6.A1 INTRODUCTION

Increasing urbanization continues to occur throughout much of the world, and at this time this trend appears likely to continue for at least the near future. As the population grows in any metropolitan area, a variety of additional facilities are needed to serve these people. Many of these facilities are in the form of structures such as houses, apartment buildings, restaurants, and office buildings that occupy areas within the metropolis. The additional space required for these structures is generally obtained in three ways: ( a) Existing structures are torn down to make room for new structures; ( b) new structures are built on land within the existing metropolitan boundaries that were previously unimproved (relative term); and ( c) the boundaries of the metropolis are expanded to provide additional land for development.

One of the primary criteria used to select a site for development is the suitability of the ground for supporting the structure to be built. In most urban areas, the best sites were developed first, and, as urbanization continues, when a previously undeveloped site is purchased, the engineering properties of the existing near-surface materials are often such that the structure cannot be supported by shallow foundations. The traditional solution for these situations is to support the structures on deep foundations typically piles or drilled piers where a small portion of the load is transmitted to the poorer near-surface materials and a large portion of the load is transmitted to better bearing materials deeper within...