Foundation Engineering:
Shallow foundations (sometimes called 'spread footings') include pads, strip footings and rafts. Shallow foundations are those founded near to the finished ground surface. If surface loading or other surface conditions will affect the bearing capacity of a foundation it is 'shallow'. Shallow foundations are used when surface soils are sufficiently strong, dense or stiff to support the imposed loads; they are generally unsuitable in weak or highly compressible soils, such as poorly-compacted fill, peat, soft clay, loose sand, etc.
Deep foundations
include piles (cast-in-place-drilled piles, driven piles, micro piles and H-piles), pile walls, diaphragm walls and caissons. Deep foundations are those founded deeply below the finished ground surface for their base bearing capacity to be affected by surface conditions. Deep foundations can be used to transfer the loading to a deeper, more competent strata at depth if unsuitable soils are present near the surface.
Mat foundations are shallow spread foundations consisting of a single slab covering the supporting stratum beneath the entire supported superstructure.
Earth retaining system (retaining walls or shoring) are designed for either permanent subterranean or retaining walls system. Retaining walls system should be designed to resist lateral earth pressures from the soils with or without consideration of hydrostatic pressure behind the walls.
Shoring will be required to support of construction excavations if sloping excavation is not feasible. A soldier-pile shoring system may be used to maintain temporary support of vertical wall excavations.
Soldier Piles are constructed of steel H sections driven prior to excavation. As the excavation proceeds, horizontal sheeting (lagging) is inserted behind the piles. The horizontal earth pressures are concentrated on the soldier piles because of their relative rigidity compared to the lagging. Soil movement and subsidence is minimized by maintaining the lagging in firm contact with the soil. Soldier piles are most suitable in conditions where well constructed walls will not result in subsidence. Ideally over consolidated clays, soils above the water table if they have some cohesion and free draining soils which can be effectively de-watered, e.g. sands.
Tie Backs are earth anchors installed either horizontally or diagonally to exert vertical force on a wall.
