Vulnerability of Baghdad Soil to Liquefaction (Numerical Study)

A phenomenon known as "earthquake liquefaction" or "soil liquefaction" occurs when a mass of saturated soil gradually loses strength as a result of increased excess pore water pressure generated by ground shaking during a strong earthquake. In other words, the state condition of soil liquefaction is when the soil's effective stress momentarily drops to zero. Iraq's capital is Baghdad, located in a moderately seismically active area. The soil layers for Baghdad city bear silty, a shallow sand layer and the groundwater level exists. This study investigates if Baghdad soil may be liquefied by studying the factors on which the liquefaction phenomenon depends. The factors as relative density (DR= 30, 50, 75 and 85 %), shear modulus (G0= 35, 65, 85, 95 and 125) MPa, shrinkage rate coefficient (hp0 from 0.1 to 8), surface modulus, (nb from 0.2 to 5) and critical state line coefficient (R from 1.5 to 5) have been changed based on the Halabja earthquake. The study was analyzed by PLAXIS 2D, and the PM4Sand model was chosen for the liquefiable layer to evaluate the possibility of liquefaction and investigate the impact of the earthquake intensity and its duration on the occurrence of the liquefaction. The properties of the soil stratification were chosen from available data for 200 boreholes, and 630 tested samples were selected from all Baghdad regions, which normalized the physical and engineering properties data.