Mário Quinta-Ferreira

In-place evaluation of a limestone base course modulus, using a van-integrated falling weight deflectometer (FWD) and the GeoGauge (SSG)

A comparative evaluation of the in-place stiffness modulus using a van-integrated falling weight deflectometer (FWD) and the GeoGauge (soil stiffness gauge – SSG) was done on a limestone all-in-aggregate (AIA), used in the base course of a highway pavement. The tests were done in two campaigns, one for each unbound granular layer of 0.15 m thickness, along 510 m, using five alignments. Considering the whole granular materials used, the dry unit weight (γd) is related with the stiffness modulus obtained with the SSG. The stiffness moduli obtained for the SSG and for the FWD in the same test point are not correlated. Considering as reference the equivalent modulus obtained with the FWD, the moduli computed for the 85th percentile with both the FWD and the SSG show a difference lower than 20%. These results emphasise the possible use of the SSG as a reliable procedure for stiffness modulus evaluation of unbound limestone bases.

Natural and man-made causes for the “Elísio de Moura” earth flow in Coimbra, Portugal

The paper reports the 27 December 2000 landslide, which occurred in the city of Coimbra, central Portugal, affecting loose fill soils and slope debris derived from the red sandstone of Triassic age. With urban spread, the base of the hill slope on which farming had taken place over many centuries was terraced to provide residential properties; the excavated material was end-tipped at the top of the slope, modifying the slope gradient from the original 18° to 38°. The loose fill was placed without engineering precautions, directly on to the debris slope material. Following a small slip in 1998, remedial works were undertaken involving large diameter piles anchored into the bedrock. This engineering construction formed the back slope and restricted the extent of the December 2000 landslide, which occurred during a period of unusually heavy rainfall.RésuméL’article présente le glissement du 27 décembre 2000 qui s’est produit dans la ville de Coimbra, au Portugal, affectant des remblais meubles et des formations de pente dérivées des grès rouges d’âge triasique. Dans le cadre d’une opération d’urbanisme, la base d’une colline, où des exploitations agricoles ont existé depuis des siècles, a fait l’objet de terrassements en vue d’un aménagement résidentiel. Les matériaux excavés furent déversés au sommet de la pente, modifiant l’angle de pente d’une valeur originale de 18° à 38°. Le remblai meuble fut mis en place sans précaution particulière, directement sur les formations de pente. A la suite d’un petit glissement en 1998, des travaux de confortement furent entrepris, comportant des pieux de grand diamètre ancrés dans le substratum. Ces travaux d’ingénierie permirent de limiter l’extension du glissement de décembre 2000, qui se déclencha pendant une période de pluies intenses inhabituelles.

Rock Fall Analysis on the City of Lubango, SW Angola

A study of the rock falls conditions of an area in the city of Lubango (Angola) was carried out. The upper parts of the studied slopes are constituted by whitish and grayish quartzites and pink, brown or reddish sandstone from the Chela Group of the Precambrian age. Debris deposits can be found at the toe of the slope. The slope movements are more frequent during the rainfall period, which run from October through April. A lithological and volumetric characterization of the rock fall blocks present on the study area was carried out. The software program Rocfall of the Rocscience packages was used to study the rock fall paths. The rocks location, mass and velocity as well as the properties of the slope material were defined and the rock falls trajectories were studied. The possible rock fall trajectories on the slope can cause significant damage to homes. According to the stability study, some mitigation and prevention procedures were suggested in order to allow human occupation of the Lubango’s urban area adjacent to the slopes.

Geological-Geotechnical Studies for the Ore Transport Railway Line “S11D—Sudeste do Pará”, Brazil

In Brazil, the railway transport of iron ore moves large quantities and needs to overcome huge distances between the mining areas and the shipping harbors. As the Brazilian railway network requires renewal and expansion, sound procedures to conduct suitable engineering geology studies are needed. The objectives, methodology, and study phases are presented, focusing on the geological and geotechnical constraints of the terrains crossed by the railway line. These constraints may increase the costs, cause construction delays, or generate difficulties during construction or operation. The new iron ore railway project, “S11D—Ramal Ferroviario Sudeste do Para” in Brazil, is used as a case study. It is 100 km in length, connecting the new S11D mine to the existing Carajas railway, and hauls the iron ore to a shipping port, the Ponta da Madeira Maritime Terminal. The geological-geotechnical studies developed for the design, and utilized during construction along the S11D railway branch line, are presented and discussed. Several unusual aspects of the engineering geology studies for an excavation, an embankment, a bridge, a tunnel, and for the location of natural granular materials for sub-ballast and ballast layers are presented. It is concluded that continuous improvement of the engineering geology studies is desirable to increase the efficiency of the design, construction, and operation of a railway.

Characterization and rehabilitation of the “Porta Férrea” stone materials, University of Coimbra, Portugal

The “Porta Férrea” (Iron Gate) is the main access to the “Paço das Escolas” (University Palace) at the University of Coimbra, Portugal. It has undergone several adaptations and reconstructions from an original castle gate until the present portal that was built in 1634. The inscription of “University of Coimbra, Alta and Sofia” in the UNESCO Word Heritage list increased the interest in developing conservation works and to do the characterization of the limestone materials of the “Porta Férrea” portal. To support the conservation works, a research project was developed. The intervention plan, the sampling and testing performed and the conservation developed are presented. The rock material in the portal is the Ançã limestone, showing very high porosity around 30%, creating quite important degradation and conservation problems. The deterioration pattern, analyses performed, and the conservative works are presented. In this study it can be confirmed that Ançã limestone of “Porta Férrea” do not decay according a theoretical predictable pattern in response to polluted environments, as the defined for Portland limestone, assuming erosion rates and forms controlled by a range of micro-environment conditions particularly related with architectural constraints.

Assessment of the Alteration of Granitic Rocks and its Influence on Alkalis Release

Several concrete structures had shown signs of degradation some years after construction due to internal expansive reactions. Among these reactions there are the alkali-aggregate reactions (AAR) that occur between the aggregates and the concrete interstitial fluids which can be divided in two types: the alkali-silica reaction (ASR) and alkali-carbonate reaction (ACR). The more common is the ASR which occurs when certain types of reactive silica are present in the aggregates. In consequence, an expansive alkali-silica gel is formed leading to the concrete cracking and degradation. Granites are rocks composed essentially of quartz, micas and feldspars, the latter being the minerals which contain more alkalis in their structure and thus, able to release them in conditions of high alkalinity. Although these aggregates are of slow reaction, some structures where they were applied show evidence of deterioration due to ASR some years or decades after the construction. In the present work, the possible contribution of granitic aggregates to the interstitial fluids of concrete by alkalis release was studied by performing chemical attack with NaOH and KOH solutions. Due to the heterogeneity of the quarries in what concerns the degree of alteration and/or fracturing, rock samples with different alteration were analysed. The alteration degree was characterized both under optical microscope and image analysis and compared with the results obtained from the chemical tests. It was concluded that natural alteration reduces dramatically the releasable alkalis available in the rocks.

Characteristics of aggregates used in road construction in Portugal, complying with the requirements of European Conformity (CE marking)

In the context of European Conformity (CE marking), an inventory on the aggregates used in road construction in Portugal, encompassing 145 producers (68%) and 228 production centres (79%) was carried out, aiming to support the normalisation of activity for aggregates. A broad and representative characterisation of the geometric, physical, mechanical, chemical, and weathering properties of the aggregates was obtained. A total of 106 aggregate sizes allowed the delineation of two predominant dimensional combinations. Aggregates showed dependence on the lithological type, especially with respect to geometrical, physical, and mechanical properties. More than 30% of the all-in aggregates did not satisfy the sand equivalent category SE50 and the methylene-blue category MB2.5, requiring great care in the establishment of specifications. For high levels of performance, in terms of mechanical resistance, the percentage of aggregates satisfying the Los Angeles category LA30 and the polished stone value category PSV50 was quite low. Comparisons with other countries were not possible as no similar data compilation or inventory was found. The present research aims at improving the application of European aggregate standards and, hopefully, at triggering similar work in other countries, especially European ones, in order to contribute to new international standards or to the revision of those standards currently in force.

False low water content in road field compaction control using nuclear gauges: a case study

Abstract During the construction of a highway in the north of Portugal, it was verified that in a few places, the compaction control of the road fill materials presented unexpected results with the surface moisture-density gauge (SMDG). The water content was lower than measured by oven drying, and the density and compaction grade were much higher than when using the sand cone. In an effort to understand the reasons for this unexpected offset, the road fill material was tested in situ with two different brands of SMDG, extra sand cone tests were performed and samples were collected at the test sites and tested in the laboratory to determine the water content by oven drying. The local geology, mineralogy, geochemistry and radiation level of the fill materials were studied. It was concluded that the incorrect results were caused by the presence of chemical elements in the road fill materials, mainly manganese, chlorine, cadmium and boron, which are able to capture the neutrons released by the SMDG, delivering a false low water content (FLoW). An index to evaluate the susceptibility of the soil to present a FLoW is proposed. Despite the reliability of the SMDG in most fill control, it must always be used with great care, after cross-checking its results with other direct control tests.

Characterization of the Dagorda Claystone in Leiria, Portugal, Based on Laboratory Tests

The Hetangian Dagorda claystone Formation occupies the core of a diapir outcropping in part of the city of Leiria, exhibiting a complex geological structure. The geological and geotechnical characterization is presented based in field observation and laboratory tests allowing to conclude that the Dagorda clay soils exhibit an unfavourable behaviour for urban occupation, due to the presence of expansive clay minerals. When partially saturated these soils can lead to cracking of walls and floors, or even to endanger the stability of buildings, if they have not been strengthened to resist to expansive soil. The presence of soluble minerals, mainly gypsum and seldom halite, can allow the formation of voids and eventually the deformation or collapse of the ground. Suitable safety procedures, in order to prevent hazards should be used.