Haul roads
When managing large-scale construction or industrial projects, ensuring the integrity of the ground beneath heavy machinery is a given. Haul roads are specifically designed to address this concern. They provide a strong, stable surface for vehicles to drive on, stopping damage to the underlying terrain. In this article, let’s learn more about the haul roads.
What are haul roads: definition, types and importance in construction
Haul roads are specially designed flat roads for the movement of materials, machinery, and labor within construction sites and mining or quarrying operations. Haul roads, also known as haulage road or haul track, evenly distribute the weight of heavy equipment and reduce the risk of settling.
By enhancing equipment performance and safety, it stops rutting, erosion, and damage to the surrounding environment. These roads serve as the primary transportation for hauling extracted materials, such as ore, waste rock, or aggregates, from the extraction site to processing facilities, stockpiles, or transportation terminals.
What are the materials used to construct haul roads?
- Crushed Aggregate Base (CAB): Made from crushed rock, gravel, or a mix of natural and processed materials, CAB improves load bearing capacity. It is also inexpensive and provides proper drainage.
- Geosynthetics: Geosynthetics like geogrids or geotextiles reinforce the haul roads, distribute loads evenly and stop the soil from shifting.
- Asphalt or concrete: Provide a durable, smooth surface.
Importance of haul roads in construction
The meticulous design, construction, and management of haul roads is significant as it affects the material haulage costs. Hence, it is essential for minimizing cycle times, fuel consumption, tire wear, and overall cost per tonne hauled. A well-constructed haul road strengthens vehicle performance. For instance, reducing rolling resistance (RR)—the force opposing a vehicle’s motion—can boost productivity. A compact, smooth road reduces RR, which in turn improves fuel efficiency. It also increases vehicle speed on surface haul roads by 16% to 25% with just a 1% reduction in RR.
Design considerations of haul roads
Well-designed and maintained haul roads are essential to minimizing on-road hazards and to boost productivity in mining operations.
Understanding load-bearing capacity
Since heavy equipment and materials used in mining and construction operations subject haul roads to significant dynamic and static loads, understanding load-bearing capability is essential. To make sure that haul roads can sustain these forces over its lifetime, engineers need to evaluate the expected loads, taking into account the weight of the supplies, machinery, and other environmental effects.
Types of loads
Various types of loads, including dead loads (the weight of the road), live loads (the weight of the equipment and materials), and environmental loads (such as wind and snow) must be considered. A thorough analysis of these loads enables to determine the appropriate thickness, reinforcement, and overall configuration of the haul roads.
Drainage and water management
Standing water on haul pads leads to erosion and surface degradation. Subsurface drainage is necessary to stop water from infiltrating and saturating the base materials. It also controls rutting, erosion and surface failure. Proper stormwater management systems include components like gutters, downspouts, storm drains, retention and detention ponds, and permeable surfaces.
Stabilization techniques
An essential component of the design process is the stabilization of road materials to improve the road’s strength and functionality. Adding polymer additives, hydrated lime, and bitumen emulsions improve the performance of the road.
What are the types of haul roads?
Temporary haul roads
Temporary haul roads are constructed for short term use. Once the project is completed, these roads are either removed or repurposed.
- Gravel or Aggregate roads: Compact gravel or aggregate material provides a stable surface. Gravel allows water to drain, leading to erosion control.
- Geotextile roads: Geotextile fabric reinforces the soil and reduces settling.
- Matting Systems: Interlocking mats (e.g., steel, plastic, or wood) create a temporary surface and are ideal for environmentally sensitive areas.
Permanent haul roads
Permanent haul roads are designed for long-term use and often utilize high strength materials like asphalt to withstand ongoing operational demands.
- Concrete roads: Reinforced concrete provides a durable and long-lasting surface.
- Asphalt roads: Asphalt pavement offers a smooth and durable surface.
- Steel-Reinforced roads: Steel reinforcement adds strength to concrete or asphalt pads and are extremely durable.
Specialized haul roads
- Environmental roads: Designed to shield against contamination and protect sensitive ecosystems. Often made from durable materials such as geotextiles or composite mats.
- Heavy-Haul roads: Engineered for extremely heavy loads (e.g., mining equipment).
- Offshore roads: Designed for marine-based operations (e.g., oil rigs, drilling platforms).
- Access Roads: Transitional pads connecting haul roads to work sites.
Construction process of haul roads
The construction of haul roads starts at an early phase of a mining project and involves careful planning.
Site Analysis
This includes evaluating the topography, soil composition, drainage patterns, and geological characteristics. A detailed geotechnical survey is also necessary. Understanding these aspects helps make decisions about the best location, size, and design of the haul roads.
Grading and Preparation
The next step involves leveling the land to achieve the desired elevation and contours of the haul roads. Heavy machinery is used to cut and fill the terrain, securing a level surface. Proper grading is vital as it blocks water pooling on the roads, which could otherwise lead to erosion or flooding.
Base layer installation
The base layer which serves as the primary support for the roads is laid using a spreader to make sure even distribution of material. It is followed by compaction using a heavy roller.
Binder layer application
A binder layer is installed to bond the base and the surface layers. A thin application of asphalt or binder material is compacted to achieve optimal density and strength.
Surface layer paving
The surface layer, which directly supports vehicle traffic, is paved. It is applied evenly to provide a smooth and durable driving surface. It is the topmost layer offering protection against weather, load stresses, and wear.
Use of geosynthetics in haul roads
Geosynthetics like geocells, geogrids and geotextiles are widely used for soil stabilization and road reinforcement in mining operations.
An application of geocells is its use in creating a “beam effect.” ie. boosting load capacity and evenly distributing vertical pressure horizontally across the road’s width. The effect is achieved when geocells are integrated into the base layer of a haul road. This maintains a reliable and durable solution for navigating challenging terrains, providing robust support for the heaviest haul trucks. The beam effect also enhances the overall stability and longevity of haul roads, mitigating issues like washouts and sinking.
Furthermore, the incorporation of geocells in haul roads locks solids and aggregates in place, providing soil stabilization and reducing maintenance needs in mining.
Geotextiles separate the subgrade soil from the aggregate layer, and stop mixing, which could weaken the structural integrity of the roads by causing compaction and uneven settling. Geotextiles also quickly divert the excess water from the road structure, limiting the weakening of the road foundation and leading to erosion control. On the other hand, high tensile strength of geogrids allows it to resist deformation under heavy loads, ensuring the integrity of haul roads. It also provides reinforcement to the subgrade layer, reducing the risk of surface degradation.
What are the environmental impacts of haul roads?
Understanding the effects on the environment is essential to reduce negative consequences for ecosystems and communities.
Resource Depletion and Land Use
Haul roads require the extraction of natural resources and a significant energy use, which results in land degradation and habitat loss. Careless use of resources like timber, heavy metals, and fossil fuels causes deforestation and the exhaustion of finite resources.
Water Pollution and Erosion
Haul roads significantly impact water quality, primarily through erosion and runoff. During rainfall or snowmelt, sediments from unprotected haul roads wash into nearby waterways, leading to sedimentation and pollution.
Energy Consumption and Carbon Footprint
The operations associated with haul roads require substantial energy input, particularly through the use of heavy machinery. This contributes to the carbon footprint of construction activities, exacerbating climate change impacts.
Mitigation Strategies
Implementing green construction methods, such as using recycled aggregates from reclaimed asphalt pavement(RAP) or recycled concrete, minimize disturbance to surrounding areas. Effective stormwater management practices, such as silt fencing and riparian barriers, are essential to control runoff and protect local water sources from contamination. In- situ stabilisation enhances strength, durability and load-bearing capacity. Bioswales, which are vegetated strips that filter rainwater, serve as an innovative solution to improve the environmental performance of haul roads.
Maintenance of haul roads
Regular maintenance activities, such as grading, resurfacing, and repair of damages, are essential for keeping haul roads in optimal condition. Routine maintenance is conducted at regular intervals of 10 to 21 days to address minor surface deterioration, which can increase rolling resistance and reduce functionality. Operators must as part of safety processes work on assessing the condition of the haul roads and surrounding components, to reduce rutting and extend the overall lifespan of the road.