Matthew 7 : 24-27; “Therefore everyone who hears these words of mine and puts them into practice is like a wise man who built his house on the rock. The rain came down, the streams rose, and the winds blew and beat against that house; yet it did not fall, because it had its foundation on the rock. But everyone who hears these words of mine and does not put into practice is like a foolish man who built his house on sand. The rain came down, the streams rose, and the winds blew and beat against that house, and it fell with a great crash,” end of quote.
Building on ‘sand’ in reference to Jesus’ allegory, is putting up a building on a weak foundation-ground. The soil or rock is referred to as the natural foundation, and the bases of the walls or columns form the artificial foundations. Foundations receive and spread the load from structure above it over a safe area of the subsoil, providing a stable level on which to build. This protects the structure from damage due to soil movement caused by shrinking or swelling. Site investigation determine an ideal building foundation.
Site investigation is normally carried out to ascertain the type of in relation to the building being put up. And the extent of site investigation depends on the complexity of soil conditions, existing information about occurrences which may interfere with the stability of the building, foundation arrangements for the structure and the funds available for construction. In most cases, site investigation is carried out during preliminary stages of construction.
This is done by taking soil samples at various positions on the site. The samples are taken from trial pits of up to 3 m deep for small work. Boring the site for medium or large works [e.g., dams, power stations or monumental buildings] can also be done from a pit of up to 30 m deep. Pits are dug using a hand auger outside the perimeter of the proposed building; they can also be dug mechanically. The depth varies from 1.5 to 3 m and 1.2 m square and they should not be more than 3 m apart and not less than one per 930 square m of the site.
An inspection of the sides of the excavated pits will give the engineer information regarding the soil strata in respect to its bearing capacity. Such inspection should be done as soon as the excavation work is completed. Deeper trial pits may be used for investigation of rock which cannot be recovered intact in normal boring operations. So, wise builders don’t overlook site investigation.