A contribution to the detection of sliding resistance and calculation of critical slope inclination at timber dragging by horse

The paper deals with the determination of sliding resistance at dragging timber by horse and with the calculation of critical slope inclination in situations of threatening spontaneous movement of timber. These are reasons why the horse should not be used in such conditions. Different conditions of skidding trail surface are considered in winter and summer periods of the year. Sliding resistance was determined by using an original methodology in which the acting forces are measured by strain gauges directly at the timber dragging by horse. It was found out that the coefficient of sliding resistance cannot be determined as one concrete figure but rather as an interval of values since it is considerably variable with the character of terrain and character of the surface of dragged log. This is why the critical slope inclination should be determined in a certain interval, too, in order to include the measure of acceptable risk. The measure of acceptable risk is defined by using an auxiliary coefficient of safety whose value should range in the interval from 0.5 to 1.0 as a value indirectly proportional to the magnitude of sliding resistance coefficient.