Japanese Geotechnical Society Special Publication The 15th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering

Environmental impact of ground deformation caused by underground construction in

Gang Zheng i) and Yu Diao ii)

i) Professor, School of Civil Engineering, University, 92 Weijin Road, Tianjin, China. ii) Lecturer, School of Civil Engineering, Tianjin University, 92 Weijin Road, Tianjin, China.

ABSTRACT

This paper is a review of the study of ground deformation caused by underground construction and the countermeasures to control the environmental impact of underground construction, mainly including deep excavation and tunneling, based on case histories and state-of-art researches in China during the recent decade. According to the mechanism of deformation due to underground construction and its environmental impact, the deformation features and controlling measures were categorized into three classes, i.e., the soil displacement due to stress field change in soil or volume loss caused by construction activities, the ground loss caused by water-soil loss, and large scale ground movement due to the global failure of braced deep excavation or tunnel triggered by local damage of structures or local failure of soil. Furthermore, for each deformation type, the environmental impacts were graded based on the influence magnitude of the excavation and tunneling. Finally, the principles and methods to control the effects of deep excavation and tunneling were summarized.

Keywords: impact, countermeasure, excavation, tunnel, deformation, global failure

1 INTRODUCTION interaction during construction. Changes in stress field of soil, fluid field of groundwater and structure internal With the rapid development of urbanization in force can lead to various modes of ground deformation China, more and more underground space has been hence different influences to surrounding environment. explored for public infrastructures and commercial According to the causes of environmental impact, utilization. In the long term, it is estimated that over the the deformation features and controlling measures can next two decades China will build 20,000 to 50,000 be classified into three categories as following. new skyscrapers and more than 170 cities will require (1) The soil displacement caused by stress field mass transit systems by 2025, including 4000 km metro change in soil mass construction activities or ground line. Accordingly, there will be an increasingly number loss due to shield tunneling. Due to excavation, of excavations and metro tunnels projects, 65% of tunneling and dewatering, the soil movements develops which are planned to be constructed in the in eastern during the redistribution of soil stress and pore water China and central China. In most of these areas, the soft pressure. Nowadays the focus of the excavation and ground and high-level groundwater are the primary tunneling is the deformation controlling to minimize the challenges to the control of ground deformations effect on environment, especially in urban area. induced by deep excavation and tunneling. To ensure (2) The ground loss caused by water-soil loss. The the both safety and serviceability of the facilities groundwater may leak through the poor waterproof adjacent to the massive underground structures to be joints of diaphragm wall in deep excavation and built in China, therefore, it is necessary to sum up the segments of shield tunneling. If the fine particles of soil characteristics and countermeasures to environmental pass through the joints with water, the erosion of soil impact of ground deformation based on the successful can lead to large deformation of ground and case histories and state-of-art researches in China underground structures and can consequently cause the during the recent decade. larger opening of the joints of shield tunnel segments. In essence, retained deep excavation and tunneling (3) Large scale ground movement due to global in the above mentioned area establishes a complicated failure caused by local failure. Due to the strict system of soil-water-structure interaction. The initial deformation controlling criterion, the global stability of stress field of soil and groundwater is inevitably the excavation and tunnel seems satisfied, but a global disequilibrated during the process of underground and continual failure can also be triggered by local construction. The ground deformation, as one of the failure of structures or soil. When local damage and most important parameters for the environmental failure occur in the retaining structure of excavation or impact, is the response to the soil-water-structure

http://doi.org/10.3208/jgssp.KL-2 10 the lining of tunnel, a domino effect of failure may take Shanghai soft deposits, the deformation behavior of place in an underground structure system without diaphragm walls was analyzed by Xu et al. (2008). It sufficient redundancy, which has not attracted much was found that the location of the maximum lateral wall attention in design. Some case histories show that displacement occurs within H±5m, where H is the global failure of deep excavation and shield tunneling excavation depth. For excavations supported by can extend to a range of more than 100 m long, and the concrete struts, system stiffness has little effect on the width of the zone affected by global failure can exceed normalized maximum lateral displacement. For 100 m, causing large scale ground movement, as excavations braced by steel struts, the normalized showed in Fig.1. maximum lateral displacements decrease with the increasing system stiffness. A method for predicting the maximum lateral wall displacement based on the factor of stability against basal heave was proposed. Based on a database of 35 case histories, the characteristics of ground surface settlement caused by deep excavations in Shanghai soft soils are summarized by Wang et al. (2011).The maximum ground surface settlement generally ranges from 0.1%-0.8%H, with an average value of 0.38%H, where H is the excavation depth. The maximum ground surface settlements

Fig.1. Global failure of braced deep exaction in Hangzhou, China increase with the increase of the thickness of soft soils above wall toe, but decrease with the increase of the 2 THE SOIL MOVEMENT CAUSED BY STRESS factor of safety against basal heave. FIELD CHANGE DUE TO CONSTRUCTION Zheng and Li (2012) and Zheng et al. (2014) found ACTIVITIES that the deformation mode of retaining structures has a significant influence on the surrounding structures. It is According to the magnitude of deformation and found that given the same maximum horizontal impact to the adjacent facilities, the soil movements deflection of retaining structure with four deformation because of underground ground construction can be modes including convex, cantilever, composite and categorized as follows. kick-in mode, the displacement fields of soils outside (1) Small deformation. The effect of ground the excavation were considerably different. In practice, deformation on ordinary neighborhood buildings, road besides controlling the maximum horizontal and buried utilities is very slight. But for the existing displacements of the retaining structures, the facilities such us metro tunnel and station, special deformation mode of the retaining structures should be factories, hospitals, only very small deformation (e.g., optimized according to the surrounding environment. less 10 mm), is allowed to occur. However, Zheng and Li (2012) studied the response of conventional construction method and deformation buildings with different angle to excavations (Fig.2). It control techniques can not satisfy the strict deformation is found that the settlement of this kind of building was requirement. Therefore, additional countermeasures smaller than that of building perpendicular to must be adopted. excavations because a part of deformation energy was (2) Normal deformation. The deformation of this torsion energy for the building non-perpendicular to category is within the normal range of magnitude and excavations. When this kind of building is located over adjacent structures can remain within the serviceability the lowest point or the hogging zone of the settlement limit. To ensure that, only the conventional trough, the torsion deformation of the building is the underground construction techniques and deformation most obvious. control methods are necessary. (3) Large deformation. The deformation of this category is beyond the normal range of magnitude and adjacent structures exceeds the serviceability limit due to the large displacement of ground caused by deep excavation or tunneling. Cracks and tilt can happen to the surrounding structures, leakage and breakage occur to underground utilities. However, the stability of the overall stability of deep excavation and tunneling can be maintained. 2.1 Effect of excavation 2.1.1 Ground and building deformation

Based on 93 case histories of deep excavations in Fig. 2. Torsion of building non-perpendicular to exactions

11 2.1.2 Tunnel deformation settlement. The result was verified by in-situ monitored The numerical method has been widely conducted ground surface settlements in construction of two to study the effect of excavation on existing tunnel in cross-river tunnels in Hangzhou, China. proximity. Li and Wang (2012) simulated a A simple estimation method of prediction of surface construction of deep excavation adjacent to a subway soil under the horizontal displacement caused by shield tunnel in the typical soft soil at Shanghai. According to tunnel construction was proposed by Wang (2009). The the numerical study on the case history and data Mair’s equation was combined to predict the obtained from the situ monitoring, the results showed underground soil subsidence displacement caused by that the proposal of down-up method with zoned and shield tunnel construction. staged construction with a temporary diaphragm wall Jiang et al. (2014) studied two-phase horizontal inside the excavation was successful in controlling the displacements of strata during tunnel excavation, and deformation of the tunnel outside the excavation. combining with the numerical simulation. The results Based on the field measurements of a project in show that there is different variation of displacement Tianjin and a large number of FEM simulations which parallels to the tunnel direction and displacement considering the small strain of soil, Zheng et al. (2014) which perpendicular to the tunnel direction at different conducted parametric studies on the deformation stages of tunnel construction. characteristics of existing tunnels in various locations 2.2.2 Effect on buildings and the influenced zone of displacement caused by four Ding et al. (2011) and Peng et al. (2012) proposed deflection modes of retaining structure, including the distribution of the building foundation settlements convex, cantilever, composite and kick-in mode. Fig. 3 and the structure deformations and stresses due to illustrates the deformation of tunnels in different tunneling under different conditions. They indicate that characteristic zones caused by convex deformation of with the decrease of crossing angle, the settlement of retaining structure. The results showed that the range foundation rises; and the surface settlement of and characteristics zone were almost the same for the foundation changes from symmetrical distribution to convex and composite deformation of retaining lateral tilt; and the differential settlement of adjacent structure. The cantilever deformation of retaining plinth increases obviously. Tilt displacements and structure has less influence on the vertical deformation distortion of building increase significantly under of tunnel, leading to the shrink of sagging zone. The different crossing types; and it could rise 10 times at sagging zone became larger and transition zone and most. hogging zone were considerably compressed when the A calculated case which adopts the small-strain retaining structure exhibits kick-in deformation mode. constitutive model are compared with the field data, while the construction of Line 2 tunneled through a masonry building with a certain crossing Settlement angle, to analyze the influence on the ground surface Zone

(m) and the surface masonry buildings induced by tunneling

Depth (Jiang et al. 2014). The further analysis shows that both Convex Transition the maximum settlement and the width of traverse mode Zone settlement trough by using small-strain model achieved better agreement with the measurements. During the Horizontal displacement of Heave retaining structure (mm) tunnel construction, the masonry building tilts to the Zone axis of the tunnel. The rate of inclination obtained by Fig. 3. Deformation of tunnels in different characteristic zones the small-strain model can also consistent with the field caused by convex deformation of retaining structure data. Sun et al. (2012) reported a case history of an earth 2.2 Effect of tunneling pressure balance shield tunneling constructed in a close 2.2.1 Effect on ground surface distance near constructed underground structures in soft Zheng et al. (2015) reported a field test on a deposit of Shanghai. Throughout the shield tunneling greenfield area located within Rings 75-124 of the construction, various countermeasures such as grouting Jiantian Section Project. The cover depth of the tunnel and timely adjusting correction jacks were adopted was 18.2 m, and the ground water regime was based on field observation feedback to minimize hydrostatic with a water table at a depth of 1.8 m. A adverse environmental influences. The maximum method based on fuzzy statistics was proposed to cumulative lateral displacement of the diaphragm wall analyze the ground deformation during the normal is about 11 mm. tunneling process. 2.2.3 Effect on piles Lin et al. (2013) reported that an increase in the Liu et al. (2012) investigated the disturbance to piles shield advance speed and a decrease in the machine halt and pile groups caused by multiple nearby drives of a duration contributed to better control of ground

12 large diameter slurry shield-driven tunneling machine both vertical and horizontal alignment. The test results in Shanghai. The minimum distance between the tunnel showed that, for parallel tunnels, the influence of the with a diameter of 15.43m and the distance to the succeeding tunnel mainly occurred on the hance of the adjacent pile groups was only 1 m. A field investigation preceding tunnel, while for overlapped tunnels, the was conducted before the multiple crossings to study construction of new tunnel primarily caused an the impact on the piles caused by the tunneling process. upheaval of the existing tunnel in front of the cutter It is found that in the north bound tunnel advancement, face and a settlement behind the face. the two piles groups settled at the beginning of the Under conditions of normal gravity, model tests are tunnel shield advance. However, the two pile groups convenient to perform and cost little. However, the started to heave with the shield passage. applicability can be substantially reduced when Xu et al. (2015) reported Shanghai Metro Line 10, compared with centrifuge tests if the stress levels acting the interval tunnel from Liyang Road station to Quyang in the soil of the model tests are neglected in reference Road station. The tunnel had to cross through the pile to those of the prototype. Huang et al. (2012) used a group of Shajinggang Bridge. A series of numerical fluid filled rubber bags rubber bag to support the tunnel simulation were carried out on the entire construction cavities and removed a known amount of fluid from the process to explore the load transfer mechanism of bags to simulate the ground loss induced by the tunnel bridge structure. The calculation results show that both construction. In this way, the effects that the new shield the bridge static loads and traffic live loads were tunneling had on the existing tunnel were studied in the successfully transferred from pile foundation to raft centrifugal tests. after pile underpinning, and the removal of obstructed Many researchers have attempted to reconcile the piles during tunneling had a slight effect on the bridge. field performance with numerical predictions (e.g. (Fang and He 2007; Jiang et al. 2007; Tao et al. 2009) 2.2.4 Effect on existing tunneling as numerical approaches are considered as effective The development of transportation in large cities methods to reproduce full-scale field performance. Tao often requires the construction of multiple shield et al. (2009) reported a twin tunnel project, in which tunnels running in close proximity. It is important and cross steel support was adopted inside the existing necessary to conduct research on the response of the tunnel. The numerical results showed that the preceding tunnel induced by a new shield tunnel to effectiveness of the cross steel support was remarkable ensure safety. and especially the transverse steel support made a great Liao and Yang (2012) and Li et al. (2014) reported a contribution to the improvement of the existing tunnel project of four-line overlapped tunnels in Shanghai stress distribution. Zheng et al. (2015) reported a metro construction, in which Metro Line 11 closely spaced twin EPBS tunnels in typical soft ground. below-shield and above-shield perpendicularly crossed It was found that the existing tunnel was squeezed by the existing Metro Line 4 successively. The measured the horizontal arching effect caused by the succeeding data showed that the existing tunnels upheaved tunneling even when the face pressure of the shield was significantly with the increase of the face pressure at 4 the cutter face before the arrival of below-shield and less than the earth pressure at rest (Fig. ). Zheng et al. settled dramatically after the below-shield passed (2015) also simulated the existing tunnel reinforced by beneath the existing tunnel. During the above-shield various measures, including trailer bracing, grouting, tunneling, the excavation primarily caused an uplift of artificial freezing and scaffold bracing. The computed the existing tunnels. In order to control the heave and results showed that the trailer bracing was found to be partial uplift of the existing tunnels, the method of the most effective method for controlling tunnel loading both in the new tunnel and in the existing convergence. However, artificial freezing led to the tunnel was recommended. largest reductions in tunnel deflection.

Zhang et al. (2012) conducted field tests in a twin 75 tunnel project in Beijing to investigate the stress y Reference Vector changes of the preceding tunnel segment induced by a 10mm 70 x parallel shield tunnel driving in close proximity. The z Rx<0 Rx=0 circumferential stresses measured at the springline were Rx>0 Rx>0 65 all compressive stresses, suggesting that the preceding 1D tunnel lining mainly experienced a horizontal ovalling deformation mode during the construction of the 60 succeeding tunnel. Meanwhile, the magnitudes of the Preceding Succeeding

Distance to ring 370 of LT (m) LT of 370 to ring Distance tunnel tunnel circumferential stress changes were greater than those 55 of the longitudinal stress. -20 -10 010 20 Two series of model test under 1g conditions were Distance to the model centre (m) performed by He et al. (2007; 2008) which concerns on Fig. 4. Displacement vectors and horizontal arching during the succeeding tunneling, where Rx is the ratio of changed horizontal the interaction between closely spaced tunnels with total stress to initial value.

13 2.3 Effect of dewatering in deep excavation maximum soil settlement induced by pressure-relief on confined aquifer emerges at the location between 2.3.1 Retaining structure movement ground surface and the roof of the confined aquifer, but Zheng et al. (2014) carried out an in situ dewatering this location is unknown. test (T1) on phreatic water before excavation in Based on some field pumping tests of confined Beizhan station of Tianjin Metro Line 3. It is found that aquifer in Tianjin, Zheng et al. (2014) found that the considerable inward diaphragm wall deflection soil deformation induced by pressure-relief on confined occurred during 10-days pre-excavation dewatering aquifer shows a three-stage spatial distribution. The soil before the commence of excavation, and the maximum deformation overlying confined aquifer gradually deflection nearly reached 10 mm, which is quite increases up to down, the soil deformation underlying significant considering that there is an existing building confined aquifer heaves, and the soil deformation of located only about 4 m away from the diaphragm wall. confined aquifer gradually reduces up to down. Besides, To control the dewatering-induced wall deflection, they the maximum soil deformation appears at the top of conducted another in situ dewatering test (T2), which stratum which has drawdown under arbitrary water had struts installed at the top of the diaphragm wall supply conditions, relieving time and permeability of prior to the dewatering. As shown in Fig.5, it can be the overlying and underlying aquitard. found that the deflection at wall top decrease significantly during T2 compared with that in T1 with 2.3.3 Tunnel deformation the help of the struts on the wall top. In Tianjin, China, based on numerical calculation, The staged dewatering during staged excavation and Zheng et al. (2015) and Zheng et al. (2014) studied the bracing can also lead to wall deflection. Meanwhile, the effect of dewatering in excavation on the adjacent internal force of retaining walls and supporting existing shield tunnel. The results show that when the structures will be influenced by staged dewatering. existing tunnel is located in the soil immediately Zhang et al. (2013) carried out a two-dimensional finite overlying confined aquifer, dewatering will severely element analysis on the internal force and deformation induce tunnel settlement. of excavation and supporting structure under In Shanghai, China, Liu et al. (2012) studied tunnel asymmetric water pressure on both sides of the settlements of a metro line from 1999 to 2007. Several retaining wall. The results show that the supporting possible causes, especially secondary compressions of structures under asymmetric water pressure has some clay and sand layers due to groundwater pumping, are offset deformation toward the lower water pressure side, investigated based on laboratory test and field and the deformation at the higher water pressure side monitoring results. Noticeable secondary compression increases simultaneously, but the asymmetric water of Aquifer IV was found in some areas in Shanghai. pressure has little effect on the internal force The compression of Aquifer IV, especially the distribution of the supporting structures. secondary compression due to groundwater pumping is one of the principal reasons for long-term tunnel Wall deflection (mm) settlement. Controlling groundwater pumping in Aquifer IV is vital to minimize large tunnel settlement in Shanghai. 2.3.4 Pile deformation Li and Wang (2011) studied the effect of dewatering End of T2 and excavation on the pile within excavation. The End of T1 results show that during dewatering the bottom rebound

Depth (m) is reduced effectively and the axial compressive stress of piles increases. The consolidation settlement of soil because of dewatering makes negative skin friction occurred on the soil-pile interface, and with the Fig. 5. Observed wall deflections of T1 and T2 dewatering depth increased, the value of negative skin friction becomes larger. 2.3.2 Subsurface settlement In excavation, when waterproof walls do not cut off The theoretical solutions usually suppose that the the aquifer to be pumped during subsequent excavation, permeability coefficient of soil overlying confined dewatering may cause soil settlement around aquifer is very small. Hence, the roof of the confined excavation, which would exert negative skin friction on aquifer is supposed to be impermeable (Gong and nearby piles and cause additional pile settlements. Zhang 2011; Wang et al. 2013). However, in fact, the For dewatering-induced single pile settlement, Chen soil overlying confined aquifer is essentially the and Xiang (2006) presented a procedure to estimate the aquitard in most place. Therefore, the soil deformation drawdown, the soil consolidation settlement, the is more complex in practice. Some field studies (Luan negative friction on the pile shaft and the additional pile et al. 2010; Wang et al. 2009) showed that the settlement, induced by dewatering in phreatic zones.

14 They used a method with four steps including a Piles are widely used in China to protect the pumping model, a simplified consolidation evaluation, building adjacent to excavation. Fei (2010) reported a a pile-soil interaction model and a semi-theoretical pile case history using isolation piles to reduce the settlement prediction, excavation-induced deformation of several old Based on the researches of Chen and Xiang (2006), buildings with shallow foundation. Wang et al. (2010) Xiang et al. (2012) proposed a simplified procedure to adopted I-steel piles and soil nails to ensure the safety estimate pile foundation settlement induced by of the buildings 0.3m to a 6m-deep excavation. The multi-well dewatering in phreatic zone. Further, Xiang deformation and the stability of the nearby buildings et al. analyzed a practical dewatering case in Beijing were successfully ensured. The retaining effectiveness using their proposed method. It is found that the indicates that the leading I-steel piles are feasible to dewatering induced pile foundation settlement could protect near the buildings. Li et al. (2014) used exceed the settlement of the surrounding soil as a result double-row contiguous piles to protect high buildings of the combined effect of the negative skin friction on adjacent to an excavation in Beijing. Through the the portion of pile shafts that is above the depressed numerical simulation and in-situ monitoring, it is phreatic surface and the consolidation settlement of the proved that the double-row piles can reduce the soil below the pile tips. displacement field obviously. The horizontal displacement of soils can be reduced from 17 mm to 8 2.4 Countermeasures mm. The maximum differential settlement of high To ensure the serviceability and safety of structures buildings is 6.9 mm and the angle variance is 0.33‰. adjacent to the underground construction, controlling The isolation piles are also used to reduce the criterion in every single phase of the construction deformation of the tunnels in proximity to excavation should be established to divide the final controlling (Gao et al. 2010; Hu et al. 2003). Zheng et al. (2015) limit into definite objectives in each construction conducted a research on the efficiency of isolation piles activity. The principles and methods of controlling the in controlling the deformation of existing tunnels environmental impact caused by underground adjacent to deep excavations. The study was conducted construction may me concluded as following. based on a deep excavation project in Tianjin, which (1) Controlling disturbing source. Methods such as adopted the isolation piles to protect the adjacent tunnel excavation and dewatering by subzone, recharging, and carried out a series of field measurements on the compensation grouting of tunneling, can reduce the deformations of the diaphragm wall, soil outside the disturbance induced by excavation, dewatering and excavation, isolation piles and the tunnel. As shown in tunneling. Fig.6, the results obtained from the parametric study (2) Reinforcing the structure disturbed by the showed that isolation piles had isolating effect as well construction. The structures affected by the as dragging effect on the tunnel adjacent to the deep construction can be protected by temporary or excavation. The deformation of tunnel adjacent to the permanent reinforcement, such as steel frame and deep excavation can be increased when the dragging CFRP, etc. effect was more remarkable. Zheng et al. (2015) (3) Isolating the disturbing path. Grouting and piles suggested that the upper part of pile in the zone with are often used in between the protected structures and large displacement could be cancelled in design and excavations or tunneling to hinder the propagation of call this kind pile as buried isolation pile. The buried the construction-induced disturbance on the structure. isolation pile could be used to reduce dragging effect 2.4.1 Countermeasures to excavation effect and consequently to minimize the horizontal The soft soil in passive zone of excavation was displacement of tunnel. However, conventional usually improved in China to reduce the environmental isolation pile other than buried isolation pile is still impact of excavation. (Kuang 2000; Shao and Wang being misused in practice as countermeasure to reduce 2011; Yuan et al. 2012). These measurements, such as the deformation of tunnel. deep mixing reinforcement, have been proved to be effective. Li et al. (2012) studied the displacement Dragging effect controlling effect of the passive zone improvement. The Zone with large results show that there is an optimal depth for the displacement passive zone improvement. When the improvement depth is greater than the optimal depth, the maximum of diaphragm wall deflection and ground surface Isolation pile settlement were nearly unchanged. However, the increase of the improvement depth can reduce the horizontal displacement of the top of the retaining wall, Isolating effect which has great significance for the protection of the Fig. 6. Isolating and dragging effect of isolation pile on the surrounding environment. tunnel adjacent to excavation.

15 The servo system has been developed and adopted grouting area to reach an assigned volume strain, while in the bracing system to actively control the Sun et al. (2010) applied expanding pressure to the deformation of the retaining structures and reduce the grouting elements to simulate the heaving effect. Hou et environmental impact of deep exaction (Gu 2011; Jia et al. (2011) predicted the grouting uplift during tunnel al. 2009). Jia et al. (2009) reported the first case of construction undercrossing experimental buildings history in China using strut force servo system to #104 and #105 by numerical simulation. The results protect an adjacent metro tunnel 5.4m from an indicate that the maximum uplift is 2.1-3.7 mm. It is excavation in Shanghai soft clay. The lateral also shown that uplift force and stiffness of exterior displacement and settlement of the tunnel was isolation curtain can influence the uplift effect successfully reduced to 4mm and 2mm, respectively. significantly. 2.4.3 Countermeasures to dewatering effect 2.4.2 Compensation grouting Many researches have pointed out that （1）Vertical cutoff barrier compensation grouting is an effective measure to In China, to control the dewatering-induced soil and protect the adjacent buildings and structures. The structure deformation around excavation, vertical cutoff methods of the researches about compensation grouting walls (or waterproof wall) are usually used around can be categorized into four aspects which are the excavation. In the case of thick confined aquifer (e.g., analytical methods (Zhang et al. 2012), the test Shanghai), it is difficult to cut off the aquifer methods(Li et al. ; Yi et al. 2009; Zhang et al. 2013), completely. Therefore, Zhou et al. (2010) carried out a the numerical methods (Chen et al. 2014; Hou et al. series of simulations of excavation dewatering to 2011; Zhang et al. 2012) and case histories (Peng optimize the waterproof length to minimize the 2011). surrounding soil settlement. The optimal length of Due to the mixed geological compositions of the diaphragm wall was found to be 32m for a 15.6-17.6m soil and the complexity of the ground movement which excavation in Shanghai and the maximum settlement of is controlled by a large number of uncertain factors, surrounding soil was 7.97mm. finding closed form analytic solutions becomes an impossible task by the classical elastic-plastic analysis. （2）Vertical-horizontal cutoff barrier Zhang et al. (2012) considered the ground heave This method was not commonly used in the past induced by stratum expansion as a stochastic process years in China. However, Xing et al. (2011) recently and the stochastic medium theory was applied to reported a case study in Shanghai adopting this method. determine the heave and deformation of ground surface. The characteristics of different ground-water treatment A simplified method is proposed and can predict the methods were analyzed, and the horizontal sealing grouting-induced ground heave profiles reasonably. technology was proposed. The location and thickness of Compensation grouting has been developed mainly the horizontal sealing layer were analyzed and their by trial and error in the field. Zhang et al. (2013) effects on excavation deformation were studied through introduced a tunnel project with 79 buildings overlying theoretical analysis and three-dimensional finite the tunnel and conducted compensation grouting tests element simulation. The optimization of the horizontal to obtain the suitable grouting parameters. The entire sealing measure was carried out. The feasibility was deformation process of the monitored building during proved by means of the monitoring results during tunneling, including four consecutive stages, was excavation. elaborated. The structures were effectively uplifted by （3）Artificial recharge the compensation grouting. Besides, some laboratory Recently in China, as a method to control the tests were performed to research the fundamental dewatering-induced soil and structure deformation behavior of compensation grouting considering of the around excavation, artificial recharge on confined repeatability. Peng (2011) reported a case history of aquifer receives much attention. Qu et al. (2011) compensation grouting. The Building 34 is a key reported a case study of artificial recharge in Shanghai. protection object during tunneling. The settlement and To protect the existing Metro Lines, groundwater crack development were monitored to avoid excessive recharge was utilized around excavation. Via recharge, deformation and guide the construction in real time. the soil settlement induced by excavation and Monitoring results show that，the total subsidence value dewatering was restricted, and the settlement rate of each monitoring point was controlled within 25mm； decreased obviously. Wang et al. (2012) conducted a the differential settlement of the building is controlled multi-cycle recharge–recovery field experiment to within 1‰. investigate the response of a shallow, confined aquifer There are mainly two kinds of methods for the to artificial recharge through a well. The results showed numerical simulation of compensation grouting, i.e., the that the efficiency of a multi-cycle recharge was higher volume control and the pressure control. Zhang et al. than that of a single-cycle recharge under the same (2012) imposed radial velocity on outer mesh nodes of recharge volume and time (i.e., with the recharge

16 frequency increased, the water level rises more groundwater level and cause the heave of ground. Then distinctly). Zheng et al. (2013) reported the first the double-recharging-well method was assessed by successful case of recharge of confined water in an recharging and backflushing simultaneously. It can be excavation in Tianjin, China based on settlement seen that there was slight incremental deformations of control, as shown in Fig.7. The measured settlement of S1 and S2. Therefore, the results indicate that the the buildings during excavation further shows that the backflushing-induced settlement was eliminated using variation of the settlement of the protected buildings double-recharging-well method. After the end of almost simultaneously and directly relates to the recharging and backflushing test, the groundwater level fluctuation of the head of confined aquifer (Fig.8). dropped and settlement of the surrounding soil occurred. 0 510 Scale： （）m A11 H11 H1 JZ1 Excavation Excavation JZ4 基坑 Building 基坑 Building A12 被保护建筑 被保护建筑 JZ2 JZ5 A3 Protected building JZ3 JZ6 Excavation JZ10 A4 JZ13 JZ8 JZ11 Auxiliary recharge well H3 辅助回灌井 JZ9 Recharge回灌井 well Primary recharge well H4 JZ12 主回灌井 H7 JZ14 (a) (b) Building settlement（） JZ Fig. 9. Arrangement of recharge well: (a) Conventional method; Recharge well（） H (b) Double-recharging-well method Observation well of confined aquifer（） A Fig. 7. Plan view of excavation and protected building. RCW recharging BFW backflushing 4.0 4.0 ①：HeavingH1 recharge Steady Settling 3.5 3.5 ②：StageH1 recharge Stage D8 H1 C1Stage (mm) 3.0 C1 backflush D20 3.0 (mm) ③： Water-level 2.5 recovery 2.5 2.0 2.0 1.5 D20 1.5 deformation D8 1.0 1.0 H

Ground 0.5 0.5 settlement Ground 0.0 0.0 Fig. 8. Isolating and dragging effect of isolation pile on the 123456 tunnel adjacent to excavation. SequenceMonitoring Number of times Observation In order to ensure the success of the long-term Fig. 10. Development of ground deformation in the test of double recharging well method recharge of groundwater, periodic backflushing of recharge well is necessary. Zheng and Zeng (2014) 3 THE GROUND LOSS CAUSED BY found the backflushing of recharge well can lead to WATER-SOIL LEAKAGE ground settlement around recharge well and additional settlement of building close to recharge well. Hence, Based on the amount of soil and groundwater loss, for each primary recharge well, they added auxiliary the effects of groundwater leakage are graded as recharge wells aside the primary recharge wells, as following. shown in Fig. 9. This is termed as double-recharging- (1) Groundwater leakage. Only the groundwater well method. The auxiliary recharge well recharge leaks from the joints of the underground structure, and during the backflushing of the primary recharge well, no soil particles are taken out by the ground water. preventing the groundwater drawdown and the Ground settlement is induced by the consolidation of consequent settlement around recharge well. ground due to the groundwater leakage. Further, Zheng and Zeng (2014) conducted an in (2) Convergent water-soil loss. The soil initially situ recharge test to evaluate the double-recharing-well passes through the joints with water and local erosion method. As shown in Fig. 10, there was a recharging of ground may develop. For this category, the soil loss well (RCW) and a backflushing well (BFW) in the test stops finally due to soil arching effect and local stable and the settlement of surrounding soil was monitored at cavity forms near the leakage location. S1 and S2. Recharge was performed first to raise the (3) Continual water-soil loss. The water together

17 with soil comes out of ground ceaselessly. Large method must be guaranteed. deformation and failure can take place in the structures Research of leakage of excavation on ground and surrounding ground. Collapse of structure and deformation in China is mainly focus on accident sinkhole of ground may occur. introduction and conclusions of engineering experience. The mechanism of disaster has not been fully known. 3.1 Soil-water loss of excavation The researches mainly focus on the disaster during The risk and difficulties in deep excavation shied machine launches from or approach the engineering increase significantly due to the more and foundation pit. Wei et al. (2010) established the finite more complicated condition both in geology and element model to research the settlement of the underground environment. Numerous accidents in deep undisturbed soil in front of the reinforced soil during excavation due to leakage have occurred in China. leakage. Besides, Wei et al. (2011) established a However, field measures due to these accidents are theoretical model to research the influence of range of rather rare. Firstly, the occurrence of disaster is reinforced soil, groundwater level and the gap of wall unexpected, so it is hard to ensure the measurement is on the ground settlement due to leakage. Case studies being conducted when and exactly where the disaster is show that soil loss is a significant factor to induce happening. Secondly, disaster is destructive, so ground movement. Though the research in tunnel conventional measurements may be incapable of disaster can provide a reference on disaster in capturing any field data during large deformation stage. excavation, it is necessary to conduct research focus on Thirdly, once the accident occurs, some disaster in excavation caused by soil and water loss. countermeasures must be taken (such as injection), Only when the mechanism of disaster is revealed which makes the measurement results too complicated essentially, can the occurrence of disaster in excavation to reflect the exact influence of the disaster. can be decreased fundamentally. Xu et al. (2013) reported the monitoring of historic buildings due to the two leakage accidents of Tianjin 3.2 Soil-water loss of tunnel Metro Line 3 in China. Water with soil started to flow Accident due to seal failure of shield machine into the excavation. After that, the historic buildings occurred in Nanjing Metro Line 1was reported by Li started to settle immediately. The historical buildings and Fang (2006). The differential settlement of an suffered serious degree of damage. adjacent building was up to 42 mm, and lots of cracks When a shield machine launches from or appeared on the wall of the building. After the grouting, approaches to the excavation of station, diaphragm wall the settlement was controlled. breaking process is inevitable and contains a high risk. Leakage and lining failure are also two of main Lots of accident has happened during the diaphragm disasters for the metro tunnels in use. Ye et al. (2007) wall breaking process, such as Automated People reported the tunnel settlement of Shanghai Metro Line Mover System (APMS) accident in Guangzhou (Zhu 1 during 15 years of monitoring (Fig. 11). Leakage is a and Ju 2009). main factor for the differential settlement of the tunnel. The reasons for these accidents are complicated. Jet Therefore, full-life maintenance and monitoring must grouting generally was conducted outside the deep be done even though the tunnel has been put into excavation before diagram wall breaking, and the service, and measures must be taken to stop the leakage cleavage may exist between cemented soil and the of tunnel. Tunnel mileage (m) diagram wall. Water and sand can flow in the pit from 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000 14,000 the cleavage. Besides, the quality of freezing method to 0 Shanxi Road Staion reinforce the soil outside the diagram wall is difficult to -50 Xujiahui -100 Wantiguan Hanzhong Road guarantee. Station Station Changshu Road Station -150 Station In conclusion, lessons can be learned from these From year of 1995 to 2009 Guangpo Road accidents. Soil and water crushing accident usually (mm) Settlement -200 Station Hengshan Road -250 occur due to the low quality of waterproofing structure Station Railway Station or the breaking process. -300 (a) Renmin Square Station (1) During the construction of diagram wall, any Tunnel mileage (m) suggested construction procedure must be obeyed. 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000 14,000 0 (2) During the deep excavation, measures must be Shanxi Road Staion taken immediately when leakages occur at or directly -50 Xujiahui -100 Wantiguan Hanzhong Road adjacent to panel joints, especially in the zones outside Station Station Changshu Road Station -150 Station reinforcement cages. From year of 1995 to 2009 Guangpo Road

(3) Water-rich sand stratum has the characteristic of Settlement (mm) -200 Station high risk and must be paid significant attention. Hengshan Road -250 Railway Station (4) Diaphragm wall breaking process disturbs the Station -300 (b) (b) soil outside the excavation significantly. Therefore, Renmin Square Station high quality soil reinforcement and soil freezing Fig. 11. Tunnel settlement of Shanghai Metro Line 1 during 15 years (a) Up line (b) Down line

18 For tunnel leakage, lots of researchers in China have However, different countermeasures according to carried on the exploration in many aspects. specific engineering condition need to be built Homogenous Infiltration Body Method (HIBM) was systematically. conducted by Zheng et al. (2005). HIBM regards lining From the aspect of disaster occurrence and as permeable. Permeability coefficient of lining reflects evolution mechanism, recommended countermeasures the overall damaged condition of lining. Zhang et al. are as follows: (2006) introduced constitutive model of soil which can (1) The size of opening needs to be controlled. consider time-dependent stress-strain behavior into For tunnel leakage, the joint opening can be decreased HIBM to research the leakage of tunnel. After that, Wu to prevent the loss of soil. Besides, polyurethane can be et al. (2009) built three-dimension model to research used to stop these leakages point. the ground settlement induced by tunnel leakage. (2) Loosening zone and the soil that have the These years, numerical simulation is developed by probability to be washed away need to be reinforced by refining the joint structure and leakage location. Liu et grouting. It is noted that the setting time of grout must al. (2013) analyzed the ground and tunnel settlement be fast enough. The injection of slow setting time grout considering different joint leakage location in the may aggravate the disaster. Two liquid grout injection context of the same magnitude of water inflow. Zheng system which injects a grout mixed with cement and et al. (2014) considered eight different leakage sodium silicate is recommended. positions and researched the influence of leakage on (3) Groundwater supply can be cut off to stop the parallel tunnel and surrounding soils. flooding. The key point for this method is that the Settlement induced by the leakage is due to the dewatering speed needs to be fast enough. consolidation of soil. However, in the disaster caused (4) If all the method mentioned above is in vain, by soil and water loss, the settlement is mainly the water pouring into the underground structure is the last result of soil loss resulting in loosening and reduction choice to control the deterioration of the disaster. of resistance of ground. Numerical simulation of soil From the aspect of engineering management, and water loss is still a challenge to the researchers. recommended countermeasures are as follows: PFC-CFD method has been conducted by researchers in (1) Water-rich sand stratum is very dangerous. China to simulate the problem of soil and water loss. Special attention must be paid to this kind of stratum. Wu et al. (2014) simulated the slop erosion process (2) The quality of diaphragm wall body and with PFC-CFD method and compared the simulation to joints or waterproof curtain must be guaranteed. Tilt of the experiments, proving the applicable of this method grouting rods may induce the disaster of water and soil in simulating fluid-soil coupling problem. Jiang and loss in underground engineering. Any bentonite Zhang (2014) implemented Tait equation of state for inclusion, rapped air pocket or slurry pocket in liquid into the N-S equations to establish PFC-CFD diaphragm wall may become the opening that water and codes to make the PFC-CFD suitable in reflecting soil soil flow through. consolidation. Zheng et al. (2014) simulated the leaking (3) The seal of the shield machine need be process of sand and water using PFC-CFD method and checked frequently during tunneling, especially the tail validated the simulation results to the experiment seal. results. (4) On-time and regular monitoring and Many experimental devices have been developed by information feedback must be executed strictly. Chinese researchers to explore the mechanism of (5) During excavation or tunneling, disaster. The ground movement pattern during disaster countermeasures must be taken immediately when is researched. Research directions of these experimental leakage occurs, even if the flow rate is small. devices can be classified into four main categories: (6) During tunneling, the process of shield catastrophic behavior of working face (Zhang et al. machine launches from or approaches the foundation 2014), water inrush of undersea tunnel (Li et al. 2014), pit involve high degree of risk. The combination of tunnel collapse mechanism (Zhang et al. 2014) and soil ground freezing method and grouting injection and water loss mechanism (Zheng et al. 2014). Model reinforcement is recommended. tests can reflect the failure mechanism of tunnel disaster. However, large-scale tests which more accords 4 GLOBLAL FAILURE CAUSED BY LOCAL with the actual disaster condition still need to be FAILURE conducted. The following aspects of the global failure caused 3.3 Countermeasures by local failure are involved. Countermeasures to reduce the impact of ground (1) Local failure and instability of excavation and deformation induced by soil and water loss disaster tunnel. The local failures causing overall instability have been proposed by many researchers according the should be identified. The importance of the local failure “accident experience” (Dong 2013; Fu and Yi 2014; at different positions should be quantified. Gao and Liu 2013; Li et al. 2009; Zhang et al. 2010) (2) Trigger and transform of different local failures.

19 For excavation and tunnel, the type and location of the collapse could provide reference and basis for its local failure are various. The initial local failure may control. trigger another local failure. The relationship between Due to the importance of the deep excavation safety, local failures plays a vital role in the progressive the concept of redundancy should be introduced into failure. the design of deep excavation to increase the ability of (3) Propagation and termination mechanism of retaining structure to prevent progressive collapse. The global failure. The prevention methods can be purpose of redundancy design is that through employed to hinder the failure propagation and reasonable optimized configuration of strut system and accelerate the failure termination so that the redundancy essential construction measures of connections, on the of the system is increased. premise that the cost of the project does not increase or only increase slightly, multiply the load transfer paths 4.1 Global failure of excavation to prevent extremely large deformation or progressive In recent years, serval of excavations in China collapse of the retaining system caused by the local collapsed and caused very severe consequences, such as failure or weakness. Based on practical experiences and in Hangzhou (Gong and Zhang 2012), Beijing(Yao et al. theoretical research, the redundancy problems can be 2008), Shanghai(Sun 2012), Guangzhou, Nanning(Zhu divided into following categories ( Zheng et al. 2011). et al. 2010), etc., as shown in Fig 12. (1) Deformation redundancy of horizontal bracing system. (2) Stability redundancy of horizontal bracing system, including both single-level and multi-level horizontal bracing, and redundancy of connection joints of the vertical and horizontal retaining structure. (3) Deformation redundancy of vertical retaining system.

(4) Redundancy of the vertical supporting structures. The progressive failure of excavation has been not attracted much attraction and there is few related research. For the longitudinal progressive failure, Cheng et al. (2015) and Cheng et al. (2015) conducted both numerical simulation and model tests of partial Fig. 12. Plates of excavation collapses in China collapse induced by the breakage of some retaining piles. It is indicated that partial collapse has significant Based on those cases, it can be found that the influence on adjacent retaining structures, and can collapse process of an excavation is complicated, cause the sudden increasing of adjacent earth pressure especially when the excavation was deep, large, and and structure internal forces. They proposed a load retained by complex structures. The collapse may transfer coefficient, which equal to the increment ratios initiated from a kind of partial failure (Zheng et al. of the internal forces of the piles adjacent to the partial 2014; Zheng et al. 2011), such as partial failure of the failure, to describe the load transfer process during the retaining structure or partial instability of the soil, and progressive failure. The load transfer coefficient of a continuously evolve into many kinds of failure modes, pile decrease as the distance between the pile and the until widespread collapse occurred in the surrounding partial collapse becomes larger, as shown in Fig.13. retaining structures. The collapse of deep excavation is There were two model tests of excavation retained by a global and progressive collapse process. Zheng et al. cantilever piles. The excavation depths were 60 cm and (2011) divided the progressive collapse problems of 75 cm, corresponding to two embedded depth of pile, deep excavation into 3 main categories, i.e. progressive 60 cm and 45 cm, respectively. collapse in the cross section of the excavation, progressive collapse in the longitudinal direction of 1.45 excavation and progressive collapse of horizontal strut 1.4 75cm 60cm 1.35 system. Progressive collapse can cause massive 1.3 destruction of the excavation. Nevertheless, the 1.25 collapse cannot carry on infinitely, and will stop when 1.2 1.15 it extends to certain scope, such as the accidents in 1.1 Hangzhou (Gong and Zhang 2012; Li and Li 2010; 1.05

Zhang and Li 2010). Thus it can be seen that coefficients Load transfer 1 progressive collapse of excavation has natural 0 5 10 15 20 25 30 Pile number termination phenomenon in the longitudinal direction. Fig. 13. Load transfer coefficients of model tests with different Moreover, the termination mechanism of progressive excavation depth

20 Traditional design theory of horizontal supporting For the ground collapse induced by urban tunneling, structure of excavation is based on element design, and Zhang et al. (2010) studied the catastrophe mechanism cannot guarantee sufficient redundancy of the entire and control technology of ground collapse induced by supporting systems. Zheng et al. (2014) simulated the urban tunneling combined with ground collapse ring beam supporting structure as representative accident cases. Hou et al. (2009) analyzed the main example of horizontal strut systems. They proposed a reasons for safety accidents and proposed the relevant new redundancy evaluation index, i.e. Comprehensive control measures based on this situation and especially Redundancy Factor was proposed. The research results on the specific accident cases of Beijing new subway show that the quantity of load paths is an important projects. factor that can influence redundancy of retaining 4.3 Countermeasures structure massively, and progressive collapse Through the analysis and case studies, (Zheng et al. simulation and redundancy analysis are helpful for (2011)) proposed the following measures that are determination of key elements. significant and effective for improving the redundancy 4.2 Global failure of tunnel of the retaining system. At present, research on tunnel disasters is mainly (1) Develop more effective alternate load paths focused on the stability of the tunnel excavation surface through reasonable arrangement and design of and ground collapse induced by urban tunneling based elements. on theoretical analysis, numerical analysis, and model (2) Increase the connection resistance to improve tests. However, there are also several progressive the integrity and robustness of system. damage even collapse accidents had happened during (3) Ensure that the connections and elements have the tunneling for metro in China, such as in Shanghai sufficient ductility. (Fang et al. 2009) and Nanjing (Yang 2011). (4) Reinforce the support structure at certain interval The shield tunnel is composed of reinforced through diagonal struts or other construction measures concrete segments, and the joint part is the weak to improve the system robustness. position. The tunnel may easily encounter domino type (5) Install continuous wales to increase the continuous damage along the length direction in the continuity of retaining structure at horizontal direction case of a partial segment damage. especially when the plane form of excavation is convex. For the stability of the tunnel excavation surface， (6) Key elements have higher strength and ductility on the aspect of theoretical analysis, Xilin et al. (2011) than other elements. studied the face stability of shield tunnels based on the (7) Monitor the key elements through the whole limit equilibrium of Murayama and the upper bound process of construction. limit analysis method, and deduced the formulas for calculating the least support pressure at collapse. Wang 5 CONCLUSIONS et al. (2013) proposed a new failure mechanism under Case histories and state-of-art researches in China seepage conditions by improving the mechanism under during the recent decade were reviewed systematically. dry or drained conditions, and calculated the The following conclusions are draw. upper-bound solution of limit support pressure. On the Base on the causes of environmental impact, the aspect of numerical analysis, Zhang et al. (2011) deformation features and controlling measures were evaluated tunneling-induced ground movement by categorized into three classes, including the soil using DEM. Chen et al. (2011) investigated the failure movement caused by construction activities, the ground mechanism and the limit support pressure of a tunnel loss caused by water-soil loss, and the global failure face in dry sandy ground by using DEM, and found that caused by local damage of structures. the support pressure decreases to the limit support For the serviceability and safety of structures pressure and then increases to the residual support adjacent to the underground construction, controlling pressure with the increase of the horizontal criterion in every single phase of the construction displacement of the tunnel face. should be established to divide the final controlling On the aspect of model tests, Tang et al. (2013) limit into definite objectives in each construction conducted centrifugal model tests with different activity. overburden/diameter ratios to study the problem of The water-soil loss may cause large deformation tunnel face stability in dense sand, and a and failure of the structures and surrounding ground. “wedge-prism” failure zone occurs in front of the The principles to reduce it impact may include tunnel face after the face failure in the paper. Li controlling the size of leakage spot, stabilize the soil conducted a large-scale model test on the face stability which may be eroded, isolating the supply of the of shield tunneling in dry sand with the shield diameter groundwater, and reinforcing the affected structure. 1m by monitoring the change of the stress state in front Local damage and failure occur in the retaining of the face, and found that the collapse occurred in two structure of excavation and the lining of the tunnel may stages: local instability and global instability.

21 trigger a domino effect of failure in an underground 19) Hou, Y., Zhang, D., and Li, P. (2009). "Analysis and Control structure system without sufficient redundancy. Measures of Safety Accidents in Beijing Subway Construction." JOURNAL OF BEIJING JIAO TONG UNIVERSITY, 33(3), 52-59. FERENCES 20) Hu, Z., Yue, Z., Zhou, J., and Tham, L. (2003). "Design and 1) Chen, R., Tang, L., Ling, D., and Chen, Y. (2011). "Face construction of a deep excavation in soft soils adjacent to the stability analysis of shallow shield tunnels in dry sandy Shanghai Metro tunnels." Canadian Geotechnical Journal, ground using the discrete element method." Computers and 40(5), 933-948. Geotechnics, 38(2), 187-195. 21) Huang, D., Ma, X., Wang, J., Li, X., and Yu, L. (2012). 2) Chen, S., and Xiang, Y. (2006). "A procedure for theoretical "Centrifuge modelling of effects of shield tunnels on existing estimation of dewatering-induced pile settlement." tunnels in soft clay." Chinese Journal of Geotechnical Computers and Geotechnics, 33(4), 278-282. Engineering, 34(3), 520-527. 3) Chen, T., Zhang, L., and Zhang, D. (2014). "An FEM/VOF 22) Jia, J., Xie, X., Luo, F., and Zhai, Q. (2009). "Support axial hybrid formulation for fracture grouting modelling." force servo system in deep excavation deformation control." Computers and Geotechnics, 58, 14-27. Journal of Shanghai Jiaotong unversity, 43(10), 1590-1594. 4) Cheng, X., Zheng, G., and Huang, T. (2015). "Experimental 23) Jiang, M., and Zhang, W. (2014). "Coupled CFD-DEM study of the load transfer mechanism under the condition of method for soils incorporating equation of state for liquid." partial failure of cantilever contiguous retaining piles." Chinese Journal of Geotechnical Engineering, 36(5), 5) Ding, Z., Peng, L., and Shi, C. (2011). "Analysis of influence 793-801. of metro tunnel crossing angles on ground buildings." Rock 24) Jiang, X., Jia, Y., and Wang, T. (2007). "Numerical and Soil Mechanics, 11, 033. simulation of influence of shield tunneling on short-distance 6) Dong, Y. (2013). "Discussion of treatment measures of small parallel existing tunnel." Journal of Tianjin University, 40(7), pipe jacking construction inducing sand and water gushing" 786-790. Journal of Shijiazhuang Tiedao University (Natural Science). 25) Jiang, X., Lu, P., and Gang, Z. (2014). "Influences on the 7) Fang, J., Zhang, Z., and Zhang, J. (2009). "Application of surface structure induced by tunneling in the soft ground of artificial freezing to recovering a collapsed tunnel in Tianjin." Rock and Soil Mechanics, 35(S2), 535-542. Shanghai Metro No. 4 Line." Chin Civ Eng J, 42(8), 26) Kuang, L. (2000). "KUANG Long-chuan. Influence of 124-128. construction of deep foundation pit on tunnels of metro." 8) Fang, Y., and He, C. (2007). "Numerical analysis of effects Chinese Journal of Geotechnical Engineering, 22(3), of parallel shield tunneling on existent tunnel." Rock and 284-288. Soil Mechanics, 28(7), 1402-1406. 27) Li, D., Wang, M., Yang, G., Liu, J., and Zhang, D. (2014). 9) Fei, W. (2010). "Application of isolation piles to deformation "Monitoring of double-row piles and high buildings adjacent control of deep foundation pits close to buildings with to deep foundation pits." Chinese Journal of Geotechnical shallow foundation." Chinese Journal of Geotechnical Engineering, 36(zk2), 412-417. Engineering, 32(1), 265-270. 28) Li, G., and Li , X. (2010). "The shear strength in stability 10) Fu, K., and Yi, X. (2014). "The cause analysis and treatment analysis of subway pit in soft clay." Geotechnical ideas for sand boil disease of a railway tunnel." Journal of Investigation & Surveying, 1, 1—4. Railway Engineering Society, 31(2), 78-82. 29) Li, J., and Wang, W. (2012). "Design and Construction of 11) Gao, F., and Liu, C. (2013). "The mechanism and deep excavation engineering adjacent to the subway tunnel." comprehensive treatment of tunnel water and sand inrush Journal of Railway Engineering Society(11), 104-111. accident." Technology & Economy in Areas of 30) Li, J., and Wang, X. (2011). "Research on effect of Communications, 15(3), 26-28. dewatering and excavation on pile." Geotechnical 12) Gao, G., Gao, M., Yang, C., and Yu, Z. (2010). "Influence of Investigation & Surveying, 39(9), 5-8. deep excavation on deformation of operating metro tunnels 31) Li, L., Zhang, M., Wu, H., and Wang, Y. (2014). "Influence and countermeasures." Chinese Journal of Geotechnical of short-distance multi-line overlapped shield tunneling on Engineering, 32(3), 453-459. deformation of existing tunnels." Chinese Journal of 13) Gong, X., and Zhang, J. (2011). "Settlement of overlaying Geotechnical Engineering, 36(6), 1036-1043. soil caused by decompression of confined water." Chinese 32) Li, P., Zhang, Q., Zhang, X., Li, S., Zhang, W., Li, M., and Journal of Geotechnical Engineering, 33(1), 145-149. Wang, Q. "Analysis of fracture grouting mechanism based on 14) Gong, X., and Zhang, X. (2012). "Excavation collapse of model test." Hangzhou subway station in soft clay and numerical 33) Li, S., and Fang, L. (2006). "Analysis of EPB tunneling investigation based on orthogonal experiment method." accident in saturation fine and silt sand layer." Railway Journal of Zhejiang University SCIENCE A, 13(10), Engineering(12), 33-35. 760-767. 34) Li, S., Liu, G., and Zhang, P. (2009). "Prevention and control 15) Gu, G. (2011). "Servo system in deep excavation of Shanghai technology of gushing water of shield tail during tunneling." Jiali Centre." Machines of building, 10, 790-795. Petroleum Engineering Construction, 35(2), 79-80. 16) He, C., Su, Z., and Zeng, D. (2007). "Research on influence 35) Li, S., Wang, K., Li, l., Zhang, Q., Hu, C., Zhou, Y., Liu, H., of shield tunnel construction on deformation and secondary and Lin, P. (2014). "Development and application of an inner force of constructed." Chinese Journal of Rock extendable model test system for water inrush simulation in Mechanics and Engineering, 26(10), 2063-2069. subsea tunnel." Chinese Journal of Rock Mechanics and 17) He, C., Su, Z., and Zeng, D. (2008). "Influence of metro Engineering, 33(12). shield tunneling on existing tunnel" China Civil Engineering 36) Li, Z., Hou, W., Ye, A., Chen, K., and Tang, Y. (2012). Journal, 41(3), 91-98. "Displacement control effect of passive zone improvement at 18) Hou, Y., Zhang, D., and Chen, F. (2011). "Study of excavation section of deep foundation pits." Chinese Journal mechanism and prediction of grouting uplift in tunnel of Geotechnical Engineering,, 34(suppl), 621-627. construction undercrossing buildings." Chinese Journal of 37) Liao, S., and Yang, Y. (2012). "Deformation analysis and Rock Mechanics and Engineering, 12, 004. control of a running subway crossed by upper- and

22 lower-shield in succession." Chinese Journal of Geotechnical Engineering, 35(4), 1696–1704. Engineering, 34(5), 812-818. 55) Wang, J., Wu, L., Zhu, Y., Tang, Y., Yang, P., and Lou, R. 38) Lin, C.-g., Zhang, Z.-m., Wu, S.-m., and Yu, F. (2013). "Key (2009). "Mechanism of Dewatering-induced Ground techniques and important issues for slurry shield Subsidence in Deep Subway Station Pit and Calculation under-passing embankments: A case study of Hangzhou Method." Chinese Journal of Rock Mechanics and Qiantang River Tunnel." Tunnelling and Underground Space Engineering, 28(5), 1010-1019. Technology, 38, 306-325. 56) Wang, J., Wu, Y., Zhang, X., Liu, Y., Yang, T., and Feng, B. 39) Liu, G., Li, Q., and C.W.W.Ng (2012). "Influence of (2012). "Field experiments and numerical simulations of secondary compression due to groundwater mining on confined aquifer response to multi-cycle recharge–recovery long-term tunnel settlement." Rock and Soil Mechanics, process through a well." Journal of Hydrology, 464, 328-343. 33(12). 57) Wang, S., Lian, F., Gong, X., Sun, N., and Liu, C. (2010). 40) Liu, J., Qi, T., and Wu, Z. (2012). "Analysis of ground "Application of leading I-steel piles in retaining of movement due to metro station driven with enlarging shield foundation pits." Chinese Journal of Geotechnical tunnels under building and its parameter sensitivity analysis." Engineering, 1. Tunneling and Underground Space Technology, 28, 287-296. 58) Wang, W., Xu, Z., and Wang, J. (2011). " Statistical analysis 41) Liu, Y., Zhang, D., and Huang, H. (2013). " Influence of of characteristics of ground surface settlement caused by long-term partial drainage of shield tunnel on tunnel deep excavations in Shanghai soft soils." Chinese Journal of deformation and surface settlement." Rock and Soil Geotechnical Engineering, 33(11), 1659-1666. Mechanics, 34(1). 59) Wei, G., Guo, Z., Wei, X., and Chen, W. (2010). "Analysis of 42) Luan, C., Kan, H., and Tang, Y. (2010). "Settlement caused coupled seepage and stress of shield tunnel lauching accident by dewatering at Yishanlu Metro Station in Shanghai." in soft clay." Rock and Soil Mechanics, 31(Supp. 1), Chinese Journal of Geotechnical Engineering, 32(12), 383-387. 1961-1968. 60) Wei, X., Guo, Z., Wei, G., and Zhang, S. (2011). "Study of 43) Peng, L., Ding, Z., Huang, J., Lei, M., and Sun, H. (2012). accident mechanism of shield launching considering "Numerical analysis of deformation influence of tunnel seepage." Rock and Soil Mechanics, 32(1), 106-110. crossing types on ground building." Journal of Central South 61) Wu, H., Hu, M., Xu, Y., and Shen, S. (2009). "Law of University (Science and Technology), 1, 046. influence of segment leakage on long-term tunnel 44) Peng, Z. (2011). "Study of grouting uplifting for existing settlement." Chinese Journal of Underground Space and building traversed by tunnel and its application." Chinese Engineering, 5(A02), 1608-1611. Journal of Rock Mechanics and Engineering, S1. 62) Wu, Q., Wang, C., Song, P., Zhu, H., and Ma, D. (2014). 45) Qu, C., Chen, W., and Huang, Y. (2011). "Numerical "Rainfall erosion experiment for steep loess slope and Simulation for Subsidence of Deep Foundation Pits fluid-soil coupling simulation with PFC3D." Rock and Soil Controlled by Artificial Groundwater Recharge." Periodical Mechanics, 35(4), 977-985. of Ocean University of China, 1672, 87-92. 63) Xiang, Y., Chen, S., and Yu, C. (2012). "Estimation of 46) Shao, H., and Wang, R. (2011). "Monitoring data analysis on multi-well dewatering induced pile foundation settlement in influence of operating metro tunnel by nearly excavation phreatic zones." CIM Bulletin, 73(816), 1764-1768. construction." Chinese Journal of Underground Space and 64) Xilin, L., Wang, H., and Huang, M. (2011). "Limit Engineering, 20(S1), 1403-1408. theoretical study on face stability of shield tunnels." Chinese 47) Sun, F., Zhang, D., Wang, C., Fang, Q., and Wang, B. (2010). Journal of Geotechnical Engineering, 33(2), 57-62. "Analysis of raising pipeline by fracture grouting and its 65) Xing, H., Zhang, Z., Wu, J., Xx, C., and Ye, G. (2011). application [J]." Rock and Soil Mechanics, 31(3), 932-938. "Technology of double-confined water treatment of metro 48) Sun, H. (2012). "Research on One Pit Collapse in Shanghai." interchange station under complex soil layers." Chinese Chinese Journal of Underground Space and Engineering, Journal of Geotechnical Engineering, 33(10), 1609-1614. 10(S1), 1743-1746. 66) Xu, Q., Zhu, H., Ma, X., Ma, Z., Li, X., Tang, Z., and Zhuo, 49) Sun, Y., Xu, Y.-S., Shen, S.-L., and Sun, W.-J. (2012). "Field K. (2015). "A case history of shield tunnel crossing through performance of underground structures during shield tunnel group pile foundation of a road bridge with pile underpinning construction." Tunneling and Underground Space technologies in Shanghai." Tunneling and Underground Technology, 28, 272-277. Space Technology, 45, 20-33. 50) Tang, L., Chen, R., Yinm, X., Kong , L., Huang, B., and 67) Xu, Z., Han, Q., Zheng, G., and Zhang, L. (2013). "Field Chen, Y. (2013). "Centrifugal model tests on face stability of monitoring and analysis of effects of metro tunnels under shield tunnels in dense sand." Chinese Journal of historic buildings." Chinese Journal of Geotechnical Geotechnical Engineering, 35, 1830–1838. Engineering, 35(2), 364-374. 51) Tao, L., Sun, B., and Li, X. (2009). "Interaction analysis of 68) Xu, Z., Wang, J., and Wang, W. (2008). "Deformation double holes extremely close approaching parallel shield behavior of diaphragm walls in deep excavations in tunnels construction." Chinese Journal of Rock Mechanics Shanghai." China Civil Engineering Journal, 41(8), 81-86. and Engineering, 28(9), 1856-1862. 69) Yang, L. (2011). " The repair construction technology for a 52) Wang, C., Ding, W., Liu, W., and Qiao, Y. (2013). "Analysis tunnel accident in a city [C].Underground Transportation on Distribution Law of Soil Settlement Caused by Unsteady Projects and Work Safety: Proceedings of China'5th Dewatering of Confined Water." Journal of Tongji International Symposium on Tunneling." 48-52. University(Natural Science)(3), 361-367. 70) Yao, G., Lv, G., and Yang, Y. (2008). "Construction Safety 53) Wang, H. (2009). "Calculation of cutterhead torque for EPB Analysis Arising from the Foundation Pit Collapse of a shield and the relationship between cutterhead torque and Subway Station." Urban Rapid Rail Transit, 21(2), 71-78. shield driving parameters." China Civil Engineering Journal, 71) Ye, Y., Zhu, H., and Wang, R. (2007). "Analysis on the 42(9), 109-130. current status of metro operation tunnel damage in soft 54) Wang, H., Huang, M., Lv, X., and Zhou, W. (2013). ground and its causes." Chinese Journal of Underground "Upper-bound limit analysis of stability of shield tunnel face Space and Engineering, 3(1), 157-160. considering seepage." Chinese Journal of Geotechnical 72) Yi, X., Zhang, D., Pang, T., and Luo, J. (2009). "Practice and

23 monitoring analysis of building lifting due to grouting [J]." soils outside excavations." Chinese Journal of Geotechnical Rock and Soil Mechanics, 30(12), 3777-3782. Engineering, 36(2), 273-285. 73) Yuan, J., Liu, X., and Chen, W. (2012). "Effect of 89) Zheng, G., Deng, X., and Liu, Q. (2015). "Analysis of construction of deep excavation in Hangzhou silty sand on responses of existing shield tunnel to pressure-relief in adjacent metro tunnels and stations." Chinese Journal of confined aquifer." Rock and Soil Mechanics, 36(1). Geotechnical Engineering, 34(S1), 398-403. 90) Zheng, G., Du, Y., and Diao, Y. (2015). "Analysis of isolation 74) Zhang, C., Han, K., Zhang, D., Li, H., and Cai, Y. (2014). pile on displacement controlling of existing tunnel adjacent "Test study of collapse characteristics of tunnels in soft to excavation." Chinese Journal of Rock Mechanics and ground in urban areas." Chinese Journal of Rock Mechanics Engineering, 34,supp.1.,1-12. and Engineering, 33(12), 2433-2442. 91) Zheng, G., and Li, Z. (2012). "Comparative analysis of 75) Zhang, C., Zhang, D., Wang, M., Li, Q., and Liu, S. (2010). responses of buildings adjacent to excavations with different "Catastrophe mechanism and control technology of ground deformation modes of retaining walls." Chinese Journal of collapse induced by urban tunneling." Rock and Soil Geotechnical Engineering, 34(6), 971-982. Mechanics, 31(Supp. 1), 303-309. 92) Zheng, G., and Li, Z. (2012). "Finite element analysis of 76) Zhang, C., Zhang, D., Wang, M., Li, Q., and Liu, S. (2010). response of buildings with arbitrary angle adjacent to "Catastrophe mechanism and control technology of ground excavations." Chinese Journal of Geotechnical Engineering, collapse induced by urban tunneling." Rock and Soil 34(4), 615-624. Mechanics, S1. 93) Zheng, G., Lu, P., and Diao, Y. (2015). "Advance 77) Zhang, D., Fang, Q., Hou, Y., Li, P., and Yuen Wong, L. N. speed-based parametric study of greenfield deformation (2013). "Protection of Buildings against Damages as a Result induced by EPBM tunneling in soft ground." Computers and of Adjacent Large-Span Tunneling in Shallowly Buried Soft Geotechnics. 65, 220-232. Ground." Journal of Geotechnical and Geoenvironmental 94) Zheng, G., Wang, Q., Deng, X., and Du, Y. (2014). Engineering, 139(6), 903-913. "Comparative analysis of influence of deformation modes of 78) Zhang, D., Huang, H., and Yang, J. (2006). "Influence of retaining structures on deformation of existing tunnels partial drainage of linings on long-term surface settlement outside of the excavation." Chinese Journal of Geotechnical over tunnels in soft soils." Chinese Journal of Geotechnical Engineering, (Accepted). Engineering, 27(12), 1430-1436. 95) Zheng, G., Wang, Q., Deng, X., and Liu, Q.-c. (2014). 79) Zhang, K., and Li, J. (2010). "Accident analysis for „08.11. "Influence of pressure-relief of confined aquifer on existing 15‟ foundation pit collapse of Xianghu Station of Hangzhou tunnel under conditions of different inserted lengths of metro." Chinese Journal of Geotechnical Engineering, 32. diaphragm wall." Rock and Soil Mechanics. 80) Zhang, M., Wang, X., and Wang, Y. (2012). "Numerical 96) Zheng, G., and Zeng, C. (2014). "Technical report: evaluation of uplifting effect for upper structure by Double-well recharging system and field tests." Tianjin grouting." Journal of Central South University of Technology, University, Tianjin. 19, 553-561. 97) Zheng, G., Zeng, C., Diao, Y., and Xue, X. (2014). "Test and 81) Zhang, M., Zhao, M., Wang, P., Jia, D., Liu, Y., and Du, Y. numerical research on wall deflections induced by (2012). "Field test and analysis of segment secondary pre-excavation dewatering." Computers and Geotechnics, 62, stresses in small interval shield tunnel during construction." 244-256. Chinese Journal of Geotechnical Engineering, 34(11), 98) Zheng, G., Zeng, C., Liu, C., Shi, X., Zong, C., and Xue, X. 2121-2126. (2013). "Field observation of artificial recharge of confined 82) Zhang, X., Hu, X., and Scott, K. (2011). "A discrete water in first excavation case in Tianjin." Chinese Journal of numerical approach for modeling face stability in slurry Geotechnical Engineering, 35(S2), 491-495. shield tunneling in soft soils." Computers and Geotechnics, 99) Zheng, G., Zeng, C., Diao, Y and Xue, X. (2014). 38(4), 94-104. "Settlement mechanism of soils induced by local 83) Zhang, Y., Ding, W., Liu, X., Wang, X., and Wu, J. (2013). pressure-relief of confined aquifer and parameter analysis." "Internal force and deformation of deep foundation pit under Chinese Journal of Geotechnical Engineering, 36(5), asymmetric water pressure." Chinese Journal of 802-817. Geotechnical Engineering, 35(zk2), 107-112. 100) Zheng, G., Zhang, T., and Diao, Y. (2015). "Mechanism and 84) Zhang, Z., Kan, C., Sun, F., Guo, Y., and Li, H. (2014). countermeasures of preceding tunnel distortion induced by "Experimental study of catastrophic behavior for NATM succeeding EPBS tunneling in close proximity. Computers tunnel in debris flow strata." Chinese Journal of Rock and Geotechnics." Computers and Geotechnics, 65(4), Mechanics and Engineering, 33(12), 2451-2457. 220–232. 85) Zheng, G., Cheng, X., and Zhang, Y. (2014). "Progressive 101) Zheng, Y., Li, M., Wang, M., and Yang, L. (2005). "Study collapse simulation and redundancy study of ring-beam on influence of seepage of metro tunnels in soft soil on the supporting structures of excavations. Chinese Journal of settlements of tunnels and ground." Chinese Journal of Geotechnical Engineering." Chinese Journal of Geotechnical Geotechnical Engineering, 27(2), 243-247. Engineering, 36(1), 105-117. 102) Zhou, N., Vermeer, P. A., Lou, R., Tang, Y., and Jiang, S. 86) Zheng, G., Cheng, X. S., and Diao, Y. (2011). "Concept and (2010). "Numerical simulation of deep foundation pit design methodology of redundancy in braced excavation and dewatering and optimization of controlling land subsidence." case histories." Geotechnical Engineering Journal of the Engineering Geology, 114(3), 251-260. SEAGS & AGSSEA, 42(3), 13-21. 103) Zhu, W., and Ju, S. (2009). Research of shield tunnel 87) Zheng, G., Dai, X., and Zhang, X.-s. (2014). "Experimental construction risk and typical accident, Jinan University Press. study and numerical simulation of leaking process of sand 104) Zhu, Y., Ye, S., and Mo, Y. (2010). "Analysis and treatment and water of underground engineering." Chinese Journal of of a deep foundation pit accident in Xining, Qinghai Rock Mechanics and Engineering, 33(12), 2458-2461. Province." Chinese Journal of Geotechnical Engineering, S1. 88) Zheng, G., Deng, X., Liu, C., and Liu, Q. (2014). "Comparative analysis of influences of different deformation modes of retaining structures on displacement field of deep

24