Development of Finite Element Limiting Analysis Method and Its Applications in Geotechnical Engineering

The Finite Element Limiting Analysis Method(LELAM) has the advantage of combining a numerical analysis method with traditional limiting equilibrium methods.It is particularly applicable to the analysis and design of geotechnical engineering.In the early 20th century,FELAM has been developed vigorously in domestic geotechnical engineering over international common finite element procedures.It has made great achievements in basic theory research and computational precision,thus broadening the application fields in practical projects.In order to gradually make innovations in geotechnical design methods,some of our research results are presented,mainly including geotechnical safety factor definitions,the principles for use of the method concerned,the overall failure criterion,the deduction and selection of the yield criterion,and the measurement to improve the computational precision,etc..The application field has been broadened from two-dimensional to three-dimensional,from soil slope to jointed rock slope and foundation,from stable seepage to non-stable seepage,from slope and foundation to tunnel.This method has also been used in search of many hidden sliding surfaces of complex landslides,conducting the structural support design considering the interaction between the soil and the structure,and computing simulation foundation bearing plates load tests,etc..

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

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.

The System Analysis and Reliability Evaluation of Rock Slopes

The principal of preferred plane analysis is a new research view and model of rock slope engineering geology. It advocates that the rock slope stability, boundary conditions and failure model are controlled by preferred planes. Therefore, the problem of slope stability evaluation can be converted into the search for preferred planes and determination of preferred separating bodies. The organic combination of the deterministic model and the indeterministic model can be realized by applying the systems engineering principle and the research model and method of reliability analysis in the quantitative evaluation and prediction of rock slope stability. Finally, the paper presents the case studies of slopes of the Yangtze Gorge Project and the Ma'anshan openpit mine.

Application of data analysis method in geotechnical engineering

Geotechnical seismic engineering belongs to the cross field of geotechnical engineering and earthquake engineering. Due to the dual effects of the variability of geotechnical objects and the complexity of dynamic loading, the scientific problems involved in this field have to face more uncertainties. Through the analysis on the status quo of uncertainty analysis methods in geotechnical earthquake engineering in the field of non deterministic analysis clear difficulties, weak links with all kinds of uncertainty analysis method to solve the inherent weakness of determining geotechnical earthquake engineering uncertainty problem, and can determine the establishment and improvement to provide some ideas and direction analysis model for non.

Uncertainty quantification of inverse analysis for geomaterials using probabilistic programming

Uncertainty is an essentially challenging for safe construction and long-term stability of geotechnical engineering.The inverse analysis is commonly utilized to determine the physico-mechanical parameters.However,conventional inverse analysis cannot deal with uncertainty in geotechnical and geological systems.In this study,a framework was developed to evaluate and quantify uncertainty in inverse analysis based on the reduced-order model(ROM)and probabilistic programming.The ROM was utilized to capture the mechanical and deformation properties of surrounding rock mass in geomechanical problems.Probabilistic programming was employed to evaluate uncertainty during construction in geotechnical engineering.A circular tunnel was then used to illustrate the proposed framework using analytical and numerical solution.The results show that the geomechanical parameters and associated uncertainty can be properly obtained and the proposed framework can capture the mechanical behaviors under uncertainty.Then,a slope case was employed to demonstrate the performance of the developed framework.The results prove that the proposed framework provides a scientific,feasible,and effective tool to characterize the properties and physical mechanism of geomaterials under uncertainty in geotechnical engineering problems.

Water Environmental Impact Assessment and Analysis of Foshan Brewery Project

In recent years, the beer industry is a biological food industry that consumes a lot of water, and it has developed rapidly in China. The sewage discharged from the mass production of beer poses a huge threat to the environment. In order to evaluate and better solve the possible environmental impacts of beer treatment engineering projects, a brewery project in Foshan City is taken as an example to investigate the water pollution generation links of the engineering process including surface water and groundwater. According to the relevant technical methods and standards, water pollution factors are screened, and concentration and discharge are monitored. Through comprehensive analysis, predictive evaluation is obtained. It is confirmed that the project meets the requirements of national laws and regulations and environmental protection standards.

Comprehensive Analysis of High Temperature Performance of SBS-modified Asphalt Mixture

Evaluation of high temperature performance of SBS-modified asphalt mixture was presented.Both wheel loaded method and creep method were adopted for two different mixtures and two kinds of specimens with different height,and corresponding indicators were measured.Meanwhile,the correlation between these indicators was thoroughly analyzed and two kinds of mixtures were compared.The experimental results show that there is a good linear relationship between LWT indicators and CT indicators for M-13,while a relatively poor relationship for M-25,especially that between dynamic stiffness and static stiffness and that between dynamic stability and static creep stiffness.Besides,logarithmic relationship between DS and RD has a higher determination coefficient than that for linear relationship.Thus,multi-index evaluation should be taken for synthetically assessing high temperature performance of asphalt mixture.

Research on Risk Evaluation Method for International Engineering Projects

Risk evaluation is one of the important elements of international engineering project management. The risk factors of international engineering projects are systematically analyzed from multiple dimension features of the projects. The muhilayer evaluation index system for the international engineering project risk assessment is proposed and constructed, which consists of 8 I-grade indexes and 24 II-grade indexes as policy risk, market risk, resource risk, and technical scheme risk, schedule risk, funding risk, personnel risk and management risk. And then the self-evaluation and benchmarking evaluation methods are applied to evaluate the international engineering project risk, and established the corresponding mathematical models. Finally, a project evaluation example is given to illustrate the applicability and effectiveness of the mathematical models.

Dependability Evaluation of a Vehicle System by Simulation Method

The vehicle system studied in this paper is a type of complex repairable system in which the subsystems follow various failure distributions and conform to arbitrary failure and repair distributions.The failure data of subsystems are sometimes lacking,and the reliability test sample sizes tend to be small.Monte-Carlo technique combined with Bayes method is used to evaluate its dependability(reliability and maintainability).Following the "first-in,first-out" queuing rule,the logic relation of dependability is established by means of repairing priority and event lists.Simulation outputs the entire history of a mission,statistics of reliability and maintainability parameters and provides the basic data for system reliability design and maintainability management.

康复机器人训练脑性瘫痪患者:改善下肢运动功能效果的Meta分析

目的:系统评价康复机器人治疗脑性瘫痪患者下肢运动功能的临床效果,并比较不同机器人的疗效差异。方法:检索PubMed、Web of Science、Embase、Cochrane Library、中国知网、中国生物医学文献数据库、维普和万方数据库,搜集从建库至2024-04-10发表的关于康复机器人治疗脑性瘫痪患者运动功能障碍的随机对照试验。主要结局指标包括肌肉力量,肌张力、平衡功能、步速、步频、步长、步行耐力、下肢运动功能、日常生活活动能力。根据《国际功能、残疾和健康分类》对上述指标进行编码,通过Meta分析评价临床疗效并比较不同机器人的疗效差异。由2名研究人员进行文献检索与筛选,使用Cochrane 5.1.0偏倚风险评估工具对纳入文献进行质量评价。采用RevMan 5.4软件和Stata 16.0软件进行Meta分析。结果:①最终纳入15篇文献,共512例患者,试验组260例、对照组252例。②Meta分析结果显示,与常规康复疗法相比,康复机器人可以提高身体结构和功能(SMD=0.41,95%CI:0.24-0.58,P<0.05)、活动(SMD=0.53,95%CI:0.41-0.65,P<0.05)和参与能力(MD=7.86,95%CI:1.54-14.18,P<0.05)。其中,康复机器人可以改善脑性瘫痪患者下肢肌力、平衡功能、步速、步行耐力、下肢粗大运动功能和日常生活活动能力,但对步频、步长和肌张力的效果不明显。③网状Meta分析结果显示,步速:Innowalkpro>Gait trainer>Lokomat>3DCalt;6MWT评分:Gait trainer>Lokomat>Lokohelp>Innowalkro;GMFM-88D区评分:Lokohelp>Lokomat>KidGo>Innowalkpro>3DCalt;GMFM-88E区评分:Lokomat>Lokohelp>KidGo>3DCalt>Innowalkpro。结论:基于《国际功能、残疾和健康分类》,康复机器人训练可以改善脑性瘫痪患者下肢运动功能和日常生活活动能力。在改善步速方面,Innowalkpro机器人效果更优;在改善6MWT评分方面,Gait trainer机器人效果更优;在改善GMFM-D区评分方面,Lokohelp机器人效果更优;在改善GMFM-E区评分方面,Lokomat机器人效果更优。

Upper-Bound Limit Analysis of the Multi-Layer Slope Stability and Failure Mode Based on Generalized Horizontal Slice Method

Multi-layer slopes are widely found in clay residue receiving fields.A generalized horizontal slice method(GHSM)for assessing the stability of multi-layer slopes that considers the energy dissipation between adjacent horizontal slices is presented.In view of the upper-bound limit analysis theory,the energy equation is derived and the ultimate failure mode is generated by comparing the sliding surface passing through the slope toe(mode A)with that below(mode B).In addition,the influence of the number of slices on the stability coefficients in the GHSM is studied and the stable value is obtained.Compared to the original method(Chen’s method),the GHSM can acquire more precise results,which takes into account the energy dissipation in the inner sliding soil mass.Moreover,the GHSM,limit equilibrium method(LEM)and numerical simulation method(NSM)are applied to analyze the stability of a multi-layer slope with different slope angles and the results of the safety factor and failure mode are very close in each case.The ultimate failure modes are shown to be mode B when the slope angle is not more than 28°.It illustrates that the determination of the ultimate sliding surface requires comparison of multiple failure modes,not only mode A.

BOFDA技术综述及用于岩土工程监测的可行性研究

布里渊散射光频域分析技术(BOFDA),是一套通过测量连续泵浦光和连续探测光相互作用后产生的布里渊散射光所确定的基带函数的脉冲响应,运用相关计算方法确定传感光纤上物理信息的综合系统。与其它分布式光纤传感器相比,BOFDA可在窄基带下操作,具有分布式、高信噪比、高空间分辨率、低成本、多频信号平行测量和处理、信号动态范围大等优点。本文对BOFDA用于测量应变和温度的基本原理进行了介绍,并对前人做的室内、现场试验进行了概括和总结。

Probabilistic characterization of cyclic shear modulus reduction for normally to moderately over-consolidated clays

Evaluation of the cyclic shear modulus of soils is a crucial but challenging task for many geotechnical earthquake engineering and soil dynamic issues. Improper determination of this property unnecessarily drives up design and maintenance costs or even leads to the construction of unsafe structures. Due to the complexities involved in the direct measurement, empirical curves for estimating the cyclic shear modulus have been commonly adopted in practice for simplicity and economical considerations. However, a systematic and robust approach for formulating a reliable model and empirical curve for cyclic shear modulus prediction for clayey soils is still lacking. In this study, the Bayesian model class selection approach is utilized to identify the most significant soil parameters affecting the normalized cyclic shear modulus and a reliable predictive model for normally to moderately over-consolidated clays is proposed. Results show that the predictability and reliability of the proposed model out performs the well-known empirical models. Finally, a new design chart is established for practical usage.

Settlement Mode Analysis for An Immersed Tube Tunnel Considering A Nonuniform Foundation Under Tidal Load

Immersed tube tunnels are usually placed on soft soil layers in cross-sea tunnelling engineering.Owing to the influence of stratum conditions and slope design,the longitudinal distribution of substratum layers is generally uneven.Thus,the inhomogeneous deformation of the element-joint becomes the key factor in the failure of the immersed tube tun-nel.Therefore,a corresponding calculation method for joint deformation is needed to explore the deformation law of immersed tube tunnels.By constructing a three-section immersed tube tunnel analysis model(TTM),the relationship between the two types of deformation of the immersed tube tunnel structure in a longitudinal nonuniform soft soil foundation is described,and the deformation characteristics of the immersed structure under different boundaries are discussed.Based on the mechanical behaviour of the joint and foundation,according to the Timoshenko beam on the Vlasov two-parameter foundation(VTM),considering the tidal cyclic load during the operation and maintenance period,an example analysis is given.Moreover,the deformation characteristics and development trend of the immersed tube tunnel under the influence of different soil layers are discussed.The obtained results have a certain guiding significance for the deformation calculation of immersed tube tunnels.

Elaboration of a conceptual solution for the development of the Arctic shelf from seasonally flooded coastal areas

Currently,construction of facilities in the Arctic is carried out on sand islands,but there are limitations for remote coastal conditions.These restrictions are associated with the lack of quarries with construction sand in the immediate vicinity of the work site,as well as the risk of seasonal flooding of the territories.This article includes conceptual solutions for construction of modular piling in Arctic nearshore conditions,upon which drilling rigs and auxiliary equipment can be placed for the purpose of subsequent wildcatting,development and exploratory extended reach drilling wells(with measured depth about 15000 m).During the construction of the modular piling foundations,a mathematical simulation of the thermodynamic condition of the frozen ground was conducted,and the bearing capacity of the foundations was assessed.The proposed solutions will solve these problems by constructing modular pile foundations and placing the necessary infrastructure on them,taking into account the distribution of loads during operation in seasonally flooded areas.

考虑水力效应的裂缝边坡稳定性非线性能耗分析

现有考虑水力效应的裂缝边坡稳定性分析大多基于线性破坏准则,而岩土体破坏往往呈现非线性特征,因此开展水力效应影响下的裂缝边坡稳定性非线性极限上限分析具有重要意义。基于极限分析上限定理及强度折减技术,结合“外切线法”非线性破坏准则,构建坡顶含竖直裂缝的边坡对数螺旋线破坏模式,根据虚功原理推导出裂缝边坡安全系数解析式,通过MATLAB优化计算,结合边坡工程实例探讨了典型因素对裂缝边坡稳定性、临界裂缝及滑动面位置的影响规律。研究结果表明:随着地下水位h的持续上升,边坡安全系数不断降低,临界裂缝深度逐渐增大且临界裂缝位置逐渐向坡顶缘偏移;非线性系数m明显影响边坡的稳定性,边坡安全系数随着非线性系数的增大显著减小,采用线性破坏准则会高估地下水位变化对边坡稳定性的影响;随着非线性系数的增大,临界裂缝深度随之增大,临界裂缝位置距离坡顶缘越来越远,滑坡体体积逐渐增大;裂缝与坡顶缘距离l m随着非线性系数m的增大而增大(当m增大0.2时,l m增大约1 m),且随着裂缝与坡顶缘距离的增大,边坡安全系数无明显变化,临界裂缝深度先逐渐减小后趋于稳定。

Application of Nanotechnology in Soil Stabilization

Nano-technology is expanding its horizon in various science and technology fields.In civil engineering,soil is a complex material and used for various functions and applications.Meanwhile,sometimes an effective soil stabilization technique is needed to fulfil the site criteria and can be achieved by adopting various methods e.g.,physical,chemical,thermal or reinforcement using geotextiles and fabrics.The mechanism of soil stabilization using nanomaterials is still unexplored and open to prospective researchers.The present article attempts to touch and explore the possibilities of nano-technology in soil improvement and its applications in various civil engineering works.Microstructural analysis of the nanomaterials treated soils using the latest equipment has also been discussed.The study interprets that the use of nano materials is still limited,due to their high cost and sophisticated handling procedures.Though the use of nanoparticles in soil stabilization results in extraordinary improvements in various soil properties,the improved soil properties could be utilized for various geotechnical projects.The present study bridges the past findings to the present scenario of nanomaterials in soil improvement.

基于匝道合流数据的自动驾驶汽车安全性测试评价方法

针对自动驾驶汽车测试场景不明确、评价模型主观性强等问题,研究了高速匝道汇入场景下的典型测试场景提取方法和自动驾驶汽车匝道汇入安全性客观评价方法。深入分析了匝道汇入功能场景下的逻辑场景要素,对自然驾驶数据中的自车速度、车间距离、前车车速等逻辑场景要素进行聚类,得到两类典型的匝道汇入测试场景用于自动驾驶汽车的仿真测试。构建多层次自动驾驶汽车评价体系,引入基于自然驾驶数据的核密度估计模型来获取指标最优阈值,建立以最优阈值为参考序列、以层次分析法(AHP)和客观赋权法(CRITIC)为权重输入的灰色关联理评价模型,对自动驾驶汽车在汇入过程中的安全性进行客观评价。评价结果表明:基于核密度估计的灰色关联理论模型评价结果与主观模糊综合分析模型的评价结果相似率达98.01%,验证了客观模型的有效性。

基于Kelvin模型的圆形巷道位移反分析的唯一性

讨论了黏弹性岩体中圆形巷道位移反分析的唯一性问题。以Kelvin模型为研究对象,在圆形巷道位移解析解的基础上,利用参数可辨识条件,对岩体参数进行了位移反分析唯一性的研究。结果表明:无论测量出多少个测点的位移,都不能唯一地反分析出所有岩体参数,至少要已知2个参数,才有可能唯一地反分析出其余参数;随着已知参数的增多,各参数的可辨识性逐渐增强;竖向地应力与水平地应力是否相等,且二者作为已知条件时其大小是否为0对反分析结果有较为明显的影响;适当减少待反演参数的数量对提升反分析结果的唯一性有显著影响;所有参数中地应力具有最好的可辨识性,其次是弹性模量,泊松比及黏滞系数最差。

西安湿陷性黄土地区狭长深基坑变形分析

为了探究西安地铁车站深基坑开挖过程中桩体侧移、地表沉降等时空演变规律,以西安地区某地铁车站深基坑为工程背景,同时收集了该地区2#、3#、4#线20个狭长基坑的实测数据,并对其进行统计分析。结果表明:地铁基坑围护结构最大侧移δhm=0.04%H~0.10%H(H为开挖深度),平均值为0.06%H,最大侧移位置深度为0.7H;地表最大沉降值δvm=0.036%H~0.116%H,主要影响区在1.4H范围以内;高斯函数模型可以预测西安地区的地表沉降,其影响范围为3.5H;在特定范围内,提高支护桩的刚度和插入比可以有效控制基坑变形。研究结果可为西安市其他地铁车站基坑支护结构的设计与施工提供借鉴。