New technology for fluid-solid coupling tests of underground engineering and its application in experimental simulation of water inrush in filled-type karst conduit

According to the needs of large transportation, water conservancy and hydropower and mine projects large-scale fluid-solid coupling model tests on new technology are performed based on geomechanical model tests. This technology includes three aspects, new fluid-solid coupling similar materials, 3D visual solid-liquid coupling test system, and monitoring-analysis technique of multi-physics fields. The preparation principle of the fluid-solid coupling similar materials is proposed. Various slightly coupling regulators are chosen to add to the materials, making the performance parameters of strength, permeability and density regulated separately. The similarity of materials is greatly improved, and the properties of the materials can remain stable under the long-term effect of water. Low-strength and medium-strength rocks, fracture zone and fillings can be accurately simulated by using the materials. With the function of automated static loading and digital water pressure loading, the 3D visual solid-liquid coupling test system realizes direct large-scale interaction between pressure water and similar materials, and provides a visual place for the simulation of seepage and water inrush process under the condition of fluid-solid coupling. The precise acquisition and analysis of seepage pressure, strain and displacement in water environment can be realized by fiber technology, flexible waterproof technology of resistor elements and automatic data acquisition and analysis system. Finally, the 3D large-scale model tests on water inrush in filled-type karst conduit are carried out based on Shangjiawan tunnel in Baokang-Yichang expressway. The process of water inrush is truly reproduced, and the catastrophe characteristics of water inrush in filled-type karst conduit are revealed. The new technology has been successfully used in the model tests and provided technical assurance for good results.