Research Of Numerical Simulation On None Backflow High Pressure Rotary Jet Grouting Process

In view of the backflow problem of traditional high pressure rotary-jet grouting,the method of adding ST-1 plant glue to cement slurry to change the flow pattern is often used to achieve the none backflow high pressure rotary jet grouting.But this technology is still in the its development stage.In view of the lack of understanding of the rheological characteristics of plant glue slurry and the difficulty in predicting the pile forming effect of none backflow high pressure rotary jet grouting,this paper studied the rheological properties of plant glue slurry and the process of none backflow high pressure rotary jet grouting by indoor test and numerical simulation.The main work and research conclusions are as follows:(1)Through rheological test,it is found that plant glue slurry belongs to power law fluid.Orthogonal tests with three factors and four levels of water-solid ratio,plant glue and bentonite were designed.The results show that plant glue has a significant effect on the rheological properties of grout,which makes the grout appear non-Newtonian and reduces the strength of the stone body.The water-solid ratio is the key control factor of slurry viscosity and determines the strength level of the stone body.Bentonite slightly increases the viscosity of slurry,but has little effect on rheological properties and strength.(2)Through the simulation of grout flow in hole,the flow was analyzed.Numerical simulation of control variables shows that increasing grouting pressure,decreasing gap width between grouting pipe and hole wall and decreasing diffusion distance of grouting slurry at the bottom will increase the pressure at the hole mouth.(3)Through the simulation of power law submerged jet,it is found that the jet velocity decreases and the flow direction deviates to the surface due to the influence of slurry mixture.The higher the mixture viscosity is,the faster the jet velocity attenuation is and the more significant the direction deviation is.The higher the grouting pressure is,the less the efflux is affected,but the velocity attenuation trend remains unchanged.Formation depth has little effect on jet grout.(4)The accuracy of the model is verified by comparing the numerical simulation results with Shen’s prediction formula for the radius of high pressure jet grouting pile.By applying the formula to an engineering example,it is found that the calculated results are accurate,and the causes of pile diameter fluctuation are analyzed.Finally,the Virtual Reality content of none backflow high pressure jet grouting process is displayed.