| Yintao First-stage Project is the largest large-scale inter basin water transfer project in the history of Gansu province, its construction accelerates the general policy of the western development,which is of great significance and makes the tremendous contribution for the development of the central region of the economic development in Gansu province. As most of its diversion tunnel and culvert works through the loess area, so the seismic stability under its self-weight become difficult in the analysis of the loess tunnel, and this paper takes one of Yintao Project loess tunnel as an example and bases on the relationship between the Q3 loess’ s initial elasticity modulus and the moisture content, the loess tunnel in different water content under the condition of static and seismic loads by using the method of numerical analysis. This paper’s research is mainly from the following six aspects.1、Based on reading a lot of literature and comprehensive analysis of Yintao issue of engineering geological exploration data and the engineering geological conditions of the Yintao Project loess tunnel, combined with given in the literature of loess moistening parameters and studied on geological background of Yintao First-stage Project main channel of loess tunnel engineering area, geological structure, characteristics of loess tunnel and engineering geological parameters. Combine all above can reach the parameters that suit for the model.2、The paper has established the same kind of horseshoe cross section model of tunnel with practical engineering. So the tunnel is far greater than the longitudinal cross-sectional width that it was analyzed and calculated with the two-dimensional plane strain model, the analysis of the Loess geological parameters suitable for the model to analysis model.3、Based on the relationship of the loess water content with the elastic modulus and shear strength, using the method of earthquake acceleration time history analysis, dynamic analysis of the established model. Under the action of 7 degree and 8 degree earthquake load, the simulation of the Loess Tunnel under the traditional artificial boundary with the seismic load acting on the surrounding rock of the Loess Tunnel under the earthquake load is carried out. The results are listed below. With the increase of the water content, theabsolute value of main stress of each part of the tunnel lining decreased, so did the natural circular frequency, and self-vibration period had an opposite result. Compared with the peak earthquake acceleration of the original input, when the water content is smaller than the critical moisture content, the tunnel peak acceleration is bigger than the original seismic peak acceleration, otherwise, it had an opposite result; It is the main reason for failure of the tunnel lining when the tunnel lining symmetric part of maximum, minimum principal stress appear alternately, so the tunnel lining material fatigue damage occurs under the same water content, and compared 7 degree’s Critical water content with 8degree’s, it shows almost the same result.4、It was tested in 7 degree and 8 degree earthquake loads for the Loess Tunnel output peak acceleration of correspondence analysis, which was gotten the constant critical moisture content, the verification of the peak acceleration and the output of the original input earthquake peak acceleration values are the same, it was tested under the load of 7degrees and 8 degrees earthquake in the Loess Tunnel moistening the critical moisture content data is reasonable.5、The analysis of the loess tunnel lining in weak position and line selection, tunnel import and export(especially in shallow buried tunnel),which was easily liquefied soil layer can make the Loess Tunnel damage condition. In order to reduce the possibility of the occurrence of the Loess tunnel under seismic load under the action of the disaster, it is necessary to put forward the rationalization of the seismic measures. |
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