The Soil Layers Seismic Response Analysis Of Xi'an Yanliang District

The seismic risk evaluation of somewhere actually answers the question that how much intensity earthquake a place might be encountered in 20, 50 or 100 years, which requires more accurate forecast of earthquakes that may happen in future. Currently, the basic framework of the probabilistic seismic hazard analysis method which is widely used in the field of earthquake engineering was raised by Cornell in 1968. After decades of theoretical study and practices, it has become the most popular probabilistic method applied in worldwide seismic hazard analysis and one-dimensional equivalent linear fluctuation method is recommended by China's"Project site seismic safety evaluation"(GB17741-2005).Earthquake damage investigations and meizoseismal records show that the ground overlying soil layers have important influence to ground motion amplitude, frequency and duration of the earthquake. In most cases, the surface soil layers can amplify seismic waves; but in some special circumstances, such as a strong surface supporting layer with weak layers below might weaken the waves. Therefore, the project site soil seismic response analysis is necessary. Different kinds of soil layers have different response to the seismic waves, so it is quite necessary to make soil layers seismic response analysis. Through soil layers seismic response analysis, we can calculate out the ground response be spread by soil layers under the same bedrock ground motion of different sites. By analyzing ground motions of different sites, we can distinguish ground seismic parameters of different sites, and then provide evidence for the determination of the design response spectrum.Xi'an Yanliang District is called"city of Chinese aircraft"although it isn't a large area with small population. It is an important aviation industry base of China. Once an earthquake happed, it will make huge losses to China's aviation industry. So seismic intensity and ground motion parameters of this area should be given out by seismic activity and seismic geological environment analysis. A lot of works need to do, such as seismic hazard analysis, seismic intensity review, the determination of design ground motion parameters, small earthquake division, seismic geological stability evaluation of this area and approach regions, seismic damage prediction. This paper mainly involves the part of layer seismic response analysis.The ground geological survey mainly focused on Yanliang area and it's surround region. It is about 40 km2 which is 1 km extension of the site. The survey mainly about landforms, surface rock characters, surface structures overview. 19 drill holes were set on the basis of geological work collections, and the total footage is 1718.0m.. We collected 8 drill holes'data, and 2 holes'data could be used. We completed drilling velocity test 1683.0m in 10 holes, and 116 group soil samples'dynamical parameters test were completed in all 521 group soil samples. Indoor soil test includes solum conventional physical and mechanical tests and soil dynamical parameters tests. 5 pulsated test points were set to get dominating periods. These tests provided necessary data for seismic risk analysis.Bedrock peak acceleration and response spectra, which are the result of seismic risk analysis, will be the objective function to composite ground motion. Trigonometric series superposition method was used to composite bedrock ground motion acceleration time periods. 3 independent earthquake time periods were synthesized for each 63%, 10% and 2% probability of exceedance in 50 years.This paper makes soil layers seismic response analysis of Xi'an Yanliang area with one-dimensional equivalent linear method. One-dimensional models of every point are built, and then gives out comprehensive parameters of ground motion and the surface horizontal acceleration comprehensive design response spectrum under 3 kinds of probability of exceedances in 50 years.Xi'an Yanliang district's seismic fortification intensity is 8(by China ground motion parameters zoning map), which is equal to the calculation result. The results can be used in design of earthquake engineering in this area and have important practiceal meaning.