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System reliability-based robust design of deep foundation pit considering multiple failure modes

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Geoscience Frontiers 2024年第2期15卷 169-182页

作者： Li Hong Xiangyu Wang Wengang zhang Yongqin Li runhong zhang Chunxia Chen School of Civil Engineering Chongqing UniversityChongqing 400045China School of Design and the Built Environment Curtin UniversityBentley 6102Western AustraliaAustralia Key Laboratory of New Technology for Construction of Cities in Mountain Area Chongqing UniversityChongqing 400045China Institute of Smart City and Intelligent Transportation Southwest Jiaotong UniversityChengdu 610097China China Southwest Geotechnical Investigation&Design Institute Co. LtdChengdu 610052SichuanChina

Recently,reliability-based design is a universal method to quantify negative influence of uncertainty in geotechnical ***,for deep foundation pit,evaluating the system safety of retaining structures and finding cost-effective design points are main *** address this,this study proposes a novel system reliability-based robust design method for retaining system of deep foundation pit and illustrated this method via a simplified case history in Suzhou,*** proposed method included two parts:system reliability model and robust design *** Propagation Neural Network(BPNN)is used to fit limit state functions and conduct efficient reliability *** common source random variable(CSRV)model are used to evaluate correlation between failure modes and determine the system ***,based on the system reliability model,a robust design method is *** method aims to find cost-effective design *** solve this problem,the third generation non-dominated genetic algorithm(NSGA-III)is *** efficiency and accuracy of whole computations are improved by involving BPNN models and NSGA-III *** proposed method has a good performance in locating the balanced design point between safety and construction ***,the proposed method can provide design points with reasonable stiffness distribution.

关键词： System reliability Machine learning method Non-dominated sorting genetic algorithm Robust design Multiple objective optimization models

Analysis of ground surface settlement in anisotropic clays using extreme gradient boosting and random forest regression models

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Journal of Rock Mechanics and Geotechnical Engineering 2021年第6期13卷 1478-1484页

作者： runhong zhang Yongqin Li Anthony T.C.Goh Wengang zhang Zhixiong Chen Institute for Smart City of Chongqing University in Liyang Chongqing UniversityLiyang213300China Colloge of Aerospace Engineering Chongqing UniversityChongqing400045China School of Civil Engineering Chongqing UniversityChongqing400045China School of Civil and Environmental Engineering Nanyang Technological University639798Singapore Key Laboratory of New Technology for Construction of Cities in Mountain Area(Chongqing University) Ministry of EducationChongqing400045China

Excessive ground surface settlement induced by pit excavation(*** excavation) can potentially result in damage to the nearby buildings and *** this paper,extensive finite element analyses have been carried out to evaluate the effects of various structural,soil and geometric properties on the maximum ground surface settlement induced by braced excavation in anisotropic *** anisotropic soil properties considered include the plane strain shear strength ratio(*** ratio of the passive undrained shear strength to the active one) and the unloading shear modulus *** parameters considered include the support system stiffness,the excavation width to excavation depth ratio,and the wall penetration depth to excavation depth ***,the maximum ground surface settlement of a total of 1479 hypothetical cases were analyzed by various machine learning algorithms including the ensemble learning methods(extreme gradient boosting(XGBoost) and random forest regression(RFR)algorithms).The prediction models developed by the XGBoost and RFR are compared with that of two conventional regression methods,and the predictive accuracy of these models are *** study aims to highlight the technical feasibility and applicability of advanced ensemble learning methods in geotechnical engineering practice.

关键词： Anisotropic clay Numerical analysis Ground surface settlement Ensemble learning

Assessment of basal heave stability for braced excavations in anisotropic clay using extreme gradient boosting and random forest regression

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Underground Space 2022年第2期7卷 233-241页

作者： Wengang zhang runhong zhang Chongzhi Wu Anthony T.C.Goh Lin Wang School of Civil Engineering Chongqing UniversityChongqing 400045China Key Laboratory of New Technology for Construction of Cities in Mountain Area Chongqing UniversityChongqing 400045China School of Civil and Environmental Engineering Nanyang Technological UniversitySingapore 639798Singapore

A finite-element analysis considering the anisotropy for the undrained shear strength was performed to examine the effects of the total stress-based anisotropic model NGI-ADP(developed by Norwegian Geotechnical Institute based on the Active-Direct simple shear-Passive concept)parameters on the base stability of deep braced excavations in *** parameters included the ratio of the plane strain passive shear strength to the plane strain active shear strength s_(u)^(P)=s_(u)^(A),the ratio of the unloading/reloading shear modulus to the plane strain active shear strength G_(ur)=s_(u)^(A),the plane strain active shear strength s_(u)^(A),the unit weight c,the excavation width B,the wall thickness b,and the wall penetration depth *** to the numerical results for 1778 hypothetical cases,extreme gradient boosting(XGBoost)and random forest regression(RFR)were adopted to predict the factor of safety(FS)against basal heave for deep braced *** results indicated that the anisotropic characteristics of soil parameters need to be considered when determining the FS against basal heave for braced *** and RFR can yield a reasonable prediction of the *** paper presents a cuttingedge application of ensemble learning methods in geotechnical engineering.

关键词： Anisotropy NGI-ADP Basal heave Braced excavation Ensemble learning

Influence of groundwater drawdown on excavation responses e A case history in Bukit Timah granitic residual soils

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Journal of Rock Mechanics and Geotechnical Engineering 2018年第5期10卷 856-864页

作者： Wengang zhang Wei Wang Dong Zhou runhong zhang A.T.C. Goh Zhongjie Hou National Joint Engineering Research Center of Geohazards Prevention in Reservoir Area Environment Chongqing University Chongqing 400045 China School of Civil Engineering Chongqing University Chongqing 400045 China School of Civil and Environmental Engineering Nanyang Technological University 639798 Singapore

Performances of a braced cut-and-cover excavation system for mass rapid transit （MRT） stations of the Downtown Line Stage 2 in Singapore are presented. The excavation was carried out in the Bukit Timah granitic （BTG） residual soils and characterized by significant groundwater drawdown, due to dewatering work in complex site conditions, insufficient effective waterproof measures and more permeable soils. A two-dimensional numerical model was developed for back analysis of retaining wall movement and ground surface settlement. Comparisons of these measured excavation responses with the calculated performances were carried out, upon which the numerical simulation procedures were calibrated. In addition, the influences of groundwater drawdown on the wall deflection and ground surface settlement were numerically investigated and summarized. The performances were also compared with some commonly used empirical charts, and the results indicated that these charts are less applicable for cases with significant groundwater drawdowns. It is expected that these general behaviors will provide useful references and insights for future projects involving excavation in BTG residual soils under significant groundwater drawdowns.

关键词： Braced excavation Bukit Timah granitic (BTG) residual soil Wall deflection Groundwater drawdown Empirical charts

State-of-the-art review of soft computing applications in underground excavations

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Geoscience Frontiers 2020年第4期11卷 1095-1106页

作者： Wengang zhang runhong zhang Chongzhi Wu Anthony Teck Chee Goh Suzanne Lacasse Zhongqiang Liu Hanlong Liu Key Laboratory of New Technology for Construction of Cities in Mountain Area Chongqing UniversityMinistry of EducationChongqing 400045China National Joint Engineering Research Center of Geohazards Prevention in the Reservoir Areas Chongqing UniversityChongqing 400045China School of Civil Engineering Chongqing UniversityChongqing 400045China School of Civil and Environmental Engineering Nanyang Technological University639798Singapore Department of Natural Hazards Norwegian Geotechnical Institute0806 OsloNorway

Soft computing techniques are becoming even more popular and particularly amenable to model the complex behaviors of most geotechnical engineering systems since they have demonstrated superior predictive capacity,compared to the traditional *** paper presents an overview of some soft computing techniques as well as their applications in underground excavations.A case study is adopted to compare the predictive performances of soft computing techniques including eXtreme Gradient Boosting(XGBoost),Multivariate Adaptive Regression Splines(MARS),Artificial Neural Networks(ANN),and Support Vector Machine(SVM) in estimating the maximum lateral wall deflection induced by braced *** study also discusses the merits and the limitations of some soft computing techniques,compared with the conventional approaches available.

关键词： Soft computing method(SCM) Underground excavations Wall deformation Predictive capacity

Effects of jet grouting slabs on responses for deep braced excavations

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Underground Space 2021年第2期6卷 185-194页

作者： Wengang zhang Li Hong Yongqin Li runhong zhang Anthony T.C.Goh Hanlong Liu School of Civil Engineering Chongqing UniversityChongqingChina Key Laboratory of New Technology for Construction of Cities on Mountain Area Ministry of EducationChongqing UniversityChongqingChina School of Civil and Environmental Engineering Nanyang Technological UniversitySingapore

Jet grouting slabs are widely used in deep excavations owing to their effectiveness for reducing the deflection of the diaphragm wall and the prop forces acting on the struts and improving the basal-heave *** this paper,according to case histories in Singapore,a series of finite-element numerical simulations are performed to evaluate the effects of jet grouting slabs on responses to deep braced *** the basis of a parametric sensitivity study,a reasonable thickness of jet grouting slabs is *** effects of the wall depth,wall stiffness,soft-clay thickness,and stiffness on the performance of the jet grouting slabs are assessed by comparing and analyzing a series of simulation *** is found that the soft-clay thickness significantly affects the wall deflection and basal heave in deep *** the design of support structures,soil profiles should be considered *** findings of this study provide a reference and guidance for the support system design of similar projects.

关键词： Jet grouting slab Deep excavation Soft clay Finite-element analysis

Performance of braced excavation in residual soil with groundwater drawdown

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Underground Space 2018年第2期3卷 150-165页

作者： W.G.zhang A.T.C.Goh K.H.Goh O.Y.S.Chew D.Zhou runhong zhang Key Laboratory of New Technology for Construction of Cities in Mountain Area Chongqing UniversityChongqingChina School of Civil Engineering Chongqing UniversityChongqingChina School of Civil and Envirormental Engineering Nanyang Technological UniversitySingapore Civil Design Division Land Transport AuthoritySingapore Geotechmical cand Tunnels Division Land Transport AuthoritySingapore

In densely built-up Singapore,relatively stiffsecant-bored piles and diaphragm walls are commonly used in cut-and-cover works to minimize the impact of ground movement on the adjacent structures and *** excavations in stiffresidual soil deposits,the asso-ciated wall deﬂections and ground settlements are generally smaller than for excavations in soft soil ***,if the residual soil permeability is high and the underlying rock is highlyﬁssured or fractured,substantial groundwater drawdown and associated seepage-induced settlement may *** this study,the excavation performance of four sites in residual soil deposits with maximum excavation depths between 20 and 24 m is *** maximum wall deﬂections were found to be relatively small compared to the signiﬁcantly larger maximum ground settlements,owing to the extensive lowering of the groundwater *** this paper,details of the subsurface conditions,excavation support system,ﬁeld instrumentation,and observed excavation responses are presented,with particular focus on the large groundwater drawdown and associated ground ***ﬁc issues encountered during the excavation,as well as the effectiveness of various groundwater control measures,are *** case studies will provide useful references and insights for future projects involving braced excavations in residual soil.

关键词： Residual soil Braced excavation Wall deﬂection Ground settlements Groundwater drawdown Strut force

深基坑支护开挖对临近地铁隧道结构的影响分析研究

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防灾减灾工程学报 2018年第5期38卷 857-866页

作者：章润红刘汉龙仉文岗重庆大学土木工程学院重庆400045 重庆大学库区环境地质灾害防治国家地方联合工程研究中心重庆400045

通过数值计算,采用考虑基坑开挖过程中土体剪切模量随应变增大而衰减特性的HSS模型,研究了基坑开挖卸荷作用下,邻近地铁隧道的埋深、隧道和基坑地连墙距离及刚度比等关键因素对地铁结构附加弯矩和附加位移的影响。结果表明:对于坑底隧道... 详细信息

通过数值计算,采用考虑基坑开挖过程中土体剪切模量随应变增大而衰减特性的HSS模型,研究了基坑开挖卸荷作用下,邻近地铁隧道的埋深、隧道和基坑地连墙距离及刚度比等关键因素对地铁结构附加弯矩和附加位移的影响。结果表明:对于坑底隧道,在地下墙埋置深度范围内,与地连墙水平距离越大,隧道的侧移越小,在地下墙埋深以下,隧道侧移随与地连墙水平距离的增大而增大;通过比较坑侧与坑底隧道的附加弯矩与位移,得出地连墙底附近区域因基坑开挖卸荷引起的隧道附加弯矩较大,出现应力集中和明显的隧道-土-挡墙相互作用效应,坑侧隧道水平附加位移普遍大于竖向附加位移;此外,隧道与地连墙刚度比增大,对挡墙侧移和隧道附加位移都有明显的抑制作用。该研究揭示了基坑开挖作用下隧道-土-挡墙之间的相互作用规律,对深基坑开挖优化设计以及临近地铁结构的保护和安全运行具有一定的指导意义。

关键词：基坑支护开挖 HSS模型隧道-土-挡墙相互作用侧移附加弯矩

考虑空间变异性的基坑降水支护开挖引起地面沉降的可靠度评估

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土木与环境工程学报（中英文） 2021年第1期43卷 54-63页

作者：章润红 GOH Anthony 周廷强仉文岗重庆大学土木工程学院重庆400045 重庆大学山地城镇建设与新技术教育部重点实验室重庆400045 新加坡南洋理工大学土木与环境工程学院新加坡639798 重庆三峡学院土木工程学院重庆404130

对于软黏土或残积土中的深基坑支护开挖,开挖后的地面沉降与基底隆起和挡墙变形密切相关,且受墙后地下水变化的影响显著。提出一种基于最新开发的简化对数回归模型的可靠性分析方法预测地面最大沉降,采用考虑土体空间变异性的方差缩减... 详细信息

对于软黏土或残积土中的深基坑支护开挖,开挖后的地面沉降与基底隆起和挡墙变形密切相关,且受墙后地下水变化的影响显著。提出一种基于最新开发的简化对数回归模型的可靠性分析方法预测地面最大沉降,采用考虑土体空间变异性的方差缩减技术实现一阶可靠性方法(FORM),探讨了地面沉降超过既定阈值的概率,验证了方差缩减技术的高效性。通过分析关于空间平均及关键设计参数的影响发现,土体空间变异性会导致较高的破坏概率,挡墙的系统刚度、地面沉降阈值的大小、土体特性的变化系数以及地下水下降深度也对可靠性指标!有不同程度的影响,忽略其影响会导致不可靠的设计,较大的特征长度会导致较低的破坏概率和较高的!,同时考虑cu/σ′v和E50/cu的空间变异性会比单独考虑其中一项对!影响更大。

关键词：地面沉降基坑支护开挖降水空间变异性方差缩减