摘要
为了建立干湿循环作用下裂土应变硬化损伤模型,提出裂土微元强度服从Laplace分布的假定,同时考虑初始损伤门槛影响,引入干湿循环损伤变量和荷载作用损伤变量,分别描述裂土干湿循环开裂和应力水平作用下损伤演化规律。基于不同干湿循环阶段裂土的固结不排水三轴剪切试验,探究围压对不同干湿循环开裂损伤的影响;利用线性拟合确定应变硬化损伤模型参数,探讨围压和干湿循环次数对初始损伤应力门槛值的影响,并对比验证不同干湿循环次数与应力水平作用下的试验结果。研究结果表明:干湿循环对裂土平均微元强度影响显著,5次循环后,微元平均强度降幅显著,相比初始状态降低39.7%~78.5%;反映平均微元强度与弹性模量的Laplace分布参数m0和T0均与围压呈正相关;围压提高了初始应力损伤门槛值,降低了干湿循环作用造成的损伤,相比初始状态试样,5,8和12次干湿循环后试样的初始损伤应力门槛值分别降低37.77%,45.67%和57.43%。建立的基于Laplace分布的损伤本构模型能充分反映干湿循环作用后裂土受荷时的应变硬化特征,并可模拟裂土在干湿循环和围压共同作用下的全应力-应变曲线,其模型参数易获取,且具有明确的物理意义;干湿循环次数愈多,围压愈高,模型与土体应力-应变试验曲线吻合程度越高。
In order to establish the strain hardening damage model of cracked soil during the drying-wetting cycles,the hypothesis that the strength of cracked soil obeys Laplace distribution was proposed.Considering the influence of initial damage threshold,the damage evolution law of cracked soil during drying-wetting cycles and at different stress levels was described by introducing the damage variable of drying-wetting cycles and load.Based on the triaxial consolidation undrained shear test(CU)of cracked soil during different drying-wetting cycles,the influence of confining pressure on cracking damage during drying-wetting cycles was investigated.The parameters of damage model were determined by linear fitting,the effects of confining pressure and dryingwetting cycles on the threshold value of initial damage stress were discussed,and the results were compared with those during different dry wet cycles and at different stress levels.The results show that the drying-wetting cycle has a significant effect on the average micro element strength.After five cycles,the average micro element strength decreases significantly,which is 39.7%-78.5%lower than that of the initial state.The parameters of the Laplace distribution,m0 and T0,which reflect the mean strength and elastic modulus of the microelements,are linearly and positively correlated with confining pressure.Confining pressure can improve the initial damage threshold and reduce the damage caused by the drying-wetting cycles.Compared with the initial state of samples,the initial damage stress threshold of samples after 5,8 and 12 cycles reduces by 37.77%,45.67%,and 57.43%,respectively.The damage constitutive model based on Laplace distribution can fully reflect the strain hardening characteristics of cracked soil under load after dry and wet cycles,and can simulate the stress-strain curve of cracked soil under the combined action of dry and wet cycles and confining pressures.The model parameters are easy to obtain and have clear physical significance.The more the number of
作者
周峙
张家铭
宁伏龙
罗易
ZHOU Zhi;ZHANG Jiaming;NING Fulong;LUO Yi(School of Engineering,China University of Geosciences,Wuhan 430074,China;Key Laboratory of Geological Survey and Evaluation of Ministry of Education,Wuhan 430074,China)
出处
《中南大学学报（自然科学版）》
EI
CAS
CSCD
北大核心
2020年第12期3484-3492,共9页
Journal of Central South University:Science and Technology
基金
地质探测与评估教育部重点实验室主任基金和中央高校基本科研业务费(GLAB2019 ZR05)
国家自然科学基金资助项目(41372311)
安徽省交通运输厅科技进步计划项目(2018030)。
关键词
裂土
干湿循环
LAPLACE分布
应变硬化
统计损伤模型
cracked soil
wet-dry circulation
Laplace distribution
strain hardening
statistical damage model
