共查询到20条相似文献，搜索用时 218 毫秒
1.
边坡可靠度分析的一种新的优化求解方法 总被引：1，自引：0，他引：1
介绍了Low & Tang提出的一种新的可靠度优化求解方法,并将之用于边坡可靠度分析中：该方法适用于任何概率分布的相关变量,不必计算当量正态均值和方差、相关变量独立变换,直接在变量的原始空间内搜索边坡的最小可靠指标和概率临界滑面,可采用任何合适的约束优化方法进行求解,方法清晰简洁。边坡可靠度分析常用的滑面有2个：最小安全系数（变量均值处）对应的确定性临界滑面和最小可靠指标对应的概率临界滑面,但这2个滑面在有些情况下差别较大,Hassan & Wolff提出了一种简化方法可以方便地获得概率临界滑面,但由于方法简单,受到质疑。通过一系列算例分析,优化求解方法得到的概率临界滑面和Hassan & Wolff的简化方法滑面非常接近,显示了简化方法的有效性,值得在工程实践中推广。 相似文献
2.
提出一种考虑能量-时间分布的边坡动力可靠性分析方法。该方法将动态最危险滑动面及其稳定系数以时间序列加以刻画,并根据边坡动力反应的能量分布特征,提取持续时间统计窗,用于对上述时间序列的统计分析,以获取边坡动力模糊失效概率、边坡动力可靠度指标和基于保证率的边坡动力稳定系数。以澳大利亚计算机应用协会边坡稳定考核题为例,应用上述新方法考察其在芦山7.0级主震波形条件下的稳定性,研究了在不同统计窗下的边坡动力可靠性。案例分析表明： （1）新方法能够抓住影响边坡动力稳定的主要时间段,使分析结果更为凝练、可信。（2）通过引入边坡失效状态的模糊判别,使得可靠性评价中能够考虑模糊性,解决了以往常规方法区分度不够的问题。（3）基于保证率的边坡动力稳定系数具有很好的应用前景,它在内涵上体现了可靠性分析,在形式上与静力稳定系数的定义兼容,在数值上反映了边坡瞬时动力稳定系数的保守估计值,在实践上与现行规范的拟静力法具有良好的可比性,因而具有多方面的优势。（4）就本案例而言,动力条件下最危险滑动面的发育位置趋向于静力条件下的最危险滑动面,体现了依据静力和拟静力理论框架所进行的防护工程设计,在动力条件下仍然具有积极的意义。（5）新方法对定量研究现行边坡规范的抗震设计冗余提供了一条途径。提出的新方法为边坡抗震研究提供了新的思路、方法和可供参考的实例。 相似文献
3.
基于均质路堤边坡Monte Carlo法的稳定可靠度计算,分析了临界滑面搜索策略和稳定分析方法两类模型不确定性对边坡可靠度的影响特性,讨论了边坡失效概率随土工参数变异性的变化规律。研究表明,选用不同的临界滑面搜索策略所得可靠度结果差异不大,参数滑面法（overall slope）的失效概率略大于均值滑面法（global minimum）,但差别对边坡稳定性分析没有实质性影响;土性参数变异水平是影响边坡可靠度的最重要因素,边坡在相同设计参数安全系数下的可靠度指标随参数变异性增大而急剧降低;不同稳定性分析方法对应的安全系数概率密度函数曲线形态基本一致,但失效概率差异明显,因此目标可靠度指标取值应与稳定性分析方法相适应。提出的考虑土工参数变异水平的安全系数取值修正原则,对改进确定性设计的边坡稳定分析技术有积极意义。 相似文献
4.
This paper deals with slope reliability analysis incorporating two-dimensional spatial variation. Two methods, namely the method of autocorrelated slices and the method of interpolated autocorrelations, are proposed for this purpose. Investigations are carried out based on the limit equilibrium method of slices. First-order-reliability-method (FORM) is coupled with deterministic slope stability analysis using the constrained optimization approach. Systematic search for the probabilistic critical slip surface has been carried out in this study. It is shown that both methods work well in modeling 2-D spatial variation. The results of slope reliability analysis are validated by Monte Carlo simulations. Failure probabilities obtained by FORM agree well with simulation results. It is found that 2-D spatial variation significantly influences the reliability analysis, and that the reliability index is more sensitive to vertical autocorrelation distance than to horizontal autocorrelation distance. Based on this study, failure probability is found significantly overestimated when spatial variation is ignored. Finally, the possible use of the method of interpolated autocorrelations in a probabilistic finite element analysis is suggested. 相似文献
5.
临界滑动面的获得是土质边坡稳定性分析中一个必要的过程,然而现有分析方法难以保证该临界滑面的准确性,而且部分分析方法在计算过程中会陷入局部最小值陷阱。基于单变量方法和最速梯度法,提出了交替变量局部梯度法,该方法能够突破最优化方法应用在边坡稳定性分析上的瓶颈。首先,通过斯宾塞极限平衡方法和网格搜索法（或者其他确定临界滑面的方法）,获得边坡初始椭球状临界滑面;其次,在该滑面上布置若干节点作为变量,目标函数为安全系数Fs关于空间节点坐标Zi的方程,为了使目标函数快速降低,沿负梯度方向循环优化每个节点,当满足一定精度要求时,即可获得三维土质边坡非圆弧状临界滑动面;最后,通过算例证明该方法可行,计算结果可靠。 相似文献
6.
基坑土钉支护边坡有限元稳定性分析方法探讨 总被引：4，自引：1，他引：3
针对基坑土钉支护开挖边坡的稳定性,讨论了极限平衡方法的局限性,指出应用有限元方法分析评价基坑土体结构稳定性是近年来研究的新趋势。采用滑面应力分析法和强度折减法两种有限元方法对基坑边坡的稳定性进行了研究。对于无支护的基坑边坡,两种有限元方法得到的安全系数和滑动面结果一致,且滑动面形状随基坑土体强度的降低保持不变。对于采用土钉支护的基坑边坡,两种有限元方法得到的安全系数结果一致,不同阶段下滑动面形状和位置不同,这主要是由于在强度折减时,仅仅对土体强度参数进行折减,而未考虑土钉自身强度的降低。最后指出,在应用强度折减法时,是否考虑土钉自身强度的折减有待进一步研究。 相似文献
7.
基于临界滑动场的岩质边坡临界滑动面搜索方法 总被引：1，自引：0，他引：1
在边坡稳定分析中临界滑动面搜索是关键问题。现行搜索算法包括数学规划法和智能搜索算法,均是以圆弧或圆弧加折线为假定滑动面形式在计算土质边坡基础上发展起来的,基本上不适用于岩质边坡计算。临界滑动场理论以余推力法和最优化理论为基础,采用新的结构面处理方法,可计算出与实际情况基本吻合的最大余推力方向场,能方便追踪出各可能出口点的滑动面,从而找出边坡整体临界滑动面。取一均质土质边坡算例对计算结果可信度进行验证,与强度折减法和Spencer极限平衡法所得计算结果相吻合。另取一露天矿边坡对该方法的实用性进行了验证。 相似文献
8.
Te Xiao Zi-Jun Cao Xiao-Song Tang 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2017,11(1):146-159
ABSTRACTA simplified reliability analysis method is proposed for efficient full probabilistic design of soil slopes in spatially variable soils. The soil slope is viewed as a series system comprised of numerous potential slip surfaces and the spatial variability of soil properties is modelled by the spatial averaging technique along potential slip surfaces. The proposed approach not only provides sufficiently accurate reliability estimates of slope stability, but also significantly improves the computational efficiency of soil slope design in comparison with simulation-based full probabilistic design. It is found that the spatial variability has considerable effects on the optimal slope design. 相似文献
9.
The paper presents a computational procedure for reliability analysis of earth slopes considering spatial variability of soils under the framework of the Limit Equilibrium Method. In the reliability analysis of earth slopes, the effect of spatial variability of soil properties is generally included indirectly by assuming that the probabilistic critical slip surface is the same as that determined without considering spatial variability. In contrast to this indirect approach, in the direct approach, the effect of spatial variability is included in the process of determination of the probabilistic critical surface itself. While the indirect approach requires much less computational effort, the direct approach is definitely more rigorous. In this context this paper attempts to investigate, with the help of numerical examples, how far away are the results obtained from the indirect approach from that obtained from the direct approach. In both the approaches, it is required to use a model of discretization of random fields into finite random variables. A few such models are available in the literature for one-dimensional (1D) as well as two-dimensional (2D) spatial variability. The developed computational scheme is based on the First Order Reliability Method (FORM) coupled with the Spencer Method of Slices valid for limit equilibrium analysis of general slip surfaces. The study includes bringing out the computational advantages and disadvantages of the three commonly used discretization models. The sensitivity of the reliability index to the magnitudes of the scales of fluctuation has also been studied. 相似文献
10.
This paper develops a risk de-aggregation and system reliability approach to evaluate the slope failure probability, pf, using representative slip surfaces together with MCS. An efficient procedure is developed to strategically select the candidate representative slip surfaces, and a risk de-aggregation approach is proposed to quantify contribution of each candidate representative slip surface to the pf, identify the representative slip surfaces, and determine how many representative slip surfaces are needed for estimating the pf with reasonable accuracy. Risk de-aggregation is performed by collecting the failure samples generated in MCS and analyzing them statistically. The proposed methodology is illustrated through a cohesive soil slope example and validated against results from previous studies. When compared with the previous studies, the proposed approach substantially improves the computational efficiency in probabilistic slope stability analysis. The proposed approach is used to explore the effect of spatial variability on the pf. It is found that, when spatial variability is ignored or perfect correlation assumed, the pf of the whole slope system can be solely attributed to a single representative slip surface. In this case, it is theoretically appropriate to use only one slip surface in the reliability analysis. As the spatial variability becomes growingly significant, the number of representative slip surfaces increases, and all representative slip surfaces (i.e., failure modes) contribute more equally to the overall system risk. The variation of failure modes has substantial effect on the pf, and all representative surfaces have to be incorporated properly in the reliability analysis. The risk de-aggregation and system reliability approach developed in this paper provides a practical and efficient means to incorporate such a variation of failure modes in probabilistic slope stability analysis. 相似文献
11.
提出了一套基于随机响应面法的边坡系统可靠度分析方法。该方法首先从大量潜在滑动面中筛选出代表性滑动面。针对每条代表性滑动面,采用Hermite多项式展开建立其安全系数与土体参数间的非线性显式函数关系（即随机响应面）。然后,采用直接蒙特卡洛模拟计算边坡系统失效概率。在蒙特卡罗模拟中,采用所有代表性滑动面的随机响应面计算每一组样本所对应的边坡最小安全系数。最后,以两个典型多层边坡系统可靠度问题为例验证了该方法的有效性。结果表明：文中提出的边坡系统可靠度分析方法能够有效地识别边坡代表性滑动面,具有较高的计算精度和效率,并且确定代表性滑动面时无需计算滑动面间的相关系数。同时该方法可以有效地计算低失效概率水平的边坡系统可靠度,为含相关非正态参数的边坡系统可靠度问题提供了一条有效的分析途径。此外,多层边坡可能同时存在多条潜在滑动面,基于单一滑动面（如临界确定性滑动面）或者部分代表性滑动面进行边坡系统可靠度分析均会低估边坡失效概率。 相似文献
12.
Xing Zheng Wu 《Computational Geosciences》2013,17(5):739-755
In probabilistic slope stability analysis, the influence of cross correlation of the soil strength parameters, cohesion and internal friction angle, on the reliability index has not been investigated fully. In this paper, an expedient technique is presented for probabilistic slope stability analysis that involves sampling a series of combinations of soil strength parameters through a copula as input to an existing conventional deterministic slope stability program. The approach organises the individual marginal probability density distributions of componential shear strength as a bivariate joint distribution by the copula function to characterise the dependence between shear strengths. The technique can be used to generate an arbitrarily large sample of soil strength parameters. Examples are provided to illustrate the use of the copula-based sampling method to estimate the reliability index of given slopes, and the computed results are compared with the first-order reliability method, considering the correlated random variables. A sensitivity study was conducted to assess the influence of correlational measurements on the reliability index. The approach is simple and can be applied in practice with little effort beyond what is necessary in a conventional analysis. 相似文献
13.
在经验性降雨阈值和边坡稳定性数值分析两大类研究的基础上,考虑了降雨入渗和非饱和土性质,使用岩土有限元软件Plaxis高级模式对滑坡预警降雨阈值进行研究分析。算例表明,将降雨量在降雨时间范围内分成2段后,得到的边坡稳定性变化与实际情况更接近,重新定义前期降雨为在给定初始条件下引起边坡最危险滑裂面到坡面之间土体吸力分布发生变化的降雨。前期降雨时长与潜在滑裂面最大深度成正比,与饱和渗透系数成反比。将前期降雨量引入到降雨强度—持时曲线中作为第三个空间坐标轴,将该曲线拓展为前期降雨量-降雨强度-持时曲面。通过一基岩型边坡算例展示了阈值曲面的建立方法,并通过与模型试验数据的对比验证了其可靠性。 相似文献
14.
安全系数的计算和临界滑动面的确定是边坡稳定性分析的两个组成部分,强度折减法可以得到合理的安全系数,但却不能准确刻画临界滑动面的位置。基于对滑动现象的认识,提出了一种基于位移场分析的临界滑动面确定方法,认为当边坡处于临界状态时,其潜在滑动面附近的位移等值线最为密集,潜在滑动面上的点往往是在深度方向上沿垂直滑面的位移变化率达到最大值的位置。将本文方法与Spencer法、岩质边坡模型试验进行了对比,验证了该方法在曲线和折线滑动面搜索方面的适用性和可靠性。同时,探讨了单元形状、疏密程度、离散点间距等因素对滑动面的影响。 相似文献
15.
圆弧滑动有限元土坡稳定分析 总被引：13，自引：0，他引：13
提出一种基于有限元应力变形计算的边坡稳定分析方法,仍假定滑动面形状为圆弧形,有限元网格由一组同心圆作为纬线,一组竖向线为经线构成。对两相邻圆弧线所夹的弧形带分析滑动力和抗滑力,建立平衡方程,确定安全系数,其中小值安全系数对应的弧形带为可能的滑动带。变化圆心位置用优选方法寻找最小安全系数对应的圆心,从而得出真正的滑动面。算例分析表明,该方法计算所得安全系数与Bishop法接近,是合理的,其突出优点是由有限元计算直接得出滑面上的应力,而不须作近似的插值处理,因而应力更准确。该方法可以考虑土的非线性变形特性,也更符合土的实际情况。此外,用有限元计算得出位移,亦可将稳定分析和变形联系起来,为现场通过位移监测来估计边坡的稳定性提供了可能性,同时也为膨胀土边坡的稳定分析中考虑膨胀性的影响提供了可能性。 相似文献
16.
Mohsen Abbaszadeh Kourosh Shahriar Mostafa Sharifzadeh Mehrdad Heydari 《Geotechnical and Geological Engineering》2011,29(4):581-596
Nowadays, there are many new methods for slope stability analysis; including probabilistic methods assessing geotechnical
uncertainties to develop safety factors. In this paper, a reliability index analysis for the Sungun copper mine slope stability
is evaluated based on three methods of uncertainties consisting Taylor series method, Rosenblueth point estimate method and
Monte-Carlo simulation method. Sungun copper mine will be one of the Iran’s biggest mines with final pit’s height of 700 meters.
For this study two of its main slopes were assessed, one dipping to the NE (030) and the other to the SE (140). Probability
density function of cohesion and angle of friction for the slopes were developed using limit equilibrium methods. These shear
strengths were then used to determine the probability density function of safety factor and reliability index using the probabilistic
methods. Results of the probabilistic analysis indicate that with ascending values of the uncertainties the reliability index
decreases. Furthermore, it was determined that with the Monte Carlo simulation the seed number used has little effect on the
reliability index of the safety factor especially with seed numbers in excess of 1200. Variations in the overall reliability
index of safety factor were observed between the two slopes and this difference is explained by the differences in complexities
of the geology within the cross-section. 相似文献
17.
数值分析方法（有限元、有限差分等）可计算边坡应力、变形和破坏,但直接计算边坡安全系数比较困难;而极限平衡法需对边坡体内力作出假设,计算精度受到限制。利用数值分析方法计算得到的应力场,重新定义推力最大原理中推力的含义,将常规边坡临界滑动场数值模拟方法作进一步的改进,提出基于数值应力场的边坡临界滑动场方法。该方法可充分发挥两大方法的优势,能够准确、方便地搜索出边坡临界滑动面位置,并给出更合理的边坡安全系数。通过两个算例的稳定性分析,并与其他方法进行比较,验证了该方法的准确性和合理性。 相似文献
18.
Reza Jamshidi Chenari Reza Alaie 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2015,9(2):109-123
Slopes are mainly naturally occurred deposits, so slope stability is highly affected by inherent uncertainty. In this paper, the influence of heterogeneity of undrained shear strength on the performance of a clay slope is investigated. A numerical procedure for a probabilistic slope stability analysis based on a Monte Carlo simulation that considers the spatial variability of the soil properties is presented to assess the influence of randomly distributed undrained shear strength and to compute reliability as a function of safety factor. In the proposed method, commercially available finite difference numerical code FLAC 5.0 is merged with random field theory. The results obtained in this study are useful to understand the effect of undrained shear strength variations in slope stability analysis under different slope conditions and material properties. Coefficient of variation and heterogeneity anisotropy of undrained shear strength were proven to have significant effect on the reliability of safety factor calculations. However, it is shown that anisotropy of the heterogeneity has a dual effect on reliability index depending on the level of safety factor adopted. 相似文献
19.
针对基坑工程中岩土参数存在随机性和变异性的特点,基于响应面重构法、遗传算法和禁忌搜索方法研究了土钉墙边坡可靠性分析方法。考虑土钉的加固作用,建立了适用于土钉墙边坡任意形状滑面安全系数计算的改进Morgenstern-Price法。基于响应面原理,将改进Morgenstern-Price法取代传统响应面法中的有限单元法来随机抽样构造响应面函数,建立了一种近似的土钉墙边坡可靠度计算方法。以土体的抗剪强度指标 、 为随机变量,提出了一种能同时确定土钉墙边坡最小可靠度指标 及相应最危险滑面的全局优化计算方法--土钉墙可靠性分析自适应禁忌搜索遗传算法（ATSGA）。结合算例,分别以土钉墙边坡的最小可靠度指标和最小中值安全系数为目标函数,采用ATSGA法搜索其相应的最危险滑动面,结果表明,二者相差较大。 相似文献
20.
Stability of an embankment constructed on soft consolidating soil improved with pre-fabricated vertical drains is investigated. The factor of safety of the embankment is obtained at various time intervals from the end of construction till the end of consolidation in order to check the embankment stability. Finite element method is used to obtain the effective stresses at required points in soil at various time intervals. Critical slip surface is obtained using two methods. In the first method, the critical slip surface is assumed as an arc of a circle selected among various probable slip circles with minimum factor of safety whereas, in the second method, a random walking type Monte Carlo technique is used to predict the critical slip surface. The effects of providing vertical drains on stability of an embankment is investigated by comparing the factor of safety of slope with vertical drains to the factor of safety of slope without vertical drains. It is concluded from the study that the installation of vertical drains enhances the factor of safety of the embankment from the end of construction till the end of consolidation. 相似文献