防止新永春隧道湧水的熱瀝青灌漿工法

HOT BITUMEN GROUTING TO REDUCE INFLOW IN NEW YUNGCHAUG TUNNEL

北迥雙線新永春隧道,在1998年10月24日,距隧道南口1812m處,發生嚴重的湧水問題,最大湧水量逐80m3／min,為了克服此巨大湧水量,進行長距離鑽探作業,以了解湧水區段地質與湧水情形,調查結果發現湧水區段為大理岩層,泅水壓力很高,最大水壓接近4MPa,因此施作大口徑排水宣洩水壓,以減少開挖面的湧水量,最後採用熱瀝青灌漿工法,來進行湧水區段的地盤止水改良工程。開挖結果顯示瀝青滲透岩盤細縫及填補孔洞的性能良好,總湧水量減少顯著,提供日後開挖的安全環境,隧道得以順利貫通。

A major inflow occurred in the New Yungchung Tunnel on October 24 1998. To overcome this huge gushing water, a long-distance drilling program was conducted to discover the geology of the region where groundwater could be a source. It suggests that there is marble bedrock and groundwater of very high pressure. Big drain pipes are then installed to release the water pressure and reduce the inflow at the working face. At last, hot bitumen grouting is used to reduce inflow. The index tests of the bitumen are carried for quality control, and the two most important factors influencing the grouting are the injection pressure and the injection temperature. The effect of grouting can be evaluated by analyzing the grout volume, the actual progress of excavation, the residual gushing water, the injection pressure and temperature of bitumen. The investigation during tunneling shows that ability of hot bitumen to penetrate the crack of the bedrock and to fill the voids is good. The total inflow is reduced apparently, and a safer environment for tunneling is provided.