Predicting Wall Deflections for Deep Excavations with Servo Struts in Soft Clay
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 150, Issue 1
Abstract
Axial forces can be artificially adjusted in deep excavations braced with servo struts to reduce excavation-induced deformations. The interactions among the servo strut, retaining wall, and retained soil must be considered to predict the excavation-induced deformations and axial force adjustment. According to the beam–spring model, this study advances a simplified method to calculate the wall deflections generated by excavation with adjustable axial forces in struts. The proposed method incorporates the coupling relationship between the alterations in the earth pressure and wall displacement to consider soil–wall interactions. A mixed boundary, including force boundary and spring boundary, is introduced in the equilibrium equation to simulate the adjustable forces in the servo struts. The recommended method accounts for the soil–wall–strut interactions. Two real excavation cases supported by traditional and servo steel struts, respectively, validate this study’s findings. Comparisons between the predictions and measurements demonstrate the effectiveness of the proposed method. Projections and measurements indicate that the servo struts reduce the maximum wall deflection, which decreases significantly with the increased axial force. Importantly, the retaining wall moves outside the excavation if excessive axial forces are applied in the servo struts.
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Data Availability Statement
Some or all data, models, or code that support the findings of this study are available from the corresponding author upon reasonable request.
Acknowledgments
The authors gratefully acknowledge financial support from the National Natural Science Foundation of China (NSFC Grant Nos. 52278361 and 52378379) and the Natural Science Foundation of Shanghai (Grant No. 22ZR1430800). Furthermore, the authors are grateful to Biao Huang for the initial data processing of the excavation cases.
References
Chen, B., T. Yan, D. Song, R. Luo, and G. Zhang. 2021. “Experimental investigations on a deep excavation support system with adjustable strut length.” Tunnelling Underground Space Technol. 115 (Sep): 104046. https://doi.org/10.1016/j.tust.2021.104046.
Chen, H., F. Chen, and Y. Lin. 2022. “Slip-line solution to earth pressure of narrow backfill against retaining walls on yielding foundations.” Int. J. Geomech. 22 (5): 04022051. https://doi.org/10.1061/(ASCE)GM.1943-5622.0002356.
Chen, H., J. Li, and L. Li. 2018. “Performance of a zoned excavation by bottom-up technique in Shanghai soft soils.” J. Geotech. Geoenviron. Eng. 144 (11): 05018003. https://doi.org/10.1061/(ASCE)GT.1943-5606.0001964.
Chen, J.-J., M.-G. Li, and J.-H. Wang. 2017. “Active earth pressure against rigid retaining walls subjected to confined cohesionless soil.” Int. J. Geomech. 17 (6): 06016041. https://doi.org/10.1061/(ASCE)GM.1943-5622.0000855.
Di, H., H. Guo, S. Zhou, J. Chen, and L. Wen. 2019. “Investigation of the axial force compensation and deformation control effect of servo steel struts in a deep foundation pit excavation in soft clay.” Adv. Civ. Eng. 2019 (Nov): 5476354. https://doi.org/10.1155/2019/5476354.
Finno, R. J., and M. Calvello. 2005. “Supported excavations: Observational method and inverse modeling.” J. Geotech. Geoenviron. Eng. 131 (7): 826–836. https://doi.org/10.1061/(ASCE)1090-0241(2005)131:7(826).
Finno, R. J., S. Kim, J. Lewis, and N. Van Winkle. 2019. “Observed performance of a sheetpile-supported excavation in Chicago clays.” J. Geotech. Geoenviron. Eng. 145 (2): 05018005. https://doi.org/10.1061/(ASCE)GT.1943-5606.0002010.
Frydman, S., and I. Keissar. 1987. “Earth pressure on retaining walls near rock faces.” J. Geotech. Eng. 113 (6): 586–599. https://doi.org/10.1061/(ASCE)0733-9410(1987)113:6(586).
Hsieh, P.-G., C.-Y. Ou, and W.-H. Hsieh. 2016. “Efficiency of excavations with buttress walls in reducing the deflection of the diaphragm wall.” Acta Geotech. 11 (5): 1087–1102. https://doi.org/10.1007/s11440-015-0416-6.
Hsieh, P.-G., C.-Y. Ou, and Y.-L. Lin. 2013. “Three-dimensional numerical analysis of deep excavations with cross walls.” Acta Geotech. 8 (1): 33–48. https://doi.org/10.1007/s11440-012-0181-8.
Hsieh, P.-G., C.-Y. Ou, and C. Shih. 2012. “A simplified plane strain analysis of lateral wall deflection for excavations with cross walls.” Can. Geotech. J. 49 (10): 1134–1146. https://doi.org/10.1139/t2012-071.
Huang, B., M. Li, J. Chen, Y. Hou, and J. Wang. 2018a. “An improved beam-spring model for excavation support.” In Proc., China-Europe Conf. Geotechnical Engineering, Springer Series in Geomechanics and Geoengineering, edited by W. Wu and H.-S. Yu, 336–339. Cham, Switzerland: Springer.
Huang, B., M.-G. Li, Y. Hou, and J.-J. Chen. 2018b. “Effect of auto-compensating steel struts on stress and deformation behaviors of supporting structures.” Supplement, Rock Soil Mech. 39 (S2): 359–365. https://doi.org/10.16285/j.rsm.2018.1310.
Huang, B., M.-G. Li, Y. Ma, J.-J. Chen, and J.-H. Wang. 2019. “Elastic foundation beam method considering coupling between deformation behavior of retaining wall and earth pressure.” Chin. J. Underground Space Eng. 15 (3): 802–810.
Khosravi, M. H., T. Pipatpongsa, and J. Takemura. 2013. “Experimental analysis of earth pressure against rigid retaining walls under translation mode.” Geotechnique 63 (12): 1020–1028. https://doi.org/10.1680/geot.12.P.021.
Kim, S., and R. J. Finno. 2019. “Inverse analysis of a supported excavation in Chicago.” J. Geotech. Geoenviron. Eng. 145 (9): 04019050. https://doi.org/10.1061/(ASCE)GT.1943-5606.0002120.
Li, M.-G., J.-J. Chen, and J.-H. Wang. 2017. “Arching effect on lateral pressure of confined granular material: Numerical and theoretical analysis.” Granular Matter 19 (2): 20. https://doi.org/10.1007/s10035-017-0700-2.
Li, M.-G., O. Demeijer, and J.-J. Chen. 2020. “Effectiveness of servo struts in controlling excavation-induced wall deflection and ground settlement.” Acta Geotech. 15 (9): 2575–2590. https://doi.org/10.1007/s11440-020-00941-9.
Li, M.-G., X. Xiao, J.-H. Wang, and J.-J. Chen. 2019. “Numerical study on responses of an existing metro line to staged deep excavations.” Tunnelling Underground Space Technol. 85 (Mar): 268–281. https://doi.org/10.1016/j.tust.2018.12.005.
Lim, A., P. G. Hsieh, and C. Y. Ou. 2016. “Evaluation of buttress wall shapes to limit movements induced by deep excavation.” Comput. Geotech. 78 (Sep): 155–170. https://doi.org/10.1016/j.compgeo.2016.05.012.
Liu, B., D.-W. Zhang, C. Yang, and Q.-B. Zhang. 2020. “Long-term performance of metro tunnels induced by adjacent large deep excavation and protective measures in Nanjing silty clay.” Tunnelling Underground Space Technol. 95 (Jan): 103147. https://doi.org/10.1016/j.tust.2019.103147.
Liu, F. Q. 2014. “Lateral earth pressures acting on circular retaining walls.” Int. J. Geomech. 14 (3): 04014002. https://doi.org/10.1061/(ASCE)GM.1943-5622.0000291.
Ng, C. W. W., J. Wei, H. Poulos, and H. Liu. 2017. “Effects of multipropped excavation on an adjacent floating pile.” J. Geotech. Geoenviron. Eng. 143 (7): 04017021. https://doi.org/10.1061/(ASCE)GT.1943-5606.0001696.
Ou, C. Y., P. G. Hsieh, and Y. L. Lin. 2013. “A parametric study of wall deflections in deep excavations with the installation of cross walls.” Comput. Geotech. 50 (May): 55–65. https://doi.org/10.1016/j.compgeo.2012.12.009.
Ou, C.-Y., P.-G. Hsieh, and Y.-L. Lin. 2011. “Performance of excavations with cross walls.” J. Geotech. Geoenviron. Eng. 137 (1): 94–104. https://doi.org/10.1061/(ASCE)GT.1943-5606.0000402.
Ou, C.-Y., J.-T. Liao, and H.-D. Lin. 1998. “Performance of diaphragm wall constructed using top-down method.” J. Geotech. Geoenviron. Eng. 124 (9): 798–808. https://doi.org/10.1061/(ASCE)1090-0241(1998)124:9(798).
Ou, X., X. Zhang, J. Fu, C. Zhang, X. Zhou, and H. Feng. 2020. “Cause investigation of large deformation of a deep excavation support system subjected to unsymmetrical surface loading.” Eng. Fail. Anal. 107 (Jan): 104202. https://doi.org/10.1016/j.engfailanal.2019.104202.
Paik, K. H., and R. Salgado. 2005. “Estimation of active earth pressure against rigid retaining walls considering arching effects.” Geotechnique 55 (4): 342–343. https://doi.org/10.1680/geot.2005.55.4.342.
Shi, J., J. Wei, C. W. W. Ng, and H. Lu. 2019. “Stress transfer mechanisms and settlement of a floating pile due to adjacent multi-propped deep excavation in dry sand.” Comput. Geotech. 116 (Dec): 103216. https://doi.org/10.1016/j.compgeo.2019.103216.
Tan, Y., and Y. Lu. 2018. “Responses of shallowly buried pipelines to adjacent deep excavations in Shanghai soft ground.” J. Pipeline Syst. Eng. Pract. 9 (2): 05018002. https://doi.org/10.1061/(ASCE)PS.1949-1204.0000310.
Tan, Y., and D. Wang. 2013. “Characteristics of a large-scale deep foundation pit excavated by the central-island technique in Shanghai soft clay. II: Top-down construction of the peripheral rectangular pit.” J. Geotech. Geoenviron. Eng. 139 (11): 1894–1910. https://doi.org/10.1061/(ASCE)GT.1943-5606.0000929.
Wang, W.-D., C. W. W. Ng, Y. Hong, Y. Hu, and Q. Li. 2019. “Forensic study on the collapse of a high-rise building in Shanghai: 3D centrifuge and numerical modeling.” Geotechnique 69 (10): 847–862. https://doi.org/10.1680/jgeot.16.P.315.
Wang, Y., H. Wang, and W. Zhang. 2000. “Distribution of earth pressure on a retaining wall.” Géotechnique 50 (1): 83–88. https://doi.org/10.1680/geot.2000.50.1.83.
Wu, S.-H., J. Ching, and C.-Y. Ou. 2013. “Predicting wall displacements for excavations with cross walls in soft clay.” J. Geotech. Geoenviron. Eng. 139 (6): 914–927. https://doi.org/10.1061/(ASCE)GT.1943-5606.0000826.
Wu, Y.-X., H.-M. Lyu, J. Han, and S.-L. Shen. 2019. “Dewatering-induced building settlement around a deep excavation in soft deposit in Tianjin, China.” J. Geotech. Geoenviron. Eng. 145 (5): 05019003. https://doi.org/10.1061/(ASCE)GT.1943-5606.0002045.
Wu, Y.-X., H.-M. Lyu, J. S. Shen, and A. Arulrajah. 2018. “Geological and hydrogeological environment in Tianjin with potential geohazards and groundwater control during excavation.” Environ. Earth Sci. 77 (10): 392. https://doi.org/10.1007/s12665-018-7555-7.
Wu, Y.-X., S.-L. Shen, H.-N. Wu, Y.-S. Xu, Z.-Y. Yin, and W.-J. Sun. 2015. “Environmental protection using dewatering technology in a deep confined aquifer beneath a shallow aquifer.” Eng. Geol. 196 (Sep): 59–70. https://doi.org/10.1016/j.enggeo.2015.06.015.
Xiao, H.-J., S.-H. Zhou, and Y.-Y. Sun. 2019. “Wall deflection and ground surface settlement due to excavation width and foundation pit classification.” KSCE J. Civ. Eng. 23 (4): 1537–1547. https://doi.org/10.1007/s12205-019-1712-8.
Xu, L., H. Chen, F. Chen, Y. Lin, and C. Lin. 2022. “An experimental study of the active failure mechanism of narrow backfills installed behind rigid retaining walls conducted using Geo-PIV.” Acta Geotech. 17 (9): 4051–4068. https://doi.org/10.1007/s11440-021-01438-9.
Zeng, C.-F., G. Zheng, and X.-L. Xue. 2019a. “Responses of deep soil layers to combined recharge in a leaky aquifer.” Eng. Geol. 260 (Oct): 105263. https://doi.org/10.1016/j.enggeo.2019.105263.
Zeng, C.-F., G. Zheng, X.-F. Zhou, X.-L. Xue, and H.-Z. Zhou. 2019b. “Behaviours of wall and soil during pre-excavation dewatering under different foundation pit widths.” Comput. Geotech. 115 (Nov): 103169. https://doi.org/10.1016/j.compgeo.2019.103169.
Zhang, W., A. T. C. Goh, and F. Xuan. 2015. “A simple prediction model for wall deflection caused by braced excavation in clays.” Comput. Geotech. 63 (Jan): 67–72. https://doi.org/10.1016/j.compgeo.2014.09.001.
Zhang, W., Z. Hou, A. T. C. Goh, and R. Zhang. 2019. “Estimation of strut forces for braced excavation in granular soils from numerical analysis and case histories.” Comput. Geotech. 106 (Feb): 286–295. https://doi.org/10.1016/j.compgeo.2018.11.006.
Zheng, G., X. Yang, H. Zhou, Y. Du, J. Sun, and X. Yu. 2018. “A simplified prediction method for evaluating tunnel displacement induced by laterally adjacent excavations.” Comput. Geotech. 95 (Mar): 119–128. https://doi.org/10.1016/j.compgeo.2017.10.006.
ZPDOHURD (Zhejiang Provincial Dept. of Housing and Urban-Rural Development). 2014. Technical specification for building foundation excavation engineering. DB33/T 1096-2014. Hangzhou, Zhejiang, China: ZPDOHURD.
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Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 150 • Issue 1 • January 2024
Copyright
© 2023 American Society of Civil Engineers.
History
Received: Sep 20, 2022
Accepted: Aug 31, 2023
Published online: Oct 27, 2023
Published in print: Jan 1, 2024
Discussion open until: Mar 27, 2024
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