High Pressure Jet Grouting Mechanism Test And Numerical Simulation Research

With the development of China’s economy and technology,the development and utilization of underground space has become the current development trend.Underground engineering is faced with challenges such as collapse and water inrush due to the impact of groundwater and geological conditions.High-pressure rotary jet grouting technology is an effective means of strengthening soil layer and waterproofing.It cuts the soil by the pressure formed by the jet,and replaces the soil particles with slurry to form a pile with a certain diameter.At present,the design theory of high-pressure rotary jet grouting method is based on engineering analogy.The study of the mechanism of high-pressure jet stream breaking soil needs to be continued.In this paper,the variation law of the high-pressure jet stream breaking distance under different conditions is studied by basing on the sand and sand-pebble soil jet-breaking model test,and using the discrete element software to simulate the high-pressure jet grouting breaking process with the fluid-solid coupling model.It aims to deepen the understanding of the mechanism of high-pressure jet grouting and provide a reference for the design and construction of high-pressure rotary jet grouting.The main research contents are as follows:(1)Firstly,the model tests in sand were carried out for the three influencing factors of injection pressure,overburden pressure and injection time.By changing the parameters such as injection pressure,overburden pressure and injection time,the variation law of injection distance with injection pressure,overburden pressure and injection time is obtained.Through model test research,it is found that the injection distance increases with the increase of injection pressure,and the increasing trend gradually slows down.The injection distance decreases with a concave curve as the overlying pressure increases.The longer the injection time,the greater the injection distance,and the increasing trend gradually slows down,and finally reaches stability.The sensitivity analysis shows that the injection pressure has the largest influence on the injection distance,followed by the injection time,and the overlying pressure has the smallest influence on the injection distance.(2)A model test of jet flow soil breaking was carried out in a sandy pebble soil layer to study the effect of the size of pebble particles on the main mechanical properties of the jet flow breaking soil process and influence on the effect of jet stream breaking soil.As the size of the pebble particles increases,the main role of the jet flow gradually changes from splitting to seepage,and the jet distance decreases significantly.The spraying distance shows an increasing trend with the increase of the spraying pressure,and the increasing trend gradually slows down.The jet flow decreases linearly with the increase of the overlying pressure.(3)The numerical simulation is used to simulate the model test,and it is clear that the mechanism of jetting the soil for breaking and effects of changing injection pressure,overburden pressure and adding pebble particles on mesomechanical properties in soil.The simulation results of the particle flow simulation model show that the simulation results are not much different from the experimental results.(4)The soil model is expanded to simulate the ultra-high pressure jet flow breaking soil in the sand layer,and the macroscopic physical phenomenon and mesomechanical changes of the high pressure jet flow breaking soil are obtained.The injection distance increases stepwise with the increase of injection pressure.The cavity width increases stepwise + zigzag with the increase of injection pressure.The change of soil particle displacement with spray pressure is similar to the change of spray distance and cavity width.The fluid pressure distribution in the soil layer fluctuates with positive and negative peaks.As the injection pressure increases,the peak fluid pressure also increases.As the simulation proceeds,the fluid pressure in the cavity gradually becomes disordered and distributed under the action of the vortex.