➢ Exploratory Boring.
➢ Laboratory Test.
➢ Earth Resistivity Test.
➢ Field Test.
Soil investigation must be undertaken to determine the bearing capacity of the soil, its settlement rate and the position of the water table. One of the easiest methods is to dig trial pits and visual inspections carried out then samples with minimum disturbance are collected for subsequent laboratory testing. Where possible, drilling should be undertaken as this enables one to obtain undisturbed samples from which settlement rate and bearing capacity may be obtained. For soils that loosen, such as sand and gravel, a plate-bearing test can be used to determine the bearing capacity of the soil insitu and designing of the static loads on spread footings. If the strength of the soil is not adequate for the increased loading, it is necessary to improve on the foundations by introducing piles or enlarging the footing and reinforcing it betters to sustain the increased loading.