Pavement Reconstruction.
A significant innovation for the reconstruction of rural roads in Australia has been realised through the use of the impact roller.  The impact roller has been used on a regular basis by a number of local councils on rural roads where there are no sewers or other services below the pavement, while more caution is required in metropolitan areas due to the myriad of shallow underground services.
One of the biggest problems for rural roads is localised or more widespread failure due to poor subgrade conditions.  The major benefit of the impact roller is that the subgrade can be improved from the surface, without the need to remove any material.  Sealed pavements and even concrete stabilised base courses are broken up under impact rolling, leaving a material suitable as the new sub-base.  Sufficient settlement is usually induced by impact rolling, so that after shaping and conventional rolling, a new base course and wearing course can be laid without further earthworks.

Agricultural Sector
In the Australian agricultural sector, impact rolling has been utilised since the early 1990’s to address problems with leakage from water storages and channels for the cotton and rice industries.  More recently, impact rolling has been successfully deployed in the construction of pads for beef cattle feedlots, where environmental constraints require properly engineered facilities.
The ground improvement generated by the “square” impact roller in the agricultural sector offers significant environmental benefits.  Water loss through permeation from water storages and channel banks is reduced, which reduces the impact on groundwater and soil salinisation.  The reduction in irrigation water consumption improves the environmental sustainability of high water-use crops.

Brownfield Sites
The widest application of the “square” impact roller in Australian metropolitan areas relates to the redevelopment of former industrial sites.  Sometimes these “brownfield” sites are re-used for industrial purposes, but often they are developed for residential use, which generally requires more remediation due to a more sensitive end use.
In common to most existing industrial sites, the land has been filled.  Generally, this fill has been required to provide a level base for slabs and pavements, but often more marginal land, zoned for industrial use, has had deeper amounts of fill placed over sometimes poor, soft or weaker soils.  Over decades of use, fill materials have become contaminated and waste materials have been buried on older industrial sites.  The challenge for the remediation team is to find a solution that is environmentally sound but also realising a cost-benefit to the developer.
Impact rolling provides an alternative to re-engineering existing fill.  Materials that are environmentally suited to retention on site, but that may otherwise need to be taken off site if excavated, can often respond to impact rolling to produce suitable subgrade conditions.

Mine Waste Tips
The mining sector was an early advocate of impact rolling to reduce the incidence of spontaneous combustion in coal stockpiles, a use that still continues in South Africa today.  In Australia, the “square” impact roller has been utilised on numerous mine sites to improve mine haul roads, in the construction of tailings, dams and to compact the capping over waste rock cells.
The most recent work undertaken by the “square” impact roller at a mine site is, however, a non-engineering application.  On the hard rock open cut gold mines, spoil is carted by 300t haul trucks and end-tipped to form large waste rock tips.  The trucks drive up onto the tip head and then turn through 180̊ and reverse to the edge to dump the load.  During turning, the truck tyres are particularly prone to damage from protruding hard sharp rocks.  The cost of truck tyres is the largest single cost to the mining operation of the largest open cut gold mine in Kalgoorlie, Western Australia.
Impact rolling on the tip head to “rubblize” the rock has the effect of breaking down larger sharper rocks, with an associated reduction in abnormal tyre wear.  The “square” impact roller module is specifically modified for such mining applications.

Landfills
The provision of adequate landfill void space in and around existing and developing cities is an ever-growing problem.  As a general rule, landfill operators utilise a unit that combines compaction and dozing, which compacts while it traverses and spreads the fill material and can also spread soil cover.  While this approach generally serves the purposes for which it is deployed, the extent of future gross and differential settlement that occurs in refuse tips is still substantial.  When such sites are later turned over to, say, recreational use, problems frequently arise with differential settlement and associated risks to site users.
The “square” impact roller has been utilised on numerous landfills, particularly in Victoria, Queensland and Western Australia, as well as other Australian states and overseas.  Due to the extremely variable and heterogeneous nature of waste, and difficulties associated with testing such materials, there is a limited amount of quantified output from impact roller work on landfills, most users relying on observational techniques to substantiate the impact roller’s effect.
Two locations were selected from the data set to illustrate the variable response that can be expected on such sites.  The landfill had a soil capping of approximately 1m thickness overlying the waste material and the trial alignment was subjected to 90 passes.  Modest settlements of 200mm to 250mm were recorded after approximately 40 passes where the fill was shallowest (less than 3m thick).  However, where the fill was deeper than 5m, a maximum settlement of approximately 700mm was recorded after 90 passes.  The use of the impact roller on landfills at various times during the placement of the fill is likely to provide additional landfill capacity during the filling process.  Initial cost estimates indicate that this is an attractive scenario, particularly as the cost of waste disposal continues to rise.

Land Reclamation
Land reclamation projects generally take the form of creating new land at the edge of a water body or raising land that is at or close to the water table or sea level.  Frequently, the fill material is sand that is dredged from the sea or river floor, usually placed hydraulically into or onto the area being reclaimed.  The “square” impact roller has been used on many such projects to produce a soil “raft” of significant thickness to reduce differential settlements and accommodate infrastructure.  This has been undertaken in most Australian states, in the United Kingdom, Hong Kong and the Netherlands.

Test Methods for Monitoring and Validation
Many different test methods are utilised to verify the effects of impact rolling, varying dramatically from site to site and project to project.  Some projects, in fact, include no quantitative testing, relying on anecdotal and observational evidence.  It is considered that this variation is generally attributed to a combination of the client’s, designer’s and/or geotechnical engineer’s preferences and experience with impact rolling, the readily available test equipment budget constraints, the site’s location and/or particular site conditions.