Evaluation of grouting reinforcement effect for karst filling medium based on seepage-erosion theory
LIU Qi1，2，CHEN Weizhong1，3，YUAN Jingqiang1，WANG Yaxiong4，WAN Hao4
(1. State Key Laboratory of Geomechanics and Geotechnical Engineering，Institute of Rock and Soil Mechanics，Chinese Academy of Sciences，Wuhan，Hubei 430071，China；2. University of Chinese Academy of Sciences，Beijing 100049，China；3. Geotechnical and Structural Engineering Research Center，Shandong University，Jinan，Shandong 250061，China；4. Poly Changda Engineering Co.，Ltd.，Guangzhou，Guangdong 510000，China)
Abstract：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 points I，II with 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.
2020, Vol. 39 
