Xiangan Tunnel provides valuable experience for the construction of Chinese subsea tunnel
3 min readTechnological Innovation Results
After a decade of scientific research and four years and eight months of engineering practice, key technologies for the drilling and blasting method used during the surveying, design, construction and operation of Xiangan Tunnel had been worked out. The packaged technologies of both construction and operation had been completed to fill the domestic gap, marking that Chinese people had mastered the core technology of independently constructing undersea tunnels. This played an exemplary and leading role in China’s construction of subsequent undersea tunnels.Meanwhile, the cutting-edge technology for constructing high-difficulty high-risk undersea tunnels under complicated geological conditions had been enriched and developed, being a milestone in the history of the world’s undersea tunnel construction.
1. The Scientific Comparison and Selection Mode of China’s undersea engineering was established.
The in-depth comparison and selection mode was carried out in one gate dam scheme for tidal power generation, seven sea-crossing bridge schemes and three tunnel schemes(immersed tube, drilling and blasting, and shield tunneling method). After taking many factors into account, such as the high-risk geological conditions like weathered slots and permeable sand layers, the protection of harbor approach resources, the environmental impacts to the Chinese White Dolphin National Natural Reserve, the all-weather operation, the construction technology and the cost of engineering, the drilling and blasting method was finally selected.
2. The comprehensive technologies for high-precision geological exploration under complicated marine environments were established.
During the design period, geological survey technologies for the common land area were optimized both in terms of its parameters and its process. Such innovative technologies as reflection technology of shallow marine seism, CT survey technology of marine cross-hole seismic waves, and experimental technology of marine drilling for water pumping (pressing) were put forward.
During the construction period, the comprehensive geology forecast technology mode for theXiangan Tunnel was established, with heading advance borehole as the principal, geophysical explorations of TSP and infrared water detection as the supplement, and a service channel with a small section as the priority.
3. The design method of tunnel line for the drilling and blasting method for large cross-sections under complicated geological conditions was put forward.
The concept of undersea tunnel bedrock isobath was put forward for the first time. Based on that,a horizontal line design method,a vertical line design method, and a section layout mode with “two vehicular channels +one service channel”were established.
4. The design method of supporting structure system for the large section undersea tunnel was established.
It included the computational formula of external water pressure under the undersea tunnel structure, the optimal undersea tunnel section mode to resist that external water pressure, and the subarea waterproofing and multiple self-waterproofing system of the undersea tunnel. The high performance concrete, temperature control and crack prevention were designed for the tunnel structure for the sake of durability.
5. The safe construction technology for the large section undersea tunnel under complicated geological conditions was established.
It included the tunnel construction technology for the weathered slots, for the water-rich sand layers in the intertidal zone, and for the terrestrial wholly or largely weathered granite; the grouting and plugging water technology and surrounding rock consolidation technology suitable for the undersea tunnel; the tunnel deformation control technology considering soft rock damage and seepage; the tunnel hard rock control and blasting technology considering Chinese white dolphin protection; and the emergency rescue management system for the undersea tunnel construction
6. The technology system for undersea tunnel operation safety and maintenance was established.
It included the undersea tunnel disaster prevention and rescue system, the long-term monitoring system based on undersea tunnel risk identification theory; maintenance technology based on records of undersea tunnel construction, etc.
In addition to the Xiamen Xiangan Tunnel construction, these research results were successfully applied in many other large-scale construction projects, such as Qingdao Jiaozhou Bay Tunnel, Changsha Liuyang River Tunnel, and Xiamen Second West Passage Tunnel.
