David Lees and Associates were appointed by Brandrill Limited to carry out the tender design for twin motorway tunnels at Ma on Sha in the New Terrotories in Hong Kong. 
 

The tunnels pass through decomposed granite and weathered mudstones and metasiltstones of which there is little previous experience of tunneling in Hong Kong. 
  
David Lees and Associates reviewed the clients proposed design using heavy reinforcement based on simple design assumptions, and developed more practical support criteria based on NATM techniques to provide a commercial tender advantage and practical construction solution.