Biopolymer Geogrids for Geotechnics

This study focused on the mechanical characterisation of 3D printed biopolymer geogrids for civil and geotechnical engineering applications. The polylactic acid specimens were designed based on first-order similitude conditions and were produced by fused deposition modelling techniques. An experimental programme was carried out to investigate the mechanical behaviour of 1:2 scale model geogrids undergoing tensile loading conditions, in order to explore their use in soil reinforcement and stabilisation of geomaterials. The secant stiffness at 2.0% of strain and the ultimate tensile strength were used for this purpose. The results showed an average tensile strength of 4.5 ± 0.5 kN/m, which is in good agreement with that of fossil oil-derived polymer prototypes, while presenting a significantly lower elongation at failure. The printing process appeared stable and replicable. The influence of degradation on the tensile properties of 3D printed polylactic acid geogrids over time still needs to be studied. Keywords: geogrid, additive manufacturing, biopolymer, tensile strength, geotechnic

Stress-strain Relationship in Homogeneous and Two-layered Triaxial Test Specimens

The stress-strain relationship of a homogeneous specimen, obtained from triaxial compression test, allows to determine stiffness parameters for numerical-method based analyses in common geotechnical software. Stiffness parameters are defined as the ratio of stress to strain along an axis. However, when a heterogeneous specimen is tested, the equivalent elastic modulus that represents a simplification of the nonlinear behavior is complex. This paper presents a study intended to contribute to the debate about the degree to which conventional soil mechanics approaches can be applied to layered specimens. Triaxial compression tests were carried out on both homogeneous and two-layered specimens under a low effective confining pressure of 30 kPa. The triaxial apparatus was chosen since the applied stress and specimen boundary conditions are well defined, and the repeatability of the test method is good. The behavior of both specimens was studied in terms of the stress-strain relationship and stiffness. The main differences were crucial to understanding the composite soil-aggregate interaction, which is discussed and compared. The results indicate that the interface between composite soil and aggregate is important to keep the stability of the layer of aggregate over the soft composite soil, and practical methods of achieving that are suggested

Exploring irrigation and water supply technologies for smallholder farmers in the Mediterranean region

Water security is a hot topic all over the world, due to global warming, climate change, natural calamities such as droughts and floods, overuse of water, and other factors. Water issues have been scientifically investigated from several perspectives, namely institutional, economic, social, environmental, managerial, and technological. However, the technological aspects of irrigation and water supply for smallholder farmers in the Mediterranean region have not been adequately addressed. This paper explores irrigation and water supply technologies for smallholder farmers in the selected Mediterranean countries (Egypt, Malta, Morocco, and Portugal). The methods of analysis are literature review, fieldwork, and observation. The literature survey reveals that Mediterranean countries share many common features in terms of climate, water and land resources, and development issues. Nevertheless, the selected countries in the Mediterranean region (Egypt, Malta, Morocco, and Portugal) differ in terms of type of crops, water management regulations, labor force availability, financial sustainability, and economic approaches. These remarks signal the need for applying a specific approach in selecting a technology for irrigation and water supply according to the regional context. Additionally, the financial and economic perspectives of the three key technologies (i.e., SLECI, desalination technology, and engineering constructed wetlands) require further analysis.This research carried out within the project MED-WET “Improving MEDiterranean irrigation and Water supply for smallholder farmers by providing Efficient, low-cost and nature-based Technologies and practices” (Project ID 1646) funded by Partnership for Research and Innovation in the Mediterranean Area (PRIMA) program.info:eu-repo/semantics/publishedVersio

Comportamento do solo microreforçado com fibras sinteticas de pequeno comprimento

Dissertação de Mestrado em Engenharia Civil, Especialidade em Mecânica dos Solos e Engenharia Geotécnica, apresentada à Faculdade de Ciências e Tecnologia da Universidade de Coimbr

The Cohesion or Dilation Effect on the Shear Strength of Granitic Residual Soil

The paper reports laboratory investigations carried out in granitic residual soil from Covilha, to evaluate the stress-strain-dilatancy behaviour to provide a new model. Some soil tests are intended only to classify soil into broad groups. Other tests are done to examine the mechanical behaviour of soils and particularly to investigate their strength and deformation during loading. Drained and undrained triaxial tests were performed to study soil fabric effects on the mechanical behaviour of a granitic residual soil. It was revealed that the dilatancy of the saturated soil contributes to shear stress and strength at lower confining pressures. The cohesion is apparent for small stress and we need to introduce the evaluation of volumetric strain to understand the effect of the dilatancy in the peak strength