三轴多级循环加卸载下红砂岩强度与变形特征试验研究  

Experimental Study on Strength and Deformation Characteristics of Red Sandstone under Triaxial Multilevel Cyclic Loading and Unloading

作　　者：宋宇宁 曾亚武[1] SONG Yuning;ZENG Yawu(School of Civil Engineering,Wuhan University,Wuhan 430072,China)

机构地区：[1]武汉大学土木建筑工程学院,湖北武汉430072

出　　处：《粉煤灰综合利用》2022年第6期7-14,共8页Fly Ash Comprehensive Utilization

基　　金：国家自然科学基金面上项目(41772308);国家自然科学基金青年项目(42107175)。

摘　　要：为研究围压及应力路径对多级循环加卸载下红砂岩的变形破坏特征的影响,采用RMT-301岩石与混凝土力学试验系统,对红砂岩在10 MPa、20 MPa、30 MPa、40 MPa围压下进行常规三轴压缩试验和等下限增幅循环加卸载试验、增下限等幅循环加卸载试验。研究结果表明:等下限增幅循环加卸载、增下限等幅循环加卸载下试件均呈脆性破坏,强度特性随围压的变化趋势基本一致,试件的加卸载变形模量总体上均随围压增大而增大;随着应力级数增加,等下限增幅循环加卸载下,加卸载变形模量呈先增加后降低或一直降低的趋势,而增下限等幅循环加卸载下均呈增加趋势;随着循环次数的增加,试件的轴向残余应变呈阶梯式增长,且在每级应力循环中呈对数型增长;每级应力的第一次循环对试件损伤影响最大,轴向残余应变显著增长,且增下限等幅循环加卸载下增长更为显著;试件在每级应力循环的轴向残余应变增量随应力级数的变化趋势不同,等下限增幅循环加卸载下呈先减小后增大的“V”形变化趋势,而增下限等幅循环加卸载下总体上呈一直增大的“ノ”形变化趋势,且围压越大变化趋势越明显。In order to study the influence of confining pressure and stress path on deformation and failure characteristics of red sandstone under multi-stage cyclic loading and unloading,RMT-301 rock and concrete mechanics test system was adopted. Conventional triaxial compression test,cyclic loading and unloading test with equal lower limit and cyclic loading and unloading test with equal lower limit were carried out on red sandstone under confining pressure of 10 MPa,20 MPa,30 MPa and 40 MPa. The results show that the specimens under cyclic loading and unloading with equal lower limit increase and amplitude increase and lower limit increase show brittle failure,and the variation trend of strength characteristics with confining pressure is basically the same. In general,the loading and unloading deformation modulus of specimens increases with the increase of confining pressure. With the increase of stress series,the deformation modulus increases first and then decreases or decreases all the time under cyclic loading and unloading with equal lower limit increasing,while it increases under cyclic loading and unloading with equal amplitude increasing and lower limit increasing. With the increase of the number of cycles,the axial residual strain increases in a stepped manner,and in each stress cycle,it increases in a logarithmic manner. The first cycle of each stress has the greatest effect on the damage of specimens,and the axial residual strain increases significantly,and the increase is more significant under cyclic loading and unloading with increasing lower limit. Specimen in the axial residual stress cycle per level of strain increment trend along with the change of stress series,such as the lower growth cycle and increase with the decrease of after unloading,first under the “V”shape trend,and increases the lower limit of loops and uninstall the overall picture is always “ノ”form change trend of increase,and the greater the confining pressure,the more obvious the change trend is.

关 键 词：红砂岩 多级循环加卸载 应力路径 变形模量 残余应变 

分 类 号：TU45[建筑科学—岩土工程]