论文部分内容阅读
为了研究煤层固液耦合和渗透水压力(水力梯度)作用下的结构改造及渗透性演变规律,在MTS 815.02电液伺服岩石力学试验系统上采用瞬态压力脉冲法进行了煤体全应力应变过程中的渗透性测试。试验结果表明,煤体的渗透性与其内部结构密切相关,在全应力应变过程,煤体渗透性的演变与其内部裂隙的变化趋势一致。在应变软化至峰值强度的24.98%时,煤体渗透性达15.69×10-13cm/s,分别是弹性阶段和峰值时的79.30倍和16.34倍。在固液耦合不产生损伤的条件下,瞬态渗透系数整体与水力梯度成正比关系。渗透水压力可引起结构面的错动闭合或导致破裂碎屑集聚堵塞渗流通道。当煤样变形进入到弹塑性阶段以后,瞬态渗透系数随时间延长先整体降低,降低到一定值时突然急剧增大至一定峰值,然后再逐渐降低并趋于稳定。且煤样由弹塑性经塑性至破坏(残余强度)阶段,中间突变的峰值与初始瞬态渗透系数的差值越来越小,出现中间突变峰值所需时间越来越长。采用瞬态压力脉冲法测量评价岩石的渗透性时,应采用上下水压差第一次趋于稳定时的数据来计算其渗透系数。
In order to study the structural transformation and permeability evolution under the effect of solid-liquid coupling and infiltration hydraulic pressure (hydraulic gradient) in coal seam, the whole-stress-strain process of coal was carried out by transient pressure pulse method on MTS 815.02 electro-hydraulic servo rock mechanics test system In the permeability test. The experimental results show that the permeability of coal is closely related to its internal structure. During the process of total stress and strain, the permeability of coal is consistent with the change of its internal fissures. When the strain is softened to 24.98% of the peak strength, the permeability of coal reaches 15.69 × 10-13cm / s, which is 79.30 times and 16.34 times of the elastic phase and peak respectively. Under the condition that solid-liquid coupling does not produce damage, the transient permeability coefficient is directly proportional to the hydraulic gradient. Permeate pressure can cause the structural surface to close or cause the buildup of seepage channels by the bursting debris. When the deformation of coal sample enters into the elasto-plastic phase, the transient permeability coefficient decreases overall with the increase of time. When it decreases to a certain value, it suddenly increases sharply to a certain peak value, and then gradually decreases and tends to be stable. In addition, the difference between the peak value of the intermediate abrupt change and the initial transient permeability coefficient is getting smaller and smaller, and the time required for the peak of the intermediate abrupt change takes longer and longer. When using the transient pressure pulse method to measure and evaluate the permeability of rock, the permeability coefficient should be calculated by the data when the pressure difference between upper and lower water reaches the first stable condition.