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Earthworks
Published in Jonathan Knappett, R. F. Craig, Craig’s Soil Mechanics, 2019
Jonathan Knappett, R. F. Craig
Similar to slopes and cuttings, tunnels and sinkholes (i.e. underground excavations which are either intentional or unintentional, respectively) are a class of problem for which self-support of the soil mass also controls the design. Shallow tunnels onshore may be constructed using the cut-and-cover technique; this is where a deep excavation is made, within which the tunnel is constructed, which is then backfilled to bury the tunnel structure. The design of such works may be completed using the techniques described in Chapter 11, and this class of tunnel will not be considered further here. In marine and offshore applications, sections of tunnel structure may be floated out to site, flooded to lower them into a shallow trench excavated on the riverbed/seabed and connected underwater, followed by pumping out of the internal water. These are known as immersed tube tunnels. Some of the terminology related to tunnels is shown in Figure 12.24.
Tunnel construction techniques
Published in David Chapman, Nicole Metje, Alfred Stärk, Introduction to Tunnel Construction, 2017
David Chapman, Nicole Metje, Alfred Stärk
Immersed tube tunnels are ideal for crossing rivers and estuaries in urban areas. Owing to the location just under the river/sea bed, this method can be considerably cheaper than excavating or boring (TBM driving) through the ground under the river/sea bed. The surface infrastructure (roads, railtrack) needs to connect to the tunnel but is constrained by limits on gradients that are suitable for cars or trains. Therefore, the deeper the tunnel, the longer this lead in section needs to be. Since bored tunnels are generally constructed at a greater depth, which is necessary for ground stability during construction, they are often longer than immersed tube tunnels and hence more costly. Bored tunnels may also be technically more challenging due to the high water pressures, which can be a problem during construction.
Reinforcement learning for safe evacuation time of fire in Hong Kong-Zhuhai-Macau immersed tube tunnel
Published in Systems Science & Control Engineering, 2018
In recent years, with the establishment of the international economic zone and the new exploitation of global marine resources, an increasing number of transcontinental and transnational passages have been constructed. Immersed tube tunnel plays an important role, as it has many advantages, for instance, it does not occupy the navigation channel, can be used under any weather circumstances, has little impacts on the environment and makes full use of the underground space, etc.. Gradually, people are changing their traditional concept that ‘coming across the water, making a bridge’. The immersed tunnel is under the river and deep sea, which brings convenience as well as difficulties of evacuation when fire disasters occur. The fire has became one of the main disasters which occur frequently in tunnels. And the deep depth of the immersed tube tunnel makes the escape from vehicle fire extremely difficult. Through the analysis of a large number of accident cases, we found that no effective measures were taken to prevent the possible crowd crowding before the accident and there was no timely and effective evacuation in case of fire. When fire and other accidents happen, the clock is ticking, how to choose the optimal path to achieve minimum evacuation time becomes an important issue.
Study on bearing characteristics of marine subsoil for semi-rigid immersed tunnel
Published in Marine Georesources & Geotechnology, 2022
Yapeng Niu, Yongli Xie, Hongguang Zhang, Xiabing Yue, Yingguang Han, Zhinan Hu
Since the development of immersed tube tunnel structure, various structural types such as reinforced concrete immersed tube, steel shell concrete immersed tube, and reinforced prestressed concrete immersed tube, have been utilized, with the reinforced concrete immersed tunnels being the most widely used (Lunniss, Baber, and 2013).