Civil engineer guide to fighting positions, shelters, obstacles

AFH 10-222 Volume 14 1 August 2008 49
2.5.7.1. Site Selection and Preparation. Site selection and preparation are
critical to the performance of structures built using wire mesh containers. Soil
conditions and drainage patterns must be considered when siting these structures.
Factors that influence deterioration of near-surface materials are elevated
moisture levels, soil erosion, freeze/thaw cycles, decay of organic matter,
and compression of weak soils. Wire mesh container structures transmit
their loads through the “fill walls” into the foundation below. The foundation
needs to be stable enough to absorb these loads. The site should be flat and
level with sufficient strength and stability to support the structure for the
amount of time it is needed. If a structure cannot be sited on an improved
surface such as concrete, asphalt, or stabilized soil, the area should be graded
to remove excess materials and loose surface soils to provide a smooth and
level surface to prevent the structure from settling and shifting over time. To
improve the surface area, dig a trench, approximately 20 inches beneath each
wall of the structure (Figure 2.24). The width of the trench should extend 20
inches beyond the edge of each wall. Line the trench with a geotextile cloth
(minimum weight 200 g/m2) and backfill it with a well compacted layer of
coarse graded fill material or crushed rock. Test the foundation for strength
and stability before starting any type of construction.
Figure 2.24. Improved Foundation.