滇池湖相沉积泥炭土参数测定与剪切特性研究

Parameter determination and shear characteristics of lacustrine sedimentary peat soil in Dianchi Lake

有机质含量和含水率对泥炭及泥炭质土(简称泥炭土)的力学性质及工程特性影响都很大,但现有的规范、规程及标准对高有机质含量土的含水率(ω)及有机质含量(w u)测定标准不明确,各单位测试结果差异较大。为明确高有机质含量土的ω及w u测定标准,开展不同灼烧温度及灼烧时间下的测试试验。滇池湖相沉积土的场地一般都有3~5层层状分布的泥炭土,现对不同埋深的5层泥炭土进行从低至高围压下的三轴固结不排水(CU)试验,探究不同埋深及围压下其应力-应变的变化规律及演化机理。试验发现:泥炭土随围压增大应力-应变关系曲线呈现“分层”现象,最大偏应力对应的应变随深度增加而减小,线型随围压和土样埋深而发生改变,孔隙压力系数总体随着深度的增加而减小,并提出CU试验泥炭土破坏应变控制标准。以上研究进一步加深了对泥炭土力学特性的认识,也为明确ω及w u的测定标准提供了试验依据。

Organic matter content(w u)and water content(ω)greatly influence the mechanical properties and engineering characteristics of peat and peaty soil(peat soil for short).However,the determination standards ofωand w u of soil with high organic matter content are unclear in existing codes,procedures,and standards,and the test results vary greatly among different units.To define the determination standards ofωand w u of high organic content soil,tests were performed under different burning temperatures and burning times.Generally,the site of lacustrine sedimentary soil in Dianchi Lake has 3-5 layers of peat soil.To explore the variation law and evolution mechanism of stress and strain under different buried depths and confining pressures,a series of triaxial consolidation undrained(CU)tests was performed on five layers of peat soil with different buried depths under low to high confining pressures.The test results show that the stress-strain curve of peat soil presents a“layered”phenomenon with increasing confining pressure;the strain corresponding to the maximum deviatoric stress decreases with increasing depth,and the curve shape changes with the confining pressure and buried depth of soil samples;the pore pressure coefficient decreases with increasing depth.Moreover,the control standard of failure strain of peat soil in the CU test is proposed.This research further deepens the understanding of the mechanical properties of peat soil and provides an experimental basis for determiningωand w u standards.