INVESTIGATION OF THE LENGTHWISE DURABILITY OF A PACKAGED BILEVEL RAFTING UNIT

Abstract

Introduction. Usage of bi-level packaged rafting units offers sufficient advantages in round wood transportation along small and medium size rivers, due to decrease of logistic costs for small logging enterprises. The aim of the present work is to obtain information necessary for evaluation and securement of lengthwise durability of involved rafting units. Materials and methods. The study is based on the approved theoretical technique, tested and validated by the authors when solving other similar tasks. Results. It was determined that the mean force of lengthwise log translocation resistance in a package of a rafting unit depends on the factors: height, length, filling and form coefficients of packages, average log diameter, wood density, friction coefficient, angle of interior friction. The value of the above mentioned force was introduced as a criterion  for integrated assessment of   lengthwise durability of a package. This value was suggested as the lengthwise durability criterion of the package. The criterion allows the complex evaluation of the lengthwise durability. The equations and graphic charts for criterion relevant to packages in upper and lower levels are developed. The criterion value for a rafting unit as a whole to be determined as a mean number among all packages. It was found out that the lengthwise durability criterion of a package increases linearly depending on the factors: length, height, filling coefficient, log diameter, friction coefficient. Relation to angle of interior friction: inverse, close to linear. The package lengthwise durability decreases depending on wood density and coefficient of package form increase. Equations for determination of force counteracting to relative lengthwise slippage of packages in a rafting unit were developed. It was noted that counteracting force increases linearly depending on increase of coefficient of friction, volume of logs in a package and decrease of wood density. As a rule, counteracting force for a package is significantly higher than average value for single log. Conclusion. It was found out, that lengthwise durability of packages in an upper layer of a rafting unit is significantly higher than the same for the lower level. It is recommended to place packages of small diameter coniferous logs and deciduous species in the upper layer of a rafting unit.