Study on Controllable Splitting Grouting of Loess Based on Bingham Fluid

At present, most grouting designs are blind, some grouting parameters rely on experience, and the control of grouting process is not suitable enough, which cannot ensure the grouting quality, but also hinder the further promotion of splitting grouting. The slurry is mainly in the form of softening of the loess. Most of the cracks formed in the grouting hole surface are vertical cracks and horizontal cracks which appear at the shallow depth. The slurry diffuses in the cracks and eventually condenses and hardens to form slurry veins. The distribution of the slurry veins in the soil greatly affects the grouting effect. In order to realize controllable splitting grouting in the loess, The diffusion theory of Bingham slurry in loess is extrapolate by using the flat narrow seam model. It is concluded that the diffusion radius is related to the parameters such as grouting pressure difference, crack parameters and slurry properties. Taking this as the starting point, the field grouting test is designed. The results show that by controlling the grouting parameters and construction process, the deviation of slurry vein size and spacing of the design value can be realized within ± 40%; when the grout pressure is low, the loess is mainly extrusion is the main effect, and the extruding diffusion radius is about 1.2~2 times the diameter of the grouting pipe. Splitting is dominant when the pressure is higher; the core structure of the composite foundation pile formed in the test has a lower strength at a shallower depth. Therefore, the actual grouting should consider increasing the strength of the surface structure, which provides a certain reference for the design of grouting parameters in the actual grouting project.