Evaluation of slope failure due to the reduction of shear strength from the slaking effect at the Mae Moh Mine in Thailand | |
| Author | Peetiya Nidhinandana |
| Call Number | AIT Thesis no.GE-21-03 |
| Subject(s) | Landslides--Thailand--Mae Moh Mine Shear strength of soils--Testing Finite element method Mineral industries--Waste disposal--Thailand--Mae Moh Mine |
| 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 | The stability of waste dumps is crucial to the open-pit mine’s successful operation. It has been observed that most waste materials, especially clay-bearing rock, have significant slaking behaviors, resulting in slope instability. Recently, the large slope failure of the western dumping area occurred at Mae Moh Lignite Mine, Lampang, Thailand. One of the causes concluded in the investigation report was the slaking of poor-quality waste materials over time which later broke down to form a clay layer. Since this dump will be continuously operating, it is essential to evaluate the slope stability with the change of shear strength due to slaking behavior of waste materials at the slope base. Red Bed and grey claystones (OB, IB, and UB) were collected from the Mae Moh mine and subjected to wet-dry cycles in the laboratory. The slaking progressive of the specimen was determined by grain size distribution analysis. Clay content, intact rock strength, and original confining pressure significantly influence the slaking behaviors. The direct shear tests were performed on slaked materials at the designed cycles. As a result of fine particle increment and poorly-graded distribution with higher cycles, the obtained friction angles were decreased while the apparent cohesion from matric suction was increased at the same water content. The slope stability analyses with obtained friction angle indicated the factor of safety (FS) is much higher than one at the initial condition without slaking and continues decreasing close to unity at the completed slaking cycles indicated by average particle size (D50). Therefore, slaking effect could have caused the slope failure potential. Moreover, the grading improved slope after the failure was analyzed with the back-calculated condition and future activities. The results reveal that the FS is still less than the stability criteria of 1.3 even before the additional dumps. The soil suction was considered with the dewatering process and gave the higher FS equaling to 1.3 before adding new dumps. However, to maintain the same factor of safety, only 70-75% of the original volume can be dumped with a very conservative slope angle of 3.5 degrees and 0-200 m setback distances. Therefore, to reach FS=1.3 and the original dump volume design, additional ground improvement or protective structure should be considered. |
| Year | 2022 |
| 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) | Chao, Kuo Chieh; |
| Examination Committee(s) | Noppadol Phien-Wej;Avirut Puttiwongrak; |
| Scholarship Donor(s) | Asian Institute of Technology Scholarships; |
| Degree | Thesis (M. Eng.) - Asian Institute of Technology, 2022 |