Research On The Technology Issue Of Down-the-hole Hammer Drilling With Casing For Complex Stratum

With the development of our country's construction, more and more drilling engineering projects are need in complex stratums. Drilling in these stratums is bound to affect the relevant stability and balance conditions in these stratums. Some common phenomena may appear are as follows: fall of wall hole slumping,clumps,falling,leakage loss,water gushing,diameter curtailment,diameter augmentation and so on. If not handled properly, construction difficulties, accidents or even drilling failure may occur in the drilling process, which in turn may result in poor quality of the drilling, low efficiency drilling, high cost of drilling. Drilling with casing technology, an effective solution to drill in complex stratums, may successfully deal with the problem of protecting the wall of hole in the process of drilling. However, there are still many problems, such as: ambiguity classification of the complex stratums' systematic; inexplicit of methods of determining reasonable drilling tools and regulations in complex stratums; uncertainty of the method of the depth of casing and its impact factors of Down-the-hole Hammer Drilling with Casing.Mainly based on the causes of complex stratums and its characteristics, the requirements of current drilling construction, the paper conducted a research on complex stratums in a all round way , the specific impact of the drilling construction , reference the results of previous researches making a scientific classification of complex stratums: Incompact Stratum, Fractured Stratum, Water-sensitive Stratum, Loss Stratum,identified difficult problems of every kind complex stratums and reasonable drilling methods.And doing an analysis the level of difficulty of drilling with casing in a variety of soil and rock.Analysis of the characteristics, practical effect, the scope of application of existing three Down-the-hole Hammer Drilling with Casing Technology: Down-the-hole Hammer drilling with casing, percussive diamond coring with casing, simultaneous casing&coring method by pneumatic Down-the-hole Hammer drilling, optimizing and organizing the existing drilling technology,identifying drill tools and craft parameters and further improvement to solve the difficult problem of drilling in complex Stratums is also included in the paper. By applying engineering mechanics, fluid mechanics theory and drilling Engineering advanced theories at home and abroad, the paper inferred formula governing the dept in complex stratums and analyzed its impacting factors. By putting the theory into practice and based on the engineering geological investigation of thick sand and gravel layer in Chengguan railway, the paper tested the air-powered Down-the-hole Hammer drilling technology and the order parameters determined, in theory of this stratum follow-up casing the greatest depth is 20.8 meters, the scene protecting the wall of hole with casing an average depth is 15.7 meters, the most up to 18.3 meters, successfully deal with the common hard problem of drilling slowly when meet big isolated stone,falling,clumps,jamming of the drilling tools and so on; fairly good results is achieved.