圆孔孔壁裂缝水压扩张的压力参数理论分析

运用水压致裂法和Griffith理论,对地应力场中岩体孔壁水压诱致裂缝扩展过程进行了分析,将孔隙压力作用下孔壁裂纹的扩展过程分为3个阶段,即孔壁破裂、第二次扩展、第三次破裂扩展阶段;且不同的破裂阶段分别对应着不同的水力压力。分析了含内压裂纹的扩展压力与原始地应力场及围岩力学特性的关系,随着岩体埋深由浅至深的逐渐增加,水力致裂圆孔的孔壁破裂压力变化由2个阶段过渡为3个阶段,且存在一个钻孔位置的临界埋深。为实际坚硬顶煤水力弱化的试验设计提供了依据。

Theoretical analysis of crack expanding under pore hydraulic pressure

With the help of hydraulic fracturing method and Griffith law, the process of crack expansion due to hydraulic pressure in rock mass abject to earth stress field was analyzed in mechanics. The process of crack expansion was divided into two or three stages. They are crack occurrence of pore, second crack expanding and third crack expanding. And different fracturing stages correspond to distinct hydraulic pressure. Moreover, the relationship between fracturing pressure of crack and distribution of earth stress field was elucidated as well as mechanical characteristic of surrounding rock. The variety of fracturing pressure for crack expansion changes from two stages to three stages with the increasing of rock mass's burying depth, and a critical burying depth of drilling hole exists. Analysis of pressure in the process of crack expanding in the drilling hole of coal mass was proceeded, as a result the guideline were presented for simulating test of hydraulic fracturing in coal mass.