Study on the Deformation and Failure Characteristics of the Long Composite Insulated Cold Transmission Pipe in Deep Mines

Abstract

To address the delamination and water leakage caused by the fracture of insulated chilled water pipeline (ICWP) in the process of long-distance drilling through deep strata, a new insulated cold transmission pipe with a composite structure was designed based on the actual project. The mechanical and deformation characteristics of the mortar materials of the different filling layers were investigated using uniaxial compression and Brazilian split tests. The distribution law of the maximum principal strain field on the surface during the test process was obtained by applying the digital image correlation method. Based on the experimental results, the finite-difference model was established and FLAC3D was used to analyze the stability of the long-distance composite structure ICWP under different stress conditions. The numerical results show that when the ground stress exceeds 12 MPa, the plastic damage occurs in the inner and outer filling layers of the ICWP. When the ground stress reaches 17.5 MPa, there is a small plastic zone in the cold transmission pipe, but the composite structure ICWP does not affect the regular operation of the pipe. Based on that, the mapping relationship for the plastic damage rate of the inner and outer filling mortar of the ICWP to the ground stress and the parameters of the insulation pipe was constructed to provide a theoretical basis for improving the deformation damage resistance characteristics of the composite structure ICWP.