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Infl uence of overconsolidation ratio on shear modulus in cohesive soils. The determination of initial shear modulus in soils from shear wave velocity measurements needs the application of bender elements in laboratory investigations. Both shear wave velocity and initial shear modulus depends on many factors, especially mean effective stress, void ratio and stress history. Results of laboratory test performed on cohesive soils samples are presented in this paper.
Paper presents the course of soil deformations during operation of rotary cultivator working element determined on the basis of developed mathematical model. Moreover, the changes of geometrical and energetic parameters characterizing rotary cultivator operation in the soil of various parameters were considered. The results regarding driving torque and power requirement may be a basis for selecting essential construction parameters of rotary cultivators as well as for determining their optimum operation parameters.
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Wyznaczanie modułu odkształcenia postaciowego G0 w iłach. W pracy została przedstawiona próba określenia modułu odkształcenia postaciowego silnie prekonsolidowanego gruntu spoistego – iłu pochodzącego z poletka doświadczalnego Stegny w Warszawie, z wykorzystaniem badań terenowych i laboratoryjnych. W pracy zaprezentowano i porównano wyniki badań wykonanych in situ stożkiem sejsmicznym SCPTU oraz wyniki badań laboratoryjnych przeprowadzonych na próbkach gruntu konsolidowanych izotropowo wykonanych w aparacie trójosiowego ściskania wyposażonym w piezoelementy i w kolumnie rezonansowej.
Mathematical model describing the action of a narrow tillage tool was used to analyse the effect of selected soil and tool parameters on that action. Working resistance and the indices of soil deformation (critical depth, cracking angle) were investigated. Working resistance of a narrow tool was affected mostly by the soil internal friction angle and less by the soil cohesion and bulk density and increased with the rise of considered soil parameters. The cracking angle rose with the soil cohesion only while it decreased with increasing other soil/tool parameters. Critical depth increased with internal friction angle and cohesion of the soil and it decreased with rising of the other factors.
In this review paper the changes of hydraulic gradient in the flow characteristics is presented. The analysis has been obtained in the value of loaded effective stress in soft soil. The relationship between flow velocity and hydraulic gradient is nonlinear. The results of soft soils used to the analysis were obtained in laboratory using the flow-pump technique. To describe the permeability characteristics the prelineary and postlineary phases should be considered. The prelineary phase characterises the flow at very low hydraulic gradient which usually appears in situ. The permeability characteristics show the strong changes of hydraulic gradient under different values of effective stress.
W pracy przedstawiono trzy sposoby formułowania modeli fizycznych: deterministyczny, statystyczny i probabilistyczny. Pokazano na przykładzie modeli odkształceń gleb, że już w momencie formułowania definicji naprężenia i odkształcenia podejmuje się decyzję wyboru aparatu matematycznego.
The paper discussed the application of mercury porosimetry method to investigations of agricultural materials. Most of these investigations concerned the soil materials. Pores systems of soils were characterized taking into account the pore classifications. The effects of polyamide sorbent on sandy and clay soils microstructure were investigated. Also the influence of mechanical deformations on the dimension of soils particle aggregates and on the microstructure of soil were described. The microporosity of humic fractions (humic acids and ß-humus) and internal porosity of wheat grain and starch extrudates were described.
The infl uence of loading rate on deformation of organic soil. In this review paper the changes of deformation parameters in the organic soils characteristics are presented. The main view was put on the infl uence of loading rate on presented soils. The results of soft soils used to the analysis were obtained in laboratory using oedometer tests. To describe the deformation process of organic soils two kinds of oedometer tests were held: with gradually increasing load and constant load. Both techniques show the wide range of factors determine deformations and settlements of organic subsoil, among which important are also the velocity and the value of loading rate.
Soil, as a tractive surface for agricultural tractors as well as military and off-road vehicles, is required to withstand dynamic loads occuring under wheels or tracks. mechanical properties of soil medium result in dependence between load, velocity of sytain and stress- deformation relationships. These information are of the major importance when considering soil compaction as well as tractive performaces of the vehicles. Having analyzed results pulished by many researches, the autors of this work haveconcluded the lack of a proper method for soil stress- deformation measurements. Therefore, the aim of the work is to desing and research some new methods of soil stress- deformation measurements. In the second chapter results of experimental research with a SST transducer are shown. The transducer allows to measure strasses for complete soil stress state calculations. Additionally, a mechanical system was used for soil deformations measurements in the three direction in space.The third chapter contains numerous details on desing of an improved version of the measuring system with an triaxal head. Soil deformations are measured with a novel method, which uses laser and a CCD camera.The next chapter describes another version, which is suitable for field experiments. Detailed descriptions of field procedures are given. A system for soil stress- deformation measurements developed with laser and optical fibers is shown in the last numbered chapter. There are also described some future designs, containing nanotechnology and telemetries.
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