Study On Seismic Design Method For Compound Supporting Structure Of High-steep Slope In Earthquake Area

The geographical position of our country lies between the circum-pacific seismic belt and the Eurasian seismic zone, so it is an earthquake-prone country. Earthquakes have brought great life and property losses to our country, but they also have left a lot of valuable real seismic materials to us. During the earthquake damage investigation on the supporting structures in Wenchuan earthquake, it was found that damages of different degrees occurred in the high slope retaining walls in high earthquake intensity regions, which lead to rockfall off the road and road embankment collapse. In the event of an earthquake, the normal use of the lifeline of roads and railways would be affected and the smooth progress of the rescue and relief would be impeded. Therefore, the research on the supporting of high-steep slope in seismic area is of great engineering significance.This paper combined with the development plan project of "Earthquake-proofing Technique Research on Special Supporting Engineering of High-Steep Slope"(2008G028-D) proposed by department of railway ministry science and technology, and took the slope supporting structure of Dali-Ruili railway line which is still under construction as engineering background. By the earthquake damage investigation on the supporting structures in the5.12Wenchuan earthquake, this paper aimed at experiment research on the seismic behavior of the supporting structures. Some kinds of compound supporting structures which are applicable to the high intensity and high-steep slope have been refined and a reasonable and reliable seismic design method has also been proposed for guiding the design of supporting structures along the railway line.The research contents of this paper are as follows:1. According to the survey and reconnaissance of the earthquake damage of the supporting system of roads and railways in seismic area, a typical compound supporting structure was refined and was adopted as the supporting system of the high-steep slope in seismic area. The frame structure of anchor cable was adopted in the upper part while the sheet pile wall was designed as the lower part of this compound supporting structure.2. On the basis of analysing and summarizing related supporting structure seismic design methods in seismic design codes home and abroad, the gaps and shortages were found in seismic design codes in our country.3. According to the large-scale shaking table model test results analysis of this refined compound supporting structure, it has been proposed for the aseismatic design of prototype slope along Dali-Ruili railway line:(1) In the seismic design of the sheet pile wall, it adopted the seismic design code now in low intensity seismic area, but it was necessary to revise the amplified coefficient of the horizontal seismic load along the wall height in the code before calculating its inner force in high intensity seismic area.(2) In the seismic design of the frame beam of anchor cable, three methods could be used to calculate its inner force, including the elastic foundation frame structure finite difference method, the elastic foundation frame structure simplified method and the continuous beam method on rigid support. A most reasonable design method was refined among all these methods.