Abstract:For landfill stability design,the 2-dimensional method is convenient and simple,but it does not consider the effects of the landfill's geometry that may contribute to an instability failure.In this study,for the first time,a 3D seismic stability analysis method for landfills under earthquake loading is proposed.This was achieved by dividing the landfill into two zones called the maximum horizontal and maximum vertical lengths along the liner itself and analyzing the overall slip failure along the liner system.The method is based on the assumptions as follows:(1)the entire landfill slip is along the liner system,(2)because of the restrictions of surrounding bedrock,the entrance of the landfill is considered to be the main slip direction,thus assuming that the angle between axis and the shear stress at the bottom of the landfill is fixed,(3)the friction between the lateral zone interfaces is ignored (4)pressure applied at the base is concentrated at the center of the bottom surface.Through the 3D stability analysis method,considering the effects of horizontal and vertical seismic coefficients,a factor of safety (Fs)is established.Based on this method,the relationships among the height to width ratio,shear strength of the liner system,horizontal seismic coefficient,vertical seismic coefficient,and Fs are studied and discussed.The height to width ratio and horizontal seismic coefficient are shown to have an important effect on Fs.In addition,when the horizontal seismic coefficient is fixed,Fs decreases with an increasing height to width ratio.With a height to width ratio between 1 and 10,Fs decreases faster.However,when the ratio is greater than 10,the rate of the decrease of Fs becomes smaller.When the ratio is greater than 1 000,the curve is nearly linear,and Fs can be considered unchanged.Although the height to width ratio is an important factor affecting the stability of the landfill,this effect is reduced when the horizontal seismic coefficient become large.Thus,during landfill stability analysis,the selection of an appropriate analysis method according to the specific geological environment is important.In addition,the horizontal seismic coefficient is an important factor that affects the stability of the landfill.When the height to width ratio is fixed,Fs of the landfill decreases continuously as the horizontal seismic coefficient gradually increases from 0 to 0.3.Compared with the horizontal seismic coefficient,the effect of the vertical seismic coefficient is small and can be neglected for stability analysis.By comparing the results from 2D and 3D seismic stability analyses,the 2D method is found to greatly underestimate the stability of the landfill,whereas the 3D method is found to be more realistic.The 2D method will accurately reflect the stability of the landfill only in the case of a large height to width ratio.The 3D seismic stability analysis method established in this study is a valuable tool for landfill design.
