不同瓦斯压力下煤岩三点弯曲断裂特性研究

Investigation on fracture mechanism of coal rock on three-point bending tests under different gas pressures

为探求含瓦斯煤I型裂纹断裂韧度及断裂过程裂纹扩展特性,以原煤制作中心直裂纹半圆盘三点弯曲试样为研究对象,利用自行研制的带视窗的含瓦斯煤岩试验装置,开展了不同瓦斯压力条件下含瓦斯煤I型裂纹断裂特性研究。研究结果表明:在瓦斯赋存状态下,随瓦斯压力的增大,I型断裂韧度及断裂能耗呈逐渐降低的趋势;含瓦斯煤试样扰度逐渐增大,试样在破坏前塑性形变逐渐明显;裂纹初始扩展速度显著增加(瓦斯压力由0增加至1.5 MPa时,其初始扩展速度由78 m/s提高至239 m/s),且随裂纹长度的增加,扩展速度明显降低;通过数字散斑方法,清晰的描述试样表面变形及裂纹扩展过程,并得到裂纹扩展前的损伤区域。

To investigate the opening-mode（mode-I） fracture toughness and the crack propagation characteristic ofcoal containing gas,semi-circular bend coal specimens with central straight cracks were tested with the self-developedvisible gas-solid coupling test equipment under different molding pressures. The results show that mode-I fracturetoughness and rupture energy decrease of coal area obviously influenced by gas. The fracture toughness and the ruptureenergy decrease with the increase in gas pressure,but the deflection and plastic deformation of coal increases with theincrease in gas pressure. Crack propagation velocity becomes faster as gas pressure increases. When gas pressure in-creases from 0 to 1. 5 MPa,the crack velocity increases form 78 m/ s to 239 m/ s,and when cracks are gradually propa-gating,the crack velocity sharply decreases. On the basis of the digital speckle correlation method,the full deformationfield of gas-containing coal at the mesoscopic scale has been successfully measured,and the whole failure process anddamage evolution of the coal containing gas is revealed by the lateral displacement and strain of coal specimens.