摘要
水敏感性和结构性是黄土区别于其他类型土的主要特点,得到了广泛的研究,但大多数试验研究都采用垂直方向制备的试样,仅考虑了黄土垂直方向的力学特性,这对于以承受上部垂直荷载为主的黄土地基基础等工程类型来说是合理和准确的,而对于受力状态较为复杂的边坡和隧道及地下结构等工程类型,黄土力学性质的各向异性可能更为重要。分别从垂直向和水平向制取兰州Q4黄土的原状土试样,通过三轴剪切试验研究了其抗剪强度和变形参数在不同围压下和不同方向上的差异性,并与直剪试验获得的强度参数进行对比。结果表明:兰州Q4黄土力学性质的各向异性是较为显著的,强度方面的差异主要体现在黏聚力,而内摩擦角的差异性较小;变形特征具有随围压增加而从脆性向塑性转化的特点,垂直方向的变形模量比水平方向的变形模量平均要大2倍左右。用黄土的结构性强度及其形成机制解释了试验结果,认为黄土力学性质的各向异性特点是其结构性的另一种表现方式,应重视黄土在不同方向上强度和变形特征的差异性,以获得更安全合理的参数。
Water-sensitivity and structural property of loess which have been widely studied are the two marked characteristics compared with the other soils. But most test researches are always conducted by using soil samples taken only in the vertical direction, which means only the vertical mechanical behaviour is taken into account. It is absolutely both reasonable and correct to study the vertical mechanical properties of loess mainly loaded vertically by upper foundations, but for those constructions with complicated stress state at different parts such as loess slopes, tunnels and/or underground structures, the anisotropy of loess might be more significant. The undisturbed Q4 loess in Lanzhou is sampled both from vertical and horizontal directions; then triaxial shear tests are conducted to investigate the difference of shear strength and deformation parameters under different confining pressures. The shear strength parameters obtained from triaxial test are also compared with those from direct shear test. The test results show that the anisotropy in mechanical behaviours of Q4 loess in Lanzhou is remarkable. The anisotropy in shear strength is mainly externalized by cohesion but the friction is nearly the same. Both the vertical and horizontal deformations can be characterized by conversion of brittle failure to plastic failure while the confining pressures are increasing. The difference in deformation modulus of loess between vertical and horizontal directions is quite obvious, i.e. the deformation modulus in vertical directions is averagely twice than that in horizontal directions. The test results are explained by using the structural strength and corresponding forming mechanism of loess. The anisotropy in mechanical behaviours, of loess can be considered as another type of structural property of loess, which should be paid more attention in order to get more safe and reasonable parameters.
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2012年第1期17-23,共7页
Rock and Soil Mechanics
基金
铁道部科技研究开发计划课题资助项目(No.2005K001-D(G)-1)
兰州交通大学"青蓝"人才工程基金(No.QL-08-19A)
关键词
黄土
各向异性
结构性
抗剪强度
变形模量
loess
anisotropy
structural property
shear strength
deformation modulus
作者简介
梁庆国，男，1976年生，博士，副教授，主要从事岩土体工程方面的教学和科研工作。E-mail：lqg_39@163．com
