Water Management Strategies

Pressure Grouting

Pressurised grouting techniques used in civil and mining projects to manage groundwater have been developed since 1802. Ongoing demand for water control systems supported further development and the first application in a mining project was documented in the latter half of the 19th century.

“Grouting was a term used mainly by masons and bricklayers until it was adopted by tunnel miners for the method of injecting a lime slurry behind cast-iron liners, invented by Barlow in 1864 and improved by Greathead in 1886. The term then spread to cover a variety of injection processes.”

 Aarsleff Ground Engineering: Grouting – The History  https://aarsleff.co.uk/company-news/grouting-the-history/

Whilst largely unheard of outside engineering circles grouting has provided solutions to many projects relied on by society today. Refinement and application methodology for grouting has developed further over the last 120 years to be used to control potable water and is a normal feature of constructing of water storage dams for the protection of municipal water supplies. Projects dealing with large water inflows from subterranean water bodies (aquifers) or  surface water bodies (lakes, rivers, seas) are not uncommon with tunnelling becoming a substitute to bridges in large cities like Sydney and Melbourne. Grout use has been developed to ensure protection of groundwater quality and the typically uses neat, fine silica cement grout, the same ingredient that is used in making typical household cement drinking water storage tanks. The use of grout has many applications associated with groundwater protection and control. Correct use of grout is a safe process that is commonly used in establishing water extraction bores in Australia, the method is so successful that there is a push in the irrigating states of America to legislate the use of grout in all water extraction well construction in order to protect aquifer quality.

“The National Ground Water Association believes that the grouting of water wells is an effective and necessary measure to protect public health and the quality of our groundwater supplies.”

National Ground Water Association – Position Paper – Grouting of Water Wells

Attached are two papers published and industry reviewed relating to grouting application and suitability in various situations.

The paper on grout application at Ernest Henry is provided as an example of grouting being used to control groundwater inflows at high pressure and flow rates in fractured rock, Ernest Henry mine managed groundwater that had greater inflows and higher pressure than those measured at the Bird-in-Hand Gold project.  The main water bearing unit at Ernest Henry is the Gilbert River formation consisting of semi-consolidated, weakly cemented, quartz sand and gravel with a typical thickness of about 5 m, this formation reoccurred over a 300m strike. Eight specific aquifers were identified and 18 separate grouting zones were managed to control mine water inflows. A comparison of the groundwater properties between Ernest Henry and Bird-in-Hand Gold are in the table below.

Parameters Ernest Henry Bird in Hand
Inflows (l/s) 75-100 10-60
Pressure (kPa) 3500 1400
Temperature (oC) 49 20

 

Ernest Henry achieved greater than 97% control of groundwater inflows to a reduced inflow level of less than 2l/s. To ensure that a conservative approach is taken to understand groundwater impacts  of the Bird-in-Hand Gold project on regional groundwater, the scenarios of not using any grout and using grout with a varying effectiveness have been analysed to understand the impact on water users.  All investigation work is undertaken to demonstrate protection of groundwater and compliance with the Western Mount Lofty Water Allocation Plan. It is proposed to use grout to control groundwater inflows and protect groundwater quality as part of the mine groundwater management plan.

The second paper provides and over view of grouting application and techniques used and applied at various stages of mining projects.  The paper was published in the International Journal of Mine Water, vol 5 (4) in 1986. While the paper is 31 years old it shows that the application of grouting is not a new concept and the use of grout to control water in mining projects is tried and tested across a range of applications.  It also provides for a description of investigation methods that are required to understand aquifer properties.  The research undertaken to understand the aquifer associated with the Bird-in-Hand Gold project can be reviewed in the BIHGP Groundwater Assessment (Link) on the Groundwater page of the Bird-in-Hand project.

These papers are by no means the only documents available on the topic of grouting, the application of grout for use in groundwater control is a well-documented process and additional papers are available through industry bodies, conference proceedings and can be found by a search on the internet.

To access the grouting papers please click the links below.

Groundwater Management Control

Managing High Pressure Water Inflows at the Ernest Henry Underground Mine