三种不同粒径砂岩的强度与破坏特征

为研究三种不同粒径砂岩在受载条件下的强度变化和破坏特征，选取同一地区的三种不同粒径的砂岩，分别进行了单轴压缩和巴西劈裂试验，借助基恩士超景深显微系统观察三种砂岩在受压、受拉破坏后裂隙周围岩石结构。试验结果表明：（1）砂岩随着粒径减小，颗粒比表面积增大，胶结及结构排列越密实，抗压（抗拉）强度越高，破坏形式由延展性逐渐转为脆性；（2）砂岩抗压强度随着粒径增大而降低，细砂岩较粉砂岩抗压强度降低了24.1%，粗砂岩较粉砂岩抗压强度降低了49.4%；（3）砂岩抗拉强度随着粒径增大而减小，细砂岩较粉砂岩抗拉强度降低了33.2%，粗砂岩较粉砂岩抗拉强度降低了52.3%；（4）砂岩抗压、抗拉强度随着粒径增加分别呈指数、幂函数减小的演化规律和变化特征。

The Strength and Failue Characstics of Three Kinds Of Sandstone With Different Particle Size

Abstract: In order to study the strength change and failure characteristics of sandstones with three different particle sizes under loading conditions, uniaxial compression and Brazilian splitting tests were conducted on sandstones with three different particle sizes. With the help of Keyence ultra-depth of field microscopy system, observe the rock structure around the fissures of the three sandstones after compression and tension failure . The experimental results show that:(1)With the decrease of particle size, the specific surface area of sandstone particles increases, the cementation and structural arrangement are more dense, the compressive ( tensile ) strength is higher, and the failure mode gradually changes from ductility to brittleness;(2) The compressive strength of sandstone decreases with the increase of particle size. The compressive strength of fine sandstone is 24.1 % lower than that of siltstone, and the compressive strength of coarse sandstone is 49.4 % lower than that of siltstone;(3) The tensile strength of sandstone decreases with the increase of particle size. The tensile strength of fine sandstone is 33.2 % lower than that of siltstone, and the tensile strength of coarse sandstone is 52.3 % lower than that of siltstone.(4) With the increase of particle size, the compressive and tensile strength of sandstone show the evolution law and variation characteristics of exponential and power function decrease, respectively.