液氮溶浸对饱水煤裂隙扩展的影响研究

Study on influence of liquid nitrogen infiltration to saturated water coal fracture expanded

为研究煤体注氮增透对液氮溶浸下饱水煤裂隙的扩展规律,从王营子矿取立方体原煤煤样,真空饱和后开展液氮溶浸试验,测试了液氮溶浸前后煤样的声速、代表性裂隙面积变化率和煤样表面微观结构的变化,推导了液氮作用下饱水裂隙内水相变为冰的冻胀压力,建立了液氮溶浸下饱水煤裂隙煤扩展的力学判据。结果表明:1液氮溶浸下煤内裂隙水相变为冰,体积膨胀,引起煤内裂隙扩展,代表性裂隙面积增长,超声波速降低,裂隙密度增加。煤的微观结构也发生了很大变化。2建立的力学判据准确预测了煤样的裂隙扩展。3随着裂隙长短轴长度比值的减小,冻胀压力增加,随着水流出系数增加,冻胀力线性减小。

In order to study the expansion law of the saturated water coal fracture under the infiltration of the liquid nitrogen,the cubic raw coal samples taken from Wangyingzi Mine,after the vacuum saturation,the liquid nitrogen leaching experiment was conducted. The sound velocity of the coal sample was tested before and after the liquid nitrogen leaching and the representative crack area variation rate and coal sample surface micro structure variation were tested. Under the liquid nitrogen role,the frost swelling pressure of the ice was derived from the water phase in the saturated water cracks and the mechanics criterion of the saturated water crack expanded was established under the liquid nitrogen role. The results showed that 1 under infiltration the liquid nitrogen,the crack water in the coal transformed to ice,the volume was swelled,the cracks within the coal were expanded,the representative crack area was increased,the ultrasonic velocity was reduced and the crack density was increased. The micro structure of the coal was highly varied. 2 The mechanics criterion established could accurately predict the crack expansion of the coal sample. 3 With the length ratio of long axis and minor axis decreased,the frost swelling pressure would be increased and with the water flow coefficient increased,the linear of the frost swelling would be decreased.