砂砾岩水压致裂机理及数值仿真研究

Mechanism and Numerical Simulation of Hydraulic Cracking of Sand and Gravel

为研究水力劈裂作用下的水力裂缝与砂砾石岩相互作用机理,基于统计损伤理论,利用有限元软件RFPA建立了完整不含砂砾石模型与含砂砾石有限元模型,得到了水力裂缝的扩展过程及峰值内水压变化.结果表明:不含砂砾石组出现主裂纹(出现在孔洞上下侧),裂纹路径单一,含砂砾石组裂纹与砂砾石相互作用,扩展路径曲折;砂砾石的存在极大地提高了岩体水力劈裂的内水压峰值,同时侧压的增大同样也增加了砂砾石岩的强度;对主裂纹产生机理进行了分析,同时归纳总结了水力劈裂水力裂缝与砂砾石相互作用的4种形式:偏转绕行,止裂,吸附,穿砾破坏.

In order to study the interaction mechanism between hydraulic fracture and gravel rock under hydraulic fracturing,based on the statistical damage theory,Numerical models containing gravel and without gravel were established by RFPA finite element software.Through this model,the propagation process of hydraulic fracture and the change of water pressure in the peak value are obtained.The results show that the main crack appears in the group without gravel(at the upper and lower side of the hole),the crack path is single,while the crack in the group containing gravel interacts with gravel and the propagation path is tortuous.The existence of gravel greatly increases the peak value of water pressure in hydraulic splitting of rock mass.The increase of lateral pressure also increases the strength of gravel rock.Finally,the mechanism of main crack is analyzed and four forms of interaction between hydraulic fracture and sand-gravel are summarized,i.e.deflection detour,fracture arrest,adsorption,and gravel failure.