Unsealed Road Grading Your Questions Answered

What is maintenance grading? Council grades unsealed roads to reshape and re-compact the road, to reduce lumps and bumps and ensure that the road will shed water away from the centre after rain. A grading maintenance schedule is adhered to every 6 or 12 months, depending upon the road condition, the amount of use and the effects of wet weather. What is gravel re-sheeting? Gravel re-sheeting is when new gravel is added to the road. This is due to the severe deterioration of the road that can compromise the safety of road users. The gravel is generally laid in loose layers and then trimmed and compacted using a grader, water cart and roller so that the new road generally has a depth of about 150mm. Why does my road lose gravel? Gravel wears away over time due to the combination of the environment (wetness and dryness), the type and volume of traffic and excessive traffic speed. Softer gravel rock will wear away faster than harder gravel rock.

Unsealed roads are made up of a mixture of gravel of differing sizes, clay and soils. This mixture affects the strength of the pavement and how long it will last. The rock gives the pavement strength and the clay and other soils binds the gravel together.

Where possible, the grader drivers will recover as much of the loose gravel as they can during the grading of a road and turn it from the edge back into the centre of the road.

Why is does my road appear to be shrinking? As the road wears down over time the edges of the road pavement will wear and the width can become less. Road edges can be weakened and deteriorate due to wet weather, vegetation encroachment and by motorists driving close to the edge of the road and cutting corners on road bends.

Width can also be affected over long periods due to grading when additional gravel is not applied. When new gravel is provided on a regular basis the loss of pavement width is significantly reduced. Can tyning the road help to remove potholes and corrugations? Tyning is a term used for ripping up the road with a grader. The process allows the road material to be reshaped to reinstate the crown (the high point at the centre of the road). Whilst tyning can help repair potholes by providing a smoother surface, it is only appropriate if there is enough gravel on the road surface to be ripped up and reshaped. Most of Council’s unsealed roads have limited gravel so this process is not used very often. Tyning is when the tynes of the grader dig into the road surface and brings material from the lower part of the road pavement to the surface (somewhat like ploughing). The road is then graded and rolled as normal. When there is limited gravel in the pavement surface, this process only brings clay and other soil to the surface which further diminishes the pavement by dispersing any gravel that does exist.

Why is weed spraying performed prior to grading? Vegetation encroachment can weaken road edges so spraying the grass in table drains (and road shoulders) to kill off the grass in this location will reduce encroachment into the road. It also reduces the likelihood of vegetation being incorporated into the road during grading activities.

Can the road be strengthened by road stabilisation? Yes, road stabilisation is a process that makes the clays and soils stiffer and stronger through the introduction of lime, cement or other engineered additives. This makes the road more resistant to wear, however the materials are still susceptible to the environment (wetness, dryness and traffic), and when stabilised roads begin to deteriorate, potholes are typically harder and sharper which increases the likelihood of vehicle damage.

The extent to which the life of an unsealed road pavement may be extended through stabilisation is extremely variable depending on the existing materials and may vary from a couple of months to a couple of years.

Council currently practices road stabilisation on sealed roads only, where the pavement is protected by a bitumen seal.

The introduction of stabilisation on unsealed roads is costly and can only be undertaken if there is sufficient gravel on the road for the strengthened clays to actually bind together. It would only be practical to use stabilisation in partnership with gravel re-sheeting, however this would significantly increase the cost of gravel re-sheeting.

How about improving the quality of the gravel? Council’s quality of gravel varies across the local government area. We extract ridge gravel from approved mine sites on local properties, and we supplement this with materials from commercial hard rock quarries, reuse of excavated sealed road materials and recycled crushed concrete.

Extracting quarried gravel can be an expensive operation. The harder rock results in a better quality outcome however it is more expensive due to the blasting and crushing activities within the quarry.

Why is my road dusty? Unsealed roads will always generate some level of dust, because they are made up of gravel, clay and soils and are significantly affected by the environment and driver behaviour.

In very dry conditions roads will become more susceptible to dust generation through the wearing of the clays in the road. When motorists drive at an inappropriate speed (particularly heavy vehicles) excessive dust can also be generated.

My road is slippery. Unsealed roads can be significantly affected by the environment and will be slippery during wet conditions. The degree of slipperiness is often dependent on the quality of the remaining gravel present. Engaging 4WD is highly recommended.

Recently graded roads can become boggy or slushy if impacted by a rain event during the grading works or potentially up to 2-3 weeks after the completion of grading. Drying out the road with sunshine and time is the most effective treatment.

For more information visit pmhc.nsw.gov.au contact Council on (02) 6581 8111.