Behavior of Square Footing Resting on Gypseous Soil and Surrounded by a Sheet Pile Wall

Abstract

Laboratory model is used in this study to investigate the behavior of centrally loaded square footing resting on gypseous soil, and surrounded by a sheet pile wall at a distance of 2B from the footing edge and extend in depth to 2B as well. During this study the soil were subjected to ten cycles of saturation and drainage at one-week interval to simulate heavy rainfalls or floods. It should be noted that the soaking water were added only outside the area surrounded by the sheet pile. Four points were chosen to detect gypsum solubility, three of them below the footing edge at different depths and one outside the sheet pile wall for comparison. It has been found that the dissolved gypsum below the footing is significantly less than the one outside the sheet pile wall. For each cycle of saturation-drainage the gypsum content is found to be reduced by 3 % and 0.8 % for the outsider point and for average of the three points respectively. Settlement during first cycle of saturation – drainage was twice as the second cycle and about four times of the third cycle. However, this first cycle settlement is about 25 % of the settlement of footing where no sheet pile wall is used. To sum up, the sheet pile wall found to be an effective protection to reduce the collapsibility of gypsum soil and to reduce footing settlement.

Effect of Soil Nonlinearity on Analysis of Raft Foundation

“…In the above equation, B is the width of the foundation strip between centerlines of two bays, k is the modulus of subgrade reaction, E f is the modulus of elasticity of foundation material, and I f is the moment of inertia of the cross-section of the footing strip. The rigid method yields overestimation of moments and shear forces in the raft, while the plate on elastic foundation method yields more accurate results [4][5][6][7][8]. According to section 13.3.4.3 of the ACI 318-19 code, soil pressure distribution under raft foundation shall be consistent with the soil properties, and with principles of soil mechanics [9].…”

Effect of Initial Water Content on the Collapsibility of Natural and Cement-Treated Gypseous Soils

“…Collapsible soils may be residual soils resulting from weathering process of rocks producing soils with a wide range of particle-size distribution because of leaching out soluble materials by weathering, leading to large voids and thus unstable structures [1]. The gypseous soil is most likely to be found as stable and has relative strength in its dry conditions but upon wetting, its strength deteriorates and sometimes it collapses if it is soaked in water [2].Water infiltration into gypseous soil or the fluctuation of water table can cause unstable superstructure due to gypsum dissolution, producing cavities and settlement of building, and increase flow rate in hydraulic structure [3,4]. Gypseous soils are very hard soils when they are dry and exhibit large deformation and collapse settlement upon wetting due to the bound weakening and gypsum dissolution.…”

“…Collapsible soils may be residual soils resulting from weathering process of rocks producing soils with a wide range of particle-size distribution because of leaching out soluble materials by weathering, leading to large voids and thus unstable structures [1]. The gypseous soil is most likely to be found as stable and has relative strength in its dry conditions but upon wetting, its strength deteriorates and sometimes it collapses if it is soaked in water [2].…”

Preliminary Study on the Reduction in Shear Strength Parameters of Gypseous Soil upon Wetting

“…However, breaking the gypseous bonds leads to reduction in soil strength. Other methods involve adding solutions such as fuel oil [8] or asphalt cutback [9], silicon oil [10] or putting barriers to isolate gypseous soils from water [11]. Some additives are used to remove the gypsum from soil [12].…”