In Situ Seismic Investigation of Black Butte Dam.

摘要

Surface refraction, surface vibratory, downhole, and crosshole seismic tests were conducted. Compression-, shear-, and Rayleigh-wave (P-,S-, R-wave) velocities as a function of depth were determined for the dam and underlying foundation materials. Results of the investigation indicated that P-wave velocities in the dam's core exhibited values of 2150, 5050, and 3050 fps with increasing depth. The random-fill section indicated velocities of 1825 and 32225 fps. The foundation materials exhibited velocities of 1500, 4400, 6775, and 9850 fps; the first two foundation zones correlated with alluvium while the latter two were representative of the Black Butte Series and Chico Formation, respectively. Materials on the right abutment had velocities of 1225, 3500, and 9825 fps corresponding to slope wash, Tehama Formation, and basalt flows, respectively, while materials on the left abutment were determined to have velocities of 2375 and 8225 fps representative of slope wash and basalt, respectively. The S-wave velocity profile showed that the dam's core had velocities of 875, 650, and 975 fps with increasing depth. The random-fill section of the dam had velocities of 1100 and 1675 fps. Foundation materials had velocities of 675, 1350, and 1800 fps with the first two velocities representative of alluvium and the third velocity corresponding to the Black Butte Series. R-wave velocities on the right abutment ranged from about 640 to 1125 fps from near surface to a 37-ft depth.