节理岩体关键块体稳定的概率分析

基于地下岩体受节理面的控制,节理面的几何和力学参数随机分布,从而导致岩体系统具有高度不确定性,提出以关键块体理论为基础,考虑节理几何和力学参数随机性的岩体开挖可靠度分析方法,并给出了块体稳定的总失效概率评价模型。以澳大利亚阿德莱德地区一铜矿地质条件为例,以节理面倾角、倾向、摩擦系数和黏聚力为随机变量,通过Monte Carlo模拟和概率图方法,进行了岩体可靠度和失效概率的计算。最后,采用条件概率的分析方法,计算了单面滑动块体的总失效概率。计算结果表明,块体沿单面滑动并且出现的概率为11.0%,总的失效概率为3.85%,超过一般岩体工程可允许的风险水平,认为该方法可以作为评价块体可靠性的依据。     

基于广义子集模拟的土坡系统可靠度分析

如何有效地评价边坡的系统可靠度并识别出对边坡稳定性具有重要影响的关键滑面一直是边坡稳定性分析的关键问题。提出了基于广义子集模拟的边坡系统可靠度分析方法及代表性滑面识别方法,并推导了基于广义子集模拟的边坡系统可靠度计算公式及边坡中滑面对边坡系统失效的相对贡献量化公式。基于广义子集模拟计算结果,采用概率网络评价方法识别边坡代表性滑面。以一个双层黏性土坡和芝加哥国会切坡算例验证了所提方法的有效性。结果表明：提出的基于广义子集模拟的边坡系统可靠度分析方法可有效地估计边坡系统及其单一滑面的失效概率,对于具有低失效概率水平边坡可靠度的求解,其计算效率明显优于传统蒙特卡洛模拟方法。此外,对于单个失效模式而言,广义子集模拟与子集模拟计算效率相当。对于多个失效模式的失效概率计算问题,广义子集模拟不需要重复对每个失效模式失效概率进行计算,计算效率明显优于子集模拟。提出的代表性滑面选择方法是在系统失效概率及单滑面失效概率的高效计算基础上实现的,代表性滑动面能够较好地代表边坡系统失效,从而有效地降低了边坡系统失效概率对代表性滑面数目及代表性滑面失效概率估计准确性的依赖性。     

裂隙岩体抗滑稳定分析的概率方法

本文应用概率论和数理统计理论,探讨了裂隙岩体抗滑稳定分析方法。根据裂隙产状服从半球法线分布的假设,求得裂隙组集中产状的均值、方差和均值的可信区间。根据剪断试验资料,尝试用两点法确定抗剪参数的分布。采用极限平衡理论,应用蒙特卡洛法,计算坝肩岩体中可能滑动的块体的安全特征β和块体的稳定安全可靠度Pr,以此来评价该块体的稳定性。为了研究单个参数对稳定性的影响,在稳定性可靠度分析的程序中考虑了参数的灵敏度分析。最后给出了块体失稳的破坏概率Pf和安全系统Kc之间的关系,以便与常规的确定性分析加以比较。     

节理岩体的块体尺寸特征分析及其可靠度评价

通过对块体形成机制的讨论,根据岩体内节理面间距分布的随机性,分析了不同尺寸块体的出现概率。在计算块体的可靠度时,考虑了结构面的产状,粘结系数,磨擦系数等多个随机因素的影响。     

基于Copula函数的岩土结构物系统可靠度分析

研究了基于Copula函数的抗剪强度参数联合分布模型对岩土结构物系统可靠度的影响规律,揭示了抗剪强度参数间相关结构对岩土结构物系统可靠度影响的过程。介绍了不完备概率信息条件下基于Copula函数的抗剪强度参数联合分布模型构造方法,提出了Copula理论框架下岩土结构物系统失效概率计算的蒙特卡罗模拟方法,以典型岩土结构物如挡土墙和岩质边坡为例研究了Copula函数对系统可靠度的影响。结果表明:Copula函数为不完备概率信息条件下抗剪强度参数联合分布模型的构建提供了一种有效的工具。不完备概率信息条件下岩土结构物系统可靠度不唯一,不同Copula函数计算的系统失效概率差别非常大,这种差别在实际工程可靠度设计中应该引起重视。Copula函数对系统可靠度的影响分为两个机制不同的阶段,首先是参数间相关结构对系统中单一失效模式可靠度的影响,其次是每一个失效模式对系统可靠度的影响。     

锦屏二级水电站皮带机隧洞关键块体的概率分析

锦屏二级水电站皮带机隧洞岩体不连续面发育,确定隧洞开挖面是否可能产生关键块体具有重要实际意义。在对皮带机隧洞详细的地质调查和研究基础上,把随机概率模型引入关键块体理论,分析锦屏二级水电站皮带机隧洞关键块体的滑落概率,得出迹长和关键块体失稳的概率为反比关系,皮带机隧洞各主要结构面迹长为1~3m的概率较高,含结构面J2的关键块体相对稳定以及顶拱圈的加固将成为皮带机隧洞的支护重点等结论,为设计有效的加固方案提供了依据,具有重要的工程应用价值。     

CFG桩复合地基承载力可靠度分析

利用可靠度理论对从国内收集到的25组CFG桩复合地基承载力试验数据进行了概率统计处理。借助无量纲计算模式,计算不同载荷组合下CFG桩复合地基承载力的可靠度指标,并分析了各随机变量对可靠度指标的影响程度。为评价常 用经验公式 的可靠性提供一定的参考。     

基于可靠度理论的滑坡稳定性分析

基于可靠度理论,利用可靠度理论中的概率矩点估计法对延安市宝塔区卧虎山滑坡的稳定系数、可靠度和破坏概率进行了计算、分析。计算结果表明,基于可靠度理论滑坡稳定性计算能克服客观存在的土性参数的空间离散性、时间变异性,并把计算结果与传统稳定性计算结果进行了分析比较,证明了基于可靠度理论的滑坡稳定性计算方法的可靠性和可行性。     

重力式基坑支护系统的可靠性分析

本文分析了重力式基坑支护系统可能包含的多重破坏模式后,在考虑土性参数不确定性的情况下,运用系统可靠度理论对基坑支护系统的失效概率进行分析和计算。结果表明该方法能对基坑系统的稳定性作出较全面的评价。     

关键块体概率分析在复杂构造条件下大型地下工程开挖中的应用

锦屏一级水电站泄洪洞位于雅砻江右岸埋深大于100m的大理岩中,构造条件复杂,确定隧洞开挖面是否可能产生关键块体对工程安全具有重要意义。本文在对泄洪洞中导洞地质调查和研究基础上,将随机概率模型引入关键块体理论,分析关键块体的生成概率、体积大小与安全系数,得出关键块体形成概率服从负指数分布,主要取决于J②、J④组裂隙迹长的分布情况;关键块体的体积与主要结构面迹长成正比,最终收敛于结构面对关键块体完全切割时的关键块体体积;关键块体的安全系数随主要结构面迹长的增加而降低,但是同样收敛于结构面对关键块体的完全切割情况。为设计有效的加固方案提供了依据,具有积极的工程应用价值。     

基于自由面上环路对应节理无限切割的关键块体搜索

关键块体理论在评价工程裂隙岩体稳定性中得到了广泛应用。然而,一方面岩体中节理数量众多,关键块体的搜索将耗费较多机时;另一方面,极少数偶然出现的块体识别也会极大地增加计算量。因此,开发有针对性和灵活的关键块体搜索方法就非常重要。首先将研究区域分解成凸子区域,找出自由面上的闭合环路,然后利用环路的组成节理以及与其相交节理进行空间无限切割来识别该环路是否对应关键块体。该方法针对性强,能较好地适应人为规定的判别条件,如搜索楔形体以及后缘切割限定等,并能顺利实现凹面体的关键块体搜索,且编程实现简单。以某挂帮矿的顶柱为实例进行关键块体的搜索,验证了上述方法的可行性。     

大型地下洞室群关键块体地震响应分析

基于块体理论,针对地下厂房围岩中的关键块体,采用Newmark法进行了地震响应特征和稳定性评价方法的研究,研究表明,三向地震荷载组合作用下,在块体上引起的数值较大、作用时间很短的惯性力是关键块体产生永久位移的根本原因。块体在不同烈度地震荷载作用下其响应特征不只发生量的变化,还有运动规律、模式方面的变化。研究还发现,关键块体地震响应特征与其几何特征存在一定的相关性,并由此建立了大型地下洞室群围岩地震稳定分析的多因素、多指标评判方法。最后考虑结构面的退化效应,研究了块体地震响应特征关于结构面强度参数的敏感性,获得了一些有益的结论。     

三峡永久船闸高边坡关键块体的概率分析(英文)

基于传统块体理论对不连续岩体的稳定分析是建立在不连续面贯穿所研究岩体的假定基础上的，而实际的岩体不连续而长度是有限的。因此，本文将随机概率模型张块体理论，研究了三峡永久船闸边坡关键块体的肖落概率和块体的大小及分布密度，结果表明该方法具有重要的工程实用价值。     

Assessment of discontinuous rock slope stability with block theory and numerical modeling: a case study for the South Pars Gas Complex,Assalouyeh, Iran

In this study, a geotechnical model has been used to analyze the stability of a discontinuous rock slope. The main idea behind block theory is that it disregards many different combinations of discontinuities and directly identifies and considers critical rock blocks known as “key blocks”. The rock slope used as a case study herein is situated in the sixth phase of the gas flare site of the South Pars Gas Complex, Assalouyeh, Iran. In order to analyze the stability of discontinuous rock slopes, geotechnical modeling which was divided into geometrical sub-modeling and mechanical sub-modeling has been utilized. This model has been established upon the KGM (key-group method) algorithm which was based on the limit equilibrium method and block theory and prepared and coded by the Mathematica software. According to the results of the stability analysis, the analyzed slope was determined to be in the category of “needs attention,” and the security level, calculated through the FORM (first-order reliability method) analysis, was estimated to be 1.16. In order to verify the model, the results obtained from the model were compared with those of the UDEC software, which is a numerical method based on distinct components. As a conclusion, it was determined that the results of the model agreed well with those of the numerical method.     

岩质边坡关键块体的搜索方法及工程应用

工程边坡开挖所揭露的某些结构面组合块体在破坏原有静力平衡状态后,进行应力重新分配,进而块体会发生失稳、滑动等变形,甚至影响到整个边坡发生破坏,因此,结构面组合块体的稳定性是决定岩质边坡稳定的重要因素。本文通过对某工程开挖边坡地形和结构面三维实体模型的建立,实现了边坡结构面与开挖地形实体模型在AutoCAD平台上的可视化操作,剖切不同位置的二维图形预测分析了边坡开挖后可能存在的结构面组合块体,采用块体计算程序(Swegde)验证关键块体并进行稳定性评价。结果表明:三维实体模型及剖切技术与块体计算方法的结合,易于搜索关键块体。事实证明,该方法操作简便,计算结果准确,搜索方法具备可行性。     

A rigorous solution for the stability of polyhedral rock blocks

Block theory has been widely applied to stability analysis of rock engineering due to its clear concept and elegant geometrical theory. For a general block with multiple discontinuity planes, it is assumed that contact is only maintained on a single plane (single-plane sliding) or two intersecting planes (double-plane sliding) in block theory analysis. Since the normal forces and shear resistances acting on the other discontinuity planes are omitted, it can cause unreasonable estimations of block failure modes and incorrect calculation of factors of safety. In this study, a new method is presented that permits to consider the contribution of the normal forces and shear resistances acting on each discontinuity plane to the block stability. The proposed method meets all of the force-equilibrium and moment-equilibrium conditions and provides a rigorous solution for stability of general blocks with any number of faces and any shape. Some typical polyhedral blocks in rock slopes are analyzed using block theory and the proposed method. The results indicate that the traditional block theory may give a misleading conclusion for the predictions of stability and sliding direction of rock blocks when contact occurs on more than two discontinuity planes.     

The key blocks of unrolled joint traces in developed maps of tunnel walls

This paper presents a general method of key block analysis for cylindrical surfaces with numerous real or statistically produced joint traces. General tunnel curves, analytically represented, are unrolled to yield a ‘developed view’ on which the joint traces are continuous curves. Then, using extended block theory, the maximum key block regions are delimited from the curved polygons of the unrolled joint trace map. The methods discussed here apply to a cylindrical tunnel of any shape in section and in any orientation, including inclined tunnels and shafts. The trace maps for which the method applies can be generated statistically, as described herein, or surveyed from real traces on exposed tunnel walls. A brief introduction to the basic theory about tunnel key blocks is provided here so that this paper can be understood without reference to other papers on block theory.     

Block theory on the complex combinations of free planes

The core problem of block theory is to determine the finiteness, removability and mechanical stability of various blocks under different engineering structures based on dip angles, dip direction angles of discontinuities, frictional angles and the direction of the active resultant force. The practices of the classical block theory focus mainly on the convex blocks, assuming that joint surfaces and excavation faces are planar and extended infinitely in the rock mass. However, in practical engineering structures, the concave combinations of free planes (natural of excavated surfaces) are common. For example, the non-convex blocks usually exist in underground edges, corners and portals, and some of them are quite dangerous. In this paper, the characteristics of the non-convex blocks with complex combinations of free planes are analysed deeply based on the classical block theory. First, a non-convex block is seen as a combination of a series of convex blocks, then the criteria for finiteness and removability of the non-convex blocks are proposed, and finally, the identification algorithm is designed and validated by some cases. The results show that the method is effective and feasible and has important theoretical significance and practical value.