Experimental Investigation of Capillary Rise in Unsaturated Gypseous Soils

Abstract

Capillary rise is a phenomenon that must be considered an inevitable factor when dealing with unsaturated gypseous soil. This study investigates the behavior of gypseous unsaturated soil under capillary action, where different gypsum content and soil densities are experimentally tested in a developed laboratory model consisting of Transparent pipes 1 m long and 0.05 m in diameter. All the pipes are placed inside a rectangular basin with a dimension of (1500×500×500 mm). The soil was taken from Tikrit city in Iraq at a depth of (1.5 to 2 m) under the natural soil surface; the laboratory tests clarified that the soil is poorly graded sand with a gypsum percent of 59%. The three other gypseous soil samples were prepared by dissolving with HCl acid to gain the required percentages of gypsum (22, 37, and 6%). The results show that the presence of gypsum in the soil slows down the rise of water in the soil after rapid rising in the first stages of the test. The low and moderately gypseous soils required a shorter time to reach the maximum capillary rise than highly gypseous soils. Also, the existence of gypsum increased the max. The height of the capillary rise and the degree of saturation in the capillary zone were also noticed for all soil densities examined. The effective stress will be low in the fully saturated parts while it’s high in the low saturated parts.