Study Of Evaluating Seismic Subsidence Of Loess By Shear Save Velocity And Water Content

Seismic subsidence of loess is a kind of earthquake disaster under seismic loading,which caused by a crash damage of large pore structure.Ground subsidence and loess landslides are the specific performances.In history,serious damages have been caused by seismic subsidence of loess in earthquakes to people's lives and property.Instance of earthquake has caused the people to the attention of the seismic subsidence of loess.The current method of evaluating seismic subsidence of loess is mainly laboratory test for the seismic subsidence coefficient of different depth,accumulating each of them to calculate the seismic subsidence amount.In this paper,on the basis of predecessors' research results,by analyzing a large number of shear wave velocity,water content and experimental date of seismic subsidence.A method was given by using shear wave velocity and water content jointly.Through these studies,the following several conclusions are made in this paper:1.Shear wave velocity and water content were selected to evaluate the seismic subsidence of loess.Analyzed the relationship between shear wave velocity and the seismic subsidence coefficient,and relationship between water content and the seismic subsidence coefficient.Under the condition of the same water content,the seismic subsidence coefficient decreases with the increase of shear wave velocity.In the same interval of shear wave velocity,the seismic subsidence coefficient increase with the increase of water content.And the trend becomes slow with the increase of water content.2.Analyzed the mutual relations between shear wave velocity and water content in the process of seismic subsidence.The author puts forward the concept of the absolute seismic subsidence coefficient.By analyzing the relationship between the seismic subsidence coefficient and the two parameters,it showed that shear wave velocity represents the characteristic of strength and the absolute strain of unsaturated loess,water content have great influence on the characteristic of strength and the release of the absolute strain.Based on the phenomenon,the concept of the absolute seismic subsidence was held,which reflects the potential ability of seismic subsidence.It has positive correlation with shear wave velocity.Water content has little influence on it,and has great influence on the process of seismic subsidence of loess.3.On the method of evaluating seismic subsidence of loess,two fitting formulas were given involve shear wave velocity,water content and seismic subsidence coefficient.the fitting formulas including shear wave velocity and water content will give different seismic subsidence coefficients,by comparing the two coefficients,the real seismic subsidence coefficients can be used to evaluating the characteristic of seismic subsidence.Under the guidance of this method,there are two kinds of condition: the one is when the seismic subsidence coefficient calculated by fitting formula of water content is less than the absolute seismic subsidence coefficient.The potential ability of seismic subsidence has not been fully released.The actual seismic subsidence coefficient is from by the fitting formula of water content.The other is when the seismic subsidence coefficient calculated by fitting formula of water content is greater than the absolute settlement coefficient.It means that the potential ability of seismic subsidence has been fully released,the actual seismic subsidence coefficient will be calculated by the fitting formula of shear wave velocity,the absolute settlement coefficient.4.Evaluating the seismic subsidence of loess in Lanzhou New Area by shear wave velocity and water content jointly,and compared with the results of laboratory test.The conclusion show that the prediction results are basically consistent.The research results of this paper provide a good idea for seismic subsidence of regional loess and has a large significance on engineering.