Role of Gypsum on Shear Strength and Its Relation With Some

Abstract

A laboratory experiment was conducted to investigate the role of soil gypsum content on soil shear strength and its relation with penetration resistance, wet B.D, porosity and void ratio. Different soil samples with different gypsum contents were prepared, So(0), S1(100), S2(200), S3(300), S4(400) and S5(500) gm.kg-1 through mixing surface soil (So) sampled from Tuwaitha site (40km south- East of Baghdad) with different levels of pure gypsum. Prepared gypsiferous soil samples were wetted by spraying of water to reach at half field capacity. and incubated for 60 days in plastic bags with continual daily mixing. After the incubation period, the soil samples were air dried, grinded and sieved through a 2mm sieve. Soil samples were packed into a standard rings to a bulk density of 1.25 Mg.m-3.Some soil physical characteristics were determined such as shear strength of soil and soil penetration resistance and wet bulk density and moisture characteristics curve at 0, 33, 100, 300, 500 and 1000 kPa, porosity and void ratio for each soil sample. The results showed that the Increasing soil moisture tension caused un increasing soil shear strength, penetration resistance and reducing of soil wet bulk density values. Increasing in gypsum content up to 200gm.kg-1 caused un increasing in soil shear strength and penetration resistance, and tends to decrease gradually next to 200gm.kg-1 gypsum content. A positive logarithmic relation was derived between soil shear strength and penetration resistance values for all soil gypsum content treatments. A negative logarithmic relation was obtained between soil shear strength and wet bulk density for all the studied moisture tensions.