基于渗流-侵蚀理论的岩溶充填介质注浆加固效果评价

Evaluation of grouting reinforcement effect for karst filling medium based on seepage-erosion theory

岩溶充填介质渗透失稳是地下工程突水涌泥灾害的主要类型之一,对其注浆加固效果的科学评价是保证地下工程施工安全的重要前提。基于自主研发的大型三轴渗流-注浆多功能试验平台,围绕影响注浆加固效果的关键因素:介质初始孔隙度与注浆压力,分别对注浆前、后充填介质开展变质量渗流试验,通过监测渗流演化过程中介质孔隙度、涌水速率的变化,系统分析注浆前、后充填介质渗透系数的降幅、各渗流阶段的演化特征以及流态转换临界时间点的延迟幅度,对不同充填状态的充填介质在特定注浆参数下的加固效果进行定量分析。试验发现:注浆提高了溶腔充填介质的抗渗流稳定性,延缓了孔隙度的快速演化,推迟了"突水"爆发阶段的出现时间,更系统地证实了渗流失稳"三阶段"演化模型的合理性;基于该试验结果建立的渗流转换临界点Ⅰ,Ⅱ的延迟时间与注浆压力、试样初始孔隙度的回归方程,不仅定量描述了注浆对各渗流演化阶段的影响,而且为岩溶隧道注浆加固效果评价提供新角度。

The instability of karst filling medium induced by seepage-erosion process often causes serious water-mud inrush disasters,and the scientific evaluation of its grouting reinforcement effect of karst filling medium is an important prerequisite for ensuring the safety of underground construction.In this paper,seepage-erosion tests before and after grouting were conducted via a self-developed large-scale triaxial seepage-grouting multi-functional test platform,focusing on the key factors of grouting reinforcement effect including the initial porosity of the medium and grouting pressure,and the changes of the medium porosity and the water outflow rate during the seepage process were monitored.The decline of the permeability coefficient,the evolution characteristics of each seepage stage and the delay amplitude of the critical point for flow transition were quantitatively analyzed,and then the reinforcement effect for the filling medium under specific existence conditions and particular grouting parameters were evaluated.The test results show that grouting improves the seepage resistance stability of the filling medium and delays the rapid evolution of porosity as well as the occurrence of the"water inrush"stage,which systematically confirms the rationality of the"three-stage"seepage theory.The regression equations of the delay time of transition pointsⅠ,Ⅱwith the grouting pressure and the initial porosity of the samples not only quantitatively describe the influence of grouting on each seepage stage,but also provide a new evaluation perspective for the grouting reinforcement of the filling medium in karst cavities.