Abstract
The construction of inclined shafts in extra-long highway tunnels constitutes an important auxiliary construction measure that increases working faces, facilitates mucking and material transportation, improves ventilation, and enhances construction efficiency, thereby holding significant importance for schedule assurance. The right line of the Dapanshan Tunnel has a total length of 8678 m, with the inclined shaft measuring 1498 m in length, a comprehensive gradient of 9.99%, an intersection angle of 66°35′08″ between the inclined shaft and main tunnel, and Grade Ⅲ surrounding rock classification. Based on the Dapanshan extra-long tunnel project of the Hangzhou-Shaoxing-Taizhou Expressway, this paper introduces in detail the technical measures employed in the intersection section between the inclined shaft and main tunnel, including two-bench method excavation (with a cycle advance of 2–3 m), I18 steel arch and foot-lock bolt support, installation of reinforced steel support rings, main tunnel crown excavation and transition to bench method construction, as well as monitoring and measurement of crown settlement and clearance convergence. Monitoring results indicate that the cumulative crown settlement measured 8.2 mm and cumulative peripheral convergence ranged from 4.69–8 mm, both far below the control standard of ±100 mm. Construction from the inclined shaft intersection to the completion of main tunnel crown excavation required only 27 days, with safe construction and controllable deformation, providing a reference for similar intersection construction in extra-long tunnels.
Full Text
Construction Technology at the Intersection of Inclined Shaft and Main Tunnel in Dapanshan Tunnel
Zhang Xu
Shanghai Tunnel Engineering Co., Ltd., Shanghai 200000, China
Abstract
In highway extra-long tunnels, inclined shaft construction serves as a critical auxiliary measure that increases working faces, facilitates muck removal and material transport, improves ventilation, and enhances construction efficiency—playing a vital role in schedule assurance. The right line of Dapanshan Tunnel extends 8678 m, with its inclined shaft measuring 1498 m at a comprehensive gradient of 9.99%. The intersection angle between the inclined shaft and main tunnel is 66°35′08″, with surrounding rock classified as Grade III. Drawing on the Dapanshan extra-long tunnel project of the Hangzhou-Shaoxing-Taizhou Expressway, this paper presents a detailed account of key technical measures at the intersection section: two-bench excavation (with cycle advance of 2–3 m), I18 steel arch support with lock-foot anchor bolts, installation of reinforced steel support rings, main tunnel roof lifting and transition to bench method construction, along with monitoring of crown settlement and clearance convergence. Monitoring results demonstrate a cumulative crown settlement of 8.2 mm and peripheral convergence of 4.69–8 mm, both well below the ±100 mm control standard. The section progressed from inclined shaft intersection construction to main tunnel roof lifting completion in only 27 days, achieving safe construction with controllable deformation. These practices offer valuable reference for similar intersection sections in extra-long tunnel inclined shaft projects.
Keywords: roof lifting; intersection section; bench method; temporary shed support