The Densification of Loose Sand Using Compaction Piles

Two case histories of densification of loose sandy soils using compaction piles are analyzed. The sandy soils were improved to support heavily loaded structures using shallow foundations. The technique used was deep compaction through compaction piles driven with Franki -type equipment, and shallow compaction by vibratory plate. Results of the compaction processes are presented and discussed to provide guidance for future projects. The analysis includes distance from the compaction pile, initial relative density, time delay for results verification after compaction, and depth. The results of densification demonstrate the method is efficient

Método del papel de filtro para la medida de la succión del suelo

The capillary pressure of the soil (i.e., the pressure difference between air and water components in soil voids) is a key variable in the analysis of the hydro-mechanical behavior of unsaturated soils. Therefore a simple and economical laboratory method for the measurement of the capillary pressure of the soil (also known as soil matric suction, the reference being the atmospheric pressure), even if a degree of approximation is involved, is of considerable value. The filter paper method calculates soil suction indirectly by measuring the gravimetric water content of the filter paper at equilibrium that is related to soil suction through a predetermined calibration curve. The advantages of the method are simplicity, economy and reasonable accuracy. It can be used to measure suctions from 10 to 30000 kPa. In this paper, the authors use the contact filter paper method for matric suction measurements of an unsaturated compacted silty sand (formed by the weathering of granite) which has been used as a building material for a road in the north of Portugal. The matric suctions inferred from filter paper measurements depend on the calibration between the water content of the filter paper and suction. Therefore, three calibration curves proposed at the literature (Chandler et al. 1992; ASTM D 5298; and Oliveira & Marinho 2006) for the Whatman 42 filter paper are used to interpret the measured filter paper gravimetric water contents. The results of these tests are compared to other techniques (i.e., tensiometers, and the osmotic technique) used to measure or control the negative pore water pressure in the compacted soil specimens and the results obtained are reasonably accurate.La presión capilar del suelo (es decir, la diferencia de la presión entre el aire y los componentes del agua en vacíos del suelo) es una variable llave en el análisis del comportamiento hidromecánico de suelos no saturados. Un método por lo tanto simple y económico del laboratorio para la medida de la presión capilar del suelo (también conocido como la succión matrica del suelo, la referencia que es la presión atmosférica), mesmo si un grado de aproximación está implicado, es de valor considerable. El método del papel de filtro calcula la succión indirectamente utilizando curvas de calibración. Las ventajas del método son simplicidad, economía y exactitud razonable. El método del papel de filtro se puede utilizar para medir succiones a partir del 10 al 30000 kPa. En este artículo, los autores utilizan el método del papel de filtro para la medida de la succión matric de una arena limosa compactada no saturada (formada por la meteorización del granito) que se ha utilizado como material de construcción para un camino en el norte de Portugal. Las succiones matric deducidas de medidas del papel de filtro dependen de una calibración entre el humedade del papel de filtro y la succión. Por lo tanto, tres curvas de calibración propuestas en la literatura (Chandler et al. 1992; ASTM D 5298; y Oliveira & Marinho 2006) para el papel de filtro de Whatman 42 se utilizan para interpretar lãs humedades gravimétricas medidas del papel de filtro. Los resultados de los ensayos se comparan a otras técnicas (es decir, tensiómetros, y la técnica osmótica) usadas para medir o controlar la presión negativa en lãs muestras compactadas del suelo y los resultados obtenidos sea razonablemente exacto

Efeito da calibração do papel filtro na curva de retenção de um solo arenoso siltoso compactado

The soil suction is a key variable in the analysis of the hydro-mechanical behavior of unsaturated soils. The filter paper method (FPM) calculates soil suction indirectly by measuring the gravimetric water content of the filter paper at equilibrium that is related to soil suction through a predetermined calibration curve. The matric suctions inferred from FPM depend on the calibration between the water content of the filter paper and suction. Therefore, some published calibration curves (Fawcett and Collis-George 1967; Hamblin 1981; Chandler and Gutierrez 1986; Chandler et al. 1992; ASTM D-5298 1992; and Oliveira and Marinho 2006) for the Whatman 42 filter paper are used to interpret the suction measurements of an unsaturated compacted silty sand. Experimental errors induced by using an inadequate calibration curve are discussed. The test results compared to other techniques used to measure or control suctions in the compacted soil specimens are reasonably accurate.A sucção de um solo é uma variável essencial na análise do comportamento de solos não saturados, e é necessário e importante o desenvolvimento de técnicas, diretas e indiretas, de determinação da pressão capilar de solos, que tentam aliar à simplicidade de aplicação, o que se espera ser uma precisão aceitável para os problemas reais do dia a dia da engenharia de solos. O MPF determina a sucção de forma indireta e depende da precisão em que foi determinada a curva de calibração. Várias curvas de calibração para o papel filtro Whatman 42 têm sido propostas na literatura (Fawcett and Collis-George 1967; Hamblin 1981; Chandler and Gutierrez 1986; Chandler et al. 1992; ASTM D-5298 1992; e Oliveira and Marinho 2006). Este artigo discute o uso do MPF para determinar valores de sucção de um solo arenoso siltoso compactado não saturado. Comparam-se os resultados obtidos com outras técnicas utilizadas para medir ou controlar sucções de amostras compactadas do solo arenoso siltoso e conclui-se que o MPF com adequada curva de calibração pode apresentar resultados satisfatórios.Universidade de Coimbra. Faculdade de Ciências e Tecnologia (FCT-UC)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Settlement predictions of footings on sands using probabilistic analysis

The design of footings on sands is often controlled by settlement rather than bearing capacity. Therefore, settlement predictions are essential in the design of shallow foundations. However, predicted settlements of footings are highly dependent on the chosen elastic modulus and the used method. This paper presents the use of probabilistic analysis to evaluate the variability of predicted settlements of footings on sands, focusing on the load curve (predicted settlements) characterization. Three methodologies, the first- and second-order second-moment (FOSM and SOSM), and Monte Carlo simulation (MCS), for calculating the mean and variance of the estimated settlements through Schmertmann (1970)'s equation, are presented and discussed. The soil beneath the footing is treated as an uncorrelated layered material, so the total settlement and variance are found by adding up the increments of the layers. The deformability modulus (ESi) is considered as the only independent random variable. As an example of application, a hypothetical case of a typical subsoil in the state of Espirito Santo, southeast of Brazil, is evaluated. The results indicate that there is a significant similarity between the SOSM and MCS methods, while the FOSM method underestimates the results due to the non-consideration of the high-order terms in Taylor's series. The contribution of the knowledge of the uncertainties in settlement prediction can provide a safer design

Proposals of SPT-CPT and DPL-CPT correlations for sandy soils in Brazil

Field tests in geotechnical engineering are fundamental for identification of the underground conditions. The standard penetration test (SPT) is the most commonly used geotechnical approach. There has been an increase both in the use and application of the in situ tests: cone penetration test (CPT) and dynamic probing (DP). Several empirical SPT-CPT and dynamic probing light (DPL)-CPT correlations for sandy soils have been discussed in the literature. New SPT-CPT and DPL-CPT correlations for the sandy soils of the city of Vitoria, in the southeast of Brazil, are suggested in this paper. Statistical analyses to evaluate the quality of the data used are performed, and the suggested correlations are validated with several previous published datasets. The paper also provides some insights into SPT-CPT correlations and soil characteristics (i.e. the mean particle size and the fines fraction of the soil)

ANÁLISE DE IMAGENS NA DETERMINAÇÃO DA FORMA E TEXTURA DE AREIAS

A forma dos grãos tem importante papel na avaliação da distribuição granulométrica das partículas de um solo. Entretanto, a maioria das técnicas de peneiramento evidencia que os grãos são esféricos e descritos por um único parâmetro, o diâmetro. Este trabalho teve por objetivo estudar a aplicação da análise de imagens, aliada ao grau de esfericidade e à teoria dos fractais, como ferramenta para mensurar parâmetros de forma e textura superficial de duas areias de características supostamente distintas da região da Grande Vitória, Espírito Santo, Brasil. Os resultados dos parâmetros de forma e textura superficial das amostras são apresentados e discutidos. As análises dos resultados para a variável esfericidade mostram diferenças estatísticas significativas entre as duas areias de origens diferentes. A areia de jazida de cordão litorâneo (AJ) apresentou grau de esfericidade ligeiramente superior e textura superficial mais lisa do que a de rio (AR), indicando que as areias AJ sofreram maior intemperismo em razão do transporte

Evaluation of empirical methods for estimating potential evaporation values in northeast France

This study presents and discusses the field monitoring of an experimental embankment divided into two symmetrical sections constructed with two different fine-grained soils in the northeast of France. The field instrumentation included detailed monitoring of volumetric water content, matric suction and temperature within the embankment as well as measurements of meteorological data. The field measurements show that the used instrumentation worked well on monitoring the soil responses to the meteorological changes in the two soils. The study also evaluates different empirical methods for estimating potential evaporation (ET) values based on regional meteorological data. The results show a large variability observed on the ET values for the investigated site calculated by empirical methods or equations based on meteorological local date

Évaluation del’étalonnage du papier filtre pour la détermination indirecte de la succion d'un sable silteux compacté non saturé

The soil suction is a key variable in the analysis of the hydro-mechanical behavior of unsaturated soils. The filter paper method (FPM) calculates soil suction indirectly by measuring the gravimetric water content of the filter paper at equilibrium that is related to soil suction through a predetermined calibration curve between the water content of the filter paper and suction. This paper evaluates the use of six published calibration functions for the Whatman 42 filter paper for indirect determination of soil suctions of an unsaturated compacted silty sand. Evaluation of the filter paper calibrations was carried out using the experimental results given by Fleureau et al. (2002) obtained with other techniques used to measure or control the soil suctions in the compacted silty sand. The results show that the matric suctions inferred from FPM depend on the used calibration function. A modified calibration function is suggested, which gives better estimation of the soil water retention curve for the investigated soil. The FPM offers a promising simple technique for the determination of soil suction, provided that an adequate calibration function is used for the investigated soil saturation range.La succion du sol est une variable importante dans l'analyse du comportement hydromécanique des sols non saturés. La méthode du papier filtre (FPM) permet d’évaluer la succion du sol indirectement en mesurant la teneur en eau massique du papier filtre à l'équilibre, qui est liée à la succion de sol par une courbe d'étalonnage prédéterminée entre la teneur en eau du papier filtre et la succion. Cet article évalue l'utilisation de six fonctions de calibrage pour le papier filtre Whatman 42 pour la détermination indirecte de la succion d'un sable silteux compacté non saturé. L'évaluation de l’étalonnage du papier filtre a été effectuée en utilisant les résultats expérimentaux donnés par Fleureau et al. (2002), obtenus avec d'autres techniques employées pour mesurer ou contrôler la succion du sable vaseux compact. Les résultats prouvent que les succions déduites de la FPM dépendent de la fonction de calibrage utilisée. Une fonction de calibrage modifiée est proposée, qui donne une meilleure évaluation de la courbe de succion de sol. La FPM est une technique simple prometteuse pour la détermination de la succion du sol, à condition que d’utiliser une fonction d’étalonnage adaptée à la gamme de saturation du sol étudiée.CAPE