THE UPLİFTİNG BEHAVİOR OF SHALLOW BURİED PİPELİNES WİTHİN THE LİQUEfiABLE SOİLS UNDER CYCLİC LOADİNGS

The liquefaction of soils under earthquake loadings has 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 decreases sharply, and large deformations happen in the area. 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 and also underground structures may be severely damaged. Pipelines 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 soil dilatancy angle, soil friction angle, 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. Results show the prominent role of friction angle of soil, diameter of pipe and exist an optimum level for burial depth in pipe response reduced floatation.

Keywords:

Baseline , Liquefaction , Buried Pipelines , Finite Difference Method , Flac- 2D , Finne Model.