Limit analysis on seismic stability of anisotropic and nonhomogeneous slopes with anti-slide piles

This study employs the limit analysis method to evaluate the seismic stability of anisotropic and nonhomogeneous slopes stabilized with anti-slide piles. The pseudo-static approach is used to simplify the earthquake load. The yield seismic acceleration factor is obtained from the optimization procedure and the results are verified with the published data. Then, the seismically-unstable slope is reinforced with anti-slide piles, and the seismic stability of the reinforced slope is explored. The results show that the anisotropy and nonhomogeneity of soils have significant effects on the stabilizing force required from the anti-slide piles and the optimal location of the pile is near the toe of the slope.     

边坡强度参数对于稳定性影响的极限平衡法分析

为了研究岩土体抗剪强度参数对边坡稳定性的影响,通过理论推导和Bishop极限平衡法计算,分别改变岩土体的粘结力c和内摩擦角,探讨边坡安全系数和滑动面的变化.结果表明：粘结力或内摩擦角改变时,边坡的安全系数将发生变化,而滑动面的变化受函数η-c的影响,η-c与粘结力和内摩擦角有关.当η-c为定值时,滑动面不随抗剪强度参数的变化而变化;当η-c增大时,边坡的滑动面从近坡面逐渐向边坡内部移动;反之,η-c减小时,边坡的滑动面从边坡内部向近坡面移动.研究结果为边坡稳定性分析的理论和实践研究提供了参考.     

Limit analysis for the seismic stability of three-dimensional rock slopes using the generalized Hoek-Brown criterion

The parameters that influence slope stability and their criteria of failure are fairly understood but over-conservative design approaches are often preferred, which can result in excessive overburden removal that may jeopardize profitability in the context of open pit mining. Numerical methods such as finite element and discrete element modelling are instrumental to identify specific zones of stability, but they remain approximate and do not pinpoint the critical factors that influence stability without extensive parametric studies. A large number of degrees of freedom and input parameters may make the outcome of numerical modelling insufficient compared to analytical solutions. Existing analytical approaches have not tackled the stability of slopes using non-linear plasticity criteria and three-dimensional failure mechanisms. This paper bridges this gap by using the yield design theory and the Hoek-Brown criterion. Moreover, the proposed model includes the effect of seismic forces, which are not always taken into account in slope stability analyses. The results are presented in the form of rigorous mathematical expressions and stability charts involving the loading conditions and the rock mass properties emanating from the plasticity criterion.     

水力学作用下顺层岩质边坡稳定性研究

采用静水压力在总水位1/2处达到最大作为静水压力的新假设,并对结构面上的动水压力进行了详细的推导计算,完善了影响边坡稳定的水力学理论.当坡顶面出现竖直张裂缝时,张裂缝中的水深影响结构面上静水压力和动水压力的大小,可用张裂缝中的临界水深作为边坡破坏的依据.通过实例分析,结构面和张裂缝中的静水压力对边坡的稳定性影响较大,而结构面上的动水压力对边坡的稳定性影响较小.在给定边坡条件下,静水压力使边坡的稳定系数降低了16.8%;动水压力使边坡的稳定系数降低了1.2%.     

Three-dimensional stability analysis of anisotropic and non-homogeneous slopes using limit analysis简

A method of three-dimensional loaded slope stability for anisotropic and nonhomogeneous slopes was presented based on the upper-bound theorem of the limit analysis approach. The approach can be considered as a modification and extension of the solutions. The influences of friction angle, anisotropy factor, nonhomogeneous factor, slope angle, ratio of width to depth, and load on the slope crest were investigated. The results show that solutions are suitable to deal with the purely cohesive soils and frictional/cohesive soils, isotropic and anisotropic, homogeneous and nonhomogeneous, loaded and unloaded cases.     

黏土边坡稳定性分析的一种快捷方法

为减少黏土边坡稳定性分析手工试算的工作量,提出一种快捷方法,先通过最危险的平面滑动面来确定滑动体的大小,在保持滑动体大小不变的情况下,通过简单的迭代计算将平面滑动面调整为实际滑动面,如圆弧滑动面等,并求出相应的稳定安全系数,用以判断边坡的稳定性．结果表明,本法所求得的边坡稳定安全系数均接近或小于文献所给出的结果．     

Limit equilibrium method for slope stability based on assumed stress on slip surface

In the limit equilibrium framework, two- and three-dimensional slope stabilities can be solved according to the overall force and moment equilibrium conditions of a sliding body. In this work, based on Mohr-Coulomb(M-C) strength criterion and the initial normal stress without considering the inter-slice(or inter-column) forces, the normal and shear stresses on the slip surface are assumed using some dimensionless variables, and these variables have the same numbers with the force and moment equilibrium equations of a sliding body to establish easily the linear equation groups for solving them. After these variables are determined, the normal stresses, shear stresses, and slope safety factor are also obtained using the stresses assumptions and M-C strength criterion. In the case of a three-dimensional slope stability analysis, three calculation methods, namely, a non-strict method, quasi-strict method, and strict method, can be obtained by satisfying different force and moment equilibrium conditions. Results of the comparison in the classic two- and three-dimensional slope examples show that the slope safety factors calculated using the current method and the other limit equilibrium methods are approximately equal to each other, indicating the feasibility of the current method; further, the following conclusions are obtained: 1) The current method better amends the initial normal and shear stresses acting on the slip surface, and has the identical results with using simplified Bishop method, Spencer method, and Morgenstern-Price(M-P) method; however, the stress curve of the current method is smoother than that obtained using the three abovementioned methods. 2) The current method is suitable for analyzing the two- and three-dimensional slope stability. 3) In the three-dimensional asymmetric sliding body, the non-strict method yields safer solutions, and the results of the quasi-strict method are relatively reasonable and close to those of the strict method, indicating that the quasi-strict method can be used to obtain a reliable slope safety factor.     

水平阶跃荷载作用下单层球面网壳结构的动力稳定性

以具有实际工程意义的40m跨度K8型单层球面网壳为研究对象，在分析单层网壳结构在水平阶跃荷载作用下动力失稳过程的基础上，探讨了网壳结构的动力稳定性临界荷载的判定方法，研究了矢跨比、弹塑性、阻尼和初始几何缺陷等因素对网壳结构动力稳定性临界荷载的影响，并进一步分析了水平阶跃荷载与水平静荷载及水平地震荷载作用下的稳定性临界荷载之间的关系。     

Comprehensive analysis of slope stability and determination of stable slopes in the Chador-Malu iron ore mine using numerical and limit equilibrium methods

One of the critical aspects in mine design is slope stability analysis and the determination of stable slopes. In the Chador Malu iron ore mine, one of the most important iron ore mines in central Iran, it was considered vital to perform a comprehensive slope stability analysis. At first, we divided the existing rock hosting pit into six zones and a geotechnical map was prepared. Then,the value of MRMR (Mining Rock Mass Rating) was determined for each zone. Owing to the fact that the Chador-Malu iron ore mine is located in a highly tectonic area and the rock mass completely crushed, the Hock-Brown failure criterion was found suitable to estimate geo-mechanical parameters. After that, the value of cohesion (c) and friction angle (e) were calculated for different geotechnical zones and relative graphs and equations were derived as a function of slope height. The stability analyses using numerical and limit equilibrium methods showed that some instability problems might occur by increasing the slope height.Therefore, stable slopes for each geotechnical zone and prepared sections were calculated and presented as a function of slope height.     

竖向恒载对框架结构动力稳定性影响研究

以框架结构为例,建立了结构动力稳定性分析的基本模型,提出了利用动力响应的敛散性来判断结构动力稳定性的具体方法.通过算例分析,给定不同的竖向恒载值,得到框架结构在水平动力荷载作用下的临界荷载值,结果表明,竖向恒载对动力稳定性有明显影响,但动力临界荷载与相应静力临界荷载的比值变化不大.     

Pseudo-dynamic analysis of seismic stability of reinforced slopes considering non-associated flow rule

The required reinforcement force to prevent instability and the yield acceleration of reinforced slopes are computed under seismic loading by applying the kinematic approach of limit analysis in conjunction with the pseudo-dynamic method for a wide range of soil cohesion, friction angle, dilation angle and horizontal and vertical seismic coefficients. Each parameter threatening the stability of the slope enhances the magnitude of the required reinforcement force and vice versa. Moreover, the yield acceleration increases with the increase in soil shear strength parameters but decreases with the increase in the slope angle. The comparison of the present work with some of the available solutions in the literatures shows a reasonable agreement.     

恒载荷下TiNi和TiNiCu形状记忆合金弹簧的热稳定性

TiNi基形状记忆合金弹簧是一种有广阔应用前景的形状记忆合金驱动元件.研究了在电流加热方式下,不同加热温度,不同恒载荷作用下TiNi和TiNiCu记忆合金弹簧的热稳定性.研究表明,恒定载荷下,最初的几次循环后,弹簧的行程变小,而在循环次数超过一定次数后,弹簧的行程不随着循环次数的增加而发生明显变化.对于TiNi和TiNiCu记忆合金弹簧,过热和过载均会向弹簧中引入不可逆的塑性变形,导致其热稳定性的下降.由于Ti3Ni4相粒子的析出强化了基体,在恒载荷下,TiNi合金弹簧较TiNiCu合金弹簧显示出更加良好的热稳定性.     

外压容器稳定性的可靠性分析

利用可靠性分析方法.对外压容器进行了可靠度的分析讨论,并给出了计算实例.为外压容器的设计及失效分析提供了理论依据.     

低周反复荷载下钢筋混凝土异型节点的损伤分析

基于钢筋混凝土异型节点的受力特点和破坏模式，提出了一种将其视为子结构进行损伤分析的方法，并建立了适用于低周反复荷载下钢筋混凝土异型节点的损伤模型。通过与试验结果相对比，证明，钢筋混凝土异型节点的损伤分析不仅丰富了伪静力条件下的实验内容，而且为该类节点受力机理和破坏过程的研究提供了一种行之有效的手段。研究表明，在伪静力条件下钢筋混凝土异型节点的总体损伤是由其内部各主要控制因素的损伤共同贡献而成，在加载之初受混凝土损伤影响较大，而在加载中后期则主要由节点核心区纵筋及箍筋的损伤起控制作用。     

基于矢量和法的边坡三维极限平衡稳定分析法

对于具有复杂几何特征的边坡问题, 用二维极限平衡理论难以得到与实际相应的分析结果.基于矢量和法安全系数定义,提出了能满足所有条柱3个力的平衡和滑坡体3个整体力矩平衡的严格通用极限平衡分析法.通过侧向剪力系数和侧向剪力分布函数对条间力进行假定,考虑所有条间剪力对安全系数的影响.利用滑体力的平衡条件和边界条件分别得到条柱各行和各列的安全系数,再利用滑体整体力矩平衡条件确定侧向剪力系数.将条柱底面剪力矢量和的反方向作为潜在滑动方向,通过抗滑力和滑动力在其上的投影之和之比确定整个坡体的矢量和安全系数.典型算例验证了方法的合理性,计算结果表明,完全考虑条间力作用将提高边坡的稳定安全系数.     

降雨入渗条件下分层非饱和土质边坡随机反分析

基于时变数据参数随机反分析理论,采用马尔可夫链蒙特卡罗方法(Markov chain Monte Carlo simulation,MCMC法),建立了分层边坡非饱和渗流随机反分析模型.以香港东涌某天然坡地降雨入渗现场试验为案例,建立单层土和双层土非饱和渗流模型,利用DREAM算法对时变降雨条件下非饱和土渗流模型参数进行随机反演,研究了单层土和双层土模型参数后验分布和预测效果.结果表明,参数后验分布变异性较先验分布减小,与单层土模型相比,双层土模型能缩减更多的参数不确定性,校准期内置信区间更窄,验证期内预测与实测值吻合程度较高.     

渗流对土质边坡稳定性影响分析

根据强度折减有限元法,采用Mohr-Coulomb屈服准则及关联流动法则,以收敛性准则结合特征点位移突变准则作为边坡失稳判据,研究了无渗流、渗流应力耦合及非耦合情况的土质边坡的稳定性.研究表明:1)渗流对边坡稳定性的影响十分明显,无渗流及渗流应力耦合两种情况的均质边坡的最小安全系数分别为1.84、1.115;2)渗流应力耦合效应对边坡稳定的影响极其不利,应该采用耦合方法评价边坡的稳定性,耦合、非耦合情况的最小安全系数分别为1.115、1.28.     

西安白鹿塬北缘黄土边坡稳定的可靠度分析

在西安白鹿塬北缘实测了14个黄土自然边坡断面,建立了地质模型,通过采样测试并收集已有的测试资料,获得了各时代黄土地层的物理力学参数,将Morgenstern-Price法稳定性计算公式作为极限状态方程,分别采用Monte-Carlo法和Duncan法进行了边坡稳定的可靠度分析。结果表明:采用Monte-Carlo法和Duncan法得到的14个边坡稳定系数分别为1.11～1.41和1.09～1.33,显示这些边坡处于基本稳定—稳定状态; 采用上述两种方法得到的边坡可靠指标分别为0.56～1.79和0.39～1.60,得到的失效概率分别为3.4%～29.0%和5.5%～34.8%,并且共有75%的边坡失效概率大于10%,失效可能性较大。统计结果表明:白鹿塬区边坡的坡高和坡度存在负相关性。低而陡的边坡潜在最危险滑面剪出口较高,失效概率较小; 坡高达到50 m及以上时,边坡高而缓,剪出口较低,失效概率较大,其中河流下切深,有N₂泥岩出露的极高边坡,稳定性最差。Duncan法求解的稳定系数略小于Monte-Carlo法求得的结果,而前者求解的失效概率略大于后者,两种方法计算结果较为接近。由于Duncan法理论简单,计算量小,更宜于在实际工程中应用。