Hydrostatic Uplift in Pervious Soils

This paper describes an original research to determine the hydrostatic uplift on the base of a structure, founded on a pervious soil, when there is no loss of head due to velocity of flow. Engineers have not been in agreement on this question, some believing that the pressure due to the hydrostatic head acts on the full area of the base, and others that the pressure acts only on a portion of the area because the remaining portion is in intimate contact with the soil.The paper records the results of 218 tests, not including trial tests, nor those made to standardize the apparatus. The soil materials used were sand, gravel, and clay. The tests were conducted with both low and high hydrostatic heads. The size of the base area, the head, and the unit loading on the soil were varied sufficiently to demonstrate that the results are independent of these factors. Shallow depth of soil under the test base, however, does affect the results.The effective area, or that portion of the base on which the uplift acts, is stated in percentage of the total base area. The test results show that this effective area is approximately 90 to 100%, according to the test conditions.The apparatus used and the methods of conducting the tests are fully described and illustrated.