岩体粗糙裂隙网络渗流分析的子单元法

岩体粗糙裂隙的细部特征对区域整体渗流分析影响很大,以往渗流分析往往没有考虑粗糙裂隙细部特征以及其对整体渗流分析的影响。提出子单元法来分析岩体粗糙裂隙网络渗流,则可以较好的分析上述影响。子单元法将每一裂隙当成一个单元,裂隙内部则分成若干子单元,裂隙单元的总体水力特征受所有的子单元联合作用控制,而细部水力特征由单一子单元体现。根据单裂隙开度分布统计规律模拟裂隙开度分布,将单裂隙等长分段(子单元),根据模拟开度参数求得裂隙中任一子单元的平均隙宽,进一步推导裂隙的单宽流量公式和子单元结点的水头公式。利用岩体裂隙网络渗流理论,结合粗糙单裂隙等宽流量公式,求得各裂隙结点水头,进一步求得裂隙的单宽流量,进而求得裂隙子单元水头和流速。通过分析可得粗糙裂隙网络渗流与平滑裂隙网络存在明显不同:(1)裂隙网络中任一裂隙单宽流量计算公式不同,粗糙裂隙的等效水力隙宽小于平均隙宽;(2)裂隙内水头分布形式不同,光滑裂隙呈直线状分布,而粗糙裂隙呈阶梯状分布;(3)组成裂隙网络渗流传导矩阵的计算公式不同,粗糙裂隙网络考虑了裂隙细部水力特征对渗流的影响;(4)粗糙裂隙子单元法考虑了裂隙开度分布不均匀对裂隙过流能力的影响,更加合理。本研究可为实际工程提供参考。

The sub-element method on the analysis for the seepage in the coarse fractures network of rock mass

The detail characteristics of coarse fractures has great effect on the seepage analysis of the whole study area, but in the past time, the detail characteristics of coarse fractures and its influence to seepage analysis used to be not taken into consideration. For the convenience of the seepage analysis on coarse fractures network of rock mass, the sub-element methods was proposed. In this method, each fracture is an element, and is divided in to several sub-elements. The hydraulic characteristics of fractures are controlled by the union effects of all the sub-elements in it, while its detail hydraulic characteristics can be revealed by analyzing certain sub-element. The numerical simulation for fractures aperture has been done according to the statistical distribution patterns, and the fracture has been divided into several length-equaling sub-elements, then the mean aperture for each sub-element has been calculated, and the last part is the derivation of unit discharge formula and the water head formula for sub-element. Based on the seepage theory for network of rock mass, making use of unit discharge formula for coarse fractures, then the water heads for each fracture node can be calculated, after then the following is unit discharge formula of fractures. The following conclusions can be draw from this paper: that is there are great differences between the seepage for coarse fractures network and smooth fractures network of rock mass: (1) the unit discharge formula for coarse fractures and for smooth fractures is different, and the equivalent hydro-force aperture is smaller than the mean aperture ; (2) the water head distribution for them is different, because the curve for straight smooth fracture is a straight line, but for coarse fracture is a stairs line; (3) the calculation formula for conductivity matrix is different, and the detail characteristics in coarse fracture has been taken into consideration; (4) the non-uniform for aperture distribution has been taking into consideration in the sub-element method, which is more abide by the practical engineering. The study in this paper can give some references for practical engineering.