Experimental study of the axial movement of the pipeline in permafrost conditions with changes in soil temperature and humidity

Abstract

The significant part of the frozen soils, common of the northeastern regions of the laying of pipelines, loses its bearing capacity when the temperature rises to the values of melting ice. In turn, the loss of the design position of the pipeline section located in the thawed soil area causes unacceptable deformations, which can lead to incidents and accidents. The most dangerous places arise at the boundaries of sites with different soils properties, and primarily at the border of frozen and thawed soils. Currently, to evaluate the thermal interaction of pipelines with frozen thawing soils, data are used for ordinary thawed soils, however standard methods are not suitable in these cases, since they do not take into account a sharp change in the properties of frozen soils during thawing. The authors conducted studies of soil resistance (coefficient of soil reaction) to the longitudinal displacements of the pipeline depending on the temperature and humidity of the soil. For this purpose, an experimental model of a pipeline in frozen ground was developed. The main characteristics of the model and the experimental technique are described in detail. The results of studies of the coefficient of soil reaction in the longitudinal direction, as well as the ultimate shear stresses depending on the temperature and humidity of the soil, the type of soil and the depth of the pipeline are presented. The dependence of the coefficient of soil reaction on the ratio of the depth of the pipeline to its diameter is shown. It was established that at a temperature t = –8... –10 °С and humidity w = 10...15 %, the highest value of the coefficient of soil reaction is achieved. In the absence of moisture, the temperature does not affect the coefficient of soil reaction. The lowest coefficient of soil reaction for frozen soils is achieved at a positive soil temperature.