The purpose of this paper is to test models by computing hill slope form in an area of 5ha. including about 80 measuring points data with the size of a grid of 25m×25m. Therefore computed profiles can be compared with actual profiles in slope-gradient distribution whose terrain indices F were known. The analytical solution of the slope-gradient distribution, with the values ranged from logS_1 to logS_2, could be approximately fitted to the linear equation. Each F_1 and F_2 of given point S_1 and S_2, in which F_1 and F_2 are area percentages of slopes less then each S_1% and S_2% than (S_1<S_2), are also obtained from the linear equation. Least-squares method is used to obtain a "best" value for terrain index F that maximizes the level of agreement between actual slope-gradient distribution and computed profile. The determined equation F was well expressed by logistic equation that was controlled by the value of slope standard deviation σ_m. This method produces a value of terrain index F that is sufficiently accurate in the present context. Agreement between theoretical profiles and measured ones for the 120 area data, is generally good, with the exception of profiles deformed by slumping. Therefore, the preliminary results suggest that the model can be used to simulate slope-gradient distribution according to the linear equation.

View full abstract

Just after work, the foot print of the semi-legged vehicle was about 50cm in width, about 60cm in length, about 30cm in depth and at interval of about 3m on the flat ground. The values of cone index on the foot print were similar to those on the undisturbed soil. Therefore, the foot prints were marked by the slip of the foot, but soil compaction scarcely occurred. One year later, the depth of the foot prints were reduced by about 10cm, and surface landslides didn't occur. The values of cone index did not vary change. Just after work, the tracks by the tracked vehicle were about 5cm to 10cm in depth. The dug tracks by skidder were the maximum of 43cm in depth. The tracks did not so vary change in four years. Four years later, the values of cone index on the tracks by harvester were similar to those on the undisturbed soil. The dry bulk density on tracks against the undisturbed soil was reduced. But the content of organic matter on tracks was constant and lower than that on the undisturbed soil.

View full abstract

A vehicle for silvicultural operation that has high mobility on steep slope and rough terrain had been developed by Forest Agency. The characteristics of this vehicle are hydro-static transmission (HST), 4 triangle shaped rubber crawlers, articulated steering, stepped axle system, variable tread system, tilted turntable on which the cabin and the boom are mounted, computer aided attitude display system for safety, a rotary saw bush cleaner and a rotary cutter equipment. We conducted tests of this vehicle on FFPRI test field and a clear cut area of national forest. The result indicates high mobility of this vehicle, and 3 big problems, 1. the vehicle easily turn-over to outside when the oprator steers it heavily, 2. the triangle shaped crawlers easily rotate around the crawler-swing arm axle on steep slope or rough terrain, 3. slippery on rough terrain because of rigid crawlers and simple HST distribution. Therefore we discussed the counter plan against these problems. 1. forbiding to swing the boom to outside during steering, 2. adding the rotation stoppers between crawlers and swing arms, 3. changing the HST distribution and add flow divider valves.

View full abstract

"The Multi-storied Forest Management Project" is practiced in Perak State, Peninsula Malaysia, as a part of the JICA's project. The purpose of this study is to promote the development of the multi-storied forests by establishing techniques for felling and hauling the upper-story tree, Acacia mangium. To reduce damage to lower-story trees, a backhoe and an agricultural tractor were adopted in the logging system. The labor productivity was 2.36 m^3/person・day in a multi-storied plot, 2.85 m^3/person・day in a four-row plot, and 3.86 m^3/person・day in an eight-row plot. The decrease of the labor productivity by the multi-storied forest management was caused by the difference of a cutting row number. It was estimated that the presence of the lower-story tree did not exert influence as much. Felling, delimbing and bucking costs were estimated at 12 US$/m^3, skidding costs at 7 US$/m^3 and transportation costs at 28 US$/m^3 as a whole. The results of the trial upper-story tree felling and hauling in the survey clearly proved that logging of the upper-story tree would be technically possible. The optimum forest road density in the multi-story forests area was estimated at 26.5 m/ha. However, this density is likely to change considerably depending on the estimated maintenance and administration costs of forest roads ; its cost in the tropical area is a critical factor which will determine the level of any permanent forest road networks for sustainable forest management.

View full abstract

This study mainly deals with the characteristics of suspended sediment running off from a forest road surface. According to the existing experience model relating to the suspended sediment run off, the amount of the suspended sediment is, at second power, proportional to its run off amount but turned out not to be so practically. Therefore, the experience model is not desirable. By recalculating the conventional opened data, this study shows that the relations between the amount of suspended sediment and its flowing amount can simply be expressed by a linear model. It is also found that the amount of easy-to-flow out increases at a rate of one power of the residual amount on road surface. In this regard, if the run off rate of suspended sediment is inversely proportional to its residual amount, the characteristics of its flow are experimentally examined. The result is that the running off rate of suspended sediment depends upon rainfall intensity and longitudinal slope. More specifically, the running off rate of suspended sediment is proportional to rainfall intensity and increases at a rate of two power of longitudinal slope.

View full abstract

In order to clarify what sort of physical burden forestry-workers have received in daily walking to their working spots, we made an up and downhill walking test on a path of 20 degrees with three kinds of loads by three subjects. Their walking motions were analyzed with the three dimensional movement analyzer, and their reactive forces at knees in the vertical direction and moments at knees were calculated with the multiple-segment biodynamic model in the sagittal plane. The summary of the result is : In case of uphill walking, the knee of the support leg is received the reactive force about equal to his body weight during the swing phase, and the moment is lager than that of downhill walking. In case of downhill walking, the knee of the support leg is received the instantaneous reactive force which is larger than his body weight. The maximum force is 100 to 120% of his body weight in case of carrying a scythe, and is 120 to 130% of his body weight in case of carrying a chain saw.

View full abstract