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1.
基于Hoek—Brown非线性经验强度准则和简化Bishop法，导出了节理破碎岩体边坡新的稳定性系数计算公式。通过在简单遗传算法（SGA）中引人适应度变换技术改进其收敛性能，提出了节理破碎岩体边坡稳定性分析和最危险滑动面搜索的自适应遗传算法（AGA）。算例计算结果表明：（1）AGA能准确地搜索到边坡全局最小稳定系数及其对应的临界滑动面；（2）AGA计算效率和数值稳定性均比SGA和随机投点法有较大提高；（3）采用不同的适应度变换函数均可提高计算效率。为简便起见，推荐采用线性变换函数。 相似文献
2.
针对土钉墙内部稳定性分析问题,提出一种能同时确定土钉墙任意形状最危险滑动面及相应安全系数的全局优化算法。首先,基于边坡极限平衡法中的Morgenstern-Price法,考虑土钉的加固作用,推导土钉墙安全系数计算公式。然后,分析简单遗传算法（SGA）和禁忌搜索算法（TSA）的不足,引进自适应遗传算法（AGA）,用禁忌变异算子替换自适应遗传算法中的标准变异算子,提出一种新型的混合优化算法--自适应禁忌变异遗传搜索算法（ATMGA）,并将其应用到土钉墙内部稳定性分析领域,建立土钉墙任意形状临界滑裂面稳定性分析优化算法。算例分析表明,（1）与单纯的SGA、TSA以及AGA相比,文中ATMGA法搜索效率高、收敛速度快且能准确地搜索到土钉墙最危险滑动面及其相应的最小安全系数;（2）土钉支护前、后临界滑面位置相差较大,建议在实际工程中对支护后基坑的临界滑面以及相应的安全系数进行重新搜索。 相似文献
3.
An automatic technique for the determination of the coefficients of models for soil–water characteristic curves (SWCC) or water retention curves (WRC) is presented. The technique is based on optimisation using genetic algorithms, in which the error between predictions and experimental data is minimised by varying the model parameters. The method is powerful and reasonably efficient in finding the best parameters. Four models are analysed including one accounting for hysteresis behaviour. Details of a simple genetic algorithm (SGA) and its complete application are explained. To account for the hysteresis of the SWCC, the models are programmed in a rate form, in which numerical integration is employed to advance the state variables. One advantage of the optimisation presented is that the best curves averaging both the drying and wetting paths are obtained when hysteresis is present. 相似文献
4.
岩土工程数值分析方法对于研究复杂的岩土介质与多变的施工措施是一种得力的方法,比传统的解析方法、室内试验方法、模拟试验方法、现场试验方法等具有无可替代的优越性。按岩土工程数值方法的历史发展、作用及发展方向,将其分为4个层次：作为一种高级计算器,直接为某个具体岩土工程的设计服务,对该岩土工程在各种极端设计工况下进行安全性、稳定性的计算分析;作为一种强大的、无与伦比的模拟分析器,对复杂工况条件下复杂岩土工程的各种不利因素的相互作用、相互影响、耦合效应等进行模拟分析;作为一种无成本、可重复的多功能试验机,探索具体岩土工程的稳定机制或某工程措施的加固机制;作为岩土工程数值方法的终极目标,对数值分析方法进行二次开发——研发智能化、快速化、简便化的新型数值分析工具。对这4个层次进行了讨论,并对每个层次进行举例说明。 相似文献
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一维固结条件下黏土微结构再造过程研究和描述 总被引：1，自引：1，他引：0
采用冷冻制样方法,对不同固结压力作用下得到的重塑黏土压缩试样进行了真空干燥,对其水平截面、45o截面和垂直截面上获得的SEM照片域微结构参数进行了研究。对简单微结构参数的研究表明,随固结压力增大颗粒体所占比重越来越大。对合成微结构参数的研究包括主成分分析和聚类分析两方面,结果表明,随固结压力增大,第一主成分指标近似线性增大;不同固结压力作用下的样品具有明显的聚类特征,且类内距离随固结压力增大逐渐增大。在建立各种土力学关系时,可以考虑纳入合成微结构参数而并非简单微结构参数,以反映土微结构的整体特征。 相似文献
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A Simple Method for Analysis of Point Anchored Rockbolts in Circular Tunnels in Elastic Ground 总被引：1，自引：0，他引：1
A. Bobet 《Rock Mechanics and Rock Engineering》2006,39(4):315-338
Summary. A simple analytical method for the analysis of point anchored rockbolts is presented in this paper. The solution has been
derived for elastic ground and rockbolts, for plane strain conditions, and for tunnels with circular cross section. The method
provides accurate results for the rockbolts’ loads and displacements and explicitly includes the connection of the rockbolts
to the surrounding ground. The addition of such details to a Finite Element numerical model is critical; otherwise the solution
obtained may be dependent on the discretization used and on the stiffness of rockbolts and ground. As an alternative to including
details of the rockbolt head and anchor point in the numerical model, which could be computationally very expensive, an equivalent
spring constant is proposed. The spring constant is obtained by matching numerical with analytical results for a simple case,
but keeping the geometry, material properties, and discretization unchanged. 相似文献
9.
This paper presents a method that incorporates a non‐associated flow rule into the limit analysis to investigate the influence of the dilatancy angle on the factor of safety for the slope stability analysis. The proposed method retain's the advantage of the upper bound method, which is simple and has no stress involvement in the calculation of the energy dissipation and the factor of safety. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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基于矢量和分析方法的边坡滑面搜索 总被引：8，自引：3，他引：5
基于力是矢量这个基本概念,给出了边坡矢量和法安全系数的矢量表达式。在边坡荷载已知的情况下,运用有限元法计算得到边坡真实的应力分布状态,使用矢量和法安全系数并采用优化算法中的直接法搜索边坡的临界滑面。计算结果表明,使用矢量和分析法搜索得到的临界滑面位置与极限平衡法得到的滑面位置基本吻合,且安全系数相对误差最大为2.09 %,验证了该方法在边坡稳定分析中的合理性与可靠性。矢量和分析方法与基于强度储备安全系数的分析方法不同,具有明确的物理和力学意义,且不需引入过多假设,公式简洁,易于进行三维边坡稳定分析,不需进行迭代计算,可在工程实际中得到广泛的运用。 相似文献
12.
In a probabilistic analysis of rock slope stability, the Monte Carlo simulation technique has been widely used to evaluate
the probability of slope failure. While the Monte Carlo simulation technique has many advantages, the technique requires complete
information of the random variables in stability analysis; however, in practice, it is difficult to obtain complete information
from a field investigation. The information on random variables is usually limited due to the restraints of sampling numbers.
This is why approximation methods have been proposed for reliability analyses. Approximation methods, such as the first-order
second-moment method and the point estimate method, require only the mean and standard deviation of the random variable; therefore,
it is easy to utilize when the information is limited. Usually, a single closed form of the formula for the evaluation of
the factor of safety is needed for an approximation method. However, the commonly used stability analysis method of wedge
failure is complicated and cumbersome and does not provide a simple equation for the evaluation of the factor of safety. Consequently,
the approximation method is not appropriate for wedge failure. In order to overcome this limitation, a simple equation, which
is obtained from the maximum likelihood estimation method for wedge failure, is utilized to calculate the probability of failure.
A simple equation for the direct estimation of the safety factors for wedge failure has been empirically derived from failed
and stable cases of slope, using the maximum likelihood estimation method. The developed technique has been applied to a practical
example, and the results from the developed technique were compared to the results from the Monte Carlo simulation technique. 相似文献
13.
Gregory H. Roder 《Tectonophysics》1977,43(3-4)
Two methods are presented whereby finite-strain data may be determined from naturally occurring irregular strain markers (polygons) which are of unknown pre-deformation shape and distribution, without assumptions as to the orientation of the finite-strain ellipse. The first method describes “construction” of ellipses within the polygons, these ellipses providing the basis for analysis by already developed techniques. The second method is a simple extension of Wellman's method, which graphically establishes a strain ellipse from angle and line data. 相似文献
14.
渗流分析中排水孔模拟的叠单元法 总被引：2，自引：0，他引：2
排水孔是重要的渗控措施,如何准确模拟排水孔的作用是渗流分析中的关键问题之一。目前普遍采用排水子结构法,但由于子结构网格依存于整体网格,在解决复杂工程问题时网格划分难度很大。文中提出一种新的排水孔模拟方法--叠单元法。对于含排水孔的结构,将其划分为不包含排水孔的整体网格以及各排水孔附近区域的局部网格,网格之间相互独立。然后,通过排水孔局部网格的外边界面的虚拟渗流,实现整体网格与排水孔局部网格的耦合。算例分析的结果表明,当排水孔局部网格范围大小取为整体网格单元尺寸的1～3倍,外边界面渗透系数取为材料渗透系数的102～103倍时,所提方法能够准确模拟排水孔的作用。由于叠单元法的网格划分简便易行,有望广泛应用于复杂工程问题的渗流分析 相似文献
15.
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
16.
Paul F. Carr 《Mathematical Geology》1981,13(3):193-200
Permian and post-Permian igneous rocks of the southern Sydney Basin of New South Wales can be distinguished on the basis of major-element geochemistry. A data base of 102 analyses of these igneous rocks has been used to evaluate the effectiveness of various discriminants based on univariate and multivariate analysis. Inspection of histograms of compositional frequency for each major-element oxide is an efficient method of univariate analysis and assigns up to 92.2% of the rocks to the correct age group. Discriminant function analysis using up to 10 variables does not produce a more efficient discriminant than the simple binary plot of SiO
2
versus TiO
2,which assigns 95.1% of the rocks to the correct age group. No other binary or ternary diagram commonly used in petrology produces such an efficient discriminator. 相似文献
17.
A computational method, based on an advanced elasto-plastic large strain formulation, well suited for the analysis of the cone penetration problem, is presented. A new approach of finite strain elasto-plastic analysis is employed.13 The basic (non-rate) constitutive relations are developed in a spatial reference space to preserve their physical significance. They are subsequently transformed in Lagrangian co-ordinates, and through simple time differentiation, their rate equations are introduced. The method is computationally implemented with the finite element method and special provisions are taken to allow for the moving boundary conditions of the problem. 相似文献
18.
岩土材料极限分析上界法的讨论 总被引：9，自引：2，他引：7
现行的极限分析上界法,尽管求解结果合理,但理论上却存在一些矛盾：如试验证明,关联流动法则不适用于岩土材料,而现行解法却采用了关联流动法则;传统分析中假设体积不变,但计算中却出现大于实际的体积剪胀变形;按关联流动法则,应力特征线与速度滑移线重合,但在分析中却采用速度方向与应力特征线方向成 角;实际土体破坏时,破坏面上同时存在着剪切力 和正应力 ,但在计算中却反映不出摩擦功。近年在中国日益兴起的广义塑性力学理论为岩土材料的极限分析方法提供了科学的理论基础。作者提出了基于广义塑性力学的极限分析上界法,消除了上述矛盾,并获得了正确的计算结果。通过同经典算法的比较,证明了两种方法的计算结果几乎是一致的,但现行方法计算简便,因而,可作为一种实用的计算方法。论文还对上述两种算法作了系统的分析与比较,指出了它们求解的相同点与不同点。 相似文献
19.
On the Equivalence of the Cokriging and Kriging Systems 总被引：2，自引：0，他引：2
Simple cokriging of components of a p-dimensional second-order stationary random process is considered. Necessary and sufficient conditions under which simple cokriging is equivalent to simple kriging are given. Essentially this condition requires that it should be possible to express the cross-covariance at any lag series h using the cross-covariance at |h|=0 and the auto-covariance at lag series h. The mosaic model, multicolocated kriging and the linear model of coregionalization are examined in this context. A data analytic method to examine whether simple kriging of components of a multivariate random process is equivalent to its cokriging is given 相似文献
20.
地震分析中人工边界处理与地震动输入方法研究 总被引：8，自引：0，他引：8
基于柱面波波动方程,推导建立了适用于土-结构地震动力相互作用分析的地震动输入和人工边界的处理方法.其中,地震动的输入是通过在人工边界上施加等效节点力来实现的,等效节点力的大小与入射地震波波速成正比;而人工边界的处理方法使得人工边界条件不仅在时间上是局部的,而且在空间上也是局部的.这种处理方法简单、有效,物理意义清晰,且很容易在有限元法中实现,结合Newmark时间积分是无条件稳定的.为了验证方法的有效性和精度,给出了两个算例,分别用于检验人工边界条件的性能以及地震动输入方法的正确性.算例分析结果表明,所提出的方法是十分有效的. 相似文献