Holdfast Training Services Trial Blog

Just a quick blog to give an update on what is going on on my site at the moment as I head towards the culmination of my Ph 2 attachment.

As a reminder I am employed in the engineering team delivering the Northern Portal cut and cover structure in Melbourne from which two 16m dia TBMs will be launched early next year.

1st TBM following factory acceptance (manufactured across Europe and China)

We have finally got rid of the dirty and messy piling sub contractor on site, which has opened up some real estate and allowed the installation of the temporary propping system to begin in earnest. The planning and installation of the temporary propping system has been my primary area of responsiblity and so far we have installed five 40m props across the excavation, which has allowed us to start excavating beneath “roof level”

Having initially opted to use 35T excavators within the excavation, these have quickly been swapped out for 16T machines, due to slow productivity as a result of the machines getting bogged and the confined nature of the work area beneath the props.

16T excavators working beneath props

Due to hold ups in the piling works as well as changes to the design and sequencing of works (we are currently constructing using a pre-IFC design) a lot of my time is being spent managing the logistics of receiving thousands of tons of steel  on site (not necessarily in quite the required order) and ensuring the sub-contractors are kept abreast of design changes and constructing to the latest design.

One of many deliveries arriving on site

During installation of first props

During the prop installation, strain gauges are being fitted to a number of props, and settlement monitoring stations have been installed around the box, as well as prisms on the capping beam to detect any movement throughout the works.

Strain gauge installation

The data collected from these systems is monitored daily and trigger levels have been prescribed to provide alerts should unexpected movement or stresses in the props be detected. We have to submit a new permit to excavate every 24hrs which takes into account the information collected through our monitoring program.

The model below gives an indication of what the portal will look like once all three level of propping have been installed.

The TBMs are arriving in February and by that point we need to have reached full depth, poured the base slab and removed the second and third level of props, so it’s a busy run up to Christmas….