Earth Pressures Due to Compaction: Comparison of Theory with Laboratory and Field Behavior

Compaction of backfill adjacent to stiff and unyielding structures induces earth pressures in the compacted fill that exceed normal at-rest earth pressures. A numerical method that can be used to calculate compaction-induced lateral earth pressures has been proposed by Duncan and Seed. The purpose of the study described in this paper is to evaluate the theory by comparing calculated and measured compaction-induced lateral earth pressures. The data for the comparisons is from values measured in backfills behind three stiff, unyielding walls: the instrumented retaining wall in the Transport and Road Research Laboratory in Crawthorne, England; the instrumented retaining wall in the Virginia Tech Geotechnical Laboratory in Blacksburg, Virginia; and the lock walls at Eisenhower and Snell Locks in New York state. The lock walls were found to be cracked, apparently by high earth pressures induced by compaction, and an extensive rehabilitation program was required. The measurements from all three walls confirm the existence of compaction-induced lateral earth pressures. For clean sand backfill, pressures calculated using the theory of Duncan and Seed are shown to be in reasonable agreement with measured values. Laboratory test data indicate that for moisture-sensitive silty sand backfill the applicability of the Duncan and Seed theory, which does not include considerations of pore water pressure development during backfill placement and compaction, depends on the degree of saturation of the backfill.