Study On The Mechanism Of Vacuum And Negative Pressure Infiltration Grouting For Unsaturated Silt Sand

In the actual construction and engineering application of grouting technology,it is often encountered in silt fine sand formations with small soil void ratio and low permeability coefficient.The traditional grouting method has poor grouting effect in this soil layer.The slurry diffusion radius is far from the theoretical diffusion radius.Vacuum negative pressure infiltration grouting can effectively solve this problem.However,only the qualitative effect of partial vacuum negative pressure on infiltration grouting has been obtained,and the mechanism of vacuum negative pressure on infiltration grouting has not been fully studied.For unsaturated soil,the soil sample is in a moist state and has a certain water content.The soil particles will absorb water from the surrounding environment,and the water between the particles will exist in the pores between the two particles in the form of liquid bridges.The permeability of the body and the spread of the grout during the grouting process have an important influence.Based on the “ Research on the Mechanism of Permeability Grouting in Unsaturated Silt-Fine Sand Layers under Vacuum Negative Pressure”,the National Natural Science Foundation of China established a two-dimensional mathematical model of liquid bridges.The following liquid bridge balance equation is derived,and the influence of liquid bridge morphology changes and liquid bridge fracture conditions under different negative pressures are studied.At the same time,the design and development of the permeability coefficient experiment of the unsaturated silt fine sand layer and the vacuum negative pressure infiltration grouting experiment have explored the verification analysis of the liquid bridge theory in the macroscopic water holding characteristics and grouting mechanism of the unsaturated silt fine sand layer.The main work and results are as follows:1.Theoretical derivation of the two-dimensional liquid bridge under equilibrium and negative pressure,and the establishment of the liquid bridge equilibrium equation based on the principle of surface free energy.2.Through numerical calculation method,the morphological change,water content and matrix suction of the liquid bridge under negative pressure are analyzed by examples,and the influence of the change of the liquid bridge morphology and the fracture condition of the liquid bridge under different negative pressures is studied.3.Through the unsaturated permeability coefficient experiment,the relationship between the soil-water characteristic curve and the permeability coefficient when negative pressure is applied is studied,and then the influence law of the liquid bridge on the unsaturated permeability coefficient is explored,and compared with the theoretical derivation.4.Design and conduct unsaturated soil vacuum negative pressure grouting experiments to study the influence of liquid bridge on the diffusion of vacuum infiltration grouting under different negative pressures and different initial water contents of soil samples,and summarize the differences in silt fine sand soil.The diffusion law of the slurry and the characteristics of the consolidated body under vacuum.