Searsville
Dam is a 68-foot high curved concrete gravity dam with a central
overflow section. Located in San Mateo County, California, the
dam impounds San Francisquito Creek by forming a 952 acre-feet
reservoir. Built of interlocking cast-in-place concrete blocks
in 1890, the dam survived the 1906 San Francisco Earthquake which
occurred on the San Andreas fault located only 3,000 feet west
of the dam.
Three-dimensional
linear and nonlinear finite-element analyses were performed to
assess safety of the dam. The seismic inputs included two sets
of three-component acceleration time histories associated with
a maximum credible earthquake magnitude of 7.8 occurring on the
San Andreas Fault.
Initially
linear-elastic analyses were carried out to compute vibration
properties, perform sensitivity analyses to assess the influence
of the foundation modulus on the dam response, and to obtain a
preliminary estimate of seismic stresses. The linear-elastic analyses
were conducted using GDAP program.
The
seismic evlautation required a nonlinear numerical model to account
for the effects of potential opening of existing cracks, vertical
joints within the dam, and the dam-foundation contact surface.
These were conducted using QDAP.
The 3D nonlinear finite-element analyses of Searsville Dam were
performed for both static and seismic loads. The nonlinear analyses
were carried out by assuming zero tensile strength for the vertical
cracks and the crown joint and a nominal tensile strength for
the dam-foundation joints. In addition to the stress analysis,
structural stability of the dam against sliding along the dam-foundation
contact surface was also evaluated and factors of safety were
determined. This work was done in association with Dames and Moore
of San Francisco, as the prime contractor.
