基于四叉树网格和多边形比例边界有限元方法的岩土工程非线性静动力分析

有限单元法(FEM)作为强大的数值分析技术广泛应用于岩土工程结构数值模拟。由于传统有限元的单元形状局限性以及岩土工程模型的复杂性(分层施工模拟、复杂材料分区等),较难编制通用的高质量网格剖分算法,使得模型网格生成消耗整个分析过程的大部分时间,阻碍快速自动化分析进程。采用四叉树网格剖分技术,联合非线性多边形比例边界有限元(PSBFEM)方法,发展了一种可用于岩土工程结构的快速建模和数值分析方法。对某心墙坝进行了静动力数值模拟,并与传统有限元结果对比验证了其正确性。研究表明,文中方法具有使用简便、网格灵活、生成速度快、质量高等特点,可以大幅降低累赘繁琐的人工干涉,为工程结构快速设计–优化提供有力的技术手段。该方法扩展至三维结构将具有更大的研究价值和工程意义。     

覆盖型岩溶塌陷的空间预测与评价

针对危害性最大的覆盖型岩溶,建立考虑土盖层厚度和岩土体类型的典型岩溶地质结构模型,分析其在地下水位升降及地表水入渗情况下的塌陷机制。结合具体岩溶工程问题,提出“物理探测－工程勘察－岩、土物理力学试验－数值模拟－监测评价”的岩溶塌陷空间预测方法,并将该方法应用于湖北省黄石市一处典型覆盖型岩溶灾害区。在物理勘探、工程勘察和岩土物理力学试验的基础上进行的岩溶塌陷数值模拟表明,相对于地下水位快速升降,因地表水入渗导致黏土盖层软化引起的地面沉降更大。依据数值模拟结果,结合研究区地面及房屋裂缝的发展情况,划分出塌陷危险区的具体空间范围。实践证明,该岩溶塌陷空间预测方法具有较强的可操作性和较高的可靠性,可作为类似工程问题的研究方法予以推广     

海岸岩土工程的物理与数值模拟方法

采用物理模型试验来再现实际现象,验证数值模拟方法的有效性;同时采用数值模拟来弥补离心模型试验的缺陷,揭示模型试验规律,评价实际海岸岩土-结构系统在不同工况下的变形与强度稳定性及其变化.并简要地介绍了针对防波堤土工织物加筋垫层作用机理研究、黄骅港外航道防沙堤工程安全性评价、上海洋山港浅置式大圆筒结构试验段工程安全性评价三个具体项目进行评价的成果,初步展现了物理模型试验与数值模拟方法在海岸岩土工程的机理研究、方案论证、结构与施工优化、结构安全性评价等方面所能发挥的重要作用和广阔的应用前景.     

岩土力学数值分析方法研究

随着岩土工程领域的不断扩展与延伸,岩土力学数值分析方法得到了迅速发展,出现了各种各样的数值分析方法。将岩土力学常用的数值分析方法分为连续变形分析方法与非连续变形分析方法两大类,对各种方法的研究现状和最新进展进行了评述,着重介绍了各种方法的优缺点,并提出了解决问题的思路、方法和建议。     

秦望山隧道南口高陡岩质边坡稳定性分析及治理效果评价

滑坡作为一种常见的地质灾害严重影响工程的安全与稳定和人类的生命财产安全。边坡稳定性受岩土体力学性质、地形地貌条件和周边环境等因素影响。本文以秦望山岩质边坡为研究对象,采用3DEC数值模拟软件分析了边坡治理前后不同工况下边坡的稳定性。稳定性分析结果表明治理加固后各工况下坡体位移均明显减小;通过对治理后滑坡的裂缝变形和锚索应力监测数据进行分析,验证了边坡治理措施的有效性。     

基于参数反演的边坡地下水渗流数值模拟

渗流是影响岩土工程边坡稳定性的重要因素,对不同工况下岩土体边坡地下水渗流规律进行数值模拟,弄清其动态变化规律,对于边坡稳定性分析、支护设计、工程防排水措施的制定等都有重要的意义。以龙滩水电站左岸进水口边坡为研究对象,通过免疫进化规划算法,得到了边坡岩体渗流场参数。在此基础上,对洪水期、枯水期情况下地下水渗流状态进行了数值模拟,通过对比分析,研究了不同河床水位情况下地下水渗流变化规律,从而为边坡稳定性预测奠定了理论基础。     

岩土破损力学:结构块破损机制与二元介质模型

沈珠江等在总结岩土材料的基本特性、分析理论和研究方法的基础上,提出了岩土破损力学理论框架和二元介质模型概念。基于岩土二元介质模型思想,近年来在试验、理论和数值模拟方面对结构性岩土材料进行了详细研究。通过对棒状和棱柱状结构块试件的平面试验,探讨了结构性岩土材料的破损机制,并发现了在受荷过程中结构块逐渐破损并转化为软弱带二者共同抵抗外部作用,即验证了二元介质模型对结构性岩土材料力学抽象的正确性;扩展了岩土二元介质模型对岩土材料的脆性变化进行了模拟,并与结构性土和砂岩的三轴试验结果进行了验证;基于二元介质模型概念,发展了一种模拟岩土材料破损过程的细观数值方法,同时提出了适用于结构性岩土材料的强度准则。     

自然单元法在岩土工程中应用两例

自然单元法(NEM)是较近出现的一种无网格方法,其形函数兼有无网格的特点和传统有限元的优点,是一种理想的适合岩土工程问题计算的新型数值方法。介绍了自然单元法的基本原理和特性,并讨论了其在岩土工程中的具体应用。将Goodman单元引入自然单元法以实现对不连续面的模拟,研究表明,在NEM中加入节理单元的总体原则和具体的实施细节与FEM中完全相同;而在一般的无网格方法中,则稍微复杂一点。为了实现对岩土工程中常见的无限域或半无限域问题的模拟,引入了无界单元;由于自然单元法的特性,自然单元法和无界元可实现无缝“耦合”。具体的数值算例验证了上述思路。     

Midas／GTS软件在边坡三维稳定分析中的应用

Midas／GTS岩土数值模拟软件具有简洁的界面、前后处理功能强大的岩土材料模型库,能满足大部分岩土体的破坏模式。建立工程边坡的三维数值模型,并对其计算分析．结果接近真实情况,且计算结果相对安全。本文采用该软件与有限元强度折减法相结合模式,对三维边坡实例的各种工况进行数值模拟,得到边坡的最大剪应变、最大剪应力出现的部位和数值大小以及边坡整体安全系数,由此确定边坡的薄弱带和潜在滑面,能客观反映边坡稳定性。     

岩基载荷试验影响因素分析

在大型工程的岩土工程勘察中,如何确定岩石地基的承载力,直接影响到建筑的质量、造价和进度。载荷试验作为模拟建筑物基础受力条件的试验,科学、直观地提供了地基的承载力和变形模量,给设计部门提供了不可或缺的设计依据。然而,岩基载荷试验结果受基岩埋深及孔径的影响尚不清楚。利用ABAQUS有限元分析软件,对深层岩基载荷试验影响因素进行数值模拟分析,得出的结论可为今后岩土工程勘察提供借鉴。     

基于孔压静力触探的岩土参数正态性检验方法对比

岩土参数的正态分布是岩土工程可靠分析的基本假定之一。目前,岩土工程参数的正态性检验以KS （Kolmogorov-Smirnov）检验为主,然而诸多研究表明,对于小样本数据,KS检验的正态性检验结果并不可靠。本文以废黄河泛滥沉积相粉土中的孔压静力触探（CPTU）锥尖阻力q_t数据为研究对象,首先采用ANOVA （方差分析）检验,从CPTU测试资料中进行总体的样本筛选,然后应用SW （Shapiro-Wilk）检验、KS检验、LF （Lilliefors）检验和AD （Anderson-Darling）检验等4种正态性检验方法,在不同样本容量条件下,对测试数据进行正态性检验评价。当测试数据的样本容量充足时,分析结果表明：SW检验结果最为严格,KS检验结果最不保守,而LF检验和AD检验的严格性介于两者之间;对于常规岩土工程设计,采用KS检验结果即可满足稳定性分析要求,对于复杂岩土工程设计,采用SW检验对设计参数进行正态性检验,可降低设计的不确定性。     

Analysis and Design of an Underground Portal in Lateritic Soils

This paper presents a case study of the analysis and design of slopes for the portal of an underground crude oil storage cavern site. The site selected for the slope study is characterized by residual soils and granitic rock formations, located in the southwestern part of India. It is observed that in tropical residual soils, most hillslope failures are caused by rainfall and thus it is important to consider hydrological conditions when attempting to analyze the stability of slopes in such material. Combinations of shallow slopes with lower overburden and high steep hillslope with large overburden were considered in the present study along with varying combinations of lateritic soils and weathered rock formations. The paper discusses the various investigations carried out to define the geotechnical properties of lateritic soil and weathered rock, followed by numerical modelling and remedial measures adopted to ensure the stability of slopes during design and construction phase. Since analysis and design procedures for such residual soils are not well established, comprehensive geological and geotechnical investigations were carried out prior to numerical model development for carrying out finite element studies in order to ascertain long term stability of slopes under differing ground conditions. The results of the stability analysis indicated that slope under existing condition were potentially unstable under rainy conditions and specific supporting measures were planned to ensure stability. Several alternatives were examined for improving the stability of slope taking into consideration existing facilities, space available for mobilization of equipments and environmental conditions in reference to specific project requirements. The convergence pattern obtained from geotechnical monitoring using optical targets along the slopes did not showed any alarming movement for over a year.     

A FORM-based approach for probabilistic analysis in geotechnics: Application to a reinforced concrete drainage culvert

As numerical models are increasingly used as a design tool in geotechnical engineering, it is highly desirable if geotechnical reliability analysis can be conducted based on numeral models. Currently, the practical use of geotechnical reliability analysis-based numerical models is still quite limited. In this study, an easy to access method is derived to conduct geotechnical reliability analysis based on numerical models. To facilitate its application, a procedure is outlined to implement the suggested method such that geotechnical reliability analysis can be automated using existing geotechnical numerical packages. The procedure is illustrated in detail with an example, and the source codes provided can be easily adapted to analyze other similar problems. The method described in this paper is used to study the reliability of a deteriorating reinforced concrete drainage culvert in Shanghai, China. The suggested method provides a convenient means for reliability analysis of complex geotechnical problems.     

Applications of Particle Swarm Optimization in Geotechnical Engineering: A Comprehensive Review

Particle swarm optimization (PSO) is an evolutionary computation approach to solve nonlinear global optimization problems. The PSO idea was made based on simulation of a simplified social system, the graceful but unpredictable choreography of birds flock. This system is initialized with a population of random solutions that are updated during iterations. Over the last few years, PSO has been extensively applied in various geotechnical engineering aspects such as slope stability analysis, pile and foundation engineering, rock and soil mechanics, and tunneling and underground space design. A review on the literature shows that PSO has utilized more widely in geotechnical engineering compared with other civil engineering disciplines. This is due to comprehensive uncertainty and complexity of problems in geotechnical engineering which can be solved by using the PSO abilities in solving the complex and multi-dimensional problems. This paper provides a comprehensive review on the applicability, advantages and limitation of PSO in different disciplines of geotechnical engineering to provide an insight to an alternative and superior optimization method compared with the conventional optimization techniques for geotechnical engineers.     

Application of the artificial bee colony algorithm-based projection pursuit method in statistical rock mass stability estimation

Because of the complexity of factors that affect rock mass stability, the design and decision-making in related engineering cannot rely solely on theoretical analysis and numerical calculation, but depend on the comprehensive judgment of experts. In pursuit of a statistical approach that may improve this disparity, an artificial bee colony algorithm-based projection pursuit (ABC-PP) method is presented for rock mass stability determination. The ABC-PP method is a powerful tool to deal with high-dimension problems, which characterize rock mass stability assessment practice. Two experiments are employed to demonstrate the efficiency of the ABC-PP method. In the first case, the state of stability is classified at two levels: stable and failed, whereas in the second case stability is classified at five levels (1–5) to test the capability of multi-level prediction of the ABC-PP method. Results show that the ABC-PP method could predict the rock mass stability accurately and may also provide the relative importance of specific controls on stability.     

地下洞室岩体变形模量的尺寸效应研究

变形参数是岩体工程变形计算、稳定性评价的前提,岩体变形参数的合理取值一直是岩土工程界关注的热点和难点之一.由于岩体力学参数存在随研究尺度不同而变化的特性,被称之为岩体力学参数的尺寸效应,因此由室内试验获取的岩石力学参数,甚至现场试验获取的岩体力学参数,均代表不了岩体工程尺度实际的力学特性,不能直接用于工程实际.为获取能...     

市政道路工程勘察资料的时效性分析和探讨

城市化的发展,使市政道路改造工程越来越多,如何科学有效地利用拟建期的勘察资料,节约勘察成本,成为工程勘察关注的焦点。通过对场地地形地貌和地质构造、地层和水文地质条件、岩土物理力学性质、场地稳定性评价和地震效应、岩土工程重点分析评价等岩土工程要素进行分析,对比前后各要素,探讨勘察资料的时效性,进而确定勘察点布置和深度,以及取土（水）样和原位测试工作量。最后以具体工程为例,探讨勘察要点,指出利用拟建期的勘察资料应主要考虑4.0m以内的地层变化,重点勘察路基破损的路段。     

岩土综合勘察技术在风力发电场地基工程中的应用

以风力发电场工程勘察为例,介绍了岩土综合勘查技术在不同的地形地貌、地层和水文地质条件中的应用。由于拟建工程的风机塔基大多数坐落于地势较高的山坡处,故采取以井探、槽探方法为主,工程物探为辅的勘察方法;对于位于平缓地带的办公区、生活区和变电站的场地勘察,则运用了土层剪切波速测试和静力触探试验的方法。通过各种岩土勘察技术的应用,掌握了该场地的地基土层物理力学性质指标及地基适宜性。地基变形监测和建筑物的稳定性检测结果显示,应用该方法所提供的岩土设计参数和各种施工方案经济合理、目的性和针对性强。