边坡稳定性评价结果的表达与边坡稳定判据

本文比较全面系统地总结分析了目前边坡工程中常用的各种稳定性评价结果的表达方式, 即各种边坡稳定判据。它们主要包括：(1)安全系数；(2)可靠度或破坏概率；(3)边坡岩体的位移、应力、位移速度等；(4)定性经验结论；(5)干扰能量；(6)声发射率等六种。在此基础上, 本文分析了各种判据的特点及其适用条件等。     

基于ABAQUS的降雨入渗条件下基坑边坡稳定性分析

降雨入渗条件下边坡的稳定性分析是评价边坡工程安全的主要依据,对工程施工具有重要的指导意义。以南水北调中线工程淇河倒虹吸基坑边坡为研究对象,基于ABAQUS有限元软件,考虑降雨入渗的边界条件,采用强度折减法求解了边坡的最大位移与安全系数,进行了边坡的稳定性分析。计算中,降雨入渗强度为15mm/h,持续时间为72h。计算结果表明:边坡一次开挖的水平方向最大位移、竖向方向最大位移、安全系数分别为0.26m、0.67m、1.650;边坡二次开挖后相应的计算结果分别为0.19m、0.62m、1.641;边坡三次开挖后相应的计算结果分别为0.20m、0.63m、1.639。定性分析与数值计算结果均表明,施工过程中,南水北调中线工程淇河倒虹吸基坑边坡是稳定的。本文的研究结果可以为该工程的施工提供理论依据,对降雨入渗时边坡的稳定性研究具有一定的借鉴意义。     

龙滩水电工程左岸B区边坡压脚工程效果分析

龙滩水电工程左岸蠕变体B区边坡的变形和稳定是工程安全的关键。根据边坡地质与稳定性分析,边坡的整体稳定性主要取决于坡脚岩体的稳定性,因此,B区边坡治理采取了压脚的工程措施。本文采用数值模拟方法(三维离散单元法)分析了压脚前后B区边坡的整体稳定性,结果表明B区边坡压脚工程可有效控制边坡岩体的变形。同时,数值分析结果也与边坡地表和深部位移动态监测结果一致,证明了压脚工程的显著效果。     

矿山边坡稳定性研究的回顾与展望

本文阐述了露天矿边坡工程的特点, 回顾了露天矿边坡稳定性研究及其取得的理论成果和进展, 指出露天矿边坡稳定性研究的特点, 提出相应的研究技术路线与方法。     

缓倾外层状结构边坡变形破坏模式及支护对策研究

高速公路开挖形成越来越多的工程边坡。缓倾外层状结构边坡作为一种典型的岩质边坡，一般情况下整体稳定性较好，但在特定的结构面组合状况下，开挖后也可能产生整体变形破坏。本文以软弱结构面和长大裂隙发育的公路工程边坡为例，通过岩体结构及边坡一定范围内已有边坡破坏现象的调查研究，采用工程地质类比和三维离散元法综合分析边坡变形破坏模式，并针对变形破坏模式的特点，提出支护对策。研究结果表明，结构面贯通坡体形成切割块体的后缘和侧缘边界时，缓倾外层状结构边坡可沿层面产生滑移-拉裂变形，若滑面与临空面具有一定夹角，边坡的变形可表现为旋转式滑移-拉裂；结构面组合控制的缓倾外层状结构岩质边坡稳定性受坡体中下部的关键块体控制，一旦关键块体失稳，将引起上部块体的连锁失稳，此类边坡变形控制的重点是对关键块体分布区域进行强支护；支护工程实施后的变形监测结果表明，基于变形破坏模式分析的边坡支护方案保证了边坡施工和运营过程中的安全。     

黄土填方高边坡变形破坏机制分析

本文依据西北某油田倒班基地黄土填方高陡边坡工程勘察, 研究了该边坡的变形破坏机制, 通过对边坡工程地质条件及变形破坏分析, 建立FLAC^3D地质模型, 采用数值模拟方法研究了边坡变形破坏机制。研究结果表明, 主要变形区或破坏区为陡坎周围至其沿坡面向下20～25m 的范围之间, 其破坏深度底界为全新世填土层Q4与原状黄土Q3接触面, 但要重点控制沿坡面向下20～25m 的范围之间的变形。数值模拟结果表明, 该边坡目前整体稳定性较好, 不会发生整体变形破坏。     

三峡库区边坡结构及失稳模式研究

随着三峡库区移民迁建工程的实施,移民城市与集镇建设和路桥工程施工形成了大量人工高边坡。据统计,移民迁建区已形成的高边坡多达3000余处,由于地质条件复杂,90%的边坡安全性达不到要求,对移民工程构成严重威胁。与我国其他地区不同,三峡移民区的边坡顶部、下部,甚至边坡中部大都要修建建筑物,因此,在治理边坡的同时,往往要考虑采用退层建筑方式利用边坡的问题,同时,三峡库区的城市功能以旅游开发为主,结合边坡整治来实施绿色工程和开发旅游资源非常重要。为了尽可能利用有限的土地资源,移民工程往往是依山就势,一般都采用前挡后挖的模式进行场平。本文系统研究了三峡库区边坡结构类型,划分为顺层边坡、平缓软硬岩层互层边坡、滑崩堆积体边坡、溶塌角砾岩边坡、层状碎裂岩体边坡等,并对典型边坡开挖前后变形破坏过程进行了研究。结合三峡移民迁建工程,介绍了基于防护的边坡利用技术,并进行了示范。     

高层建筑深基坑边坡支护的主要问题与对策

本文总结了工程实例经验教训，提出了高层建筑深基坑边坡支护的主要问题与对策。     

广东高速公路路堑边坡失稳原因与防治分析

通过大量实际工程实例的综合分析研究,论证了近年来广东高速公路路堑边坡失稳的主要原因、防治设计理念、治理程序、边坡监测和应急措施,认为在水及气候条件、地层岩性、地质构造、人工活动等方面的存在不利因素。由此,提出了由地质测绘、工程地质勘察、稳定性综合分析、方案设计、施工图设计组成的五阶段,并通过实例分析了路堑边坡的防治设计措施。     

加权函数组合预测边坡变形模型的研究

边坡变形监测是边坡监测的主要内容之一,其变形预测问题是边坡工程中主要技术难题之一。考虑边坡位移变形预测模型的局限性,如神经网络预测方法需要大量的实测数据作为学习样本,灰色系统模型要求原始数据序列必须满足指数规律,且数据序列变化速度不能太快等。建立了边坡变形反向传播神经网络预测模型,同时给出了灰色GM(1,1)边坡预测模型。提出边坡的神经网络与灰色系统加权函数组合预测模型,采用动态规划解法,将原模型转化为多阶段决策问题,使组合预测误差的平方和最小,得到组合权重,这样得到的变形预测结果的精度将大大提高,弥补了单一方法的局限性,满足工程预测的需要。通过边坡实例加以验证,加权函数组合预测模型的预测结果精度有一定提高,能够与实际监测数据相吻合,达到准确预测的目的。     

基于实验的数值反演的滚动轮胎稳态温度场的有限元分析

根据轮胎温度场的单向解耦分析思想,形成了一个基于ABAQUS程序的轮胎稳态温度场的分析方法,单向解耦过程分为变形、损耗、热传导三个分析过程。变形分析中,采用了平衡态的超弹性材料模型;损耗分析中,依据变形分析获得的应力应变场,结合材料粘性损耗特性来获得损耗能量;热传导分析中,依据实测的轮胎胎侧温度场,提出了一种基于实验的数值反演方法来确定胎侧的对流热边界条件。由于轮胎胎侧的形状和结构细节,其对流热边界不同于旋转平圆盘的对流热边界,本文的数值反演方法避免了实测胎侧对流热交换系数的困难。     

基于区间分析的工程结构不确定性研究现状与展望

随机分析方法、模糊分析方法是已经广泛使用的工程结构不确定性分析方 法, 近年来区间分析方法逐渐为人们所熟知并成为是一种新的工程结构不确定性分析方法, 它主要用来研究具有区间特性的工程结构. 区间分析方法在统计信息不足以描述不确定参数 的概率分布或隶属函数、工程单位仅提供不确定参数的区间范围而想获得结构响应的区间范 围时就发挥了其优点. 综述了区间分析方法及其在工程结构不确定性分析中的应用状 况, 将基于区间分析的工程结构不确定性问题研究归结为以下4个方面: 不确定性结构系统 的区间有限元分析; 基于区间的非概率可靠性分析; 工程结构区间反演分析; 基于区间参数 的结构优化设计. 分析评价了国内外在这几个方面的研究成果及其最新进展, 同时指出目前 研究中存在的问题和研究的方向.     

Excitation symmetry analysis method (ESAM) for calculation of higher order non-linearities

A non-linear system with 3rd order non-linearity is fully characterized using symmetry analysis (SA) applied to the excitation, as it is done in 2nd order non-linear systems using the pulse inverted method. Symmetry analysis is performed using irreductible representations and the character table of C₃ rotation point group, which leads to the construction of three eigen-excitations allowing extraction of the 3rd order non-linearity parameter without the perturbation of fundamental and 2nd order terms. Validation of this concept is based on excitation symmetry analysis method (ESAM) which was tested on simulated noisy signals and compared with classical spectral analysis.     

Theoretical Analysis of Viscous Coupling in Two-phase Flow through Porous Media

Theoretical analysis is presented to quantify the viscous coupling effect in two-phase flow through porous media. The analysis is based on the principle of potential difference equations as well as on the interfacial contact area and partition concept. The analysis shows that viscous coupling effect is negligible throughout the normalized saturation range. The expression, Xϕ ², was developed for the quantification of the parameter that controls the amount of viscous coupling, where X was theoretically found to have a maximum value of 2.     

Two-dimensional moiré method and grid method using Fourier transform

Formerly, the authors presented one-dimensional strain analysis by a moiré method using a Fourier transform. In the present work, the method is extended to two-dimensional strain analysis. The analysis is completely automated by introducing digital image processing. All of the laborious and subjective procedures required in the classical and conventional moiré method, such as separation of the two gratings, fringe-sign determination, fringe ordering and fringe interpolation, are completely eliminated; and objective, fast and accurate analysis can be made.currently Engineer, Kansai Electric Power Co. Inc.Paper was presented at the 1988 SEM Spring Conference on Experimental Mechanics held on June 5–10 in Portland, OR.     

Nonlinear shell-type to beam-type fea simplifications for composite frp poles

This paper presents a semi-analytical finite element analysis of pole-type structures with circular hollow cross-section. Based on the principle of stationary potential energy and Novozhilov’s derivation of nonlinear strains, the formulations for the geometric nonlinear analysis of general shells are derived. The nonlinear shell-type analysis is then manipulated and simplified gradually into a beam-type analysis with special emphasis given on the relationships of shell-type to beam-type and nonlinear to linear analyses. Based on the theory of general shells and the finite element method, the approach presented herein is employed to analyze the ovalization of the cross-section, large displacements, the P-Δ effect as well as the overall buckling of pole-type structures. Illustrative examples are presented to demonstrate the applicability and the efficiency of the present technique to the large deformation of fiber-reinforced polymer composite poles accompanied with comparisons employing commercial finite element codes.     

Bifurcation buckling of shells of revolution including large deflections,plasticity and creep

A summary is first presented of the conceptual difficulties and paradoxes surrounding plastic bifurcation buckling analysis. Briefly discussed are nonconservativeness, loading rate during buckling, and the discrepancy of buckling predictions with use of J₂ flow theory vs J₂ deformation theory. The axisymmetric prebuckling analysis, including large deflections, elastic-plastic material behavior and creep is summarized. Details are given on the analysis of nonsymmetric bifurcation from the deformed axisymmetric state. Both J₂ flow theory and J₂ deformation theory are described. The treatment, based on the finite-difference energy method, applies to layered segmented and branched shells of arbitrary meridional shape composed of a number of different elastic-plastic materials. Numerical results generated with a computer program based on the analysis are presented for an externally pressurized cylinder with conical heads.     

Heat flux-flow coupling effects in the stability of vapour generators

A study has been carried out to investigate the dynamics of two-phase flow in vapour generators, with special reference to the effect of flux-flow couplings on density wave instability. A distributed parameter time-varying theoretical analysis of the conservation equations, together with the constitutive laws of two-phase flow, has been derived. The analysis takes into account the dynamics of the heater wall, revealing the predominant role of the heat flux-flow couplings on the stability of the system. A digital computer program has been written and developed to implement the theoretical analysis. Results from the analysis are used for comparison with the available data and the effect of the flux-flow couplings on instability is demonstrated and discussed. These results are also used to explain the dynamic behaviour of a specially constructed “Arcton-113”¹ closed loop comprising a helical, electrically heated, once-through vapour generator in a parallel channel arrangement with high thermal capacitance. Kopplungseffekte zwischen Wärmefluß und Strömung bei der Stabilität von Dampferzeugern     

Photoelastic Analysis of Edge Residual Stresses in Glass by Automated “Test Fringes” Methods

Since the glass is a birefringent material, the analysis of residual stress in glass is usually carried out by means of photoelastic methods. This paper considers the automation of the “test fringes” method which is based on the use of a Babinet compensator or of a beam subjected to bending. In particular, two automated methods are proposed: the first one is based on the use of the centre fringe method in monochromatic light and the second one is based on the use of RGB photoelasticity in white light. The proposed methods have been applied to the analysis of membranal residual stresses in some tempered glasses, showing that they can effectively replace manual methods of photoelastic analysis of residual stresses in glass.     

Thermoelastic investigations for fatigue life assessment

An investigation is presented on the suitability and accuracy of a thermoelastic technique for the analysis of fatigue cracks. The stress intensity factor ranges ΔK _I and ΔK _II are determined from thermoelastic data recorded from around the tip of a sharp slot in a steel specimen under biaxial load, in order to assess the accuracy of the technique. ΔK _I and ΔK _II are determined to within 4% and 9% of a theoretical prediction, respectively. The results from a similar test on a fatigue crack under biaxial load are also presented. These show that thermoelastic stress analysis is a rapid and accurate way of analyzing mixed-mode fatigue cracks. A discussion is given on the potential of thermoelastic stress analysis of propagating cracks.