单裂隙岩体水力裂缝扩展机理的数值模拟

Numerical simulation on propagation mechanism of hydraulic fracture on fractured rockmass

应用真实破裂过程分析系统软件RFPA2D2.0-Flow,采用细观方法表达岩石材料非均匀特性,建立了渗流-应力-损伤耦合模型;模拟分析了裂隙岩体在具有不同角度、不同长度、天然裂隙中点与井孔之间不同间距的单一天然裂隙条件下的水压致裂过程;通过对模型内拉伸裂缝萌生及扩展的描述,得出了天然裂隙角度、长度、天然裂隙中点与井孔的间距对裂隙岩体内水力裂纹的扩展及与天然裂隙相交模式的影响趋势。模拟分析结果表明:天然裂隙角度对模型稳定性影响较小,但对裂纹扩展模式的影响较大;天然裂隙与井孔间距的减小使模型的失稳水压值随着裂隙角度的增加而逐渐增大,但最大值与间距未减小时基本相同;随着天然裂隙长度的增加,模型的承载能力逐渐减弱,且减弱的幅度逐渐增大。

Hydraulic fracturing process in fractured rockmass which with single natural fracture at various conditions: different angles, different lengths and different distances from the wellbore is simulated by using RFPA2D(2.0)-Flow version which adopts the finite element method and considers the heterogeneous characteristics of rock in meso-scale to create seepage-stress-failure coupling model. Influential tendency of natural fracture's angle, length and distance from the wellbore on the seepage characteristics of fractured rockmass is given through the description of tensile fracture initiation and propagation in the rock specimens. Simulation results obtained show that the natural fracture angle has little effect on the stability of specimen, but has great effect on fracture propagation modes. The distance of natural fracture from wellbore affects the breakdown pressure and fracture propagation mode of specimen. With the increase of the natural fracture length, the bearing capacity of the specimen weakens gradually.