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A modified back analysis method for deep excavation with multi-objective optimization procedure

Journal of Rock Mechanics and Geotechnical Engineering 2024年第4期16卷 1373-1387页

作者： Chenyang Zhao Le Chen Pengpeng Ni Wenjun Xia Bin Wang State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China Guangdong Research Center for Underground Space Exploitation Technology School of Civil EngineeringSun Yat-sen UniversityGuangzhou510275China Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) Zhuhai519000China Jiangsu Provincial Transportation Engineering Construction Bureau Nanjing210004China

Real-time prediction of excavation-induced displacement of retaining pile during the deep excavation process is crucial for construction safety.This paper proposes a modified back analysis method with multi-objective optimization procedure,which enables a real-time prediction of horizontal displacement of retaining pile during construction.As opposed to the traditional stage-by-stage back analysis,time series monitoring data till the current excavation stage are utilized to form a multi-objective function.Then,the multi-objective particle swarm optimization (MOPSO) algorithm is applied for parameter identification.The optimized model parameters are immediately adopted to predict the excavation-induced pile deformation in the continuous construction stages.To achieve efficient parameter optimization and real-time prediction of system behavior,the back propagation neural network (BPNN) is established to substitute the finite element model,which is further implemented together with MOPSO for automatic operation.The proposed approach is applied in the Taihu tunnel excavation project,where the effectiveness of the method is demonstrated via the comparisons with the site monitoring data.The method is reliable with a prediction accuracy of more than 90%.Moreover,different optimization algorithms,including non-dominated sorting genetic algorithm (NSGA-II),Pareto Envelope-based Selection Algorithm II (PESA-II) and MOPSO,are compared,and their influences on the prediction accuracy at different excavation stages are studied.The results show that MOPSO has the best performance for high dimensional optimization task.

关键词： Multi-objective optimization back analysis Surrogate model Multi-objective particle swarm optimization(MOPSO) Deep excavation

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Challenges associated with numerical back analysis in rock mechanics

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第6期14卷 2058-2071页

作者： Gabriel Walton Sankhaneel Sinha Department of Geology and Geological Engineering Colorado School of MinesGoldenCO80401USA

Numerical back analysis is a valuable tool available to rock mechanics researchers and practitioners.Recent studies related to back analysis methods focused primarily on applications of increasingly sophisticated optimization algorithms(primarily machine learning algorithms)to rock mechanics problems.These methods have typically been applied to relatively simple problems;however,more complex back analyses continue to be conducted primarily through ad hoc manual trial-and-error processes.This paper provides a review of the basic concepts and recent developments in the field of numerical back analysis for rock mechanics,as well as some discussion of the relationship between back analysis and more broadly established frameworks for numerical modelling.The challenges of flexible constraints,non-uniqueness,material model limitations,and disparate data sources are considered,and representative case studies are presented to illustrate their impacts on back analyses.The role of back analysis(or“model calibration”)in bonded particle modelling(BPM),bonded block modelling(BBM),and synthetic rock mass(SRM)modelling is also considered,and suggestions are made for further studies on this topic.

关键词： back analysis Numerical modelling Inversion Case studies

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Numerical and back analysis-based methodology for support design of cut slopes at the Turkish – Georgian Border(NE Turkey)

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Journal of Mountain Science 2021年第6期18卷 1678-1695页

作者： Muhammet Oğuz SÜNNETCI Hakan ERSOY Arzu FIRAT ERSOY Karadeniz Technical University Dept.of Geological EngineeringTrabzon 61080Turkey

In this study, geophysical and geotechnical studies were carried out in NE Turkey to evaluate the stability and support design of cut slopes that will be excavated during the construction of a new border control complex. 13 vertical and 3 inclined boreholes were drilled, and 2D electrical resistivity tomography surveys were conducted along 8 profiles to investigate the horizontal and vertical continuity of the geological units. Strength characteristics of all units were determined by laboratory tests. Limit equilibrium(LE) slope stability analyses were conducted on the geological model for static and pseudo-static conditions and factor of safety values as low as 0.227 were determined for post-excavation. back analysis was conducted for the determination of required support forces on the slopes to achieve a factor of safety of 1.3. A feasible support system consisting of bored piles and rock anchors was designed based on back analysis results for each cut slope. LE analyses were repeated after the implementation of the designed support systems and the lowest factor of safety value increased to 1.35. The utility and safety of the designed support systems were investigated using finite element slope stability analyses and strength reduction factor values higher than 1.3 were determined which means support systems will function as intended and no support failure will occur. Lastly, quick reference charts were created for alluvium and residual soil materials to easily determine the safe slope angle in the future in case no support measures will be applied.

关键词： Slope stability 2D electrical resistivity Geotechnical studies Finite element Sensitivity analysis back analysis

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Probabilistic back analysis for geotechnical engineering based on Bayesian and support vector machine

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Journal of Central South University 2015年第12期22卷 4778-4786页

作者：陈炳瑞赵洪波茹忠亮李贤 State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of Sciences School of Civil Engineering Henan Polytechnic University School of Resource and Environmental Engineering Wuhan University of Science and Technology

Geomechanical parameters are complex and uncertain.In order to take this complexity and uncertainty into account,a probabilistic back-analysis method combining the Bayesian probability with the least squares support vector machine(LS-SVM) technique was proposed.The Bayesian probability was used to deal with the uncertainties in the geomechanical parameters,and an LS-SVM was utilized to establish the relationship between the displacement and the geomechanical parameters.The proposed approach was applied to the geomechanical parameter identification in a slope stability case study which was related to the permanent ship lock within the Three Gorges project in China.The results indicate that the proposed method presents the uncertainties in the geomechanical parameters reasonably well,and also improves the understanding that the monitored information is important in real projects.

关键词： geotechnical engineering back analysis uncertainty Bayesian theory least square method support vector machine(SVM)

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Application of back analysis on Laterally Loaded Single Pile

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Journal of Shanghai Jiaotong university(Science) 2015年第6期20卷 696-702页

作者：吴锋龚景海富坤 School of Naval Architecture Ocean & Civil Engineering Shanghai Jiaotong University Shanghai Third Harbour Engineering Science & Technology Research Institute Co. Ltd.

In views of the limitations of the existing methods for calculating the pile foundation capacity, a back analysis approach of the m-value is introduced. In order to consider the sensitivity of pile behavior to the m-value,the relationships between the applied horizontal loads at pile head and the corresponding m-value along with the pile stiffness changes are studied. Based on statistics data from the extensive in-situ tests, the back analysis results suggest an exponential expression for the m-value in various soil conditions and horizontal displacements at pile head. This method is capable of providing an accurate m-value in calculating the pile responses under lateral loads.

关键词： laterally loaded piles m-method back analysis horizontal displacement

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Numerical study of the mechanical process of long-distance replacement of the definitive lining in severely damaged highway tunnels

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Underground Space 2023年第2期9卷 200-217页

作者： Xinrong Liu Yang Zhuang Xiaohan Zhou Chao Li BinBin Lin Ninghui Liang Zuliang Zhong Zhiyun Deng School of Civil Engineering Chongqing UniversityChongqing 400045China National Joint Engineering Research Center of Geohazards Prevention in The Reservoir Areas Chongqing 400045China College of Civil Engineering Guizhou UniversityGuizhou 550025China Department of Hydraulic Engineering Tsinghua UniversityBeijing 100084China

Mountain road tunnels are prone to water leakage and lining corrosion under the complex geological conditions and corrosive envi-ronments,which will reduce the strength of the lining structure until it loses its load-bearing capacity;eventually,the definitive lining will need to be replaced.In this paper,a highway tunnel in a mountainous area in Southwest China is taken as an example.Field investi-gation found that the tunnel was seriously corroded by sulfate,the strength of the definitive lining decreased,and large-scale cracks and spalling appeared on the surface,so the operator decided to replace the definitive lining by the method of interval replacement.Based on the data obtained from drilling and coring,a numerical model of long-distance replacement of the definitive lining of the damaged tunnel is established.First,the back analysis of the calculation parameters is carried out,and the modified calculation results are com-pared with the field monitoring results for verification.Then,the deformation trend of the tunnel and the development of the plastic zone during the process of long-distance replacement of the definitive lining are studied.Finally,the construction scheme is optimized.Numer-ical analysis results show that the replacement of the definitive lining of the tunnel mainly leads to the settlement of the arch crown and the uplift of the inverted arch.The deformation of the tunnel shows two rapid growth stages and two stable stages during the replace-ment process;after replacement,the deformation of the arch crown and the inverted arch is divided into two buffer zones and one stable zone.In the progress of the replacement of the definitive lining,the plastic zone does not change.Regarding the reinforcement measures,with the increase in the grouting range,the grouting efficiency decreases,and the effect of the temporary steel arch on controlling the overall deformation is not obvious.The length of the replacement of the single section should be determined according to the geological conditions of the

关键词： Deteriorated tunnel Long-distance replacement of the definitive lining back analysis Reinforcement measures Numerical simulation

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Numerical Simulation of Vacuum Preloading for Chemically Conditioned Municipal Sludge

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Journal of Renewable Materials 2023年第1期11卷 363-378页

作者： Wenwei Li Xinjie Zhan Baotian Wang Jinyu Zuo Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering College of Civil and Transportation EngineeringHohai UniversityNanjing210098China Geotechnical Engineering Department Nanjing Hydraulic Research InstituteNanjing210029China

Municipal sludge is a sedimentation waste produced during the wastewater process in sewage treatment plants.Among recent studies,pilot and field tests showed that chemical conditioning combined with vacuum preloading can effectively treat municipal sludge.To further understand the drainage and consolidation characteristics of the conditioning sludge during vacuum preloading,a large deformation nonlinear numerical simulation model based on the equal strain condition was developed to simulate and analyze the pilot and field tests,whereas the simulation results were not satisfactory.The results of the numerical analysis of the pilot test showed that the predicted consolidation degree was greater than that measured by the field tests,which is attributed to the relatively low permeability layer formed during the preloading process of the prefabricated vertical drain.To better reflect the consolidation process of the conditioned sludge,a simplified analysis method considering the low permeability layer around the prefabricated vertical drain was proposed.The initial permeability coefficient of the low permeability layer is determined via numerical simulations using finite difference method.The predicted settlement curve was in good agreement with the measured results,which indicated that the numerical simulation based on the equal strain condition considering the relatively low permeability layer can better analyze the consolidation process of ferric chloride-conditioning sludge with vacuum preloading.

关键词： Sludge treatment large deformation numerical simulation chemical conditioning-combined vacuum preloading low permeability coefficient back analysis

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A REVISED SOLUTION OF EQUIVALENT PERMEABILITY TENSOR FOR DISCONTINUOUS FRACTURES

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Journal of Hydrodynamics 2012年第5期24卷 711-717页

作者： HE Ji CHEN Sheng-hong SHAHROUR Isam State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan University 430072Wuhan China Laboratoire Genie Civil et geo-Environnement University Lille 1 59650 Villeneuve d Ascq France

The equivalent permeability tensor is essential to the application of the equivalent porous media model in the numerical seepage simulation for fractured rock masses. In this paper, a revised solution of the equivalent permeability tensor is proposed to represent the influence of the fracture connectivity in discontinuous fractures. A correction coefficient is involved to reflect the com- plex seepage flow type through the rock bridge. This correction coefficient is back analyzed from single-hole packer tests, based on the Artificial Neural Network （ANN） back analysis and the Finite Element Method （FEM） seepage simulation. The limitation of this back analysis algorithm is that the number of single-hole packer tests should be equal or greater than the number of fracture sets, and three is the maximum number of the fracture sets. The proposed solution and the back analysis algorithm are applied in the permea- bility measurement and the seepage simulation for the Xiaowan arch dam foundation.

关键词： discontinuous fractures permeability tensor back analysis packer test Artificial Neural Network （ANN）

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Breaches of the Baige Barrier Lake: Emergency response and dam breach flood

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Science China(Technological Sciences) 2020年第7期63卷 1164-1176页

作者： CAI YaoJun CHENG HaiYun WU ShuaiFeng YANG QiGui WANG Lin LUAN YueSheng CHEN ZuYu Changjiang Institute of Survey PlanningDesign and ResearchWuhan 430010China Bureau of Hydrology Changjiang Water Resource CommissionWuhan 430010China State Key Laboratory'of Simulation and Regulation of Water Cycle in River Basin.China Institute of Water Resources and Hydropower Research Beijing 100038China Department of Geotechnical Engineering China Institute of Water Resources and Hydropower ResearchBeijing 100048China State Key Laboratory of Eco-hydraulics in Northwest Arid Region Xi'an University of Technology'Xi'an 710048China Changjiang Survey Institute of MWR Wuhan 430011China

This paper documents the emergency response to the breaches of the Baige Barrier Lake. The lake was successively formed by landslides that occurred on October 10 and November 3, 2018 at the provincial border between Sichuan and Tibet in China. The barrier lake created by the "10.10" landslide breached on October 12 and triggered a flood with a peak discharge around 10000 m^3/s. The residual landslide barrier was enhanced by a second landslide on November 3, resulting in a higher barrier with larger flood potential. An overflow channel was excavated in the crest of the barrier to prompt the breach to be triggered at a lower water level. The second breach happened on November 12 with a measured peak discharge of 31000 m^3/s. Nearly 75000 people were evacuated before the two breaches. In order to prevent the downstream dams from possible over-topping, nearly 3.27×10~8 m^3 of the stored volume was released from the Liyuan reservoir 688 km downstream of Baige Barrier Lake. This paper presents the measured hydrographs and the back-analysis results for the "11.03" barrier lake. It is shown that the modern models of dam breach hydraulics can reasonably reproduce the barrier breach hydrographs;however, further studies are needed to define the key parameters which highly influence the calculated results. Knowledge acquired during the emergency response to the case can be shared with experts working on breaches of embankment dams and can be referenced to promote both the theory study and the engineering practice to mitigate the potential risks caused by this type of catastrophic events.

关键词： dam breach back analysis baige barrier lake emergency response downstream flood propagation

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Application and Validation of a Multi-block Constitutive Model at Landslides of the Wenchuan Earthquake

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工程科学与技术 2018年第3期50卷 33-45页

作者： STAMATOPOULOS Constantine XIONG Ke DI Baofeng Stamatopoulos and Associates Limited Liability Company 5 Isavron Street Athens 114-71 Greece &Hellenic Open University Parodos Aristotelous 18 Patra 26335 Greece Institute for Disaster Management and Reconstruction Sichuan University Chengd

A multi-block model and a corresponding computer program have been developed which predict the kinematics of landslides.Furthermore,a unique event for studying different models simulating the triggering and movement of landslides is the 2008Wenchuan earthquake in the mountainous region in Sichuan Province of China,which caused a large number of rapid landslides.The purpose of the paper is two-fold:(a)to propose and incorporate into the multi-block model constitutive relations predicting soil response along slip surfaces,and(b)to apply the multi-block model with the constitutive relations at landslides triggered by the Wenchuan earthquake.The proposed constitutive equations predict the shape of the shear stress-displacement response measured in ring shear tests.In the application,four landslides caused by the Wenchuan earthquake were considered.Only in one of these landslides the shear resistance-displacement response along the slip surface has been measured in laboratory tests.At this landslide,the triggering and movement of the landslide was predicted.In the other landslides,back analyses were performed and it was observed that the multi-block model predicted reasonably well the final configuration of all slides.In addition,as the measured and back-estimated total friction angle of all landslides was less than 180,and the materials along the slip surface were sandy,it is inferred that some,or all of the slip surface during these slides was sheared in an undrained manner and excess pore pressures generated during sliding played a key role in the triggering and movement of these landslides.Concluding,the paper(A)proposed and validated a multi-block constitutive model which can be applied to predict the triggering and movement of earthquake-induced slides and(B)by analyzing four landslides of the 2008 Wenchuan earthquake,it concludes that some,or all of the slip surface during these slides,was sheared in an undrained manner and excess pore pressures generated during sliding played a key role in the triggering and m

关键词： Wenchuan earthquake multi-block model seismic displacement landslides back analysis strain softening

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