Abstract

Recycling is an important habit to avoid waste. This paper evaluates the performance of masonry mortar, elaborated by replacing natural sand with recycled fine aggregate (RFA) obtained from mortar. Five families of mixtures were prepared with different replacement proportions: 20%, 40%, 60%, and 100%. A 1:4 volumetric cement-to-aggregate ratio was used for all mixtures by experimentally adjusting the amount of water to achieve the same consistency of 175 ± 5 mm. The effects of the following procedures were analyzed: (1) the use of a deconstruction technique to collect the RFA, (2) pre-wetting of the aggregates, and (3) the use of a commercial plasticizer. Experimental results show that it is possible to use this type of recycled fine aggregate as a substitute for natural sand by up to 60% in the manufacture of masonry mortar without significantly affecting its properties.

Abstract

Currently, worldwide, many nations are paying close attention to the improvement and optimization of the usage of recycled materials in the building sector. The increase in the raw materials and the increased environmental awareness have gained considerable importance on a global scale. In road engineering, the waste material is used for the design and construction of pavements. Ecology, energy efficiency, profitability and significant reduction of the construction time are the primary drivers of this proposal. However, social and legislative aspects have prevented these types of procedures are implemented successfully in most developing countries. In this article, we analyze some of the main trends in the use of waste materials for the design and construction of pavements.

Abstract

This paper presents a revision of some of the models that have been proposed to estimate the strength of unsaturated soils. The theoretical results obtained from these models are compared with the experimental results of controlled suction triaxial tests made on silty sand. The model that resulted in the best prediction was used to determine the stability of a slope of highly compressive clay subjected to changes in its water content. It is well known that the water content of soil is directly related with suction and that suction is an independent variable of the stress state that modifies the shear strength of unsaturated soils. Therefore, when the water content of a slope is modified, the safety factor of the slope is also modified. This exercise allows drawing some important conclusions over the stability of slopes related to the safety factor.

Abstract

A number of slopes that have been stable during many years may fail when an extraordinary rain period occurs. This phenomenon involves not only the lithology, the geometric and the mechanical characteristics of the slope but also the rain-evaporation-infi ltration regime of the site. In this paper, the stability of a slope in the comunity of San Juan de Grijalva, Ostuacán, Chiapas (Mexico) that failed during an intense raining period is analyzed. The volume of this slide was over 5 millions of cubics meters of soil and it produced the obstruction of the Grijalva river. The stratigraphic and geometric properties of the slope were determined and undisturbed samples were obtained in the site to determine the mechanical properties of the material. The stability analysis considered the variation of the cohesion of the soil caused by we ing and it was possible to observe the evolution of the safety factor with the water content of the material. Through the analysis of the rain infi ltration and the stability of the slope, it has been possible to reproduce the failure process.

Abstract

Durante la época de lluvias se presentan en el estado de Tabasco (México) deslizamientos en los bordos de los ríos que atraviesan la entidad, siendo los de la zona conocida como La Manga de los más afectados. Este artículo presenta el análisis de la evolución de la estabilidad de uno de estos bordos debido a los cambios en el grado de saturación del suelo (Sr) que lo conforma. El objetivo fue determinar el Sr del suelo para el cual el bordo pasa de una condición de seguridad a una de falla. Para lograrlo, primero se realizó una campaña de exploración de campo y ensayos de laboratorio, lo que permitió obtener las características geométricas del bordo, así como las propiedades del suelo que lo constituye. De las muestras inalteradas obtenidas en campo se realizaron ensayos de compresión triaxial variando solo el grado de saturación del suelo. Con los datos obtenidos y mediante el software GeoSlope 2016 se realizaron diversos análisis de la estabilidad. Los resultados muestran que conforme el grado de saturación crece la estabilidad del bordo disminuye. Se comprobó que para el bordo en estudio sobrepasar un grado de saturación de 70 % implica una condición de peligro de deslizamiento. Por lo tanto, el monitoreo del grado de saturación del suelo que constituye a los bordos permite anticipar su falla y, en consecuencia, hace posible establecer acciones de prevención.

Abstract

Durante la ejecución de obras de ingeniería es común que el suelo que se desea utilizar no cumpla con los criterios de calidad que la normativa correspondiente exige para garantizar la estabilidad estructural de la obra. Para aquellos casos en los que el valor del índice de plasticidad del suelo excede el máximo permitido, la estabilización química ha demostrado los mejores resultados. En esta investigación se realizó un análisis comparativo del rendimiento del óxido de calcio (CaO) o cal viva, y el cloruro de sodio (NaCl) o sal de mesa, como agentes estabilizadores. Se agregaron estos agentes químicos en distintas proporciones al suelo en estudio y se monitorizaron las variaciones del límite líquido, límite plástico y el índice de plasticidad. Los resultados demostraron, contrario a lo que tradicionalmente se espera, que para el caso del suelo en estudio el mejor agente estabilizador es el cloruro de sodio o sal de mesa, debido a que no solo es más efectivo en disminuir el índice de plasticidad, sino que además es más barato que la cal.