Laboratory Assessment of Water Permeability Loss of Geotextiles Due to Their Installation in Pervious Pavements

During the last decades, the importance of sustainable development in society has increased considerably. Sustainable Urban Drainage Systems (SUDS) are a group of techniques that aim to improve the management of rain and run-off water while reducing their pollution. Many of these systems incorporate geotextiles in their structures, which act as a layer separation and water filter. Some authors defend the idea that by simply being installed, geotextiles partially or totally lose their separation and filtering capacities. This study proposes a testing methodology that can reproduce this effect and obtain a reduction factor for the water permeability of the material after its installation, which is defined here as the ?new condition factor?. The procedure simulated the real installation conditions in the laboratory by causing the specimen to undergo both mechanical and hydraulic damage and subsequently measuring the loss of water permeability that it provoked on the geotextile. Two different nonwoven geotextiles were tested in order to validate the procedure and to obtain initial results that could confirm the need for the new condition factor in the design of pervious pavements with geotextiles. Analysis of variance (ANOVA) was used to determine the statistical significance of the test variableshis research was funded by the Spanish Ministry of Economy and Competitiveness, grant number BIA2012-32463, and by the Dirección de Investigación of the Universidad Católica de la Santísima Concepción, fund FAA 02/2018. The authors would like to thank the support and collaboration from the Construction Technology Research Group (Grupo de Investigación de Tecnología de la Construcción - GITECO), the Geosynthetics Laboratory of the University of Cantabria (LAGUC), Grupo de Caminos de Santander (GCS) and the Geotechnical Group of the University of Cantabria

Experimental characterization of the shear strength of raw (MSW) and pre-treated (MBT-MSW) municipal solid waste landfills

RESUMEN: Con el objetivo de obtener de forma sencilla y económica las características mecánicas de la masa de residuo en un vertedero, se ha realizado una campaña de ensayos de campo utilizando pruebas presiométricas y de penetración estática. Esto ha permitido la obtención de los valores de los parámetros resistentes y deformacionales de los vertederos estudiados. En los últimos años, se han introducido los Tratamientos Mecánicos y Biológicos (M.B.T.) en la gestión de residuos. Los objetivos fundamentales de estos son la disminución de la actividad de la materia orgánica en los materiales depositados en el vertedero, así como la reducción de la masa y volumen de residuos vertidos. Actualmente no es suficientemente conocido el efecto que estos tratamientos tienen en la resistencia, por lo que se ha realizado un estudio mediante ensayos de laboratorio de los materiales generados en la planta de tratamiento del vertedero de Meruelo (Cantabria). Para el estudio se han realizado ensayos de corte directo sobre probetas de base cuadrada de 300 mm de lado y ensayos de compresión triaxial consolidados drenados sobre probetas de 100 mm de diámetro. La campaña ha permitido obtener las características mecánicas de los dos materiales generados en la planta, así como de muestras con proporciones variables de los mismos. Por último, se ha realizado el análisis retrospectivo de un accidente real (Back-analysis) ocurrido en un vertedero de R.S.U. sin tratar, lo que ha permitido determinar las posibles causas y las características resistentes de los residuos involucrados.ABSTRACT: With the aim of characterizing in a simple and economic way the waste disposed in a landfill, a field campaign, using pressuremeter and cone penetration test, was undertaken to determine the shear strength and the stiffness of the studied landfills. In the last years, Mechanical and Biological Treatments (MBT) have been introduced in waste management. The main purposes of these treatments are to decrease the activity of the organic matter within the waste mass and to reduce the weight and volume of the landfilled waste, but it is not clear how these treatments affect the shear strength of the residues. The materials generated in the Meruelo’s landfill treatment facilities have been studied in the laboratory using large scale Direct Shear (300 x 300 m) and large scale Triaxial (Ø100 m) tests. As the materials generated are disposed together, several mixtures with variable proportions of each of them have also been studied. Finally, the accident occurred in a real non-treated MSW sanitary landfill has been studied. The possible causes of the accident along with the shear strength of the involved wastes have been determined.Esta tesis doctoral ha sido financiada por las siguientes instituciones: Proyecto de investigación “Estudio para el establecimiento de la metodología y las condiciones más adecuadas en la realización de ensayos de caracterización geotécnica de residuos en depósitos controlados” financiado por Ferrovial Servicios S.A. Proyecto de investigación del Plan Nacional de I+D+i “Propiedades mecánicas de los residuos sólidos urbanos (R.S.U.) para el diseño y explotación de vertederos” (Ref. BIA2012-34956). Otorgado al Grupo de Geotecnia de la Universidad de Cantabria por el Ministerio de Economía y Competitividad. Ayuda predoctoral para la Formación de Profesorado Universitario (F.P.U.) (Ref. FPU12/05530) concedida por el Ministerio de Educación, Cultura y Deporte dentro del Programa Nacional de Formación de Recursos Humanos de Investigación. Beca predoctoral concedida por la Universidad de Cantabria dentro del Programa de Personal Investigador en Formación predoctoral del año 2012 Ayuda de movilidad para estancia breve concedida por el Banco Santander a través de Santander Universidades dentro del programa Becas Iberoamérica. Santander Investigación 2016/2017

Shear strength characterization of fresh MBT and MSWI wastes from a Spanish treatment facility

ABSTRACT: A laboratory shear strength characterization of the landfilled materials of the Municipal Solid Waste integral treatment plant from the Meruelo Environmental Complex in Cantabria (Spain) was performed. The materials tested come from the rejection of the Mechanical and Biological Treatment (MBT-MSW) and the slags produced in the energy recovery plant (MSWI). Laboratory characterization consisted of direct shear and consolidated drained triaxial testing. Mohr-Coulomb failure criterion parameter values were obtained and compared to reported values in the literature. In some tests, failure was not reached due to the reinforcement effect for fibrous particles; thus, the mobilized shear strength parameters for different values of axial strain were obtained. The triaxial test results showed strain-hardening in MSW-MBT but not in MSWI. Failure was reached on both materials in direct shear testing, with MSWI showing peak and ultimate strengths, whereas MBT-MSW exhibited only ultimate strength. Direct shear test obtained strength can be characterized by a cohesion of 20 kPa and a friction angle of 33% for MBT-MSW ultimate strength, while cohesion and friction angle varies from 13.4 to 29 kPa and from 38.5º to 42.3º for MSWI ultimate and peak strength, respectively. The mobilized cohesion and friction angle obtained for MBT-MSW in consolidated drained triaxial tests ranged from 15.1 to 62.7 kPa and 20º to 28.7º, corresponding to a strain level of 5% and 25%, respectively. In triaxial testing of MSWI specimens, failure was reached, and the material showed a cohesion of 51.3 kPa and a friction angle of 32.8%.This work was supported by the Spanish Ministry of Economy and Competitiveness [grant number BIA2012-34956]; the Spanish Ministry of Education, Culture and Sports [grant number FPU12/05530]; and the Dirección de Investigación of the Universidad Católica de la Santísima Concepción [grant number INIDIN 07/2019]. The authors would also like to thank Tircantabria S.L.U. for their support during the investigation, especially on sampling

Experimental Investigation on the Influence of Oven-Drying on the Geotechnical Properties of Volcanic Ash-Derived Residual Soils

For thousands of years, the volcanic activity present along the Andes Mountain range has generated a large amount of pyroclastic material. As a result, around 60 percent of the soils present in Chile have a volcanic origin, of which, we can find soils derived from volcanic ash. These correspond to soils whose origin is the weathering of volcanic ash, which generates minerals such as allophane, imogolite, and halloysite. The presence of these minerals gives these soils unique geotechnical properties, such as high plasticity, low dry unit weight, and a unique internal structure. Subjecting these soils to extreme temperatures like those needed to perform standard laboratory tests produces changes in their structures, and thus in their geotechnical behavior. These changes are important to be aware of with respect to slope stability problems, embankment conformation, surface foundations, etc. In the present study, a type of soil found in Chile originating from the weathering of volcanic ash and locally named Trumao was studied. Due to its age and formation processes, the main minerals found in the soil are allophane and imogolite, and hence it belongs to the allophanic soil type. The material was studied in its natural state (undisturbed) and, after being oven-dried using common geotechnical tests, the behaviors of both samples were compared. The study shows that some properties are affected significantly by the oven-drying process, and thus it is not recommended to expose the material to high temperatures during geotechnical laboratory testing to avoid misleading results

Analysis of the Influence of Geomechanical Parameters and Geometry on Slope Stability in Granitic Residual Soils

Granitic residual soils are soils formed by the in situ weathering of intrusive granitic rocks and are present in different parts of the world. Due to their large presence, many civil engineering projects are carried out on and within these soils. Therefore, a correct characterization of the slopes is necessary for slope stability studies. This investigation aims to study the influence of the values of geomechanical parameters (specific weight, cohesion, and friction angle) and the geometry of a slope (height and inclination) on slope stability of residual granitic soils in dry and static conditions. To this end, an automatic system was developed for the numerical study of cases using the finite element method with limit analysis. The system allows modeling, through Monte Carlo simulation and different slope configurations. With this system, the safety factors of 5000 cases were obtained. The results of the models were processed through the SAFE toolbox, performing a Regional Sensitivity Analysis (RSA). The results of this research concluded that the order of influence of the factors were: slope angle > slope height > cohesion > friction angle > unit weight (β > H > c > ϕ > γ)