Experiment study on water jet breaking rock by multi-orifice nozzle

Abstract：The experiments were conducted for 6 types of multi-orifice nozzles on water jet breaking rock,and the factors were analyzed with the rock breaking effect including numbers of nozzle orifices,hydraulic parameters such as erosion time,nozzle pressure drop,spray distance and confining pressure value.The results show that the more numbers of nozzle orifices,the more rounded shape of the jet drilling hole;rock breaking effect increases with the jet pressure drop increases linearly;under atmosphere submerged conditions,the optimal standoff distance for gaining the maximum hole depth and rock breaking volume is about 5 to 6 times of the equivalent nozzle diameter.In the confining pressure,with the confining pressure increases,a substantial decline in rock breaking effects,the breaking effect of the multi-orifice nozzle with equivalent diameter decreases with the growth of confine pressure.In the case of guaranteeing drilling diameter,to reduce the number of orifices helps to improve the efficiency of the nozzle breaking rock.The results can offer some helps for the jet bits design in the ultra-short radius radial horizontal drilling.