Research On The Influence Of Stratum Mining On The Mechanical Behavior Of Buried Pipelines

In recent years,great progress has been made in the exploration and development of national oil and gas resources.As the most important transportation method for oil and gas resources,pipelines have received widespread attention for their structural safety and operational reliability.Because buried pipelines are in direct contact with the soil,they are affected by geological disasters.The complex and changeable geological environment is likely to cause large deformation or even failure of the pipeline and cause accidents.It not only causes serious economic losses,but also causes damage to the ecological environment.Among them,the effect of mining subsidence areas on buried pipelines has become increasingly prominent.Therefore,this paper establishes a numerical model for buried pipelines in subsidence areas,and studies the mechanical properties and deformation mechanism of buried pipelines in mining subsidence areas.The research results provide a theoretical reference for the application of buried pipelines such as laying design,safety evaluation,maintenance and protection.Based on elastic-plastic mechanics,elastic foundation beam theory,soil mechanics and finite element theory,this paper establishes a three-dimensional pipe-soil coupling numerical model in stratum settlement area,stratum subsidence area and suspended pipeline.A systematic study of the mechanical behavior of buried pipelines in mining subsidence areas was carried out including the following aspects:(1)Analyzed the theoretical model of buried pipeline's deformation,verify and establish a numerical calculation model of buried pipeline in stratum settlement area through elastic foundation beam theory.The materials and contact characteristics of the pipe-soil were selected reasonably,the deformation law of the pipeline after mining was analyzed,and the effect of different factors(pipeline parameters,mining area parameters,mining zone orientation,and mining area inclination)on the pipeline's deformation was studied.(2)Subsidence may occur in the settlement area after mining.Therefore,a numerical calculation model for the pipeline in the stratum subsidence area is established,the stress and strain response of the pipeline after mining is studied.The effect of different parameters(pipeline parameters,soil parameters)on the strain and cross-sectional shape of the pipeline was explored.(3)After the stratum subsidence in the mining area,the pipeline will be suspended.Therefore,the deformation law of the suspended pipeline is studied based on a numerical model.The effects of suspended length,pipeline diameter,wall thickness,internal pressure,internal fluid gravity,and soil on the stress and strain of the pipeline were analyzed.(4)Based on the three working conditions(stratum settlement,stratum subsidence,suspend pipeline)in the mining area,the stress and strain of the curvature pipe are analyzed in detail.The effects of curvature and subsidence area conditions on the deformation of pipeline are discussed.