Issue 8

A. Namdar, Frattura ed Integrità Strutturale, 8 (2009) 21-29; DOI: 10.3221/IGF-ESIS.08.02 21 Evaluation of seismic mitigation of embankment model Abdoullah Namdar Mysore University, Mysore 570006, India, sina_a_n@yahoo.com A BSTRACT . Conducting experiment on embankment model by shaking table could be an accurate method to evaluate the behavior of embankment or any structures under seismic loading. In this research work, in order to assess the function of seismic force and accurate placement of dense zone in the embankment model, the results of three experiments have been considered. To evaluate the reaction of the embankment model, it was measured the stress in the system and photographs were taken. The results of three experiments indicated that suitable arrangement of dense zone is the main factor at the play in embankment stability, and in predicting the possibility of embankment behavior. K EYWORDS . Liquefaction, Stress, Dense Zone, Pore Water Pressure I NTRODUCTION eismic liquefaction refers to a sudden loss in stiffness and strength of soil as a result of cyclic loading effects of an earthquake. This loss arises from the soil tendency to contract under cyclic loading. If such contraction is prevented or curtailed by the presence of entrapped water in the pores, it leads to a rise in pore water pressure and a resulting decrease in effective stress. If the effective stress drops to zero (100 per cent pore water pressure rise), the strength and stiffness also drop to zero and the soil behaves as a heavy liquid [1] . At the time of the earthquake, the embankment rested on saturated loose sandy subsoil faces high level of liquefaction risk and may bridge to failure of the embankment. Seismic force creates liquefaction due to nonlinear stress up on the model. Constructing dense zone in the subsoil is a method to reduce the effect of stress in the embankment model [2] . A research work on Dynamic properties and liquefaction potential of soils has been presented [3]. Jack W. Baker and Michael H. Faber [4]c onducted a research by using Random-field theory and geostatistics tools to model soil properties and earthquake shaking intensity. He wanted to present a potential extent of liquefaction by accounting spatial dependence of soil properties and potential future earthquake shaking. Dash et al. investigated the use of reinforcement in increasing stability of soil foundation [5] . Schimizu and Inui [6] carried out load tests on a single six-sided cell of geo-textile wall buried in the subsurface of the soft ground and also Mandal and Manjunath [7] used geo-grid and bamboo sticks as vertical reinforcement elements and studied their effect on the soil bearing capacity. Rajagopal et al. [8] have studied the strength of confined sand and the influence of geo-cell confinement on the strength and stiffness behavior of granular soils. Seismic motion could be responsible for instability of embankment model. It is possible to control seismic motion by provision of a dense zone in the subsoil as a feasible method. Embankment with good enough foundation stability could be more resistant against seismic force and could increases the safety factor in the system. M ETHODOLOGY AND EXPERIMENTS he evaluation of embankment model behavior, when it is under seismic force by manual-shaking table, provided insight in understanding seismic mitigation of embankment. The dense zone, consisted of composite material confined in geo-textile in loose saturated sandy subsoil, was studied to assess disability of liquefaction. The manual-shaking table was used to vibrate in one direction Figs. 1-3. It consisted of two wooden panels with a steel plate in between which produced harmonic vibration at frequency of 1 Hz to 3 Hz when an approximately around 75Kg force S T