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Lin, Ming (CCCC HZMB Island and Tunnel Project General Office) | Lin, Wei (CCCC HZMB Island and Tunnel Project General Office) | Van Stee, Joel (Trelleborg B.V.) | Peng, Xiaopeng (CCCC HZMB Island and Tunnel Project General Office)
The immersed tunnel of Hong Kong-Zhuhai-Macao Bridge (HZMB) contains 219 segmented joints, 60% of which are placed at water depth over 40m and each segmented joint is of circumferential length of approximately 90 m. To ensure the watertightness, the improvement of using the injectable waterstop was attempted and no leakage was found in the 5.664 km long tunnel up to now. The ways of improvement were elaborated in this paper and the conclusion drawn is that the effectiveness of watersealing can be achieved by looking at the system covering the structure and foundation of each tunnel element. Further, the elongation of the injectable waterstop that may lead to water passage was controlled by using permanent prestressing tendons longitudinally to confine the opening of the segmented joint
The waterproofness of the segmented joint of HZMB immersed tunnel has been a challenge, for over 3 km long section is located in water depth of over 40m (maximum water depth is approximately 46 m). Further, the segmented joints amounts to 219 in total and the length of each joint is as long as 90m. Comparatively, other immersed tunnels in the world has either shallower water depth or smaller cross-section (Rasmussen and Grantz, 1997); some minor leakages were reported by (Grantz et al., 1997), and as per the third author's experience of over 20 immersed tunnel, leakage through segmented joint has always been a concern. Nevertheless, no leakage has ever occurred at the segmented joints in HZMB tunnel from the commencement of installation of tunnel element in May 2013 to the completion of all installation in March 2017, and to now (June 2018).
With the consideration of tunnel's large scale and risk of this project, four rounds of waterstops were initially made for the segmented joint in the beginning of works, namely, polyurea + injectable waterstop + water expansion adhesive belt + Omega gasket. As a matter of fact, the work of water expansive adhesive belt is hard to be executed and is thus cancelled. The polyurea layer is vulnerable to fall off under the wave effect during towing of tunnel element. Therefore, the two key rounds of waterstops are injectable waterstop and the Omega seal.
Of these two, the injectable waterstop (also named after rubber-metal waterstop) is positioned outside thus being the initial round of waterstop of the segmented joint. The waterstop product of Trelleborg B.V. has been selected and applied. This type of waterstop has been developed and applied in immersed tunnel for around 30 years (Janssen, 1978: Grantz et al., 1997). The Omega seal is the secondary waterstop; its function is to stop the possible seepage water. In HZMB tunnel to improve the water sealing effect of the injectable waterstop a series of attempts have been made; they were introduced in this paper.
Sriskandarajah, T. (Subsea 7) | Mackay, Don (Subsea 7) | Rao, Venu (Subsea 7) | Zhou, Daowu (Subsea 7) | Ragupathy, P. (Subsea 7) | Kashani, Shahryar (Subsea 7) | Power, Brian (Murphy Exploration & Production)
The Murphy Dalmatian development is one of the frontier developments in deepwater, consisting of a 6.625” (168.3 mm) / 10.75” (273.1 mm) pipe-in-pipe system in 5,831 – 6,391 ft (1,780-1,948 m) water depth installed successfully by reel-lay method using Seven Oceans reel-lay vessel. Reel-lay is a proven highly efficient and cost-effective method of pipe-lay. This paper presents some of the additional engineering performed to get all the design details right for installing the Pipe-in-Pipe system efficiently by reel-lay method. The paper presents the methods used to analyse the installation sequences, shows the results of the analysis and provides details of the solutions obtained from the analysis.
The Dalmatian South is located in Desoto Canyon Block 134. The PIP system is approximately 12 km long and will be used to connect several wells via existing subsea infrastructure to the Petronius platform.
The PIP is a sliding system with centralisers at 2.15 m intervals along its length and is designed to operate with design pressure 482 barg and design temperature 93°C.
The PIP system was reel laid and safe installation in deepwater required careful evaluation of the maximum load transfer through the centralisers, particularly as the PIP traversed the aligner wheel. Detailed evaluation of the centraliser integrity incorporated evaluation of compression, slippage, creep, abrasion and centraliser bolt relaxation. The effect of reel-lay induced plastic deformation of thermal insulation on the overall heat transfer coefficient, which needed to be maintained during operation, was also evaluated in detail design.
Waterstops were designed to be fit-for-purpose in the unlikely event of water ingress in the annulus during installation.
Numerical simulations were used to obtain axial strain ratcheting and differential elongation between the inner and outer pipes of the PIP system during installation. This information provided essential guidance on the extent of available slack in the inner pipe for connecting In-line Tee and laydown PLET.
Jukes, Paul Jukes Paul (J P Kenny, Inc / IONIK Consulting Houston, TX, USA) | Singh, Binder (J P Kenny, Inc / IONIK Consulting Houston, TX, USA) | Garcia, Jose (J P Kenny, Inc / IONIK Consulting Houston, TX, USA) | Delille, Francois (J P Kenny, Inc / IONIK Consulting Houston, TX, USA)