Comparison of field and laboratory models of the load bearing capacity in coffee plantations

Abstract

Precompression stress is an important property for assessment of tropical soil structure sustainability and is often determined in laboratory tests. The objective of this study was to compare the load bearing capacity models obtained with controlled moisture in laboratory and those obtained with natural field moistures determined a long one year. The evaluation of soil structural sustainability follows four distinct steps: soil sampling in the field, uniaxial compression test of the samples in the laboratory, determination of precompression stress and estimation of the load bearing capacity models. Laboratory estimates of precompression stress were obtained from moisture controlled in laboratory and from natural moisture determined in a field a long one year. In this process, the soil samples were saturated by capillarity with distilled water in laboratory, and after 48 hours, the samples were air dried to obtain the different moisture contents. Then, the precompression stress was determined for this both conditions. To verify if the load bearing capacity models obtained with controlled moisture in laboratory may represent the load bearing models obtained with natural field moisture, these models were compared using the homogeneity test procedure. It was observed that 75% of field models analyzed were similar to the laboratory models. Thus, due to the similarity on the load-bearing capacity models obtained using natural (field) or controlled (laboratory) moisture contents, the assessment of the soil structure sustainability can be done using both methods.Index terms: Agricultural traffic, Coffea Arabica L., homogeneity test, precompression stress. RESUMOPressão de pré-consolidação é uma importante propriedade na avaliação da sustentabilidade estrutural do solo e é determinada em testes de laboratório. Neste estudo, objetivou-se comparar modelos de capacidade de suporte de carga obtidos com umidade controlada em laboratório e com umidade natural de campo ao longo de um ano. A avaliação da sustentabilidade estrutural do solo ocorreu em quatro etapas: coleta de amostras de solo indeformado, ensaio de compressão uniaxial das amostras em laboratório, estimativa da pressão de pré-consolidação e obtenção dos modelos de capacidade de suporte de carga. As estimativas da pressão de pré-consolidação de laboratório e de campo foram obtidas com umidades controladas em laboratório e com umidade de campo, respectivamente, ao longo de um ano. No laboratório, a saturaçaõ das amostras se deu por capilaridade, com água destilada e depois de 48 horas, essas amostras foram secas ao ar para obter diferentes valores de umidade. Em seguida, realizou-se o ensaio de compressão uniaxial dessas amostras e a pressão de pré-consolidação foi determinada para as duas condições aqui proposta. Para verificar se os modelos de capacidade de suporte de carga com umidade controlada em laboratório podem representar os modelos de capacidade de suporte de carga de umidade natural, esses modelos foram comparados utilizando o teste de homogeneida...

Soil compaction during harvest operations in five tropical soils with different textures under eucalyptus forests

“…The susceptibility of soils to compaction and the extent of soil compaction can be evaluated with different properties of the soil, such as bulk density, porosity, penetration resistance, hydraulic conductivity (Ampoorter et al, 2010;Silva et al, 2011;Moreira et al, 2012;Braga et al, 2013;Lopes et al, 2015;Silva et al, 2016), and more recently, the precompression stress (Araujo-Junior et al, 2011;Figueiredo et al, 2011;Pacheco;Cantalice, 2011;Ajayi et al, 2013). Precompression stress is generally considered as (a) an indicator of the soil mechanical strength (Ajayi et al, 2013); (b) the maximum pressure that should be applied to the soil to prevent compaction (Severiano et al, 2010;Araujo-Junior et al, 2011), and (c) the required pressure by the root system to enable the root elongation (Iori et al, 2013). The use of precompression stress as an indicator of soil structure sustainability is based on the fact that it divides the soil compression curve into regions of elastic (recoverable) deformations and plastic (non-recoverable) deformations (Oliveira et al, 2011;Vasconcelos et al, 2012;Iori et al, 2013).…”

“…Precompression stress is generally considered as (a) an indicator of the soil mechanical strength (Ajayi et al, 2013); (b) the maximum pressure that should be applied to the soil to prevent compaction (Severiano et al, 2010;Araujo-Junior et al, 2011), and (c) the required pressure by the root system to enable the root elongation (Iori et al, 2013). The use of precompression stress as an indicator of soil structure sustainability is based on the fact that it divides the soil compression curve into regions of elastic (recoverable) deformations and plastic (non-recoverable) deformations (Oliveira et al, 2011;Vasconcelos et al, 2012;Iori et al, 2013).…”

Influence of field slope and coffee plantation age on the physical properties of a red-yellow Latosol

“…We observed that the youngest and oldest plantations had worst soil physical properties. During the early stages of the establishment of the coffee plantation (0-2 years), the impact of soil disturbance by tillage prior to the establishment of the coffee plantation (Iori et al, 2013) is still evident on the soil structure. On the other hand, the physical property of the oldest coffee plantation (33 years) was remarkably altered by accumulated traffic and lower soil organic matter content.…”

Desenvolvimento, Automação E Desempenho De Um Consolidômetro Com Interface Homem-Máquina

“…Iniciativas como essas têm feito da modelagem e da predição da Capacidade de Suporte de Carga do Solo (CSCS) uma proposta viável e exequível, mesmo que ainda praticada por um grupo restrito de pesquisadores no Brasil (Silva et al, 2003a;Severiano et al, 2008;Iori et al, 2013;Dias Júnior et al, 2005;Araujo-Junior et al, 2011;Pais et al, 2013).…”