Hydrotex fabric forms have been used in millions of square feet of installations worldwide, some in the most severe conditions. In the process they have established a new benchmark in erosion protection by outperforming traditional concrete slope paving and riprap.
Thousands of installations and extensive flume testing of Hydrotex products have proven that our fabric-formed concrete erosion protection systems outperform all alternatives. Hydrotex linings and mats, with permissible shear stress in excess of 60 lbs/ft2 (2.87 kN/m2), provide the high degree of stability needed to resist the stresses associated with high velocity flows.
Hydrotex fabric-formed concrete has greater hydraulic efficiency than riprap and concrete slope paving because of several factors. It can mitigate uplift forces due to outflow and excess pore water pressure, reduce hydraulic uplift by slowing channel velocities, and conform to soil contours to reduce the potential for underscour.
Many styles of Hydrotex linings and mats can accommodate severe uplift pressures. These uplift pressures often cause the failure of traditional concrete slope paving. Unlike traditional methods, fabric forms can be manufactured with built-in filter drains that reduce the mean phreatic level and pore pressures within the underlying soil.
Most Hydrotex fabric forms construct concrete linings with deeply patterned surfaces. These patterns create a lining with high hydraulic resistance. The result is reduced flow velocity and reduced wave run up and down rush. These surface characteristics impart stability to the system by reducing velocities and also mean that the designer can affect the flow characteristics of a channel, creating the opportunity for an "engineered" hydraulic system.
By choosing the correct type of form, in-channel flow can be slowed, reducing downstream velocities and discharge turbulence. Or a hydraulically efficient, smooth form (such as Uniform Section) can be chosen to maximize drainage from a given area.
Filled-in-place fabric forms accommodate themselves to uneven contours, curves, and subgrades at the time that they are filled. In doing so, the soil and the concrete protection are in intimate contact, reducing the chance of underscour. Some forms create seperate concrete units, attached to each other with fabric perimeters and/or embedded cables. As a result, the concrete mats can articulate to adapt to uneven settlement.
Hydrotex fabric forms are delivered to the jobsite ready-to-fill and require no additional forming materials. Installation consists of preparing the area, laying out the forms, and filling them with concrete from a small line concrete pump. Wood or steel forming is not required, since the fabric forms themselves assure that the protective concrete assumes the proper configuration, contours, dimensions, and thickness.
Hydrotex linings and mats do not require steel reinforcement or concrete finishing. A much smaller crew can handle a Hydrotex installation and fabric forms can be installed without dewatering.
The fabric forms are extremely lightweight, so they can be rapidly shipped anywhere in the world. The "weight" component of a Hydrotex system, the fine aggregate concrete, is readily available from concrete suppliers worldwide. Once the site is prepared, simple hand tools and a concrete pump are all that is needed to fill the forms. In areas with difficult or restricted access, the concrete can be pumped to the forms from as far away as 800 feet (250 meters). Because of the low mobilization costs, it can be practical to install fabric forms on jobs as small as a hundred square feet (10 sq. meters). Regardless of the job size, the ease of mobilization and transportation, and the reduced equipment requirements mean that the job goes in faster and at less cost per square unit of protected area.
Fabric forms are designed to provide the least possible environmental impact. The fabric used in the forms filters the concrete mix, allowing excess mixing water to escape while retaining the cement solids. EL and EB linings have been designed to provide defined areas that can be cut out after installation so that native vegetation can be planted or seeded to create a more natural appearance. Hydrotex linings and mats are free of hazardous projections that could endanger pedestrians, animals, vehicles, or boats.
Filter point (FP) linings with filtering points (drains) provides erosion resistant, permeable concrete linings for ditches, channels, canals, streams, rivers, ponds, lakes, reservoirs, marinas, and protected port and harbor areas. Filter point linings have a cobbled surface and a relatively high coefficient of hydraulic friction in order to achieve lower flow velocities and to reduce wave run-up. The filter points provide for the relief of hydrostatic uplift pressures, increasing the system's stability.
Filter point linings were the first type of fabric form for concrete developed. In 1965, a Dutch patent was issued for "fabric-formed slope paving”. The form suggested by this patent was later refined to create the first "filter point" lining. As the use of this technology has spread worldwide, a variety of other forms have been developed to meet specific job requirements. However, filter point remains the most widely-used form style.
Uniform section linings are similar to traditional concrete slope paving. They create a solid, high-quality concrete lining with a relatively low hydraulic resistance and uniform cross-section. These linings are used to reduce the infiltration or exfiltration of aggressive waste and chemical fluids into or out of open channels and basins. They are also used to reduce exfiltration in arid regions where open channels and basins require watertight linings.
Uniform section linings are resistant to leachate and most chemicals. They protect geosynthetic liners from mechanical damage, exposure to UV light, and freeze-thaw cycles. These self-supporting, high-strength linings permit construction on steep side slopes and replace the conventional use of clay or sand as liner protection. Concrete filling of the forms can be performed with a minimum of traffic on the liner, and the tensile strength and abrasion resistance of the fabric protect the liner from the pumped concrete.
Articulating block mats form cable-reinforced concrete block mattresses that resist erosive forces. They are often constructed where a revetment is exposed to frontal attack by wave action. AB mats are typically used to protect coastlines, canals, rivers, lakes, reservoirs, underwater pipelines, bridge piers, and other marine structures from propeller wash, ship wakes, wind waves, currents, and high velocity flows. They are also used in environmental construction for landfill caps, down chutes, and collector channels.
The AB fabric form consists of a series of compartments linked by an interwoven perimeter. Grout ducts interconnect the compartments, and high strength revetment cables are installed between and through the compartments and grout ducts. Once filled, the AB mat becomes a mattress of pillow-shaped, rectangular concrete blocks. The interwoven perimeters between the blocks serve as hinges to permit articulation. The cables remain embedded in the concrete blocks to link the blocks together and facilitate articulation.
Filter Band linings are similar to filter point, providing an effective and highly permeable concrete lining that resists erosive forces. Filter Band differs from filter point in that the form creates interconnected, tubular concrete elements that are separated by large, interwoven filter bands. The filter bands provide for greater reduction of uplift pressures than filter point linings. Also, the biaxial alignment of the tubular elements creates two directionally determined coefficients of hydraulic friction. As a result, Filter Band achieves greater reduction of flow velocity or wave energy than filter point.
Filter Band concrete linings are specified in situations similar to those for which filter point might be used, but which also require greater relief of uplift pressures, higher reduction of flow velocities, or greater reduction of wave run up.
Enviromat linings are installed to provide protection against periodic high flows. After installation, vegetation can be planted within the open structure of the lining.
Enviromat linings are used in drainage ditches and on the upper slopes of channels, canals, lakes, reservoirs, rivers, and other water courses, as well as for embankments subject to heavy run-off. Enviromat linings are comprised of concrete-filled elements and unfilled areas that allow for the establishment of vegetation. Once the concrete sets, the unfilled and interwoven areas are opened by cutting the fabric and are planted or filled with topsoil and seeded. Within a growing season a vegetated cover will normally extend over the lining, resulting in an erosion control system with the hydraulic, ecological and aesthetic features desired.
EL linings have a greater open area than EB, so a vegetated cover will be established more rapidly. EB linings can articulate and are more tolerant of uneven settlement after installation.