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- Geostatistical analysis of settlements induced by liquefaction: case study river Lis Alluviums, PortugalPublication . Veiga, Anabela; Mourato, Sandra; Rodrigues, HugoIn the present work the result of the application of geostatistical methods to soil settlement data is presented. The settlements are induced by liquefaction as a result of an earthquake of magnitude 5.5. In the present paper the ArcGIS Geostatistical Analyst software was used, where a number of Kriging methods are available. Geostatistical analysis was performed on two phases: (i) modelling the semivariogram to analyse the surface properties and; (ii) application of a Kriging method. The best adjustment was obtained with a Gaussian model with a first order function trend removal. The settlement values were obtained from the analysis and treatment of results of SPT tests carried out on soils corresponding to alluvial soils in the urban centre of Leiria, Portugal. The results show a significant area where are expected large settlements that can generate significant damages in the building stock and infrastructures.
- Characterization of the Dagorda Claystone in Leiria, Portugal, Based on Laboratory TestsPublication . Veiga, A.; Quinta-Ferreira, M.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.
- Diapir Mudstone Properties, Leiria, PortugalPublication . Veiga, Anabela; Quinta-Ferreira, MárioThe engineering geology study of the Dagorda Formation outcropping in the core of the Parceiros-Leiria diapir, was based on field reconnaissance, on in situ and laboratory tests. The formation is constituted mainly by clay and silt, sometimes with sand, occasionally with gypsum or marls. The engineering geology properties of the fine materials showed large variability depending on their degree of consolidation and water content, ranging from very poor to fair. The presence of soluble minerals can develop dissolution voids. When exposed, for example in excavation surfaces, they tend to deteriorate because of decompression and exposure to the external environment, easily losing strength when wet, which facilitates the failure on slopes or foundations. The presence of soluble minerals (gypsum and rock salt at greater depth) can develop dissolution voids due to circulating water. In depth the variation of the mechanical properties may lead to difficulties in foundation ground, as well as difficulty of concreting piles, due to the escape of concrete between neighboring piles along fissures and dissolution voids. The occurrence of very low strength seams, may constrain the stability of cuttings. The unusual geotechnical behavior of these terrains due to the presence of both clay and soluble minerals must be taken into account. In all engineering works to be carried out on these materials it is recommended to develop a detailed engineering geology study prior to construction, in order to early identify the problems and to define the suitable solutions and construction techniques to be adapted to each case. The construction works must have geotechnical assistance in order to improve the construction operations.