| Author | A-Nanya Chaladthanyakit |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering in Geotechnical and Earth Resources Engineering, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Abstract | Traditionally to design the pile in the expansive soils, the shearing stress from the uplift is predicted based on the saturated soil mechanics. The maximum magnitude of uplift skin friction which exerts on the pile shaft is estimated by using the swelling pressure and coefficient of uplift between soil and pile. The alpha (α) value as a saturated condition is commonly used for the conservative design. However, the scenarios that engineers encounter in the engineering practice, the pile may be founded in the unsaturated conditions. The increasing moisture in the soil is the cause of increasing the volume and swelling pressure. It also causes a reduction in matric suction. Due to several factors that influence the uplift shear stress, the alpha value might not be constant as considered in saturated condition for design.
In this research, a series of single pile model test was conducted in the laboratory and studied the influence of change in the degree of saturation on the α value. The soil in this study is artificial clay prepared by mixing bentonite and sand at the different initial degree of saturation. The basic properties test, the direct shear test, the constant volume test, the consolidation swelling test, and suction measurement are conducted following the procedure of ASTM, in order to obtain the variables used to determine the α value.
Back-calculation of alpha value as a function of the swelling pressure and matric suction from the theoretical equation shows, that the alpha value increases as the beta value increases since both are influenced by increasing of initial degree of saturation. However, the difference in the increase of the alpha value is less than 10 % with the different initial degree of saturation. Therefore, the alpha value can be used as a constant value in pile design in expansive soils.
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| Year | 2019 |
| Type | Thesis |
| School | School of Engineering and Technology |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Geotechnical Engineering (GE) |
| Chairperson(s) | Kuo-Chieh Chao; |
| Examination Committee(s) | Pham Huy Giao;Noppadol Phien-wej ; |
| Scholarship Donor(s) | Royal Thai Government Fellowship ; |