Liquefaction Analysis of Beach Protection Structure: Numerical Simulations

Abstract

The damage on infrastructures as well as environmental losses can be triggered by abrasion. That is why abrasion is included one kind of concerning disasters in Indonesia. West Sumatra is one of the provinces in Indonesia where its shoreline faces directly to the Indian Ocean. The West Sumatra shoreline abrasion phenomena have been recorded since earlier year 1900s. Abrasion prevention structures generally can be used to minimize the damage in near shore infrastructures. Cobblestone type groin is the most popular abrasion prevention structures to protect coastlines in the West Sumatra. West Sumatra groins were usually placed directly on the beach sand. The stability of the kind of groins is then greatly influenced by the mechanical state of the soil. Practically, the groins were designed in the static state which considers self-weight and the wave forces. In fact, due to dynamic forces the stability of the groins can be reduced. The external dynamic forces can increase in inertia forces and the change of the soil condition. Earthquake may lead the groins' base soil to liquefy which can disrupt the stability of the groins in terms of loss of bearing capacity. This study described the numerical simulation results to observe groin stability due to liquefaction. The liquefaction phenomena is simulated by increasing the applied pore pressure in the soil mass. The simulation results are then plotted in terms of shear-normal stress diagrams. The groin stability is then observed using the Mohr-Coulomb failure criterion. This study found that groin stability is not only disrupted by full liquefaction, but the liquefaction state can also disrupt the groin stability. It is also found that the groin dimensions affect the stability against a certain liquefaction level.