Study on safe tunneling penetration technology for large diameter rescue wells

The tunneling well section refers to the formation with a certain thickness reserved at the bottom of the well during the construction of the rescue well to prevent the water from the overlying rock strata from entering the roadway, and to ensure that the dynamic pressure at the bottom of the hole does not cause damage to the roadway roof when the casing is inserted and the well is cemented. In order to achieve safe and rapid lifting of trapped personnel to the surface, it is required that the rescue well has a large diameter, excellent and fast drilling, and accurate targeting, while maintaining the integrity of the roadway roof and controlling mud influx into the roadway. Through theoretical analysis, numerical simulation, field application and other research methods, the construction technology of the rescue well penetration roadway was optimized. Through three-dimensional similarity simulation, roof displacement of roadway excavation, surrounding rock disturbance during drilling process, safety distance of through roadway section, and casing depth were studied. At the same time, the air DTH hammer reverse circulation drilling process was optimized to achieve effective packer aquifer and sidewall unstable strata, and ensure that the rescue capsule is placed and lifted smoothly in the rescue well. Taking the ground rescue well in the refuge chamber of a coal mine in Shanxi as an example, a numerical simulation model of the roadway excavation and drilling process was established. The simulation results show that:① the main damage methods of the roadway and the surrounding rock of the borehole include shear failure and tensile failure with the domination of shear failure. The smaller the cohesion of formation rock, the greater the width of the plastic failure zone of surrounding rock. After the roadway is excavated, the height of the roof plastic zone reaches 9.59 m and the maximum roof subsidence is 15.9 cm. ② During the drilling of the large-diameter rescue well on the ground, the drilling destroyed the original stress balance of the stratum, causing the stress redistribution of the surrounding strata, causing the surrounding strata to produce moving deformation and plastic damage zones, which were symmetrically distributed in the center of the wellbore. The range of horizontal displacement is 20.3-90.5 mm, and the width of plastic failure zone is 1.43-1.82 m. ③ Under certain conditions of bottom-hole load, with the increase of the through-way distance, the roof of the roadway has a large tensile plastic strain at first. When the through lane interval length increases to more than 15 m, the roof plastic strain weakens, The roadway distance continues to increase, and the plastic strain of the lateral side increases due to the extrusion effect. The research on the safety penetration technology of large-diameter rescue wells is a further improvement of the construction technology of rescue wells.