Building Deformation Prediction Based on Ground Surface Settlements of Metro-Station Deep Excavation

Hindawi Advances in Civil Engineering Volume 2018, Article ID 6050353, 14 pages https://doi.org/10.1155/2018/6050353

Research Article Building Deformation Prediction Based on Ground Surface Settlements of Metro-Station Deep Excavation

Dapeng Li and Changhong Yan

School of Earth Sciences and Engineering, Nanjing University, No. 163 Xianlin Road, Qixia District, Nanjing, China

Correspondence should be addressed to Dapeng Li; [email protected]

Received 1 May 2018; Revised 30 August 2018; Accepted 13 September 2018; Published 10 October 2018

Guest Editor: Zhanguo Ma

Copyright © 2018 Dapeng Li and Changhong Yan. *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. Building deformations are not only closely related to the distance from the building to metro-station excavation but also related to the relative positions of the building and metro-station excavation. Building deformations can be predicted using ground surface settlement profiles. Based on typical geological parameters of Nanjing metro-station excavation, ground surface settlements were numerically simulated by auxiliary planes perpendicular and parallel to the excavation and by angled auxiliary planes at the excavation corner. Results show that the ground surface settlement profiles in auxiliary planes are closely related to the relative positions of the auxiliary planes and the metro-station excavation. Partitioning of ground surface settlements was proposed according to the three types of ground surface settlement profiles; furthermore, bending deformation and torsional deformation regularities of surrounding buildings were analyzed, and an estimation method for building settlements was developed. Finally, field-monitored settlement data of 21 buildings in different zones were compared with the estimated settlement data, and the application of the settlement estimation method to different types of foundations was analyzed. *e results of this study can serve as reference for metro-station deep excavation construction and protection of surrounding buildings.

1. Introduction auxiliary planes [9, 10]. However, few studies have investigated ground surface settlements in the case of 3D Metro-station deep excavations are generally located in states, especially ground surface settlements in angled bustling areas of a city. *e excavation design should meet auxiliary planes and in parallel auxiliary planes. not only the strength and stability requirements of the Building deformation around metro-station excavation support structure but also the deformation-control re- involves geotechnical-structural interaction, making it quirements of the surrounding environment [1]. Soil-mass a cross-disciplinary geotechnical engineering problem. Son displacements around station excavations have complex and Cording [11] studied the phenomenon of building three-dimensional (3D) characteristics. However, previous failure due to excavation in scaled models of 1 :10 and found studies mainly focused on wall deflection and involved that cracks in buildings can be classified as “shear + tension,” limited considerations for ground surface settlements “convex + stretch,” and “concave + stretch.” *e different [2–8]. Ground surface settlements can be studied through deformation forms are closely related to the ground surface auxiliary planes perpendicular and parallel to the excava- settlement profile; that is, the relative position relationship tion, as well as through angled auxiliary planes at the between the building and excavation determines the de- excavation corner (Figure 1). formation form of the building. *ese conclusions are Ground surface settlements in the perpendicular aux- consistent with the numerical simulation results reported by iliary plane have been studied by many scholars but mainly Zheng and Li [12–14]. In addition, Bryson and Zapata- in the case of two-dimensional (2D) plane-strain states. For Medina [15] and Sabzi and Fakher [16] studied building example, researchers have proposed triangular and trough- deformations around excavations through field monitoring, shaped ground surface settlement profiles in perpendicular theoretical analysis, and numerical simulation. 2 Advances in Civil Engineering

symmetry can be considered in rectangular excavation, and Angled auxiliary plane only one-half or one-quarter model can be used for the analysis. Boundary conditions were generally set up such that the ground surface boundary was a free boundary, the Perpendicular auxiliary plane displacements of lateral boundaries were constrained in the Parallel auxiliary plane horizontal direction, and the displacement of the bottom boundary was constrained in the vertical direction. *e initial stress equilibrium was achieved by applying a gravi- Support structure tational field. In general, the width and depth of the deep excavations of Nanjing metro stations were approximately 20 m, while Station excavation the length was approximately 200 m [17]. To improve the calculation efficiency, the middle part of the deep excavation was considered to be in a 2D plane-strain state; therefore, Figure 1: Auxiliary planes around station excavation. appropriate size reduction in the length direction of the model could meet the analysis requirements. Taking the size Li et al. [17] studied ground surface settlement profiles by of the station excavation as 120 m × 20 m × 20 m, the one- analyzing field-monitoring data of 30 station excavations in half model was established with dimensions of 200 m × the construction of Nanjing Metro Line 3, Line 10, and Line 150 m × 90 m, as shown in Figure 2. *e soil mass was S8. In the present study, the modified Cam-clay model was modeled using 8-node 6-faceted elements. adopted with typical geological parameters in the Nanjing Nanjing is located in the lower reaches of the Chang Jiang region, and the 3D characteristics of ground surface set- river, belonging to the Yangtze depression fold belt in geo- tlements resulting from station excavation were numerically tectonic geology. Marine strata, continental strata, and marine- analyzed using FLAC3D. *e numerical simulation in the continental strata of different eras have been alternately de- present paper is a supplementary study to the report by Li posited here since the Sinian period. *e ground surface et al. [17]. Li et al. [17] reported that three types of ground consists mostly of Quaternary alluvial clay overlying Creta- surface settlement profiles suitable for different zones (zones ceous sandstones. Table 1 presents the clay soil parameters A, B, and C) around the excavation were obtained in the used in numerical analysis, which is typical for Nanjing. construction of Nanjing Metro Line 3, Line 10, and Line S8. *e present study conducted further research on building deformations. Partitioning of ground surface settlements 2.2. Modeling of Support Structure. *e support structure of was proposed according to the three types of ground surface station excavation is a combination of diaphragm walls and settlement profiles; then, a prediction method for the type of strutting levels. *e diaphragm walls had a reinforced building deformation and an estimation method for building concrete structure with a thickness of 0.8 m, the insertion settlements were developed. Finally, field-monitored data ratio of the diaphragm walls was 0.5 (the excavation depth is and estimated settlement values of building settlements were 20 m, so the diaphragm wall depth is 30 m, 10 m of which is compared, and the application of the settlement estimation under the excavation bottom, as shown in Figure 3), and method to different types of foundations was discussed. a liner lining element was used in the simulation. *e ex- It should be noted that the three surface settlement cavation was carried out in 5 steps of 4 m each, and 5 layers of horizontal support were built. A structure element beam profiles reported by Li et al. [17] were based on the greenfield st ground settlement. *us, the greenfield ground settlement was adopted in the simulation. *e 1 layer of strutting levels was used to assess the building deformation, and there was was a reinforced concrete beam with a cross section of 0.6 m × nd th no consideration of the excavation-building interaction. 0.8 m set at the surface; the 2 to 5 layers of strutting levels were steel pipe beams of ϕ609, with layer spacings of 4 m each (Figure 3). 2. Preparation of Numerical Analysis For each layer of strutting levels in the middle of the 2.1. Modeling of Soil Mass. According to Xu et al. [18] and station excavation, the beams were supported in parallel Ding et al. [19], the settlement influence range of excavation with a spacing of 4 m between them. In the corner of the is generally within 4 times the excavation depth. For soft-soil station excavation, the beams were in the form of bracing, areas with poor engineering properties, the settlement in- and the spacing between the supporting points was 4 m. *e fluence range will not exceed 5 times the excavation depth. parameters of diaphragm walls and strutting levels are listed Zheng and Jiao [1] showed that the influence range of in Table 2. bottom uplift of deep excavation is generally 2 times the excavation depth. Furthermore, the choice of the soil con- 3. Ground Surface Settlements around stitutive model is very important in numerical analysis. the Excavation According to analyses of different constitutive models by Ou et al. [20], Potts [21], Antonio´ et al. [22], and Anthony et al. *ere are two types of ground surface settlement profiles: [23], the modified Cam-clay model is preferred for deep- triangular and trough-shaped [10]. For the cantilever sup- excavation analysis. To improve the calculation efficiency, port structure without strutting levels, the ground surface Advances in Civil Engineering 3

150m

60m

20m 90m 20m

200m

Figure 2: Soil-mass model.

Table 1: Parameters of the clay soil. Slope of Slope of Initial Soil Porosity Poisson’s Lateral pressure Slope of initial expansion critical state volumetric gravity ratio ratio coeﬃcient consolidation line Parameters line line ratio OCR γ e μ K λ κ M ] (kN/m3) 0 0 Data 19.6 0.705 0.343 0.451 0.093 0.012 0.843 2.040 1

10m 30m

Figure 3: Support structure model.

Table 2: Parameters of the support structure. Moment of Young’s modulus, Poisson’s *ickness, t Cross-sectional area, Polar moment of Material 2 inertia E(GPa) ratio, μ (m) A (m ) inertia, Ip Iy Iz C30 Diaphragm walls 30 0.20 0.8 ———— concrete C30 1st strutting level 30 0.20 — 0.48 0.026 0.014 0.040 concrete 2nd to 5th strutting ϕ609steel 206 0.27 — 0.03 0.001 0.001 0.003 levels pipe settlement profile is generally triangular, while for the maximum settlement position, and influence range of set- support structure with strutting levels, the ground surface tlement. *e ground surface settlements can be analyzed settlement profile is generally trough-shaped. *e study of through the perpendicular auxiliary plane, parallel auxiliary ground surface settlements mainly focuses on important plane, and angled auxiliary plane around the station exca- parameters such as the maximum settlement value, vation (Figure 1). 4 Advances in Civil Engineering

3.1. Ground Surface Settlements of the Short Side, Long Side, ground surface settlement profiles take the trough- and Excavation Corner at Different Positions. When the shaped form. *e maximum settlement values and excavation depth H � 20 m, the perpendicular auxiliary planes the positions of the maximum settlement values of at different positions around the station excavation were the trough-shaped settlement both decrease with analyzed to investigate the regularities of ground surface increase in l. settlements at different positions around the station exca- (3) When the parallel auxiliary planes are far from the vation, as shown in Figure 4. In the figure, l represents the diaphragm wall (l > 10 m), the ground surface set- distance from the perpendicular auxiliary plane to the ex- tlement values δv do not increase when d > 10 m but cavation corner, and the corner 30° direction auxiliary plane instead continue to decrease; the rate of decrease indicates that the plane at the corner is at an angle of 30° with slows down, and the ground surface settlement respect to the perpendicular auxiliary plane l � 0 m. A similar profiles take the triangular form. definition applies to the corner 45° direction auxiliary plane. Figure 4(a) shows the variation regularities of the ground Figure 5(b) shows the variations of ground surface set- surface settlements at different positions on the short side. It tlements in the parallel auxiliary planes outside the long-side can be observed that the settlements decrease continuously support structure at different distances from the diaphragm from the short-side center perpendicular auxiliary plane to wall, where the position d � 60 m is the excavation corner. On the corner 45° direction auxiliary plane; however, the po- the two sides of the demarcation plane l � 10 m, when d > sitions of the maximum ground surface settlements grad- 10 m, the ground surface settlements show two types of ually shift away from the diaphragm wall. profiles: trough-shaped and triangular. *e settlement trend Figure 4(b) shows the variation regularities of the ground in the parallel auxiliary planes is related to that in the per- surface settlements at different positions on the long side. It pendicular auxiliary planes around the station excavation. can be observed that when l > 28 m, the ground surface settlement curves coincide, indicating that this region is in 4. Partitioning of Ground Surface Settlements the 2D plane-strain state. In the process of transition from l � 28 m to l � 0 m, the ground surface settlements decrease Based on the numerical analysis of ground surface settlements while the positions of the maximum surface settlement move and according to the three settlement profiles in the three types closer to the diaphragm wall to a certain extent owing to 3D of zones (zone A, B, and C) around the station excavation [17], effects. In the process of transition from l � 0 m to the corner partitioning of ground surface settlements was proposed, as 45° direction, the ground surface settlements decrease fur- shown in Figure 6. *ere are three critical positions of set- ther, but the positions of the maximum settlements moved tlements outside the diaphragm wall: the maximum settlement farther away from the diaphragm wall, which is essentially line, settlement turning line, and settlement boundary line. *e the same as that of the long-side center perpendicular area within the settlement boundary line is referred to as the auxiliary plane without 3D effects. main influence area. In this region, the influence of surface *e variation regularities of vertical settlements at dif- settlements is significant, and the buildings are subject to ferent positions were consistent with the results reported by significant differential settlements. *e area outside the set- Li et al. [17]. tlement boundary line is referred to as the secondary influence area. In this region, the statistical values of surface settlements are generally distributed within 0–3 mm, and the surface 3.2. Ground Surface Settlements within the Parallel Auxiliary settlements have little influences on the buildings. For a deep Plane. Figure 5 shows the variations of ground surface metro-station excavation, buildings in the main influence area settlements in the parallel auxiliary planes around the station should be monitored and protected. Minor settlements may excavation, where l represents the distance from the parallel also occur in the secondary influence area, but the settlement auxiliary plane to the diaphragm wall. *e position d � 0 m is hazard in this area is negligible. the midpoint of the diaphragm wall, while positions d � 10 m It can be observed from Figure 6 that there are three types and d � 60 m in Figures 5(a) and 5(b), respectively, corre- of zones around the station excavation, namely, zones A, B, and spond to the excavation corner. C, and each zone has three critical settlement lines: the Consider the parallel auxiliary planes outside the short- maximum settlement line, settlement turning line, and set- side support structure. It can be observed from Figure 5(a) tlement boundary line. *e variation regularities are as follows: that the ground surface settlements in the parallel auxiliary (1) Compared to zone A and zone C, the critical set- planes at different distances l outside the diaphragm wall tlement lines of zone B are considerably short. exhibit the following characteristics: (2) *e distances in zone C from the critical settlement (1) During the transition from d � 0 m to 10 m, the lines to the excavation corner are the same as those in ground surface settlement values δv gradually zone A; however, the critical settlement lines of zone decrease. C are circular arcs with the excavation corner as the (2) When the parallel auxiliary planes are close to the center. diaphragm wall (l � 2 m, 6 m, and 10 m), the ground (3) *e critical settlement lines of zone B are not the surface settlement values δv increase for d > 10 m settlement contour lines, and the settlement values (position d � 10 m is the excavation corner), and the decrease from zone A to zone C. *e critical Advances in Civil Engineering 5

1 2 0 0 –1 –2 –2 –4 –3 –6 –4 –8 –5 –10 –6 –12 –7 –14 –8 –16 (mm) (mm) v –9 v –18 δ –10 δ –20 –11 –22 –12 –24 –13 –26 –14 –28 –15 –30 –5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 –5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 d (m) d (m) 45° direction l =4m 45° direction l =12m l =32m 30° direction l =6m 30° direction l =16m l =36m l =0m l =8m l =0m l =20m l =50m l =2m l =10m l =4m l =24m l =60m l =8m l =28m

(a) (b)

Figure 4: Ground surface settlements at diﬀerent positions: (a) short side and (b) long side.

2 2 0 0 –2 –2 –4 –4 –6 –6 (mm) (mm) v v

δ –8 δ –8 –10 –10 –12 –12 –14 –14 –16 –16 0102030 40 50 60 70 0 20 40 60 80 100 120 d (m) d (m) l =2m l =20m l =2m l =20m l =6m l =30m l =6m l =30m l =10m l =40m l =10m l =40m l =15m l =15m

(a) (b)

Figure 5: Ground surface settlements in the parallel auxiliary planes outside the (a) short side and (b) long side.

settlement lines of other zones can be regarded as Buildings located around the station excavation will settlement contours. inevitably cross the critical settlement lines. *e relative position relationship between the building and excavation will directly affect the building deformations. 5. Prediction of Building Deformations Buildings are generally composed of longitudinal walls, inner longitudinal walls, transverse walls, and inner transverse *ere are mainly two methods to predict building de- walls. *e deformation regularities of buildings can be ana- formations due to excavation: the finite element method lyzed from two aspects, as shown in Figure 7: “bending de- (FEM) and simplified analysis method (SAM). *e process formation of wall” and “torsional deformation of building.” of FEM is complex and not easily performed by engineers. SAM is used to predict building deformations through ground surface settlements. *is method is simple and easily 5.1. Bending Deformation of Wall. Consider the building in applied in practice [24–26]. zone A. When the building is perpendicular to the 6 Advances in Civil Engineering

Main influence area Secondary influence area

Maximum Settlement Settlement settlement line turning line boundary line

0 5 10 15 20253035 4045 50 (m) 5mm 10mm Zone A

30mm

Station excavation

Ground surface 0 5 10 15 20253035 4045 50 (m) M 10mm 5mm Zone B 0 0 25mm 5 10 10mm 15 5 20 25 10 30 10mm 35 15 4045 20 2.5mm 50 25mm (m) 25 5mm 30 35 Zone C 40 45 M: distance affected by 3-D effects, about 1.5 times 50 Zone B (m) the excavation depth and 1/10 of the excavation length. Figure 6: Partitioning of ground surface settlements. excavation (α � 90°), the longitudinal walls of the building deflections of the concave and convex deformations will exhibit bending deformation. Because the transverse are small; therefore, the main tensile strains on the wall is parallel to the diaphragm wall without differential wall are not significant. settlement, there will be no bending deformation. Similarly, (3) As the distance from the building to the diaphragm when the building is parallel to the excavation (α � 0°), only wall d increases further, the building mainly crosses the transverse walls will exhibit bending deformation. When the settlement turning line. Under this condition, the the building and the excavation are at angles in the range of main tensile strain on the longitudinal wall shows 0° < α < 90° in zone A, or when the building is located in a crest-shaped distribution. zones B or C with 3D effects, longitudinal and transverse (4) If the distance from the building to the diaphragm walls will cross the critical settlement lines; these longitu- wall d increases further, the main tensile strain on the dinal and transverse walls will exhibit bending deformation longitudinal wall will be significantly weakened simultaneously. owing to the rapid decrease in the surface settle- (1) As shown in Figure 8, when the building crosses the ments. When the building is located outside the maximum settlement line, it will be affected by surface settlement boundary line, it is no longer concave-bending deformation. Under this condi- affected by bending deformation. tion, the main tensile strain on the longitudinal wall is trough-shaped. Assuming that the building is perpendicular to the diaphragm wall, bending de- 5.2. Torsional Deformation of Building. When the building formation occurs on the longitudinal wall only. and the excavation are in the range of 0° < α < 90°, the two parallel longitudinal walls will simultaneously cross the (2) As the distance from the building to the diaphragm critical surface settlement lines. Owing to the positions of wall d increases, when a part of the building crosses settlements, the critical lines crossing the two walls are the maximum settlement line and another part different; therefore, in addition to the bending deformation crosses the settlement turning line, the building will of each wall, the building also exhibits torsional be affected by both concave-bending deformation deformation. and convex-bending deformation. *e main tensile strain on the longitudinal wall will be trough-shaped (1) As shown in Figure 9, when the building crosses the near the excavation and crest-shaped away from the maximum settlement line, the maximum settlement excavation. It can be observed from Figure 8 that point of the back longitudinal wall is located closer to although the building exhibits both concave and the front transverse wall than that of the front convex bending deformations simultaneously, the longitudinal wall. Consequently, the building will Advances in Civil Engineering 7

Inner transverse wall Back wall Inner longitudinal wall Transverse wall Longitudinal wall

Front wall

d α Support structure Settlement turning lin Maxim Station excavation um settlem e ent line

Figure 7: Building around the station excavation.

Maximum Settlement Settlement settlement point turning point boundary point Support structure

Station excavation d m

α Longitudinal wall: m = asin d m Transverse wall: m = bcosα a: length of longitudinal wall b: length of transverse wall d: Vertical distance of wall to excavation Figure 8: Bending deformation of a wall.

exhibit torsional deformation. *e direction of the clockwise rotation. In contrast, the back transverse torsional deformation of the front longitudinal wall wall exhibits counterclockwise rotation since the is clockwise, while that of the back longitudinal wall right side of the back transverse wall is closer to the is counterclockwise. Because the left side of the front settlement turning line than the left side. transverse wall is closer to the maximum settlement (3) Similar analysis can be carried out for the arc-shaped line than the right side, the front transverse wall critical settlement lines in zone C, as shown in Fig- exhibits counterclockwise rotation. In contrast, the ure 11. It can be concluded that the front longitudinal back transverse wall exhibits clockwise rotation since wall exhibits counterclockwise rotation, the back lon- the right side of the back transverse wall is closer to gitudinal wall exhibits clockwise rotation, the front the maximum settlement line than the left side. Note transverse wall exhibits clockwise rotation, and the back that the clockwise direction, counterclockwise di- transverse wall exhibits counterclockwise rotation. rection, left side, and right side in this context are the relative position relationships when the observer *e above analysis of the longitudinal and transverse faces the facade. walls can be carried out for the inner longitudinal and transverse walls. *e analysis above indicates that when (2) As shown in Figure 10, when the building crosses the α � 0°, 90° or the center symmetrical line of the building in settlement turning line, the settlement turning point zone C passes through the excavation corner, the positions of the back longitudinal wall is located closer to the of the critical settlement line through the parallel walls are front transverse wall than that of the front longi- the same. Consequently, the walls only exhibit bending tudinal wall. Consequently, the building will exhibit deformation and do not exhibit torsional deformation. torsional deformation. *e direction of torsional deformation of the front longitudinal wall is counterclockwise, while that of the back longitudinal wall 6. Estimation of Building Settlements is clockwise. Because the left side of the front transverse wall is closer to the settlement turning line According to Li et al. [17], the maximum surface settlements than the right side, the front transverse wall exhibits δVm can be directly estimated from the excavation depth H; 8 Advances in Civil Engineering

Maximum Settlement Settlement settlement line turning line turning line

d 2 Station Building excavation d Building Maximum 1 settlement line d 2 d m 1 m Station m excavation m

Figure 9: Torsional deformation of a building across the maximum Figure settlement line. 11: Torsional deformation of a building located outside the excavation corner.

Maximum Settlement settlement line turning line compared with the estimated free surface settlement values, as shown in Figures 12–14. d 2 *e regularities between the actual foundation settle- Station ments and the estimated ground surface settlements are excavation d 1 Building summarized as follows: (1) For strip foundations, it can be observed from Fig- ures 12(a)–12(d), 13(a)–13(f), and 14(a)–14(d) that, m although there are deviations between the measured m settlement values of the strip foundation and the estimated values of the ground surface settlements, the trend is essentially the same. It should be noted that because the strip foundation itself has a certain resistance capacity to deformation, the actual settlement profile of the building foundation at the max- Figure 10: Torsional deformation of a building across the settle- imum settlement position of the surface settlement ment turning line. profile will not indicate a sharp angle but will rather be relatively smooth at the maximum settlement. (2) *e raft foundation has greater integral rigidity than then, the ground surface settlements at different zones can be the strip foundation, which is helpful to adjust the estimated through the ground surface settlement profiles. uneven settlement of the foundation. It can be ob- *e ground surface settlements in different zones are served from Figures 12(g), 13(g), and 14(g) that the regarded as the settlements of the building foundation. actual settlement values of the raft foundations are *erefore, the building settlements at different zones around generally smaller than the estimated ground surface the metro-station excavation can be estimated. settlements, and it is a conservative estimation to However, the ground surface settlements and building consider the ground surface settlements as the settlements may not be completely consistent with each building foundation settlements. other. *e relationship between building settlements and (3) Pile foundation is a type of deep foundation com- ground surface settlements should be further investigated. monly used in high-rise buildings. *e main ob- In this section, 21 buildings around the station exca- jective of using a pile is to utilize its own stiffness vations were selected for field monitoring. *e surroundings much more than that of the soil and to transfer the of the station excavation were divided into three different upper structure load to the hard soil or rock around zones, namely, zones A, B, and C, and there were seven the pile to reduce structure settlements. *erefore, buildings in each zone. *e building structures include the settlements of deep soil mass at the pile bottom can commonly used brick-concrete structure and the frame directly affect the pile foundation, while the influence structure, and the type of foundations mostly includes the of ground surface settlements on the pile foundation strip foundation, raft foundation, and pile foundation. *e is relatively small. *is can be verified as shown in measured settlement values of the building foundations were Figures 12(e), 12(f), 14(e), and 14(f). *e figures Advances in Civil Engineering 9

d (m) d (m) –10 –5 0 5 10 15 20 25 30 35 40 45 50 –10 –5 0 5 10 15 20 25 30 35 40 45 50 0 0 0 0 Excavation –5 5 –5 5 –10 10 –10 10 Excavation –15 15 –15 15 –20 20 –20 20 –25 –25 (mm) 25 (mm) 25 Z (m) Z (m) v Support v Support –30 30 δ –30 30 δ –35 Building information: 35 –35 Building information: 35 Distance to excavation is 8.6m, 6 ﬂoors, –40 40 –40 Distance to excavation is 11.4m, 7 ﬂoors, 40 brick-concrete structure, and strip foundation. brick-concrete structure, and strip foundation. –45 45 –45 45 –50 50 –50 50 –10–5 0 5 10 15 20 25 30 35 40 45 50 –10–5 0 5 10 15 20 25 30 35 40 45 50 d (m) d (m)

Estimated surface settlement Estimated surface settlement Monitored building settlement Monitored building settlement (a) (b) d (m) d (m) –10 –5 0 5 10 15 20 25 30 35 40 –10 –5 0 5 10 15 20 25 30 35 40 45 50 0 0 0 0 Excavation –5 5 –5 5 –10 10 –10 10 Excavation –15 15 –15 15 –20 20 –20 20 –25 25 (mm)

–25 Z (m) v 25 (mm) Z (m) Support v δ –30 30 δ –30 30 Support –35 Building information: 35 –35 35 Distance to excavation is 4.6m, 7 ﬂoors, Building information: –40 40 –40 40 brick-concrete structure, and strip foundation. Distance to excavation is 13.4m, 4 ﬂoors, –45 45 –45 frame structure, and strip foundation. 45 –50 50 –50 50 –10–5 0 5 10 15 20 25 30 35 40 45 50 –10 –5 0 5 10 15 20 25 30 35 40 d (m) d (m)

Estimated surface settlement Estimated surface settlement Monitored building settlement Monitored building settlement (c) (d) d (m) d (m) –10 –5 0 5 10 15 20 25 30 35 40 45 50 55 60 –10 –5 0 5 10 15 20 25 30 35 40 45 50 55 60 0 0 0 0 –5 5 –5 5 –10 10 –10 10 –15 Excavation 15 –15 15 –20 20 –20 20 –25 25 –25 25 (mm) (mm) Z (m) Z (m) v v –30 30 δ –30 30 δ –35 35 –35 35 Support Building information: Building information: –40 Distance to excavation is 25.0m, 23 ﬂoors, 40 –40 Distance to excavation is 7.6m, 8 ﬂoors, 40 –45 frame structure, and pile foundation. 45 –45 frame structure, and pile foundation. 45 –50 50 –50 50 –10 –5 0 5 10 15 20 25 30 35 40 45 50 55 60 –10 –5 0 5 10 15 20 25 30 35 40 45 50 55 60 d (m) d (m)

Estimated surface settlement Estimated surface settlement Monitored building settlement Monitored building settlement (e) (f) d (m) –10 –5 0 5 10 15 20 25 30 35 4540 0 0 –5 5 –10 Excavation 10 –15 15 –20 20 –25 25 (mm) Z (m) v –30 30 δ –35 Support Building information: 35 –40 Distance to excavation is 7.8m, 11 ﬂoors, 40 –45 frame structure, and ra foundation. 45 –50 50 –10 –5 0 5 10 15 20 25 30 35 4540 d (m)

Estimated surface settlement Monitored building settlement (g)

Figure 12: Building foundation settlements in zone A: (a) Xiaoshi Uptown Station: Shop Building; (b) Wuding Gate Station: Security Business Hall; (c) Wuding Gate Station: Wuzhou Motor Factory; (d) Mengdu Avenue Station: Aocheng Store; (e) Jimingsi Temple Station: Peace Mansion; (f) Daxinggong Square Station: Nanjing Library; (g) Jiulong Lake Station: Yihe District. 10 Advances in Civil Engineering

d d (m) (m) –10 –5 0 5 10 15 20 25 30 35 40 45 –10 –5 0 5 10 15 20 25 30 35 40 0 0 0 0 –5 5 –5 5 –10 10 –10 10 Excavation Excavation –15 15 –15 15 –20 20 –20 20 –25 25 –25 25 (mm) (mm) Z (m) v Z (m) v δ –30 Support 30 δ –30 Support 30 –35 Building information: 35 –35 Building information: 35 –40 Distance to excavation is 15.0m, 12 ﬂoors, 40 –40 Distance to excavation is 8.0m, 4 ﬂoors, 40 –45 frame structure, and strip foundation. 45 –45 brick-concrete structure, and strip foundation. 45 –50 50 –50 50 –10 –5 0 5 10 15 20 25 30 35 40 45 –10 –5 0 5 10 15 20 25 30 35 40 d d (m) (m)

Estimated surface settlement Estimated surface settlement Monitored building settlement Monitored building settlement (a) (b)

d (m) d (m) –10 –5 0 5 10 15 20 25 30 35 40 45 50 –10 –5 0 5 10 15 20 25 30 35 4540 0 0 0 0 –5 5 –5 5 –10 10 –10 10 Excavation Excavation –15 15 –15 15 –20 20 –20 20 –25 Support 25 –25 25 (mm) (mm) Z (m) Z (m) v v

δ Support δ –30 Building information: 30 –30 30 –35 Distance to excavation is 11.0m, 6 ﬂoors, 35 –35 Building information: 35 Distance to excavation is 12.6m, 6 ﬂoors, –40 brick-concrete structure, and strip foundation. 40 –40 40 frame structure, and strip foundation. –45 45 –45 45 –50 50 –50 50 –10 –5 0 5 10 15 20 25 30 35 40 45 50 –10 –5 0 5 10 15 20 25 30 35 4540 d (m) d (m)

Estimated surface settlement Estimated surface settlement Monitored building settlement Monitored building settlement (c) (d)

d (m) d (m) –10 –5 0 5 10 15 20 25 30 35 40 45 –10 –5 0 5 10 15 20 25 30 35 40 45 50 55 60 0 0 0 0 –5 5 –5 5 –10 10 –10 10 Excavation –15 15 –15 15 Excavation –20 20 –20 20 –25 25 (mm) –25 25 (mm) Z (m) v Z (m) v δ –30 Support 30 –30 Support 30 δ –35 Building information: 35 –35 Building information: 35 –40 Distance to excavation is 10.5m, 6 ﬂoors, 40 –40 Distance to excavation is 8.2m, 6 ﬂoors, 40 brick-concrete structure, and strip foundation. –45 45 –45 brick-concrete structure, and strip foundation. 45 –50 50 –50 50 –10 –5 0 5 10 15 20 25 30 35 40 45 –10 –5 0 5 10 15 20 25 30 35 40 45 50 55 60 d (m) d (m)

Estimated surface settlement Estimated surface settlement Monitored building settlement Monitored building settlement (e) (f) Figure 13: Continued. Advances in Civil Engineering 11

d (m) –10 –5 0 5 10 15 20 25 30 35 40 5045 0 0 –5 5 –10 10 –15 Excavation 15 –20 20 –25 25 (mm) Z (m) v –30 30 δ Support –35 Building information: 35 –40 Distance to excavation is 8.3m, 7 ﬂoors, 40 –45 frame structure, and strip foundation. 45 –50 50 –10 –5 0 5 10 15 20 25 30 35 40 5045 d (m)

Estimated surface settlement Monitored building settlement (g)

Figure 13: Building foundation settlements in zone B: (a) Xiaoshi Uptown Station: Xixia Power Company; (b) Xiaoshi Uptown Station: Xiaoshi Hospital; (c) Yuhua Gate Station: Yuhua Village Residential Building; (d) Fenghuangshan Park Station: Jiaotong Guesthouse; (e) Confucius Temple Station: Liugongxiang Community Building 1; (f) Confucius Temple Station: Liugongxiang Community Building 2; (g) Jimingsi Temple Station: No. 138 Residential Building of Southeast University.

d d (m) (m) –10 –5 0 5 10 15 20 25 30 35 40 45 50 –10 –5 0 5 10 15 20 25 30 35 40 45 0 0 0 0 –5 5 –5 5 –10 10 –10 10 Excavation Excavation –15 15 –15 15 –20 20 –20 20 Support –25 –25 25 (mm) (mm)

25 Z (m) v Z (m) v Support δ –30 30 δ –30 30 Building information: Building information: –35 –35 35 Distance to excavation is 13.0m, 5 ﬂoors, 35 Distance to excavation is 10.0m, 3 ﬂoors, –40 40 –40 brick-concrete structure, and strip foundation. 40 brick-concrete structure, and strip foundation. –45 45 –45 45 –50 50 –50 50 –10–5 0 5 10 15 20 25 30 35 40 45 50 –10–5 0 5 10 15 20 25 30 35 40 45 d d (m) (m)

Estimated surface settlement Estimated surface settlement Monitored building settlement Monitored building settlement (a) (b)

d (m) d (m) –10 –5 0 5 10 15 20 25 30 35 40 45 50 –10 –5 0 5 10 15 20 25 30 35 40 45 0 0 0 0 –5 5 –5 5 –10 10 –10 10 Excavation Excavation –15 15 –15 15 –20 20 –20 20 –25 25 –25 25 (mm) Z (m) Support Z (m) Support v (mm) v –30 30 δ –30 30 δ –35 Building information: 35 –35 Building information: 35 –40 Distance to excavation is 22.7m, 3 ﬂoors, 40 –40 Distance to excavation is 10.0m, 4 ﬂoors, 40 brick-concrete structure, and strip foundation. –45 45 –45 brick-concrete structure, and strip foundation. 45 –50 50 –50 50 –10–5 0 5 10 15 20 25 30 35 40 45 50 –5 0–105 10 15 20 25 30 35 40 45 d (m) d (m)

Estimated surface settlement Estimated surface settlement Monitored building settlement Monitored building settlement (c) (d) Figure 14: Continued. 12 Advances in Civil Engineering

d (m) d (m) –10–5 0 5 10 15 20 25 30 35 40 45 50 55 55 60 –10 –5 0 5 10 15 20 25 30 35 40 45 50 0 0 0 0 –5 5 –5 5 –10 10 –10 10 Excavation Excavation –15 15 –15 15 –20 20 –20 20 Support

–25 25 (mm) Z (m)

Building information: (mm)

v –25 25 v Z (m) δ

Building information: δ –30 Distance to excavation is 15.7m, 30 –30 30 30 ﬂoors,frame structure, Distance to excavation is 17.0m, 5 ﬂoors, –35 35 –35 35 and pile foundation. frame structure, and pile foundation. –40 40 –40 40 Support –45 45 –45 45 –50 50 –50 50 –10–5 0 5 10 15 20 25 30 35 40 45 50 55 60 –5 0–105 10 15 20 25 30 35 40 45 50 d (m) d (m)

Estimated surface settlement Estimated surface settlement Monitored building settlement Monitored building settlement (e) (f) d (m) –10 –5 0 5 10 15 20 25 30 35 40 45 0 0 –5 5 –10 10 Excavation –15 15 –20 20 Support –25 25 (mm) Z (m) v –30 Building information: 30 δ Distance to excavation is 13.0m, 5 ﬂoors, –35 35 frame structure, and ra foundation. –40 40 –45 45 –50 50 –10–5 0 5 10 15 20 25 30 35 40 45 d (m)

Estimated surface settlement Monitored building settlement (g)

Figure 14: Building foundation settlements in zone C: (a) Xinzhuang Uptown Station: Building of Nanjing Forestry University; (b) Fenghuangshan Park Station: Commercial Building of Liuhe District; (c) Fenghuangshan Park Station: Residential Building of Water Conservancy Bureau of Liuhe District; (d) Fenghuangshan Park Station: Residential Building of No. 2 Nanjing Lock Factory; (e) Daxinggong Square Station: Chang’an International Building; (f) Longhua Road Station: Residential Building of Agricultural Bank; (g) Longhua Road Station: Dormitory of Tobacco Company.

show the differences between the actual settlements long-side center, and corner 45° direction. *e of pile foundations and the estimated ground surface maximum settlement position of the short side is settlements are large. closer to the diaphragm wall than that of the long side and the corner 45° direction, and the maximum *e above analysis indicates a specific relationship be- settlement positions of the long side and the corner tween the actual settlements of building foundation and the 45° direction are essentially the same. When the estimated ground surface settlements, and the estimated distance of the parallel auxiliary plane to the di- ground surface settlements can be regarded as the building aphragm wall is within 0.5H (approximately 10 m), settlements. However, this estimation method is more re- the ground surface settlements in the parallel aux- liable in strip foundations because raft foundations are iliary plane increase when they cross the excavation conservative. For pile foundations, the ground surface set- corner, and the settlement profile is trough-shaped. tlements are not appropriate for the prediction of settle- When the distance of the parallel auxiliary plane to ments of pile foundations. the diaphragm wall is greater than 0.5H, the ground surface settlements continue to decrease when they 7. Conclusions cross the excavation corner; however, the rates of decrease were lower, and the settlement profile was Based on the numerical simulation and analysis of sur- triangular. *e surface settlement phenomenon in rounding building deformation presented in this paper, the the parallel plane is related to the surface settlement following conclusions may be drawn. profiles in the perpendicular auxiliary plane at dif- (1) For the ground surface settlements, the surface ferent zones around the station excavation. settlement profiles in the perpendicular auxiliary (2) Partitioning of ground surface settlements related to plane are all trough-shaped at the short-side center, the maximum settlement line and settlement turning Advances in Civil Engineering 13

line was proposed according to the three types of Chinese Journal of Geotechnical Engineering, vol. 36, surface settlement profiles at different zones, and the pp. 391–395, 2014, in Chinese. surrounding area of station excavation was divided [6] B. Liu, D. Zhang, and P. Xi, “Numerical analysis of excavation into two parts, namely, the main influence area and effect of unsymmetrical loaded foundation pit with different the secondary influence area. *us, bending de- excavation depths,” Journal of Southeast University (Natural formation and torsional deformation of the sur- Science Edition), vol. 46, no. 4, pp. 853–859, 2016, in Chinese. [7] Y. Zhou, A. Yao, H. Li, and X. Zheng, “Correction of Earth rounding buildings can be easily predicted. pressure and analysis of deformation for double-row piles (3) Settlement data of 21 buildings and the estimated in foundation excavation in Changchun of China,” Ad- ground surface settlements were compared. It was vances in Materials Science Engineering, vol. 2016, Article shown that settlements for a strip foundation were ID 9818160, 10 pages, 2016. consistent with the estimated ground surface set- [8] J. Chen, J.-S. Yang, X.-M. Zhang, and X.-F. Ou, “Numerical tlements, while settlements with raft foundations or analysis and field measurement of force on diaphragm walls in pile foundations were different from the estimated adjacent deep excavations,” Journal of Northeastern Univer- free surface settlements. sity, vol. 38, no. 8, pp. 1189–1194, 2017, in Chinese. [9] C.-Y. Ou, P.-G. Hsieh, and D.-C. Chiou, “Characteristics of (4) It is possible to estimate the ground surface settle- ground surface settlement during excavation,” Canadian ments at different zones around the station exca- Geotechnical Journal, vol. 30, no. 5, pp. 758–767, 1993. vation according to the excavation depth H in order [10] P.-G. Hsieh and C.-Y. 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