With PERI know-how and support for the best architectural concrete quality
7 July 2017
Since 2010, PERI has been supporting the construction of the 6 km long underwater tunnel section of the fixed link between Hong Kong and Macao / Zhuhai with the provision of two forming machines. The excellent cooperation has led to additional orders: PERI has provided professional engineering services and project-specific formwork solutions for achieving the best possible architectural concrete results as well as large time-savings during construction work for the tunnel portals and two operation buildings.
The mega project to create a 35 km long road between Hong Kong and the Chinese mainland started a few years ago in China. In the area of the approach flight path of the Hong Kong International Airport, Check Lap Kok, the connection runs through an underwater tunnel. PERI developed two hydraulically operated forming machines to produce the individual segments for this 6 km long tunnel which was finally completed in May 2017. The extremely positive, successful cooperation resulted in the China Communications Construction Company Ltd. (CCCC) commissioning the Weissenhorn-based company to deliver additional engineering work and formwork material. Since the end of 2014, PERI has therefore been developing comprehensive formwork solutions for the tunnel entrances; just over a year later, the company received the order for supplying the formwork solutions for the operations buildings on two artificial islands in the Southern Chinese Pearl River Delta. For the customer, the most important requirement was to achieve a first-class architectural concrete quality.
At the transition area leading down from the bridge, six lanes with a 3 % longitudinal gradient disappear into the tunnel whereby two artificial islands were created in order to accommodate these crossover points. For the transition structures, it was necessary to realize the up to 15.50 m high side walls of the entrances with a clearly structured joint and tie arrangement as well as ensuring they are permanently impermeable to water. In addition, enormous wave breakers were put in place around the islands.
Since autumn 2015, multi-storey operation buildings have now been constructed on the two artificial islands which reach a size of almost 100,000 m2 for each respectively. In the structure at the west end of the tunnel – which has around 19,000 m2 of usable space – machine rooms, fire-fighting equipment and office space will subsequently be accommodated; with one basement level and three above-ground floors, this building is almost 20 m high. At the eastern exit of the tunnel, a 23.60 m high, 4-storey building has been realized. In addition to the service and equipment areas of the tunnel operator, two storeys with retail areas are also located here. Furthermore, an exhibition has been planned for the top floor which will feature the development and realization of this mega project.
As the Chinese client had had little experience with the construction of architectural concrete structures, defining the required fair-faced concrete results was to be decided on at the start of the planning. The contractual partners selected Architectural Concrete Class SB 4 as the decisive quality feature in accordance with the Architectural Concrete Reference Guidelines published by the German DBV and VDZ associations. Subsequently, all project participants analysed any required adjustments to the usual construction methods that might be needed on the jobsite itself. The PERI experts drew up numerous suggestions for improvement in order to cost-effectively and efficiently achieve the previously defined architectural concrete results.
The usual construction methods for different areas needed to be modified including, among other things, the intersections of main and secondary beams. On site, it is customary to concrete slabs and beams in one pour. By contrast, during the planning process it was decided to concrete all components separately and, in addition, use prefabricated reinforcement cages. The aim of these measures was to facilitate the efficient use of system formwork and to significantly accelerate the construction time.
After the realization of these foundations, planning the formwork and shoring required for the walls, columns, main and secondary beams, slabs, balconies and cantilevered parapets took place. As far as possible, the planning team used PERI system formwork in order to optimize the cost-effectiveness of the construction work. Due to the in part curved shapes, PERI engineers also designed special formwork for numerous components.
The fabrication of the up to 15.50 m high reinforced concrete walls, which separate the two lanes in the area of the tunnel entrances, is carried out with mobile PERI portal formwork carriages. This movable solution includes a project-specific VARIO GT 24 Girder Wall Formwork, which enabled the construction team to realize the required, clearly structured joint and tie arrangement for the walls. Moreover, the use of the SK Tie Technology provided the high degree of water tightness required throughout. Also for the massive breakwater, the construction team used a mobile PERI wall formwork solution.
For the large-sized columns, slabs, cantilevered balconies and parapets, PERI developed formwork and scaffolding solutions based on standard components of various PERI systems. The Weissenhorn-based company also planned, produced and supplied project-specific solutions with timber formers and a range of cut-to-size plywood panels for the more complex-shaped areas and components. All system components and panel cuts used were delivered to the construction site just-in-time and assembled on site according to the construction progress.
Through the combination of competent PERI engineering, efficient system formwork, precisely matching special formwork and continuous support along with quality control of all work carried out by a PERI supervisor, the contractor was able to achieve a reduction in the construction time of around 6 months compared to his primary planning.
Source: PERI GmbH