journal of forest science

Non-solid roadway degradation of forest roads from theoretical
and practical aspects
L. ZELINKA
Technical University, Forestry Faculty, Zvolen, Slovak Republic
ABSTRACT: This article deals with the degradation process of non-solid roadways of forest roads with bituminous surface
that was investigated for 10–15 years. The roadway degradation was described by determining the value of roadway
deflection and for better orientation it was calculated as a change in operating performance, namely as the number of standard
axles during the time of roadway use. The results indicate that the degradation process is gradual, of non-linear character.
The calculated values will be used to determine “wear coefficients” which will help to plan the optimal time of
roadway repair (overlay).
Keywords: degradation; theory; forest roads; course
BRIELY ON ROADWAY DEGRADATION
THEORY
The roadway degradation (GSCHWENDT 1994) is taken
to mean gradual deterioration of the roadway condition
due to wheel traffic under certain climatic conditions
(especially in spring time). Climatic conditions and the
quality of roadway subsoil influence deterioration of the
roadway condition, which results in deterioration of parameters
which comprehensively define the roadway serviceability
as well as the roadway mechanical efficiency
(construction bearing capacity).
Assumptions about development and changes in the
parameters defining the roadway condition are used in
roadway management to draw up renewal and rehabilitation
plans, to make decisions and to adopt roadway renewal
strategy.
THEORETICAL ASSUMPTIONS
The real course of roadway degradation can be determined
either from the roadway degradation as whole
(it is more objective) or from a change in individual parameters
of roadway serviceability which can also be simulated.
Assumed changes in parameters (of the general roadway
condition) in dependence on time or repetition of
the standard loading are expressed by degradation model.
Degradation function is a mathematical expression of
changes in roadway parameters or changes in the general
roadway condition according to a certain degradation
model and assumptions in dependence on time or repetition
of loading.
JOURNAL O OREST SCIENCE, 47, 2001 (7): 314–321
In roadway management we need the following models
and functions of degradation for:
– new roadways,
– roadways under reconstruction and renewal,
– existing roadways in use with different wheel traffic
and under different climatic conditions.
The evaluation of economic effects is connected with
determination of a suitable period for roadway renewal
from the technical view. Technical and economic decisions
have to be taken in accordance with maintenance
and renewal strategies.
To determine the roadway degradation and to construct
the model we usually determine and evaluate the roadway
parameters on a certain section by repeated measurements.
We can express the changes in average values
in dependence on time or wheel traffic after statistical
processing of parameters on a certain section of the road.
The relation of absolute values of roadway and time or roadway
and wheel traffic parameters is used for expression of
the real course of roadway degradation in real time.
The relations between relative values of variables are
used for the mathematical expression of roadway parameter
changes in dependence on time or wheel traffic.
Distribution of models results from segregated and
aggregated roadway evaluation to show the roadway serviceability
and to evaluate the condition of roadway construction.
According to the formulation of degradation model
(and degradation function) there are:
a) deterministic models – based on the relations and regularities
valid for a physical model of roadway,
b) stochastic models – based on the calculation of the
probability of occurrence of the observed condition.
314
J. FOR. SCI., 47, 2001 (7): 314–321