VALUATION OF SEISMIC PERFORMANCE ON POLYETHYLENE PIPE INCLUDING JUNCTIONS AND BENDS DURING AN EARTHQUAKE

Abstract

 Evaluation of seismic performance on buried pipeline changes whether the pipe slips against the surrounding soil or not. When slippage takes place, stress and strain concentrate to junctions and bends. Important factors of slip or not-slip are critical shear stress of soil (τ_cr) and elasticity of pipe materials. Previous experiments by our group have shown that polyethylene pipe (HPPE) does not slip in the soft ground during severe earthquake. By contrast, HPPE slips a little in solid ground because of the short wavelength. In this study, we estimated the influence of slippage against junctions and bends. Our results are as follows: (1) τ_cr of HPPE with accessories including a coupler and branch saddle is 10.8kN/m² - 19.5kNm² because these accessories function as resistance in the soil. (2) Maximum slippage of HPPE is approximately 12.5mm in the solid soil. (3) we confirmed that there are no leakage from the branch saddle and the strain acting on the pipe with accesories and bends is enough small even in case HPPE slips. Through this study, the evaluation of seismic performance on polyethylene pipeline as the water pipeline were completed.