摘要
参照应力控制式三轴仪的作用原理,对应变控制式三轴仪进行了改造,使用改造后的仪器研究了侧向卸荷条件下原状黄土的变形特性及各项土力学参数的变化规律,并与常规三轴压缩试验进行了对比,结果表明:(1)试样在卸荷初期呈现明显的弹性变形,弹塑性变形范围较小,后期呈现明显的塑性变形,且破坏较为迅速;(2)试样的各项土力学参数与常规三轴压缩试验明显不同,包括内聚力c偏小、内摩擦角φ偏大、初始模量Ei偏大等;(3)试样发生破坏时破坏比Rfu≈1,说明已达到承载力极限状态;(4)试样的剪切带呈现出由一条向多条发展的趋势,且出现应变软化现象,造成强度迅速衰减。在基坑工程的设计阶段,应尽量选取与土体的应力路径相符合的试验参数,以使施工方案更为合理。
The author reformed the triaxial apparatus of strain control apparatus by reference to the theory of the triaxial apparatus of stress control.The paper performed lateral unloading test using the modified strain controlled triaxial apparatus,researched deformation characteristics of undisturbed loess samples and tendencies of mechanical parameters under lateral unloading condition,and analyzed differences with conventional triaxial compression test.The results show:(1)In the lateral unloading condition,samples appeared obvious elastic deformation in the early stage and the scale of elastic-plastic deformations was small.In the late stage,samples showed distinctive plastic deformations and had high damage speed.(2)Compared with conventional triaxial compression test,this test has significant different test parameters and tendency,which are mainly characterized by smaller cohesion,larger internal friction angle and larger initial modulus.(3)When damages happened,samples damage ratio approached 1,which has reached ultimate capacity limit states.(4)When damages happened,shear zones of samples developed from one to many along with strain softening.As a result,intensity decreased fast.In the design of foundation pit,we should analyze the stress path and stress state of soil,and use the test parameters which accords with actual engineering so that the construction scheme will be more appropriate.
作者
李宝平
郭兴峰
张玉
王智
刘鹏
LI Bao-ping;GUO Xing-feng;ZHANG Yu;WANG Zhi;LIU Peng(School of Civil and Architecture Engineering,Xi’an Technological University,Xi’an 710021,China)
出处
《土木工程与管理学报》
北大核心
2018年第6期87-93,100,共8页
Journal of Civil Engineering and Management
关键词
基坑开挖
应力路径
侧向卸荷
变形特性
excavations of foundation pit
stress path
lateral unloading
deformation characteristics
