Liquefied Soil Ground Motion Response Spectrum Analysis Method And Applied Research

The study on effects of liquefied zone on surface ground motion and seismic response of buildings is one of the very important subjects in the engineering of earthquake-resistance of structure. A modified two-dimensional dynamic effective stress method is established and also the corresponding program presented in the paper .And the method is used for analyzing the effects of liquefaction of sand soil zone on surface ground motion and the response spectrum of acceleration,velocity and displacement.The main achievements of the paper can be summarized as follows:1.The state-of-art of the research on the effective stress methods is conducted first. Then, the shortage of the research at present is discussed and some key points to be solved are pointed out2.A two-dimensional effective stress method is established and also the corresponding program(NDFEPS-2D)presented. The modified method has some obvious characters : more reasonable description of actual rise of pore water pressure under seismic loading ; calculates easily, may facilitate application in actual project.3.Blasting vibration monitoring was carried out in the project of the first blasting excavation issue in Quanzhou economic development zone headquarters square. And got the blasting earthquake wave. Then, the blasting earthquake wave,the natural earthquake wave and the artificial production earthquake wave are to be the input earthquake wave.4.The ground surface response spectrum of acceleration,velocity and displacement were calculated using NDFEPS-2D. And the effects of liquefaction sand soil on surface ground motion are investigated for considering the thickness,depth,width of the liquefied sand layer and the input earthquake wave. The obtained results indicate that compared with the clay layer, the liquefied sand layer takes a decreasing effects on the short period component of the surface ground motion and the effects increase with increasing of the thickness,depth and width of the liquefied sand layer; The liquefied sand layer takes a increasing effects on the long period component of the surface ground motion but the effect is not obviously ;To the input earthquake wave, the demarcation point of Strengthens and weaken is about 0.6s.5.On the basis of the results of the analysis in this paper, summing up the security measures to the liquefied zone: rational using liquefied sand layer and avoiding failure of foundation.6.Established blasting vibration hazard assessment methods on the basis of the response spectral theory, and applied to practical project. The results indicate that the assessment conclusion educed form the application of this method and application of the《Blasting Safety Regulations》(GB6722-2003) are consistent.