Design and Construction of Ground Improvement for TMCLKL Southern Ventilation Building

The Southern Ventilation Building (SVB) is located on newly reclaimed land where 15-20 m of Sand Fill overly 15m of soft to firm silty clay Marine Deposit which was improved with prefabricated band drains.  The SVB sits directly above the Tuen-Mun Chek Lap Kok Tunnels (TMCLKL). The original design required installation of over 330 number of shaft grouted piles. Due to the presence of the tunnels the pile design was relatively inefficient and required 3m thick pilecaps. An alternative design was developed to delete the piled foundations by carrying out additional ground improvement within the soft soil layer using a combination of Jet Grouting and Deep Cement Mix using Cutter Soil Mix (CSM) and support the building on a raft foundation. The ground improvement scheme was also leveraged to reduce the temporary wall depth and shoring quantities. In order to rationalise and minimise the ground improvement quantities, the CSM panels formed a grid of orthogonal underground beams which allowed an efficient Area Replacement Ratio to be achieved.