Model tests on stress and deformation of freezing-pipes during multi-circle freezing before excavation

In order to study the stress and deformation law of freezing pipes during multi-circle freezing, model tests are carried out based on the similarity theory. The multi-direction law of the freezing pipes under deep ground pressure before excavation is acquired. The following conclusions are drawn through analysis: the deformation of freezing pipes before the stage of excavation is completed during the ealier freezing stage; the strain of freezing pipes in clay stratum is larger than that in sand stratum; the maxmium tension stress in clay stratum is 97.7 MPa, while the maxmium compression stress is 161.5 MPa, and the bending stress is 1.7 times the axial one. The maxmium bending stress is 0.62 times the yield load of freezing pipes, while these stress is very small in sand stratum. The model test aim to improve the stress performance of freezing pipes, to reduce the strain energy storaged in freezing pipes before excavation and to reduce the failure rate of freezing pipes during excavation.