裂隙岩体渗流-断裂耦合机制及应用

Coupling mechanism of seepage-fracture in fractured rock mass and its application

将断裂力学引入裂隙岩体流固耦合分析,建立裂隙岩体渗流-断裂耦合机制,在FLAC3D现有计算模块的基础上,通过FISH研制了裂隙岩体渗流-断裂耦合分析程序。该模型的耦合机制体现在:渗透水力梯度作为渗透体积力作用于应力计算单元,裂隙渗透压作为面力作用于裂纹张开部分引起断续岩体裂纹的劈裂扩展;岩体裂纹的扩展引起岩体渗透系数的增加导致渗流场的改变。将渗流-断裂耦合理论应用于高水头不衬砌压力隧洞工程中,系统地研究高水头不衬砌压力隧洞在运行期间的水力劈裂、渗流场和内水外渗渗漏情况,得到:①处于水力劈裂的高水头压力隧洞周边向外延伸依次为拉剪劈裂区、压剪劈裂区、未劈裂区;②由于渗流体积力作用,高水头压力隧洞内水外渗过程中洞周产生径向向外变形;③高水头压力隧洞内水外渗过程中渗漏率先增加后平稳减少最终稳定。首次提出陡倾地表下不衬砌压力隧洞与裂纹几何特性、力学特性和岩石断裂韧度高度相关的水力劈裂系数的概念。建议在水工隧洞设计规范中建立与水力劈裂系数相匹配的安全控制标准,可为我国不衬砌压力隧洞工程的设计提供理论基础。

By introducing the fracture mechanics into fluid-solid coupling analysis, the mechanism of seepage-fracture coupling is established. Baesd on the existing computation modules of FLAC3D, the programs of seepage-fracture coupling in fractured rock mass are developed by use of the FISH language. The coupling mechanism of the model lies in that the hydraulic gradient acts on the stress units as seepage volume strength, the seepage pressure acts on the opening part of cracks as surface force and induces fracture and growth of discontinuous cracks, and the crack growth leads to the increase of permeability coefficient and ultimately to the change of seepage field. The theory of seepage-fracture coupling is applied to unlined pressure tunnels. The laws of hydraulic fracture, distribution of seepage field and leakage ratio of the inner are studied. The results are obtained as follows： （1） from the tunnel border, the rock around the unlined pressure tunnels stretches outwards and three zones are formed, that is, tensile-shear splitting zone, compressive-shear splitting zone and no disturbance zone; （2） radial displacement occurs at the tunnel border during the leakage of imler water; （3） the leakage ratio first increases, then decreases and finally keeps steady. The hydraulic splitting factor of pressure tunnels under inclined ground is proposed and closely correlated with the geometric and mechanical characteristics of cracks and fracture toughness of the rock. For the design standards of hydraulic tunnels, it is suggested to establish the safety control standards matched with the hydraulic splitting factor. The mechanism of seepage-fracture coupling provides a theoretical basis for the design of unlined pressure tunnels in China.