STUDY OF THE BACKFILL SOIL PRESSURE INFLUENCE ON THE MAXIMUM ALLOWABLE SPAN LENGTH IN PIPELINE UNDERGROUND LAYING ON THE SUPPORTS OF CONTAINERS FILLED WITH SOIL
The most appropriate technical solution when crossing melt subsiding permafrost with island permafrost is the underground laying of pipeline with taking actions for fixing its vertical position at the design reference marks. The authors of this work propose a method of laying pipelines using supports of containers with soil to reduce pipe settling in conditions of island-type distribution of subsiding permafrost. Study of the impact of backfill soil on the underground pipeline laid on the supports of containers with soil, will allow to improve reliability of the pipeline and to determine the optimal spacing of supports of the containers with soil. Aims and Objectives Determining the extent of the backfill soil pressure impact on the maximum allowable span length of the pipeline laid on the supports of containers with soil. Methods Theoretical study of the effect the backfill soil pressure exerts upon the stress-strain state of the pipeline and the maximum span length allowable in terms of strength. The calculations are based on the improved calculation of beam crossings without compensation for longitudinal stresses. Results The impact of various ground conditions on the maximum allowable span length and the stress-strain state of a pipe section has been studied. The plots of changes in the allowable span length, longitudinal stresses and bending moments, depending on the density of backfill soil have been constructed. Conclusion According to the results of the calculations: - higher specific weight of the backfill soil results in reduction of the allowable span length, yet the gradient of reducing span length is non-permanent. When the values of specific weight of the backfill soil increase, the gradient magnitude decreases, and the decrease is non-linear; - the values of the bending moment in the most stressed section increase and the value of the bending moment from longitudinal force decreases with increase in specific weight of the backfill soil, the gradient of changing moments being the same by the absolute value. With further increase in specific weight of the soil, the gradient magnitude remains constant.