Rafaela Cardoso

Instituto Superior Técnico · DECivil

The effectiveness of biocementation to treat the collapse potential of a real soil is investigated. The analysis is done considering structural changes experienced by the soil during the treatment and not only in service. Oedometer tests were performed on treated and untreated soil samples, both in saturated and unsaturated states, to study structu...

Road drainage systems collect runoff water during rainfall; however, their malfunction or defective discharge systems may cause downslope soil erosion through scour and runoff. Under climate changes scenario it is ex�pected the occurrence of intense rainfalls with high erosion potential, and therefore it is important to increase slope resilience ag...

Biocementation consists in using enzyme or non-pathogenic bacteria to produce calcium carbonate (biocement) and is being used to seal cracks in stone and concrete for retrofitting and consolidation works, as alternative to conventional solutions such as using polymeric mortar. The results of an experimental study performed to evaluate the efficienc...

Biocementation, or microbially induced calcite precipitation (MICP), is a technique currently appraised for the improvement of sandy soils. These type of soils are good candidates for MICP-based soil improvement due to their relatively large voids size associated to high permeability and room available for bacteria colonization. Only few studies us...

Measurements taken on a historical dike in the Netherlands over one year showed that interaction with the atmosphere led to oscillation of the piezometric surface of about 0.7 m. The observation raised concerns about the long-term performance of similar dikes and promoted a deeper investigation of the response of the cover layer to increasing clima...

Biocementation consists in using urease enzyme and a solution rich in urea and in calcium to precipitate calcium carbonate (biocement). When applying this treatment in soils, the biocement minerals bond the grains improving overall soil’s hydro-mechanical properties. For the practical use of this technique, it is necessary to be able to predict the...

Biocementation consists on the use of microorganisms (bacteria) to promote the precipitation of calcium carbonate (biocement). When this technique is applied in soils or fractured rocks, the biocement which is precipitated can fill voids and discontinuities, being easy to apply, not very intrusive and requiring low energy consumption. There are sev...

Shallow Geothermal Energy (SGE) exchanges heat with the ground. In continuous, long-term operation, the initial temperature field can be disturbed, and subsurface thermal changes can be developed. In this paper, the thermal impact of a SGE system under a Mediterranean climate is handled. Temperature monitoring was conducted on 15 investigation bore...

The proper assessment of soil thermal properties, such as thermal conductivity, assumes a particular relevance for the design of Ground Source Heat Pump systems, as it determines the heat transfer and the energy efficiency design. Multiple methods can be used for thermal conductivity estimation, however significant scatters in measurements are ofte...

Salinization/desalinization processes in the soil vadose zone are important to define agricultural irrigation and drainage schedules, especially in reclaimed crop areas. Numerical modeling of soil–climate interaction is a very helpful tool to understand soil salinity distribution and solute transport and therefore define efficient desalination solu...

Shallow Geothermal Energy (SGE) exchanges heat with the ground. In continuous long-term operation, the initial temperature field can be disturbed, and subsurface thermal plumes can be developed. In this paper, the thermal impact of a SGE system under Mediterranean climate is handled. Temperature recordings from 104 thermal probes placed in depth al...

Soil erosion in slopes mainly occurs due to runoff water. Biocementation may be an alternative to traditional stabilisation methods to prevent this phenomenon. In this research, enzyme induced calcium carbonate precipitation (EICP) was tested to analyse its efficiency in preventing soil erosion. To do so, two small slopes made of uniform-graded siz...

Non-destructive tests, such as geophysical electrical resistivity tests, can be useful to determine how Biocementation treatment in soils is distributed in volume. However, electrical resistivity is affected not only by void ratio but also by water content and the chemical nature of the pore fluid. This paper presents an experimental investigation...

Biocementation treatment consists in using bacteria or other biological agents to promote the precipitation of calcium carbonate (biocement) in the soil pores. When used in slopes for protection against surface erosion, this treatment creates a stiff and strong pervious cover, allowing infiltration necessary to reduce water runoff. The knowledge of...

In the last decade, a significant effort was made by research institutions and industry to change ordinary construction materials into green, smart, adaptive, and advanced materials. Green materials (for example bio-cement) are developed to reduce carbon footprint and waste, using biological agents replacing common binders. Smart materials can moni...

Monitoring structural behavior of earth structures during construction and in service is a common practice done for safety reasons, consolidation control and maintenance needs. Several are the techniques available for measuring displacements, water pressures and total stresses, not only in these geotechnical structures but also at their foundations...

The effectiveness of biocementation to treat the collapse potential of a well graded sand is investigated. The novelty on the application of this treatment for this purpose is that the analysis is done considering structural changes experienced by the soil during the treatment and not only in service. Oedometer tests were performed on treated and u...

Biocementation is a soil treatment technique wherein bacteria living in soil pores promote the precipitation of calcium carbonate. One of the most recent applications of this treatment is to provide resistance against the erosion of slopes by creating a resistant cover but still allowing infiltration to avoid water runoff. For modeling infiltration...

This study investigated the use of the Formation Factor of the material as an alternative way to estimate soil-cement strength involving no destructive tests. This factor is obtained from Archie’s Law and consists of the ratio of pore water electrical conductivity to saturated porous material electrical conductivity, being related to porosity by co...

Biocementation can be an alternative to traditional stabilisation methods to prevent runoff soil erosion in slopes. Laboratory scale tests were made on small sand slopes and treatment efficiency was analysed using structure from motion (SfM) photogrammetry performed with a mobile phone.

Runoff water may cause soil erosion, being this a concern affecting multiple areas. Monitoring tools can help design efficient solutions to prevent erosion. This is usually done using reliable tools such as terrestrial laser scanners (TLS). However, for very fast erosive processes, the rate at which changes occur is greater than the scanning time a...

Biocementation is a relatively recent soil improvement technique which consists in using biological agents to promote the precipitation of calcium carbonate (biocement) that works as a cement binding the grains. Some of the main difficulties when using this technique are how to predict the amount of biocement precipitated by a fixed dosage of enzym...

In this paper capillary stresses and water retention of regular arrangements of rough spherical particles are analysed to shed light on the effective stress in unsaturated soils. These arrangements can be used to model soils with uniformly graded round particles such as sand as they are simpler to analyse due to their symmetries. Capillary stress d...

Da mistura de solos com ligantes hidráulicos resultam materiais cimentados artificialmente através de ligações físicas (minerais resultantes da hidratação do ligante). A geometria das ligações é controlada pela quantidade de água usada no processo construtivo que, por sua vez, depende de requisitos de trabalhabilidade e da adição ou não de adjuvant...

A new constitutive model for the soil-water retention behaviour of unsaturated soils is proposed, able to reproduce the main drying and wetting paths, the cyclic retention behaviour and its dependence on the specific volume. The most significant aspect is the inclusion of the evolution, with the specific volume, of the degree of saturation when suc...

Biocementation is being used to seal cracks in stone and concrete for retrofitting and consolidation works, as alternative to conventional solutions such as using polymeric mortar. As when such traditional techniques are used, joint thickness and roughness play an important role on sealing efficiency and this must be investigated when using bioceme...

In this paper, the Discrete Element Method is used to study the effect of capillary forces, in equilibrium with the ambient relative humidity, on the response of irregular arrangements of equal-sized spheres, simulating a fine uniformly graded quartz sand. The effect on the isotropic compression was investigated by applying an increase in total str...

In shallow geothermal energy systems (SGES) thermal conduction can be considered the dominant process in the heat transfer between the primary circuit (borehole heat exchanger or thermoactive geostructure) and the surrounding ground. Thus, a proper characterization of soil thermal properties, namely of its thermal conductivity, is mandatory for eva...

Microbially induced carbonate precipitation (MICP), or biocementation, consists in using microorganisms living in the soil to produce calcium carbonate (biocement). This mineral bonds the grains and therefore improves the soil hydro-mechanical properties. When using this technique, one of the challenges is to ensure homogeneous treatment in the ent...

The contribution of indigenous bacteria and of some possible precipitation due to chemical reactions occurring during the treatment of sandy soils through microbially induced calcite precipitation (MICP) is investigated in this paper considering two different grading size distributions. This is a novelty, because the presence of the feeding solutio...

In this paper, the Discrete Element Method is used to study the effect of capillary forces, in equilibrium with the ambient relative humidity, on the response of irregular arrangements of equal-sized spheres, simulating a fine uniformly graded quartz sand. The effect on the isotropic compression was investigated by applying an increase in total str...

Electrical resistivity of soils can be used to evaluate the level of contamination in soils in geophysical prospection tests. The chemical composition of pore fluid also corresponds to a given water potential, named as osmotic suction. Therefore both electrical resistivity and osmotic suction can be related when soil is saturated. This paper invest...

Microbially induced carbonate precipitation (MICP), or biocementation, consists in using microorganisms living in the soil to produce calcium carbonate (biocement). This mineral bonds the grains and therefore improves the soil hydro-mechanical properties. When using this technique, one of the challenges is to ensure homogeneous treatment in the ent...

Cracking due to desiccation can compromise the behaviour of earth structures built with compacted clayey soils by promoting water access and consequent volume changes on further wetting. Tensile strength therefore is important to be considered when studying the behaviour of such structures, and in particular its dependence on the degree of saturati...

Slate is a natural stone widely used for building, for which is subjected to regulations and standards in order to be commercialized. As far as the influence of water is considered, only detailed studies are compulsory when the water absorption is higher than 0.60%. However, the mechanical behavior of this layered material depends on water content,...

Biocementation is being used mainly to improve the mechanical and hydraulic properties of soils. This technique consists in adding bacteria and feeding solution to soils to produce calcium carbonate (biocement). When produced in enough quantity, calcium carbonate formed around bacteria present in the soil pores create bonds connecting the particles...

This paper describes how Electrokinetic Treatment (EKT) was used to decontaminate compacted kaolin, artificially contaminated with leachate obtained from a landfill waste site near Lisbon, Portugal. An experimental test was conducted in a laboratory scale setup with focused on monitoring electrochemical properties of the soil and pore fluid during...

Soil improvement using ureolytic bacteria or other biological agents is a promising technique currently under investigation. It is based on the precipitation of calcium carbonate (biocement) due to the enzymatic hydrolysis of urea. The biocement produced clogs the soil pores, consequently bonding the soil grains and increasing overall strength and...

The thermal properties of samples of compacted white kaolin were investigated after suction application using vapor equilibrium in wetting and drying paths. The samples tested were compacted for the same water content and void ratio was changed to achieve different structures due to compaction. The water retention curve of the samples was determine...

Alguns aterros da Autoestrada A10 foram construídos com margas compactadas, que consistem num conjunto de fragmentos cujas dimensões e arranjo dependem do processo de compactação. Porque as margas são materiais com comportamento evolutivo, os fragmentos de marga sofrem forte degradação física quando sujeitos às acções atmosféricas (essencialmente m...

A numerical study was performed for evaluating the geothermal potential of foundation piles used as heat exchangers with the ground, for seasonal heat storage. It is based in a case-study of a building in Aveiro Campus University, equipped with a shallow geothermal heat pump system (GSHP) designed to support most part of the energy demands for the...

avieira@lnec.pt RESUMO A instalação de fundações termoactivas em edifícios é uma solução energeticamente eficiente, bastante utilizada em vários países europeus. Para a modelação destes elementos é necessário conhecer as características térmicas dos solos de fundação, nomeadamente a sua condutividade e capacidade térmicas. Estes parâmetros dependem...

A utilização de geoestruturas termoativas, em particular estacas termoativas e BHE (Borehole Heat Exchangers) surge cada vez mais como uma via de utilização das camadas superficiais de solo como reservatório térmico para efeitos de climatização de edifícios. Sendo uma tecnologia relativamente recente, subsistem ainda dúvidas quanto à quantificação...

Soil-cement mixtures are largely used in civil engineering applications. Nevertheless, their mechanical behavior is not properly defined in current constitutive modeling. In this study, an elastoplastic subloading surface model for cemented materials is used to simulate the behavior observed in consolidated undrained triaxial tests performed on sam...

In general, the prescription of the amount of water used in soil–cement mixtures is done to define the optimal compaction conditions for bases and sub-bases, or to ensure the fluidity necessary for a good mixture by injection. A better knowledge about the hydraulic behaviour of the resulting mixtures may be useful in service conditions, when permea...

Soil-Cement mixtures are used in several geotechnical applications and consist of artificially structured materials with stable fabric due to the presence of artificial bonds, which are the hydrated cement minerals coating the aggregates (soil particles). An extensive experimental study was performed on samples of an artificially cemented silty san...

In clayey soils the electrical current flows through the liquid phase (free water) and the surfaces of the electrically charged clay minerals, where water is adsorbed. The distinction between the two paths cannot be done by the usual way of considering only the degree of saturation (volume of water) or the gravimetric water content (mass of water)....

Currently there are no small sensors that can be incorporated inside soil samples for laboratory testing, to monitor water transport during loading. This is an important limitation to a better understanding of the hydromechanical coupled behaviour of soils. A sol-gel relative humidity sensor (11 mm × 11 mm), microfabricated in a clean room environm...

The quantification of the breach hydrograph of an overtopped earth dam remains a challenge, even in controlled laboratory conditions. In this work, the breach hydrograph is calculated as the product of the velocity normal to a breach cross section and the estimated area of that cross section. Although theoretically simple, because it is based on th...

The increment of secondary deformations due to electrokinetic treatment (EKT) was studied considering that these deformations are associated to the mobilization of the water adsorbed by the clay minerals. This water is at the level of microstructure, and therefore volume changes occur while water is flowing from the micro to the macropores. Water t...

This paper describes the experimental procedure followed to fabricate and validate sol-gel based RH sensors to be incorporated in soil specimens for standard laboratorial tests. It is the first time such sensors were used for soil suction measurement. They are microfabricated relative humidity sensors (footprint area 11000 μm ×22000 μm) operating b...

Soil-Cement mixtures are artificially structured materials with stable fabric due to the presence of artificial bonds. This type of materials is used in several geotechnical applications such as in pavement base layers in transportation infrastructures. In this paper artificially cemented silty sands are studied adopting dosages of 10% and 13% of P...

Traditionally, electrical resistivity tests are being used for geophysical characterization but the electrical properties of soils can also be explored for compaction control of geotechnical works. Theoretical relations for estimating the electrical resistivity can be derived based on the degree of saturation and can be plotted in a chart relating...

Electrokinetic, or Electrochemical treatment, is one of the possible techniques to decontaminate impervious soils such as clayey soils. Real time monitoring of the electrical resistivity of a soil can be a useful tool in controlling and assessing the removal of water and ions during decontamination using this technique. Field conditions were simula...

Electrical resistivity, saturated hydraulic permeability and P wave velocity are investigated for an artificially cemented sand. The calibration of some known equations used in geophysical characterization tests relating these properties is done considering the presence of artificial bonds. In this case bonds are the hydrated cemented minerals coat...

The main findings when using microbially induced calcite precipitation, MICP, in two case-studies, a sandy soil and a mortar surface, are presented. The first case is focused on studying biocementation in sands to improve their mechanical properties. Tests were carried out with the aim to check the biological activity and understand MICP effects on...

Jet grouting is a known ground improvement technique largely used worldwide for different applications. One of the major limitations of this technique is mainly related to obtaining good predictions of the geometry of the final grouted body, as it is a function of the injection parameters and soil properties. Over the years, many studies have been...

Prospection techniques based on measuring the electrical resistivity of geomaterials are being used mainly for geophysical characterization, for evaluating soil contamination and the extension of contaminated areas, in addition to the compaction control in geotechnical works. This technique is based on the fact that contrasts in electrical resistiv...

The use of recycled aggregates (RA) in construction constitutes a significant step towards a more sustainable society and also creates a new market opportunity to be exploited. In recent years, several case-studies have emerged in which RA were used in Geotechnical applications, such as filling materials and in unbound pavement layers. This paper p...

Data of the water retention domain measured on upper Jurassic marl from Portugal are presented. Under drying and wetting cycles physical degradation was observed, which causes an evolution of the microstructure and of the water retention domain of the material. Classical water retention models from the literature are not able to account for evolvin...

The control of water content or water movement in soils is fundamental not only to ensure some desired characteristics but also for different applications, such as consolidation, dewatering, conditioning, and decontamination. In clayey soils, due to the small size of clay particles their behavior is ruled by the interactive electrochemical forces r...

Some embankments on the A10 motorway, in Portugal, were built with marls. A lime treatment was prescribed for the material placed on the shoulders to protect it from the actions of the weather. This zoned profile design solution was a cheaper alternative to giving the embankment a full treatment.Two major concerns emerged during the construction, w...

A consideração das ações atmosféricas no dimensionamento de estruturas geotécnicas tais como taludes, aterros, barragens de aterro e fundações, justifica-se quando as deformações devidas a ciclos de molhagem e secagem (ciclos de sucção) ultrapassam valores que podem comprometer a funcionalidade destas estruturas. Para o cálculo das deformações devi...

Floods resulting from dam failures are responsible for devastating disasters from which consequences include economical and human losses, which entirely depend on the inundated area extension, the number of lives at risk and on the warning time available (Wahl, 1998). Overtopping is the most common cause of failure in recent dams. Also, embankme...

The combined effect of flow induced by the increment of vertical stress and by the presence of a constant electrical potential is analysed using one-dimensional consolidation theory. Electro-hydro-mechanical coupling is considered. Data from oedometer tests performed on saturated white kaolin specimens, in which a DC voltage was applied during the...

This paper focuses on understanding the mechanical response of non-saturated compacted marls used to build some motorway embankments in Portugal. The compacted material consists of crushed marls, which can be assumed to be a set of fragments with relatively large dimensions. Experimental studies on the hydromechanical behaviour of this compacted, e...

The compressibility of granular soils is studied by adopting a micromechanical approach in which soil is considered as a set of particles and volume changes result from their interaction. Oedometric tests were performed in four different granular materials which grains have different stiffness and water sensitivity. The tests were performed in dry...

Jurassic marls from Abadia, Portugal, were used in the construction of some motorway embankments. Large fragments of this evolving material remained after the construction process, and their degradation was of concern because of the expected change of the engineering properties of the compacted material. The material exhibits a very complex behavio...