Research Outputs
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.
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 variables.