非规则软质千枚岩点荷载强度评价的等效面积法  

An equivalent area method for evaluating the point load strength of irregular soft phyllite

作　　者：朱江江[1] 罗强[1] 詹学启[2] 蒋良潍[1] 方东 ZHU Jiangjiang;LUO Qiang;ZHAN Xueqi;JIANG Liangwei;FANG Dong(School of Civil Engineering,Southwest Jiaotong University,Chengdu,Sichuan 610031,China;China Railway Siyuan Survey and Design Group Co.,Ltd.,Wuhan,Hubei 430063,China)

机构地区：[1]西南交通大学土木工程学院,四川成都610031 [2]中铁第四勘察设计院集团有限公司,湖北武汉430063

出　　处：《岩石力学与工程学报》2018年第12期2762-2771,共10页Chinese Journal of Rock Mechanics and Engineering

基　　金：中铁第四勘察设计院集团有限公司科技研究开发计划项目(2016K27–1);国家重点基础研究发展计划(973计划)项目(2013CB036204)~~

摘　　要：软质岩较难获得完整的圆柱状标准试件,点荷载试验是快速简便评价其强度的有效方法。基于点荷载强度的力学实质,分析“加载间距法”和“等效直径法”的计算模式差异,通过引入试样实际破坏截面与最小截面的宽度比“面积系数”,构建以最小截面积为基本参数的“等效面积法”及统一表达式;选用非规则软质千枚岩试样,讨论风化程度不同时面积系数的变化特征;研究形状系数和加载点间距对点荷载强度的影响规律。试验表明:面积系数呈高度偏态分布,其特征值中位数随风化程度增加在1.40~1.46范围内小幅增大,明显大于“加载间距法”的0.3~1.0,也大于“等效直径法”的4/π;据此,提出适用于非规则软质千枚岩的建议值1.43。点荷载强度sI随形状系数β和加载点间距D增大呈渐缓的减小趋势,随风化程度增加,sI受β影响的敏感性逐渐降低,D则变化不大;对于强、弱和微风化试样,点荷载强度相对偏差≤40%,所要求的形状系数不宜小于0.4,0.5和0.6,加载点间距可取35~80mm。For soft rocks,point load test is often used as an effective method to evaluate the strength quickly and easily due to that it is difficult to obtain complete cylindrical standard specimens. Based on the mechanical essence of the point load strength,the difference between the calculation models of load spacing method and equivalent diameter method was analyzed. By introducing the width ratio of the actual breaking section to the minimum section,the unified expression of the equivalent area method with taking the minimum section area as the basic parameter was constructed. The samples of irregular soft phyllite were adopted to discuss the variation characteristics of the ratio with different weathering degrees and to investigate the influence of the shape factor and the loading point space on the point strength index. Test results show that the distribution of the ratio is highly skewed,and that,with increasing the weathering degree,the characteristic value increases slightly between 1.40 and 1.46,which is not only larger than 0.3–1.0 of the“load spacing method” but also greater than 4/π of the “equivalent diameter method”. Consequently,1.43 is suggested as the characteristic value for soft phyllite. The point load strength decreases with increasing the shape factor or the loading point space. With increasing the weathering degree,the sensitivity of the influence of the shape factor on the point load strength reduces gradually. While the relative deviation of the point load strength is less than 40%,for strongly,weak and slightly weathered samples,the shape factors are not less than 0.4,0.5 and 0.6 respectively and the loading point spaces are 35–80 mm.

关 键 词：岩石力学 软质岩 点荷载试验 等效面积法 面积系数 风化程度 形状系数 尺寸效应 

分 类 号：TU45[建筑科学—岩土工程]