Structural backfill design for corrugated-metal buried structures

The aim of this study is to provide a design method for the structural backfill envelope surrounding corrugated-metal buried conduits that will consider the behavior of the surrounding soil as well as the structure\u27s properties. The requirements of the structural backfill envelope are discussed. Previous design practice is reviewed and its deficiencies are pointed out. The need for an appropriate design method for the structural backfill envelope is shown. Soil models for finite element analysis of soil-conduit systems are presented. Soil parameters for these models are evaluated to investigate their suitability. As a result of this evaluation, recommended values of soil parameters for design are suggested. It is shown that the performance of two field installations is satisfactorily predicted using these recommended values. A study of the constructability of soils showed that granular soils are much easier to place and compact to minimize structural distortion and provide much higher support to the conduit than cohesive soils. A design criterion for the width of the structural backfill envelope based on limiting values of deflection is presented. A design approach for conduit wall thrust is also developed. This approach considers the effects of conduit shape, width of structural backfill envelope, fill height, conduit size, and compression and bending stiffnesses. Arching factors from different methods are compared. After reviewing the past work on buckling, the elastic continuum theory is used to develop buckling design charts. The effects of the width of structural backfill envelope, relative stiffness between the conduit and the structural backfill soil, the relative stiffness between the surrounding soil and the structural backfill soil, and the height of fill are included in these charts