基于数字图像的非均质岩土工程材料的数值分析方法

提出了一种基于数字图像的非均质岩土工程结构的二维数值分析方法。以花岗岩为例,先将岩石的表面图像导入计算机中;然后采用基于彩色空间的数字图像技术将组成花岗岩的几种主要材料:长石、石英和黑云母一一分辨出来并再现岩石的细观结构;再通过一个简单的线性转换,将图像细观结构转换为矢量细观结构;最后,岩石的矢量细观结构可以与数值计算方法--有限元法或有限差分法结合,从而实现非均质岩石材料的力学分析。采用有限差分法FLAC程序来分析岩石的破坏过程。传统室内试验数值模拟表明材料的细观结构对应力分布和破坏模式有着明显的影响,基于数字图像的数值分析方法可以真实地实现岩土工程材料的非均质分析。     

岩土类材料的统一强度理论及其应用

岩土类材料的强度理论是土木、水利、铁道、矿业等工程中的一个重要的基本问题。以往各种强度理论一般只适用于某一类特定的材料。本文对材料强度理论不作任何假设（如外凸性等），直接根据材料单向拉伸和单向压缩强度极限（也可用岩土工程中常用的材料强度参数Ｃ＿０和φ），从一个统一的单元体模型出发，考虑所有应力分量以及它们对材料破坏的不同影响，建立一个能够适用于各类材料的统一强度理论和统一形式的数学表达式。它包含了现有各种主要强度理论和一些尚未表达过的新的强度理论。按统一强度理论表达式得出的两大族８种强度准则可以适用于各种岩土类材料，并可由此蜕化得出两族适用于金属材料的统一形式屈服准则。     

岩土材料弹性力学模型与计算方法

 岩土材料内摩擦性质是岩土的基本力学性质之一，无论岩土处于何种受力状态，都应考虑岩土体的内摩擦力。然而，至今只有岩土极限分析与塑性力学中考虑岩土体的内摩擦力，而在弹性理论与能量理论等诸方面均未体现。岩土体无论是处于塑性状态还是弹性状态，都存在着内摩擦力，为此建立岩土材料弹性力学的摩擦体力学单元。基于土体试验提出黏聚力先发挥，摩擦力随变形逐渐发挥，并假设摩擦因数与应变成正比，由此确定摩擦力的计算，最后仿效线弹性力学计算方法，但此时摩擦体的剪切模量G已非常数，从而形成摩擦体的非线性弹性力学计算方法。算例表明，按该方法计算出的弹性地基上的位移和剪应力小于传统方法计算出的位移和应力值，这比较符合实际情况，表明采用摩擦体力学单元对岩土材料是合适的。     

新型土工材料在加筋土工程中的应用

通过在山西临汾至侯马高速公路的工程实践 ,解决了加筋挡土墙的防腐问题 ,且简化了施工工艺 ,为新型土工材料的推广应用 ,提供了有价值的施工经验和技术依据。     

Strength-increase mechanism and microstructural characteristics of a biotreated geomaterial

Microbially induced calcite precipitation (MICP) is a recently proposed method that is environmentally friendly and has considerable potential applications in artificial biotreated geomaterials. New artificial biotreated geomaterials are produced based on the MICP technology for different parent soils. The purpose of this study is to explore the strength-increase mechanism and microstructural characteristics of the biotreated geomaterial through a series of experiments. The results show that longer mineralization time results in higher-strength biotreated geomaterial. The strength growth rate rapidly increases in the beginning and remains stable afterwards. The calcium ion content significantly increases with the extended mineralization time. When standard sand was used as a parent soil, the calcium ion content increased to a factor of 39 after 7 days. The bacterial cells with attached calcium ions serve as the nucleus of crystallization and fill the pore space. When fine sand was used as a parent soil, the calcium ion content increased to only a factor of 7 after 7 days of mineralization. The nucleus of crystallization could not normally grow because of the limited pore space. The porosity and variation in porosity are clearly affected by the parent soil. Therefore, the strength of the biotreated geomaterial is affected by the parent soil properties, mineralization time, and granular material pore space. This paper provides a basis for theory and experiments for biotreated geomaterials in future engineering practice.     

椭球形结构块破损过程的数学描述

把结构性岩土材料理想为由椭球形结构块组成的堆积体。在受力的过程中,椭球体逐渐破碎并转化为碎屑物。椭球体可能有压碎、剪裂和弯裂3种破坏模式,结构体的破坏过程可分成5个阶段,本文推导了相应的破坏准则。给出了椭球体在一种规则的堆积方式下的应力应变曲线和破损参数的演化规律。这些曲线与堆积体的受力方向有关,从而解释了这种材料的各向异性。     

岩土破损力学—— 结构类型与荷载分担

岩土破损力学是不同于岩土断裂力学和岩土损伤力学的新理论。介绍了岩土破损力学中分宏观、细观和微观3个层次的研究方法，把结构性岩土材料划分为碎裂结构、散块结构、包络结构和浮悬结构4种类型，并讨论了分别确定结构体和结构面分担荷载的基本原则。     

干湿循环下复合固废填料配比对强度的影响

通过对不同配比的9组复合固废轻质填料(简称轻质填料)试样在不同干湿循环次数下的单轴抗压强度试验,分析了干湿循环下各组分掺入比对轻质填料抗压强度的影响.结果表明:轻质填料经历8次干湿循环后仍有较好的力学性能,达到或超过水泥土的强度要求.随着水泥掺量的增加,轻质填料在早期干湿循环过程中强度提高,有助于后期抗干湿循环.适量掺...     

Basic characteristics and development of yield criteria for geomaterials

The yield criteria of geomaterials play a crucial role in studying and designing the strength of materials and structures.The basic characteristics of yield criteria for geomaterials need to be studied under the framework of continuum mechanics.These characteristics include the effects of strength difference（SD） of materials in tension and compression,normal stress,intermediate principal stress,intermediate principal shear stress,hydrostatic stress,twin-shear stresses,and the convexity of yield surface.Most of the proposed yield criteria possess only one or some of these basic characteristics.For example,the Tresca yield criterion considers only single-shear stress effect,and ignores the effect of SD,normal stress,intermediate principal stress,intermediate principal shear stress,hydrostatic stress,and twin-shear stresses.The Mohr-Coulomb yield criterion accounts for the effect of SD,normal stress,single-shear stress and hydrostatic stress,but disregards the effect of intermediate principal stress,intermediate principal shear stress,and twin-shear stresses.The basic characteristics remain to be fully addressed in the development of yield criterion.In this paper,we propose a new yield criterion with three features,that is,newly developed,better than existing criteria and ready for application.It is shown that the proposed criterion performs better than the existing ones and is ready for application.The development of mechanical models for various yield criteria and the applications of the unified strength theory to engineering are also summarized.According to a new tetragonal mechanical model,a tension-cut condition is added to the unified strength theory.The unified strength theory is extended to the tension-tension region.     

Geomaterials: their application to environmental remediation

Geomaterials are materials inspired by geological systems originating from the billion years long history of the Earth. This article reviews three important classes of geomaterials. The first one is smectites—layered silicates with a cation-exchange capacity. Smectites are useful for removing pollutants and as intercalation compounds, catalysts and polymer nanocomposites. The second class is layered double hydroxides (LDHs). They have an anion-exchange capacity and are used as catalysts, catalyst precursors, sorbents and scavengers for halogens. The third class of geomaterials is zeolites—microporous materials with a cation-exchange capacity which are used for removing harmful cations. Zeolite composites with LDHs can absorb ammonium and phosphate ions in rivers and lakes, whereas zeolite/apatite composites can immobilize the radioactive iodine. These geomaterials are essential for environmental remediation.