卸荷条件下结构性软黏土三维力学特性研究  

Study on the Three-Dimensional Mechanical Properties of Structural Soft Clay Soils under Unloading Conditions

作　　者：杨爱武 黄俊枭 李建华 Yang Aiwu;Huang Junxiao;Li Jianhua(College of Environmental Science and Engineering,Donghua University,Shanghai 201620,P.R.China;College of Civil Engineering,Tianjin Chengjian University,Tianjin 300384,P.R.China)

机构地区：[1]东华大学环境科学与工程学院,上海201620 [2]天津城建大学天津市软土特性与工程环境重点试验室,天津300384

出　　处：《地下空间与工程学报》2024年第3期812-826,共15页Chinese Journal of Underground Space and Engineering

基　　金：国家自然科学基金(42177119,51978440);中央高校基本科研业务费专项资金(2232021A-07)。

摘　　要：软黏土一般具有结构性,结构性是土体变形特性的重要影响因素。以天津滨海软黏土为原料土,通过掺入少量不同含量的水泥人工制备出土质近似均匀、结构性有所不同的结构性软黏土,采用GCTS真三轴试验仪探讨基坑开挖条件下结构性土体的三维力学特性。结果表明:侧向卸荷条件下土体应变与卸荷速率、土体本身结构性、固结围压皆有关系;当土体结构性与卸荷速率相同时,围压越小的试样应变增长的速率越快,破坏时应变量越大;在土体结构性与围压相同时,随着卸荷速率的增大,破坏应变以及破坏时的应力大小都增大;当大主应变ε1小于破坏应变,土样的结构性未发生破坏时,ε1-ε3关系曲线斜率增长速率较慢,当大主应变ε1达到破坏峰值后,小主应变ε3方向膨胀速率加快,直至试样破坏;在同一围压下,土体初始卸荷切线模量随卸荷速率的增大而减小,土体卸荷破坏强度随卸荷速率的增大而增大。在此基础上,对应力-应变关系进行分析,建立并验证了考虑卸荷速率和土样结构强度影响的卸荷破坏强度预测公式。Soft clay soils are generally structural in nature,and structural properties are an important factor influencing soil deformation characteristics.The soft clay soil of Tianjin Binhai was used as the raw material,and the structural soft clay soil was artificially prepared by mixing a small amount of cement with different contents to produce a nearly homogeneous soil with different structural properties.The test results show that the strain of the soil under lateral unloading conditions is related to the unloading rate,the structure of the soil itself and the consolidation envelope pressure.When the structural properties of the soil and the unloading rate are the same,the smaller the envelope pressure,the faster the strain growth rate of the specimen and the greater the strain during damage.When the structure of the soil is the same as the surrounding pressure,the strain at failure and the stress at failure both increase as the unloading rate increases.When the large principal strainε1 is less than the damage strain and the structural properties of the soil sample are not damaged,the slope of theε1-ε3 relationship curve grows at a slower rate,and when the large principal strainε1 reaches its peak damage,the expansion rate in the direction of the small principal strainε3 accelerates until the sample is damaged.Under the same circumferential pressure,the initial unloading tangential modulus of the soil decreases with increasing unloading rate,and the unloading damage strength of the soil increases with increasing unloading rate.On this basis,the stress-strain relationship was analysed and a prediction formula for the unloading damage strength was established and validated,taking into account the effects of unloading rate and structural strength of the soil sample.

关 键 词：结构性土 卸荷速率 初始卸荷模量 卸荷破坏强度 真三轴试验 

分 类 号：TU411[建筑科学—岩土工程]