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.
AbstractŠEVELOVÁ, L., KOZUMPLÍKOVÁ, A.: The numerical model for parametric studies of forest haul roads pavements. Acta univ. agric. et silvic. Mendel. Brun., 2010, LVIII, No. 5, pp. 361-368 Forest roads pavement structures are considered to be low volume roads. These roads serve as a mean of transport of wood and people. Besides they are currently o en used for recreational purpose.The construction of the pavements should be suitable for forest transportation irrespective of their low bearing capacity. These pavement structures are very specifi c for special unbound materials that are used in their construction. To meet the requirements of the pavement designs and simulation analysis the FEM model in the so ware ANSYS was created. This paper compares two material models used for the description of the behaviour of unbound materials. The fi rst is linear elastic according to Hook theory (H model) and the second one is nonlinear plastic model Drucker-Prager (D-P model). ANSYS so ware has been used to create fl exible model based on the parametrers of variable principle. The fl exible model is parametric to realize repeated calculations useful for optimization analysis.parametric study, optimization analysis, FEM, fi nite element method, fi nite element model of pavement, forest pavement roads, construction of pavement roads Specifi ka lesních odvozních cest a jejich význam v lesním hospodářství a zpřístupňování krajiny kladou stále větší důraz na optimalizaci návrhu těchto multifunkčních komunikací. Vozovka, jako vícevrs-tvá konstrukce spolupůsobící s podložím, musí zajišťovat bezpečný a hospodárný provoz motorových vozidel po dobu požadované životnosti při dané intenzitě dopravního zatížení. Stávající klasické ná-vrhové metody pro dimenzování účelových komunikací jsou založeny na znalosti kalifornského poměru únosnosti podloží, označovaného jako CBR (kalifornský index únosnosti podloží (EN 13286-47)), empirii a experimentu. Experimentální měření a zkoušky dodávají sice velmi důležité podklady a informace o vlivu zatížení a klimatických jevů na vozovky, ale jsou podmíněny realizací na skuteč-ných modelech s vysokou fi nanční náročností. Při-tom např. neumožňují analyzovat stav napjatosti konstrukčního systému vozovka -podloží, zachytit efekty přetížení únosnosti, predikovat chování nových materiálů apod.Vhodným a progresivním nástrojem pro analýzu těchto problémů jsou parametrické studie a spolehlivostní analýzy (Florian, 2005), které umožňují vyšetřovat vzájemné spolupůsobení jednotlivých částí systému vozovka -podloží, vyčíslit míru vlivu faktorů způsobujících proměnlivost jeho chování nebo zahrnout do výpočtu náhodnou proměnlivost vlastností vstupních charakteristik. Současná geotechnická praxe však nedisponuje vhodným numerickým modelem, který je nedílnou součástí těchto analýz, přestože návrhy konstrukcí jsou při využití numerických metod ekonomičtější (Ravaska, 2002; Gaba a kol., 2002) a poskytují reálnější představu o chování konstrukce.Cílem probíhajících prací je vytvořit vhodný numerický model, jenž ...
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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 diff erent amounts of water. Thus modulus of elasticity (Young modulus) of diff erent materials including recycled ones can be measured under the diff erent conditions of horizontal and vertical stresses and under the diff erent 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 diff erent 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.
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