PARALLEL STOCHASTIC ANALYSIS FOR GEO-ENGINEERING

[如下：1.可靠性是不会发生故障的概率；2.特征值是材料属性的单个值，当用于确定性分析时，对于给定的可靠性水平，它将给出与随机分析相同的响应；3.折减系数是指将平均属性值按比例调整的系数(从0.0到1.0)。]拟议的研究集中于这样一个事实，即自然材料是可变的，这种变异性的表示似乎对现实地理解某些岩土工程和地质环境问题至关重要。为了说明的目的，选择了一个具体的问题。这项调查需要一名研究助理，他将专注于：(A)将现有的有限元程序从串行环境转换为并行环境；(B)使用这些优化的程序来研究非均质性对三维边坡稳定性的影响。总成本为91K，外加名义服务成本104K，分为两个部分：1.粘土路基边坡的稳定性。这一简单的(总应力)应用将确定不排水剪切强度的基于可靠性的折减系数，由此可以得出基于可靠性的特征值。特别令人感兴趣的是基于2-D和3-D分析的减少系数之间的比较：即2-D方法有多保守，通过以真正的3-D响应为基础的减少系数将获得哪些经济收益？这项研究还将调查非均质性对破坏机制演变的影响以及对潜在滑移所涉及的土体体积的影响。水下填砂边坡的稳定性(使用耦合有效应力方法)。第一阶段将比较长斜坡的二维和三维响应。(因此，除所得的折减系数是按土的摩擦角计算外，其范围将与黏土路缘斜坡的折减系数相似。)第二阶段将考虑Nerlerk水下护堤。该结构的设计是为了形成加拿大波弗特海海底石油勘探平台的一部分，但在施工期间(26米高)由于静态液化而失败。这个复杂的3-D应用程序将模拟护堤的结构，并将导致预测故障概率、发生故障的护堤高度以及潜在滑坡体的几何形状和体积。(请注意，有详细的现场测量数据可供比较。)拟议的研究将展示一种新的、更有意义的方法来表示地质结构响应，稳定性(可靠性)的定义现在反映了正在分析的材料的可变性质。地质环境应用被视为并行随机分析将蓬勃发展的一个特殊领域。

[In what follows: 1. Reliability is the probability that failure will not occur; 2. A characteristic value is that single value of a material property which, when used in a deterministic analysis, will give the same response as a stochastic analysis for a given level of reliability; 3. A reduction factor is that factor (from 0.0 to 1.0) by which the mean property value is scaled to give the characteristic value.]The proposed research concentrates on the fact that natural materials are variable and that representation of this variability appears crucial to getting a realistic understanding of certain geotechnical and geo-environmental problems. A specific problem is chosen for illustrative purposes. The investigation requires one Research Associate, who will focus on: (a) converting existing finite element codes from serial to parallel environments; (b) using these optimised codes to investigate the influence of heterogeneity on 3-D slope stability. It involves a total cost of 91k plus notional service costs of 104k, and is divided into two parts:1. The stability of cut slopes in clay. This simple (total stress) application will determine reliability-based reduction factors for undrained shear strength, from which reliability-based characteristic values may be derived. Of particular interest will be the comparison between reduction factors based on 2-D and 3-D analyses: i.e. how conservative is the 2-D approach, and what economies are to be gained through basing reduction factors on the true 3-D response? The study will also investigate the influence of heterogeneity on the evolution of failure mechanisms and on the volumes of soil involved in potential slides.2. The stability of underwater sandfill slopes (using a coupled effective stress approach). The first stage will be to compare 2-D and 3-D responses for long slopes. (Hence, the remit will be similar to that for cut slopes in clay, except that the derived reduction factors will be for soil friction angle.) The second stage will consider the Nerlerk underwater berm. This structure was designed to form part of a bottom-founded oil exploration platform in the Canadian Beaufort Sea, but failed during construction (at a height of 26 m) due to static liquefaction. This complicated 3-D application will simulate the construction of the berm, and will result in predictions of the probability of failure, the height of the berm at which failure occurs, and the geometries and volumes of potential slides. (Note that there are detailed field measurements available for comparison.) Significantly, it will provide a benchmark against which previous, current and future 2-D investigations may be properly quantified.The proposed research will demonstrate a new and more meaningful approach to representing geo-structural response, with the definition of stability (reliability) now reflecting the variable nature of the material which is being analysed. Geo-environmental applications are seen as a particular area in which parallel stochastic analysis will flourish.