Geotechnical Engineering Online Library

In land scarce Singapore, the development of a comprehensive and efficient underground public transport system is the key to a sustainable transport system. This has resulted in many tunnels being built in densely urbanized areas and at close proximity to buildings and infrastructures. The tunnelling effects on these adjacent structures can be detrimental as problems such as pile settlement and passive loading on the piles could arise. The construction of large scale infrastructure projects such as Circle Line has opened up enormous scope for tunnelling and underground works in Singapore, which offers a great opportunity to study the response of piles to tunnelling. Two case histories are presented and involved the monitoring of 200 buildings located within the influence of tunneling along Circle Line (CCL) 3, 4 and 5. More than 3600 building settlement markers were analyzed and the resulting pile head settlements due to tunnelling were compared with surrounding ground surface movements. The results of the full-scale instrumented piles subjected to the effects of twin tunnel construction on adjacent groups of bored cast in-situ piles are also discussed.

The growing demand for public and sustainable transportation in heavily urbanized areas like Singapore requires construction of an increasing number of Metro Lines. Complicated technical challenges are associated with such an activity and settlement prediction models play a key role in assessing the tunnelling-related risk assessments and planning mitigation techniques. Although a significant amount of research has been performed to study the settlements induced by side-by-side twin tunnels, the settlement prediction of stacked tunnelling has been, relatively, limited. In this paper, stacked tunnelling induced settlements are predicted using 2D numerical simulation. The extensive data from the instrumentation measurements collected during the construction of a stacked configuration tunnel in Singapore Downtown Line MRT tunnels have been used to study the validity of the principle of superposition for stacked tunnels. Key observations are presented by comparing empirical, numerical and actual field settlement data. Using the Monte-Carlo simulation technique, the empirical trough parameter is back-calculated to fit the actual settlements observed in Kallang formation. This could be used for future settlement predictions in similar ground conditions.