Study On Seismic Performance Of Highway Subgrade

ABSTRACT:China is an earthquake-prone country decided by the global plate tectonic and dynamic condition, subgrade is the most common structure of highway, once subjected to the earthquake the damage is universal. The study target of doing subgrade structure model testing by shaking table is to profound understand the law of its dynamic response, the process of dynamic failure, the influence of the ground motion parameters and examine theory analysis result whether or not right. By contrast with the disaster of subgrades in wenchuan earthquake, then sum up the damage characteristics and find the weak points of subgrade structure. It is basic support for subgrade seismic design that on these achievement. It is the first time to take subgrade structure model testing by large scale shaking table in china.Firstly, This paper analyse and summarize the present situation of shaking table model test as well as the earthquake damage assessment on subgrade, and this play a very good reference for the shaking table model test in this research. At the same time, the paper generalize the damage forms and damage features of subgrade structures according to wenchuan seismic event in which some subgrade structures are destroyed. Earthquake damage indicates that, the subgrade structure under certain conditions may cause serious damage, should cause the attention of earthquake resistance and disaster mitigation of subgrade structure. And representative survey study is taken about structure earthquake resistance and shaking table test aiming to supply reference for the test study.Secondly, the technical problems of shaking table test are studied based on previous research, including the shaking table model box selection, the treatment of boundary conditions and the model soil dynamic characteristics. Depending on a set of similarity law of large-scale shaking takbe model test we deduced and the test results, we choose the model material as well as the corresponding ratio. According to the test requirements and purpose, design the measurement method of the dynamic acceleration and displacement response, select the corresponding sensor and data acquisition system, and determine the model construction method and loading scheme of the shaking table test.On the basis of above study chievements, the preparations for the subgrade shaking table test model with and without retaining structure are finished, and the modle test is realized smoothly considering the input earthquake wave type, intensity, frequency and multi-direction input. we use the finite difference program to simulate the shaking table test at the same time, so as to prove the rationality of the numerical analysis model.Finally, based on the shaking table test results and the numerical analysis results, some knowledge of subgrade model dynamic response is achieved which including the acceleration magnification and displacement response and dynamic soil pressure on retaining wall and other aspecets of the analysis. During the test process, the subgrade model showed some earthquake resistance, both the acceleration magnification and displacement response reach the peak on the top of the subgrade and the top of the retaining wall, this law is similar to the subgrade seismic damage performance in wenchuan earthquake. So that more emphasis should be given to the top of the subgrade and the top of the retaining wall.