Influence of lateral pressure on mechanical behavior of different rock types under biaxial compression

Abstract

Lots of field investigations have proven that layer-crack structure usually appears during the excavation process of deep rock or coal mass. To provide experimental data for studying the formation mechanism of layer-crack structure, this study researches the influence of lateral pressure on the mechanical behavior of different rock types. Four rock types have been tested and the formation mechanism of macro-fracture surface is analyzed. Results indicate that the brittleness and burst proneness of rock or coal material are stronger than that of gypsum material due to the different mineral compositions and structures. When the lateral pressure is less than 10% uniaxial strength, the peak stress and elastic modulus increase with the increase of lateral pressure; but when the lateral pressure is larger than 10% uniaxial strength, the two parameters decrease slightly or keep steady. This is because when the lateral pressure reaches a certain value, local failure will be formed during the process of applying lateral pressure. Under the condition of low lateral pressure, the failure of the specimen is dominated by the tensile mechanism; under the condition of relatively high lateral pressure, the area of the specimen close to the free surface is tensile splitting failure, and the area far from the free surface is shear failure.

摘要

大量现场案例证明，层裂结构通常出现在深部煤岩体的开挖过程中。为对探讨层裂结构形成机 制提供实验数据，本论文通过测试分析四种类型岩石宏观破裂面的形成机制，研究了侧向压力对不同 类型岩石力学行为的影响机制。结果表明，由于矿物成分和内部结构不同，岩石或煤的脆性和冲击倾 向性均**于石膏。当侧压低于单轴**度的10%时，峰值应力和弹性模量随着侧压的增加而升高；当侧 向压力高于单轴**度的10%时，峰值应力和弹性模量随着侧压的增加略有下降或保持不变。分析其原 因为当侧压达到临界值时，继续施加侧压时会导致岩石局部失效。低侧压条件下，试样破坏主要受拉 伸机制控制；较高侧压条件下，试样邻**自由面区域发生拉伸劈裂破坏，远离自由面区域发生剪切 破坏。