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: Measurement of particle-size distribution (PSD) of soil with large-sized particles (e.g., 25.4 mm diameter) requires a large sample and numerous particle-size analyses (PSAs). A new method is needed that would reduce time, effort, and cost for PSAs of the soil and aggregate material with large-sized particles. We evaluated a nested method for sampling and PSA by comparing it with the methods that follow the American Association of State Highway and Transportation Officials (AASHTO) standard T88-00 and the American Society for Testing and Materials (ASTM) standard D422-63. Using 33 forest road aggregate samples from the Clearwater National Forest in northern Idaho, the nested method required much less laboratory time and effort and resulted in similar PSA values, except for the 0.149 mm (No. 100) sieve, where the smallest particle-size fraction (PSF) values (1.30% and 1.39%) were observed. The nested method shows great potential for determining PSDs of the soil and aggregate material with large-sized particles and should be tested on other forest soils and road aggregates. The nested sampling and analysis method allows for the same number of samples to be collected but requires less laboratory time, making it more efficient and economical for testing the soil and aggregate material with large-sized particles such as forest road aggregate. Key words: grain-size distribution, gravel road, soil grading, soil sampling, unpaved road. Resume: Il faut un vaste echantillonnage et plusieurs analyses granulometriques pour mesurer la distribution granulometrique d'un sol qui contient de grosses particules (p. ex., diametre de 25,4 mm). Une nouvelle methode est necessaire pour reduire le temps, les efforts et les ressources financieres necessaires pour faire l'analyse granulometrique des sols et materiaux granulaires qui contiennent de grosses particules. Nous avons evalue une methode imbriquee pour l'echantillonnage et l'analyse granulo-metrique en la comparant aux methodes prescrites par la norme T88-00 de l'American Association of State Highway and Transportation Officials (AASHTO) et la norme D422-63 de l'American Society for Testing and Materials (ASTM). Avec 33 echan-tillons de granulat provenant de chemins forestiers dans la foret nationale de Clearwater dans le nord de l'Idaho, la methode imbriquee a necessite beaucoup moins d'efforts et de temps de laboratoire et les valeurs de l'analyse granulometrique etaient similaires a l'exception de la passoire de 0,149 mm (N° 100) ou les plus faibles valeurs (1,30 et 1,39 %) de classe granulometrique ont ete observees. La methode imbriquee offre un fort potentiel pour determiner la distribution granulometrique des sols et materiaux granulaires qui contiennent de grosses particules et elle devrait etre testee pour d'autres sols forestiers et granulats utilises pour les chemins forestiers. La methode imbriquee d'echantillonnage et d'analyse permet de collecter la meme quantite d'echantillons mais exige moins de temps de laboratoire, ce qui en fait une methode plus efficace et plus economique pour tester les sols et les materiaux granulaires qui contiennent de grosses particules tels que le granulat utilise pour les chemins forestiers. [Traduit par la Redaction] Mots-cles: distribution granulometrique, route de gravier, granulometrie des sols echantillonnage des sols, route non revetue., Introduction Particle-size analysis (PSA) is a method commonly used to deter-mine the particle-size distribution (PSD) of soil and aggregate material. The PSD consists of particle-size fractions (PSFs) of each individual [...]

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. [ABSTRACT FROM AUTHOR]

Accurate spatial information on forest roads is important for forest management and harvest operations. This study evaluated the positional accuracy, shape similarity, and cost of three mapping techniques: GNSS (Global Navigation Satellite System) mapping, CAD file conversion (as-built drawing), and image warping. We chose five road routes within the national forest road system in the Republic of Korea and made digital road maps using each technique. We then compared map accuracy to reference maps made from field surveys. The mapping and field-survey results were compared using point-correspondence, buffering analysis, shape index, and turning function methods. The comparisons indicate that GNSS mapping is the best technique because it generated the highest accuracy (Root Mean Square Error: GNSS mapping 1.28, image warping 7.13, CAD file conversion 13.35), the narrowest buffering width for 95% of the routes overlapped (buffering width: GNSS mapping 1.5 m, image warping 18 m, CAD file conversion 24 m), highest shape similarity (shape index: GNSS mapping 19.6–28.9, image warping 7.2–10.8, CAD file conversion 6.5–7.4), and smallest area size difference in turning function analysis (GNSS mapping 2814–4949, image warping 7972–26,256, CAD file conversion 8661–27,845). However, GNSS requires more time (236 min/km) and costs more ($139.64/km) to produce a digital road map as compared to CAD file conversion (99 min/km and $40.90/km) and image warping (180 min/km and $81.84/km). Managers must decide on the trade-off between accuracy and cost while considering the demand and purpose of maps. GNSS mapping can be used for small-scale mapping or short-haul routes that require a small error range. Image warping was the lowest cost and produced low-accuracy maps, but may be suitable for large-scale mapping at the regional or national level. CAD file conversion was expected to be the most accurate method, because it converted as-built drawings to a map. However, we found that it was the least accurate method, indicating low accuracy of the as-built drawings. Efforts should be made to improve the accuracy of the as-built drawings in Korea. [ABSTRACT FROM AUTHOR]