Research On Drilling Performance Of Cluster Pneumatic Down-the-hole Hammer

Large diameter down-the-hole(DTH)hammer in underground infrastructure construction,mining emergency rescue,and water wells and other large diameter drilling construction of rock crushing efficiency,construction speed,but the use of strict requirements for supporting equipment,single hammer prices,and engineering costs are higher.A cluster pneumatic DTH hammer combines several small DTH hammers to break the rock together,which is a more economical and feasible ideal method to increase the speed of large diameter hard rock drilling.However,the domestic research on cluster pneumatic down-the-hole drilling technology has just started.Due to the lack of necessary theoretical and experimental data support,there are some problems in the engineering test,such as unreasonable drilling parameters,the short service life of drilling tools,and poor speed-up effect.In order to further improve the mechanical performance of cluster pneumatic DTH hammer and improve the construction efficiency of large-diameter hard rock drilling,the structure of cluster pneumatic DTH hammer is optimized through finite element analysis;By establishing the rock breaking simulation model of cluster pneumatic DTH hammer bit and the nonlinear dynamic model of the piston,and using the method of the field test,the drilling performance of cluster pneumatic DTH hammer is studied,the rock-breaking efficiency and piston motion performance of cluster pneumatic DTH hammer bit under different drilling parameter combinations are analyzed,and the process parameters of cluster pneumatic DTH hammer drilling system are optimized.It has a certain theoretical reference and engineering application value for the design and development of cluster pneumatic DTH hammers and the optimization of drilling parameters.Firstly,combined with the pneumatic reverse circulation drilling technology,through the research on the distribution scheme of each sub hammer of cluster pneumatic DTH hammer,the scheme of uniform distribution of all equal diameters of six pneumatic DTH hammers is determined,and the distribution diameter is Φ 588 mm.The structure of the cluster type pneumatic DTH hammer support frame and the joint structure of the gas distribution box is optimized by the finite element method,and the overall structure design of the Φ830/346 mm cluster type pneumatic DTH hammer is completed.Secondly,the rock-breaking mechanism of the pneumatic DTH hammer is analyzed.Based on the Drucker-Prager rock constitutive model,the interaction model of piston-braze head-rock of cluster pneumatic DTH hammer is established by using ABAQUS software with non-reflective boundary conditions.The effects of double bit stress coupling,impact velocity,rotation velocity,impact frequency,and impact time interval on the drilling effect of bit in granite,sandstone,and mudstone are analyzed.The variation laws of the corresponding impact reaction force,the displacement of the drill bit invading the rock,the rebound velocity,the amount of rock breaking,and the specific work of rock breaking with the process parameters are obtained,and the optimal combination of process parameters and the optimal impact time interval is obtained.Then,the theoretical analysis of the piston motion law and the pressure,temperature,and gas mass flow rate of each gas chamber in each gas distribution stage of the pneumatic DTH hammer was carried out,and the nonlinear dynamics model of the piston was established,and the numerical calculation of multiple working conditions was carried out by using MATLAB software to obtain the piston speed,acceleration,front and rear gas chamber pressure and gas consumption variation law under a single cycle,as well as the pneumatic DTH hammer output performance under different rock hardness,air inlet pressure,back pressure and The optimal drilling parameters of cluster pneumatic DTH hammer in different strata were obtained,and the volume of air distribution box was optimized.Finally,through Ф580/215.9mm cluster pneumatic DTH hammer reaming drilling test,to verify the rationality of the structural scheme and the applicability of the reverse circulation drilling process,combined with the use of the site,the structure of the rationalization and improvement proposals.