• Journal of Korean Society of Forest Science
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• v.88 no.2
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• pp.255-265
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• 1999

This study deals with forest soil characteristics and their effects on the trafficability of logging vehicles. The study area is the national experimental forest located in Kwangnung. This site has 20m length and is equally divided by 5 surveying ranges with 4m width, on which a tractor(FIATAGRI) attached with logging boogie can drive in 4 driving types, namely 1time-return unload, 1time-return with load of 780-790kg weight of 3 logs, 5 and 10times-return with same load. After one driving type on all surveying ranges, the soil hardness is surveyed 5 times with 3 several type tools, SHM-1 type, lang penetrometer(L-PNTM), and clegg impact soil tester(CIST). A disturbed degree of cover vegetation and sliding conditions of vehicle are also observed. As results, the soil type of the test site was SC by USCS and dry brown forest soil. The cover vegetation is gotten trambled under driving after 3-5 times-return, shrubs leaves are fully fallen and their bark are peeled, and after 10 times-return the cover vegetations were nearly disappeared. The test vehicle has neither slided nor was overthrown. The wheel tracks in the 1-3 ranges, of which unit weight(gd, gt) is high and soil moisture content(MC) is low, were only 1-2cm deep, but those in the 4-5 ranges, of which the gd, gt is low and the MC is high, were 5-7cm deep. In the soil hardness test, which was established in 5 test ranges by types of driving, the more driving times, the higher the hardness. The soil hardness surveyed by L-PNTM has changed slowly and that surveyed by SHM-1 type has risen sharply. In the ranges with higher specific gravity(Gs), higher unit weight, lower MC and higher liquid limit(LL) and plasticity index(PI) was the soil hardness high and the trafficability was good. In the ranges with opposite conditions, also in the ranges of the lower soil hardness, the trafficability must be not good, because the wheel track may be deep. The results from CIST attached with 4kg hammer was not better than expected. So it is recommended to use CIST with 2.5kg or 0.5kg hammer.

• International Journal of Highway Engineering
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• v.4 no.4 s.14
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• pp.23-39
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• 2002

This study dealt with developing a new approach for finding properties which might represent rut resistance characteristics of asphalt mixture under static loading. Two aggregates, a normal asphalt (pen 60-80) and 5 polymer-modified asphalts were used in preparation of 12 dense-graded mixtures. Marshall mix design was used in determination of OAC and each mixture at the OAC was prepared for a newly-developed Kim test on Marshall specimen (S=10cm) and gyratory specimen (S=15cm), and for wheel tracking test. Kim test used Marshall loading frame and specimens were conditioned for 30min at $60^{\circ}C$ before loading through Kim tester an apparatus consisting of a loading column and a specimen and column holder Diameter (D) of column was 3cm and 4cm with each column having different radius (r) of round cut at the bottom. The static load was applied at 50mm/min in axial direction of the specimen, not in diametral direction. The maximum load ($P_{max}$) and vertical deformation (y) at $P_{max}$ point were obtained from the test. A strength value was calculated based on the $P_{max}$ r, D and y by using the equation $K_D = 4P_{max}/{\pi}(D-2(r-\sqrt{2ry-y^2}))^2$ and is defined as the deformation strength ($kgf/cm^2$). The values of $P_{max}$/y and $K_I=K_D/y$ were also calculated. In general the leading column diameter and radius of round cut were significant factors affecting $K_D$ and $P_{max}$ values while specimen diameter was not. The statistical analyses showed the $K_D$ had the best correlation with rut depth and dynamic stability. The next best correlation was found from $P_{max}$ which was followed by $P_{max}$/y and $K_I$ in order.