Sunday, March 18, 2012

Landscaping Strategies for Soil Control

Landscaping on a large scale, as for a new home or perhaps even a larger building, comes with a set of common engineering problems that have been worked on for centuries in a series of ever-improving techniques. Among these is keeping earth under control, particularly in sloping land. Earth is not as firm (at least in construction terms) as is generally necessary, so ways of stabilizing it have been extensively studied. Here are some of the solutions in use today. These represent new ideas or refinements.

When an earthen slope needs to be held in place (because it will tend to settle and move downward over time, especially when acted upon by weather), Retaining Walls are often the solution called upon. A retaining wall not only holds earth in a predefined space, it also allows for terracing in a landscaping scheme. Retaining walls can be shaped and curved to conform to the terrain or the vision of the architect, and can be faced in a wide variety of appearances, from smooth to rough-hewn.

There are a number of different kinds of retaining walls. One simple example is the typical basement foundation walls of a house; they hold back soil from the basement. It should be noted, however, that the term "retaining wall" usually refers to a wall that is not anchored top and bottom. Typical retaining walls used in landscaping include gravity retaining walls, which rely mainly on the strength of the wall material to hold back the soil. They are normally made of stone or concrete and may feature a backward angle for additional support.

Another common retaining wall is the cantilevered wall, which is a stone wall with a large footing to help relieve pressure; cantilevered walls are often buttressed from the front as well. Another type is the piling wall, which is usually made of metal or wood; piling walls gain strength by having two-thirds of their length underground to support the above ground portion. Piling walls offer a good strategy in areas where the soil is softer than normal.

One other method for controlling soil is the use of a Geotextile. This is a plastic fabric, which may be a weave or a solid sheet that is placed underground to hold soil in place. It has the advantage of offering permeability, should drainage be required. Geotextiles are a common strategy employed to retard soil erosion.

A more modern technique that came into common use in the 1970s and quickly spread is called soil nailing. As the name implies, reinforced steel bars, either solid or hollow, are "nailed" into a slope. They are usually capped in some fashion. This stabilized the slope to a surprising degree. A geotextile mesh may also be used.

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