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.
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).
Quantifying Geotourism: A demoscopic study for the “Litoral del Biobío” Geopark project (Chile)
Geotourism as a tool for local and social development requires evaluating how geology is perceived by society and how the geology can contribute to solve society’s needs and perspectives. This research is the result of a survey undertaken in the “Litoral del Biobío” geopark project (Chile) from April to September 2019. This survey consists of over 400 people and is a direct geoturistic demoscopic study on local communities. It covers a large diversity of social setting (ranging from urban to rural indigenous) and also a diverse level of education. Salient points of the results includes more than 80% of the community are aware of the sites of tourist interest in their community, while less than 20% recognize the geology and/or geosites of the territory. The need for economic development (21%) and tourism in natural areas (82.5%) stand out as the main tourism focus and tool for generating sustainable economic resources for the territory. Geodiversity and geotourism play an important role (48.1%), but are subordinate to biodiversity (76.7%) in the territory. Furthermore, geotourism is far from the perceptions of crime (23%), given that it is still a minority tourism sector. Finally, there is a certain level of resignation in the community regarding the medium-term development of its territory (52%), with education on geological and environmental risks (77%) being one of the main priorities. This study shows that, although there are basic needs to be covered in the territory, such as security and public infrastructure, there is also a great interest in developing tourism in natural areas. In this scenario, geotourism becomes relevant as a tool that can contribute to local sustainable economic development, education on geological risks, awareness of the geological value of the territory, as well as the revaluation of the cultural heritage in the study area.
An open-source system for generating and computer grading traditional non-coding assignments
One of the most time-consuming activities in higher education is reviewing and grading student evaluations. Rapid and effective feedback of evaluations, along with an appropriate assessment strategy, can significantly improve students’ performance. Furthermore, academic dishonesty is a major issue in higher education that has been aggravated by the limitations derived from the COVID-19 pandemic. One of the possible ways to mitigate this issue is to give different evaluations to each student, with the negative cost of increasing reviewing time. In this work, an open-source system developed in Python to automatically create and correct evaluations is presented. Using Jupyter Notebook as the graphical user interface, the system allows the creation of individual student question sheets, with the same structure and different parameter values, to send them to students, grade them, and send the final score back to the students. The proposed system requires little programming knowledge for the instructors to use it. The system was applied in Civil Engineering and Geological Engineering programs at the Universidad Católica de la Santísima Concepción, drastically reducing grading time while improving students’ performance.
The effect of weathering on the variation of geotechnical properties of a granitic rock from Chile
The effect of rock weathering on geotechnical parameters can become substantial in geotechnical design. The weathering degree (WD) has usually been divided into five levels from fresh rock to completely weathered rock. In this study, the above five WDs are adopted to analyse the variation of several regularly used geotechnical properties. To that aim, a series of laboratory tests on a Chilean granitic rock in different stages of weathering was carried out. The results of the tests have been analysed by normalizing each geotechnical parameter with respect to the value obtained for slightly weathered samples instead of for fresh rock samples as is usually adopted. In this way, it was found that the unconfined compressive strength reduces steadily and considerably with each WD, as has been previously reported. Conversely, the modulus of deformation and P-wave velocity tend to stabilize the rate of reduction for highly and completely weathered rock samples, which does not agree with the trend and higher rate reductions found by other researchers. This stabilization reduction rate with WD was also found for compaction density, friction angle and Poisson's ratio.