Mr Samuel MOK

@ Senior Engineer, Highways Department

Topic: Experience Sharing on Concreting Practice for Critical Structures under Central Kowloon Route Project

Biography

Ir Samuel MOK obtained his first degree on civil and structural engineering in the University of Hong Kong in 1997 with further postgraduate studies on the Master of Science in Infrastructure Project Management in 2005 and the Master of Art in Public Policy Management in 2010.  Towards his professional development, Samuel had been involved in various infrastructure projects including sewerage and waterworks, Pak Shek Kok reclamation, power substations, railway and highways projects in joining various client and public sectors including CLP Power Ltd, MTR Corporation and various works departments of HKSAG Government such as Water Supplies Department (WSD), Drainage Services Department (DSD), Civil Engineering and Development Department (CEDD) and Highways Department (HyD).  His broad project management experience on major railway and roadwork projects covered various aspects amongst Lok Ma Chau Spur Line, Kowloon Southern Link, Shatin-to-Central Link and Central Kowloon Route (CKR) projects from planning, design, construction to commissioning stages.  Mr. Mok currently works as Senior Engineer of HyD overseeing the quality assurance and quality control for major construction works, in particular CKR project undertaken by the Department.

 

Abstract

The Central Kowloon Route (CKR), one of the compacted infrastructure projects currently implemented in Hong Kong, consists a 4.7 km long, dual 3-lane trunk road linking Yau Ma Tei Interchange in West Kowloon and the road network at Kai Tak Development Area and Kowloon Bay in East Kowloon. The CKR project involves construction of critical reinforced concrete structures including approach viaducts, landscaped decks, deep excavated cut-and-cover and blasted tunnels, ventilation and administration buildings. Apart from conventional concreting practice, Highways Department has spearheaded his continuous improvement towards quality management from working in collaboration with the contractors and resident site staff in developing innovative technologies in construction of integral reinforced concrete structures for its timely delivery and commissioning of the project.

 

In embracing the time, cost and quality challenges to fast-track the construction of this mega highways project within the congested urban area, deep underground and underwater stratum, various initiatives on concreting underground tunnel structures had been pursued. These include adoption of casting slipform at tunnel shaft, travelling formwork for tunnel wall stems and roof slab in achieving early formwork dismantling and adoption of BIM model containing prefabricated reinforcement bar bending schedule. Besides, admixtures and designated concrete placement locations were designed to enhance the concrete workability within the lengthy tunnel section.  As regards the concrete quality control against early thermal cracking, specifically in thick concrete structures, enhanced curing method with cooling pipes together with comprehensive temperature monitoring measures were also adopted to ensure tunnel structure durability from longer maintenance point of view. The project also explored other acceleration measures on programme-critical superstructure construction of associated ventilation buildings including use of higher strength in-situ concrete and pre-assembled table form falsework for its early removal, in conjunction with installation of modular off-site precast concrete units. In lowering early temporary rise for the high strength concrete strength, mixes with granulated blast-furnace slag (GGBS) had also been utilized which could reduce the risk of thermal cracking as compared with traditional use of pulverized fuel ash and cement mixes and exhibited as green materials to reduce the embodied carbon emission on concrete production in demonstrating the growing emphasis towards sustainability development in the construction industry.