Compaction and Breakage Characteristics of Crushed Stone Used as the Backfill Material of Urban Pavement Subsidence

The subsidence of urban pavement is becoming frequent accidents, and backfill is the primary means of remedy. Crushed stone is a commonly used aggregate for backfill material in engineering, and its compaction behavior under load needs to be well understood. In this work, a series of compaction tests were carried out on the same batch of crushed stone samples with the same gradation. The content changes of particles with different sizes were analyzed, the particle breakage characteristics during the compaction process were discussed, and the difference in particle breakage caused by loading speed and loading mode was examined. It shows the following: (1) For all samples, the content of particles that were crushed during compaction was always less than 40%. The particles with the strongest breakage varied with sample gradation. (2) The particle breakage could be divided into four categories: complete fragmentation, complete rupture, local fragmentation, and surface grinding. They affected the particle size distribution after compaction to varying degrees. (3) The particle breakage could be expressed as a cubical parabola of loading speed, whose coefficients are related to the sample gradation. (4) Stepwise loading rendered stronger particle breakage than direct loading, and the increase of particle breakage due to loading mode was more evident for continuous grading samples than discontinuous grading samples. This study will provide an experimental basis and reference for the selection and use of backfill aggregate in urban subsidence areas.

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