Experiments of salinity effect on soft Bangkok clay : a case study of road embankment slope stability | |
| Author | Kanokrat Khansanthia |
| Call Number | AIT Thesis no.GE-22-09 |
| Subject(s) | Soil salinization--Thailand Clay--Thailand Soil mechanics--Thailand |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Geotechnical and Earth Resources Engineering |
| Publisher | Asian Institute of Technology |
| Abstract | The central lowland of Thailand has been deposited in large regions by massive sedimentary strata. The soft Bangkok clay, a homogeneous marine sediment, is one of the unique layers and influences foundation consideration in many construction projects. Slope instability on the soft ground surrounding the Chao Phraya Plain, particularly along the canal rural road, is another concern that causes property damage. Although insecure foundations, rapid drawdown, and vehicle overload are the most significant effects on slope stability, soil salinity remains a mystery in terms of its influence on the strength of the slope. The main objectives of this study are to investigate the salinity effect on soft Bangkok clay related to the slope strength and to evaluate the factor of safety of slope due to soil salinity in road embankment. In this study, the marine clay was collected from station 17+535 m of rural road PT.5021, Phathum Thani, Thailand. The geotechnical and geophysical characteristics of five soil salinity conditions (clean soil, original soil, adding 2.5%, 5%, and 7.5% NaCl to soil) with curing time were investigated. Then, the numerical modeling was performed in different scenarios: saturated soil and partially unsaturated soil conditions. It was discovered that increasing the salt content reduced soil plasticity. There were no significant changes in hydraulic conductivity due to the soil type and short release time. On the other hand, both the unconfined compressive strength (UCS) and the undrained shear strength ( {u1D446}{u1D446}{u1D462}{u1D462}) presented the interest values after evaporation. The soil strength gradually increases according to increasing salt content, reaching its maximum at 2.5% NaCl addition. For the geophysical properties of soil, when the soil salinity increased, the soil resistivity dropped in the opposite direction as the soil electrical conductivity increased. As a laboratory result, it is possible to conclude that 2.5% NaCl addition has a huge impact on the geotechnical and geophysical properties of soft clay. The slope stability analysis was carried out by changing absolutely the undrained shear strength as a proportion of salt content. As a result, the factor of safety of canal embankment would rise when the soil strength increases. It is undeniable that the appropriate salt concentration (2.5% NaCl) can help to improve marine clay strength and contribute significantly to slope strength. |
| Year | 2023 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Geotechnical Engineering (GE) |
| Chairperson(s) | Avirut Puttiwongrak |
| Examination Committee(s) | Kuo-Chieh Chao;Pham Huy Giao;Krit Saowiang |
| Scholarship Donor(s) | Royal Thai Government Fellowship |
| Degree | Thesis (M. Sc.) - Asian Institute of Technology, 2023 |