共查询到20条相似文献，搜索用时 406 毫秒
1.
基于非线性Mohr-Coulomb破坏准则,结合极限分析上限法和拟静力分析法,建立功能方程,推导了地震效应下裂缝边坡的安全系数计算方程。采用数学规划方法,计算了不同参数组合条件下的边坡安全系数值,详细分析了非线性条件下一系列参数对边坡稳定性的影响。研究表明,边坡安全系数随非线性参数和地震效应的增大而减小。对比分析可知,在非线性破坏准则下,裂缝深度较大时,裂缝对边坡稳定性影响显著,且边坡越陡影响越大;当裂缝深度超过某个值后,临界破坏面起始端可能不穿过裂缝最底端,而是从裂缝中间某部位穿过。在地震效应作用下,非线性抗剪强度参数对安全系数影响显著。研究成果进一步完善了裂缝边坡稳定性分析内容,所列图表为边坡的设计与施工提供有益参考。 相似文献
2.
《Computers and Geotechnics》2006,33(6-7):294-304
When the slope geometry, unit weight and pore water pressure distribution in a homogeneous soil slope are given, the location of the critical slip surface for a particular method of slices is related only to the ratio of c′ (cohesion) and tan ϕ′ (internal friction angle). To utilize this relationship in back calculating c′ and ϕ′ values, two slope models with circular slip mechanism are presented to represent shear failures in simple fill or cut slopes and long natural slopes, and for each of the models, two dimensionless parameters regarding c′/tan ϕ′ and maximum depth of the critical slip surface are introduced. Based on the new findings from limit equilibrium analysis of slope models, charts are plotted to show the relationships of the two dimensionless parameters and ϕ′ values for a safety factor of unity. Using the charts can make a rapid estimate of the magnitude of both c′ and ϕ′ from a known position of the failure surface in a homogeneous slope. 相似文献
3.
基于极限分析上限定理,考虑均匀加筋和三角形加筋两种加筋模式,采用拟静力分析方法推导了一定边坡高度条件下的三维加筋边坡临界加筋强度的计算公式。通过与已有文献结果的对比,验证了所提方法的正确性,并讨论了边坡宽高比、水平和竖向地震力系数对三维边坡稳定性的影响。结果表明:地震力作用下边坡临界加筋强度随边坡宽高比的增大而增加,但其变化速率逐渐减小,当边坡宽高比大于10时,三维边坡加筋强度与二维情况相近;随着水平地震作用的增大,三维边坡临界加筋强度呈非线性增大;随着竖向地震作用的增大,临界加筋强度大致呈线性增加,且随着坡角的增大,竖向地震作用对临界加筋强度的影响更加显著;两种加筋模式下的边坡临界加筋强度值变化规律一致,且三角形加筋模式所需的加筋强度较小,效果较优。最后,针对实际工程提出了一些工程建议。 相似文献
4.
Earthquake effects are commonly considered in the stability analysis of rock slopes and other earth structures. The standard approach is often based on the conventional limit equilibrium method using equivalent Mohr–Coulomb strength parameters (c and ?) in a slip circle slope stability analysis. The purpose of this paper is to apply the finite element upper and lower bound techniques to this problem with the aim of providing seismic stability charts for rock slopes. Within the limit analysis framework, the pseudo-static method is employed by assuming a range of the seismic coefficients. Based on the latest version of Hoek–Brown failure criterion, seismic rock slope stability charts have been produced. These chart solutions bound the true stability numbers within ±9% or better and are suited to isotropic and homogeneous intact rock or heavily jointed rock masses. A comparison of the stability numbers obtained by bounding methods and the limit equilibrium method has been performed where the later was found to predict unconservative factors of safety for steeper slopes. It was also observed that the stability numbers may increase depending on the material parameters in the Hoek–Brown model. This phenomenon has been further investigated in the paper. 相似文献
5.
《地学前缘(英文版)》2018,9(6):1639-1648
Cohesion(c) and friction angle(φ) of rock are important parameters required for reliability analysis of rock slope stability. There is correlation between c and φ which affects results of reliability analysis of rock slope stability. However, the characterization of joint probability distribution of c and φ through which their correlation can be estimated requires a large amount of rock property data, which are often not available for most rock engineering projects. As a result, the correlation between c and φ is often ignored or simply assumed during reliability studies, which may lead to bias estimation of failure probability. In probabilistic rock slope stability analysis, the influence of ignoring or simply assuming the correlation of the rock strength parameters(i.e., c and φ) on the reliability of rock slopes has not been fully investigated. In this study, a Bayesian approach is developed to characterize the correlation between c and φ, and an expanded reliability-based design(RBD) approach is developed to assess the influence of correlation between c and φ on reliability of a rock slope. The Bayesian approach characterizes the sitespecific joint probability distribution of c and φ, and quantifies the correlation between c and φ using available limited data pairs of c and φ from a rock project. The expanded RBD approach uses the joint probability distribution of c and φ obtained through the Bayesian approach as inputs, to determine the reliability of a rock slope. The approach gives insight into the propagation of the correlation between c and φ through their joint probability into the reliability analysis, and their influence on the calculated reliability of the rock slope. The approaches may be applied in practice with little additional effort from a conventional analysis. The proposed approaches are illustrated using real c and φ data pairs obtained from laboratory tests of fractured rock at Forsmark, Sweden. 相似文献
6.
Sam Frydman 《Geomechanics and Geoengineering》2020,15(1):54-63
ABSTRACTA simplified approach is presented for estimating permanent displacements in slopes as a result of both vertical and horizontal seismic accelerations. A study of 52 earthquake records showed that the time difference between maximum horizontal and vertical accelerations varied between 0 and 10.3 s. The approach is illustrated for an earth dam embankment by analysing the effects of five of the above earthquake records. The approach combines a pseudo-static slope stability analysis for estimation of the critical (or yield) horizontal-vertical acceleration combinations, and a Newmark type displacement analysis. Guidelines are presented for conservative choice of soil strength parameters of saturated clays for use in the stability analysis. While permanent displacements of up to 40 cm were predicted without considering the vertical acceleration component, no additional displacement above 3.5 cm resulted when this component was included. The predicted additional displacement was consistently less than 10%, and in 50% of the analyses, vertical acceleration led to smaller predicted displacements. The simple approach may be applied in analysis for any slope using real earthquake records. Using existing, empirical expressions for permanent displacement, based only on horizontal accelerations, the effect of the vertical accelerations may be conservatively estimated by increasing the displacement by 10%. 相似文献
7.
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. 相似文献
8.
地震效应和坡顶超载对均质土坡稳定性影响的拟静力分析 总被引：3，自引：0，他引：3
基于强度折减技术和极限分析上限定理,假定机动容许的速度场破坏面,考虑坡顶超载、水平和竖向地震效应影响推导了边坡稳定性安全系数的计算表达式。采用序列二次规划迭代方法（和内点迭代方法）对边坡安全系数目标函数进行能量耗散最小化意义上的优化计算,与多个算例的对比验证了其方法和程序计算的正确性;对影响土质边坡动态稳定性的一些因素进行了参数分析,分析表明：随着边坡倾角?、坡顶超载q、水平和竖向地震效应影响系数的增大,边坡稳定性安全系数显著下降;随着坡顶超载q、水平地震效应影响系数kh的增大、竖向地震效应影响系数kv的减小,边坡的潜在滑动面越来越深,潜在破坏范围越来越大。竖向地震效应对边坡稳定性也有一定影响,强震条件下的设计计算必须考虑竖向地震效应的影响。 相似文献
9.
顺层岩质边坡地震动力响应研究 总被引：1，自引：0，他引：1
地震作用下边坡的动力响应研究是边坡动力稳定分析的基础,利用FLAC3D有限差分软件建立一个顺层岩质边坡动力数值模拟模型,对其在竖向和水平向地震耦合作用下的动力响应全过程进行研究。研究表明,地震竖向和水平向耦合作用模拟比简单的模拟水平向振动更加接近实际情况,对岩土体的破坏更大;顺层岩质边坡在耦合地震作用下存在垂直放大和临空面放大作用;坡面水平向和竖向加速度均随高程增加呈增大趋势,在结构面处增大特别明显;竖向地震波产生的水平与竖向拉裂是触发斜坡体产生初期崩滑破坏的主控因素;边坡动力响应特征值的放大效应表明,其放大系数值从大到小依次是：竖向加速度＞水平加速度＞竖向速度＞水平速度;耦合地震波作用下,随着av /aH的增大,坡面监测各点横向位移基本呈增大趋势,说明竖向地震作用起了重要的破坏作用。 相似文献
10.
R. Trizzino 《Engineering Geology》1987,23(3-4):263-276
A simple method for evaluating the seismic stability of embankments and slopes has been developed by modifying the generalized procedure of slices proposed by Janbu. A pseudostatic analysis is carried out. The seismic force is represented through its horizontal and vertical components, acting on the centre of gravity of the soil mass. Defining a nominal state of plastic equilibrium, the safety factor of the slope for a given value of the seismic force is obtained through an iterative procedure that converges very rapidly. Moreover, by assuming a seismic force of intensity varying from zero value (static condition) up to a limit value, depending on the seismicity of the area, one can obtain the “influence lines” of the horizontal and vertical acceleration. Finally, a directional parametric analysis has been carried out considering a seismic force of a given intensity, acting in a direction varying from 0° to 360° with respect to the vertical axis through the gravity centre of the slope. By means of this procedure it is possible to locate a “critical zone” for the slope, i.e., that one within which any seismic force can cause the failure of the slope. Moreover, it appears that it is incorrect to consider only the horizontal acceleration in the stability analyses of slopes under earthquake loading conditions, as the most dangerous direction is usually different from the horizontal one. 相似文献
11.
考虑强度各向异性的边坡稳定有限元分析 总被引：1，自引：0，他引：1
天然沉积的土层总是表现出一定程度的强度各向异性,但现有的边坡稳定有限元分析极少考虑各向异性的影响。对大型有限元软件ABAQUS进行二次开发,使其能够考虑土体黏聚力随大主应力方向的变化,动态更新增量迭代求解过程中边坡不同位置处的抗剪强度,进而提出具备安全系数自动搜索功能的各向异性边坡稳定分析方法。计算结果表明,均匀边坡的有限元解与极限分析上限解相差很小。如果采用土体固结方向的黏聚力并按各向同性评价缓坡的稳定性,可能严重高估安全系数,尤其是在黏聚力较高的情况下。与极限分析不同,建立的强度更新有限元模型能够分析成层边坡的稳定性。 相似文献
12.
极限分析上限方法在海底斜坡稳定性评价中受到了广泛关注,但已有成果未考虑地震荷载以及多土层海底斜坡可能出现的局部破坏机制。基于上限定理,推导了拟静力水平地震条件下多土层海底斜坡外力功率与内能耗散率平衡方程;结合强度折减技术和最优化方法,求解了海底斜坡整体和局部地震稳定性安全系数,并实现了多土层海底斜坡的局部滑动面搜索;通过典型算例分析,验证了本文方法的有效性。在此基础上,探讨了不同水平地震条件下两种组合土层海底斜坡的整体和局部稳定性,通过与数值解对比,其结果可以较准确地评价海底斜坡稳定性并有效预测滑移面位置。最后,将极限分析上限方法应用于一海底斜坡工程实例。 相似文献
13.
14.
Most classical approaches for evaluating the stability of soil slopes with cracks are performed under two-dimensional (2D) condition. Three-dimensional (3D) effect and suction-induced effect of unsaturated soils are generally neglected in assessing the slope stability. This paper develops a 3D limit analysis method to evaluate the stability of an unsaturated soil slope with tension cracks under steady infiltrations. The boundary-value problem is formulated based on the 3D rotational failure mechanism by taking the effects of suction, effective unit weight, and tension crack into account. A simplified method is proposed to calculate the work rate of unsaturated soil weight. A layer-wise summation method is developed based on the divergence theorem to calculate the internal energy dissipation rate. Detailed discussions are conducted to investigate the effects of suction and Poisson's ratio on the stability of unsaturated soil slopes. Examples are given to illustrate the 3D effect, the suction-induced effect as well as the effects of infiltration and water in cracks on the slope stability. 相似文献
15.
This study embraces the formation of the limiting geometry of finite slopes under the static and seismic conditions within the slip line theory framework coupled with the modified pseudo-dynamic approach. The proposed methodology is expected to achieve a global factor of safety of 1.0 for the obtained slope profile. While analysing the stability of slopes using the limit analysis or the limit equilibrium method, the cognition of the slope geometry and the nature of the slip surface need to be known in advance. Such limitations are ruled out in the present analysis with the aid of the slip line method. Further, by employing the modified pseudo-dynamic approach, the dynamic properties of soil, such as damping ratio and frequency effect, are effectively considered in this stability analysis. The consideration of the slip line theory permits to achieve an adaptive failure mechanism in the analysis. The impact of a set of parameters characterizing the input motion and the dynamic soil properties on the behaviour of a slope explains the relevance of the present modified pseudo-dynamic approach compared to the conventional pseudo-static and the original pseudo-dynamic approaches. The proposed solution serves as a measure of the seismic slope stability in accordance with the geomorphological process generally encountered in nature. Compared with the available literature, the present results propose safe, economical, and efficient design guidelines for finite slopes and intimate the need for preventive measures to enhance the stability of existing slopes.
相似文献16.
Ashok K. Chugh 《国际地质力学数值与分析法杂志》2003,27(11):905-926
Boundary conditions can affect computed factor of safety results in two‐ and three‐dimensional stability analyses of slopes. Commonly used boundary conditions in two‐ and three‐dimensional slope stability analyses via limit‐equilibrium and continuum‐mechanics based solution procedures are described. A sample problem is included to illustrate the importance of boundary conditions in slope stability analyses. The sample problem is solved using two‐ and three‐dimensional numerical models commonly used in engineering practice. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
17.
黄土边坡中竖直裂隙的发育往往会对边坡稳定产生影响。相对于平面应变机制,建立三维破坏机制下边坡稳定性分析方法更能接近实际边坡失稳情况。基于塑性极限分析上限法,考虑预先存在竖直裂隙的三维黄土边坡不同破坏机制（坡面破坏、坡脚破坏和坡底破坏）,建立能量平衡方程及其无量纲临界高度值γH/c表达式,采用随机搜索法得到了临界高度的上限解。分析了约束宽度、边坡坡度、内摩擦角以及裂隙深度对三维竖直裂隙黄土边坡临界高度值的影响。结果表明：对于坡脚破坏机制,临界高度值随着裂隙深度的增加而减小,减小至临界裂隙深度 (δ /H)min后,裂隙深度的增加不再影响临界高度值;临界裂隙深度随着坡度β 的增大而增大,随着内摩擦角φ 的增大而减小。当约束宽度B/H<0.8时,大多数破坏机制为坡面破坏。当约束宽度B/H=0.8、内摩擦角φ =10° 及约束宽度B/H=0.6、内摩擦角φ =15° 时,边坡的破坏从坡面破坏机制逐渐过渡到坡脚破坏机制。存在竖直裂隙的黄土边坡比完整边坡具有更小的临界高度,约束宽度及内摩擦角会对三维黄土边坡破坏机制产生影响。 相似文献
18.
Seismic stability analysis of soil nail reinforced slope using kinematic approach of limit analysis 总被引：3，自引：0，他引：3
Prediction of the critical seismic yield acceleration coefficient and the seismic permanent displacement of soil nail reinforced
slope under seismic loading has been playing an important role in helping design in the earthquake-prone areas. In this paper,
the seismic stability of soil nail reinforced slope is analyzed using the kinematic theorem of limit analysis. The log-spiral
failure mechanism is considered and the corresponding analytical expressions are derived to calculate the critical seismic
yield acceleration coefficient and the permanent displacement of slope subjected to earthquake loading. A series of calculations
are carried out to illustrate the influence of inertial force on the stability of a nail-reinforced slope. Parametric studies
indicate that the strength and geometry of slope as well as characteristic parameters of soil nail have a significant effect
on the critical seismic yield acceleration coefficient and the permanent displacement of soil nail reinforced slope. 相似文献
19.
Fei Zhang Dov Leshchinsky Rafi Baker Yufeng Gao Ben Leshchinsky 《国际地质力学数值与分析法杂志》2016,40(18):2514-2531
This paper revisits the variational limit equilibrium (LE) analysis of three‐dimensional (3D) slope stability in the context of limit analysis (LA). It proves the kinematic admissibility of the 3D mechanism in LA, although it was derived from LE variational extremization. It also includes algorithms in the realm of LA that are associated with the variational mechanism. A comparison between the variational results and reported LA upper‐bound or LE closed‐form results is conducted. It demonstrates that the variationally derived mechanism consistently yields upper‐bound solutions for 3D symmetrical slopes that are as accurate as those produced by postulated mechanisms in LA. However, the results are more critical than those derived from spherical failure mechanism in LE. The generalized log spiral 3D mechanism rigorously legitimizes the variational slope stability analysis in both frameworks of mechanics LE and LA. Stability charts were produced where the 3D factor of safety can be assessed for a constrained length of failure, while including factors like pore water pressure and seismic loading. The results presented within this study demonstrate the capabilities of the variational 3D solution and can be used to evaluate approximate methods, numerical or closed‐form, developed in 3D slope stability analyses. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
20.
By using an axisymmetric lower bound finite element limit analysis formulation, the stability numbers (γH/c) for an unsupported vertical circular excavation in a cohesive–frictional soil have been generated. The numerical results are obtained for values of normalized excavation height (H/b) and friction angle (ϕ) greater than those considered previously in the literature. The results compare well with those available in literature. The stability numbers presented in this note would be beneficial from a design point of view. 相似文献