正应力作用下北山花岗岩单裂隙几何特征对辐射流渗流行为的影响研究

Study on the influence of geometrical characteristics of single Beishan granite fracture under normal stress on seepage behaviors of radiation flow

岩体裂隙中的地下水渗流可能会导致采掘过程中围岩突水或支护失效。为研究北山花岗岩裂隙渗流行为,采用MTS815岩石力学试验系统开展了单裂隙辐射流渗流试验研究,获得了不同正应力条件下裂隙流量的变化规律,分析了裂隙几何特征对其渗流特性的影响。随后采用变异函数对裂隙空隙三维分布特征进行量化表征,建立了考虑裂隙空隙三维分布特征和接触率为影响因素的辐射流等效水力隙宽计算模型(CA模型)。研究结果表明:裂隙空隙三维分布特征可由三维分布系数(CA)表征,CA值越大,裂隙空隙的分布越不均匀;CA模型可定量表征裂隙等效水力隙宽与裂隙力学隙宽、接触率和空隙三维分布系数之间的函数关系。试验数据与模型计算结果具有较好的一致性,验证了CA模型的合理有效性。

The seepage of groundwater in rock joints may result in water-inrush from surrounding rock or failure of support during excavation.To study the seepage behaviors of Beishan granite fractures,radiation flow seepage tests on specimens with a single fracture were conducted using the MTS815 rock mechanics test system.The variations of flow quantity of the fractures under different normal stresses are obtained.The influence of geometric characteristics of fractures on seepage behaviors is analyzed.Subsequently,the 3D distribution characteristics of the fracture voids are quantitatively characterized by the variogram.The equivalent hydraulic aperture calculation model of radial flow(CA model),which considers the influence of the 3D distribution characteristics of the fractures and contact ratio,is established.The 3D distribution of fracture voids can be characterized by 3D distribution coefficient(CA).The larger the CA value is,the more uneven the distribution of fracture voids is.Meanwhile,the CA model can be used to quantitatively describe the functional relationships between the equivalent hydraulic aperture of fracture and the mechanics aperture,the convex contact ratio and the 3D distribution coefficient of the fracture.In addition,a comparison shows that the model calculation results are in good agreement with experimental data,indicating that the established CA model is reasonable and effective.