Landslides and Debris Flows at Khao Phanom Benja in Krabi, Sounthern Thailand
- Pathum Thani, Thailand : Asian Institute of Technology, 2017
- 1 online resource (215 leaves) : ill. + 1 online resource
- Dissertation ; no. GE-17-02 .
- Asian Institute of Technology. Dissertation; no. GE-17-02 .
A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering in Geotechnical and Earth Resources Engineering, School of Engineering and Technology
Thesis (Ph.D.) - Asian Institute of Technology, 2018
A detailed investigation on the characteristics of the 2011 catastrophic landslides of Khao Phanom Benja, Krabi, Thailand was conducted. The landslides on the slope faces of the high relief granitic mountain led to devastating debris flows of large rock boulders that buried houses in the foothill area. The unfavorable orientations of four major joint sets of the mountain created high kinematic instability of rock wedge slides along the stream channel direction as well as rock wedge formation on the channel walls in the eastern sides of the mountain. Weathering and joint opening in the areas of slopes and stream channels increase the vulnerability of rock slides, in particular for a prolonged heavy rainfall. The heavy rainfall and stream channel flows on slab block of rock slope erosion along stream bank caused down bank slope failure. The increasing upward water pressure caused the increase in uplift force behind the rock block and rock wedge failure. Based on the equilibrium conditions of the potential plane and wedge failures, the factor of safety had been highly decreased when percentage of height of water in tension crack increases. The stability of rock slope failure at Khao Phanom Benja might be change from stable to unstable when the ground water pressure in term of percentage of height of water in tension crack rising up to 30-75%.In addition, the hazard zone delineation of debris flows deposition was mapped out using a MATLAB code named as DFLOWZ. Majority of slides on the eastern slopes of the mountain were granitic rock slide modes while soil slide and surface erosion on residual soil to completely weathered sedimentary rock were the predominant modes of failure on the western and northern slopes in lower areas at foothills of the mountain. As found in this investigation the factors influencing landslides and debris flows in 2011 at Khao Phanom Benja, Krabi, southern Thailand were not only limited to the prolonged rainfall but also to slope gradient, rock types and weathering degree, discontinuity characteristics.