A method of preparing wall protecting mud for continuous wall grooving underground a sandy geologic layer

The invention relates to the technical field of underground construction and provides a method of preparing wall protecting mud for continuous wall grooving underground a sandy geologic layer. The specific gravity of the wall protecting mud is 1.2-1.4 g/cm , the viscosity is 23-40 s, and the sand percentage is less than 5%. The method includes (1) a step of mixing bentonite and water according to a weight ratio of 1:1-3 in a mud box, fully stirring the mixture, and then storing and fermenting the mixture for 24-48 h to obtain bentonite mud; (2) a step of mixing clay, water, sodium carbonate and barite according to a weight ratio of 100:200-250:1-2:1-3, and fully stirring the mixture in a mud box to obtain clay mud; (3) a step of mixing the bentonite mud and the clay mud to obtain the wall protecting mud, with the water-material ratio of the wall protecting mud being controlled to be greater than 60:40 and lower than 70:30, and the wall protecting mud comprising 0.15-0.4% of the sodium carbonate and 0.15-0.6%