Abstract
According to the deep foundation pit project of Xiaoxihu station on Lanzhou subway Line 1, the three-dimensional finite-element model of the half-cover excavation method of retaining structure is established to simulate the construction of the excavation of the foundation pit. This article analyzes the settling of the surrounding surface, the horizontal displacement and vertical displacement of the retaining pile, the vertical displacement of the shoring column, and the change of the axial force of the inner support and compares them with the actual monitoring data. The results show that for the collapsible loess strata in Lanzhou, the design of retaining pile and inner support is viable. The support form has a good control effect on the deformation of the foundation pit. It keeps the foundation pit stable. The numerical simulation results are more consistent with the actual monitoring data. It provides a basis for the scientific design and construction of a deep foundation pit in the Lanzhou metro station.
1 Introduction
In the context of the city’s rapid economic development, the space on the ground is gradually saturated and crowded. It is particularly important to develop underground space. The subway can make full use of underground space to solve urban congestion problems, and the construction of the subway becomes the focus of underground space development. Subway stations are usually built in urban areas with dense buildings and large populations. Pit excavation space is restricted, and the underground soil layer and pipeline are complex. Ensure that the pit is safe and operational, and also consider the impact on the surrounding environment. Compared with other forms [1], the retaining pile and inner support forms provide excellent support and reduce disturbance to the surrounding soil environment. It has an important contribution to reducing underground space pollution and sustainable development. Ye et al. [2,3] studied the deformation analysis and safety evaluation of pit excavation on existing subway tunnels. In addition, they proposed a model and calculation method for lateral unloading loading of tunnel tubes to solve the problem of the impact of pit excavation on adjacent shield tunnel tubes and anchors. Wu et al. [4] investigated the reasonableness of the support design of drilled piles and prestressed anchor cable support combined with concrete corner stiffener under complex pit surroundings, dense building areas, complex subsurface soils, and groundwater effect. Ye and Li [5] explored the effective control of the deformation of neighboring buildings by using the support structure of “bitted piles + prestressed anchors” and the local use of soil nail wall deep and large foundation pit support structure. Because the deformation analysis experiment of braced excavation is difficult, the numerical simulation analysis software has become an approach studying geotechnical engineering problems [6,7]. The selection and parameter analysis of the foundation pit brace model is an important step in the numerical analysis [8,9,10]. Many researchers have also studied the complex foundation pit with complicated geological conditions [11,12,13]. The foundation pit support is influenced by the site. The same support form is distinct in different soil layers, and its deformation law and influencing factors differ. Many researchers are competing to study the deformation and stress of support forms in clay areas [14,15], soft soil areas [16,17], or other collapsible loess areas [18]. Here are a few research studies on retaining pile and inner support forms for collapsible loess strata in the Lanzhou area.
Taking the Xiaoxihu Station of Lanzhou Urban Rail Transit Line 1 as an example, this article studies the half-cover excavation pits of the retaining pile and inner support form of the collapsible loess layer in the Lanzhou area. According to the actual excavation conditions, a three-dimensional finite-element model is built to analyze the deformation law of the retaining structure and the surrounding ground settlement. Based on comparison with actual surveillance data, it was found that the retaining wall and internally supported forms in the Lanzhou area can effectively control the deformation within the subway foundation pit support.
2 Engineering overview
2.1 Station overview
Xiaoxihu station, the middle station of the first phase of Lanzhou Urban Rail Transit Line 1, is located in the east of the small West Lake flyover in Qilihe District. The station is laid along the east–west direction of Xijin East Road. The total length of the foundation pit is 203.60 m, the net width of the standard section is 22.20 m, and the depth of the foundation pit is 17.67–18.20 m. It is an island station.
2.2 Engineering geological conditions
The geographic environment of the proposed site belongs to category II. It is located in VIII of seismic fortification intensity, and the third group is the design earthquake group. The groundwater level is buried at 7.20–9.20 m, which is a submersible type. The 2-10 and the 3-11 pebble layers are the main aquifers of the station. The site is a class I area in the Yellow River. The subway passes through the stratum mainly as a pebble layer, and the upper layer covers collapsible loess and silt. From the engineering geological investigation report, the stratigraphy is distributed in the following order from top to bottom: Quaternary Holocene Q4 (1-2) plain fill, Q4 (2-1) loess, Q4 (2-4) silt, Q4 (2-10) pebble, and Quaternary lower Pleistocene Q1 (3-11) pebble. The main mechanical parameters of the top cover are given in Table 1.
Physical and mechanical indices of soils
| Number | Name | Unit weight γ (kN m−3) | Cohesion c (kPa) | Inner friction angle φ (°) | Permeability coefficient (m/d) |
|---|---|---|---|---|---|
| 1-2 | Plain fill | 18.4 | 19 | 18.0 | — |
| 2-2 | Loess | 16.6 | 16 | 24.0 | — |
| 2-4 | Silt | 18.2 | 14 | 24.0 | 25.8 |
| 2-10 | Pebble | 23.0 | 0 | 40.0 | 25.8 |
| 3-11 | Pebble | 23.5 | 0 | 42.0 | 25.8 |
2.3 Foundation pit support scheme
The south side of the station is covered by a half-width cover to traffic congestion. The support construction of the foundation pit takes the shape of a bored pile and concrete/steel pipes column, and the whole foundation pit is split into four excavations. The body of the station is made of 800 mm diameter 1,400 mm cast-in-place piles, and the east and west shields are made of 1,500 mm diameter 1,800 mm cast-in-place piles. The pile spacing is slightly adjusted in some sections. All cast-in piles are made of C30 concrete. Between the piles is a concrete mesh surface. An 800 mm × 800 mm reinforced concrete crown beam is placed at the head of each pile. Along the foundation pit, there is vertical arrangement of three inner supports; the first one uses 800 mm × 800 mm reinforced concrete with a horizontal spacing of 6.0 m and is supported on the crown beam. The second and third use 609 mm × 16 mm steel pipe support with a horizontal spacing of 2.5–3.5 m and are supported on the steel purlin. The steel purlin adopts two H-type 45b combined steels. Figure 1 illustrates a cross-section of the pit support. Figure 2 depicts the actual construction.
Section of support for foundation pit.
Pictures of site construction.
2.4 Monitoring scheme and monitoring point layout
The station foundation pit monitoring project includes monitoring horizontal and vertical displacement in the pile body, the vertical displacement of the temporary column top, the inner support axis force, and the settlement displacement of the surrounding surface. Among them, DB1-4 is the monitoring point of surface settlement (bulge), LZ1-6 is the monitoring point of temporary column displacement, ZQ1-2 is the monitoring of pile displacement, and ZL1-4 is the monitoring of internal brace axial force. The layout and surrounding environment of each monitoring point are shown in Figure 3.
Layout of the foundation pit monitoring plane.
3 Establishment of the finite element model
The whole process simulation of the foundation pit excavation was produced using PLAXIS 3D (2020) software. The station lowered the aquifer depth below the base of the foundation pit before excavation, and numerical simulations were performed without considering the effect of groundwater on the simulation results. The soil body adopts the Mohr–Coulomb constitutive model. The foundation pit retaining structure is a cast-in-place pile of net spray concrete. The single pile unit cannot accurately simulate the working condition of the foundation pit retaining structure. Therefore, the plate element is used to keep the stress of the pile equivalent. According to the equivalent stiffness theory calculation method of PLAXIS 3D Basic Tutorial, the pile body is equivalent to a slab for calculation, and the thickness of the grouted pile is converted to a slab unit for calculation through
Model parameter value table
| Model name | Elasticity modulus E (kN m−2) | Unit weight γ (kN m−3) | Poisson’s ratio υ (kN m−2) |
|---|---|---|---|
| Equivalent retaining pile | 3 × 107 | 25 | 0.2 |
| Temporary column | 3 × 107 | 25 | 0.2 |
| Crown beam | 3 × 107 | 25 | 0.2 |
| Waist beam | 2.06 × 108 | 78.5 | 0.3 |
| Continuous beam | 3 × 107 | 25 | 0.2 |
| Concrete support | 3 × 107 | 25 | 0.2 |
| Steel support | 2.06 × 108 | 78.5 | 0.3 |
Pit excavation construction conditions
| Working condition | Contents of construction | Excavation depth (m) |
|---|---|---|
| 0 | Initial geostress equilibrium | 0 |
| 1 | Perimeter pile construction | 0 |
| 2 | Excavation of the first layer of soil in the pit and setting of the first support | −5.6 |
| 3 | Excavation of the second layer of soil in the pit and setting of the second support | −11.6 |
| 4 | Excavation of the third layer of soil in the pit and setting of the third support | −16.12 |
| 5 | Soil excavation to the bottom of the pit | −21.62 |
Calculation analysis mode.
Foundation pit enclosure structure mode.
4 Analysis of simulation results
4.1 Analysis of the surrounding ground settlement
The model cloud diagram of total model vertical displacement is shown in Figure 6. The surrounding surface settlement curve is shown in Figures 7 and 8. This article takes DB1, DB2, and DB3 near the high-rise residential building in the middle of the foundation pit and takes DB5, DB6, and DB7 on the end of the foundation pit.
After the first excavation, the surrounding points gradually settled downward, and the maximum settlement was 4 mm.
After laying the retaining pile and constructing the first concrete inner support, inner support plays a good role in the surrounding soil. The downward displacement of surrounding ground has a rising trend. Part of the surface changes from settlement to bulging.
During the second excavation, the passive earth pressure in the building pit gradually decreased as the excavation depth increased. The force exerted by the first inner column on the building pit retaining structure is insufficient. The surrounding soil gradually sinks, which eventually forms a larger settlement deformation than the first excavation.
When installing the second steel pipe inner support and applying 660 kN of prestressing force. The vertical deformation of the surrounding soil was controlled and the curve trend stabilized.
For the third excavation, the previous inner supports have provided good support. At this time, the surrounding soil deformation is small, which is optimized compared with the last two excavations.
Apply the inside support of the third steel tube and apply a prestress of 600 kN. The force is continuously applied under the condition that soil deformation is controlled, and the surrounding soil has a small degree of bulging compared with the previous deformation amount.
In the last excavation, soil settlement outside the pit showed an upward trend and stabilized. Surface subsidence tendencies at the two ends are roughly the same but slightly different due to the influence of surrounding buildings, human activities, and road traffic. In accordance with GB 50497-2019 Technical Standards for the Supervision of Excavation Pit Works, the cumulative value of settlement of the roadbed of neighboring roads is within 20–40 mm, and the total settlement is controlled within the maximum settlement range.
Model cloud diagram of vertical displacement of the overall model.
Surface settlement chart is the middle of the foundation pit.
Surface settlement chart on the end of the foundation pit.
4.2 Horizontal displacement analysis of pile body
The model cloud diagram of total pile displacement is shown in Figure 9. A model cloud diagram of horizontal pile displacement in the center of the excavation is shown in Figure 10. Horizontal displacement curves at 2, 6, 10, and 14 m of two retaining piles, ZQ1 in the midst of the foundation pit and ZQ2 at the end of the foundation pit, are shown in Figures 11 and 12. With increasing excavation depth, the total transverse deformation of the pile body is progressively greater, and the small part of the deformation shows a shrinking trend.
After installing the first concrete inner support, the horizontal deformation trend of the pile body is effectively controlled and no longer increases.
After the second construction of the foundation pit, the deformation of the pile was increased, and the deformation amount was two to three times that of the first excavation.
After installing the second steel support and applying prestress, the deformation of the pile body gradually stops in the initial stage and then begins to compress outside the pit. At 10 and 14 m, due to the deep buried pit soil, the displacement change trend is slower. At 2 and 6 m, the displacement changes sharply due to the short distance from the steel support.
With the installation of the third steel support, the lateral deformation of the pile body appears a tendency to suspend development. When the prestress acts, the pile appears to be displaced outside the pit. Specifically at 10 m, due to the closer distance to the third inner support, the displacement retraction is obvious.
Model cloud diagram of the total displacement of the pile.
Model cloud diagram of horizontal displacement of the pile in the middle of the foundation pit.
Horizontal displacement graph of ZQ1 pile.
Horizontal displacement graph of ZQ2 pile.
Due to the multi-layer inner support form, the top of the cast-in-place pile has the smallest displacement, the bottom is the second, the middle is the largest, and the position at the inner support shrinks sharply. The overall trends in horizontal displacement of both piles are similar and strongly linked to the construction circumstances. The ZQ1 piles ranged from 10 to 14 m in maximum horizontal displacement. The ZQ2 piles ranged from 6 to 10 m in maximum horizontal displacement. The end of the foundation pit is more dangerous than the middle part of the foundation pit. The overall horizontal displacement of the upper part of ZQ2 is greater than ZQ1. Specifically at 6 m, the deformation displacement is the largest, and only the displacement of the bottom of the pile is close. According to GB 50497-2019 Technical Standards for Monitoring of Construction Pit Engineering, it can be known that the warning line of the cumulative value of deep horizontal displacement of the grouted piles with a pit design safety grade of 2 is in the range of 40–60 mm. Therefore, it can be judged that the whole structure is safe. Therefore, in designing and monitoring foundation pits, we should pay attention to the center section of the support pile at the end of the excavation.
4.3 Vertical displacement analysis of pile body
The vertical displacement curves of ZQ1 and ZQ2 piles at 0, 2, 6, 10, and 14 m are shown in Figures 13 and 14. The overall curve trend is gradually sinking. When the inner support is added for the first time, there is an upward bulging trend at the lower end of the pile at 10 and 14 m. The deformity of the pile body at 0 m is slightly less than 2 m. The maximum displacement occurs at 2 m of the pile and gradually decreases downward along the pile. The vertical deformity curves of the two piles are the same. No matter where the retaining pile is located, it has less influence on the vertical deformity of the pile.
Vertical displacement graph of ZQ1 pile.
Vertical displacement graph of ZQ2 pile.
The vertical deformity curve of the pile body is similar to the overall trend of the surrounding surface settlement. The upward displacement point corresponds to the added inner support condition, and the downward displacement point corresponds to the foundation pit excavation conditions. Due to the long-term constant load and live load on the surrounding surface, the soil has a high degree of consolidation. The disturbance caused by the digging of the foundation pit is less affected. As the main support structure of the foundation pit, the retaining pile bears the road load and the soil pressure behind the pile, and its deformation degree is much larger than the surrounding surface settlement.
4.4 Vertical displacement analysis of temporary column
In contrast to the open-cut method, the half-cover-cut method also includes a temporary upper roadway and temporary columns in the middle of the pit. The column not only supports the load from the upper road surface but also bears the pressure caused by the vertical deformation of the inner support. A coupling beam system is used between the columns, and the three layers of inner support are placed on the coupling beam. It is able to effectively control the vertical deformation of the middle part of the inner support and enhance the inner support stability.
The vertical displacement graph of the temporary column is shown in Figures 15 and 16. The temporary columns LZ1, LZ2, and LZ3 are located in the center of the pit, and LZ4, LZ5, and LZ6 are at the end of the foundation pit. Where a small amount of soil is removed, the stress of soil in the pit is released, and a small uplift tendency is formed, which causes upward-side resistance to the upper column and makes the column uplift upward. The uplift trend causes side resistance between the lower part of the column and the soil, which prevents the column from rising upward. After the internal support is installed, the deformation of the retaining pile and soil beyond the pile is effectively controlled. The uplifting trend of the pit bottom is weakened. The vertical displacement of the column is retracted. With increasing excavation depth, most of the soil in the hole is gone, and the upward bulging trend is more and more intense. Simultaneously, because the interface between the column and the ground is reduced, the downward frictional force of the lower part of the column is reduced, and the uplift of the column should be more obvious. However, since the foundation pit mainly passes through the pebble soil layer, the pebble compressive strength is high, and the degree of uplift is less obvious. Therefore, the curve of the vertical displacement of the column fluctuates upwards and down with the working condition near 0. The displacement of the end of the foundation pit is slightly larger than the middle of the foundation pit, but the overall trend is consistent, which is closely linked to the conditions of the construction site.
Vertical displacement graph of a temporary column in the middle of the foundation pit.
Vertical displacement graph of a temporary column at the end of the foundation pit.
4.5 Axial force analysis of inner support
The model cloud diagram of the axial force of the concrete inner support is shown in Figure 17. The axial force variation curve of the concrete support is shown in Figure 18. Take the inner support ZL1 and ZL2 in the middle of the foundation pit, and ZL3 and ZL4 at the end of the foundation pit. Before installing the first layer of inner support, the data are taken 0. After the second excavation of the foundation pit, axial force increased significantly. After the second steel support is applied and prestressed, the axial force tends to decrease as it shares the first layer of inner support pressure. In particular, the inclined support at either end of the pit has a large axial force that is reduced to near zero. Its axial force of the foundation is greatly reduced to nearly 0 points. Excavate the soil again and construct a third inner support. At this time, because the distance from the first pillar is large, the middle support of the foundation pit is slightly affected and tends to be stable. However, the axial force at both ends of the foundation pit has many sudden changes. Because the excavation area on either end of the foundation pit is large, the number of supports is small, the length is not uniform, and the force placed at the oblique angle is inferior to the middle support, the axial force of the ZL1 and ZL2 in the middle is much smaller than that of the ZL3 and ZL4 at the end. The axial force of ZL1 and ZL2 develops slowly during the digging of the foundation pit, and the degree of change is not high. The overall trend of the curve is smoother. The axial force of ZL3 and ZL4 develops rapidly in the digging process, and the degree of abrupt change is high. After supporting the construction, the axial force reduction trend is also very rapid, and the reduction is huge. It is clear that during the digging of the foundation pit, the axial force at both ends of the foundation pit changes significantly and rapidly. There is a large adverse effect on internal internal support. Focusing on the impact of sudden changes in the axial force on the inner support during design and post-monitoring is necessary.
Model cloud diagram of axial force of concrete inner support.
Axial force graph of concrete inner supporting.
5 Comparative analysis of monitoring data and simulation results
5.1 Comparative analysis of surrounding surface settlement
The surface settlement around the pit after completion of the excavation was significant. Therefore, the monitoring data of DB4, DB5, and DB7 are compared to the simulation results. The curve is shown in Figure 19. At point DB4, south of the central part of the pit, and at point DB5, closer to the pit, westward of the end of the pit, monitoring data and modeling results are in good agreement. Specifically in the late stage of pit excavation, the curves are the same. DB7 is far from the foundation pit, and the observation results have slightly deviated from the simulation results. The numerical simulation settlement results slightly rebound in the later stage. The reason is that the excavation process at the near point of the foundation pit greatly influences deformation, so the numerical simulation results are closer to the reality of the situation. The effect of other extraneous factors at the far point is strengthened, such as a man-made vehicle, and space–time effect, which cannot be reflected in the simulation calculation. So, the simulation data have a certain deviation from the measured data. However, the general trend is essentially the same. It shows that selecting models, loads, parameters, and calculation methods is reasonable and feasible in three-dimensional finite-element simulation.
Comparison curve of surface subsidence monitoring and calculation value.
5.2 Comparative analysis of vertical deformation of pile body
The correlation curves between the observation data and the calculation results of the vertical deformation of the piles of the ZQ1 pile at 2, 6, and 10 m are shown in Figure 20. The simulation data have more calculation steps and do not consider all the uncertain factors; the curve is smoother, and the deformation trend is obvious. The monitoring data have less value and more external interference factors, and the curve has many displacement points. There is some deviation between simulated and measured data, but the overall trend is consistent. Further explanation of the three-dimensional finite-element software simulation is reasonable and feasible.
Comparison curve of ZQ1 pile: (a) at 2 m, (b) at 6 m, and (c) at 10 m.
6 Conclusions
This article simulates the working conditions of the excavation of the underground station excavation pit in the form of retaining wall piles and internal support in the Lanzhou area and analyses it through numerical simulation compared with actual observation data. The conclusions are as follows:
Based on the analysis of simulation data of pit excavation, the shifting of the pile body and the subsidence of the surrounding soil are all within the allowable range of the design. The retaining pile + concrete/steel inner support foundation pit support form good control of pit deformation in the collapsible loess layer in the Lanzhou area.
The provisional pillar in the middle of the foundation pit is subjected to two forces: One is that the excavated soil has an upward lateral resistance to the upper part of the column, which causes a tendency to uplift; and the other is that the uplift trend causes a downward side resistance between the lower part of the column and soil, which causes a tendency to settle. The two forces interact, and the two trends cancel each other, forming a deformation tendency of the up and down floating for the column. However, since the foundation pit mainly passes through the pebble soil layer, the pebble compressive strength is high, the degree of uplift is not obvious, and the displacement curve fluctuates with the working condition near 0.
During the excavation process, the retaining pile has better rigidity and integrity. The vertical and horizontal displacements of the retaining pile at the end of the excavation and in the middle of the excavation are small, but the axial force of the inner support at the two places is greatly different. Moreover, the inner support axial force at the end has a large fluctuation in the short term, which has a great adverse effect on the inner support. It is important to pay more attention to the design and monitoring of the shoring at the end of the excavation pit.
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Funding information: This research was mainly supported by the National Natural Science Foundation of China (NSFC Grant Nos 52168050 and 51768040).
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Author contributions: All authors have accepted responsibility for the entire content of this manuscript and approved its submission.
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Conflict of interest: The authors state no conflict of interest.
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Ethical approval: The research conducted is not related to human or animal use.
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Data availability statement: The data used to support the findings of this study are available on request from the corresponding author.
References
[1] Zhu Y, Chen R, Wu L, Xu Q, Zhan Z. Reinforcement placement on mechanics and deformation of stepped reinforced retaining wall experimental study of characteristics. Appl Rheol. 2022;32(1):155–65. 10.1515/arh-2022-0131.Search in Google Scholar
[2] Ye SH, Zhao ZF, Wang DQ. Deformation analysis and safety assessment of existing metro tunnels affected by excavation of a foundation pit. Undergr Space. 2021;6(4):421–31. 10.1016/j.undsp.2020.06.002.Search in Google Scholar
[3] Ye SH, Zhou J. Study on stress and deformation of shield tunnel plate under unloading of foundation pit excavation. Arab J Geosci. 2021;14:2490. 10.1007/s12517-021-08842-1.Search in Google Scholar
[4] Wu J, Ye SH, Wang ZQ, Yang D. Application and automatic monitoring and analysis of hybrid support structure in ultra-deep foundation pit engineering in the Lanzhou area under complex environmental conditions. Water-Sui. 2023;15(7):1335. 10.3390/w15071335.Search in Google Scholar
[5] Ye SH, Li DP. Monitoring and numerical simulation analysis of deep and large foundation pit excavation in complex environment. China Civ Eng J. 2019;52(S2):117–26. 10.15951/j.tmgcxb.2019.s2.017.Search in Google Scholar
[6] Jiang SY, Du CB, Sun LG. Numerical analysis of sheet pile wall structure considering soil-structure interaction. Geomech Eng. 2018;16(3):309–20. 10.12989/gae.2018.16.3.309.Search in Google Scholar
[7] Ardakani A, Bayat M, Javanmard M. Numerical modeling of soil nail walls considering Mohr Coulomb, hardening soil and hardening soil with small-strain stiffness effect models. Geomech Eng. 2014;6(4):391–401. 10.12989/gae.2014.6.4.391.Search in Google Scholar
[8] Goh ATC, Zhang F, Zhang WG, Zhang YM, Liu HL. A simple estimation model for 3D braced excavation wall deflection. Comput Geotech. 2017;83:106–13. 10.1016/j.compgeo. 2016.10.022.Search in Google Scholar
[9] Zhang WG, Goh ATC, Xuan F. A simple prediction model for wall deflection caused by braced excavation in clays. Comput Geotech. 2015;63:67–72. 10.1016/j.compgeo.2014.09.001.Search in Google Scholar
[10] Xiang YZ, Goh ATC, Zhang WG, Zhang RH. A multivariate adaptive regression splines model for estimation of maximum wall deflections induced by braced excavation. Geomech Eng. 2018;14(4):315–24. 10.12989/gae.2018.14.4.315.Search in Google Scholar
[11] Zhang WG, Goh ATC, Goh KH, Chew OYS, Zhou D, Zhang R. Performance of braced excavation in residual soil with groundwater drawdown. Undergr Space. 2018;3:150–65. 10.1016/j.undsp.2018.03.002.Search in Google Scholar
[12] Mangushev RA, Osokin AI, Garnyk LV. Experience in preserving adjacent buildings during excavation of large foundation pits under conditions of dense development. Soil Mech Found Eng. 2016;53(5):291–7. 10.1007/s11204-016-9401-9.Search in Google Scholar
[13] Elbaz K, Shen SL, Tan Y, Cheng WC. Investigation into performance of deep excavation in sand covered karst: A case report. Soils Found. 2018;58(4):1042–58. 10.1016/j.sandf.2018.03.012.Search in Google Scholar
[14] Juang CH, Wang L, Hsieh HS, Atamturktur S. Robust geotechnical design of braced excavations in clays. Struct Saf. 2014;49:37–44. 10.1016/j.strusafe.2013.05.003.Search in Google Scholar
[15] Zhang WG, Zhang RH, Goh ATC. MARS inverse analysis of soil and wall properties for braced excavations in clays. Geomech Eng. 2018;16(6):577–88. 10.12989/gae.2018.16.6.577.Search in Google Scholar
[16] Feng SL, Wu YH, Li J, Li P, Zhang ZY, Wang D. The analysis of spatial effect of deep foundation pit in soft soil areas. Geomech Eng. 2012;5(8):309–13. 10.1016/j.proeps.2012.01.052.Search in Google Scholar
[17] Sun YY, Zhou SH, Luo Z. Basal-heave analysis of pit-in-pit braced excavations in soft clays. Comput Geotech. 2017;81:294–306. 10.1016/j.compgeo.2016.09.003.Search in Google Scholar
[18] Mei Y, Hu CM, Wang XY, Yuan YL, Zhao N. Deformation characteristics of ground surface and retaining pile induced by deep foundation pit excavation of subway station in collapsible loess of Xi’an area. China Railw Sci. 2016;37(1):9–16. 10.3969/j.issn.1001-4632.2016.01.02.Search in Google Scholar
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