The process of ‘greening’ the face of a geosystem by planting or seeding the topsoil retained behind the front face. Usually employed in conjunction with a wrap around reinforced soil slope face, an inclined slope face supported by steel mesh, or a crib wall.
Vegetation of slopes and walls is an aesthetic, environmental and technical requirement for many infrastructure owners. Green surfaces are desirable to ensure the embankment / cutting / wall integrates well with the surrounding landscape and environment; often a wall or slope provides a new green space in a built up location and can contribute to biodiversity by supporting local flora and wildlife. More importantly, vegetation has an important role in controlling the erosion of slopes due to water run off, rain and wind action, and can contribute to improve the stability of the surface layers.
Trees, bushes and grasses provide a physical barrier to the actions of the elements, reinforce the soil with their root system, and absorb water reducing pore pressures in clay slopes. Vegetation works in synergy with soil and slope reinforcement and erosion control as it also provides a natural screen to the UV rays, which are detrimental to polymeric geocomponents.
Vegetation of slopes and walls is encouraged through use of grid-like surface reinforcement, which leaves space for the plants to grow. Grid reinforcement is often coupled with permanent (for steeper slopes) or bio-degradable mats that hold the topsoil in place. The mats might be supplied factory pre-seeded with appropriate nutrients incorporated, or seeding might be undertaken after placement. Biomats in particular can absorb many times their weight in water and are therefore frequently used for hydroseeding.
Geocells were used to build an environmental bund at a natural turf sport pitch in Sheffield. The local available soil, of very low shear strength, could be used, thus saving the costs of buying and importing granular material. The bund was then profiled to the required slope using topsoils, and geocells were applied on the slope surface to reduce erosion and speed up vegetation.