The penetration grouting is very widely used in geotechnical engineering nowadays, but the slurry diffusion radius is not long enough because of low grouting pressure. The vacuum grouting method is proposed to solve this problem. However, there is no diffusion theory model of vacuum grouting, which makes the practical application lack scientific basis. In this paper, the distribution law of vacuum negative pressure in soil is deduced. Then, the boundary conditions of Maag's spherical diffusion model are modified by the vacuum pressure distribution law. After that, the vacuum modification model is deduced. Finally, Maag's model and modified model are analyzed according to a published experiment, which proves that the vacuum modification model is suitable for predicting the slurry diffusion of vacuum grouting. The proposed model provides a reference for the theoretical study of vacuum grouting.
Vacuum tube dewatering method and light well point method have been widely used in engineering dewatering and foundation treatment. However, there is little research on the calculation method of unsaturated seepage under the effect of vacuum pressure which is generated by the vacuum well. In view of this, the one-dimensional (1D) steady seepage law of unsaturated soil in vacuum field has been analyzed based on Darcy's law, basic equations, and finite difference method. First, the gravity drainage ability is analyzed. The analysis presents that much unsaturated water can not be drained off only by gravity effect because of surface tension. Second, the unsaturated vacuum seepage equations are built up in conditions of flux boundary and waterhead boundary. Finally, two examples are analyzed based on the relationship of matric suction and permeability coefficient after boundary conditions are determined. The results show that vacuum pressure will significantly enhance the drainage ability of unsaturated water by improving the hydraulic gradient of unsaturated water.
Vacuum dewatering method has been widely used in geotechnical engineering. However, there is little research on the groundwater level distribution under the effect of vacuum pressure which is generated by vacuum wells. In view of this, the groundwater level distribution in phreatic aquifer is analyzed. First, the vacuum pressure distribution in soil is analyzed through Darcy's law and steady-state seepage control equation based on established particles and pores model. Second, the boundary conditions are modified by the vacuum pressure distribution law and then the water level distribution equations in flow boundary and waterhead boundary conditions are derived. Finally, dewatering experiment is carried out to analyze the water levels in vacuum and nonvacuum dewatering and verify the theoretical model of water level distribution in vacuum dewatering. The results show that, in both boundary conditions, the water levels in vacuum dewatering are lower than those in nonvacuum dewatering. The theoretical values agree with the experimental values well, which proves the rationality of theoretical equations and predicting the water levels in vacuum dewatering method.
e deep vacuum dewatering method is effective for groundwater control in projects. By now, although the vacuum consolidation in soft soil foundation treatment has been analyzed much, the settlement of deep vacuum dewatering has not been researched sufficiently. Because of the extra vacuum pressure, the settlement should be analyzed further. In this paper, the settlement models are derived and analyzed based on the 2 vacuum pressure distribution models (plane seepage model and Johnson's model), Imai and Chai's vacuum consolidation models, and elastic model of traditional soil mechanics. And then a project case is provided to verify the theoretical models. e results show that the proposed model is suitable to predict the settlement and provide new references for vacuum dewatering engineering.
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