灰岩三轴压缩力学特性试验及三维离散元模拟

Experimental and 3D DEM Simulation on the Triaxial Compression Mechanical Behavior of Limestone

开展岩石常规三轴力学特性及细观损伤机理研究,对于维护地下工程围岩的稳定具有重要意义。为此针对徐州地铁工程所涉及的灰岩,开展了不同围压作用下常规三轴试验及PFC^(3D)数值模拟研究,分析了灰岩的力学特性、微裂纹和能量随围压演化特征。研究结果表明:围压对灰岩的力学特性及能量演化有较大影响;试样峰值强度、残余强度随围压呈线性增加,弹性模量、变形模量与围压呈正相关;随着围压增加,试样破坏模式由张拉破坏转为剪切破坏,峰后呈现延性趋势;各类裂纹数目均逐渐增加,试样逐渐由拉伸裂纹主导的破坏向剪切裂纹主导的破坏转变;在能量演化方面,加载前期荷载做功几乎完全转化为应变能,在峰值应力附近达到峰值,在峰后阶段得到缓慢释放。

The study of the conventional triaxial mechanical properties of rocks and the mechanism of finescale damage is of great significance for maintaining the stability of the surrounding rocks of underground projects.For this reason,conventional triaxial tests and PFC^(3D) numerical simulations were carried out on the limestone rock masses involved in the Xuzhou Metro project under different confining pressures.The mechanical properties,microcracks and energy evolution characteristics of the limestone with confining pressure were analyzed by numerical simulation.The research results show that:The confining pressure has a significant influence on the mechanical properties and energy evolution of the specimens.The peak strength and residual strength of the specimens increase linearly with the confining pressure,and the elastic modulus and deformation modulus are positively correlated with the confining pressure.As the confining pressure increases,the failure mode of the specimen changes from tensile damage to shear damage,with a ductile trend after the peak;the total number of tensile cracks,shear cracks and cracks also gradually increases,the specimen gradually changes from tensile crack-led damage to shear crack-led damage.During the pre-loading phase,the external load work is almost completely converted into strain energy stored in the specimen,which peaks near the peak stress and is slowly released in the post-peak phase.