Haul roads
When large -scale construction or managing industrial projects, ensuring the integrity of the ground under heavy machinery is a given. Haul Roads are specifically designed to remove this concern. They provide a strong, stable surface to drive vehicles, which prevent damage to the underlying area. In this article, let’s learn more about the roads.
What are haul roads: definition, types and importance in construction
Haul roads are particularly flat roads for the movement of materials, machinery and labor within construction sites, mines, or other industrial operations.
Good haul road design supports equipment performance and safety while helping prevent rutting, erosion, and environmental damage. These roads are the main routes for moving materials like ore, waste rock, or aggregates from the extraction site to processing plants, stockpiles, or transport hubs.
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 help strengthen the haul roads, spread out the loads evenly, and prevent the soil from moving around.
- Asphalt or concrete: Provide a durable, smooth surface.
Importance of haul roads in construction
How haul roads are planned, built, and maintained plays a big role in managing haulage costs. When roads are in good shape, it helps cut down on fuel use, tire damage, delays, and the cost of moving each tonne of material. 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.
A 1% cut in rolling resistance can cause significant advancements in fuel efficiency and permit a clear increase in the average speed of vehicles, which ultimately improves overall productivity.
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
Haul roads in mining and construction deal with both heavy static and dynamic loads from equipment and materials. Understanding the load-bearing capacity of haul roads is essential. Engineers evaluate it by accounting for expected loads, including the weight of machinery, volume of materials, and site-specific environmental factors.
Types of loads
It is essential to consider various types of loads, which include dead loads (the weight of the road), live loads (the weight of the equipment and materials), and environmental loads (primarily from water, temperature changes, and freeze-thaw cycles). Conducting a detailed analysis of these loads helps in establishing the correct thickness, reinforcement, and overall layout 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 relies on features like crowning the road surface, side ditches, culverts, and properly graded slopes to direct water away from the road structure.
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 made for temporary use. Once the project is done, these roads are either eliminated or given a new purpose.
- Gravel or Aggregate roads: Compact gravel or aggregate material creates a solid surface. Gravel helps water to drain, which aids in controlling erosion.
- 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 made for lasting use and often incorporate durable materials like asphalt to endure ongoing operational requirements.
- 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.
Construction process of haul roads
The construction of haul roads starts at an early phase of a project and involves careful planning. The following steps describe the process for a high-performance paved (asphalt) road, while simpler aggregate roads would typically stop after the base layer installation and compaction.
Site Analysis
This involves looking at the landscape, soil types, drainage systems, and geological features. A thorough geotechnical survey is also essential. Grasping these factors aids in deciding the optimal location, dimensions, 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 top layer, which directly handles vehicle traffic, is paved. It’s laid down evenly to create a smooth and long-lasting driving surface. This is the uppermost layer that protects 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 ensures a dependable and long-lasting solution for traversing difficult terrains, offering strong support for the heaviest haul trucks. Additionally, the beam effect improves the overall stability and lifespan of haul roads, reducing problems such as 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. The exceptional high tensile strength of geogrids aids in resisting deformation when subjected to heavy loads, thereby preserving the integrity of haul roads. It strengthens the subgrade layer, reducing the likelihood of surface damage or premature wear.
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
Constructing and using haul roads requires a significant amount of energy, which harms the land and disrupts habitats. Carelessly utilizing resources such as timber, heavy metals, and fossil fuels results in deforestation and the exhaustion of finite resources.
Water Pollution and Erosion
Haul roads have a big effect on water quality, mainly due to erosion and runoff. When it rains or the snow melts, sediments from these unprotected roads can wash into nearby streams and rivers, causing 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.