Dry Soil Mixing addressed settlement and stability requirements

The project

A new bridge over Emigrant Creek South, part of the Ballina Bypass, Pacific Highway upgrade, required approach embankments to be built over very soft soils needed a foundation to limit settlement and ensure stability.

The challenge

The Richmond River floodplain south of Ballina has deep, soft soils, which are vulnerable to large and variable settlement. These needed to be stabilised and strengthened, to allow construction of the embankments and to reduce differential settlement at the transition between the embankments and the bridge structure.

The solution

Dry Soil Mixed columns provided a ground improvement solution that met the settlement criteria specified by the client whilst being cost-effective. Keller installed a total of 35,000lm of columns in an interlocking grid beneath the embankment footprints and side slopes. A significant advantage of the solution was that it allowed construction of the embankments soon after treatment was complete, minimising delays to the programme. Treatment was verified using pull-out tests, coring and UCS tests on recovered samples. Results showed that both strength and modulus of the soil mixed columns met the design criteria.

Project Facts

Owner

RMS

Main Contractor(s)

Ballina Bypass Alliance (Leighton Contractors, Coffey, SMEC, AECOM and RMS)

Keller Business Unit(s)

Keller

Engineer

N/A

Download Project Sheet

Kf Ref 281 Rev01 Ge Ballina Bypass