Experimental Investigation Of Groutability And Quantitative Evaluation Of Reinforcement Effect For Strongly Weathered Granite

The 21st century is an era of great development of underground space.Geological hazards caused by underground engineering crossing splitingd zones and weathered rock strata seriously threaten the safe development of underground space.Among them,strong-fully weathered granite rock mass is easy to become an important disaster source of large-scale deformation,collapse,water gushing and sand gushing under engineering disturbance due to its poor integrity,low strength and easy to lose stability.Theory and practice show that grouting is an effective means to prevent and control such disasters.However,influenced by the characteristics of the grouted rock and soil,the properties of grout and grouting control methods,there are significant temporal and spatial differences in the diffusion form of grout in strongly weathered granite and the effect of grouting reinforcement,which makes it difficult to select the key indexes such as grouting pressure,grouting rate and grouting ratio in grouting design.Therefore,it is of great theoretical and practical significance to analyze and evaluate the groutability of strongly weathered granite rock mass,summarize grouting reinforcement modes and quantitatively evaluate the effect of grouting reinforcement.In this paper,based on indoor grouting simulation test,combined with theoretical analysis,numerical simulation and other methods to carry out systematic research.The basic physical indexes of injected rock and soil are obtained,and the effects of physical parameters on its mechanical and permeability characteristics are studied based on the test of physical properties of S WG Furthermore,the grouting simulation test of strongly weathered granite is carried out by using single cement slurry.The grouting criterion considering the influence of particle size,water cement ratio,grouting pressure,clay content and relative compactness of strongly weathered granite is established.The spliting pressure and the spliting path propagation process of strongly weathered granite are studied by using RFPA numerical analysis software.The calculating formula of spliting pressure characterized by small principal stress and cohesion of injected medium is obtained.On this basis,the grouting diffusion strengthening mode of strongly weathered granite is divided and its strengthening mechanism is explained.The grouting reinforcement experiment of strong weathered granite was carried out.The influence of particle size,clay content,relative compactness and water cement ratio of grouting on grouting reinforcement effect was analyzed by orthogonal test method,and the main factors controlling grouting reinforcement effect were determined.The test results show that the main controlling factors of the strength of grouting reinforcement body are cement slurry water cement ratio and clay content of grouting medium,and the main controlling factors of the impermeability of grouting reinforcement body are cement slurry water cement ratio and relative compactness of grouting medium.Through the fitting analysis of test data,the quantitative relationship between grouting reinforcement indexes such as strength and permeability coefficient of grouting reinforcement body and factors such as cement slurry ratio,relative compactness of grouted medium,clay content and curing time is established,and the quantitative evaluation of grouting reinforcement effect of strong weathered granite is realized to a certain extent.The research results in this paper are of great significance for improving the grouting design method of strongly weathered granite and guiding the successful implementation of engineering practice.