Here - Stuff

methodology in Youd et al. (2001) and as outlined previously.Comparisons of the CRR 7.5 and CSR 7.5 for the Darfield andChristchurch earthquakes are presented in Figures 9B and 9Dfor the SASW and DCP tests, respectively.As may be observed from Figure 9B (V s data), liquefactionis predicted to have occurred from ~1.75 to ~6 m during boththe Darfield and Christchurch earthquakes, with the factorof safety against liquefaction being slightly lower during theChristchurch event. Similar trends are predicted in Figure 9D(DCPT data), but liquefaction is predicted to have occurredduring both earthquakes in a slightly thinner layer, ~2.5 to~3.25 m. These predictions are consistent with field observations(i.e., liquefaction occurred at the site during both earthquakes,with the liquefaction being more severe during theChristchurch earthquake).Avondale Road BridgeAvondale Road Bridge (Figure 4D) was constructed in 1962,runs approximately in the north-south direction, and spansthe Avon River (Figure 2). The bridge consists of three spans ofprecast reinforced concrete girders that are supported on twothree-column bents and seat-type abutment walls with wingwalls.Since its construction, the bridge has been seismicallyretrofitted using steel brackets, which are bolted to tie the elementsof the bridge together.The bridge was not damaged during the Darfield earthquake,with the region north of the bridge showing no signs ofliquefaction damage. However, just south of the bridge, alongthe inner bank of the river, there were minor to moderate levelsof liquefaction ejecta, with the volume increasing toward thesouthwest. Liquefaction and lateral spreading were more severeduring the Christchurch earthquake, with larger volumes ofejecta and significant lateral spreading adjacent to both sidesof the south abutment. To the north, there was also increasedvolume of ejecta, and moderate spreading 30 m to the west.There was minimal roadway damage adjacent to the northabutment; however the north abutment back-rotated approximately3°. At the south, the abutment has back-rotated 7°, withmoderate settlement of the approach and damage to roadwayand services (Figure 10C). Large lateral spreading cracksextended out from both sides of the abutment, transitioningfrom perpendicular to the riverbanks to parallel over a distanceof approximately 15 m. The superstructure and piers showed nosigns of damage after either earthquake.A cone penetration test (CPT) was performed after theDarfield earthquake, approximately 15 m to the west of thesouth abutment, with the results shown in Figure 10A (Tonkinand Taylor 2011a). The CRR 7.5 profile for the site was determinedusing the CPT data, per Youd et al. (2001). Using thePGAs listed in Table 1, the cyclic stress ratios (CSRs) for boththe Darfield and Christchurch earthquakes were calculatedfollowing the methodology outlined in Youd et al. (2001).Comparisons of the CRR 7.5 and CSR 7.5 for the Darfield andChristchurch earthquakes are presented in Figure 10B. As maybe observed from this figure, the site is predicted to marginallyliquefy during the Darfield earthquake, with the severity(A)(C)(B)▲▲Figure 10. Avondale Road Bridge field investigation: A) CPTprofile; B) liquefaction assessment using CPT data, comparingthe cyclic resistance ratio CRR 7.5 to the Darfield (CSR 7.5 DAR)and Christchurch (CSR 7.5 CHC) cyclic resistance ratio; C) damageto southern abutment and approach.of the liquefaction increased for the Christchurch earthquake.These predictions are consistent with field observations (i.e.,liquefaction occurred at the site during both earthquakes, withthe liquefaction being more severe during the Christchurchearthquake).Gayhurst Road BridgeGayhurst Road Bridge was constructed in 1954, runs inapproximately the north-south direction, and spans the AvonRiver (Figure 2). This integral bridge, shown in Figure 4E, consistsof three-spans of precast reinforced concrete girders supportedby wall piers that were cast in place within the deck andseat-type concrete abutments with wingwalls. Both the piersand the abutments are founded on reinforced concrete piles.Prior to the earthquakes, both approaches were approximatelylevel with the bridge deck as part of the natural level of the riverbanks.Severe liquefaction occurred during the Darfield earthquake,indicated by the significant volume of ejecta to the north958 Seismological Research Letters Volume 82, Number 6 November/December 2011