Simulation Analysis For Casing Pipe Structure Of DTH Hammer Dirlling

With the development of China’s economic take-off and construction, drilling inthe complex stratum, especially in the collapse, loose, missing stratigraphic area, thestrata of borehole will cause disturbance during the process of drilling, resulting ainstability which is originally in a relatively stable state and balance, due to the loss ofconstraint,the hole wall always occurs collapse, off the blocks, leakage, holedeviation. If it is not handled properly in the complex stratum drilling, the explorationwill make it difficult to continue because of drill hole card or buried drill accident,which will force to stop drilling, and even a deterioration that makes the drilling holescrapped.Theoretical research of the mechanism for pore wall instability and missingstrata in different rock stratum has been made at home and abroad, simulation studyalso has been put into experiment, a variety of new material, new program and newtechnology are carried out, these methods about how to deal with complex stratum,are increasingly mature and improve. On the research of drilling technology, we use aseries of drilling method integrated and comprehensive management to cope with thecomplex formation, and provide a new idea to solve similar drilling problems.At Molybdenum Mine in Luanchuan, because of blind exploitation, minestratigraphic information is out of unified management. There are a lot ofunderground air scattered distribution areas, many of them are blind mined-out. Inaddition, due to the formation of internal and external conditions, some goaf collapse,faulted zones of rock sandwiched between loose broken band, Unstable rock drops, even worse, the goaf blast caused cracks criss-cross, strata leakage, all of thesecomplicated factors make exploration become more difficult by using ordinarydrilling technology or a single drilling method.This paper is mainly about the drilling challenges and drilling technology inLuanchuan Molybdenum Mine. Experimental research on the whole hole reversecirculation drilling, C·S·R partial reverse circulation drilling and DTH Hammerdrilling with casing have been made in order to solve the hole drilling in complexstratigraphic which is always poor quality, low efficiency and high costs. Meanwhile,drilling technology of DTH hammer and Structure optimization has also been studied.The main feature of DTH Hammer Drilling with casing is the casing pipe anddrill follow-up synchronization, protect hole wall effectively. DTH hammer drillingwith casing exist three problems:(1) the thickness and strength of the casing pipemake itself can bear far less than the drill pipe;(2) the casing pipe has to withstandthe vertical drill bit pressure and the potential impac t of the hole hammer, the pipemay be broken at thread area;(3) the bottom of the casing pipe thread often fatiguefracture. In order to improve the casing thread strength and increase the drilling depthwith casing pipe, this paper has made a simulation analysis in chapter five by usingANSYS finite element analysis software about the nominal diameter, pitch, heightof thread and the bottom corner of trapezoidal. Finally, the structure of the casing shoewas optimized. The results of the optimization for casing thread: d=137.9mm, p=10mm, h=2.6mm, β=68°, the length of the casing shoe: S=400mm.