为了探究承压水下巷道围岩的渗透突变机理，针对空心岩样的渗流-应力特征开展了一系列室内试验和渗透突变表征模型研究。自主研制了一套空心岩样径向渗流-轴向应力试验系统，突破了仅开展轴向渗流的传统试验条件限制，实现了径向渗流及轴向应力同步进行。采用该新型试验系统，以孔径(5-20mm)和水压(0.5-2.5MPa)为变量开展多组空心红砂岩渗流-应力试验，得到空心岩样径向渗流-轴向应力特征。试验结果表明径向渗流的蚀损作用引起岩样内聚力、内摩擦角等力学参数衰减，增大水压，渗流的蚀损作用变强，岩样内部裂隙贯通通道形成时间缩短，渗透突变现象提前发生。大孔径岩样对轴向应力敏感度更高，内部结构受径向渗流蚀损作用易破坏，渗透突变发生时间缩短。岩样渗透率在试验过程中存在三种状态：(1)以孔隙结构为主要渗流介质的孔隙渗流状态，(2)以局部裂隙结构为主要渗流介质的非稳定渗流状态，(3)以贯通裂隙结构为主要渗流介质的渗透突变状态。渗透率达到峰值的试样渗流介质为受水压影响产生的贯通裂隙结构，峰值渗透率随水压增大呈线性增长，与孔径没有明显关系。以裂隙体积变化为纽带建立空心岩样渗透突变表征模型，模型计算值与实验结果吻合良好。以屈服应力/应变、峰值应力/应变为临界条件将渗透率演化曲线分为三个阶段：(1)渗透率微增演化阶段、(2)渗透率突增演化阶段、(3)峰后渗透率演化阶段。其中，渗透率突增演化阶段是突水灾害发生的控制环节，需在此之前采取注浆封堵、输水降压等措施预防事故发生。

To explore the seepage mutation mechanism of roadway surrounding rock under confined groundwater,a series of laboratory tests and model studies were conducted for the seepage-stress characteristics of roadway surrounding rock.A set of seepage-stress test system for hollow rock samples was developed,which broke through the limitation of traditional test conditions that only conduct axial seepage flow and achieved the simultaneous operation of axial stress and radial seepage.Based on the new test system,the radial seepage tests of several groups of hollow red sandstone are carried out by using bore diameter (5-20 mm) and hydraulic pressure (0.5-2.5 MPa) as variables.The permeability evolution law and radial seepage characteristics of hollow rock samples are obtained.The test results show that erosion damage of radial seepage causes the attenuation of mechanical parameters such as cohesion and internal friction angle of rock samples,with the increase of water pressure,the erosion damage of seepage becomes stronger,the formation time of fracture through channel in the hollow specimen is shortened,and the seepage mutation of seepage occurs in advance.The hollow specimen with large bore size is more sensitive to axial stress,the internal structure is more easily damaged by radial seepage erosion damage,and the time of seepage mutation is shortened.The permeability of the rock specimen experiences three states during the test:① the pore seepage state with pore structure as the main seepage medium,② the unsteady seepage state with the partial fracture structure as the main seepage medium,and ③ the seepage mutation state with fissure structure as the main seepage medium.When the permeability reaches the peak value,the seepage medium of the specimen is the through fracture structure caused by the influence of water pressure,the peak permeability increases linearly with the increase of water pressure,and has no obvious relationship with pore diameter.According to the change of fracture volume,the characterization model of seepage mutation of hollow rock sample is established,and the calculated results of the model are in good agreement with the experimental data.According to the critical points of yield stress/strain and peak stress/strain,the permeability evolution curve was divided into three phases:① permeability increase evolution phase,② permeability rapidly increase evolution stage,and ③ post-peak permeability evolution stage.Among them,the sudden increase in permeability evolution stage is the control stage of water inrush disaster occurrence,before that,measures such as grouting and blocking,water delivery and pressure reduction shall be taken to prevent disasters.

1 空心岩样径向渗流试验方法

   1.1 试验方法概述

   1.2 试验系统

   1.3 试样制备

2 空心岩样径向渗流-轴向应力特征

   2.1 空心岩样轴向应力特征

   2.2 空心岩样径向渗流特征

3 空心岩样渗透突变表征模型

   3.1 应变表征渗透率数值模型

   3.2 应力表征渗透率数值模型

4 结论