复杂初始应力状态下松砂多向循环单剪特性  

Multi-directional cyclic simple shear behaviour of loose sand undercomplex initial stress states

作　　者：李尧[1] 李嘉评 LI Yao;LI Jia-ping(School of Highway,Chang’an University,Xi’an,Shaanxi 710064,China;Qingdao Municipal Engineering Design Research Institute,Qingdao,Shandong 266000,China)

机构地区：[1]长安大学公路学院,陕西西安710064 [2]青岛市政工程设计研究院,山东青岛266000

出　　处：《岩土力学》2023年第9期2555-2565,共11页Rock and Soil Mechanics

基　　金：国家自然科学基金项目(No.51708040)。

摘　　要：松砂极易液化,微小的应力状态变化也会影响其液化特性。基于多向循环单剪试验,采用松砂作为试验材料,开展不同静剪应力大小、方向和复杂剪切路径下的循环单剪试验,研究复杂初始应力状态下松砂循环单剪特性,得到以下主要结论:(1)随静剪应力比增大,试样剪应力峰值增大,第1个循环内孔隙水压力增量变大,试样更易液化;初始静剪应力大小对孔隙水压力的影响在剪切初期更显著。(2)随初始静剪应力和动剪应力主轴之间夹角增大,试样在X方向的剪应力峰值减小,试样孔隙水压力加速增长,在第1个循环以及最后1个循环内孔隙水压力增量变大,循环间差值增大,试样更易发生瞬时液化。(3)8字形剪切路径试样的应力-应变滞回圈面积最大,每个循环消耗能量最多,圆形剪切路径次之,直线剪切路径最小。复杂剪切路径会在剪切开始时诱发孔隙水压力的突然增加,加大各循环中孔隙水压力的增量,试样更易液化。(4)影响松砂液化因素的排序为:初始静剪应力与动剪应力夹角、剪切路径、初始静剪应力大小。Loose sand is highly susceptible to liquefaction,and small changes in stress state can affect its liquefaction characteristics.Based on multi-directional cyclic simple shear tests,this study conducted cyclic simple shear tests on loose sand under different magnitudes and directions of static shear stress,and complex shear paths.The cyclic simple shear characteristics of loose sand under complex initial stress states are studied.The main conclusions are drawn as follows:(1)As the static shear stress ratio increases,the peak shear stress of the specimen increases,the increment of pore water pressure in the first cycle increases,and the specimen is more prone to liquefaction.The effect of the magnitude of initial static shear stress on excess pore water pressure is more significant at the early stage of shearing.(2)With the increase of the angle between the initial static shear stress and the main direction of dynamic shear stress,the peak shear stress of the specimen in the X direction decreases,and the pore water pressure of the specimen accelerates to increase.In addition,the increment in pore water pressure in the first cycle and the last cycle increases,and the difference between the cycles increases.The specimen is more prone to sudden liquefaction.(3)The specimen with 8-shaped shear path has the largest area of stress−strain hysteresis loops,which consumes the most energy per cycle,followed by the specimen with the circular shear path,and the specimen with the straight shear path has the smallest area.Complex shear paths can induce a sudden increase in pore water pressure at the beginning of shearing,increasing the increment in pore water pressure in each cycle and making it more prone to liquefaction.(4)The sequence of factors affecting the liquefaction of loose sand is the angle between the initial static shear stress and the dynamic shear stress,the shear path,and the magnitude of the initial static shear stress.

关 键 词：多向循环单剪试验 松砂 复杂初始应力 液化 孔隙水压力 应力路径 应力反转 

分 类 号：TU411[建筑科学—岩土工程]