Hindawi Advances in Civil Engineering Volume 2019, Article ID 4145721, 12 pages https://doi.org/10.1155/2019/4145721 Research Article Numerical Study and Field Monitoring of the Ground Deformation Induced by Large Slurry Shield Tunnelling in Sandy Cobble Ground Chengping Zhang ,1,2 Yi Cai,1,2 and Wenjun Zhu 1,2 1Key Laboratory of Urban Underground Engineering of Ministry of Education, Beijing Jiaotong University, Beijing 100044, China 2School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China Correspondence should be addressed to Wenjun Zhu; [email protected] Received 29 September 2018; Accepted 18 December 2018; Published 3 February 2019 Academic Editor: Daniele Baraldi Copyright © 2019 Chengping Zhang et al. +is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. +is paper presents the ground deformation induced by the large slurry shield tunnelling with a diameter of about 12 m in urban areas, which may challenge the safety of the existing nearby constructions and infrastructures. In this study, the ground de- formation is analyzed by a three-dimensional finite difference model, involving the simulation of tunnelling advance, grouting, and grouting hardening. +e transverse settlement, longitudinal settlement, and horizontal displacement of the ground are analyzed by comparing the simulation results with the field measurements in the Rapid Transit Line Project from Beijing Railway station to West Beijing Railway station in China. +e numerical model proposed in this paper could well predict the ground deformation induced by large slurry shield tunnelling. +e results show that the main transverse settlement occurs within the zone about 1.5 times of the excavation diameter, and the settlement during the passage of the shield and the tail void plays a most important role in the excavation process. 1. Introduction roadway, the empirical method was first put forward by Martos [6], and the error function was suggested to present At present, lots of tunnels are constructed or being planned the surface settlement through profile approximately. A to relieve the traffic pressure in metropolis. +e application description of the green-field settlement was proposed by of the slurry shield method to urban tunnel construction in collecting field observations from many case histories over sandy cobble ground is more and more popular for its the years by Peck [7], and O’Reilly and New [8, 9] sum- comfortable work environment [1]. Ground deformation is marized plenty of empirical equations and pointed out that inevitably induced by the excavation of the slurry shield Peck’s empirical method is unable to provide a reasonable tunnel in urban areas, which is negative to the existing prediction for soils other than normally consolidated clays, structures and pipelines. As a result, a great deal of attention as the empirical model is based on limited scope of the has been attracted all over the world [2, 3]. Several ap- database. With the assumption that the ground loss is proaches, such as the empirical method, model test, nu- uniformly distributed along the longitudinal direction, the merical simulation, and field monitoring, have been used to settlement profile can be expressed by Gaussian distribution. estimate the ground deformation during the shield Attewell and Woodman [10] suggested that the longitudinal tunnelling. settlement at any longitudinal coordinate can be described +e empirical method is based on the regression analysis by cumulative Gaussian probability. of the recorded ground surface settlement and then used to Model test is also a common way to investigate the predict the ground surface settlement [4, 5]. Based on the evolution law of the ground deformation, including the ground surface settlement measured in the field of a mine centrifuge model test and physical model test [11]. Based on 2 Advances in Civil Engineering a series of plane-strain centrifuge model tests on the single 2. Project Description and Monitoring tunnels in moderately stiff clay, Grant and Taylor [12] found that the high-quality data can be used to improve the In order to alleviate traffic congestion and improve the predictions of both surface and subsurface movements in the ground surface environment of Beijing, the capital city in plane transverse to the tunnel. And a procedure for pre- China with a population of around 30,000,000, the RTLP was dicting horizontal movements as a function of the vertical started in 2005, which begins at Beijing West Railway Station settlement profile was also suggested. Kuwahara et al. [13] in the west and ends at Beijing Railway Station in the east as investigated the mechanism of ground settlement in the shown in Figure 1. +e total length of the RTLP is 9,151 m. process of tail void by the centrifuge model test and found +e tunnel takes up about 7,230 m in the whole project, with that the ground deformation mechanism in the field had a a buried depth varying from 16 to 22 m. 5,227 m of the close similarity with the results observed in the physical tunnel is constructed by the slurry shield, while other parts models. Atkinson and Potts [14] investigated the influence of are built by the open-cut method and mining method. It the depth of burial and crown settlement on the surface should be pointed out that there are several historical subsidence above shallow tunnels in soft ground. Compared buildings with traditional Chinese style above the tunnel with the observations of settlements above some existed including Jianlou and Zhengyangmen, which are particu- tunnels, the model’s behaviour matches with the field re- larly sensitive to the subsidence induced by excavation. cords well, and an empirical relationship is given between Considering the historical, cultural, and communal value of the buried depth, the trough width, the crown, and surface these buildings, the evaluation of the ground surface set- settlements for tunnels in sands and in clays. tlement is the key ingredient in the design stage and during With the development of the computer technique and the whole construction process. +us, a monitoring system numerical software, the numerical simulation method has was set along the tunnel to investigate the effects of exca- become more and more effective to solve the problem in vation on the ground deformation. +e monitoring portion tunnel construction [15, 16]. Finno and Clough [17] sim- considered in this study is the first 509 m of the shield tunnel ulated the entire EPB tunnelling process in five stages by the which begins at the north of Tianningsi Bridge. finite element program and obtained the lateral displace- In this project, results of extensive in situ and laboratory ment. Do et al. [18] proposed a finite element method to tests provided a description of the different geological for- study the failure mechanisms of deep excavations in soft mations. A typical geological profile of the shield tunnel is clay. Besides, Melis et al. [19] assessed the accuracy of each shown in Figure 2. +e profile reveals that the monitoring analytical or empirical predictive method with reference to portion of the shield tunnel is mainly located in gravel the soil movements using a numerical model of shield tunnel environment. Figure 3 shows the typical in situ soil of this excavation. project. Figure 4 shows the distribution of the grain size Field monitoring is also widely used in the tunnel obtained by the indoor screening test. +e results indicate construction [1]. Chen et al. [20] mainly focused on the field that the maximum grain diameter is about 300 mm. +e measurements of parallel tunnels using EPB shields in silty elliptical gravel with strong compression capacity accounts soils. +is research revealed the changes of pore pressure in for 12%. It can also be found that about 1/3 of the sands are the soils and ground deformation during EPB shield tun- in the size from 0.25 mm to 0.5 mm. According to the nelling. Generally, field measurement can be used in available documents about the water table in the excavation combination with other methods. Sugiyama et al. [21] area, the influence of the underground water level can be compared the field measurement of ground deformation due negligible. to slurry shield tunnelling with the model test and numerical +e slurry shield used in this project with a total length of simulation, and two kinds of practical design charts were about 11.52 m is characterized by an outer diameter of proposed to appropriately predict the transverse surface 11.97 m at the face and 11.95 m at the tail. However, in some settlement troughs in the clays or sands and gravels. Ocak special circumstances, the maximum excavation diameter at [22] proposed a new empirical formula for estimating the the face can reach up to 12.04 m. surface transverse settlement trough of twin tunnels. +e tunnel lining is fabricated by concrete with the Moreover, the comparison with field measurement validated maximum compressive strength of 50 MPa based on the the reasonability of an empirical formula. experimental tests on the cubic specimens with the di- However, it should be pointed out that the studies above mensions of 150 mm × 150 mm × 150 mm. +e tunnel lining mainly focused on the influences of small diameter shield is set in place inside the shield tail to support the sur- excavation on the ground deformation. +e research on the rounding rock as the machine moves forward. +e outer and large-diameter shield excavation in sands and gravels is still inner diameters of the lining ring are equal to 11.6 m and limited up to now. In this study, a three-dimensional nu- 10.5 m, respectively.