DECEMBER 20, 2000

The Results of Using Isolation Tools Around Pier Shafts

Speaker: Dr. Mike O'Neill

The December meeting featured Dr. Mike O'Neill, a geotechnical professor from U of H. He presented the results of using isolation tubes around pier shafts. He continuously measured pier elevations and in-situ soil suction and demonstrated how isolating the pier shaft from the soil nearly stopped the heave and subsidence that non-isolated piers experienced. He said that skin friction in the clays at the U of H site were found to measure about 1/2 of the shear strength. He also said that for non-isolated piers in Houston to be stable they needed to extend at least twice the depth of constant suction.