H. Tosun et R. Ulusay, ENGINEERING GEOLOGICAL CHARACTERIZATION AND EVALUATION OF LIQUEFACTION SUSCEPTIBILITY OF FOUNDATION SOILS AT A DAM SITE, SOUTHWEST TURKEY, ENVIRONMENTAL & ENGINEERING GEOSCIENCE, 3(3), 1997, pp. 389-409
Osmankalfalar Dam was planned to be built in the Mediterranean region
of Turkey. The 29.5 m high-zoned embankment dam will be founded on all
uvial deposits consisting of four soil zones. Under the ongoing dam si
te investigation stage a preliminary program of field and laboratory i
nvestigations was completed in 1995 to characterize soil properties an
d to evaluate the potential for liquefaction of the foundation soils d
uring an earthquake. The results of both field and laboratory investig
ations that were used to assess the ground conditions, with particular
reference to the liquefaction susceptibility-at the proposed dam site
, is presented. Considering the limitations in SPT blow-count and fine
s content, 51 layers were examined. From these, 17 layers through thre
e boreholes along the centerline of the dam were considered for liquef
action assessment. Based on the seismic records available for the site
vicinity, a scenario earthquake of M7.5, taking place 40 to 60 km fro
m the site, was used in the analyses. Ground-motion attenuation relati
onships yield a(max) values between 0.12 g and 0.18 g, Two SPT-based m
ethods were evaluated and the results derived from these were compared
to those obtained from laboratory cyclic triaxial tests performed on
tube samples from trial pits. The methods revealed that silty fine-to-
medium sand layers between the depths of 8 and 15 m in zone B would be
susceptible and marginally susceptible to liquefaction as a consequen
ce of event two (a(max) = 0.18 g) during the operational stage of the
dam. Necessary future investigations and possible remedial measures to
increase liquefaction resistance of the foundation soils were recomme
nded.