复杂应力路径下海相结构性软土力学特征试验  

Mechanical characteristic test of structural marine soft clay under complex stress paths

作　　者：王智超[1,2] 王炜超 彭慧良 哈吉章 WANG Zhichao;WANG Weichao;PENG Huiliang;HA Jizhang(Hunan Key Laboratory of Geomechanics and Engineering Safety,Xiangtan University,Xiangtan 411100,China;School of Civil Engineering,Xiangtan University,Xiangtan 411100,China;China Construction Fifth Engineering Division Corp.,Ltd.,Changsha 410000,China)

机构地区：[1]湘潭大学岩土力学与工程安全湖南重点实验室,湖南湘潭411100 [2]湘潭大学土木工程学院,湖南湘潭411100 [3]中国建筑第五工程局有限公司,湖南长沙410000

出　　处：《铁道科学与工程学报》2023年第8期2868-2877,共10页Journal of Railway Science and Engineering

基　　金：湖南省教育厅优秀青年项目(17B260);湖湘高层次人才聚集工程-创新团队(2019RS1059);国家自然科学基金资助项目(51308485)。

摘　　要：为揭示结构性软土层基坑开挖以及盾构施工过程中周围土体面临的复杂应力路径状态,设计不同应力路径三轴试验以探究结构性软土在开挖和卸载过程中的强度以及变形特征。选用大阪湾天然结构性软土为参照目标,人工制备海相高液限、大孔隙以及相似结构性变形特征的软土,克服了天然结构性原状软土取样困难以及试样性状离散性大等问题,并对批量制备的结构性软土试样开展CTC(CTE),RTC(RTE)和PTC(PTE)6种不同应力路径下的三轴剪切试验,深入分析基坑开挖以及盾构施工2类典型施工路径对结构性软土力学性能的影响。研究结果表明:1)结构性软土在不同应力路径下的力学特性差异显著,且应力应变曲线都存在软化现象,RTC(RTE),CTC(CTE)和PTC(PTE)的峰值强度依次增大,三轴拉伸仅为压缩强度的60%~70%;2)基坑被动区卸载路径下变形和强度显著降低,盾构同步注浆施工路径下峰值强度较高但存在脆性破坏风险;3)结构性软土归一化模量的变化体现了土体渐进破坏过程,且不同应力路径下的归一化模量与固结围压相关;4)不同路径对土体黏聚力变化明显,开挖卸载路径下土体抗剪强度降低了80%,说明不同应力路径对结构性软土的强度和变形特征都存在明显劣化作用。研究结果对软土地基中以变形控制为主的基坑开挖和盾构施工具有较好的指导意义。In order to reveal the complex stress path state of surrounding soil during foundation pit excavation and shield construction of structural soft soil,triaxial tests with different stress paths were designed to explore the strength and deformation characteristics of structural soft soil during excavation and unloading.The natural structured soft clay of Osaka Bay was selected as the reference target,and the Marine soft soil with high liquid limit,large porosity,and similar structural deformation characteristics were manually prepared,which overcame the sampling difficulties of natural structural undisturbed soft soil and the large discreteness of sample properties.Triaxial shear tests under six different stress paths including CTC(CTE),RTC(RTE)and PTC(PTE)were carried out on the batch prepared structural soft soil samples,and the effects of two typical construction paths including foundation pit excavation and shield construction on the mechanical properties of structural soft soil were analyzed.The results show that:1)the mechanical properties of structural soft soil exhibit significant differences under different stress paths,and the stress-strain curves all have softening phenomenon.The peak strength of RTC(RTE),CTC(CTE)and PTC(PTE)increase successively,and the triaxial tensile strength is only 60%~70%of the compressive strength.2)The deformation and strength of the passive area of the foundation pit are significantly reduced under the unloading path,and the peak strength of the shield synchronous grouting construction path is higher but there is a risk of brittle failure;3)The change of normalized modulus of structural soft soil reflects the progressive failure process of soil,and the normalized modulus under different stress paths is related to consolidation confining pressure.4)The cohesion of the soil varies significantly with different paths,and the shear strength of the soil decreases by 80%under the excavation and unloading path,indicating that the strength and deformation characteristics of the structur

关 键 词：结构性 应力路径 变形特征 割线模量 抗剪强度指标 

分 类 号：TU411[建筑科学—岩土工程]