Utah Admin. Code R655-11-6A - Factors of Safety
A. All dams should
meet the following criteria for factors of safety under normal loading
conditions. TABLE
Minimum Factor
Condition of Safety
End of Construction Case--upstream and
downstream slopes 1.3
Steady State Seepage--upstream and downstream
slopes (full pool) 1.5
Instantaneous Drawdown--upstream slope 1.2
OR
Actual Drawdown--upstream slope 1.5
B. All factors of
safety should be generated by methodology acceptable to the State Engineer. In
undertaking the analysis, the effects of anisotropy should be considered and a
ratio of horizontal to vertical permeability of at least nine should be used in
the seepage analysis, unless otherwise justified to the satisfaction of the
State Engineer. Ratios of up to 100 should be considered if the material types
and construction techniques will cause excessive stratification.
C. The strengths used in the stability
analysis should be obtained from tests which best model the situation being
analyzed.
D. The analysis of the
upstream slope stability for actual drawdown should consider drawdown rates
which the low level outlets are capable of generating. Actual residual pore
pressures should be used.
E. For
low hazard dams the State Engineer may waive the requirements of a stability
analysis, including a seismic analysis, if it can be demonstrated that
conservative slopes and competent materials are used in the dam, and seismic
problems (i.e., liquefiable materials, active faults close to the dam) are not
present.
Notes
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