Analysis Of Influence On The Amplification Coefficient Of The Site With Weak Interlayer By The Factors

The weak interlayer is still not taken into consideration in the items of the current seismic code about site classification although it is common in the site soil formation. Researching the seismic response of the site with weak interlayer has a great significance because it is in favor of reducing investment and the sustainable development of society to consider the isolation and damping effect of the weak interlayer during seismic design.The merits and faults of the equivalent linear method, which is still the universal way for soil layer seismic response analysis until now, are presented in this paper as well as the basic principles of it. Meanwhile, the relevant earthquake ground motions of the site are calculated when changing the input motion, the thickness and location of the weak interlayer to acquire a relationship curve between the amplification coefficient of peak acceleration and the corresponding different effect factors by using EERA-a computer program for equivalent linear seismic response analysis. According to the curves, the paper summarizes the influence law of the factors on the amplification coefficient and analyzes the reasons briefly.It is presented that the intensity and spectral characteristics of input motion, the thickness and buried depth location of the weak interlayer have a great overall interaction with the amplification coefficient of peak acceleration in addition to the correlation between these factors. This paper draws a regular conclusion that the amplification coefficient keeps decreasing, at last remains unchanged following the increase of intensity and buried depth with the critical values affected by other factors. However, in the range of 2 to 20 meters, the amplification coefficient fluctuates differently-first goes up, then down, at last up again with the increasing of the thickness for the possible reason that the predominant period of the site gets close to the main seismic wave period within certain range of thickness, which affected by the intensity and location.