공유 오디오

UNIT 1: THE GROUND WE BUILD ON (FOUNDATIONS) INTRODUCTION Every building needs a good start. That start is under the ground. It is called the foundation. Before we build, we must look at the ground. The Importance of Soil Soil is the top part of the ground. It can be different. Sometimes it is hard rock. Sometimes it is soft sand. Sometimes it is wet clay. An engineer must study the soil first. Why? Because the building is heavy. The soil must hold the weight. If the soil is soft, the building c