双孔隙结构重塑非饱和膨胀土的抗剪强度特性  

Shear strength behaviors of unsaturated expansive soils with dual-porosity structure

作　　者：钱建固[1,2] 林志强 QIAN Jiangu;LIN Zhiqiang(Department of Geotechnical Engineering,Tongji University,Shanghai 200092,China;Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education,Tongji University,Shanghai 200092,China)

机构地区：[1]同济大学地下建筑与工程系,上海200092 [2]同济大学岩土及地下工程教育部重点实验室,上海200092

出　　处：《岩土工程学报》2023年第3期486-494,共9页Chinese Journal of Geotechnical Engineering

基　　金：国家自然科学基金项目(41877252)。

摘　　要：针对具有双孔隙结构(即集聚体间和集聚体内孔隙)及双峰持水曲线的内乡膨胀土压实样,进行了一系列宽广吸力范围内非饱和土三轴剪切试验及峰值强度演化规律的研究。试验结果表明:在净应力相同的条件下,中低吸力下的应力应变关系为应变硬化,伴随明显的剪缩变形;高吸力下为峰值后软化,在经历了1%~3%的体积收缩变形之后开始出现剪胀。试样的脆性随吸力的增加而增长,在中低吸力下呈桶形或中心鼓形的延性破坏模式,在高吸力下发生应变局部化现象,伴随着明显的剪切带出现。此外,脆性增加了峰后软化的幅度,表现为峰值偏应力与残余破坏状态之间的差值增大。基于区分毛细和吸附作用的双峰持水曲线(SWRC)模型,针对内乡膨胀土与其它具有双孔隙结构及双峰SWRC的土体在毛细吸应力空间进行了峰值强度分析,将吸力从孔隙应力尺度乘以毛细饱和度变为骨架应力尺度时,其呈现的强度包络线为双折线特征。理论分析表明,低吸力范围内,双孔隙结构非饱和土的抗剪强度由饱和强度与毛细吸应力贡献;高吸力范围内,抗剪强度应由饱和强度、毛细吸应力与胶结作用提供。A comprehensive set of experimental tests over a wide suction range and mechanism analysis are carried out to study the shear strength of Neixiang expansive soil with dual-porosity structure and bimodal soil-water retention curve(SWRC).Under the low and medium suction range, all the deviator stress versus strain curves show the strain-hardening behaviors with the shear contraction. Under the high suction range, the deviator stress versus strain curves show the post-peak strain softening stress-strain responses and the initial contraction of 1%~3% followed by the shear dilation. The specimens become stiffer with the increase of suction, and show a ductile failure mode with barrel shape or bulging at center under the low to medium suction ranges and strain localization with sliding surface under the high suction ranges. Also, the brittleness increases the amplitude of the post-peak softening, which is consistent with the increase of the difference between the magnitude of peak and the residual shear strength. Based on the bimodal SWRC considering capillarity and adsorption, the shear strength is analyzed and investigated in the capillary suction stress space for the soils with dual-porosity structure and bimodal SWRC. It is concluded that the strength shows the bi-linear characteristics if the capillary saturation has been used to upscale the suction from pore-scale stress to macroscopic one. The theoretical studies show that for the soils with double-porosity structure, the capillary suction stress under the low suction range can better characterize the macroscopic effective stress transferred between skeletons.The peak shear strength under the high suction range is provided by capillarity and closely related to the intra-aggregate cementation.

关 键 词：非饱和土 双孔隙结构 土体持水曲线 抗剪强度 毛细 胶结 

分 类 号：TU432[建筑科学—岩土工程]