Study On The Stability Of Large Diameter Deep Gas Drainage Borehole Casing In The Interface Of Hard And Soft Stratum

In recent years, the technology of gas drainage drilling at the surface ground had been widelyused in the field of coal mine. The technology is a good way to prevent the happening of the coalmine gas accident.It also can improve the efficiency of energy use.. The stability of the casing is toassure the safety of structure and key project to normal working, the study of casing is imperative.It is very important to study the stability of the casing which had wide coverage of knowledgeand multiple fields. Many factors affect the stability of casing. In the stage of production of thecasing, due to the process of production with the different level, material uniformity, ovality ofcasing affect its stability. In the process of drilling, cementing and laying, the configuration of thecement slurry, and the technology level of weld, the friction between casing and the earth,cementing cement, the height of the construction of higher ground casing, these factors also play arole to the stability of the casing. Some important factors which cannot be ignored are geologicalconditions and underground motion. Due to the complexity of underground structure, the frequentunderground movement and imperceptibility, this part of the factors is often very important.This paper try to analyze some factors influence the stability of gas drainage drilling at thesurface ground in DingJi Coal, Huainan. Considering the crustal stress of Huainan, circle of cement,formation pore pressure, the force situation of casing is analyzed in the process of cementing andlaying. The key work is to analyze how the interaction of Hard and soft formation influence thestability of the casing. This paper also summarized the characteristic of ground stress in Huainanarea. By means of FLAC3D, numerical simulate the simulation of gas drainage drilling in DingJiCoal, Huainan. Decorate in the interactive interface of hard and soft stratum with a number ofmonitoring stations, calculated the stress and strain of monitoring stations, got the maximum forcecurve, determine the location where casing are mostly vulnerable. The result of numericalsimulation played a guiding role for the construction. In the construction and use stage we should tostrengthen this monitoring position or take some reinforcement measures.FLAC3D is suitable forsimulation of geotechnical engineering, the calculation results has reference value for casing designand the construction work, save the cost.