En la práctica de la ingeniería geotécnica es común el empleo de fundaciones por pilas cargadas transversalmente en la parte superior. Frecuentemente este tipo de fundación es ejecutada en suelos de alta porosidad y colapsables, comunes en varias regiones de Brasil. Debido a la poca información disponible en la literatura, se realizaron dos pruebas de carga con cargamento transversal en una pila (diám. 0,8 m; prof. 9,0m; diám. base 1,60m). Se realizó una prueba de carga estando el suelo en su condición de humedad natural y otra después de la previa inundación. Fueron obtenidas las curvas carga x desplazamiento horizontal y los coeficientes de reacción horizontal. Los resultados permitieron verificar la aplicabilidad de fórmulas teóricas de previsión de comportamiento, así como proponer parámetros a ser utilizados para el suelo. Previo a la realización de las pruebas de carga fueron realizados ensayos de laboratorio y campo para la investigación del subsuelo.

Unsaturated surface soils with porosities above 50% cover great extensions of areas in Midwest Brazil. Because of their large volumes of voids, these soils undergo great strain under loads. In addition, many of these soils are collapsible, i.e., when the soils are under load and in case of a significant increase in the moisture content or saturation of the soil, the structure collapses, thus producing unacceptable displacement values for the buildings. Because of these characteristics, problems often occur in industrial floors, pavements and other types of slabs on ground and shallow foundations. To solve this problem, compaction of the topsoil is performed before starting the construction. For this study, the soil characteristics are analyzed using both geotechnical laboratory tests and field tests in order to predict the soil behavior in terms of deformability, resistance and collapsibility. The study was conducted at the experimental site located at the State University of Campinas-Unicamp, in the municipality of Campinas, State of São Paulo, Brazil. The geotechnical properties of the subsoil were determined by collecting undisturbed samples down to 8 m in depth and deformed samples up to 9 m of depth (impenetrable). Simple recognition surveys were performed: standard penetration test (SPT) and electric static cone penetration test (CPT). The edometric tests conducted on undisturbed samples with flooding at different levels of stress revealed collapsible characteristics of the soil. With the conduction of tri-axial tests (CU), numerical values were obtained for the angle of friction and the cohesion intercepts for each depth. Paschoalin Filho (2008) verified a significant reduction in these values with soil saturation. The influence of soil deformability and of the type of load on industrial floors is analyzed. The results indicate huge influence of soil deformability in the case of distributed loads, and a minor influence in case of concentrated loads. The thickness of the compacted soil layer is very important to the definition of the modulus of subgrade reaction (k) for the studied soil.

No abstract

Abstract. In geotechnical engineering, the problem of laterally top-loaded piles occurs frequently. This type of foundation is often used in highly porous, collapsible soils, which are common in several regions of Brazil. Because of the limited information available in the literature, several load tests have been performed on piles subjected to this load. To analyze the behavior of piles in these collapsible soils, load tests were performed in steel piles (I), W 250  32.7 section (mm  kg/m), length 12 m, conventional bored piles (/ = 0.40 m; L = 12 m) and continuous helical auger piles (/ = 0.40 m; L = 12 m). All of them were tested at the same site. For each type of pile, a first load test was carried out with the soil in its natural condition of moisture content, followed by a second load test after the surface soil was flooded for 48 h. The results indicated a significant negative effect of flooding on the topsoil which consisted of sandy-silty clay with collapsible features down to the depth of 6 m. Load vs. horizontal displacement curves and soil coefficients of horizontal reaction were obtained. The results allowed the proposal of parameters for use in the soil under study. Before executing the load tests, laboratory and in-situ tests were performed to investigate the local subsoil.

Analise de prova de carga em tubulão a céu aberto submetido a esforço horizontal em solo não saturado de diabásio da região de Campinas / Roberto Kassouf. ..