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Liquefaction Evaluation of Densified Sand at Approach to Pier 1 on Treasure Island, California, Using SASW Method.


pdf icon Liquefaction Evaluation of Densified Sand at Approach to Pier 1 on Treasure Island, California, Using SASW Method. (5165 K)
Andrus, R. D.; Stokoe, K. H., II; Chung, R. M.; Bay, J. A.

NISTIR 6230; 80 p. October 1998.

Available from:

National Technical Information Service

Keywords:

soil liquefaction; soil improvement; building technology; SASW test; seismic testing; shear wave velocity; surface waves; sand

Abstract:

Areas of improved and unimproved soil near berthing Pier 1 at Treasure Island, California, were investigated by the Spectral-Analysis-of-Surface-Waves (SASW) test. The upper 12 m of sand fill beneath the approach to the pier had been densified by a vibrating probe technique in 1985. The area of improved soil, which is 23 m wide and 93 m long, performed well during the 1989 Loma Prieta earthquake (Mw=7.0), while sinkholes, sand boils and cracks formed in the adjacent unimproved areas. SASW tests were conducted on a 240-m-long alignment that extended across the area of improved soil using a seismic vibrator as the principal source with receiver spacings from 7.6 m to 76 m. Average shear wave velocities determined for the densified and undensified sand fill below the water table were 192 m/s and 167 m/s, respectively. Two simplified analytical procedures based on shear wave velocity correctly predict no liquefaction for the densified sand, and marginal liquefaction for the undensified sand. Although less conservative, liquefaction assessment procedures based on the SPT and CPT provide similar predictions.