Solutions by ground problem
Not sure which method you need? Start from the problem found in the site investigation. Each page explains how the problem is recognised, why it matters and which methods are usually considered.
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Loose sand and fill: low bearing capacity and settlement
Loose natural sands and uncontrolled fills compress under load. Structures built on them can settle more than they tolerate, and settle unevenly.
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Soft clay and compressible soil: controlling settlement
Soft clays and silts cannot be densified by impact or vibration. Under load they settle slowly and by large amounts unless the ground is reinforced or the load is carried deeper.
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Liquefaction risk in loose, saturated sands
During an earthquake, loose saturated sand can lose its strength as pore-water pressure rises. The ground then behaves like a liquid, and foundations settle or tilt.
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Collapsible soils: sudden settlement on wetting
Some dry, loosely structured soils are stable until they get wet. Water from leaks, irrigation or a rising water table then breaks the bonds between grains, and the ground collapses under load.
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Cavities and karst in limestone and gypsum
Limestone and gypsum dissolve slowly in groundwater, leaving voids. A cavity beneath a foundation may give no warning at the surface until it is loaded.
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Deep excavations next to structures and below groundwater
A deep excavation removes the support of the ground beside it. Next to buildings and roads, or below the water table, the sides must be retained and the water controlled.
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Heavy loads where the bearing stratum is deep
When the upper soils cannot carry a structure's load, even after improvement, the load is transferred to deeper, stronger strata.
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Weak subgrade under roads, yards and working platforms
Roads, storage yards and working platforms need a stiff surface layer. On weak subgrade, wheels and outriggers push through the fill, leaving ruts and unsafe platforms.
Which method fits depends on the site investigation and the performance requirement. More than one may be combined.