Seismic simulation of liquefaction-induced uplift behavior of buried pipelines in shallow ground

Abstract

Damages of underground structure buried in liquefiable soils under earthquake loadings have always been a main concern for geotechnical engineering practices. As an earthquake causes the ground to liquefy, the effective stress and hence the shear strength of the soil decrease sharply and large deformations happen in the area. Of course, this phenomenon occurs only rarely when the liquefaction occurs at a large depth. However, deformations increase extensively when this layer is located in shallow depths near the ground level. In this case, super structures as tunnels and also underground structures may be severely damaged. Pipelines and manholes buried in saturated sand deposits, during earthquake loading, could damage from resulting uplift due to excess pore water pressure generation. Especially for previously buried pipelines, in order to set the priority for seismic retrofit, evaluating the risk of floatation in each region could be a concern. In this paper, effects of several parameters including dilatancy and friction angle of soil, density ratio of natural soil, diameter and burial depth of pipe on uplift of pipe by construct, an advanced soil pipe model in FLAC 2D software, and Finn behavior model under cyclic loading have been investigated. The results show that soil parameters such as friction angle, pipe diameter and optimal depth of buried pipes have a significant impact in reducing the buoyancy force.