Large construction projects often have erosion control problems, and there are many potential causes. However, each case is different and must be handled based on site conditions and severity. Erosion control is important not only for preserving the construction site and protecting new structures, but also for mitigating the environmental impact on the surrounding area.
Manufacturers are constantly developing innovative products to reduce erosion and other environmental impacts. This article provides an overview of the most common methods.
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Riprap is one of the most popular methods used to protect the soil from erosion in areas of concentrated runoff. Riprap is a layer of large interlocked stones, forming a barrier on slopes that are unstable due to seepage, or in places that constantly receive a large and concentrated flow. This erosion control method is commonly used to reduce erosion in lake shores and riverbeds. In most cases, before riprap is installed, a layer of synthetic geotextile membrane is placed to prevent the soil from moving through the riprap.
Articulated Concrete Block
Articulated concrete blocks (ACBs) provide a hard armored surface that is considered an alternative to riprap. ACBs consist of a matrix of individual concrete blocks that are placed together, forming an erosion-resistant overlay with specific hydraulic characteristics.
Articulated concrete blocks are revetment systems, produced in various shapes and thicknesses. ACBs form a flexible and interlocking matrix of blocks with uniform size, shape and weight. They are connected by a series of cables and used to handle erosion on the embankments of waterways, boat ramps and drainage channels. ACBs can be molded for an existing area to protect from erosion, while allowing vegetation growth through the layer.
Mechanically stabilized earth (MSE) walls are a new technology that has replaced many conventional concrete retaining walls in recent decades. A MSE wall is a composite structure with alternating layers of compacted backfill and soil reinforcement elements. These are fixed to a thin wall facing, which prevents erosion of the structural backfill. This type of wall provides several advantages over traditional reinforced walls, such as ease and speed of installation. MSE walls provide flexibility, offering a high load-bearing capacity and seismic resistance. Thanks to their features, these walls can be built very tall.
Turbidity barriers are implemented to prevent soil erosion, and also to keep contaminants away from water sources. These barriers are typically made from a floating geotextile membrane, which is anchored to the bottom of a water body with weights. They consist of a top flotation boom, an impervious fabric curtain that extends downwards, and a heavy galvanized chain sealed into a hem along the curtain length. There are cases in which turbidity barriers are used for supplemental sediment control. They are also known as floating turbidity silt curtains.
A french drain consists of an underground piping system called a drain tile, which channels surface and groundwater to an exit point. The drain tile is sometimes perforated to allow water seepage into the soil beneath, while the excess water travels to the exit point. For proper installation, french drains require a slope of around 1 inch of drop per 10 feet of horizontal run.
Geotextiles are used to control erosion and improve soils, before installing embankments, pipelines, roads or earth-retaining structures. Geotextiles may have an open mesh weave, a warp-knitted structure, or a close fabric or nonwoven surface. When selecting a geotextile, some of the factors considered are separation, filtration, drainage, sealing, reinforcement and protection.
Soil nails improve resistance against slope failures, and they can be installed relatively quickly. The procedure consists of drilling into the soil and placing a series of steel bars deep into the earth. The nails are capped at the surfaces with facing, creating a barrier that resembles a retaining wall. As an alternative, soil nails can be driven into the soil and grouted in place after installation.
Dust Control Methods
Dust control methods should be implemented in any construction site where there is potential water and air pollution from dust travelling through the landscape. Uncontrolled dust pollution can also worsen the effect of wind erosion. There are several methods used to control dust in construction sites, which include misted water, silt fences, and polymer additives.