IN SITU BOREHOLE MEASUREMENTS AND LABORATORY MEASUREMENTS AS PRIMARY TOOLS FOR THE ASSESSMENT OF THE SEISMIC SITE EFFECTS

摘要

Within the NATO Science for Peace Project 981882 "Site-effect analyses for the earthquake-endangered metropolis Bucharest, Romania" we obtain a unique, homogeneous dataset of seismic, soil-mechanic and elasto-dynamic parameters. Ten 50 m deep boreholes are drilled in the metropolitan area of Bucharest in order to obtain cores for dynamic tests and vertical seismic profiles for an updated microzonation map related to earthquake wave amplification. The boreholes are placed near former or existing seismic station sites to allow a direct comparison and calibration of the borehole data with actual seismological measurements. A database is assembled which contains P- and S-wave velocity, density, geotechnical parameters measured at rock samples and geological characteristics for each sedimentary layer. All the V_(s•3a) computed values belong to type C of soil after this classification (Romanian Code for the seismic design for buildings - P100-1/2006). Approximately 250 samples were gathered from the 10 drill sites. These samples were mostly not disturbed (samples as they were recovered from the tube of the drilling rig) and partly disturbed (those which had no proper consistency). Results obtained by the down-hole method in the 10 boreholes drilled in Bucharest City as well as from laboratory measurements will be used as input data in the program SHAKE2000 in order to obtain the seismic site effects due to the shallow soft layers.