Three-dimensional RITSS large displacement finite element method for penetration of foundations into soil

The Remeshing and Interpolation Technique with Small Strain (RITSS) approach has been developed to deal with 3-D geotechnical problems in this paper. Unstructured 20-node hexahedral element is found to work well for predicting collapse loads accurately for 3-D undrained geotechnical problems involving material incompressibility. Remeshing is automatically accomplished by ANSYS program. With remeshing and interpolation, small fluctuations appear in the load–deformation results. In order to minimize these fluctuations, different increment sizes and remeshing frequencies are explored. Meanwhile, various 3-D interpolation methods are compared, and the unique element division method is found to work best. The results of two numerical applications are presented for a 3-D strip footing penetrating deeply into uniform clay and a square foundation into normally consolidated clay. The computed bearing capacity responses are compared with other numerical or conventional results. The results show that the present method is accurate and efficient for 3-D large displacement foundation penetration problems.     

珠海某大厦深基坑支护工程监测实例

珠海某大厦深基坑原始地貌单元属剥蚀残丘,后经人工挖填整平。基坑开挖深度为10 m。基坑施工中共设置坑顶位移监测点10个,侧向水平位移观测孔4个,地下水位观测井4口等,对基坑进行实施监测,保证了施工的顺利进行。     

多通道滑坡位移监测仪的研制

文章提出一种滑坡表层位移监测方法,设计并研制了四通道位移监测仪器。该仪器选用特制的拉杆位移传感器完成滑坡位移传感,单片机逻辑控制实现位移监测数据动态显示,并对大量程、急速位移滑动做声光预警,监测数据自动保存。文章阐述了其工作原理及软硬件设计思路,并介绍了位移监测仪在三峡万州库区塘角村1号滑坡的野外应用实验。     

紧邻地铁的深基坑支护施工技术

深圳星河酒店基坑两侧紧邻地铁,周边环境复杂,开挖深度达18．6m。该基坑支护主要为钻孔及人工挖孔咬合桩,为适应基坑周围环境的多样性,还采用了锚杆、植筋墙,利用结构本体换撑,静爆加切割拆除内支撑等工艺。分析了该基坑不同部位水平位移的原因,及基坑变形特征。经监测,基坑变形各项指标均在设计的控制标准之内,取得了令人满意的基坑支护效果。可供类似工程借鉴。     

四川宣汉天台滑坡的变形位移特征及形成机理

天台滑坡是在平缓斜坡和平缓岩层区发生的特大型土质滑坡,以多级分块滑动为主要特点。滑体的水平位移量前部最大,向后部逐渐减小。根据滑坡体上槽、脊相间的复杂的台阶式地形概括出5种滑坡次级变形模式,分析了滑坡产生多级分块滑动的主要条件,建立了水压力推动滑坡产生分块滑动的成因模式。     

PPP网解UPD模糊度固定技术监测尼泊尔Ms8.1级地震对中国珠峰地区及周边地震同震位移

利用UPD模糊度固定技术无需顾及基线解算基站地震所带来的影响,可以进行高精度非差PPP解算,"真实"获取地震周边地区GNSS站点高精度同震位移变化。为此,本文利用"国家基准一期工程""中国大陆构造环境监测网络"以及国家测绘地理信息局在珠峰周边所观测的GNSS观测资料,基于UPD模糊度固定技术高精度非差解算2015年4月25日尼泊尔Ms8.1级地震对我国珠峰地区及周边地震同震位移影响。首先,本文选取全国及周边IGS均匀分布、站点稳定、远离震区的GNSS连续观测网络数据计算卫星端的宽、窄巷UPD,采用PPP网解UPD模糊度固定技术,对解算地震区域内的GNSS测站的载波相位模糊度进行固定,得到无模糊度的精确相位观测值,进行高精度非差PPP解算;通过对平静日IGS测站数据处理与ITRF2008历元坐标对比分析,验证了该方法的精确性;最后,对2015年4月25日、5月12日地震以及地震前后数据,进行了UPD模糊度固定技术的非差PPP解算,分析了中国珠峰地区及周边GNSS站的同震位移;同时也分析了中国珠峰地区在2005—2015年10年的位移变化情况。UPD模糊度固定技术整网解算的方法也证实了能够为GNSS用于监测地震同震位移等,提供了一种精确、可靠的技术手段。     

一种高精度的基坑水平位移监测方法探讨

将CPⅢ(高速铁路轨道控制网)平面控制测量的自由测站施测方法应用到基坑水平位移变形监测中,其特点是根据施工现场情况选择任意合适的地点架设测站,避免了施工环境对测量工作的影响和仪器的对中误差。介绍了Helmert方差分量估计定权原理和置平平差原理,通过自编程序完成了基坑变形监测的仿真计算。计算结果证明:利用自由测站采集观测数据,Helmert方差分量估计定权约束平差和置平平差均能够高精度地得到毫米级的基坑变形量,可以应用到基坑水平位移变形监测中。     

高速公路类土质路堑边坡施工期变形监测预警探讨

高速公路类土质路堑边坡是边坡领域的一种重要类型,在工程特性方面与土质边坡或岩质边坡具有明显差异。深入认识该类边坡的工程特性和失稳机理,对该类边坡施工期间的安全建设以及正常运营期间安全评估具有重要意义。基于高速公路类土质路堑边坡工程地质特点、边坡变形影响因素,结合盘兴高速公路K5滑坡变形监测预警实例,提出了采用位移速度比率作为预警参考值的滑坡预警方法,并在松铜一标ZK5 410～485段左侧边坡成功预警,避免了人员伤亡,减轻了经济损失。为类土质路堑边坡工程设计、工后防治、安全运营提供指导。     

Bivariate simulation using copula and its application to probabilistic pile settlement analysis

This paper aims to propose a procedure for modeling the joint probability distribution of bivariate uncertain data with a nonlinear dependence structure. First, the concept of dependence measures is briefly introduced. Then, both the Akaike Information Criterion and the Bayesian Information Criterion are adopted for identifying the best‐fit copula. Thereafter, simulation of copulas and bivariate distributions based on Monte Carlo simulation are presented. Practical application for serviceability limit state reliability analysis of piles is conducted. Finally, four load–test datasets of load–displacement curves of piles are used to illustrate the proposed procedure. The results indicate that the proposed copula‐based procedure can model and simulate the bivariate probability distribution of two curve‐fitting parameters underlying the load–displacement models of piles in a more general way. The simulated load–displacement curves using the proposed procedure are found to be in good agreement with the measured results. In most cases, the Gaussian copula, often adopted out of expedience without proper validation, is not the best‐fit copula for modeling the dependence structure underlying two curve‐fitting parameters. The conditional probability density functions obtained from the Gaussian copula differ considerably from those obtained from the best‐fit copula. The probabilities of failure associated with the Gaussian copula are significantly smaller than the reference solutions, which are very unconservative for pile safety assessment. If the strong negative correlation between the two curve‐fitting parameters is ignored, the scatter in the measured load–displacement curves cannot be simulated properly, and the probabilities of failure will be highly overestimated. Copyright © 2011 John Wiley & Sons, Ltd.     

Fast multipole displacement discontinuity method (FM‐DDM) for geomechanics reservoir simulations

The displacement discontinuity method (DDM) is frequently used in geothermal and petroleum applications for modeling the behavior of fractures in linear‐elastic rocks. The DDM requires O(N²) memory and O(N³) floating point operations (where N is the number of unknowns) to construct the coefficient matrix and solve the linear system of equations by direct methods. Therefore, the conventional implementation of the DDM is not computationally efficient for very large systems of cracks, often limiting its application to small‐scale problems. This work presents an approach for solving large‐scale fracture problems using the fast multipole method (FMM). The approach uses both the DDM and a kernel‐independent version of the FMM along with a preconditioned generalized minimal residual algorithm to accelerate the solution of linear systems of equations using desktop computers. Using the fundamental solutions for constant displacement discontinuity in a two‐dimensional elastic medium, several numerical examples involving fracture networks representing fractured reservoirs are treated. Numerical results show good agreement with analytical solutions and demonstrate the efficiency of the FMM implementation of the DDM for large‐scale simulations. Copyright © 2015 John Wiley & Sons, Ltd.