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为研究复合坚硬顶板的水压裂缝扩展过程,建立相应扩展模型,对水压裂缝的扩展机制和扩展模式进行理论分析,以大同矿区复合坚硬顶板为研究对象,采用岩石损伤破裂过程渗流-应力耦合分析系统(RFPA~(2D)-Flow)数值模拟软件,研究水压裂缝的扩展过程及不同因素下的影响,并用相似模型试验方法验证数值模拟结果。结果表明,水压裂缝的扩展主要受到顶板岩石的力学性质、主应力差、层理面倾角和层理面力学性质等因素的影响。大同矿区的复合坚硬顶板中的水压裂缝优先扩展进入强度最低的泥岩层,随主应力差增大,水压裂缝向不同岩性岩层扩展过程的差异性减弱。随着层理面倾角增大,水压裂缝由穿过粗粒砂岩层扩展逐渐转为沿层理面和限制在压裂层内扩展。而层理面弹性模量的增大,有利于水压裂缝直接扩展进入粗粒砂岩层。
In order to study the hydraulic fracture propagation process of composite hard roof, a corresponding extension model is established, and the expansion mechanism and extension mode of hydraulic fractures are theoretically analyzed. Taking the composite rigid roof in Datong mine as the research object, the seepage-stress coupling Analysis system (RFPA ~ (2D) -Flow) numerical simulation software to study the expansion process of hydraulic fractures and the impact of different factors, and verify the numerical simulation results with similar model tests. The results show that the expansion of hydraulic fractures is mainly affected by the mechanical properties of the roof rock, the main stress difference, bedding plane angle and mechanical properties of bedding plane and other factors. The hydraulic fractures in the composite rigid roof of Datong Mining Area preferentially expand into the mudstone with the lowest strength. With the increase of the principal stress, the difference in the expansion process of the hydraulic fractures to different lithologies is weakened. As the bedding plane inclination increases, the hydraulic fractures gradually expand from coarse sandstone to fine bedding along the bedding planes and confine them to expand in the fracturing layer. The elastic modulus of the bedding surface increases, which is conducive to the direct expansion of hydraulic fractures into coarse sandstone.