Seismic Behavior of Gravel Drains and Compacted Sand Piles using Physical and Numerical Models
Department. of Civil & Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, USA
During recent earthquakes, it was observed that liquefaction can cause severe damages to buildings in the form of significant subsidence and shear failure of foundation soil. This damages is known to be due to the build up of pore water pressure and hence a reduction of soil strength. A number of remediation methods exist which reduce the excess pore pressure, enhance the shear deformability of the soil and fortify the soil. Two well known methods which are gravel drains and compacted sand piles are discussed and compared in this paper. Some precisely prepared 1-g shaking table tests were performed regarding these methods. The results show that compacted sand piles were more efficient than gravel drains in the case of liquefaction resistance and settlement of the subsoil during the shaking period. On the other hand after shaking the efficiency of the gravel drains was improved by the means of excess pore pressure dissipation. Also the cases were modeled with a numerical finite element program which could only handle the excess pore water pressure. By evaluating the numerical results with the experimental ones it is concluded that replicating liquefaction merely by an excess pore pressure generation/dissipation model would underestimated the excess pore pressure as well as the settlement.
Keywords: Gravel Drains, Compacted Sand Pile, Liquefaction, Shaking Table, Excess Pore Water Pressure, Numerical Modeling.
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