Abstract
Crushed stone is the most common material for use in the aggregate of bedding course. The aggregate for the bedding course of permeable roads needs to not only meet the requirements of basic mechanical properties but also ensure permeability and structural stability. This work analyzed permeability under extreme rainfall conditions and the particle mass loss during permeation and then investigated the stability of crushed stone aggregate and examined the optimal gradation and compaction levels of the crushed stone aggregate in engineering applications. It shows that (1) the permeation process included two phases, and the change of permeation velocity mainly occurred in the first phase. The permeation velocity of samples with different gradations at different compaction levels showed a stepwise change in its order of magnitude. (2) The change in permeability coincided with the change in flowrate, most probably because the sudden change of the flow altered the permeability of the sample. Factors such as gradation, compaction, and the randomness of particles arrangement in the crushed stone during sample charging all affected the permeability of the sample. (3) During the permeation process, the mass loss decreased with rising gradation. The gradation and compaction had strong influence on particle mass loss. Therefore, ensuring the structural stability of permeable road necessitates careful selection of the gradation and compaction for the crushed stone aggregate. It is recommended to use the crushed stone sample with a gradation of n = 0.7 and a compaction level of no greater than 20 mm for the aggregate of the bedding course.
Highlights
Most roads in Chinese cities use impervious pavement. e drawbacks of impervious pavement include the following. (1) It disrupts the natural circulation of water and prevents precipitation from replenishing groundwater because it lacks the permeability of soil and vegetation. (2) It obstructs the heat and water exchange between the air and the ground and worsens the “heat island” effect in urban areas because it releases massive amount of absorbed solar heat. (3) It tends to cause accumulation of water and eventually leads to urban flooding [1,2,3]
(3) During the permeation process, the mass loss decreased with rising gradation. e gradation and compaction had strong influence on particle mass loss. erefore, ensuring the structural stability of permeable road necessitates careful selection of the gradation and compaction for the crushed stone aggregate
Since the 1980s, impervious pavement is increasingly replaced around the globe by permeable asphalt, permeable tile, cobble stone-like pavement, etc., to improve the permeability so that rainwater can rapidly infiltrate into soil to reduce soil erosion, conserve water sources, and improve regional ecological environments [3,4,5]
Summary
Received 21 August 2020; Revised 10 October 2020; Accepted 19 October 2020; Published 31 October 2020. Is work analyzed permeability under extreme rainfall conditions and the particle mass loss during permeation and investigated the stability of crushed stone aggregate and examined the optimal gradation and compaction levels of the crushed stone aggregate in engineering applications. It shows that (1) the permeation process included two phases, and the change of permeation velocity mainly occurred in the first phase. It is recommended to use the crushed stone sample with a gradation of n 0.7 and a compaction level of no greater than 20 mm for the aggregate of the bedding course
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