层理对煤岩动态断裂及能量耗散规律影响的试验研究

Effects of bedding on fracture characteristics and energy dissipation of coal under impact loading

为研究动态荷载条件下加载率及层理倾角对煤样断裂韧度及能量耗散特征的影响,采用直切槽半圆弯拉法和霍普金森加载装置对煤样开展动态断裂韧性测试。分析不同层理倾角煤样动态断裂韧度的率响应特征;并通过对比不同冲击速度和层理倾角煤样的入射能、吸收能、断裂能和残余动能,得出冲击荷载下不同层理倾角煤样动态断裂过程的能量耗散规律。研究表明:冲击荷载下直切槽半圆弯拉煤样以拉伸破坏为主,且裂纹贯穿后的2个碎片均为匀速转动;煤样动态断裂韧度为准静态断裂韧度的3.52~8.64倍,动态断裂韧度随冲击速度的增大而不断增加,但煤样中层理倾角对动态断裂韧度的影响随冲击速度的增加逐渐减弱;煤样动态断裂能随冲击速度的增大而不断增加,但断裂过程能量耗散率随冲击速度的增大而不断减小。

In order to study the influence of bedding angle and loading rate on the fracture toughness and energy dissipation of coal,notched semi-circular bending（NSCB） specimens were tested by using a split Hopkinson pressure bar（SHPB） system.The dynamic fracture toughness of coal specimens with various bedding angles under different loading rates were analyzed and discussed.By comparing the incident energy,absorbed energy,fracture energy and residual kinetic energy of coal samples with different bedding angles under various impact velocities,the energy dissipation law of the dynamic fracture process of coal considering the bedding direction effect is obtained.The experimental results indicate that the fracture pattern of NSCB coal samples is tensile failure and the two pieces of the broken coal sample rotate at a constant speed.The dynamic fracture toughness of coal sample is 3.52–8.64 times of the quasi-static fracture toughness.The dynamic fracture toughness increases with the increase of impact velocity,but the effect of bedding angle on dynamic fracture toughness decreases with the increase of impact velocity.The dynamic fracture energy of coal samples increases with the increase of impact velocity,but the energy utilization ratio decreases with the increase of impact velocity.