SIMPLIFIED DESIGN METHODS FOR PIPELINES SUBJECT TO TRANSVERSE AND LONGITUDINAL SOIL MOVEMENTS

Pipelines are often subjected to transverse and longitudinal movements due to displacements in the ground caused by landslides. As landslide movements develop, pipelines can undergo transverse and longitudinal displacements and the resistance offered by the surrounding soil stead ily increases depending on the soil characteristics. This resistance r eaches an ultimate as the soil reaches failure and develops plastic st rains. Two simple analytical solutions have been developed based on th is concept: one for transverse movements and another for longitudinal movements. Nondimensional relationships have been developed and are pr esented in the form of charts. These charts permit hand calculations a nd rapid verification of structural design of the pipeline and, thus, assess the integrity of existing pipelines located in areas with groun d instability. A knowledge of the soil strength and subgrade modulus i s required along with pipeline geometry and pipe stiffness to apply th e nondimensional relationships. The soil parameters can be measured in situ or estimated using empirical correlations. Worked examples are g iven to illustrate the proposed methods and to show how various pipe f ailure criteria can be included.