AMC’s customised fluid system eliminated re-drills for piling project in Canberra, Australia

A light rail project in Canberra utilised AMC’s customised drilling fluid system and on-site support to successfully eliminate re-drills, problems caused by water incursion and manage environmental impact.

Challenge

AMC’s client was completing a significant bridge piling project for a new light rail system being built in Canberra, Australia’s capital. In the past, the client had not used drilling fluids. The client had been experiencing hole caving due to water incursion into the hole due to the close proximity to a water course.

The clients biggest challenge was being able to keep the hole open to allow for the running of the steel reinforcement and the grouting procedure. In previous operations the client had regularly experienced washouts and hole collapse due to water entering and affecting the formation, particularly when encountering swelling and fretting clays.

In the project, each hole drilled required a depth of at least 23m deep and 900mm wide for the steel reinforcement to be installed correctly.

Results

• Successful completion of 1 hole per day (drilling with mud system, placement of steel reinforcements and grouting)
• Eliminated re-drilling, lost time and associated costs
• Prevented water incursion causing borehole collapse and delays to project continuation
• Minimised risk to the local waterways
• Minimised costs of drilling fluids through recycling.

Solution

Due to the close proximity of the water course, the project needed to have an environmental management plan to reduce the risk to the local waterways. AMC designed a customised, bentonite free, and environmentally acceptable drilling fluid system tailored specifically to the project. The system provided hole stability, inhibition and filtrate control enabling increased productivity and ensuring minimal risk to the environment. AMC’s chemists conducted due diligence on the drilling fluid, ensuring that it did not affect cement bonding with steel.

It was decided that AMC would fill the drilled piling holes with a pre mixed fluid system straight after drilling to stabilise the hole, prior to running the steel casing and grout. The bentonite free fluid system was mixed in multiple 5,000L tanks, which were then gravity fed directly to the hole after the drilling had been completed. The holes were 900mm in diameter and on average 23m deep, with some up to 25m deep.

AMC’s tailored system included AMC SHALEHIB ULTRA™, an amine based product that provides superior shale and clay inhibition; AMC EZEE PAC R™, a highly dispersive high quality polyanionic cellulose polymer used for viscosity and water loss control; SODA ASH and MAGMA FIBRE. It also included AMC’s purpose built CIVIL MUD XTRA™. AMC CIVIL MUD XTRA™, a specialised high performance, highly water soluble cross-linked synthetic polymer exclusively developed for the construction and civil engineering industries. AMC was able to reduce costs and mixing times by recycling the fluid system via the recycling system with the same mix used for the first three holes.

Project Outcome

AMC’s custom designed bentonite free drilling fluid system provided critical borehole stability, controlled filtrate and prevented clay and shale sloughing.

Throughout the duration of the project, productivity increased, costs were reduced, delays were minimised and environmental impact was managed. Additional operational efficiencies were achieved;

• Zero re-drills were required, reducing the project timeframe and associated costs
• The water table was unable to enter the drilled piling holes preventing borehole collapse and further delays to the project
• The drilling fluid system was environmentally acceptable and had minimal impact on the local environment
• The recycling method reduced costs of drilling fluids
• The client successfully completed a record of one hole per day which included drilling and managing a mud system, placement of steel reinforcements and grouting.

The client was extremely happy with the methodology, on-site support and products. They advised AMC that they now have the confidence to use drilling fluids more often as it will give them a competitive edge when tendering for future projects. All stakeholders involved in the project were impressed with the minimisation of environmental harm and productivity increases.

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