Effect of ground vibration due to blasting activity in large section tunnel close to Pantai Timur Highway LPT 1

Abstract

Tunnel blast activity for East Cost Railway Project is close to the Pantai Timur Highway at Kuantan, Pahang. Due to the constant rains and humid conditions in the tropical area, rock mass is subjected to severe weathering. This zone is characterized by a thick weathering profile, which necessitates careful caution during blasting. Weathered rock material has a complicated behaviors that is sometimes neglected, especially when dealing with development blasts. Type of rock which is granite was consider in this study. The rock mass character such as strength, geological structure, and discontinuities are affecting the blast design. This needs accurate data, particularly during the development stage, especially when dealing with weathered zones. Various research gaps of different rock mass classification system and safe blasting design are discussed. Field mapping and relevant laboratory, namely point load and compressive strength tests were carried out to establish the rock mass properties. Fifty rock samples were taken from the tunnel, Ch 336 + 996 to Ch 336 + 640. The average of I50 for Sample is 1.2 MPa and the UCS average is 26.51 MPa which is Grade V granite and excavated 56 m from the tunnel face. Rock Grade IV excavated 56 to 176 m and the average I50 and UCS is 1.77 and 30.05 MPa. Rock Grade III excavated 176 to 356 m, I50 average is 3.11 MPa and UCS average 60.42 MPa. Once the rock mass properties have been established, the effect of blast, i.e. fragmentation, flyrock, vibration and air blast were determined in order to find their relationship with the blast design adopted. Based on the result from the analysis, the blast design and method will be suggested to improve the safety and health of the workforce. In another case study, rock mass classification is suggested based on exploration data consisting of Q value from the tunnel face mapping, degree of weathering, degree of hardness and fracture attitude. The three-bench method of blasting was introduced, and new blast design was adopted prior to make good the safety and health of the workforce during tunnel blasting activity.