Penetrômetro Combinado com Sensor de Umidade por TDR para Estudo da Compactação dos Solos.

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Determination of phase-volume fractions from tomographic measurements in two-phase systems

A method is proposed to determine the phase-volume fractions in tomographic representations of two-phase systems. The method is applicable in cases where no independent mean values for the phase-characteristic property (a) are available, such as in standard X-ray computed tomography (CT) using a polychromatic source. The proposed procedure is based on ®tting a sum of three parametric expressions to the histogram of a-values. The terms include two normal probability-density functions to account for noisy pure-phase values, and an analytical expression to account for intermediate values due to interface-containing voxels and blurring. To test the method, it was applied to several X-ray CT data sets of two-phase systems with known volume fractions and varying a-ranges, including a system with only about one standard deviation dierence between the mean phase a-values, i.e., with substantial overlap between the noisy pure-phase distributions. The accuracy for the considered cases was found to be approximately 2 vol% or better. As an example, the proposed ®tting procedure was used to determine the representative elementary volume needed for porosity estimation of a porous medium consisting of 0.5-mm glass beads.

Calibração e uso de uma sonda combinada tensiômetro/TDR.

A curva de retenção da água no solo é uma relação entre a umidade volumétrica e a tensão matricial do solo. Essa relação varia amplamente de solo para solo e tal variação depende fatores ligados aos valores de tensão superficial. Para baixos valores (0 a 1 bar) a dependência maior é em relação à capilaridade e à distribuição dos tamanhos de poros, portanto, fortemente da estrutura do solo.bitstream/CNPDIA/9714/1/CT39_2000.pd

Grapevine root distribution in drip and microsprinkler irrigation.

Grape (Vitis vinifera L.) yield and its quality are dependent of the root system. Root distribution information is also valuable for soil and water management. An analysis of methods to evaluate the root distribution of grapevines for both, drip and microsprinkler irrigation in a Typic Acrustox is presented for the table grape cv. Italia grafted on the rootstock IAC-313, in Northeastern Brazil. Measured root parameters using the monolith method were root dry weight (Dw) and root length density (Lv), while root area (Ap) was estimated using the soil profile method in combination with digital image analysis. For both irrigation systems, roots were present to the 1 m soil depth and extended laterally to 1 m distance from the trunk, but grapevines irrigated by microsprinkler dhowed greater root presence as the distance from the trunk increased. Values of Ap were reasonably well correlated to Dw and Lv. However, correlation values were higher when fractional root distribution was used. The soil profile method in combination with image analysis techniques, allows proper grapevive root distribution evaluation

Estimation of the hydraulic parameters of unsaturated samples by electrical resistivity tomography

In situ and laboratory experiments have shown that electrical resistivity tomography (ERT) is an effective tool to image transient phenomena in soils. However, its application in quantifying soil hydraulic parameters has been limited. In this study, experiments of water inflow in unsaturated soil samples were conducted in an oedometer equipped to perform three-dimensional electrical measurements. Reconstructions of the electrical conductivity at different times confirmed the usefulness of ERT for monitoring the evolution of water content. The tomographic reconstructions were subsequently used in conjunction with a finite-element simulation to infer the water retention curve and the unsaturated hydraulic conductivity. The parameters estimated with ERT agree satisfactorily with those determined using established techniques, hence the proposed approach shows good potential for relatively fast characterisations. Similar experiments could be carried out on site to study the hydraulic behaviour of the entire soil deposi

Digital image analysis of root distribution towars improved irrigation water and soil management: grapevine and date palm study cases.

It is presented two study cases about the approach in root analysis at field and laboratory conditions based on digit-~lilJ\}"3cge analysis. Grapevine (Vitis vinifera L.) and date palm (Phoenix dactylifera L.) root systems were analyzed by both the monolith and trench wall method aided by digital image analysis. Correlation between root parameters and their fractional distribution over the soil profile were obtained, as well as the root diameter estimation. Results have shown the feasibility of digital image analysis for evaluation of root distribution

Simplified Multistep Outflow Method to Estimate Unsaturated Hydraulic Functions for Coarse-Textured Soils

Although the multistep outfl ow (MSO) method is well suited for the estimation of soil hydraulic properties by inverse solution techniques, this method has not been widely adopted because it requires advanced instrumentation and is time consuming. Th e objective of this study was to develop a modifi ed version of the multistep outfl ow technique that largely simplifi es laboratory procedures and reduces costs and time. Th e numerical inversion procedures require applying user-friendly HYDRUS soft ware to estimate fi tting parameters for soil water retention and unsaturated hydraulic conductivity curves. Whereas values of saturated water content and saturated hydraulic conductivity must be measured independently, the remaining functional parameters are estimated using an inverse solution of a transient drainage experiment using multiple suction steps and a hanging water column, with drainage outfl ows measured during drainage. A comparison test showed that the simplifi ed experiment without tensiometric measurements provided suffi cient information in the parameter identifi cation compared with a traditional pressure outfl ow experiment with tensiometric measurements for an Oso Flaco sand and a loamy sand fi eld soil in the suction range of 0 to 17 kPa