Comparative Study On The Soil Response Analysis Methods On Deep Borehole Station Sites

The site conditions of the building location should be considered in the seismic design.The local site conditions are the influencing factors that can not be ignored in the propagation of ground motion.The main manifestation of ground motion is the amplification of ground motion in varying degrees,which will directly affect the severity of earthquake disasters.Therefore,the seismic response analysis of soil layer is an important part of seismic microzonation and site safety evaluation.The seismic response analysis methods of soil layer are mainly divided into two types,one is equivalent linearization method in frequency domain,the other is nonlinear calculation method in time domain,and different specific calculation methods are derived.At present,there are three frequency domain equivalent linearization methods.One is the traditional equivalent linearization method,and the commonly used software is SHAKE2000,referred to as SK method;The second is the equivalent linearization method with Chinese meaning of the first one to overcome a key problem),and the software named SOILQUAKE,which is called SQ method;The third is the holistic equivalent linearization approach,and the representative software is SOILRESPONSE,or SR method.The commonly used software of time domain nonlinear method is DEEPSOIL,which is called DP method.In this paper,the deep sites are defined as IV site with the thickness of overburden layer greater than 140 m,which is the difficulty of seismic response analysis at present.Based on the underground seismic records of all the deep sites currently owned by the Ki K-net strong earthquake observation network,this paper makes a comparative analysis of the existing methods,introduces the basic principles of the four representative methods,makes a comparative analysis of the surface peak acceleration,response spectrum and calibration spectrum obtained under the four methods based on the measured records,and gives a specific recommended method for practical engineering application.Finally,through the comparison of the distribution characteristics of the dynamic response along the depth,the causes of the differences of the four methods are explained.The main conclusions of this paper are as follows:1.For the surface peak acceleration,the calculated results of the four methods in grade 6 and 7 areas are close to the measured results and can be used.SR method is preferred in grade 8 areas.The calculation results of SQ and SR methods in grade 9areas are more consistent with the measured values.2.For acceleration response spectrum,SR,SQ and DP methods shall be given priority for grade 6 and 7 areas;SR performed well in grade 8 areas.In grade 9 areas,SQ and SR methods are the closest to the actual values.It can be used as recommended methods.3.For the platform height of the design response spectrum,the SR calculation result is the best.It is the recommended method,and the results obtained by SQ,SK and DP have little difference.4.For the characteristic period of the design response spectrum,SQ has the best calculation result,and it is the recommended method,followed by SR.DP and SK are not recommended above the grade 6 areas.5.For the peak accelerations of the four methods distributed along the depth,there is a large difference in the shallow surface,and the middle and deep parts are roughly the same.The dividing point is about 20 m deep in the soil layer.