Hazard analysis of rain-triggered landslides : a case study in Northern Thailand | |
| Author | Fowze, Jhahufarus Sadique Muhammathu |
| Call Number | AIT Diss. no.GE-10-01 |
| Subject(s) | Landslides--Thailand, Northern Landslide hazard analysis--Thailand, Northern |
| Note | A dissertation submitted in partial fulfillment of the requirements for the Degree of Doctor of Engineering in Geotechnical and Geoenvironmental Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. GE-10-01 |
| Abstract | The occmTences of rain-triggered landslide have gained momentum over the recent past in Thailand. This dissertation appraises the applicability of the deterministic approach for rain-triggered landslide hazard analysis, as a pilot study, in a frequently affected area in northern Thailand while demonstrating a viable approach for the characterization of the involved residual soils through a laboratory experimental program including a series of index and performance tests. Modifications to the triaxial top caps were made in new, to conduct suction monitored constant moisture shear tests in the triaxial apparatus. The results of the laboratory program on residual soils collected from Nan and Mae Hong Son Provinces, giving due consideration to their unsaturated nature, are first presented. Subsequently, coupled steady-state and dynamic geospatial modeling of rain-triggered landslides are presented for the selected study area in Nan province. Grain size distributions of the residual soils were found to exhibit bimodality in varying degrees. Coarse grained samples too were found to possess plasticity characteristics. The equation proposed by Fredlund and coworkers for bimodal grain size distribution curves was capable of modeling all the grain size distribution curves with excellent goodness of fit. Soil water characteristic curves obtained from the experimental program also exhibited the characteristics of bimodality. The characteristics of experimental soil water characteristic curves were well captured by Gitirana and Fredlund model for bimodal soil water characteristic curves. Prediction of soil water characteristic curves from grain size distribution curves using the physicoempirical Arya and Paris model showed encouraging results. The saturated permeability values of the tested samples varied in the range of 10-7 to 10- 4 mis. These values together with the soil water characteristics were used to estimate the unsaturated permeability function using statistical approach. The "viliual" pre-consolidation pressures of the samples appeared to have exceeded with the application of effective confining pressures of more than 100 kPa, which exhibited contractive behavior. The determined effective cohesion and friction angles of the selected residual soils varied in the range of 1.1 to 18.3 kPa and 21° to 32°, respectively. The unsaturated shear strength predicted using the saturated shear strength parameters and the soil water characteristics compare reasonably well. Suction monitored constant moisture content shear tests also reveal that the shear strength reduction of the tested unsaturated residual soils from the initial unsaturated state to only up to the "no suction" state could be on average 34 % under tested conditions. . Delineating 78% of about 100 surveyed shallow landslide points to fall in the high and medium hazard areas, deterministic steady state hill-slope hydrology coupled infinite slope stability model was shown to be satisfactory for hazard analysis for the pilot area given the limitation of datasets. The contribution of soil suction in maintaining the slopes were demonstrated. The dynamic hill-slope hydrology coupled infinite slope stability model was shown to capture the ground response adequately by simulating the historical maximum daily rainfall. Establishment of the models also offered a useful platform to analyze a number of scenarios with ease, including rainfall and land cover land use variations, and thereby to support proper land use planning and management activities towards a safer environment. |
| Year | 2011 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. GE-10-01 |
| Type | Dissertation |
| School | School of Engineering and Technology (SET) |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Geotechnical Engineering (GE) |
| Chairperson(s) | Bergado, Dennes T.; |
| Examination Committee(s) | Noppadol Phien-wej ;Giao, Pham Huy ;Samarakoon, Lal ;Panich Voottiprnex ; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2011 |