Shear strength of soils is highly affected by moisture conditions (i.e. water content), especially if the soil contains clay materials. Usually the laboratory specimen, which are used to determine shear strength of soil are prepared at water content and dry density same as in the field conditions, without respect to the fact, that the conditions in the future might not remain the same. For the purpose of this study soil specimen were compacted and the optimum moisture content was identified. After compaction soil was tested at the dry side of optimum water content at w = 9 %, 10 % and 11 %. Parameters of shear strength were obtained and used for stability analysis with software GEOSLOPE/W 2012. According to referenced literature, it was expected for the shear strength of the soil to decrease with increasing water content. This hypothesis was not proven for clayey soil from Brno region. Development of values of friction angle and cohesion exhibited anomalous behaviour and such development was found also for values of Factor of safety (FOS) obtained from stability analyses. Results proved the necessity of taking moisture conditions into account, when processing stability analyses, in order to achieve reliable and safe constructions.

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Forest roads are often constructed in environments with low bearing capacity of the subgrade. The subgrade then has an effect on their service life and damage. According to the methodology of the American Association of State Higway and Transportation Officiales AASHTO, the design of pavement is divided into three levels according to the intensity of the traffic load. For pavements with the highest load intensity, preparing the resilient modulus from a cyclic triaxial test is required. For other traffic load classes, including forest roads, the methodology allows the use of the estimate of resilient modulus value determined from other tests. In the laboratory at the Faculty of Forestry, Mendel University of Brno, the method from the Delft University 2009 was tested and subsequently modified, using a standard CBR machine for repeated loading. A total of 276 samples from various types of forest road subgrade from the Czech Republic were tested by the method of repeated loading on the CBR machine, from which the values of the Resilient Modulus were newly labelled M_r,CBR. The results of the statistical analysis showed a large variability of M_r,CBR values and wide intervals of its occurrence for individual types of subgrade. The variability was subjected to analysis and the influence of basic geotechnical parameters on the values of M_r,CBR was analyzed. A fundamental correlation was found between the value of M_r,CBR and the value of the plunger stress, which reached values exceeding the bearing capacity of the soil types using the Delft University method. It is necessary to limit the plunger stress during cyclic loading up to the failure limit or even better to the expected traffic load. The modified procedure results show a more consistent behavior of the modulus.

Low volume roads are widely used all over the world. To improve their quality a FEM computer simulation of their behavior is proposed. The input information about mechanical properties of individual materials is crucial for obtaining results as exact as possible. Among others, the mechanical properties are generally dependent on the state of stress and on humidity conditions. For this purpose the cyclic-load triaxial machine testing of cyclic-load performance of materials seems to be a promising test method. The test specimens can be prepared with different amounts of water. Thus modulus of elasticity (Young modulus) of different materials including recycled ones can be measured under the different conditions of horizontal and vertical stresses and under the different humidity conditions. Using the proposed testing procedure the modulus of elasticity of materials used in the newly built low volume road is obtained under the different state of stress as well as humidity conditions set to standard, dry and fully saturated level. Also recycled materials which are able to replace the traditional materials in the pavement are tested. Obtained values of modulus of elasticity can be used in a FEM study of the newly built road.

Ensuring the efficiency of forest management and the availability of landscape areas requires a quality transport network. However, any structure and its subsequent use generally contributes to a certain disruption of surrounding ecosystems, soil degradation, erosion and changes in vegetation. The presented study analyzes the effects and impacts of the five types of improving materials used to improve the load-bearing capacity of low-volume roads. Two basic types of analyses were performed: the classification of mechanical properties of soil for determining fine clay particle proportions and the chemical testing for pH and carbonate determination. The samples were always collected at three distances from the roadside, at two height levels and in two years: 2012 and 2017. The aim of the study was to quantify the effects of improving materials on the pH changes as well as the carbonate levels, and to compare their changes over the course of five years. Also, we have highlighted the possibilities of “biological tools” (vegetation) to control and minimize the impact of human activities. Vegetative control, or phytoremediation, increases soil resistance to erosion, improves water retention in a landscape and maintains the original balance. It seems to be an effective tool for reduction of the impact of pavement construction materials and technologies on the surrounding environment.

The design and assessment of forest and rural road pavements made from unbound natural and recycled materials require the careful determination of their physical-mechanical properties. The fundamental parameter for characterizing the soil material property is considered to be the resilient modulus M_r. The generally accepted alternative solution for its calculation is the cyclic CBR test, which uses standard CBR testing equipment. To perform tests on intact specimens and under stress conditions corresponding to expected states of stress in a pavement structure, an updated cyclic CBR test is proposed. In contrast to the standard cyclic CBR test, the applied loading force for repeated loadings is not determined in the first loading step by the plunger penetration to the prescribed depth, but by the stress value that is expected in an actual pavement structure. The updated test was verified on 240 tested specimens taken from a total of 40 soil samples belonging to nine soil types according to the USCS system. The resilient modulus results obtained are compared with those obtained using the standard cyclic CBR test and the cyclic triaxial test.