Eventos Anais de eventos
MECSOL 2022
8th International Symposium on Solid Mechanics
Evaluation of Lateral Soil Resistance of Buried Pipes by Limit Analysis Considering Friction at Pipe-Soil Interface
Submission Author:
Fabio da Costa Figueiredo , RJ
Co-Authors:
Fabio da Costa Figueiredo, Lavinia Maria Alves Borges, Luiz Felipe Vieira Moreira
Presenter: Fabio da Costa Figueiredo
doi://10.26678/ABCM.MECSOL2022.MSL22-0056
Abstract
Pipelines are vital means of transportation of liquids and gases over large geographical areas. Regarding hydrocarbons, they must be flow at high pressure and temperature to avoid wax formation. Low temperatures may lead to deposits at pipe walls, increasing the pressure or blocking the fluid flux. Under such thermal and mechanical loads, the pipe tends to expand longitudinally. Since these movements are restricted due to pipe supports, pipe-soil friction and the surrounding soil mass, high compressible forces are developed and it may lead to loss of stability and buckling may occur. If it occurs under controlled condition, it is a solution for stress and strain reliefs. On the other hand, uncontrolled buckling causes a sudden failure, bringing economical and environmental losses. The occurrence of lateral buckling strongly depends on the surrounding soil, friction at pipe-soil interface, pipe diameter and buried depth and subsoil characteristics. Then, the evaluation of soil lateral resistance that will entail an imminent breakout is important. This work aims the analysis of the soil lateral resistance under limit analysis theory considering friction at pipe-soil interface. Limit analysis is a direct method, posed as an optimization problem with constraints, and aims the determination of the collapse power of an elastic perfectly-plastic body without considering the load history. In this approach, the pipe is considered as a rigid body while the soil mass is a deformable one. Then, at imminent plastic collapse state, the contact between the rigid and deformable bodies is assumed as known, with permanent contact at normal direction and a slipping rule at tangential direction. Coulomb friction law is considered. The limit analysis problem is solved by a quasi-Newton algorithm and a condensation technique allied to Lemke algorithm is used to solve the complementarity problem at contact. The cohesive soil mass follows the Drucker-Prager yield criterion with an associative flux law. While most approaches consider a fully bonded or frictionless pipe-soil interface, the soil lateral resistance is evaluated by limit analysis considering friction at soil-pipe interface in this work. The soil mass is discretized by finite elements under plane strain hypothesis. As results, the soil resistance forces per length, the velocity and stress fields at soil mass are determined as well as the slip lines and its dependence with friction at pipe-soil interface and buried depth.
Keywords
limit analysis, Soil lateral resistance, friction, Pipe-soil interface
