동결선에 따른 기초의 깊이는 어느 정도?(미국 펜실바이니아)

토양 동결선에 대한 가이드 [ 미국 펜실바이니아 주택연구소 간행]

-전문은 첨부파일 참조


Background

How deep does a foundation have to be?

The answer to this critical question has two parts. The first is that the foundation should be below the topsoil which is usually much weaker and more susceptible to settlement than the subsurface soil. The depth of topsoil in Pennsylvania ranges from a few inches to more than two feet. The second, and more critical point, is the depth to which the ground may freeze. In Pennsylvania, this is usually considerably deeper than the depth of the topsoil.

Most people know that if a foundation is too shallow, freezing of moisture in the soil can cause movement that could result in damage. Poor performance (windows and doors will not operate, drywall will crack, etc.) could ultimately lead to structural failure. To protect a foundation from frost action, most foundations are designed and constructed so that the bottom of the foundation lies below the extreme freeze depth for a particular area. On the other hand, if the footer is located much deeper than really necessary, the foundation will cost more and this could affect affordability.

In order to provide an economical foundation that will last the life of the structure, the freeze depth of soil needs to be established. But finding out the appropriate freeze depth for a particular location isn’t a simple matter. Freeze depth estimates often vary widely between sources (building codes and standards, design manuals, etc.) for a given location¾probably because there are so many
variables. These variables include soil types, porosity of soil, moisture content of soil, or the use of snow cover or sod in the determination of freeze depths. So what value should be used for manufactured housing and what other what other factors need to be considered?