Site Classification Method Based On Topographical And Geological Characteristics In China

The impact of site effect on earthquake damage has been a hot topic in recent decades.The post-earthquake disaster investigation shows that in the same earthquake,the damage at different sites with similar focal distance is significantly different.It is found that the earthquake damage on soft site is always more serious than that on hard site.Therefore,it is very important to classify the site for the earthquake resistance of engineering.The classification using borehole wave velocity data is the most direct and effective way,but it is difficult to realize the classification of the regional site.In this paper,the open topographic and geological data are used to investigate the correlation between them and borehole wave velocity data,and establish a practical and effective regional site classification method.1.The borehole profile data of more than thousands engineering sites in Sichuan Province,Hebei Province,Shaanxi Province and Xinjiang autonomous region are collected,the average shear wave velocity of 30 meters near the surface(V_S30)at each site was calculated,and the constant extrapolation method and boore?2004?linear logarithm extrapolation method were used to extrapolate the data of drilling depth less than 30 m.Based on the open global 30 arc second DEM data,the slope values of the four regions are calculated,and the relationship matrix between the terrain slope and the site classification based on the American and Chinese codes is established respectively,and the site classification map of China based on the American and Chinese codes is given.After analyzing the classification results,it is found that the classification method based on slope is not suitable for the special sedimentary characteristics in Sichuan.Finally,using the DEM data of 3 arc seconds and 9 arc seconds to investigate the sensitivity of slope-based classification method,it is found that DEM data with 30 arc secondsis the most suitable for this method.2.Aiming at the problem that the classification method based on slope is not applicable in Sichuan,a terrain-based site classification method is developed,which is including terrain slope,surface texture and local convexity.Based on Xinjiang 30 DEM data,the whole region is divided into 16 categories according to the terrain characteristics and the the simple decision tree theory.The V_S30empirical estimation model is established by cross validation method,and the site in Xinjiang are classified.Comparing with slope-based mathod,it is found that the accuracy of classification is improved by introducing surface texture and local convexity than by using single feature of terrain slope.Finally,the site classification map of Sichuan area is given by this method.3.Using the large-scale geological map data,the relationship matrix of geological age and genesis and the site classification based on American codess are established.Compared with the results of Wills,the new relationship is more suitable for China.Using two different site classification methods of comprehensive topography and geology,and the classification process is given.Taking Xinjiang data as an example,it is verified that the comprehensive method improves the classification accuracy compared with the method using single terrain or geological data.