1,720,993 research outputs found
Some reflections on the use of a cooperative learning model in soil mechanics courses
No full textThe Bologna Process’ implementation enforced a significant change on the traditional learning models, focused mainly on the transmission of knowledge. The use of a cooperative learning (CL) model in the Soil Mechanics courses (undergraduate level) of the Department of Civil Engineering, University of Aveiro, Portugal, is described. The students were confronted with situations recreating professional atmosphere in Geotechnics. Mandatory team project assignments were implemented, where each student had to fulfil specific and rotational roles. All students performed the established functions (different in each project), representing the corresponding role – jigsaw. These roles had, as much as possible, a parallel to functions normally fulfilled by engineering professionals. The impact of the implemented model was assessed using students’ feedback, marks monitoring and questionnaires. These results are presented and discussed. Some additional reflections on the impact of the CL system on the teacher’s work are also included.
Sand reinforced with recycled cotton textiles from waste blue-jeans: stress–strain response
No full textThe resilience and sustainability of infrastructure can be increased by reducing quantities of natural materials used in construction and/or relax the requirements for their properties. To foster sustainable solutions and circular economy, the potential of using wastes and by-products from different industries as reinforcements should be explored. Herein the stress–strain response of a sand reinforced with waste cotton textile from blue-Jeans was studied using conventional triaxial tests. The responses observed were compared to the unreinforced soil and analysed using a critical state framework. The reinforcements were cut from waste cotton blue-Jeans, without any treatment, in three forms: horizontal discs, and discrete fibres with two different dimensions. The waste cotton textile from blue-Jeans performed well as reinforcement elements within sand. In general, the different forms of reinforcement studied (horizontal disc and fibres) placed at mid-height of the triaxial test specimens were able to improve the stress–strain response of the reinforced soil, relative to the unreinforced soil. The reinforcements increased the ductility of the stress–strain response, increased the strength parameters (for both peak and large strain responses), and increased the critical state parameters. The different forms of reinforcement are mobilised differently. For the loading conditions of the conventional compression triaxial tests, the horizontal disc of reinforcement was the most effective.</p
Synergisms between laboratory mechanical and abrasion damage on mechanical and hydraulic properties of geosynthetics
Full text linkThis paper analyses the existence of synergisms between some endurance durability agents of geosynthetics – mechanical damage (usually associated with installation) and abrasion damage (often associated with cyclic actions, for example due to contact with ballast). Three geosynthetics (geotextile, geogrid and geocomposite) were submitted to mechanical damage and abrasion damage using index laboratory tests. The geosynthetics were exposed first individually to each agent (single exposure) and then sequentially to the two agents (multiple exposures). To ensure the results were statistical representative, each set of tests was performed three times. The consequences of the damage induced were visible (naked eye). Abrasion damage was found the most critical damage mechanism for the tensile properties, particularly for the geogrid and geocomposite tested. The connections between their components created potential fragility points in the abrasion test. Due to its structure, combined with high mass per unit area and thickness, the geotextile tested survived well the damage induced. A positive synergy between the mechanical and the abrasion damage induced was found for the tensile properties of the geosynthetics most affected by damage, more important for their tensile strength than for their secant stiffness. The mechanical damage was the most critical mechanism for the permittivity of the geotextile and the geocomposite, likely due to clogging of their pores. For the permittivity and the characteristic opening size of these geosynthetics, negative synergy between mechanical and abrasion damage was found; the traditional approach was found likely to result in unsafe estimates of these properties
An equipment to perform damage during installation tests of geosynthetics
No full textThe equipment developed to carry out damage during installation tests in laboratory on geosynthetics is described. These tests allow inducing in laboratory the effects of the procedures of installation on site on the geosynthetics. The test equipment and test procedures are described and the characteristics of the granular material and the geosynthetic used in this study are referred. After carrying out the damage during installation laboratory tests, intact and damaged samples of geosynthetic were: 1) observed using scanning electronic microscope; and 2) carried out tensile tests in order to characterise the damaged induced
Synergy between mechanical damage and abrasion of a composite geosynthetic and its variability
No full textIn this paper results of tests to assess the effect of mechanical damage (generally associated with installation processes) and abrasion are presented. Laboratory tests were carried out. The material tested is a composite consisting of two overlapped geosynthetics: a nonwoven geotextile and a woven geogrid. The composite was submitted to each referred agent (mechanical damage and abrasion damage) in isolation and sequentially, in order to assess an eventual synergetic effect. The effect of the damage induced in the short-term mechanical properties of the geosynthetic was assessed. The variability of these properties was assessed by using either 1 or 3 tests per sample. Abrasion damage (either isolated or combined with mechanical damage) was the most critical mechanism, leading to higher reductions of tensile strength. Increasing the number of tests used to characterise the samples from 1 to 3, has reduced the variability of the properties assessed, although the tensile strength values decreased and the peak strain and secant stiffness modulus for 2% strain increased. The number of characterisation tests carried out per sample didn’t affect the trends observed associated with the damage induced. Some synergisms were observed for mechanical and abrasion damag
Numerical tool for the design of granular and geotextile filters
No full textTraditionally granular filters were used. In the last decades they have been progressively replaced by geotextile filters. For their design there are several methods available in the literature, however, as many of them result from the experience with implementation of geotextile filters under specific conditions, their application should be done with care. A numerical tool was developed to assist in the designing of filters, for both granular and geotextile solutions. This tool includes a list of methods useful for the designer of a filter, and thus, was developed to give the user information about the validity of the conditions for applying the methods in question. It includes a comparison and summary of the design results obtained from different methods, allowing their comparison. The numerical tool has been tested and validated using examples from literature and is working well and can be a good aid for the project of filters, therefore, a valid approach to save time and additional expenses
Hydraulic properties of a geosynthetic composite after mechanical damage and abrasion and their variability
No full textIn this paper results of tests to assess the effect of mechanical damage (generally associated with installation processes) and abrasion are presented. Laboratory tests were carried out. The material tested is a composite consisting of two overlapped geosynthetics: a nonwoven geotextile and a woven geogrid. The composite was submitted to each referred agent (mechanical damage and abrasion) in isolation and sequentially, in order to assess an eventual synergetic effect. The effect of the damage induced in some physical and hydraulic properties of geosynthetics was assessed: characteristic opening size and permittivity. The variability of these properties was assessed by using either 1 or 3 tests per sample. The results indicate that the number of tests carried out leads to different conclusions, pointing out the need of adjusting the number of specimens to be tested. The mechanical damage seems to result in a significant clogging of the geocomposite’s pores, while the abrasion damage resulted in decreased constrictions to the flow of water. Some synergisms were observed for mechanical and abrasion damage
Project-based learning in Geotechnics: cooperative versus collaborative teamwork
No full textSince 2007/2008 project-based learning models have been used to deliver two fundamental courses on Geotechnics in University of Aveiro, Portugal. These models have evolved and have encompassed either cooperative or collaborative teamwork. Using data collected in five editions of each course (Soil Mechanics I and Soil Mechanics II), the different characteristics of the models using cooperative or collaborative teamwork are pointed out and analysed, namely in terms of the students’ perceptions. The data collected include informal feedback from students, monitoring of their marks and academic performance, and answers to two sets of questionnaires: developed for these courses, and institutional. The data indicate students have good opinion of the project-based learning model, though collaborative teamwork is the best rated. The overall efficacy of the models was analysed (sum of their effectiveness, efficiency and attractiveness). The collaborative model was found more adequat
Project-based learning in consecutive modules on geotechnics: foundations
No full textThree conditions of effective learning have been reported: active learning by doing, cooperation and teamwork in learning and learning through problem solving, essential to promote creativity and innovative capacity. Project-based learning can help to promote such skills in engineering programs as it allows recreating professional reality and relating fundamental theories and skills of an engineer. High-level thinking and sound judgment is developed through accumulated authentic professional experience by engineers. For engineering students a similar process can be triggered by a teaching environment which enables simulating and stimulating such skills. To prepare better professional and enhance students' employability Civil Engineering students of University of Aveiro, Portugal, have undertaken several modules on Geotechnics where a project based learning model has been used. These group projects included open-ended realistic scenarios tackled using different tools (spread-sheets and software). This paper refers to a module on Foundations. A collaborative project-based learning model was implemented. Students' perceptions on the added value of the project were collected using a questionnaire and are discussed. Most students had attended two modules on Soil Mechanics where a similar learning model was used, but initially they had negative reactions to it. Students report a severe workload; however their estimates match the expected working hours. The model has been evolving in order to optimise the learning and address the students’ feedback
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