Analysis Of Seismic Damage Mechanism And Aseismic Design Standards Of The Shoulder Retaining Wall In The Wenchuan Seismic Area

On 12 May 2008, at 2:28 in the afternoon, a magnitude 8 earthquake struck Wenchan county Sichuan province in China. The high magnitude, frequent aftershocks, long surface rupture zone and serious secondary mountain disaster were rare for the word. After the destructive earthquake occurred, the codes were revised according to the damage features. This is the usual practice. In 5.12 Wenchuan earthquake high seismic regions, the seismic damage data of roadbed engineering provided rare conditions for researching the seismic technique of roadbed engineering in high seismic regions. Promoting highway and railway aseismic design codes development by utilizing mass seismic data in Wenchuan earthquake near field area had great scientific value and practical significance, and it also had important timeliness.Based on the seismic damage investigation of the G213 Highway shoulder retaining wall, the seismic damage mechanism of the shoulder retaining wall in the Wenchuan Seismic Area was analyzed. Than the current highway and railway aseismic design standards of the retaining wall were discussed and researched. Conclusions obtained, to promote the current highway and railway aseismic design codes revise and development, had a certain reference value and practical significance. The major research results were as follows.(1) Firstly, because the relevant regulation in the current highway codes showed that the vehicle load wasn't considered when checking the seismic stability of the highway retaining wall, the retaining wall designed according to the current highway codes could resist the 8 magnitude earthquake. Secondly, the reason of the shoulder wall's incline distortion in 9 degree earthquake zone was the foundation stress went beyond the bearing capacity. The reason of the shoulder wall's serious incline distortion and collapse in 10 degree earthquake zone was that the toppling stability coefficient didn't satisfy requirements of the codes and the foundation stress went beyond the bearing capacity. Lastly, the theory system of the stability safety factors, mainly used in the current roadbed engineering, was reasonable. The stability safety factors value was reasonable, and it was applicable in 9 degree earthquake intensity zone and could be extended to 10 degree earthquake intensity zone.(2) The relevant regulation in the current railway codes showed that the train load was considered when checking the seismic stability of the railway retaining wall. The retaining wall designed according to the current railway codes could resist the 7 magnitude earthquake, and its seismic stability should be checked in 8 degree earthquake zone and above. The current railway codes showed that the general retaining wall's seismic stability wasn't checked in 7 degree earthquake zone, and should be checked in 8 degree earthquake zone and above. So this conclusion above corresponded to the current railway codes. It could be seen that the seismic design standards of the retaining wall in the current railway codes were reasonable. On this condition that the train load wasn't considered when checking the seismic stability, the retaining wall designed according to the current railway codes could resist the 8 magnitude earthquake, and this conclusion was identical with the highway retaining wall.(3) Using sloping base and tenon could significantly improve the anti-sliding performance of the retaining wall, but had little influence on the resistive overturn performance and the foundation stress. Expanding the wall toe could significantly reduce the foundation stress and increase the resistive overturn performance effectively, but had little influence on the anti-sliding performance. While the embedment length of the retaining wall was big to some extent, the passive earth pressure in front of the wall, caused by the length of embedment, had more beneficial effects on the wall's seismic stability. So the passive earth pressure in front of the wall couldn't be ignored. Thus, it is suggested that, in high-intensity seismic regions, could consider increasing the wall's embedment length to some extent to improve the wall's seismic stability. The gravity shoulder retaining wall with relieving platform had the biggest anti-sliding safety factor. Because of the low gravity, the vertical shoulder retaining wall had the biggest resistive overturn safety factor under earthquake action.