Performance of a reinforced soil retaining wall during the Christchurch earthquakes

摘要

This paper presents a case study of a reinforced soil retaining wall built in the centre of Christchurch inrn1991. The wall has a maximum overall retained height of about 3.4m, consisting of a full height precastrnconcrete panel facing with HDPE punched and drawn geogrid attached by casting in duringrnfabrication, and reinforcing a granular backfill material. The wall forms one bank of the River Avonrnover a 50m length, so that the foundation is situated below river level, and it supports a busy mainrnroad and a bus stop. The wall was designed originally by the tie-back wedge method. During thernstrong earthquakes which shook Christchurch severely during 2010 and 2011, together with manyrnaftershocks, the wall was subjected to intense shaking. Many structures in the area were damaged byrnthis seismic activity, but the reinforced soil retaining wall performed extremely well, with neither signsrnof distress to the wall itself nor to the supported road. This paper gives full details of the wall asrndesigned, summarises the seismic shaking which took place and presents a back-analysis using therntwo-part wedge method of analysis, which is being used widely today to design such structures, forrnboth static and seismic conditions. The analysis takes into account peak ground accelerations whichrnare likely to have been experienced in this part of Christchurch during the earthquakes.