Stability analysis of rock slopes with a modified Hoek–Brown failure criterion

The original Hoek–Brown (HB) failure criterion was used to analyse the stability of rock slopes. For highly fractured rock, the original HB failure criterion has been modified, but its effect on the stability of rock slopes has not been studied. Within the framework of the kinematical approach of limit analysis, this paper computes the rigorous upper bounds of stability factors of homogeneous rock slopes with the modified HB failure criterion under the plane strain condition, by employing a ‘generalized tangential’ technique. In such technique, instead of using the modified HB failure criterion, a series of linear failure surfaces tangent to the actual non-linear failure surface are utilized to derive the upper bound solutions, incorporating a new parameter n ranging from 0.5 to 0.65. The numerical results are compared with other published solutions for the case of n=0.5. The effects of the n on the stability factors of rock slopes are discussed. Copyright © 2004 John Wiley & Sons, Ltd.     

非线性破坏准则下的边坡稳定塑性极限分析

利用塑性分析上限定理,考虑岩土介质本身的非线性破坏准则,对各种不同破裂面边坡稳定性分析进行研究。针对破坏边坡破裂面不同,采用外切直线法来分析其上限解,推导出非线性破坏准则下的边坡稳定性系数计算公式,并对较复杂的对数螺旋线破裂面边坡提出初始切线法,较好地求出塑性极限分析上限解。将在非线性破坏准则下按对数螺旋线破裂面推导出的塑性极限分析上限解运用于实际边坡工程,其结果与精确塑性分析结果非常接近,为非线性破坏准则下的边坡稳定塑性极限分析提供了一条新的思路与方法。     

块状岩体边坡倾倒破坏稳定性分析

基于Scavia模型，该文给出了由台阶状破坏面上柱状岩块所组成的具有潜在旋转-倾倒破坏模式的完整改进理论解。新的闭解允许经典模型中两组节理交汇所形成的直角可为任意角度，锚固力和地震作用力为任意方向，水压力可以是块体高度内的任意值。为了展示一般的运用方法，也为了说明倾倒破坏模式的普遍规律，该文接着给出了可变几何外形的若干理想边坡倾倒破坏的稳定性分析，其分析结果可以用来指导倾倒破坏边坡的加固处理     

基于非线性破坏准则的边坡稳定性极限分析

上限定理是求解岩土工程问题的有效工具。以上限定理为理论基础,分析边坡的稳定性问题,并考虑了岩土材料破坏准则的非线性特性。在非线性Mohr-Coulomb破坏准则下,采用条分法与极限分析上限法相结合的方法,对边坡稳定性进行分析。通过切线法引入非线性强度参数 、 ,推导了岩土材料在非线性破坏准则下的相关联流动法则,建立功能方程,推导了边坡直线滑裂面、折线滑裂面和光滑曲线滑裂面安全系数F的计算方程。采用数学规划法计算后与工程实际中常用的边坡稳定性分析方法进行对比,并获得安全系数F =1.0时的稳定性系数Ns。与已有的研究成果进行比较分析,结果表明了该方法的正确性及优越性     

Stability analysis of seismic slopes with cracks

Earthquakes can trigger slope instability, especially in the case of slopes with cracks. Studies of slope stability rarely account for the presence of cracks. In this study, the upper bound limit analysis technique and the pseudo-static method were used to examine the stability of homogeneous slopes with cracks subjected to seismic loading. A series of stability charts for slope inclinations of 2:1 (β = 63.4°), 1:1 (β = 45°), 2:3 (β = 33.7°), and 1:2 (β = 26.6°) (vertical to horizontal) and internal friction angles, φ, of 10°, 20°, 30°, and 40° are presented. These charts should be useful for readily determining the stability number (critical slope height), the critical crack depth, and the region affected by cracks for cracks of known depth but unknown location, cracks of known location but unspecified depth, and cracks of unspecified depth and location.     

非线性破坏准则下边坡稳定性极限分析斜条分法

考虑坡顶均布荷载和地震效应典型情况下,将边坡滑体进行任意斜条块划分,建立了具有倾斜界面的多块体破坏模型。基于极限分析上限法和非线性摩尔-库仑破坏准则,考虑岩体内正应力的不均匀性,引入多点切线法和强度折减法推导得出边坡临界破坏状态下的安全系数Fs通用计算公式。采用序列二次规划法对安全系数Fs的目标函数进行最优化计算,并与既有研究成果进行对比分析,其结果具有较好的一致性,相对误差不超过3.565%,表明了该方法的正确性。同时对比传统单点切线法计算结果,多点切线法较单点切线法获得的边坡安全系数值偏小,表明了多点切线斜条分法偏于保守,是安全的。参数分析表明坡顶均布荷载、地震效应和非线性参数均对边坡安全系数及潜在临界滑裂面有重要影响。多点切线法引入非线性摩尔-库仑破坏准则对边坡进行稳定性极限分析,为相关研究人员提供了一种新的思路与方法。     

Stability analysis of slopes reinforced with piles

In this paper, the kinematic approach of limit analysis is used to analyse the stability of earth slopes reinforced with piles. First, the case of slope without piles is considered and a procedure is developed to calculate the safety factor for the slope. Results are compared with those obtained using both the limit equilibrium method and more complex upper and lower bound limit analysis solutions. Then, the stability of slopes reinforced with piles is analysed. Expressions are derived allowing the force needed to increase the safety factor to a desired value and the most suitable location of piles within the slope to be evaluated. A study is carried out to illustrate the effect of piles on slope stability.     

简单边坡的稳定性分析

提出了一种新方法用于分析边坡的稳定性,对土条间作用力作了如下假定：认为土条侧面作用力平行于条底,但其大小并不相等。依据平衡条件,结合强度破坏准则,求出边坡的安全系数。算例表明,该方法不失为一种合理、有效的边坡稳定分析方法。     

基于Barton-Bandis准则的锚固边坡稳定性分析

结合岩石节理面非线性Barton-Bandis破坏准则,探讨了将Barton-Bandis破坏准则参数转化为线性Mohr-Coulomb破坏准则抗剪强度参数的两种常用方法,通过实例分析了各方法的优劣。推导了加锚单岩石节理面控制的平面滑动岩体边坡抗滑稳定性安全系数计算式,开展了锚固参数分析。研究表明：相对于采用等效线性拟合法或切线等效法获取Mohr-Coulomb抗剪强度参数而言,直接应用Barton-Bandis破坏准则计算节理面控制的岩石边坡稳定性更为直观和简便;随着结构面基本摩擦角、结构面粗糙度系数和结构面壁面有效抗压强度的增大,边坡安全系数逐步提高,且结构面基本摩擦角和粗糙度系数对边坡安全系数的影响程度更为显著;锚索锚固力越大,边坡抗滑稳定性越好,而锚索设置角度越大,边坡抗滑稳定性越低,锚索角度设置不当将明显减小锚固效应的有效性。     

基于广义Hoek-Brown强度准则的岩质边坡开挖稳定性分析

导出了广义Hoek-Brown强度准则的弹塑性矩阵计算方法,并将其用于一岩质开挖边坡施工过程模拟。同时,利用Hoek所提出的参数等效化方法对岩质开挖边坡的稳定性进行强度折减分析,揭示了开挖施工过程中边坡临界失稳模式的演变、发展过程。分析结果表明,边坡的应力-应变场、位移场、边坡的稳定性及其临界失稳模式的演变过程与采用传统的Mohr-Coulomb强度准则的发展过程是一致的,但用Hoek所提出的等效Mohr-Coulomb强度参数可能会高估边坡的稳定性。     

非线性破坏准则与岩土材料地基承载力研究

根据线性Mohr-Coulomb破坏准则,前人运用极限平衡法、滑移线理论或极限分析等方法求解地基承载力问题,但实际上岩土在剪切破坏过程中破坏准则具有非线性。因此,为了研究非线性破坏准则对地基承载力的影响,基于上限定理,通过“切线法”引进变量,根据能量耗散情况,将承载力问题转变为非线性规划问题,运用“序列二次规划算法”求出地基承载力的最优解。数值计算结果表明,当非线性破坏准则转变为线性破坏准则时,非线性参数对地基承载力有重要影响。     

Stability analysis of slopes in soils with strain-softening behaviour

This paper presents a numerical approach to analyse the stability of slopes in soils with strain-softening behaviour. In these materials, a progressive failure can occur owing to a reduction of strength with increasing strain. Such a phenomenon can be analysed using methods that are able to simulate the formation and development of the shear zones in which strain localises. From a computational point of view, this presents many difficulties because the numerical procedures currently used are often affected by a lack of convergence, and the solution may depend strongly on the mesh adopted. In order to overcome these numerical drawbacks, in the present study use is made of a non-local elasto-viscoplastic constitutive model within the framework of the finite element method. The Mohr–Coulomb yield function is adopted, and the strain-softening behaviour of the soil is simulated by reducing the strength parameters with the increasing deviatoric plastic strain. To assess the reliability of the proposed approach, some comparisons with the results obtained using other constitutive models for soils with strain-softening behaviour are presented. Finally, a slope subjected to a prescribed process of weathering is considered, and the effects of this process on the slope stability are discussed.     

Plane failure analysis of rock slopes

Summary Hoek and Bray (1981) gave an analytical approach for plane failure analysis for rock slopes that is limited to those slopes in which the upper slope surface is horizontal and the tension crack is vertical. An analysis is presented here which can take these factors into account. It is found that varying the angle of the upper slope from 0° to 30° causes a significant reduction in the factor of safety. Varying the tension crack from vertical to 70° only has an effect when the upper slope angle is less than 20°.     

Upper bound finite element analysis of slope stability using a nonlinear failure criterion

In this study, upper bound finite element (FE) limit analysis is applied to stability problems of slopes using a nonlinear criterion. After formulating the upper bound analysis as the dual form of a second-order cone programming (SOCP) problem, the stress field and corresponding shear strength parameters can be determined iteratively. Thus, the nonlinear failure criterion is represented by the shear strength parameters associated with stress so that the analysis of slope stability using a nonlinear failure criterion can be transformed into the traditional upper bound method with a linear Mohr–Coulomb failure criterion. Comparison with published solutions illustrates the accuracy and feasibility of the proposed method for a simple homogeneous slope stability problem. The proposed approach is also applied to a seismic stability problem for a rockfill dam to study the influence of different failure criterions on the upper bound solutions. The results show that the seismic stability coefficients obtained using two different nonlinear failure criteria are similar but that the convergence differs significantly.     

A generalized nonlinear failure criterion for frictional materials

A generalized nonlinear failure criterion formulated in terms of stress invariants is proposed for describing the failure characteristics of different frictional materials. This failure criterion combines a power function and a versatile function in the meridian and deviatoric plane, respectively, which is a generalization of several classic criteria, including the Tresca, Drucker–Prager, Mohr–Coulomb, Lade–Duncan and Matsuoka–Nakai failure criterion. The procedure for determination of the strength parameters was demonstrated in detail. Comparisons between the failure criterion and experimental results were presented for uncemented/cemented Monterey sand, normally consolidated Fujinomori clay, rockfill, concrete, Mu-San sandstone and granite, which reveal that the proposed failure criterion captures experimental trend quite well.     

挡墙加固非饱和土边坡整体稳定性分析

在对挡墙加固边坡进行设计和评价时应综合考虑基质吸力和挡墙对边坡整体稳定性的影响。应用可以考虑基质吸力的弹塑性强度折减有限元程序,分析了挡墙加固非饱和土边坡的整体稳定性,揭示了基质吸力对加固边坡整体稳定性的影响程度,同时亦分析了整体潜在滑动面位置的变化情况,并进行了关于吸力摩擦角的敏感性分析。     

用弹性板理论分析顺层岩质边坡的失稳

根据弹性板的稳定理论，利用能量法对缓倾角顺层岩质边坡的弯曲失稳机理进行了探讨，特别考虑了边坡长度的影响，推导了相应的计算公式，并通过计算实例，将文中的方法与用平面应变问题的弹性梁分析得出的结果做了对比，验证了文中方法的可行性。     

阶梯状黄土路堑高边坡稳定性分析方法

根据阶梯状黄土路堑高边坡的特点,假定其滑移面下段为圆弧型,中上段为直线型,上段为垂直型的复合面,利用传统稳定系数的概念,导出阶梯状黄土高边坡稳定性分析表达式.经实际检验,比较符合实际.     

基于广义Hoek-Brown准则强度折减法的岩坡稳定性分析

针对岩质高边坡的稳定性分析问题,开展了基于广义Hoek-Brown破坏准则强度折减法的研究。提出了判别强度折减法合理性的两个基本标准：与Mohr-Coulomb准则强度折减法的一致性和能否体现节理岩体的真实破坏特征。基于以上标准,对比了3种不同的基于广义Hoek-Brown破坏准则的强度折减方法：σci、mi,σci、GSI和mi、GSI均同比折减,理论分析表明：mi、GSI同比折减更符合前述标准。最后,通过对工程实例的对比研究,验证了这一结论,并提出mi、GSI同比折减更能体现节理岩体的真实破坏特征,因而其安全系数的计算结果也更加真实可靠。     

阻滑桩加固土坡稳定性分析的上限解法

从极限分析机动学方法出发,利用土的抗剪强度折减系数概念,建立了土坡的极限平衡状态方程,由此确定土坡的临界稳定安全系数及其相应的潜在破坏模式.对于典型问题,通过与现有极限平衡解和有限元数值解的对比分析,验证了这种上限解法的合理性.进而对于在给定的荷载条件下不能满足抗滑稳定性要求的土坡,考虑采用阻滑桩加固方式,根据桩侧有效土压力的合理分布模式确定桩体与滑动面相交的截面上等效抗滑力和抗滑力矩,利用极限分析上限定理建立了阻滑桩加固土坡的极限平衡状态方程,将桩侧土压力作为目标函数,运用数学规划方法确定了极限平衡状态时的临界桩侧土压力,以此为土坡加固中阻滑桩设计提供依据.通过数值计算与分析探讨了阻滑桩加固位置的优化布置等问题.