This paper was presented at the Underground Singapore 2021, September 23rd & 24th 2021, Singapore
Organised by the Tunnelling and Underground Construction Society Singapore
- Nick Shirlaw, Senior Consultant, WSP in Asia
- Tom Henderson, Senior Consultant, WSP in Asia
- Ivan Haryono, Senior Associate Geotechnical Engineer, WSP in Australia
- Francois Dudouit, Vinci Construction Grands Projets
- David Salisbury, formerly Mass Transit Railway Corporation Limited, Hong Kong, People’s Republic of China
Tunnelling from Diamond Hill Station on the Shatin to Central Link (SCL) in Hong Kong involved twin, 1.7km long, slurry TBM drives in the direction of Lion Rock. The tunnelling encountered soil and rock grades of weathered Kowloon granite, and mixed ground conditions. A swarm of dykes of basalt and rhyolite had intruded into the granite, and the granite adjacent to the dykes was hydrothermally altered.
During tunnelling it was found that the weathering of the dyke rock and the hydrothermally altered granite had resulted in the development of swelling clay minerals. As a result, a significant proportion of the soil grades of weathered rock were ‘sticky’. The contact force and the torque applied to the cutterhead were measured throughout the drive, as was the drag at the tail of the TBM. The friction on the TBM skin was calculated from the measurements. The values were used to study the relationship between the TBM parameters and the ground conditions encountered. The data was also used to derive the Field Penetration Index and Specific Energy for each ring of advance.
The values of these two parameters are compared with the assessed ground conditions. It is found that plotting these two parameters provides insight into how the TBM and the ground interact, and how changes made to the TBM for the second drive affected the performance of the TBM in the varied ground conditions. It is found that the average unit friction on the TBM skin and tail seals reduced as the TBM passed from saprolite to mixed ground to rock.
* This paper was initially submitted by Golder Associates (HK) Ltd, now a WSP company.