土工平面应变仪压力室的改进  

Improvements of loading chamber of plane-strain apparatus

作　　者：邵龙潭[1,2] 阎崇超 曾飞涛 

机构地区：[1]大连理工大学工程力学系,辽宁大连116085 [2]大连理工大学工业装备结构分析国家重点实验室,辽宁大连116085

出　　处：《岩土力学》2017年第5期1251-1257,1266,共8页Rock and Soil Mechanics

基　　金：国家自然科学基金项目(No.51309047)~~

摘　　要：现有的平面应变试验仪都不能很好地解决接触摩擦的问题,试验中土样与约束面板之间存在较大的摩擦力影响变形测量的准确性。在总结平面应变仪发展历程的基础上,根据加载方式将平面应变仪分为4类,分析了现有的平面应变试验仪的特点和存在的问题;介绍了一种改进的平面应变仪的压力室。改进后的压力室在前、后约束面板与土样之间分别增设一层厚约3 mm的密封水膜。在试验过程中,包裹土样的橡皮膜与密封水膜的硅胶膜紧密贴合而不直接与面板贴合,可以消除土样与面板之间的摩擦。同时,新型的压力室还可应用于土样变形数字图像测量系统,实时测量土样表面的变形分布,可以比较精确地测量土样的表面变形、剪切带的形成过程及特征。分别使用改进的压力室和未改进的压力室对福建标准砂进行平面应变试验,前者测得的应力-应变关系曲线的峰值比后者低约60%。制备相同干密度的土样分别进行不同围压条件下的三轴试验和平面应变试验测取土样的抗剪强度,使用改进压力室得到的抗剪强度参数与三轴试验测得的结果很接近,而使用未改进的压力室测得结果则明显不合理。The existing plane-strain apparatuses can not avoid the friction between the soil specimen and the constraint panel, which influences greatly the accuracy of soil deformation measurement. This paper presents a brief review of the plane-strain apparatuses. The plane-strain apparatuses are classified into four types according to their loading models. The advantages and disadvantages are discussed for each type of the plane-strain apparatus. A newly developed plane-strain apparatus with modified loading chamber uses the special designed front and rear panels with 3 mm water film to reduce the friction. Friction between soil sample and panel can be eliminated during the test, since the rubber film touches the water-sealing silicone membrane instead of touching the panel. A digital image measurement system is integrated into the apparatus to measure the deformation distribution on soil specimen surface with high accuracy and capability of identifying shear band and its characteristics. The improved and conventional chambers are employed to measure the deformation of Fujian standard sand, respectively. The peak values of the stress-strain curves obtained by the new plane-strain apparatus can be reduced by 60%. Both triaxial and plain-strain tests on the soil specimen with same dry density under different confining pressures measure the soil＇s shear strength. It is shown that the shear parameters obtained by using the new type of loading chamber are closed to that of the triaxial test. However, the results by using the old one are obviously unreasonable.

关 键 词：平面应变仪 新型压力室 土样与面板的摩擦 数字图像测量 

分 类 号：TU415[建筑科学—岩土工程]