膨胀土土水特征曲线的覆土压力效应研究

doi:10.13722/j.cnki.jrme.2019.0895

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摘要为研究膨胀土的应力状态对其持水特性和变形特征的影响，以南阳膨胀土为对象，模拟不同一维覆土压力(0，40，100，200 kPa)下膨胀土的土体水分特征，提出考虑覆土压力效应的土–水特征曲线(soil-water characteristic curve，SWCC)模型并探讨方程拟合过程。结果表明：(1) 各覆土压力下南阳膨胀土含水率随基质吸力呈规律性变化并表现出“双峰”形态，膨胀土持水量随覆土压力的增大而减少，200 kPa覆土压力下边界效应段II显著延长。(2) 土体孔隙比均随覆土压力和基质吸力的增大而减小，覆土压力引起的孔隙比降幅是基质吸力引起的孔隙比降幅的2.12倍，应力作用下孔隙体积变化规律由覆土压力导致的粒间孔隙失水占主导地位。(3) 基于分段思想改进双峰Fredlund-Xing方程，对南阳膨胀土实测数据进行曲线拟合，拟合参数a1和n1能有效反映不同覆土压力下SWCC1的特征点及特征吸力域的变化规律；对于SWCC2，覆土压力的影响减弱，各参数与覆土压力关系不显著。研究可为定量表征膨胀土的水力–力学耦合效应和双峰SWCC模型的建立提供参考。

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	王晓琪
	许冲
	汪时机
	李贤

关键词 ：土力学, 膨胀土, 双峰土–水特征曲线, 覆土压力效应, 固结屈服应力, 模型

Abstract：In order to investigate the stress state effect on water retention and deformation characteristics of expansive soil. Considering the overburden pressure，a soil-water characteristics curve(SWCC) model of expansive soil is carried out. Furthermore，the equation-fitting process of the proposed model under the different one-dimensional overburden pressure is analyzed. Results show that：(1) The moisture content in Nanyang expansive soil displays a regular change and bimodal characteristics wile matrix suction changes. With the increase of overburden pressure，the water-holding capacity of expansive soil decreases. The boundary effect II is significantly prolonged at 200 kPa overburden pressure. (2) The pore ratio of the soil decreases with the increase of overburden pressure and matric suction. The contribution of pore shrinkage caused by overburden pressure is 2.12 times as much as that caused by matric suction. Under the stress，the loss of void water caused by overburden pressure dominates volume shrinkage in the dehumidification process of expansive soil. (3) Based on the segmentation，the Fredlund-Xing equation is improved by using the proposed bimodal SWCC model to fit the data of Nanyang expansive soil. Fitting parameters a1 and n1 can effectively reflect the characteristic variation of SWCC1 under different overburden pressure. The influence of overburden pressure is weakened in the stage of SWCC2. The relationship between each parameter and overburden pressure is not obvious. The research gives references for the quantitative characterization of the hydraulic-mechanical coupling effect of expansive soil，as well as the study of bimodal characteristics SWCC models.

Key words： soil mechanics expansive soil bimodal soil-water characteristic curve overburden pressure effect consolidation yield stress model

引用本文:

王晓琪，许冲，汪时机，李贤. 膨胀土土水特征曲线的覆土压力效应研究[J]. 岩石力学与工程学报, 2020, 39(S1): 3067-3075.
WANG Xiaoqi，XU Chong，WANG Shiji，LI Xian. Study on overburden pressure effect of expansive soil water characteristic curve. , 2020, 39(S1): 3067-3075.

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http://rockmech.whrsm.ac.cn/CN/10.13722/j.cnki.jrme.2019.0895 或 http://rockmech.whrsm.ac.cn/CN/Y2020/V39/IS1/3067

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