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Title: Apparatus and tests for determining negative pore water pressure characteristics of desiccated clays
Authors: United States. Assistant Secretary of the Army (R & D)
Carlson, Charles A.
Keywords: Clays
Clay soils
Pore water pressure
Soil tests
Soil water
Soil mechanics
Soil moisture
Publisher: U.S. Army Engineer Waterways Experiment Station.
Engineer Research and Development Center (U.S.)
Description: Miscellaneous Paper
Abstract: The study reported herein was initiated to evaluate the influence of negative pore water pressure development in expansive desiccated clays on building behavior. This report describes the apparatus and procedures for the determination of negative pore water pressure characteristics of desiccated clays. Three trials on specimens plus auxiliary tests were conducted on samples from a test site at Lackland AFB. The water content decreased from 28.5 to 25.5 percent as the negative pore water pressure increased from 0 to 20 atm. Height changed 1.2 percent for a 1 percent change in water content. The initial negative pore water pressure occurred between 1 and 3 atm, differing by specimen. The observed upward movement of heave plugs at the test site provided evidence of the existence of negative pore water pressure. The lack of gradients of temperature or salt content indicated that water conduction was not influenced by these two factors. The soil permeability determined by specimen flow and falling-head piezometer was low at depths below 30 ft. The permeability of concrete suggested that foundation piers in these soils may act as wicks, conducting water downward beyond the inverted capillary fringe and zone of fissures. This source of water for clay expansion should be investigated.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Miscellaneous Paper

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