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Search Results: 1 - 10 of 7662 matches for " preconsolidation pressure "
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Estimativa da capacidade de suporte de carga do solo a partir da avalia??o da resistência à penetra??o
Lima, Claudia Liane Rodrigues de;Silva, Alvaro Pires da;Imhoff, Silvia;Le?o, Tairone Paiva;
Revista Brasileira de Ciência do Solo , 2006, DOI: 10.1590/S0100-06832006000200003
Abstract: the preconsolidation pressure, despite the difficulties inherent to its measurement, provides a useful measure of the soil mechanical state for soil management and the planning of mechanization systems. the estimation of the preconsolidation pressure, based on easily measurable soil physical properties, may be relevant to solve some difficulties. the objectives of this study were: (a) to quantify the preconsolidation pressure and soil resistance to penetration measured in the laboratory and the field for a haplustox under orange orchard, and (b) to establish relationships between these physical indicators. sampling and evaluations were carried out on eight consecutive days to observe the natural soil drying. there was a positive, linear, and significant relationship between the preconsolidation pressure and soil resistance to penetration measured in the laboratory as well as in the field. the similarity of the relationships among soil resistance to penetration measured in the laboratory and the field and the preconsolidation pressure allowed affirming that the load support capacity for the haplustox may be estimated from the soil resistance to penetration measured in the field.
Moacir de Souza Dias Junior,Ant?nio do Nascimento Gomes,Sebasti?o da Cruz Andrade,Moisés Rabela Azevedo
CERNE , 2002,
Abstract: One of the limitations to reach sustainable forest development is related to mechanical harvest operations which may cause soil structure degradation. The objectives of this study were: to propose a structure sustainability model of soils cultivated with Eucalyptus spp. and to determine the effect of harvest operations on soil structure. This study was conducted in a Yellow Argisols (PA) cul-tivated with Eucalyptus. The depth 0,125-0,175 m of the PA texture loam/clay presented σp values larger than those of the 0,05-0,10 m depth, for any moisture content (U). In the depth 0,05-0,10 m the equations were statically different and the PA texture sand/loam presented σp values larger than the PA texture loam/clay for larger values of moisture content of 9 kg kg-1. Thus, it is expected thatthe superficial layer of the PA texture sand/loam supports larger pressures than the one of the PA texture loam/clay. The traffic made using the cart with two axes caused structure degradation in some sampled places.
Compressibilidade de um Argissolo Vermelho-Amarelo trafegado e escarificado
Vogelmann, Eduardo Saldanha;Mentges, Marcelo Ivan;Reichert, José Miguel;Rosa, David Peres da;Barros, Cláudia Alessandra Peixoto de;Reinert, Dalvan José;
Ciência Rural , 2012, DOI: 10.1590/S0103-84782012005000004
Abstract: farm machinery wheeling is considered a major source of soil compaction. the use of chisel plow can minimize such effects, but the chisel can cause subsurface compaction. the aim of this study was to evaluate the effect of traffic and is present below the compaction layer thought compressive parameters of soil. the treatments investigated were: no-tillage, no-tillage with additional traffic (traffic intensity of 24.67mg km ha-1), no-tillage chiseling recent implanted, no-tillage with additional traffic and chiseling recent implanted. for the density, void ratio, preconsolidation pressure and coefficient of compressibility determination in the layers 0.0-0.10m, 0.10-0.20m, 0.20-0.30m and 0.30 to 0.40m samples were collected. the treatment no-tillage showed the lowest load support capacity and greater susceptibility to compaction. the traffic intensity of 24.67mg km ha-1 increased bulk density and decreased void ratio until 0.30m depth. the chisel plow did not affect the preconsolidation pressure and coefficient of compressibility of soil layer below the line of action of the chisel tip.
Comparison of estimation methods of soil strength in five soils
Ajayi, Ayodele Ebenezer;Dias Junior, Moacir de Souza;Curi, Nilton;Araujo Junior, Cezar Francisco;Aladenola, Olanike Olaiya;Teixeira Souza, Thiago Tadeu;Inda Junior, Alberto Vasconcellos;
Revista Brasileira de Ciência do Solo , 2009, DOI: 10.1590/S0100-06832009000300002
Abstract: in agriculture, the soil strength is used to describe the susceptibility to deformation by pressure caused by agricultural machine. the purpose of this study was to compare different methods for estimating the inherent soil strength and to identify their suitability for the evaluation of load support capacity, compaction susceptibility and root growth. the physical, chemical, mineralogical and intrinsic strength properties of seven soil samples, collected from five sampling pits at different locations in brazil, were measured. four clay (cs) and three sandy clay loam (scl) soils were used. the clay soils were collected on a farm in santo angelo, rs (28 o 16 ' 16 '' s; 54 o 13 ' 11 '' w 290 m); a and b horizons at the universidade federal de lavras, lavras, mg (21 o 13 ' 47 '' s; 44 o 58 ' 6'' w; 918 m) and on the farm sygenta, in uberlandia, mg (18 o 58 ' 37 '' s; 48 o 12 ' 05 '' w 866 m). the sandy clay loam soils were collected in aracruz, es (19 o 47 ' 10 '' s; 40 o 16 ' 29 '' w 81 m), and on the farm xavier, lavras, mg (21 o 13 ' 24 '' s; 45 o 05 ' 00 '' w; 844 m). soil strength was estimated based on measurements of: (a) a pneumatic consolidometer, (b) manual pocket (non-rotating) penetrometer; and (c) automatic (rotating) penetrometer. the results of soil strength properties were similar by the three methods. the soil structure had a significant influence on soil strength. results of measurements with both the manual pocket and the electric penetrometer were similar, emphasizing the influence of soil texture. the data showed that, to enhance the reliability of predictions of preconsolidation pressure by penetrometers, it is better to separate the soils into the different classes, rather than analyze them jointly. it can be concluded that the consolidometer method, although expensive, is the best when evaluations of load support capacity and compaction susceptibility of soil samples are desired.
Modelagem da capacidade de suporte de carga e quantifica??o dos efeitos das opera??es mecanizadas em um Latossolo Amarelo cultivado com cafeeiros
Silva, Arystides Resende;Dias Junior, Moacir de Souza;Guimar?es, Paulo Tácito Gontijo;Araújo Júnior, Cezar Franciso;
Revista Brasileira de Ciência do Solo , 2006, DOI: 10.1590/S0100-06832006000200002
Abstract: minas gerais state is the largest coffee producer in brazil. the state contributes with over 50 % of the total production, which is for the most part cultivated in the cerrado region. this region is outstanding in coffee production due to the advanced technology in mechanization. consequently, the machine traffic that the soils are subjected to causes concern because of the possibility of widespread soil compaction. our objectives were (a) to propose load support capacity models to a typical dystrophic yellow latosol (lad) cultivated with coffee as a function of preconsolidation pressure and moisture content; (b) to determine, through the use of this model, the influence of soil management operations on the soil structure at three depths, in the dry and rainy seasons. soil samples were taken from three depths (0 to 3, 10 to 13 and 25 to 28 cm); thirty samples were collected where there was no traffic and ten samples collected in the traffic line of each equipment, in august 2002 and march 2003, respectively, to quantify its effects on the soil structure in the rainy and in the dry seasons. the undisturbed soil samples were used in the uniaxial compression test. texture, organic matter, particle density, shrinkage limit, and plasticity limit were also determined. the load support capacity model of the lad is a function of the preconsolidation pressure and moisture content and is expressed by the equation sp = 10(2.72-1.17u) where sp means preconsolidation pressure and u means humidity. the effects of the mechanized operations in the coffee plantation were quantified by the load support capacity model and through its use it was possible to quantify the influence of the management operations in the yellow latosol structure.
Compressibilidade de um solo sob sistemas de pastejo rotacionado intensivo irrigado e n?o irrigado
Lima, C. L. R.;Silva, A. P.;Imhoff, S.;Le?o, T. P.;
Revista Brasileira de Ciência do Solo , 2004, DOI: 10.1590/S0100-06832004000600002
Abstract: increment in pasture productivity has been associated with the understanding of the soil behavior under compression. the objective of this research was to quantify (a) the compression curves and (b) the preconsolidation pressure of the soils under non-irrigated and irrigated short duration grazing systems. ninety-six undisturbed soil samples were taken from the four successive pasture cycles of tanzania grass (panicum maximum jacq.) in a hapludalf. the samples were saturated in water and equilibrated at the matrix potential (y): -10 kpa and then were weighed and submitted to an uniaxial compression test, applying the following pressures: 25, 50, 100, 200, 400, 600, 800, 1,000, 1,300, and 1,600 kpa. results support the hypothesis that there is a difference between the soil compressibility under non-irrigated and irrigated short-duration grazing systems. the higher initial compaction verified in irrigated short-duration grazing system favored the displacement of the uniaxial compression curves for higher bulk density values. the preconsolidation pressure was significantly higher in the fourth pasture cycle under irrigated than under the non-irrigated short duration grazing system.
Método alternativo de avalia??o da press?o de preconsolida??o por meio de um penetr?metro
Dias Junior, M. S.;Silva, A. R.;Fonseca, S.;Leite, F. P.;
Revista Brasileira de Ciência do Solo , 2004, DOI: 10.1590/S0100-06832004000500002
Abstract: soil compression curves are frequently used in compaction studies. these curves describe the relationship between the logarithm of applied pressure and the soil bulk density or void ratio. the preconsolidation pressure divides the soil compression curves into a region of recoverable and a region of unrecoverable deformations. consequently, the preconsolidation pressure has been used as an estimate of soil load support capacity of partially saturated soils. the preconsolidation pressure is laboratory-obtained through the uniaxial compression test which requires sophisticated equipment. besides the time spent on the test realization, it is necessary to use a graphic method or spreadsheet procedure for its determination. an alternative way to minimize this problem would be the calibration of the preconsolidation pressure by other ways of easy and fast achievement. thus, the objective of this study was to propose an alternative evaluation method of the preconsolidation pressure by a penetrometer. for this purpose, the preconsolidation pressures and penetration resistance in the superficial layer of a yellow argisol (pa) and plinthosol (fx) from aracruz (es), brazil, were determined in the laboratory. field tests were carried out with an oxisol (lv) located in belo oriente (mg). the coefficients of determination were significant and varied from 0.88 to 0.99. the equations that relate the preconsolidation pressure (sp) with the penetration resistance (rp) were of the form: sp = a + b (rp). this equation permits the estimation of the preconsolidation pressure as a function of the penetrometer resistance, which may be used in the identification of the soil compaction and as a tool to come to a decision about realizing a particular mechanized operation or not.
Consolid?metro: equipamento pneumático-eletr?nico para avalia??o do estado de consolida??o do solo
Silva, Reginaldo Barboza da;Lan?as, Kleber Pereira;Junior Masquetto, Batista;
Revista Brasileira de Ciência do Solo , 2007, DOI: 10.1590/S0100-06832007000400001
Abstract: preconsolidation pressure (sp) is determined by a consolidation test method, based on the gradual transference of a load onto the soil until all porosity is compressed. the equipment used for this test is a consolidometer, which is not available in brazil, while the models used abroad are very costly. in some cases this situation impairs the access of brazilian researchers and farmers to data of soil load support capacity (slcs). this study had the objective of developing and evaluating an electronic-pneumatic device by which sp can be obtained in the consolidation test. the equipment was developed at the universidade estadual paulista and evaluated in uniaxial tests using specimens of two oxisol horizons (surface and sub surface). the soil density values in the soil compression curves increased showing the variation of specimen strain recalque/ sinkage or displacement in function of the increasing pressure levels and soil moisture. the equipment efficiency was confirmed by the differentiated compression curves and equations obtained for the soil load support capacity models, which were able to detect the different soil consolidation degrees as well as the different sequences of structure tension in each oxisol layer.
Heterogeneidade da compacta??o de um latossolo vermelho-amarelo sob pomar de laranja
Lima, C. L. R.;Silva, A. P.;Imhoff, S.;Lima, H. V.;Le?o, T. P.;
Revista Brasileira de Ciência do Solo , 2004, DOI: 10.1590/S0100-06832004000300001
Abstract: the heterogeneity in soil compaction induced by different traffic intensities can reduce the productivity of citrus trees. the objective of this research was to quantify the compression index (ci) and the preconsolidation pressure (sp) in different sampling positions (row, between wheel track, wheel track, and canopy projection) to evaluate the compaction heterogeneity in a haplustox under an orange orchard. the sampling was carried out at forty randomly distributed sites (ten samples in each position). the samples were water saturated and equilibrated at a water potential (y) of -10 kpa. thereafter, they were weighed and submitted to a uniaxial compression test under the following pressures: 25, 50, 100, 200, 400, 600, 800, 1,000, 1,300, and 1,600 kpa. the results indicated that the sp was the most sensitive indicator to evaluate the compaction heterogeneity induced by the traffic of agricultural machinery in areas cultivated with citrus trees. soil compaction increased in the following order: row, between wheel tracks, at the wheel track, and canopy projection position.
Levels of induced pressure and compaction as caused by forest harvesting operations
Martins, Paula Cristina Caruana;Dias Junior, Moacir de Souza;Carvalho, Josemar da Silva;Silva, Arystides Resende;Fonseca, Sebasti?o Machado;
CERNE , 2013, DOI: 10.1590/S0104-77602013000100011
Abstract: this study aimed to determine levels of pressure and compaction induced by forest harvesting operations in a red latosol (lv) under planted eucalyptus. undisturbed soil samples were collected from layers 0-3 and 15-18 cm and then used in a uniaxial compression test. sampling was done before and after harvesting operations. equipment being evaluated included: harvester, feller buncher, forwarder, self-loading adapted tractor, standard truck, wide-tire truck and grapple saw. average pressures induced by the grapple saw were 320 kpa and 272 kpa, causing compaction in 80% and 20% of samples respectively from layers 0-3 cm and 15-18 cm, which indicates substantial degradation of soil structure in areas where timber is processed. in layer 0-3 cm, average pressures induced by the harvester and by the feller buncher were 240 kpa and 263 kpa respectively, while in layer 15-18 cm pressures were 234 kpa and 239 kpa respectively. the feller buncher caused higher soil compaction than the harvester in layer 0-3 cm, yet in layer 15-18 cm they had similar behavior. all timber forwarding equipment led to soil compaction. the wide-tire truck was the forwarding implement promoting the highest rate of compaction, in both residue conditions. traffic intensity 7 promoted the highest rate of soil compaction.
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