Reduction of over-excavation drill and blast tunnel excavation by optimizing blasting design | |
| Author | Rattanon Doungdeeying |
| Call Number | AIT Thesis no.GE-22-11 |
| Subject(s) | Excavation Tunneling |
| 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 optimized method to reduce overbreak during tunnel construction using the NATM method at a High-speed railway project in Thailand, specifically the Contact 3-2 tunnel construction work between Muak Lek and Lam Takhong, has been examined in this study. Overbreak in underground excavation refers to the void created during excavation beyond the payable excavation line or pay line. In this thesis, the payable excavation line has been set at 15 cm or 5% from the excavation line. After conducting a site visit and collecting data, the evaluation reveals that the rock formation consists of shale, limestone, clay, silty clay, and mudstone, resulting in approximately 30% overbreak in class IV. After comparing the data with the doubling track project located nearby, which has a tunnel length of 2,433.74 meters and 552 x-sections, the percentage of overbreak in classes II, III, and IV is found to be 11.67%, 12.52%, and 13.98%, respectively. Therefore, the factors that need to be controlled during drilling and blasting excavation are the geological condition, the length of drill holes, the powder factor, and the smooth blasting technique. The geological condition at the tunnel face can guide site engineer in designing the drilling pattern, and the length of drilling depends on the rock condition, which the driller must control. The powder factor also affects overbreak, and a powder factor of approximately 1.3 kg/Cu.m. is recommended for rock class IV based on data from the doubling track project. The smooth blasting technique, which uses small emulsion and detonating cord to blast at the contour line, controls the energy distribution of the explosives used in the blasting process. A blasting test was conducted at the entranceway of the Muak Lek tunnel, where the rock condition was found to be class IV, with shale and mud clay mixing at the tunnel face. By controlling the length of the drilling pattern, powder factor, and using the smooth blasting technique, the overbreak was reduced to around 10% in the tested section. Therefore, these factors should be implemented to control overbreak during tunnel construction. |
| 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) | Kuo-Chieh Chao;Noppadol Phien-Wej (Co-Chairperson) |
| Examination Committee(s) | Avirut Puttiwongrak;Krit Saowiang |
| Scholarship Donor(s) | Right Tunnelling PCL Scholarship |
| Degree | Thesis (M. Eng.) - Asian Institute of Technology, 2023 |