Ingenieria Civil

IAEG Commission No. 1—Engineering Geological Maps—is developing a guide to hazard maps. Scientists from 17 countries have participated. This paper is one of a series that presents the results of that work. It provides a general review of GIS landslide mapping techniques and basic concepts of landslide mapping. Three groups of maps are considered: maps of spatial incidence of landslides, maps of spatial–temporal incidence and forecasting of landslides and maps of assessment of the consequences of landslides. With the current era of powerful microcomputers and widespread use of GIS packages, large numbers of papers on the subject are becoming available, frequently founded on different basic concepts. In order to achieve a better understanding and comparison, the concepts proposed by Varnes (Landslide hazard zonation: a review of principles and practice, 1984) and Fell (Some landslide risk zoning schemes in use in Eastern Australua and their application 1992; Landslide risk assessment and acceptable risk. Can Geotech J 31:261–272, 1994) are taken as references. It is hoped this will also add to the international usefulness of these maps as tools for landslide prevention and mitigation. Six hundred and sixty one papers and books related to the topic are included in the references, many of which are reviewed in the text. La Commission N°1 de l’AIGI ≪Cartes de géologie de l’ingénieur≫ réalise un guide sur les cartes d’aléas. Des scientifiques de 17 pays ont apporté leur contribution. Cet article est l’un d’une série d’articles relatant les travaux de cette Commission. Il présente les concepts de base de la cartographie de glissements de terrain ainsi qu’un panorama de l’apport des techniques SIG (Systèmes d’Information Géographique) à cette cartographie. Trois groupes de cartes ont été considérés: des cartes d’occurrence spatiale de glissements de terrain, des cartes d’occurrence spatio-temporelle et de prévision de glissements de terrain et des cartes d’évaluation des conséquences de glissements de terrain. A notre époque de développement de la micro-informatique et des logiciels SIG, de nombreuses publications sont produites sur ce sujet, avec différentes bases conceptuelles. Afin de faciliter compréhension et comparaisons, les concepts proposés par Varnes (Landslide hazard zonation: a review of principles and practice, 1984) et Fell (Some landslide risk zoning schemes in use in Eastern Australua and their application 1992; Landslide risk assessment and acceptable risk. Can Geotech J 31:261–272, 1994) sont pris comme référence. On espère que le travail réalisé rendra plus facile l’utilisation de ces cartes comme outil de prévention et de limitation des effets des glissements de terrain. Six cent soixante une articles et ouvrages relatifs au sujet traité son référencés en bibliographie, nombre d’entre eux étant appelés dans le texte de l’article.

Fine-grained, more or less cohesive carbonate materials are extremely widespread in terms of surface area and are, therefore, commonly used as materials to construct impermeable cores for dams. However, it has not been adequately documented whether the carbonate content in fine-grained soils significantly affects their engineering behaviour. The present study shows that the carbonate content substantially influences the engineering behaviour of clayey material. For this, we subjected 32 samples to different laboratory tests, such as the normal Proctor, the Atterberg limits, granulometric analysis, oedometric and undrained triaxial tests. The resulting parameters were correlated with the carbonate content of the samples.The materials studied in this work had been used in the construction of the impermeable core of the San Clemente Dam, belonging to the hydrographic basin of the Guadalquivir River (southern Spain). These marls present, as their prime characteristic, a carbonate content of the fine fraction consistently exceeding 50%, giving them special importance in the study of this phenomenon.In this study, a direct relationship was found between the geotechnical properties of the soils studied and their degree of compaction, with the carbonate content and the type of minerals in the clay being the main factors determining the behaviour of these soils. Finally, we conclude that the percentage of carbonates should be used as a classification criterion for the soils used to construct the cores of earth-filled dams.

This work presents the results of applying the matrix method in a Geographic Information System (GIS) to the drawing of maps of susceptibility to slope movements in different sectors of the Betic Cordillera (southern Spain). In addition, the susceptibility models built by the matrix method were compared with a multivariate statistical method, and the first method gave the best results. The susceptibility maps drawn by the GIS matrix method were validated by calculating the coefficients of association with the degree of fit between recent slope movements registered in 1997 and the different levels of susceptibility of previously drawn maps (1995–1996) in different representative zones of the Betic Cordillera (southern Spain). The first sector studied showed excellent degrees of fit, with an error of less than 10% for all the slope failures and 3% when considering only failures of natural origin. In the second sector, the relative errors were less than 5%. In the third sector, the error hardly exceeded 6%. The results are discussed in the different zones and for each type of slope movement. In any case, these results evidence the predictive capacity of susceptibility maps drawn in GIS by the matrix method, for a great number of slope movements.

Analysis of 171 samples taken from the Neogene cohesive soils of the Southeastern edge of the Granada basin shows inverse correlation between carbonate content and dispersion index and swelling behaviour and direct correlations between carbonate content and shear strength. This paper shows that carbonate content and clay fraction activity have a great influence on the compaction characteristics of soils. Marls of the middle and upper Tortonian age (lower marls) are inadequate for use as subgrade because of their high plasticity. In addition, marls of lower and upper Messinian age (upper marls) are inadequate for use as subgrade because of their high carbonate content. The relationship between carbonate content and geotechnical properties is particularly important because the changes caused by pedogenic dissolution and precipitation processes lead to changes in mechanical behaviour.

We present a new method for evaluating relative active tectonics based on geomorphic indices useful in evaluating morphology and topography. Indices used include: stream length-gradient index (SL), drainage basin asymmetry (Af), hypsometric integral (Hi), ratio of valley-floor width to valley height (Vf), index of drainage basin shape (Bs), and index of mountain front sinuosity (Smf). Results from the analysis are accumulated and expressed as an index of relative active tectonics (Iat), which we divide into four classes from relatively low to highest tectonic activity.The study area along the southwest border of the Sierra Nevada in southern Spain is an ideal location to test the concept of an index to predict relative tectonic activity on a basis of area rather than a single valley or mountain front. The study area has variable rates of active tectonics resulting from the collision of Africa with Europe that has produced linear east–west anticlinal forms, as well as extension with variable vertical rates of normal faulting to about 0.5 m/ky. We test the hypothesis that areas of known, relatively high rates of active tectonics are associated with indicatives values of Iat.

The geomechanical classification SMR (Slope Mass Rating) enables the preliminary assessment of the susceptibility of rock slopes to failure. The SMR index is obtained from Bieniawski's basic RMR (Rock Mass Rating) through an ``adjustment factor'' and an ``excavation factor''. Since its appearance in 1985, this classification has been used for appraisals and preliminary studies in many countries. The method is applied automatically by a Geographic Information System (Arc-Info GIS). The present study describes the methodology used and the results obtained after mapping the failure susceptibility in rock slopes by computing the SMR index using a GIS. Data have been gathered from the Digital Elevation Model (DEM), and by the statistical analysis of the parameters measured on the slopes. The methodology has been applied to the slopes along the N-340 road between Arraijana beach and Castell de Ferro (Granada, Spain). A total of 40 slopes have been studied along a linear distance of 4 km. As a result, in addition to all the factors that determine the SMR index, the most unfavourable SMR maps as well as the corresponding mean value have been established. From a cross analysis between these two maps and the instability phenomena observeddirectly in the field, we conclude that the average value of the SMR indexcalculated for the different discontinuity sets is the most representative valueof rock-slope-failure susceptibility. The results show the usefulness of theSMR's parameters to be used in GIS applications to rock-landslide hazardalong roads.

A Differential Interferometric SAR (DInSAR) analysis of terrain displacements in the province of Granada (southern Spain) is presented here for two different study zones. The first zone concerns the Guadalfeo River Basin, where abundant landslides and unstable slopes were previously identified and inventoried on a GIS application. However, no instrumental quantification of landslide activity was available. Considering morphological criteria and field observations, these deep-seated landslides were considered to be “dormant” or moving extremely slowly. The second study zone corresponds to the Granada metropolitan area, where no previous information was available on any vertical movement.The analysis was based on ERS1 and ERS2 images, covering the period from 1993 to 2000. By using DInSAR, we made an initial qualitative assessment of movements on landsliding slopes in the Guadalfeo River Basin and also vertical land movements in the alluvial Quaternary sediments to the west and south of the Granada metropolitan area. The terrain instability assessment resulting from this research shows maximum annual velocities along the SAR line of sight (LOS) of 6 mm/yr for the Tablones landslide, and up to 13 mm/yr for the Albuñuelas village; where progressive differential settlement processes were established as the origin of the movement.In the case of the Granada metropolitan area, two sites were detected with subsidence affecting two villages: Santa Fe, located in the western part of the area, with an estimated average velocity of 8 mm/yr and Otura in the south of the area, with maximum velocities of 12 mm/yr.A description of geological features of the different sites, showing LOS ground displacement, is presented with a discussion of the application of the rates to landslide-activity assessment found, local ground conditions, or exploitation of subterranean water in urban areas.

Because of the influence of carbonates on the geotechnical properties of foundation and construction materials in civil engineering, a simple, precise, and inexpensive method of determining soil-carbonate content is needed. A large number of methods exist to determine the carbonate content in soils; but, for diverse reasons (precision (accuracy), cost, sensitivity, etc.) not all are appropriate in a civil-engineering laboratory. In the present work, different laboratory methods to determine the carbonate content in soils have been compared in order to choose the most appropriate one. The most suitable method has been selected on the basis of a number of general criteria: precision (accuracy), equipment cost, operating and maintenance costs, staff requirements, and sensitivity of the equipment. According to these general criteria, three methods can be considered suitable: flame photometry, volumetric calcimeter, and EDTA complexometry. These three methods present errors of less than 5%, involve low to medium cost, and the maintenance operations are simple. In addition, a suitability index has been defined (depending on three specific criteria: degree of precision (accuracy), level of standardization, and suitability of the operation method and type of ion analysed) which enabled the selection of the most appropriate from among the three methods. For the study, marl samples were taken from quarries used to construct the impermeable cores of three dams in the upper Guadalquivir River Basin (S Spain), as well as Standard samples were made with pure and inert calcium carbonate. Finally, it is concluded that the volumetric method (Bernard calcimeter) is the overall best technique to determine the carbonate content in civil-engineering laboratories.

Landslide susceptibility is analysed in a semi-arid mountain environment, on the southern slope of Sierra Nevada. In a study area of 460 km2, 252 landslides were inventoried, affecting 3.2% of the total surface area. These landslides were mainly slides and flows on phyllite, schist and marble units in the Inner Zone of the Betic Cordillera. The most relevant determining factors proved to be elevation, slope angle, slope aspect and lithology. Triggering factors include mainly short-term landslide generation during heavy rainfall, as well as sporadic earthquakes or long-term activation by land-use changes, river over-excavation, etc. Although landslide susceptibility, assessed by the GIS matrix method, is predominantly low, some 15% of the study area shows moderate to very high susceptibility, coinciding with the sites of public works in the region. The map drawn was validated by the degree-of-fit method, registering values above 83.2% for the zones of high and very high susceptibility. La sensibilité aux glissements est analysée dans un environnement montagneux semi-aride, sur les versants sud de la Sierra Nevada. Sur un secteur d’étude de 460 km2, 252 glissements de terrain ont été répertoriés, affectant 3,2% de la surface totale du secteur étudié. Ces glissements de terrain étaient principalement des glissements et des coulées au sein d’unités de phyllites, de schistes et de marbres dans la zone interne de la cordillère bétique. Les facteurs de prédisposition les plus significatifs étaient l’altitude, la pente topographique, la morphologie des pentes et la lithologie. Les facteurs de déclenchement comportaient, pour la génération à court terme de glissements, les fortes pluies ainsi que des séismes sporadiques et, pour les générations sur le long terme, les modifications dans l’usage du sol, le surcreusement des rivières, etc. Bien que la sensibilité aux glissements, évaluée par une méthode matricielle basée sur un système SIG, soit principalement faible, environ 15% du secteur d’étude présente une sensibilité modérée à très forte, coïncidant avec les zones de travaux publics dans la région. La carte dessinée a été validée par une méthode de degré d’ajustement, enregistrant des valeurs supérieures à 83,2% pour les zones de forte à très forte sensibilité.

In this paper, ModelBuilderTM in ArcGIS (ESRI) has been applied to landslide-susceptibility analysis, mapping and validation. The models (scripts), available for direct downloading as an ArcGIS tool, allow landslide susceptibility to be computed in a given region, providing a landslide-susceptibility map, with the GIS matrix method, and ensuring a quality validation. The paper details the steps needed for the model-building process, enabling users to build their own models and to become more familiar with the tool. The susceptibility model leads the user first through a Digital Elevation Model (DEM), depicting the morphological and morphometric features of the study area, and then through a Digital Terrain Model (DTM), useful as a source of landslide-determinant factors, such as slope elevation, slope angle and slope aspect. In addition, another determinant factor is the lithological unit, independent of the DEM. Once the determinant landslide factors are reclassified and in a vectorial format, all the combinations between the classes of these factors are determined using the geoprocessing abilities of ArcGIS. The next step for the development of the landslide-susceptibility model consists of identifying the areas affected by a given surface of rupture (i.e. source area) in every combination of the determinant-factor classes. This step leads to the landslide matrix based on a previously georeferenced landslide database of the region, in which the slopes are distinguished into two simple classes: with or without landslides. In the last stage, to build a landslide-susceptibility model, the user computes the percentages of area affected by landslides in every combination of determinant factors. In the resulting landslide-susceptibility map a progressive zonation of areas or slopes increasingly prone to landslides is performed. A model for the validation of the resulting landslide-susceptibility map is also presented, based on the determination of the degree of fit, which is calculated from the cross tabulation between a set of landslides (not included in the susceptibility analysis) and the corresponding susceptibility map.

In this work we present the first results of an analysis applied to detection of landslides features using remote sensing techniques in rock masses at the Betic Cordilleras (southern Spain). After geometric and radiometric corrections, several techniques are used to facilitate a first visual approach to landslide identification, from enhancement and filtering (laplacian and textural) of panchromatic images, to colour compositions and fusions, vegetation index (NDVI) calculus and principal component analysis of multi-spectral imagery, corresponding to different sensors (Landsat ETM, Spot 5 and Ikonos). By means a GIS analysis, we compute basic statistics of whole images and pixels corresponding to different landslides typologies (rock falls, rock slides and debris flows) and in addition Kolmogorov-Smirnov coefficient to estimate the correlation between images and movements. In general terms, original panchromatic and multi-spectral bands present better correlations than processed images (filters, NDVI and PC bands), being the spectral signature different depending on landslides typology. Rock falls appear in darker zones of images while rock slides and especially debris flows appear in clearer zones. In this way, digital classification allows identify mobilized areas by typologies, but partially mixed with other land-uses such as soils, fresh rock and alluvial materials. The employment of textural filters (variance, mean euclidean distance and GLCM entropy) that present higher values in landslides zones permit the discrimination among landslides and other land-uses. The conclusion is the need of combining digital classification and textural analysis to identify landslide features or mobilized areas. * Corresponding author: Tomás Fernández ([email protected]) University of Jaén, Spain.

Geological Maps-is developing a guide to hazard maps. Scientists from 17 countries have participated. This paper is one of a series that presents the results of that work. It provides a general review of GIS landslide mapping techniques and basic concepts of landslide mapping. Three groups of maps are considered: maps of spatial incidence of landslides, maps of spatialtemporal incidence and forecasting of landslides and maps of assessment of the consequences of landslides. With the current era of powerful microcomputers and widespread use of GIS packages, large numbers of papers on the subject are becoming available, frequently founded on different basic concepts. In order to achieve a better understanding and comparison, the concepts proposed by Varnes (Landslide hazard zonation: a review of principles and practice, 1984) and Fell (Some landslide risk zoning schemes in use in Eastern Australua and their application 1992; Landslide risk assessment and acceptable risk. Can Geotech J 31: [261][262][263][264][265][266][267][268][269][270][271][272] 1994) are taken as references. It is hoped this will also add to the international usefulness of these maps as tools for landslide prevention and mitigation. Six hundred and sixty one papers and books related to the topic are included in the references, many of which are reviewed in the text.

Because of the influence of carbonates on the geotechnical properties of foundation and construction materials in civil engineering, a simple, precise, and inexpensive method of determining soil-carbonate content is needed. A large number of methods exist to determine the carbonate content in soils; but, for diverse reasons (precision (accuracy), cost, sensitivity, etc.) not all are appropriate in a civil-engineering laboratory. In the present work, different laboratory methods to determine the carbonate content in soils have been compared in order to choose the most appropriate one. The most suitable method has been selected on the basis of a number of general criteria: precision (accuracy), equipment cost, operating and maintenance costs, staff requirements, and sensitivity of the equipment. According to these general criteria, three methods can be considered suitable: flame photometry, volumetric calcimeter, and EDTA complexometry. These three methods present errors of less than 5%, involve low to medium cost, and the maintenance operations are simple. In addition, a suitability index has been defined (depending on three specific criteria: degree of precision (accuracy), level of standardization, and suitability of the operation method and type of ion analysed) which enabled the selection of the most appropriate from among the three methods. For the study, marl samples were taken from quarries used to construct the impermeable cores of three dams in the upper Guadalquivir River Basin (S Spain), as well as Standard samples were made with pure and inert calcium carbonate. Finally, it is concluded that the volumetric method (Bernard calcimeter) is the overall best technique to determine the carbonate content in civilengineering laboratories. D

In order to characterise the influence of the heavyrains on the observed landslides during the 1996–1997hydrological cycle, rainfall records for the last 100years are analysed from 104 stations in easternAndalusia. Regarding the amounts of rain recordedbetween ...

Forward logistic regression has allowed us to derive an earth-flow susceptibility model for the Tumarrano river basin, which was defined by modeling the statistical relationships between an archive of 760 events and a set of 20 predictors. For each landslide in the inventory, a landslide identification point (LIP) was automatically produced as corresponding to the highest point along the boundary of the landslide polygons, and unstable conditions were assigned to cells at a distance up to 8m. An equal number of stable cells (out of landslides) was then randomly extracted and appended to the LIPs to prepare the dataset for logistic regression. A model building strategy was applied to enlarge the area included in training the model and to verify the sensitivity of the regressed models with respect to the locations of the selected stable cells. A suite of 16 models was prepared by randomly extracting different unoverlapping stable cell subsets that have been appended to the unstable ones. Models were finally submitted to forward logistic regression and validated. The results showed satisfying and stable error rates (0.236 on average, with a standard deviation of 0.007) and areas under the receiver operating characteristic (ROC) curve (AUCs) (0.839 for training and 0.817 for test datasets) as well as factor selections (ranks and coefficients). As regards the predictors, steepness and large-profile and local-plan topographic curvatures were systematically selected. Clayey outcropping lithology, midslope drainage, local and midslope ridges, and canyon landforms were also very frequently (from eight to 15 times) included in the models by the forward selection procedures. The model-building strategy allowed us to produce a performing earth-flow susceptibility model, whose model fitting, prediction skill, and robustness were estimated on the basis of validation procedures, demonstrating the independence of the regressed model on the specific selection of the stable cells.

In this work a methodology for preparing landslides susceptibility and hazard maps is presented, based in a bivariate analysis between past movements and determinant factors. The methodology for determining the susceptibility is an adaptation of the matrix method to a GIS, and it has been tested and validated in different zones and environments of Andalusia (southern Spain). The text also discusses the availability of information layers in Spanish SDI to developing these susceptibility maps. For the hazard evaluation, we propose a methodology of determining the susceptibility in different return periods from inventories of landslides that show activity in these considered periods. The activity was estimated from stereoscopic and monoscopic analysis of aerial photographs from different