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Article

An Approach for Modeling and Quantifying Traffic-Induced Processes and Changes in Forest Road Aggregate Particle-Size Distributions

1
Department of Environment and Forest Resources, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon 34134, Korea
2
School of Environmental and Forest Sciences, University of Washington, Seattle, WA 98195-2100, USA
3
Department of Forest Engineering, Resources and Management, Oregon State University, Corvallis, OR 97331-5704, USA
4
US Department of Agriculture Forest Service, Rocky Mountain Research Station, 1221 South Main Street, Moscow, ID 83843-4211, USA
*
Author to whom correspondence should be addressed.
Forests 2019, 10(9), 769; https://doi.org/10.3390/f10090769
Received: 29 July 2019 / Revised: 30 August 2019 / Accepted: 2 September 2019 / Published: 4 September 2019
(This article belongs to the Special Issue Planning, Design, and Maintenance of Forest Road Networks)
Forest road aggregate changes due to traffic. The physical processes that cause these aggregate changes need to be understood for more effective road management that can help reduce maintenance costs and efforts, and negative environmental impacts of forest roads. This study modeled three processes that could change the particle size distribution (PSD) of forest road aggregate: crushing (breaking down the surfacing material), subgrade mixing (moving upward of fine-grained, roadbed sediment), and sweeping (migration of loose aggregate particles to the shoulder and roadside by tire action). There are two types of sweeping: sweeping-out (dislodging large-size particles from tire tracks) and sweeping-in (accumulating large-size particles near the roadside and shoulder). Our study modeled the expected traffic-induced processes based on theoretical concepts and literature to examine how these processes change forest road aggregate PSD. Then the modeled results were compared with the observed PSDs from cross-sectional locations where traffic-induced processes likely occurred. Based on these comparisons, we enhanced the modeling and inferred how much the crushing, subgrade mixing, and sweeping-in processes changed the PSDs, but could not infer the sweeping-out process due to the difficulty in separating the sweeping-out from crushing. This study demonstrates that the traffic-induced processes could be modeled and quantified using the following assumptions: crushing was estimated by assuming a half logarithmic normal distribution with a mean of the crushed particle diameter and higher crushing rates for large-size particles; subgrade mixing was estimated by assuming the move-in of fine-grained subgrade soils from the road bed; and sweeping-in was estimated by assuming the move-in of large-size particles with a logarithmic normal distribution. Our modeling approach can offer insights on how traffic-induced processes affect road aggregate under various road and traffic conditions. This information can be useful in developing cost-effective road maintenance strategies and implementation plans. View Full-Text
Keywords: crushing; logarithmic normal distribution; particle size distribution; process modeling; road aggregate; subgrade mixing; sweeping; traffic crushing; logarithmic normal distribution; particle size distribution; process modeling; road aggregate; subgrade mixing; sweeping; traffic
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MDPI and ACS Style

Rhee, H.; Fridley, J.; Chung, W.; Page-Dumroese, D. An Approach for Modeling and Quantifying Traffic-Induced Processes and Changes in Forest Road Aggregate Particle-Size Distributions. Forests 2019, 10, 769. https://doi.org/10.3390/f10090769

AMA Style

Rhee H, Fridley J, Chung W, Page-Dumroese D. An Approach for Modeling and Quantifying Traffic-Induced Processes and Changes in Forest Road Aggregate Particle-Size Distributions. Forests. 2019; 10(9):769. https://doi.org/10.3390/f10090769

Chicago/Turabian Style

Rhee, Hakjun, James Fridley, Woodam Chung, and Deborah Page-Dumroese. 2019. "An Approach for Modeling and Quantifying Traffic-Induced Processes and Changes in Forest Road Aggregate Particle-Size Distributions" Forests 10, no. 9: 769. https://doi.org/10.3390/f10090769

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