峰后大理岩非线性渗流特征及机制研究

 在围岩开挖扰动区中，围岩应力和裂隙水压力将会显著地影响其渗流性质。当水头压力梯度增大时，渗流速率增大，Darcy流转化为非线性渗流。首先，采用研制的温度–应力–渗流耦合的岩石力学试验系统进行不同静水压力下大理岩峰后非线性渗流试验，研究渗流速率随压力梯度的演化规律，将其演化过程分为稳定Darcy流、Darcy流向非线性渗流过渡段和非线性渗流3个阶段进行分析，并采用完全二次多项式描述渗流速率与水头压力梯度的关系。然后，通过试验中记录的变形数据，拟合临界启动压力梯度和裂隙水力开度与试样侧向变形的函数关系式，得到不同静水压力条件下由水头压力引起的裂隙水力开度的变化规律；并深入分析临界启动压力梯度、固有渗透系数和二次项系数演化的内在机制。随着静水压力的升高，试样中裂隙水力开度逐渐减小，引起固有渗透系数逐渐减小，二次项系数和临界启动压力梯度逐渐增大；随着水头压力的增大，裂隙水力开度逐渐增大，引起固有渗透系数增大，临界启动压力梯度和二次项系数减小。

RESEARCH ON CHARACTER AND MECHACISM OF NONLINEAR SEEPAGE IN POST-PEAK MARBLE

For the excavation damage zone(EDZ) in underground construction，seepage is greatly influenced by the stress in the surrounding rock and the water pressure in cracks. For example，seepage velocity will increase with the water head pressure gradient increasing，and then the seepage becomes nonlinear instead of Darcy flow. So the properties of nonlinear seepage in cracked marble under different hydrostatic pressures and water pressures are focused on. Firstly，the seepage tests are performed using the self-developed temperature-stress-hydraulic coupling test system. According to the test results，the evolutionary law of seepage under different water head pressure gradients can be divided into three stages，namely，steady Darcy seepage，transition from Darcy seepage to nonlinear seepage and nonlinear seepage；and a complete quadratic polynomial is proposed to describe the relationship between water head pressure gradient and seepage velocity. Secondly，the relationship between critical water head pressure gradient and lateral deformation of rock specimen is described by a linear equation based on the deformation data；and then an empirical function is proposed for crack hydraulic aperture and the lateral deformation of specimen. Finally，the evolution of crack hydraulic aperture is studied，which is responsible for the variations of the critical water head pressure gradient，inherent permeability and quadratic term coefficient. Two conclusions are drawn as follows：(1) with the hydrostatic pressure increases，the crack hydraulic aperture reduces，which leads to reduction of the inherent permeability while augments of the critical water head pressure gradient and the quadratic term coefficient；and (2) with the water pressure increases，the crack hydraulic aperture increases，accordingly，the inherent permeability increases，but the critical water head pressure gradient and the quadratic term coefficient reduce.