Heavy Patching

Stabilcorp is experienced in all aspects of Gravel and Asphalt Heavy Patching and recognise that all road failures should not be treated or repaired the same.

For example a failure within a subgrade is repaired differently than that of a base course failure.

Identifying the type of failure is an important first step in a successful repair process.

At Stabilcorp we undertake pavement testing to identify the mode of failure and recommend to the client the design and remediation treatment required. This approach ensures that the repair to the failed area of road will provide the client with value for money and longevity of the repair.

The types of failures and remediation options available for Gravel Heavy Patching are;

Subgrade Failures

These occur at depth and require removal of base and sub-base to expose the failed subgrade layer. After testing a remediation treatment can be provided which may include in-situ stabilizing to improve the CBR of the subgrade.

One of the methods employed to expose the subgrade layer and reutilises base/sub-base materials is the process known as side casting which recycles existing construction materials for reuse in the remediation. This method provides significant cost savings to the client.

Another method is to simply remove and replace the base and sub-base to waste, inspect the subgrade layer for strength and replace with new compliant gravel materials. This method is typically used for patches ranging from 10m2 to 100m2.

Sub-base Failures

These occur at the sub-base level and can be attributed to a non-complying gravel product that was used in the original construction or ingress of water. The methods to improve the sub-base layer involve either;

  • Removing the base course via the side casting technique to expose the failed sub-base layer, followed by in-situ stabilizing of this layer.
  • Introducing a complying overlay of gravel mixed in with the sub-base layer resulting is an improved sub-base material which may not require any more treatment. The base layer is then reinstated on top of the sub-base layer.
  • Side casting of base material followed by the removal of the sub-base layer to a stock pile for reuse for gravel re-sheeting purposes. The base course layer is then graded into the excavation forming a new and improved sub-base layer. This layer can be stabilised or left in its exisiting state depending on the quality of the base material.

Base Failures

These occur at the base layer, typically at the top 100mm of the pavement formation. The methods to improve the base layer involve either;

  • In-situ stabilizing of the base (and may include part of the sub-base layer) to provide an impermeable layer to minimise ingress of water.
  • Provision of a gravel overlay over the base layer and in-situ mixing of gravel layer into base followed by in-situ stabilising of mixed layer.

The use of asphalt in heavy patching is typically used on highway applications or where there is a need to minimize traffic disruption due to the speed of application.

Generally, 100mm – 200mm of material is milled out and reinstated with an asphalt layer or layers. This process provides a strengthened base layer in a short period of time, however is much more costly than gravel heavy patching.

Stabilcorp is highly skilled in this area of road repair and maintenance and frequently utilises the above remediation techniques for Councils and RMS clients in their Heavy Patching repair programs.