The Effect of Contact on the Filter Paper Method for Measuring Soil Suction

The filter paper method is one of the most commonly used and critiqued techniques for measuring soil suction. However, many aspects related to its use still require some clarification. The results of a comprehensive study on the effect of the contact between the soil grains and soil water and the filter paper are presented herein. We investigated the influence of the equilibration time, the texture of the porous material and the degree of contact, or lack thereof, between the soil grains and the filter paper using Miamian #42 and three different types of porous material. To enhance the difference between the total suction and the matrix suction, osmotic suction was induced by saturating the specimens with a sodium chloride solution.

Modeling field load tests in lateritic unsaturated soil

Many models for unsaturated soil have been developed in the last years, accompanying the development of experimental techniques to deal with such soils. The benchmark of the models for unsaturated soil can be assigned to the Barcelona Basic Model (BBM) now incorporated in some codes such as the CODE_BRIGHT. Most of those models were validated considering limited laboratory test results and not much validation is available considering real field problems. This paper presents modeling results of field plate load tests performed under known suction on a lateritic unsaturated soil. The required input data were taken from laboratory tests performed under suction control. The modeling nicely reproduces field tests allowing appreciating the influence of soil suction on the stress-settlement curve. In addition, wetting induced or collapse settlements were calculated from field tests and were nicely duplicated by the numerical analysis performed.

Evaluation of Electrical Resistivity in a Tropical Sandy Soil Compacted

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Shear strength of a natural and compacted tropical soil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Temperature Effects on Suction Measurement Using the Filter Paper Technique

This paper presents the results of an experimental study of thermal effects on filter paper calibration curves used to obtain the soil suction. When the temperature is significantly different from ambient values, it is essential to consider the influence of temperature on the filter paper calibration curves to obtain a reliable soil suction measurement. The calibration curve of Whatman No. 42 filter paper was determined at 10 degrees C, 25 degrees C, and 50 degrees C using the vapor equilibrium technique with sodium chloride solutions at different concentrations and the axis translation technique. The experimental results showed a major influence of temperature on the filter paper calibration curves. Using the obtained experimental data a calibration equation was proposed, taking into account the effect of temperature. The obtained calibration curves were then used to determine the soil water retention curve of kaolin clay, which showed lower retention capacity at higher temperatures.

Laboratory and field investigation of the performance of suction drains, a novel low-carbon technology for ground stabilization

Con riferimento alla realizzazione di tunnel per servizi interrati, l’incertezza che contraddistingue il quadro geologico, oltre che incidere sui costi, riveste un ruolo chiave nella progettazione preliminare. Sebbene un’approfondita caratterizzazione geotecnica e geologica del volume di terreno inerente l’opera di scavo sia generalmente parte integrante del progetto, non è comunque possibile eliminare del tutto tali incertezze per via dell’estensione del volume interessato oltre che per la disomogeneità che sempre contraddistingue il terreno. Generalmente, investigazioni in corso d’opera e interventi di stabilizzazione devono essere previsti per contenere i costi di perforazione ed ottimizzare la progettazione. Ad esempio, tra i metodi di esplorazione geotecnica figurano i tunnel pilota, i quali sono in grado di garantire un’ottimale caratterizzazione del quadro geotecnico del sottosuolo. Con riferimento agli interventi di stabilizzazione del terreno, adottabili laddove una perforazione tradizionale non consentirebbe il tunnelling, vi è un vasta gamma di scelta. Pertanto, da una prima analisi delle problematiche connesse al tunnelling emerge che la stabilizzazione delle facce di scavo riveste un’importanza e un risconto applicativo di prim’ordine. Questa tesi si inserisce all’interno di un progetto che promuove un’innovativa ed economica tecnica di stabilizzazione dei tunnel per suzione tenendo quindi conto dell’influenza della suzione sulla coesione non drenata.

Effects of slope inclination on the rain-induced instability of embankment slopes

Rainfall has been identified as one of the main causes for embankment failures in areas where high annual rainfall is experienced. The inclination of the embankment slope is important for its stability during rainfall. In this study, instrumented model embankments were subjected to artificial rainfalls to investigate the effects of the slope inclination on their stability. The results of the study suggested that when the slope inclination is greater than the friction angle of the soil, the failure is initiated by the loss of soil suction and when it is smaller than the friction angle of the soil, the failure is initiated by the positive pore water pressure developed at the toe of the slope. Further, slopes become more susceptible to sudden collapse during rainfall as the slope angle increases.

Seafloor-riser interaction model

Fatigue stresses associated with extreme storms, vessel movements, and vortex-induced vibrations are critical to the performance of steel catenary risers. The critical location for fatigue damage often occurs within the touchdown zone, where cyclic interaction of the riser with the seabed occurs. Developing a model for seabed stiffness requires characterization of a number of complex nonlinear processes including trench formation, nonlinear soil stiffness, soil suction, and breakaway of the riser from the seafloor. The analytical framework utilized in this research considers the riser-seafloor interaction problem in terms of a pipe resting on a bed of springs, the stiffness characteristics of which are described by nonlinear load-deflection (P-y) curves. The P-y model allows for first penetration and uplift, as well as repenetration and small range motions within the bounding loop defined by extreme loading. The backbone curve is constructed from knowledge of the soil strength, the rate of strength increase with depth, trench width, and two additional parameters, while three parameters are necessary for the cyclic response. © ASCE 2009.

土壤结构改良剂影响下的土壤水分有效性研究

以聚丙烯酰胺(PAM)与磷石膏(PG)为土壤结构改良剂,利用离心机法,测定土壤水分特征曲线,从分析土壤的吸水能力和持水能力的角度出发,研究土壤结构改良剂对土壤水分有效性的影响。研究结果表明,土壤的吸水能力、持水能力与释水能力均表现出与用量密切相关;在使用土壤结构改良剂的情况下,仍然可用van Genuchten方程很准确的模拟土壤吸力与含水率之间的关系,即可作为使用土壤结构改良剂后的土壤水分特征曲线的模拟表达式;在试验的用量范围内,土壤结构改良剂的使用不会影响植物对水分的吸收和利用。

Avaliação da erodibilidade pelo método Inderbitzen em solo não saturado da região de Bauru - SP

Pós-graduação em Engenharia Civil e Ambiental - FEB

Avaliação da resistência ao cisalhamento de um solo tropical não saturado

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Análise de microestrutura e de características geotécnicas de misturas de resíduo de polimento de porcelanato e solo

Brazil is a country in development, rich in natural resources. In order to grow sustainably, it is necessary to Brazil to preserve its environment, which is an expressive challenge, especially to industries, such as those producing ceramic materials. This study was developed using Porcelain Tile Polishing Residue (RPP) in blends with soil to build compacted fills. This residue is a slurry generated during the polishing process of porcelain tiles and contains powdery material from the polished tile, the abrasives used during the process and cooling water. The RPP was collected from a private company located in Conde/PB and it was mixed with a sandy-clayey soil, to build the fills. Laboratorial tests were conducted with pure soil, pure RPP and blends in proportions of 5%, 10%, 15% and 20% of RPP in addition to the dry mass of pure soil. The Chemical and Physical Characterization tests performed were: specific solid weight, grain size distribution, laser analysis of grain size distribution, Atterberg limits, X ray fluorescence, X ray diffraction, scanning electron microscopy and soil compaction,. The materials and blends were also compacted and direct shear tests and plate load tests were performed. Plate load tests were conducted using a circular plate with 30 cm diameter, on specimens of pure soil and 5% blend, compacted in a metallic box inside the Soil Mechanics Laboratory of the Federal University of Rio Grande do Norte, Brazil. Both mechanical tests performed were conducted under inundated conditions, willing to reduce the influence of soil suction. An evaluation of the results of the tests performed shows that RPP is a fine material, with grain size distribution smaller than 0,015mm, composed mainly of silica and alumina, and particles in angular shape. The soil was characterized as a clayey sand, geologically known as a lateritic soil, with high percentages of alumina and iron oxide, and particles with rounded shape. Both the Soil and the blends presented low plasticity, while the residue showed a medium plasticity. Direct shear tests showed that the addition of RPP did not cause major changes into blends’ friction angle data, however, it was possible to note that, for the proportions studied, that is a tendency of obtain lower shear stresses for higher percentages of RPP in the blends. Both pure soil and 5% mixture showed a punching disruption for the Plate load test. For this same test, the allowable stress for 5% mixture was 44% higher than the pure soil, and smaller vertical settlement results for all stresses.

Análise de microestrutura e de características geotécnicas de misturas de resíduo de polimento de porcelanato e solo

Brazil is a country in development, rich in natural resources. In order to grow sustainably, it is necessary to Brazil to preserve its environment, which is an expressive challenge, especially to industries, such as those producing ceramic materials. This study was developed using Porcelain Tile Polishing Residue (RPP) in blends with soil to build compacted fills. This residue is a slurry generated during the polishing process of porcelain tiles and contains powdery material from the polished tile, the abrasives used during the process and cooling water. The RPP was collected from a private company located in Conde/PB and it was mixed with a sandy-clayey soil, to build the fills. Laboratorial tests were conducted with pure soil, pure RPP and blends in proportions of 5%, 10%, 15% and 20% of RPP in addition to the dry mass of pure soil. The Chemical and Physical Characterization tests performed were: specific solid weight, grain size distribution, laser analysis of grain size distribution, Atterberg limits, X ray fluorescence, X ray diffraction, scanning electron microscopy and soil compaction,. The materials and blends were also compacted and direct shear tests and plate load tests were performed. Plate load tests were conducted using a circular plate with 30 cm diameter, on specimens of pure soil and 5% blend, compacted in a metallic box inside the Soil Mechanics Laboratory of the Federal University of Rio Grande do Norte, Brazil. Both mechanical tests performed were conducted under inundated conditions, willing to reduce the influence of soil suction. An evaluation of the results of the tests performed shows that RPP is a fine material, with grain size distribution smaller than 0,015mm, composed mainly of silica and alumina, and particles in angular shape. The soil was characterized as a clayey sand, geologically known as a lateritic soil, with high percentages of alumina and iron oxide, and particles with rounded shape. Both the Soil and the blends presented low plasticity, while the residue showed a medium plasticity. Direct shear tests showed that the addition of RPP did not cause major changes into blends’ friction angle data, however, it was possible to note that, for the proportions studied, that is a tendency of obtain lower shear stresses for higher percentages of RPP in the blends. Both pure soil and 5% mixture showed a punching disruption for the Plate load test. For this same test, the allowable stress for 5% mixture was 44% higher than the pure soil, and smaller vertical settlement results for all stresses.