Analysis of ground deformation due to groundwater level changes along the MRT line in Bangkok | |
| Author | Nutawat Tungsawat |
| Call Number | AIT Thesis no.GE-19-11 |
| Subject(s) | Mass Rapid Transit Corporation (Thailand) Subsidences (Earth movements)--Thailand--Bangkok Subsoils--Thailand--Bangkok Groundwater--Thailand--Bangkok |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering in Geotechnical and Earth Resources Engineering |
| Publisher | Asian Institute of Technology |
| Abstract | Since the early 1960s, land subsidence due to groundwater drawdown has caused several damages in Bangkok. On the other hand, groundwater level has been recovering gradually from 1997 to the present due to the effective control of groundwater use of this city. To alleviate some geotechnical concerns on stability of structures the combined effect of groundwater drawdown and recovery on land deformation needs to be studied in this research, such an effect is investigated along a MRT line, i.e., the Orange line. First of all, soil characterization along this MRT line was done based on the collected geotechnical testing data from 110 investigation boreholes up to a depth of about 80 m including the results of water content, Atterberg limits, specific gravity, unit weight, one-dimensional consolidation, standard penetration (SPT), unconfined compression , unconsolidated undrained triaxial, etc. The compressibility index and undrained shear strength was correlated with some basic soil properties such as water content, void ratio and water content ratio (ration between water content and liquid limit). In addition, an intrinsic compression analysis was performed. The intrinsic compression curves of ICL and SCL were plotted based on the consolidation test results to understand better on degree of structuration of Bangkok clays and their intrinsic compression behaviors. Compression models were also constructed which is strongly related to intrinsic compression. MCC model parameters, Lambda and Kappa, can be determined by this framework. Based on the groundwater monitoring data obtained from Department of Groundwater Resources (DGR), the contour maps of groundwater level from 1995 to 2020 were constructed for 4 aquifers, i.e., Bangkok (BK), Phra Pradaeng (PD), Nakhon Luang (NL), and Nonthaburi (NB). Data from some selected observation wells, namely, PD0044, NL0059, and NB0055, show that groundwater levels PD, NL, and NB aquifers have recovered since 1997 to 2015 at the average rate of 0.75, 1.23, and 1.15 m/year, respectively. But for some reasons they have remained constant from 2015 until now. Once the soil characterization was done, the soil model was constructed and the picture of groundwater level change was well understood the FEM coupled consolidation analysis to calculate ground deformation along MRT Orange line from 1960 to 2040 under various pore water pressure boundary conditions was conducted using ABAQUS software with the Modified Cam Clay model (MCC). The analysis was carried out, targeting mainly the uppermost 100 m zone. Results of changes in pore water pressure, effective stress, and cumulative settlement of each borehole were calculated and plotted with depth. Ground deformation along three project-based sections of the MRT Orange line was simulated and predicted. It can be seen that an uniform subsidence along all the three sections has occurred with the maximum settlement reaching approximately 34 cm in 2005, after that a ground surface rebound has occurred with the rate from 0.13 to 0.16 cm/year. Impact assessments of groundwater level variations on pile foundation and base excavation instability were carried out. Ultimate pile capacity is decreased in the period 1995 to 2015 caused by groundwater recovery, after that ultimate pile capacity is unchanging due to the constant groundwater level. The analysis of instability of base excavation was performed at Sri Burapha station by varying piezometer head parameter. As a result, base excavation at Sri Burapha is safety in the situation that groundwater level in BK aquifer which is used in the design remains constant at 13 m below the ground surface. |
| Year | 2020 |
| 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) | Pham Huy Giao; |
| Examination Committee(s) | Noppadol Phien-wej;Chao, Kuo-Chieh; |
| Scholarship Donor(s) | Royal Thai Government;Asian Institute of Technology Fellowship; |
| Degree | Thesis (M. Eng.) - Asian Institute of Technology, 2020 |