Determination of controlled parameters for designing a network for geotechnical monitoring of underground pipelines in the cryolithozone

Abstract

Relevance. Determined by the need for geotechnical monitoring in the areas of distribution of permafrost soils for underground pipelines. The geotechnical system “permafrost soil – underground pipeline” is subject to the influence of exogenous geological processes during operation, cyclical changes in the state of soils of the seasonal layer of thawing and freezing, thawing of permafrost soils from the thermal effect of the pipeline, changing the plan-altitude position. The variety of schemes for interaction of the pipeline body with varieties of lithological structure of permafrost soils along the route should be worked out in detail at the design stage and also assessed in detail during geotechnical monitoring of the pipeline. The lack of regulatory requirements for the monitored parameters of underground pipelines leads to the use of non-standardized and varied monitoring networks from project to project. The lack of standard values ​​for the maximum deformations of an underground pipeline leads to the need to use calculation methods for determining the maximum deformations of the base and pipeline. The authors proposed the use of a comprehensive methodology for calculating underground pipelines, developed by employees of JSC TomskNIPIneft to determine the maximum permissible deformations of the pipeline at each point of the route with the presence of permafrost soils at the design stage, with further use of the results obtained as a controlled criterion when conducting geotechnical monitoring. Aim. To determine the controlled parameters for geotechnical monitoring of underground pipelines in the cryolithozone at the operational stage based on the application of a comprehensive methodology for calculating underground pipelines, as well as the formation of requirements for the system of information points. Methods. Review of the regulatory framework for geotechnical monitoring, analysis and evaluation of the applied methods and designs for monitoring underground pipelines, analysis of a comprehensive methodology for calculating underground pipelines in relation to the purposes of geotechnical monitoring. Results. Based on the results of the review of regulatory and technical documentation, the authors have revealed a lack of specification of methods, equipment, volume of the geotechnical monitoring network and frequency of pipeline monitoring, as well as the requirement for the use of the calculation method of limiting deformations and the lack of description of possible methods. A detailed analysis of the complex methodology for pipeline calculations, developed at JSC TomskNIPIneft, substantiates its use for geotechnical monitoring purposes, and notes the advantage of the methodology in the detail of the obtained limit values ​​of deformation with an accuracy of one meter along the axis of the pipeline route. The authors studied the methods and designs used for monitoring deformations of underground pipelines and established the compatibility of using a complex methodology with any design and method of monitoring. The paper introduces the list of the main monitored parameters and justification for the scope of the geotechnical monitoring network for underground pipelines.

Keywords

• geotechnical monitoring
• underground pipeline
• permafrost soils
• complex methodology for pipeline calculation
• numerical modeling