Resilient Performance of Controlled Density Fill in Utility Trench Excavations
WASHINGTON UNIV SEATTLE DEPT OF CIVIL ENGINEERING
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Controlled Density Fill CDF is a ready-made mix of sand, fly ash, cement, and water that, when used as backfill, flows into excavated cavities, completely filling all voids. It can be used anywhere conventional soils or aggregate backfill is used. Its advertised advantages are numerous including speed, cost, and performance. This study concentrates on CDFs performance in utility trenches as a flexible pavement subgrade backfill material where careful engineering consideration must be given in determining material properties for pavement design and analysis. Since resilient modulus testing is the most accurate method of determining pavement subgrade suitability for soils, these tests were conducted of CDF cylinders. Moduli were compared with those of typical subgrade soils. Subgrades with resilient modulus values greater than 15, 000 psi are considered excellent material. While subgrades under Washington highways averaged 19,300 psi, CDF with 40 lbsCY of cement averaged 41,400 psi. CDF with 30 lbsCY of cement averaged only 11,700 psi. No plastic deformation settlement problems were encountered after 612,000 equivalent single-axle loads with the 40 lbsCY mix. When combined with other advantages including economy, CDF appears to be a viable subgrade material.
- Soil Mechanics
- Civil Engineering