Dam Design
Design concern: (Hydrostatic Uplift) Hydrostatic pressure above the heel (upstream edge) of the dam may cause seepage with resultant uplift beneath the dam base (depends largely on the supporting material of the dam). This reduces the dams stability to sliding and overturning by effectively reducing the weight of the dam structure. (Question: What prevents the dam from sliding?)
Determine the minimum compressive stresses in the base of a concrete gravity dam as given below. It is important that this value should be greater than zero because (1) concrete has poor tensile strength. Damage might occur near the heel of the dam. (2) The lifting of the dam structure will accelerate the seeping rate of the water underneath the dam and further increase hydrostatic uplift and generate more instability.
Catastrophic breakdown can occur if this factor is not considered: for example, it is partially responsible for the total collapse of the St. Francis Dam in California, 1928.