Building Deformation Prediction Based on Ground Surface Settlements …downloads.hindawi.com/journals/ace/2018/6050353.pdf · 2019. 7. 30. · settlements at diﬀerent positions

Research ArticleBuilding Deformation Prediction Based on Ground SurfaceSettlements 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 CommonsAttribution License, which permits unrestricted use, distribution, and reproduction in anymedium, provided the original work isproperly cited.

Building deformations are not only closely related to the distance from the building to metro-station excavation but also related tothe relative positions of the building and metro-station excavation. Building deformations can be predicted using ground surfacesettlement profiles. Based on typical geological parameters of Nanjing metro-station excavation, ground surface settlements werenumerically simulated by auxiliary planes perpendicular and parallel to the excavation and by angled auxiliary planes at theexcavation corner. Results show that the ground surface settlement profiles in auxiliary planes are closely related to the relativepositions of the auxiliary planes and the metro-station excavation. Partitioning of ground surface settlements was proposedaccording to the three types of ground surface settlement profiles; furthermore, bending deformation and torsional deformationregularities 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 theapplication of the settlement estimation method to different types of foundations was analyzed. *e results of this study can serveas reference for metro-station deep excavation construction and protection of surrounding buildings.

1. Introduction

Metro-station deep excavations are generally located inbustling areas of a city. *e excavation design should meetnot only the strength and stability requirements of thesupport structure but also the deformation-control re-quirements of the surrounding environment [1]. Soil-massdisplacements around station excavations have complexthree-dimensional (3D) characteristics. However, previousstudies mainly focused on wall deflection and involvedlimited considerations for ground surface settlements[2–8]. Ground surface settlements can be studied throughauxiliary planes perpendicular and parallel to the excava-tion, as well as through angled auxiliary planes at theexcavation corner (Figure 1).

Ground surface settlements in the perpendicular aux-iliary plane have been studied by many scholars but mainlyin the case of two-dimensional (2D) plane-strain states. Forexample, researchers have proposed triangular and trough-shaped ground surface settlement profiles in perpendicular

auxiliary planes [9, 10]. However, few studies have in-vestigated ground surface settlements in the case of 3Dstates, especially ground surface settlements in angledauxiliary planes and in parallel auxiliary planes.

Building deformation around metro-station excavationinvolves geotechnical-structural interaction, making ita cross-disciplinary geotechnical engineering problem. Sonand Cording [11] studied the phenomenon of buildingfailure due to excavation in scaled models of 1 :10 and foundthat cracks in buildings can be classified as “shear + tension,”“convex + stretch,” and “concave + stretch.” *e differentdeformation forms are closely related to the ground surfacesettlement profile; that is, the relative position relationshipbetween the building and excavation determines the de-formation form of the building. *ese conclusions areconsistent with the numerical simulation results reported byZheng and Li [12–14]. In addition, Bryson and Zapata-Medina [15] and Sabzi and Fakher [16] studied buildingdeformations around excavations through field monitoring,theoretical analysis, and numerical simulation.

HindawiAdvances in Civil EngineeringVolume 2018, Article ID 6050353, 14 pageshttps://doi.org/10.1155/2018/6050353

mailto:[email protected]://orcid.org/0000-0002-6119-7594https://creativecommons.org/licenses/by/4.0/https://creativecommons.org/licenses/by/4.0/https://doi.org/10.1155/2018/6050353

Li et al. [17] studied ground surface settlement profiles byanalyzing field-monitoring data of 30 station excavations inthe construction of Nanjing Metro Line 3, Line 10, and LineS8. In the present study, the modified Cam-clay model wasadopted with typical geological parameters in the Nanjingregion, and the 3D characteristics of ground surface set-tlements resulting from station excavation were numericallyanalyzed using FLAC3D. *e numerical simulation in thepresent paper is a supplementary study to the report by Liet al. [17]. Li et al. [17] reported that three types of groundsurface settlement profiles suitable for different zones (zonesA, B, and C) around the excavation were obtained in theconstruction of Nanjing Metro Line 3, Line 10, and Line S8.*e present study conducted further research on buildingdeformations. Partitioning of ground surface settlementswas proposed according to the three types of ground surfacesettlement profiles; then, a prediction method for the type ofbuilding deformation and an estimationmethod for buildingsettlements were developed. Finally, field-monitored dataand estimated settlement values of building settlements werecompared, and the application of the settlement estimationmethod to different types of foundations was discussed.

It should be noted that the three surface settlementprofiles reported by Li et al. [17] were based on the greenfieldground settlement. *us, the greenfield ground settlementwas used to assess the building deformation, and there wasno consideration of the excavation-building interaction.

2. Preparation of Numerical Analysis

2.1. Modeling of Soil Mass. According to Xu et al. [18] andDing et al. [19], the settlement influence range of excavationis generally within 4 times the excavation depth. For soft-soilareas with poor engineering properties, the settlement in-fluence range will not exceed 5 times the excavation depth.Zheng and Jiao [1] showed that the influence range ofbottom uplift of deep excavation is generally 2 times theexcavation depth. Furthermore, the choice of the soil con-stitutive model is very important in numerical analysis.According to analyses of different constitutive models by Ouet al. [20], Potts [21], António et al. [22], and Anthony et al.[23], the modified Cam-clay model is preferred for deep-excavation analysis. To improve the calculation efficiency,

symmetry can be considered in rectangular excavation, andonly one-half or one-quarter model can be used for theanalysis. Boundary conditions were generally set up suchthat the ground surface boundary was a free boundary, thedisplacements of lateral boundaries were constrained in thehorizontal direction, and the displacement of the bottomboundary was constrained in the vertical direction. *einitial stress equilibrium was achieved by applying a gravi-tational field.

In general, the width and depth of the deep excavationsof Nanjing metro stations were approximately 20m, whilethe length was approximately 200m [17]. To improve thecalculation efficiency, the middle part of the deep excavationwas considered to be in a 2D plane-strain state; therefore,appropriate size reduction in the length direction of themodel could meet the analysis requirements. Taking the sizeof the station excavation as 120m × 20m × 20m, the one-half model was established with dimensions of 200m ×150m × 90m, as shown in Figure 2. *e soil mass wasmodeled using 8-node 6-faceted elements.

Nanjing is located in the lower reaches of the Chang Jiangriver, belonging to the Yangtze depression fold belt in geo-tectonic geology.Marine strata, continental strata, andmarine-continental strata of different eras have been alternately de-posited here since the Sinian period. *e ground surfaceconsists mostly of Quaternary alluvial clay overlying Creta-ceous sandstones. Table 1 presents the clay soil parametersused in numerical analysis, which is typical for Nanjing.

2.2. Modeling of Support Structure. *e support structure ofstation excavation is a combination of diaphragm walls andstrutting levels. *e diaphragm walls had a reinforcedconcrete structure with a thickness of 0.8m, the insertionratio of the diaphragm walls was 0.5 (the excavation depth is20m, so the diaphragm wall depth is 30m, 10m of which isunder the excavation bottom, as shown in Figure 3), anda liner lining element was used in the simulation. *e ex-cavation was carried out in 5 steps of 4m each, and 5 layersof horizontal support were built. A structure element beamwas adopted in the simulation.*e 1st layer of strutting levelswas a reinforced concrete beam with a cross section of 0.6m× 0.8m set at the surface; the 2nd to 5th layers of struttinglevels were steel pipe beams of ϕ609, with layer spacings of4m each (Figure 3).

For each layer of strutting levels in the middle of thestation excavation, the beams were supported in parallelwith a spacing of 4m between them. In the corner of thestation excavation, the beams were in the form of bracing,and the spacing between the supporting points was 4m. *eparameters of diaphragm walls and strutting levels are listedin Table 2.

3. Ground Surface Settlements aroundthe Excavation

*ere are two types of ground surface settlement profiles:triangular and trough-shaped [10]. For the cantilever sup-port structure without strutting levels, the ground surface

Angled auxiliary plane

Perpendi

cular au

xiliary p

lane

Parallel auxiliary plane

Support structure

Station excavation

Figure 1: Auxiliary planes around station excavation.

2 Advances in Civil Engineering

settlement profile is generally triangular, while for thesupport structure with strutting levels, the ground surfacesettlement profile is generally trough-shaped. *e study ofground surface settlements mainly focuses on importantparameters such as the maximum settlement value,

maximum settlement position, and influence range of set-tlement. *e ground surface settlements can be analyzedthrough the perpendicular auxiliary plane, parallel auxiliaryplane, and angled auxiliary plane around the station exca-vation (Figure 1).

Table 1: Parameters of the clay soil.

Parameters

Soilgravity

Porosityratio

Poisson’sratio

Lateral pressurecoefficient

Slope of initialconsolidation line

Slope ofexpansion

line

Slope ofcritical state

line

Initialvolumetric

ratio OCRγ

(kN/m3) e μ K0 λ κ M ]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.

Material Young’s modulus,E(GPa)

Poisson’sratio, μ

*ickness, t(m)

Cross-sectional area,A (m2)

Moment ofinertia Polar moment of

inertia, IpIy Iz

Diaphragm walls C30concrete 30 0.20 0.8 — — — —

1st strutting level C30concrete 30 0.20 — 0.48 0.026 0.014 0.040

2nd to 5th struttinglevels

ϕ609steelpipe 206 0.27 — 0.03 0.001 0.001 0.003

60m

20m

200m

90m

150m

20m

Figure 2: Soil-mass model.

Advances in Civil Engineering 3

3.1. Ground Surface Settlements of the Short Side, Long Side,and Excavation Corner at Different Positions. When theexcavation depthH � 20m, the perpendicular auxiliary planesat different positions around the station excavation wereanalyzed to investigate the regularities of ground surfacesettlements at different positions around the station exca-vation, as shown in Figure 4. In the figure, l represents thedistance from the perpendicular auxiliary plane to the ex-cavation corner, and the corner 30° direction auxiliary planeindicates that the plane at the corner is at an angle of 30° withrespect to the perpendicular auxiliary plane l � 0m. A similardefinition applies to the corner 45° direction auxiliary plane.

Figure 4(a) shows the variation regularities of the groundsurface settlements at different positions on the short side. Itcan be observed that the settlements decrease continuouslyfrom the short-side center perpendicular auxiliary plane tothe corner 45° direction auxiliary plane; however, the po-sitions of the maximum ground surface settlements grad-ually shift away from the diaphragm wall.

Figure 4(b) shows the variation regularities of the groundsurface settlements at different positions on the long side. Itcan be observed that when l > 28m, the ground surfacesettlement curves coincide, indicating that this region is inthe 2D plane-strain state. In the process of transition froml � 28m to l � 0m, the ground surface settlements decreasewhile the positions of the maximum surface settlement movecloser to the diaphragm wall to a certain extent owing to 3Deffects. In the process of transition from l � 0m to the corner45° direction, the ground surface settlements decrease fur-ther, but the positions of the maximum settlements movedfarther away from the diaphragm wall, which is essentiallythe same as that of the long-side center perpendicularauxiliary plane without 3D effects.

*e variation regularities of vertical settlements at dif-ferent positions were consistent with the results reported byLi et al. [17].

3.2. Ground Surface Settlements within the Parallel AuxiliaryPlane. Figure 5 shows the variations of ground surfacesettlements in the parallel auxiliary planes around the stationexcavation, where l represents the distance from the parallelauxiliary plane to the diaphragmwall.*e position d � 0m isthemidpoint of the diaphragmwall, while positions d � 10mand d � 60m in Figures 5(a) and 5(b), respectively, corre-spond to the excavation corner.

Consider the parallel auxiliary planes outside the short-side support structure. It can be observed from Figure 5(a)that the ground surface settlements in the parallel auxiliaryplanes at different distances l outside the diaphragm wallexhibit the following characteristics:

(1) During the transition from d � 0m to 10m, theground surface settlement values δv graduallydecrease.

(2) When the parallel auxiliary planes are close to thediaphragm wall (l � 2m, 6m, and 10m), the groundsurface settlement values δv increase for d > 10m(position d � 10m is the excavation corner), and the

ground surface settlement profiles take the trough-shaped form. *e maximum settlement values andthe positions of the maximum settlement values ofthe trough-shaped settlement both decrease withincrease in l.

(3) When the parallel auxiliary planes are far from thediaphragm wall (l > 10m), the ground surface set-tlement values δv do not increase when d > 10m butinstead continue to decrease; the rate of decreaseslows down, and the ground surface settlementprofiles take the triangular form.

Figure 5(b) shows the variations of ground surface set-tlements in the parallel auxiliary planes outside the long-sidesupport structure at different distances from the diaphragmwall, where the position d � 60m is the excavation corner. Onthe two sides of the demarcation plane l � 10m, when d >10m, the ground surface settlements show two types ofprofiles: trough-shaped and triangular. *e settlement trendin the parallel auxiliary planes is related to that in the per-pendicular auxiliary planes around the station excavation.

4. Partitioning of Ground Surface Settlements

Based on the numerical analysis of ground surface settlementsand according to the three settlement profiles in the three typesof zones (zone A, B, and C) around the station excavation [17],partitioning of ground surface settlements was proposed, asshown in Figure 6. *ere are three critical positions of set-tlements outside the diaphragm wall: the maximum settlementline, settlement turning line, and settlement boundary line.*earea within the settlement boundary line is referred to as themain influence area. In this region, the influence of surfacesettlements is significant, and the buildings are subject tosignificant differential settlements. *e area outside the set-tlement boundary line is referred to as the secondary influencearea. In this region, the statistical values of surface settlementsare generally distributed within 0–3mm, and the surfacesettlements have little influences on the buildings. For a deepmetro-station excavation, buildings in the main influence areashould be monitored and protected. Minor settlements mayalso occur in the secondary influence area, but the settlementhazard in this area is negligible.

It can be observed from Figure 6 that there are three typesof zones around the station excavation, namely, zones A, B, andC, and each zone has three critical settlement lines: themaximum settlement line, settlement turning line, and set-tlement boundary line.*e variation regularities are as follows:

(1) Compared to zone A and zone C, the critical set-tlement lines of zone B are considerably short.

(2) *e distances in zone C from the critical settlementlines to the excavation corner are the same as those inzone A; however, the critical settlement lines of zoneC are circular arcs with the excavation corner as thecenter.

(3) *e critical settlement lines of zone B are not thesettlement contour lines, and the settlement valuesdecrease from zone A to zone C. *e critical


settlement lines of other zones can be regarded assettlement contours.

5. Prediction of Building Deformations

*ere are mainly two methods to predict building de-formations due to excavation: the finite element method(FEM) and simplified analysis method (SAM). *e processof FEM is complex and not easily performed by engineers.SAM is used to predict building deformations throughground surface settlements. *is method is simple and easilyapplied in practice [24–26].

Buildings located around the station excavation willinevitably cross the critical settlement lines. *e relativeposition relationship between the building and excavationwill directly affect the building deformations.

Buildings are generally composed of longitudinal walls,inner longitudinal walls, transverse walls, and inner transversewalls. *e deformation regularities of buildings can be ana-lyzed from two aspects, as shown in Figure 7: “bending de-formation of wall” and “torsional deformation of building.”

5.1. Bending Deformation of Wall. Consider the building inzone A. When the building is perpendicular to the

10

–1–2–3–4–5

δ v (m

m) –6–7

–8–9

–10–11–12–13–14–15

–5 0 5 10 15 20 25d (m)

45° direction30° directionl = 0ml = 2m

l = 4ml = 6ml = 8ml = 10m

30 35 40 45 50 55 60 65

(a)

20

–2–4–6–8

–10

δ v (m

m) –12–14

–16–18–20–22–24–26–28–30

45° direction30° directionl = 0ml = 4ml = 8m

l = 12ml = 16ml = 20ml = 24ml = 28m

l = 32ml = 36ml = 50ml = 60m

–5 0 5 10 15 20 25d (m)

30 35 40 45 50 55 60 65

(b)

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

2

0

δ v (m

m)

–2

–4

–6

0 10 20

l = 2ml = 6ml = 10ml = 15m

l = 20ml = 30ml = 40m

30 40d (m)

50 60 70

–8

–10

–12

–14

–16

(a)

l = 2ml = 6ml = 10ml = 15m

l = 20ml = 30ml = 40m

0 20 40 60 80d (m)

100 120

2

0

δ v (m

m)

–2

–4

–6

–8

–10

–12

–14

–16

(b)

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


excavation (α � 90°), the longitudinal walls of the buildingwill exhibit bending deformation. Because the transversewall is parallel to the diaphragm wall without differentialsettlement, there will be no bending deformation. Similarly,when the building is parallel to the excavation (α � 0°), onlythe transverse walls will exhibit bending deformation. Whenthe building and the excavation are at angles in the range of0°< α< 90° in zone A, or when the building is located inzones B or C with 3D effects, longitudinal and transversewalls will cross the critical settlement lines; these longitu-dinal and transverse walls will exhibit bending deformationsimultaneously.

(1) As shown in Figure 8, when the building crosses themaximum settlement line, it will be affected byconcave-bending deformation. Under this condi-tion, the main tensile strain on the longitudinal wallis trough-shaped. Assuming that the building isperpendicular to the diaphragm wall, bending de-formation occurs on the longitudinal wall only.

(2) As the distance from the building to the diaphragmwall d increases, when a part of the building crossesthe maximum settlement line and another partcrosses the settlement turning line, the building willbe affected by both concave-bending deformationand convex-bending deformation. *e main tensilestrain on the longitudinal wall will be trough-shapednear the excavation and crest-shaped away from theexcavation. It can be observed from Figure 8 thatalthough the building exhibits both concave andconvex bending deformations simultaneously, the

deflections of the concave and convex deformationsare small; therefore, the main tensile strains on thewall are not significant.

(3) As the distance from the building to the diaphragmwall d increases further, the building mainly crossesthe settlement turning line. Under this condition, themain tensile strain on the longitudinal wall showsa crest-shaped distribution.

(4) If the distance from the building to the diaphragmwall d increases further, the main tensile strain on thelongitudinal wall will be significantly weakenedowing to the rapid decrease in the surface settle-ments. When the building is located outside thesurface settlement boundary line, it is no longeraffected by bending deformation.

5.2. Torsional Deformation of Building. When the buildingand the excavation are in the range of 0°< α< 90°, the twoparallel longitudinal walls will simultaneously cross thecritical surface settlement lines. Owing to the positions ofsettlements, the critical lines crossing the two walls aredifferent; therefore, in addition to the bending deformationof each wall, the building also exhibits torsionaldeformation.

(1) As shown in Figure 9, when the building crosses themaximum settlement line, the maximum settlementpoint of the back longitudinal wall is located closer tothe front transverse wall than that of the frontlongitudinal wall. Consequently, the building will

Grou

nd su

rface

Statio

n exca

vation

05

1015

2025

3035

4045

50(m)

Zone B

5mm

5mm

10mm

10mm

10mm

30mm

5mm

MZone B

Zone A

Maximumsettlement line

Settlement turning line

Main influence area

M: distance affected by 3-D effects, about 1.5 timesthe excavation depth and 1/10 of the excavation length.

Secondary influence area

Settlement boundary line

10mm

25mm

25mm

0 5 10 15 20253035 4045 50

0 5 10 15 20253035 4045 50

05 10 15 20 25 3035 4045 50

(m)

(m)

(m)

Zone C

2.5mm

Figure 6: Partitioning of ground surface settlements.


exhibit torsional deformation. *e direction of thetorsional deformation of the front longitudinal wallis clockwise, while that of the back longitudinal wallis counterclockwise. Because the left side of the fronttransverse wall is closer to the maximum settlementline than the right side, the front transverse wallexhibits counterclockwise rotation. In contrast, theback transverse wall exhibits clockwise rotation sincethe right side of the back transverse wall is closer tothe maximum settlement line than the left side. Notethat the clockwise direction, counterclockwise di-rection, left side, and right side in this context are therelative position relationships when the observerfaces the facade.

(2) As shown in Figure 10, when the building crosses thesettlement turning line, the settlement turning pointof the back longitudinal wall is located closer to thefront transverse wall than that of the front longi-tudinal wall. Consequently, the building will exhibittorsional deformation. *e direction of torsionaldeformation of the front longitudinal wall is coun-terclockwise, while that of the back longitudinal wallis clockwise. Because the left side of the fronttransverse wall is closer to the settlement turning linethan the right side, the front transverse wall exhibits

clockwise rotation. In contrast, the back transversewall exhibits counterclockwise rotation since theright side of the back transverse wall is closer to thesettlement turning line than the left side.

(3) Similar analysis can be carried out for the arc-shapedcritical settlement lines in zone C, as shown in Fig-ure 11. It can be concluded that the front longitudinalwall exhibits counterclockwise rotation, the back lon-gitudinal wall exhibits clockwise rotation, the fronttransverse wall exhibits clockwise rotation, and the backtransverse wall exhibits counterclockwise rotation.

*e above analysis of the longitudinal and transversewalls can be carried out for the inner longitudinal andtransverse walls. *e analysis above indicates that whenα � 0°, 90° or the center symmetrical line of the building inzone C passes through the excavation corner, the positionsof the critical settlement line through the parallel walls arethe same. Consequently, the walls only exhibit bendingdeformation and do not exhibit torsional deformation.

6. Estimation of Building Settlements

According to Li et al. [17], the maximum surface settlementsδVm can be directly estimated from the excavation depth H;

Supportstructure

Maximumsettlement point

Settlementturning point

Settlementboundary point

Station excavation

d: Vertical distance of wall to excavation

d m

m

d

d

mTransverse wall: m = bcosαLongitudinal wall: m = asinα

a: length of longitudinal wallb: length of transverse wall

Figure 8: Bending deformation of a wall.

Transverse wall

d α

Inner transverse wall

Front wall

Inner longitudinal wall

Longitudinal wall

Settlement turning lineMaximum settlement line

Support structureStation excavation

Back wall

Figure 7: Building around the station excavation.


then, the ground surface settlements at different zones can beestimated through the ground surface settlement profiles.*e ground surface settlements in different zones areregarded as the settlements of the building foundation.*erefore, the building settlements at different zones aroundthe metro-station excavation can be estimated.

However, the ground surface settlements and buildingsettlements may not be completely consistent with eachother. *e relationship between building settlements andground surface settlements should be further investigated.

In this section, 21 buildings around the station exca-vations were selected for field monitoring. *e surroundingsof the station excavation were divided into three differentzones, namely, zones A, B, and C, and there were sevenbuildings in each zone. *e building structures include thecommonly used brick-concrete structure and the framestructure, and the type of foundations mostly includes thestrip foundation, raft foundation, and pile foundation. *emeasured settlement values of the building foundations were

compared with the estimated free surface settlement values,as shown in Figures 12–14.

*e regularities between the actual foundation settle-ments and the estimated ground surface settlements aresummarized 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,although there are deviations between the measuredsettlement values of the strip foundation and theestimated values of the ground surface settlements,the trend is essentially the same. It should be notedthat because the strip foundation itself has a certainresistance capacity to deformation, the actual settle-ment profile of the building foundation at the max-imum settlement position of the surface settlementprofile will not indicate a sharp angle but will rather berelatively smooth at the maximum settlement.

(2) *e raft foundation has greater integral rigidity thanthe strip foundation, which is helpful to adjust theuneven settlement of the foundation. It can be ob-served from Figures 12(g), 13(g), and 14(g) that theactual settlement values of the raft foundations aregenerally smaller than the estimated ground surfacesettlements, and it is a conservative estimation toconsider the ground surface settlements as thebuilding foundation settlements.

(3) Pile foundation is a type of deep foundation com-monly used in high-rise buildings. *e main ob-jective of using a pile is to utilize its own stiffnessmuch more than that of the soil and to transfer theupper structure load to the hard soil or rock aroundthe pile to reduce structure settlements. *erefore,settlements of deep soil mass at the pile bottom candirectly affect the pile foundation, while the influenceof ground surface settlements on the pile foundationis relatively small. *is can be verified as shown inFigures 12(e), 12(f ), 14(e), and 14(f). *e figures

Stationexcavation

mm

d2

d1


Building

Settlementturning line

Figure 9: Torsional deformation of a building across the maximumsettlement line.

Stationexcavation

mm

d2

d1


Building


Figure 10: Torsional deformation of a building across the settle-ment turning line.

Stationexcavation m

m

d2d1

Maximumsettlementline

Building


Figure 11: Torsional deformation of a building located outside theexcavation corner.


–100

–5

Excavation

SupportBuilding information:

Distance to excavation is 8.6m, 6 floors,brick-concrete structure, and strip foundation.

–10–15–20–25–30–35

Z (m

)

–40–45–50

05101520253035

δ v (m

m)

404550

0

Estimated surface settlementMonitored building settlement

–10 5 10 15 20 25 30 35 40 45 50

–5

–5

0 5 10 15 20d (m)

d (m)

25 30 35 40 45 50

(a)

–100

–5 Excavation

Support

Building information:Distance to excavation is 11.4m, 7 floors,

brick-concrete structure, and strip foundation.

–10–15–20–25–30–35

Z (m

)

–40–45–50

05101520253035

δ v (m

m)

404550

0


–10 5 10 15 20 25 30 35 40 45 50

–5

–5

0 5 10 15 20d (m)

d (m)

25 30 35 40 45 50

(b)

–100

–5 Excavation

Support



–10–15–20–25–30–35

Z (m

)

–40–45–50

05101520253035

δ v (m

m)

404550

0


–10 5 10 15 20 25 30 35 40 45 50

–5

–5

0 5 10 15 20d (m)

d (m)

25 30 35 40 45 50

(c)

d (m)

–10 –5 0 5 10 15 20d (m)

25 30 35 40

–10 –5 0 5 10 15 20 25 30 35 40

0–5

–10–15–20–25–30–35

Z (m

)–40–45–50

Excavation

Support

05101520253035

δ v (m

m)

404550


frame structure, and strip foundation.


(d)

d (m)

–10 –5 0 5 10 15 20d (m)

25 30 35 6040 45 50 55

–10 –5 0 5 10 15 20 25 30 35 6040 45 50 55

0–5

–10–15–20–25–30–35

Z (m

)

–40–45–50

Excavation

Support

05101520253035

δ v (m

m)

404550


frame structure, and pile foundation.


(e)

d (m)

–10 –5 0 5 10 15 20d (m)

25 30 35 6040 45 50 55

–10 –5 0 5 10 15 20 25 30 35 6040 45 50 55

0–5

–10–15–20–25–30–35

Z (m

)

–40–45–50

05101520253035

δ v (m

m)

404550


frame structure, and pile foundation.


(f )

d (m)

–10 –5 0 5 10 15 20d (m)

25 30 35 4540

–10 –5 0 5 10 15 20 25 30 35 4540

0–5

–10–15–20–25–30–35

Z (m

)

–40–45–50

Excavation

Support

05101520253035

δ v (m

m)

404550


frame structure, and ra� foundation.


(g)

Figure 12: Building foundation settlements in zone A: (a) Xiaoshi Uptown Station: Shop Building; (b) Wuding Gate Station: SecurityBusiness 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 –5 0 5 10 15 20d (m)

d (m)

25 30 35 40 45

–10 –5 0 5 10 15 20 25 30 35 40 45

0–5

–10–15–20–25–30–35

Z (m

)

–40–45–50

Excavation

Support

05101520253035

δ v (m

m)

404550




(a)

d (m)

–10 –5 0 5 10 15 20d (m)

25 30 35 40

–10 –5 0 5 10 15 20 25 30 35 40

0–5

–10–15–20–25–30–35

Z (m

)

–40–45–50

Excavation

Support

05101520253035

δ v (m

m)

404550




(b)

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

–10 –5 0 5 10 15 20d (m)

25 30 35 40 45 500

–5–10–15–20–25–30–35

Z (m

)

–40–45–50

Excavation

Support

05101520253035

δ v (m

m)

404550




(c)

d (m)

–10 –5 0 5 10 15 20d (m)

25 30 35 4540

–10 –5 0 5 10 15 20 25 30 35 4540

0–5

–10–15–20–25–30–35

Z (m

)

–40–45–50

Excavation

Support

05101520253035

δ v (m

m)

404550




(d)

d (m)–10 –5 0 5 10 15 20 25 30 35 40 45

–10 –5 0 5 10 15 20d (m)

25 30 35 40 450

–5–10–15–20–25–30–35

Z (m

)

–40–45–50

Excavation

Support

05101520253035

δ v (m

m)

404550




(e)

d (m)

–10 –5 0 5 10 15 20d (m)

25 30 35 6040 45 50 55

–10 –5 0 5 10 15 20 25 30 35 6040 45 50 55

0–5

–10–15–20–25–30–35

Z (m

)

–40–45–50

Excavation

Support

05101520253035

δ v (m

m)

404550




(f )

Figure 13: Continued.


d (m)

–10 –5 0 5 10 15 20d (m)

25 30 35 40 5045

–10 –5 0 5 10 15 20 25 30 35 40 5045

0–5

–10–15–20–25–30–35

Z (m

)

–40–45–50

Excavation

Support

05101520253035

δ v (m

m)

404550

Building information:Distance to excavation is 8.3m, 7 floors,frame structure, and strip foundation.


(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.

–100

–5

Excavation

Support



–10–15–20–25–30–35

Z (m

)

–40–45–50

05101520253035

δ v (m

m)

404550

0


–10 5 10 15 20 25 30 35 40 45 50

–5

–5

0 5 10 15 20d (m)

d (m)

25 30 35 40 45 50

(a)

Excavation


Distance to excavation is 10.0m, 3 floors,brick-concrete structure, and strip foundation.

0–5

–10–15–20–25–30–35

Z (m

)

–40–45–50

05101520253035

δ v (m

m)

404550

0–10 5 10 15 20 25 30 35 40 45–5


d (m)

–10 –5 0 5 10 15 20d (m)

25 30 35 40 45

(b)

Excavation

Support



0–5

–10–15–20–25–30–35

Z (m

)

–40–45–50

δ v (m

m)

05101520253035404550

–5 0


–10 5 10 15 20 25 30 35 40 45 50d (m)

–10 –5 0 5 10 15 20d (m)

25 30 35 40 45 50

(c)

Excavation

Support



0–5

–10–15–20–25–30–35

Z (m

)

–40–45–50

δ v (m

m)

05101520253035404550

0–10 5 10 15 20 25 30 35 40 45–5


d (m)

–10 –5 0 5 10 15 20d (m)

25 30 35 40 45

(d)

Figure 14: Continued.


show the differences between the actual settlementsof pile foundations and the estimated ground surfacesettlements are large.

*e above analysis indicates a specific relationship be-tween the actual settlements of building foundation and theestimated ground surface settlements, and the estimatedground surface settlements can be regarded as the buildingsettlements. However, this estimation method is more re-liable in strip foundations because raft foundations areconservative. For pile foundations, the ground surface set-tlements are not appropriate for the prediction of settle-ments of pile foundations.

7. Conclusions

Based on the numerical simulation and analysis of sur-rounding building deformation presented in this paper, thefollowing conclusions may be drawn.

(1) For the ground surface settlements, the surfacesettlement profiles in the perpendicular auxiliaryplane are all trough-shaped at the short-side center,

long-side center, and corner 45° direction. *emaximum settlement position of the short side iscloser to the diaphragm wall than that of the longside and the corner 45° direction, and the maximumsettlement positions of the long side and the corner45° direction are essentially the same. When thedistance of the parallel auxiliary plane to the di-aphragm wall is within 0.5H (approximately 10m),the ground surface settlements in the parallel aux-iliary plane increase when they cross the excavationcorner, and the settlement profile is trough-shaped.When the distance of the parallel auxiliary plane tothe diaphragm wall is greater than 0.5H, the groundsurface settlements continue to decrease when theycross the excavation corner; however, the rates ofdecrease were lower, and the settlement profile wastriangular. *e surface settlement phenomenon inthe parallel plane is related to the surface settlementprofiles in the perpendicular auxiliary plane at dif-ferent zones around the station excavation.

(2) Partitioning of ground surface settlements related tothe maximum settlement line and settlement turning

Excavation

Support

Building information:Distance to excavation is 15.7m,

30 floors,frame structure,and pile foundation.

0–5

–10–15–20–25–30–35

Z (m

)

–40–45–50

δ v (m

m)

05101520253035404550

–5 0


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

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

(e)

Excavation


Distance to excavation is 17.0m, 5 floors,frame structure, and pile foundation.

0–5

–10–15–20–25–30–35

Z (m

)

–40–45–50

δ v (m

m)

05101520253035404550

0–10 5 10 15 20 25 30 35 40 45 50–5


d (m)

–10 –5 0 5 10 15 20d (m)

25 30 35 40 45 50

(f )

Excavation

Support


frame structure, and ra� foundation.

0–5

–10–15–20–25–30–35

Z (m

)

–40–45–50

δ v (m

m)

05101520253035404550

–5 0


–10 5 10 15 20 25 30 35 40 45d (m)

d (m)–10 –5 0 5 10 15 20 25 30 35 40 45

(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 WaterConservancy Bureau of Liuhe District; (d) Fenghuangshan Park Station: Residential Building of No. 2 Nanjing Lock Factory; (e) DaxinggongSquare Station: Chang’an International Building; (f ) Longhua Road Station: Residential Building of Agricultural Bank; (g) Longhua RoadStation: Dormitory of Tobacco Company.


line was proposed according to the three types ofsurface settlement profiles at different zones, and thesurrounding area of station excavation was dividedinto two parts, namely, the main influence area andthe secondary influence area. *us, bending de-formation and torsional deformation of the sur-rounding buildings can be easily predicted.

(3) Settlement data of 21 buildings and the estimatedground surface settlements were compared. It wasshown that settlements for a strip foundation wereconsistent with the estimated ground surface set-tlements, while settlements with raft foundations orpile foundations were different from the estimatedfree surface settlements.

(4) It is possible to estimate the ground surface settle-ments at different zones around the station exca-vation according to the excavation depth H in orderto determine the settlements of the strip foundationstructure. *e main processes are as follows. First,the maximum settlement value δVm of ground sur-face settlements is estimated from the excavationdepth H according to the ratios H/δVm. Second, thegreenfield-condition settlements at different zonesaround the station excavation are determinedaccording to H, δVm, and three surface settlementprofiles. *ird, the ground surface settlements areregarded as the settlements of the building foun-dation, and the settlement values of the building arethen determined.

Data Availability

*e data used to support the findings of this study areavailable from the corresponding author upon request.

Conflicts of Interest

*e authors declare that there are no conflicts of interestregarding the publication of this manuscript.

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