Freezing temperature field characteristics of multi-loop pipers under different working conditions at the interface of deep thick sand and clay

The design scheme of multiple-loop pipe freezing wall is an effective method to solve the problem of deep freezing, In order to study the freezing temperature field characteristics of multiple-loop pipes under different working conditions at the boundary of deep thick sand and expansive clay, the XRD test results of the original cohesive soil at the boundary were taken. ANSYS numerical simulation was used to compare under the skewed and non-skewed conditions of fine sand and expansive clay. Studies have shown that:multiple-loop pipes are frozen without non-skewed, and the temperature field of the frozen wall of the fine sand layer and the expansive clay layer develops in a regular, symmetrical and orderly manner. The main freezing center ring tube, inner ring tube, middle-inner tube, middle-outer tube, the outer ring tube form an intersection process in turn. As the freezing time increases, the freezing temperature between the middle-inner ring and the middle-outer ring tube develops from a parabolic shape to a trapezoidal cooling shape, and the temperature difference decreases. The outer side of the inner and outer ring tubes is inverted. The cooling effect on the inside of the inner tube is obviously better than that on the outside of the outer tube. When skewed, the temperature field of the freezing wall is ir-regular in the temperature field, and the superposition of the freezing cold front is random and discrete. The formation time of the frozen wall of expansive clay is seriously lagging behind deviation and soil properties have a greater influence on the temperature of the frozen wall. The deviation has a particularly obvious effect on the expansive clay. It is more consistent with the multiple freezing pipe broken events that occurred in a mine's freezing shaft sinking at the sand-clay boundary of the formation above -400 m. The research results can provide a reference for similar deep mine frozen construction.