Research And Development Of New Type Of Pulse-free Wet-mix Shotcrete Machine

Compared to dry-mix or semi-wet shotcrete,wet-mix shotcrete technology has the advantages of low dust and high strength,but the working principle of traditional wet-mix shotcrete machine determines its concrete jet pulse which led to the big problems of high rebound rate,more tired work,low efficiency of shotcrete and the blind area during the shotcrete progress,which lead to cannot achieve automation intelligent shotcrete.In this paper,through many means such as theoretical analysis and numerical simulation and experimental research,the pulse generating mechanism of the traditional wet-mix shotcrete machine was explored,and concept of peak cut design was put forward,a kind of pulse concrete Wet-mix shotcrete machine was designed,and the effects of concrete conveying from the pulse wet-spray machine was analyzed.Firstly,the structuer and working process of traditional wet-mix shotcrete machine was analyzed,especially in the process of the relative position of two concrete cylinder with distributing valve swing.It is concluded that there was a indirect connection between the hopper and the transfer pipeline,which can relieve the pressure of transfer pipeline.And through the anlysis of the concrete stress state and flow characteristics,it is concluded that master cylinder stopping pumping concrete,the pressure of transfer pipeline was relieved and the reflux of concrete is the major causes of pulse producing.Aiming at the concrete relief and backflow problems in the transfer pipeline when the distribution valve of the traditional wet-mix shotcrete machine is swinging,the sealing baffle on the distribution valve is designed to solve the concrete relief and backflow problems.By analyzing the flow state of concrete,the method of peak cutting and valley filling is proposed to solve the concrete pulse,thus a three-cylinder pulse-free wet shotcrete is designed,which completely solves the pumping and spraying pulse of the wet shotcrete.The rheometer of EDEM model is set up,through the determination of setting parameters of concrete in the EDEM.And the model was standardized connecting with a experiment by rheometer.The three cylinder type no pulse three-dimensional model of wet-mix shotcrete machine was established in EDEM,and the working progress of this no pulse wet-mix shotcrete machine was simulated.The pumping flow characteristic and distribution state of concrete was analyzed,which verifies the feasibility of this three cylinder type no pulse wet-mix shotcrete machine.The test platform for pumping speed and pumping pressure of wet-mix shotcrete machine was established.The concrete pumping motion was analyzed by the test of pumping speed and pumping pressure using traditional wet-mix shotcrete machine,backflow of wet-spray machine and no pulse of wet-mix shotcrete machine,by which the pumping pulse of traditional wet-mix shotcrete machine can be concluded as following.First,part of the air is inhaled when the machine piston absorbs concrete,which can make many gaps in the concrete cylinder.Second,the main concrete piston stops,when the distribution valve swings.Third,there is phenomenon of concrete pressure relief and backflow during the distribution valve swinging.And the influence of concrete pumping pulse on concrete conveying pressure is measured.It is also measured that the pulse-free pumping of concrete can effectively reduce the amount of collapsing material during spraying.Roadway model was established,to carrying on the industrial test of mechanical arm vibration,the volume of shotcrete,the result of shotcrete and the rebound of rebound,using traditional wet-mix shotcrete machine and no pulse wet-mix shotcrete.It is concluded that the shotcrete vibration can be reduced effectively,the shotcrete efficiency can be increased effectively,the shotcrete quality and the flatness of wall space can be improved effectively,and the shotcrete rebound can be reduced effectively.