Abstract
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.
Highlights
During the rapid urban expansion in China, pavement subsidence in urban areas is occurring frequently [1, 2]
Samples with variable gradation were subjected to a series of compaction tests to analyze the changes in the particle content of crushed stone of different sizes. e characteristics of particle breakage during the compaction process were discussed, and the difference in particle breakage caused by loading speed and loading mode was examined
The breakage characteristics of the particles determine how the mass of particles of different size varies after the compaction [14, 15]. e breakage characteristics are dependent on factors such as the particle arrangement after charging, gradation, loading speed, and loading mode
Summary
During the rapid urban expansion in China, pavement subsidence in urban areas is occurring frequently [1, 2]. E materials for backfill often consist of crushed stone particles of different sizes, of which the particle size and gradation are the most important factors that affect the compaction and deformation of backfill materials. Xu et al [8] examined the compaction of soil-rock mixtures by considering variables as the content of >5 mm particles, the maximum filler particle size, and the filler gradation and recommended that the content of coarse material should reach 60%–80%, the maximum particle size should be 30% of the loose paving thickness, and the gradation should be continuous even though no obvious correlation was found between the gradation of the filler and the compaction characteristics of the backfill. It was found that gradation had no significant impact on the compaction strain of crushed sandstone, and particle breakage was widespread during compaction.
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