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The captioned webinar was organised by the BD Division on 4 May 2022. Ir Paris Wong, Operation Director of Meinhardt, shared his valuable experience on a challenging project – the construction of diaphragm wall (D-wall) panels at Ma Tai Wai Road for the MTR To Kwa Wan Station.
Ir Wong first briefed the attendees on the project background and explained the key site constraints and engineering considerations. The site was close to some existing old buildings with shallow foundations or no foundation records. The ground condition of the site was complex with a thick and soft layer of alluvial deposit. Site accessibility was also challenging as the three traffic lanes (six lanes in total) of Ma Tau Wai Road were temporarily closed during the construction. After completion of the Stage 1 D-wall panels on the east side of the road, some of the settlement markers recorded settlement exceeding the Alert, Action and Alarm (AAA) triggering levels and special precautionary and mitigation measures were planned and implemented in the Stage 2 construction.
Ir Wong then introduced a 4 x 4 matrix evaluation approach including the structural and geotechnical parameters to classify the problematic areas. The geotechnical parameters were sub-divided into sub-surface ground conditions and maximum settlement induced at the buildings due to Stage 1 construction. The structural parameters were sub-divided into foundation type and building conditions.
The overall evaluation of both parameters classified the existing buildings in four Classes I to IV. The worst case i.e. the Class IV buildings required the most stringent precautionary measures including jet grouting and the installation of automatic deformation monitoring system (ADMS) to monitor the movement of the concerned buildings in real-time.
The effect of the precautionary measures was discussed, particular the construction sequence and quality control of a row of jet grouting installed in front of the sensitive buildings. The method used to increase the safety margin of the slurry pressure was also shared. The last part of the webinar was to share the additional information of the construction method and ADMS monitoring requirement and limitation.
On behalf of the BD Division, we would like to express our sincere gratitude to Ir Wong for providing this fruitful seminar for our members.