Castorina Silva Vieira

Soil–geosynthetic inclined plane shear behavior: influence of soil moisture content and geosynthetic type

Abstract This paper deals with the inclined plane shear on three different geosynthetics (a geocomposite (GC), a non-woven geotextile (GTX), and an extruded geogrid (GGR)) with a residual soil from granite. Soil and geosynthetic properties, test equipment, and procedures are described. The influence of soil moisture content and geosynthetic type on soil–geosynthetic interaction behavior is discussed by analyzing the results of the inclined plane shear tests. The main conclusions that can be outlined from the present study are the following: (1) the influence of soil moisture content was relevant for the soil–GTX and soil–GC interfaces. Indeed, the resistance of those interfaces decreased with the increase of soil moisture content. No significant differences were observed between the behavior of those geosynthetics; (2) the influence of soil moisture content on the behavior of the soil–GGR interface was less evident. A slight decrease on the interface friction angle was only observed for the highest soil moisture content; (3) the dry soil–GGR interface resistance was lower than that observed for the other two geosynthetics due to the relevance of soil–soil friction at the GGR apertures, to the high percentage of fines of the soil used in the research (D50 = 1·00 mm), and to the smoother solid lateral surface of the extruded GGR when compared with the surface of the GTX or GC.

Experimental investigation on the pullout behaviour of geosynthetics embedded in a granite residual soil

Geosynthetics, including geogrids and geotextiles, have been extensively used for stabilisation and soil reinforcement in several geotechnical structures, such as foundations, abutments, walls and slopes. In these applications, soil–geosynthetic interaction plays a determinant role. This paper describes an experimental study carried out using a large-scale pullout test apparatus, aiming to investigate the pullout behaviour of different geosynthetics embedded in a granite residual soil. The study involved two geogrids (one biaxial and the other uniaxial), one geocomposite reinforcement (high-strength geotextile) and one geotextile. The soil was compacted to different relative densities. Test results have revealed that soil–geosynthetic interaction under pullout loading conditions is highly influenced by the geosynthetic properties and soil density. Regardless of soil density, the biaxial geogrid exhibited higher pullout resistance than the other geosynthetics. At maximum pullout force, the deformation along the length of the geotextiles was considerably more pronounced than that along the geogrids. For the conditions adopted in this study, the soil–geosynthetic pullout interaction coefficients ranged from .25 to .52. In general, the values of the scale effect correction factor obtained for the geotextiles were slightly lower than the value recommended by the Federal Highway Administration in the absence of test data.

Geotechnical characterization of recycled C&D wastes for use as trenches backfilling

DTU Orbit (03/11/2019) Recycling of MSWI fly ash in clay bricks-effect of washing and electrodialytic treatment Fly ash generated from municipal solid waste incineration (MSWI) is a hazardous waste due to presence and leachability of heavy metals and organic pollutants (e.g. dioxins and polycyclic aromatic hydrocarbons). In 2000, approximately 25 Mt/year of fly ash was generated in USA, Japan and EU (Reijnders 2005). Electrodialytic remediation (EDR) is one technique for MSWI fly ash treatment (Ferreira et al. 2005), where an electric DC field is applied to an ash-water suspension to extract and separate heavy metal by migration towards anode or cathode through ion exchange membranes. Ferreira et al. (2008) observed that in MSWI ash treated by water washing and EDR, metals were mainly in the strongly bonded and residual phases, indicating a reduction in the ash’s environmental risk. Belmonte et al. (2016) made Greenlandic bricks (∼2 g discs) containing 20% and 40% of EDR treated MSWI fly ash, and found that bricks had a low durability and high leaching of As and Cr. In the present study, fired fly ash-clay bricks with a larger size and with lower EDR-treated ash (water-washed before EDR) contents (5%, 10% and 20%) were made and characterized. These bricks were compared with 100% clay bricks and with bricks made from original MSWI fly ash at 20% substitution rate. The feasibility of incorporation of MSWI fly ash treated by combined washing and EDR in production of sintered clay bricks was investigated.

REVIEW OF SEISMIC PERFORMANCE OF GEOSYNTHETIC REINFORCED SOIL RETAINING WALLS

Abstract. Geosynthetic reinforced soil (GRS) retaining walls have been increasingly used as alternative to concrete gravity retaining walls. In GRS retaining walls, the concrete mass, that resist to the destabilizing forces, is replaced by a mass of soil reinforced with geogrids or other polymeric material. One of the main advantages of GRS retaining walls is their lower cost when compared to concrete retaining walls. Furthermore, GRS retaining walls built in seismically active area have performed well during major earthquakes. The seismic design of GRS retaining structures is traditionally based on Mononobe-Okabe earth pressure theory with distinct approaches for the distribution of the dynamic lateral earth pressures. The lack of improvement in seismic design of GRS retaining walls has led in recent years to some physical and numerical studies, involving large or reduced scale model shaking table tests and powerful numerical tools. This paper presents a review of selected published work, including physical and numerical models, trying to identify the main parameters with greatest influence on the seismic performance of GRS retaining walls. The paper is focused on numerical simulations verified against results physical model tests. Post-earthquake investigations are also summarized. The main conclusions are highlighted and common trends are identified.

Seismic response analysis of a geogrid reinforced wall constructed with recycled Construction and Demolition Waste

Over the last years the environmental sustainability has been demanding a pro- gressive increase in the waste valorisation in construction. The valorisation of Construction and Demolition Wastes (C&DW) reduces the use of natural resources (non-renewable) and, simultaneously, avoids congesting landfills with inert wastes coming from buildings and other infrastructures. Although some studies have been carried out on the use of recycled C&DW in construction industry, their valorisation as fill material in geosynthetic reinforced structures is almost an unexplored field. A research project aiming to contribute to the sustainable ap- plication of recycled C&DW as backfill material in geosynthetic reinforced structures, is be- ing developed at University of Porto, Portugal. Preliminary results of this research are presented in this paper. In this work the two-dimensional finite difference program Fast Lagrangian Analysis of Con- tinua (FLAC) was used to model the behaviour of a geogrid reinforced wall, constructed in Brazil, with recycled C&DW. The wall is 3.6m high and was constructed at an inclination of 1:4.3 (wall batter of 13o from vertical). The backfill was reinforced with six layers of geogrid placed at 0.6 m of vertical spacing and 2.52 m long. The seismic response of a similar wall, hypothetically constructed with recycled C&DW coming from a Portuguese recycling plant, is also evaluated. An earthquake ground motions artificially generated for the greatest seismicity area of Por- tugal was considered as seismic input. Two constitutive models were used to model the back- fill C&DW material: the Mohr-Coulomb model and a Strain-Softening model. Permanent displacements of the wall face, settlements and reinforcement tensile forces are analysed and discussed. The numerical simulations have shown that the possible decrease of the backfill shear strength during cyclic loading is an important issue to be studied more closely. Not- withstanding it was concluded that a well compacted and drained recycled C&DW can be used as fill material in geosynthetic reinforced structures.