Evaluation of Flowable Fly‐Ash Backfill. II: Dynamic Loading

Abstract

This is the second paper in a two‐part series describing trench backfill tests designed to evaluate the performance of a flowable fly‐ash backfill (ashcrete) versus that of compacted soil backfills. The site for the tests is Duke Power's Marshall Steam Station. For these tests, a series of parallel trenches is installed in the outbound lane of an on‐site service road. The major use of this road is for the hauling of fly ash to an on‐site storage area. Instrumented pipes are installed in the trenches, which are subsequently backfilled using both compacted soil and ashcrete. Surface strains for the buried pipes and joint loads are monitored for static and dynamic loading conditions. The monitored dynamic strains and joint loads resulted from normal heavy‐vehicle traffic at the site. Comparative surface strain and joint‐load data are presented at two stages of compaction for the soil backfill and the ashcrete backfill. Additional strain data for the ashcrete backfill are included to demonstrate the continued performance of this backfill after additional curing. The project was designed to demonstrate the feasibility, advantages, and safety of using this flowable fly‐ash backfill in a typical continuous high‐load application.