Oran Park

PROJECT OVERVIEW.

Diona won this work as a design and construct project. Having worked with Pezzimenti prior, they knew our capabilities regarding lengths of a single bore and also that Pezzimenti are capable of performing intercept bores – where a second microtunnel targets the end of the first microtunnel creating one long tunnel.

Oran Park Microtunneling Method Free Pipe Freebore in Self Supporting Ground

Pezzimenti Tunnelbore Microtunnelling Oran Park Length Diameter Ground and Carrier Pipe

Planning for an Intercept Bore

Once critical area of the project was that the sewer ran through a hill which, if open cut, would require trenches up to 12m deep over 300+ metres.

Diona engaged Pezzimenti in the concept stage of the design to see what was possible with respect to bore diameters and likely lengths of bores based on the ground conditions found in the geotech study for the Project – being solid shale.

From there, Diona selected suitable locations for shafts which were 340m apart. Knowing that it was not possible to bore that length from one end, they prepared both shafts for boring with the plan being an intercept bore.

Two tunnels create the 317m length required.

Boring commenced from the upstream end and was dry for the majority of the 197m. The completion of the first bore left a length of 120m to complete the intercept bore.

Boring commenced from the downstream end. When we were due to “break through”, a camera was sent from the upstream end to witness the cutters breaking through. The breakthrough was slightly off centre so the head continued to cut approx 5m past the break through point to ensure a smooth transition.

All rods were then retracted and the DN300mm GRP SN20,000 pipe was pushed up the bore from the top end on timber skids. Jacking / pushing load got to approx 5T which was well within the allowable jacking load.

A bulkhead was then built either end and the grout was poured from the bottom end.

Oran_Park_Microtunnelling_equipment_hook_truck_rods_power_pack

Site Setup at the 2nd shaft during operation. Crane truck lowers the drill rods into the shaft. The powerpack seen top right powers the drilling equipment in the shaft.

Pezzimenti Oran Park Microtunnelling Site Setup

Oran park Pezzimenti Tunnelbore Site layout

Pezzimenti Tunnelbore Bore Microtunneling over the shaft during drilling

Oran Park Microtunneling Overhead of Site Setup

Oran park Pezzimenti Tunnelbore Deep Shaft Intercept Bore

Shaft 1. 197m was tunnelled from this shaft first.

Oran park Pezzimenti Tunnelbore Deep Shaft Intercept Bore

The ground was solid shale and the majority of the tunnel was bored without using water.

Oran park Pezzimenti Tunnelbore Deep Shaft Intercept Bore

The depth for the shaft shows clearly why microtunnelling was the obvious method over open cut.

$Oran Park Pezzimenti Tunnelbore Intercept Bore from each shaft\$

Looking down on the length of the microtunnel from shaft to shaft. (Left) Above the 120m intercept microtunnel shaft. At the top right the stockpile of GRP SN20,000 pipes which would later be sliplined into the tunnel can be seen. (Right) Above the shaft of the 197m microunnel. The proximity of the dam to the second shaft can be seen top right.

Oran Park Pezzimenti Tunnelbore Microtunneling GRP Carrier Pipes