ABSTRACT
The utilization of EPB shields has advanced tunnel construction but there are still certain tunnelling risks such as settlements, sinkholes and movement/ vibrations to neighboring existing infrastructures (Shirlaw & Boone. 2005). In order to minimize and prevent such risks, derivation of over-excavation ratio by volume and weight of excavated material is required. Along with that, Building and Construction Authority (BCA. 2017) also enforced a regulation that over or under – excavation ratios (OERs) excavation should not exceed ±15% (over 115% or below 85%). However, in the local industry, the over-excavation ratios (OERs) reported by tunnelling contractors are based on rough estimation since factors such as spillages during the muck skips transportation, error from the crane measurement were unaccounted for. This paper reviews data retrieved from past tunnelling works, establishes a framework for back analyzing excavation data and proposes correction and bulking factors to better estimate the OERs.
