This paper reports the results of pullout tests on five different geosynthetics embedded in two different granular soils. Soil and geosynthetic properties are described and soil-geosynthetic interaction behaviour is studied. Based on the results of pullout tests, the influence of soil particle size, geosynthetic structure, and the role of geogrid bearing members are discussed. The main conclusion is that the influence of soil particle size on soil-geosynthetic interaction is important, but its significance depends on several factors. With geogrids, the relative sizes of soil particles and geogrid apertures, and the thickness of the geogrid bearing members, determine soil-geogrid interface shear resistance. A marked increase in soil-geogrid interface shear resistance was observed when the soil contained a significant percentage of particles with sizes slightly greater than the thickness of the geogrid bearing members, but smaller than the geogrid apertures. Tests, on geogrids in which the bearing members had been cut, show a significant decrease in soil-geogrid interface shear resistance. The influence of soil particle size is less important for geotextiles and geocomposites. Although the structure of geotextiles and geocomposites has an effect on soil-reinforcement interface behaviour, mobilised pullout resistance is also affected by the axial tensile stiffness of geotextiles and geocomposites.

This paper reports the investigation of the shear behaviour of six geosynthetics with two granular soils. The test equipment, soils, and geosynthetics properties are described and the soil-geosynthetic interaction behaviour is studied. The influence of soil particle size, geosynthetic structure, and test method are discussed by analysing the results of inclined plane tests. The main conclusions of the study are as follows: geosynthetic structure has an important influence on the soil-geosynthetic interface friction angle; higher soil-geosynthetic interface friction angles are measured when the geosynthetic surface has significantly sized apertures (e.g., geogrids) or allows the penetration of soil particles into the geosynthetic (e.g., nonwoven, spun-bonded geotextiles); geosynthetic surface roughness (e.g., geomembranes) is associated with higher soil-geosynthetic interface friction angles; soil particle size has an important influence on the soil-geosynthetic interface friction angle; broadly graded soils with large average soil particle sizes allow an increase in the soil-geosynthetic interface resistance; the method of test does not significantly influence the soil-geomembrane or soil-geotextile interface friction angles (geosynthetics with continuous surfaces); and the validity of evaluating the soil-geogrid interface resistance using a rigid support (Test method 1) depends on the structure of the geogrid. It is suggested that site conditions is the greatest factor to consider when selecting the most appropriate test method.

In this paper, data from field installation trials of geosynthetics and laboratory tests are presented and analysed. The influence of several factors was assessed, namely nominal strength and type of geosynthetic, soil, compaction energy and method used to induce installation damage. Visual observations using a scanning electron microscope were performed. From the data collected, reduction factors for installation damage were derived using tensile strength values (traditional approach) and stiffness modulus (for 2% strain). Relative to the stiffness approach, the results obtained indicate that the traditional approach can be conservative. The reduction factors, determined using the traditional approach, were also compared with interval estimates from the literature. To contribute to supporting a shift from a factor of safety approach to a limit state design, bias statistics to correct the deterministic predictions were determined from the results. Different correlations were also established to enable using these results to interpolate reduction factors for similar installation conditions and/or geosynthetics from the same family of products. Installation damage reduction factors should be used in limit state design (ultimate and serviceability). Nevertheless, the stiffness approach can only be used for limit states where tensile failure of the geosynthetics will not occur.

In todayâ??s society engineer professionals play a crucial role in tackling challenges such as climate change or economic constraints, in order to promote economical development and increase of quality of life ensuring principles like sustainability or safety. It is fundamental to prepare the future engineers to these and future challenges. According to the literature, traditional engineering educational strategies used to prepare the future engineers (lectures, lab experiences and homework) have two main drawbacks. Firstly, they inadequately prepare engineering students to engage in collaborative partnerships (essential for the practicing engineer) and, secondly, they promote passive learning and contribute to a compartmentalized curriculum. As such, the traditional deductive learning may not adequately prepare students for their innovative and flexible role as future engineers. An alternative approach is the use of non-traditional learning strategies, as in the case study hereby presented. Active learning strategies, namely project-based learning, were used to contribute to enhancing problem solving and higher order thinking skills of the graduates in Civil Engineering program of University of Aveiro, Portugal. Seizing the opportunity created by the Bologna process, two complementary courses on Geotechnical subjects (Soil Mechanics I and II) have been redesigned. The non-traditional strategies implemented include project-based learning using cooperative and collaborative models, put into practice since 2007/2008. The learning strategies referred are described and discussed. Their contribution to the development of problem solving and high order thinking skills of students is pointed out. Several strategies used to promote acceptance by students are put forward. The models were assessed using three strategies: studentsâ?? feedback during the semester; academic performance; questionnaires at the end of the semester. The evolution of the studentsâ?? response to these models is discussed using data collected in the courses. The models have been adapted to overcome some of the difficulties faced during their implementation.

This paper contributes to understanding how installation damage of geosynthetics influences their long-term response and design. A geotextile and a geogrid were exhumed after installation under real conditions; their long-term tensile behaviour was investigated using conventional creep and creep rupture tests. Reduction factors for installation damage, creep and their combined effect were computed. The main aim of the paper was to assess how the long-term response of the geosynthetics was influenced by installation damage and whether it would be necessary to update current design approaches. The installation damage affected the mechanical response of both geosynthetics; important strength reductions were observed, particularly for the most severe installation conditions. The results indicate that, contrary to what has been reported in the literature, the creep rupture response of the geotextile changed after installation damage. When tested under similar creep loads (fraction of the sample tensile strength), both geosynthetics exhibited reduced potential for creep rupture and smaller strains at the end of primary creep. Changes in stiffness were less important than those for strength, for both short- and long-term response. There was synergy between installation damage and creep; the traditional approach to design was unsafe for the geotextile and slightly conservative for the geogrid.

Installation damage of geosynthetics occurs during their handling, positioning on the ground and the placing and compacting of fill material. Abrasion is a common damage mechanism where there is cyclic relative motion (friction) between a geosynthetic and contact soil. This paper presents the laboratory test results of mechanical damage and abrasion performed on six geosynthetics. The in isolation and combined effects on mechanical, hydraulic and physical properties of the geosynthetics were assessed. Results show that the effects of induced mechanical and abrasion damage essentially depend on the geosynthetic structure. For the most affected materials, strength losses after abrasion (in isolation and combined with mechanical damage) are higher than after the induced mechanical damage. Therefore, for most geosynthetics studied, abrasion is the conditioning mechanism which most affects their tensile strength. An increase of the characteristic opening size of the geosynthetics was observed, while their permittivity did not increase. This may be caused by differences in the test set-ups.