Underwater Tunnel Construction Research Articles

Analysis on the excavation management system of slurry shield TBM in permeable sandy ground

Slurry shield TBMs with full-face mechanized excavation and active face support using slurry suspension are increasingly being employed for the construction of underwater tunnels. When tunneling in permeable sandy ground, the choice of suitable excavation management system and volume calculation method is extremely important to prevent security emergencies such as face collapse, water inflow and ground deformation. However, this subject has not attracted adequate attention in previous studies. Until now, there is still a lack of reliable methods to calculate geomaterials excavated from the tunnel face in permeable sandy ground. In the present study, shortcomings of traditional calculation method have been analyzed. Improved calculation method considering the effect of slurry filtration loss and ground water displacement has been proposed to evaluate the performance of excavation management system in permeable sandy ground. A case study of Sutong GIL Yangtze River Crossing Cable Tunnel has been carried out. The results indicate that the calculation error based on the improved method is smaller than that based on the traditional method. The improved method is much more suitable for permeable sandy ground.

A static risk assessment model for underwater shield tunnel construction

The shield method is widely used in underwater tunnel construction. However, the shield construction process faces many uncertain risk factors that increase the level of safety risk during shield tunnel construction. Therefore, risk assessment has become a necessary task in the early stages of tunnel construction. In this study, a new risk assessment model for underwater shield tunnel construction is proposed that combines a normal cloud model with an entropy weight method. The model contains 20 assessment indexes and gives the range of each index corresponding to different risk levels, which comprehensively reflects the influencing factors of risk. By using a normal cloud model, the fuzziness and randomness of risk assessment data are taken into account effectively, and the reliability of assessment results is increased. Based on an entropy weight method, the rules and characteristics of the evaluation data in the model are considered, and the weight coefficient of the evaluation index is determined to avoid the subjectivity of the expert weight method. The risk assessment model is applied using the Xiangjiang shield tunnel as an example. The results show that the overall construction risk level of the Xiangjiang tunnel is level II, which is consistent with the site risk situation and shows that the model can objectively and accurately evaluate the construction risk level of an underwater shield tunnel.

Seepage Analysis and Optimization of Engineering Method for Municipal Underwater Tunnel Construction in Urban Coastal Stratum

Li X.-Z.; Zhu, Y.-Q., and Zhao, J., 2019. Seepage analysis and optimization of engineering method for municipal underwater tunnel construction in urban coastal stratum. In: Gong, D.; Zhu, H., and Liu, R. (eds.), Selected Topics in Coastal Research: Engineering, Industry, Economy, and Sustainable Development. Journal of Coastal Research, Special Issue No. 94, pp. 260–263. Coconut Creek (Florida), ISSN 0749-0208.A municipal tunnel is a double-deck tunnel shared by traffic and municipal corridors. It is an underwater tunnel in the coastal stratum. Water seepage must be considered during the tunnel construction process. By establishing a three-dimensional geo-mechanical calculation model and considering the seepage, the construction process of the two construction methods, the step method and the CRD method, is analyzed. The CRD method is better in controlling tunnel deformation, tunnel seepage and pore water pressure distribution.

Face Stability Assessment for Underwater Tunneling Across a Fault Zone

AbstractFace stability is critical for the safety of underwater tunnel construction across fault zones. This paper presents a new analytical method that can be used to assess such stability. Follow...

Impacts of confining pressure and safety thickness on water and mud inrush in weathered granite

Due to the strong disintegration and water erosion of completely weathered granite, water and mud inrush disasters are apt to take place in this zone during underwater tunnel construction. The pore, compactness, seepage path length, fracture geometries and their interconnections for water and mud transfer are strongly influenced by confining pressure and waterproof-resistant slab safety thickness. In order to inspect the influence, a series of experiments based on a self-designed testing system and non-Darcy testing method were performed. The results indicated that the water and mud inrush evolution increased with the increase of confining pressure and decreased with the increase of safety thickness. In particular, the confining pressure mainly influences the initial evolution stage, and a critical safety thickness to prevent water and mud inrush is obtained. Besides, the non-Darcy testing method results shows that the water and mud inrush evolution affects the influence of non-Darcy flow. For example, while the safety thickness was smaller than the critical value, the evolution was large and unstable and its behavior transferred into nonlinear. In this case, the flow changed to non-Darcy flow.

Typical Underwater Tunnels in the Mainland of China and Related Tunneling Technologies

Abstract In the past decades, many underwater tunnels have been constructed in the mainland of China, and great progress has been made in related tunneling technologies. This paper presents the history and state of the art of underwater tunnels in the mainland of China in terms of shield-bored tunnels, drill-and-blast tunnels, and immersed tunnels. Typical underwater tunnels of these types in the mainland of China are described, along with innovative technologies regarding comprehensive geological prediction, grouting-based consolidation, the design and construction of large cross-sectional tunnels with shallow cover in weak strata, cutting tool replacement under limited drainage and reduced pressure conditions, the detection and treatment of boulders, the construction of underwater tunnels in areas with high seismic intensity, and the treatment of serious sedimentation in a foundation channel of immersed tunnels. Some suggestions are made regarding the three potential great strait-crossing tunnels—the Qiongzhou Strait-Crossing Tunnel, Bohai Strait-Crossing Tunnel, and Taiwan Strait-Crossing Tunnel—and issues related to these great strait-crossing tunnels that need further study are proposed.

Scene Design and Simulation Analysis of Fire Accident in Underwater Tunnel

In order to reduce the risk of tunnel fire accident, determine the fire power of the tunnel disaster prevention and evacuation facilities set requirements, by means of tunnel fire risk analysis and accident characteristics summary of proposed safety criterion for the design of underwater tunnel fire accident scene, fire power and growth rate, smoke exhaust mode and smoke emission selection, number of evacuation and evacuation time standards and so on. Using FDS+EVAC to simulate and analyze the scene of fire process and personnel evacuation, in order to better help us identify fire risk, to develop in line with the actual project of disaster prevention programs, service in underwater tunnel construction and post operation.

Incremental Launching of Structures

The incremental launching method for concrete structures was first developed in the early 1960'S. Since then it has spread all over the world. Bridges constructed by this method are cast in segments behind an abutment in a stationary form against a previously cast segment of the bridge girder. The whole superstructure is then longitudinally jacked forward incrementally to make room for the next segment in the stationary form. This method combines the advantages of precasting with those of cast‐in‐place methods, resulting in a high concrete quality and low costs. Remarkable achievements of incrementally launched bridges the to data are: Longest continuous superstructure [3,809 ft (1,161 m)]; longest span in final stage [551 ft (168 m)]; longest span during launching with auxiliary stays on top [436 ft (133 m)]; and a strongly curved bridge superstructure in plan with a radius of 492 ft (150 m). The incremental launching method has also been applied to buildings; e.g. across railway tracks. A new potential application is the construction of underwater tunnels. The main savings are achieved by the reduced labor and equipment expenditure.

Principles of trench tunnel construction : Murphy, G J Paper to 3rd Australian Tunnelling Conference, Sydney, 12–15 Sept 1978, 9P

The construction of underwater tunnels (immersed-tube construction) by the lowering into a previously prepared underwater trench of a series of bulkheaded elements and the joining underwater of element to element to form an integrated whole represents a technique perfected during this century. Although early sewer and railway tunnels adopted this methodology, it was the rapid development of vehicular transportation after World War I that gave impetus to this type of construction. A description of the design and construction of several types of immersed-tube tunnels is set forth. An early basic element was the adaptation of an all-welded circular steel shell, with or without exterior form plates. The shell some 100 meters in length was lined with a circular ring of reinforced concrete forming the structural element. This circular steel section was particularly adapted for two-lane highway tunnels, but was later modified and improved to furnish four-lane tunnels. The practice abroad, particularly in Europe, is the construction of large rectangular box sections of reinforced or prestressed concrete to provide for up to eight lanes of traffic. A brief description of the 6000-meter long Trans-Bay Tube in San Francisco, California, is given.

Prefabricated sections in the construction of underwater tunnels

Prefabricated sections in the construction of underwater tunnels

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This article describes the results obtained by the Dutch Central Institute of Scientific Research when studying the problem of underwater tunnels. This Institute has sought to establish general specifications for the design of this type of tunnels, so that they shall be more efficient than those at present in use. Firstly, a study was made of the strength, waterproof qualities, and most rational type of ventilation, with a view to drawing up of general principles on this aspect of the design. An analysis is given of the shape, suitable cross sections and constructive methods, and these are compared with those adopted in the construction of underwater tunnels at present in use in America. Particular attention has been given to designs which are largely based on prefabrication and the use of factory made structural parts, and also on the transport and erection of these at the site. The author goes on to discuss the interplay of soil and water pressures, buoyancy forces, and cases in which the tunnel is subjected to important bending and shear forces on particular sections of it. In this connection care is taken to give the theoretical considerations a ready practical interpretation. In particular, a description is given of special distance pieces which connect the two tubes making up a tunnel, also the system of joining two sections of the tube, and the measure of watertightness and flexibility which such joints provide. Finally, a summary is given of the theoretical foundations, as well as a number of observations and items of advise, which are applicable to these types of structures.