冻融循环单轴压缩下不等长交叉裂隙砂岩变形破坏特征研究

Study on Deformation and Failure Characteristics of Sandstone with Unequal Length Cross Cracks under Uniaxial Compression of Freeze-Thaw Cycle

为了探究冻融-荷载作用下含交叉裂隙砂岩力学特性及破坏机制,本文对不同冻融次数下交叉裂隙试样开展了单轴压缩试验,分析了冻融循环下交叉裂隙试样的物理性质劣化规律以及宏观力学特性,并基于PFC2D离散元软件采用水颗粒膨胀法对冻融循环全过程进行模拟,结合数值模拟与试验结果,进一步探究了冻融作用下试样的宏细观损伤机理.结果表明:冻融循环作用会使岩石的物理力学性质发生劣化,降低岩石的储能能力,与未冻融试样相比,冻融90次试样峰值强度、弹性模量、总能分别下降了32.1%、29.3%、56.77%;随着冻融循环次数的增加,试样的破坏模式由单纯剪切破坏逐步向张拉-剪切破坏过渡;试样均于主裂隙尖端处起裂,但扩展方向不同,未冻融试样沿着主裂隙45°方向扩展,而冻融后试样沿裂隙两端垂直扩展.

In order to explore the mechanical properties and failure mechanism of sandstone with crossfissures under freeze-thaw-load,this paper carried out uniaxial compression tests on cross-fissure samples under different freeze-thaw times,and analyzed the physical properties and macroscopic mechanical properties of cross-fissure samples under freeze-thaw cycles.Based on PFC2D discrete element software,the whole process of freeze-thaw cycles was simulated by water particle expansion method.Combined with numerical simulation and experimental results,the macro-meso damage mechanism of samples under freeze-thaw action was further explored.The results show that the freeze-thaw cycle will deteriorate the physical and mechanical properties of the rock and reduce the energy storage capacity of the rock.Compared with the non-freeze-thaw samples,the peak strength,elastic modulus and total energy of the freeze-thaw 90 samples decreased by 32.1%,29.3%and 56.77%,respectively.With the increase of freeze-thaw cycles,the failure mode of the specimen gradually transits from simple shear failure to tensile-shear failure.The samples all crack at the tip of the main crack,but the expansion direction is different.The unfreeze-thawed samples expand along the 45°direction of the main crack,while the freeze-thawed samples expand vertically along both ends of the crack.