泥炭质土在不同卸荷路径下的力学特性研究  

Mechanical Properties of Peaty Soils under Different Unloading Paths

作　　者：阮永芬[1] 潘继强 杨文辉[2] 闫明 李跃红 RUAN Yongfen;PAN Jiqiang;YANG Wenhui;YAN Ming;LI Yuehong(Faculty of Civil Engineering and Mechanics,Kunming University of Science and Technology,Kunming 650500,China;Kunming Survey Design and Research Institute Co.,Ltd.of Creec,Kunming 650200,China;China Railway 20th Bureau Group No.5 Engineering Corporation Limited,Kunming 650000,China;Kunming Junlong Geotechnical Engineering Co.,Ltd.,Kunming 650032,China)

机构地区：[1]昆明理工大学建筑工程学院,云南昆明650500 [2]中铁二院昆明勘察设计研究院有限责任公司,云南昆明650200 [3]中铁二十局集团第五工程有限公司,云南昆明650000 [4]昆明军龙岩土工程有限公司,云南昆明650032

出　　处：《昆明理工大学学报（自然科学版）》2022年第5期172-180,共9页Journal of Kunming University of Science and Technology(Natural Science)

基　　金：云南省重点研发计划项目(2018BC008).

摘　　要：对大量基坑工程实测资料分析发现,基坑周边的土体及支护结构的变形与设计值存在较大差异,特别是在饱和泥炭质土场地上差异更大,其原因在于基坑支护设计参数取值时一般都没考虑基坑开挖卸荷影响,造成了设计不合理.为研究卸荷过程中力学指标的变化,选取昆明地区广泛分布的泥炭质土,采用应力控制式三轴仪模拟基坑开挖下基坑侧壁、坑角及坑底的卸荷路径,通过侧向、轴向、轴侧向同时卸荷的固结不排水试验,对比分析其应力应变曲线、孔隙水压力和抗剪强度变化特征.试验结果表明:各应力路径下泥炭质土力学参数有明显差异.对于泥炭质土,在低围压下CU试验的强度大于K_(0)固结试验的强度,随围压增加两者强度差值减小;不同卸荷路径后土体的力学性质发生改变,且各应力路径下变化情况不一;侧向卸荷土体由于围压减小和产生剪应力的方式不同,在曲线形态、莫尔圆发展方向、孔压发展、孔隙压力系数A_(f)与加荷试验上有显著差异.通过以上研究以期进一步加深对泥炭质土基坑开挖中各部位土体力学性质的认识,通过理论分析可对工程设计及施工进行指导.Based on the analysis of a large number of measured data of foundation pit engineering,it is found that there are great differences between the deformation of soil and support structure around the foundation pit and the design value,especially on the saturated peat soil site.The reason is that the influence of foundation pit excavation and unloading is generally not considered in the value of foundation pit support design parameters,resulting in unreasonable design.In order to study the change of mechanical indexes during unloading,peat soil widely distributed in Kunming is selected,and the unloading path of the side wall,corner and bottom of the foundation pit under foundation pit excavation is simulated by stress controlled triaxial apparatus.Through the consolidated undrained test of lateral,axial and axial lateral unloading at the same time,the variation characteristics of stress-strain curve,pore water pressure and shear strength are compared and analyzed.The test results show that there are obvious differences in the mechanical parameters of peat soil under each stress path.For peat soil,the strength of Cu test is greater than that of K_(0) consolidation test under low confining pressure,and the strength difference decreases with the increase of confining pressure.The mechanical properties of soil changed after different unloading paths,and the changes were different under each stress path.Due to the reduction of confining pressure and the different ways of generating shear stress,there are significant differences among lateral unloading soil and loading test in curve shape,Mohr circle development direction,pore pressure development,and pore pressure coefficient A_(f).Through the above research,we hope to further deepen the understanding of the mechanical properties of soil in each part of peat soil foundation pit excavation,and guide the engineering design and construction through theoretical analysis.

关 键 词：基坑工程 力学特性 K_(0)固结 泥炭质土 应力-应变 

分 类 号：TU417[建筑科学—岩土工程]