The Simulation Research On The Mechanism And Treatment Of Shaft Wall Fracture In Thick Alluvium Induced By Dewatering

Fracturing of the shaft lining in the thick alluvium is a special mining geologic hazard. Study show that the vertical additional stress induced by mining and artificial dewatering is the primary factor to the failure. Therefore, a reasonable determination of the additional stress induced by dewatering has great significance for the failure analysis and the evaluation of the security state of the shaft wall. The thesis from the view of the reason and treatment of shaft lining cracking presents a detailed study and anaysis for the vertical stress induced by dewatering through FLAC^3D numerical modeling. Also the thesis carries through the following research work aiming at the numerical simulation in the methods of shaft lining treatment based on theoretical analysis and on-site data analysis:(1)The numerical simulation model was built based on practical engineering geologic and hydrogeologic conditions of shaft lining fracturing in the thick alluvium. The vertical additional stress acted by drainage deposition and stress, strain in shaft wall have been researched, also the process of curing the shaft linging fracture had been studied. A set of effective numerical simulation of wrecking of shaft wall has been formed.(2)The additional stress of shaft wall increases gradually with depth. Which reaches the extremum at the interface between the surface soil and bedrock until the shaft wall was wrecked. The numerical anlysis study based on decling pore pressure cause increase of efficient stress and FLAC3D. The additional stress values of dewatering depth is ten, twenty, thirty, fourty, fifty meter and force staus of shaft wall have been carried out. Also the plastic deformation of dangerous spot has been examined by the fourth strength theory.(3)The fracture mechanism of shaft wall in the thick alluvium is the additional stress on the lining at the interface between soil and shaft wall, which results from mining and decline of water-bearing zone. The additional stress due to the interfaction between soil and shaft lining make the shaft wall undertake the force cause the fracture of lining. This is reason why the fracture most take place at the inside of it, then enlarge to the outside part.(4)Strata and unloading method are used to cure the fracture of shaft wall .The results show strata and unloading method can effectively help to cut down the vertical sress of shaft wall.(5)The numerical simulation results compared with the field observation of before and after the shaft wall treatment. Both have the same trendline. This paper will provide extent experience for the evaluation of shaft wall treatment.