摘要
工程实践中,泥炭质土由于富含有机质,具有高含水量、低密度、超高压缩性以及低强度的异常力学特性,往往被视为问题土。针对昆明地区交通荷载作用下泥炭质土的动力响应特征,选取滇池草海附近典型泥炭质土,开展考虑围压水平、动应力幅值以及静偏应力影响的不排水循环三轴试验,研究该土的长期累积变形特性。研究表明:研究土样具有典型泥炭质土特征,表现为含水量181.5%~259.3%,密度1.10~1.22 g/cm^3、有机质含量29.9%~53.0%,有机物质分解度较高;动应力幅值和静偏应力对昆明泥炭质土的长期动力特性影响显著,大动应力幅值和静偏应力加剧累积变形和孔压的发展,同时,当动应力水平小而静偏应力大时,累积塑性变形的发展速度反而大;虽然初始围压对累积变形影响较小,但对残余孔压的影响显著。此外,基于双对数坐标下累积应变速率与循环周次关系以及前人研究方法,建立了泥炭质土累积塑性应变与动荷载循环周次间的经验关系。
Peaty soils are generally viewed as ＂problematic＂ soils for their high organic matter content, high water contents, low bulk density, high compressibility and low strength characteristics. The long-term accumulative behaviour of peaty soils subjected to traffic loads was studied through a series of cyclic triaxial compression tests on the samples retrieved from the site nearby Caohai on the northern side of Lake Dian. The variables including the confining stress level, the amplitude of dynamic stress and the static deviatoric stress were taken into account in this study. It was found that the tested samples were typical peaty soil, which had the initial water contents of 181.5% - 259.3%, the initial densities of 1.10 - 1.22 g/cm^3, the organic contents of 34.7% - 44.2%. The organic matters were highly decomposed. Both the amplitude of dynamic stress and static deviatoric stress had the distinct influences on the developments of permanent axial strain and pore water pressure. The larger amplitude of dynamic stress or the static deviatoric stress accelerated the developments of the permanent axial strain and pore water pressure. The development of permanent axial strain was faster when a lower dynamic stress and a larger static deviatoric stress were applied, in contrast to the case that a larger dynamic stress and a lower static stress were applied. The initial confining stress level appeared to have a little effect on the development of permanent axial strain, while it had a significant impact on the accumulation of pore water pressure. In addition, an empirical relation between the accumulative plastic strain and loading cycles was presented based on the relationships between the permanent axial strain rate and loading cycles under dual logarithmic coordinates as well as the previous studies.
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2017年第5期1247-1255,共9页
Chinese Journal of Rock Mechanics and Engineering
基金
国家自然科学基金资助项目(41402277
41672293)
国家重点基础研究发展计划(973)项目(2010CB732101)~~
关键词
土力学
泥炭质土
有机质
土动力学
静偏应力
长期循环荷载
soil mechanics
peaty soil
organic matter
soil dynamics
static deviatoric stress
long-term cyclicloading
