Does the removal of significant sediment, rock, or soil above a tunnel lining or crown, cause that tunnel to migrate vertically?
Yes, the removal of significant sediment, rock, or soil above a tunnel lining or crown, can result in tunnel to migrate vertically.
- The rock is weakened largely by blasting and the removal of supporting rock. The movement wraps around the tunnel and generates wedges of material that push in on the walls of the tunnel. It causes the tunnel to migrate vertically.
- Additionally, the removal of significant sediment results in a movement toward the tunnel from above. This movement wraps around the tunnel and generates wedges of material that push in on the walls of the tunnel.
Tunnel design[edit]
The most efficient design is determined by fundamental mechanical principles in combination with the categorization of rock masses. For example, tunnels almost never have a flat ceiling when they are dug. The reason behind this is that as the span becomes wider, the rock in the middle of the tunnel has less force holding it up, and a tunnel with a flat ceiling is more likely to collapse. However, when tunneling through firmly stratified rock, such as shale, the ceiling is often cut flat in order to make the most of the rock's inherent inclination to break along bedding planes.[1] [2]
Tunnels are dug with roofs that are segmented in a circular pattern since this is the geometric form that is the most resistant to the effects of an applied force from the outside.[3]
Concept of stress and strain[edit]
The ideas of stress and strain are the fundamentals of mechanics used in tunneling the most. On the other hand, more recent models have shifted away from concentrating on stress and strain.[4]
Rocks that are situated close to a tunnel are said to be subjected to triaxial compression. If the rocks are already under triaxial compression and the constraining rock on one side of the tunnel is removed as it is driven, then there will be a strong stress gradient on the rocks. This leads to a very hazardous scenario. On one side, the rocks that make up the tunnel wall and ceiling will be exposed to high stresses; however, the force that would normally work to counterbalance those stresses is no longer there since those rocks have been removed.[5]
How to investigate vital migration of tunnel[edit]
A distributed circuit model is used to investigate a structure known as a "vertical TFET," which occurs when tunneling takes place between two layers in a direction that is orthogonal to the direction in which source-to-drain net current flows. In the total computation, both the vertical tunneling model and the lateral drift-diffusion model are taken into account, and the contests that occur between these two processes are shown. [6]
Conductivity in the lateral direction rises when the gate length is shortened, but conductivity in the vertical direction decreases when the gate length is shortened.[6]
Mitigating tunnel vertical movement[edit]
As the evacuation surface distance increases, the maximum of the surface sedimentation curve will eventually become increasingly less significant. When the distance between the up and down tunnel evacuation sections is greater than 30 meters, the surface sedimentation curve looks very much like the surface sedimentation curve for single-hole tunnel evacuation. This means that the up-tunnel has very little impact on the up-tunnel evacuation section.[7]
There is a fixed limit at the bottom of the soil layer, which will prevent horizontal movement and vertical shift. The horizontal movement will be restricted as a result of the left and right horizontal limits imposed by the soil layer. The free boundary is determined to be the ground surface, which is located above the upper surface of the soil layer.[8]
Understanding the dynamical behaviors of parallel tunneling, performing numerical analysis on the system, and gaining an understanding of the mutual influences of various factors on the tunnel evacuation and the resultant impact of surface sedimentation have significant conceptual significance and application value for the building technology of parallel double-hole tunnels. Since the mutual influences of double-hole parallel tunneling are very complicated and the influence factors are abundant, studying the dynamical behaviors of parallel tunneling is necessary.[9]
References[edit]
- ↑ "[Solved] A vertical gate closes a horizontal tunnel 4 m high and 4 m". Testbook. Retrieved 2022-10-07.
- ↑ Massinas, Spiros (2019-12-24). Designing a Tunnel. IntechOpen. ISBN 978-1-78985-466-4.
- ↑ Min, Jie (2017). Physical and Compact Modeling of vertical and lateral tunnel field effect transistors (Thesis). UC San Diego.
- ↑ Min, Jie (2017). Physical and Compact Modeling of vertical and lateral tunnel field effect transistors (Thesis). UC San Diego.
- ↑ "How Tunnels Work". HowStuffWorks. 2006-11-04. Retrieved 2022-10-07.
- ↑ 6.0 6.1 Ng, C.W.W.; Shi, Jiangwei; Mašín, David; Sun, Huasheng; Lei, G.H. (2015). "Influence of sand density and retaining wall stiffness on three-dimensional responses of tunnel to basement excavation". Canadian Geotechnical Journal. 52 (11): 1811–1829. doi:10.1139/cgj-2014-0150. ISSN 0008-3674.
- ↑ Ng, C.W.W.; Shi, Jiangwei; Mašín, David; Sun, Huasheng; Lei, G.H. (2015). "Influence of sand density and retaining wall stiffness on three-dimensional responses of tunnel to basement excavation". Canadian Geotechnical Journal. 52 (11): 1811–1829. doi:10.1139/cgj-2014-0150. ISSN 0008-3674.
- ↑ "Lateral Movement - an overview | ScienceDirect Topics". www.sciencedirect.com. Retrieved 2022-10-07.
- ↑ Ghaboussi, Jamshid; Ranken, Randall E. (1977). "Interaction between two parallel tunnels". International Journal for Numerical and Analytical Methods in Geomechanics. 1 (1): 75–103. doi:10.1002/nag.1610010107. ISSN 0363-9061.