TABLE OF CONTENTS Design methods which are used to determine an installation design for buried gravity flow pipes are described in this chapter. Soil types and their uses in pipe embedment and backfill are discussed. Design methods are placed in two general classes rigid pipe design and pressure pipe design. Pipe performance limits are given, and recommended safety factors are reviewed.
The finite element method for design of buried piping systems is relatively new. The use of this powerful tool is increasing with time. A detailed discussion of this method is included.
The importance of soil density (compaction) and soil type in contributing to buried pipe performance has long been recognized by engineers. The pipe-zone backfill, which is often referred to as the soil envelope around the pipe, is most important. An introduction and a brief discussion of embedment soils are presented in Chap. 1. In this chapter, additional information on soil classification and soil-pipe interaction is provided.
Professor Arthur Casagrande proposed a soil classification system for roads and airfields in the early 1940s. This system, now called the Unified Soil Classification System (USCS), has been adopted by many groups and agencies, including the Army Corps of Engineers and the Bureau of Reclamation. The American Society for Testing and Materials (ASTM) version of the USCS is entitled "Classification of Soils for Engineering Purposes" and carries the designation D 2487.
The USCS is based on the textural characteristics for those soils with a small amount of fines such that the...
