Lázaro Valentin Zuquette

Analysis of cyclic swelling of mudrocks

Mudrocks are very common rocks that when in contact with water can present considerable volume change and breakdown. The many factors interacting in the swelling phenomenon complicated the approach required to carry out the present work, which focuses on the impact of cyclic wetting and drying on swelling behavior of mudrocks. The samples studied are Cretaceous Age mudrocks (Terres Noires) from the French Alps, Toarcien mudrocks from the Banassac area (south of France), and Tertiary Age mudrocks from the French Central Massif (Marnes of Limagne). Analyses of grain-size distribution, mineralogical composition, pore-size distribution, and cation-exchange capacity were made. Scanning electron microscopy (SEM) registered the condition of samples before and after free and pressure swelling tests. The results showed the importance of rock texture and structure in addition to mineralogical composition. Cyclic wetting and drying of the samples demonstrated the different mudrock behaviors that could be determined with the coefficient proposed in this work.

Engineering geological mapping developed in the Fortaleza Metropolitan Region, State of Ceara, Brazil

Abstract Engineering geological mapping was carried out, at a scale of 1:100,000, in the Fortaleza Metropolitan Region, located in northeastern Brazil, to provide engineering geological information as an aid in planning land use and occupation. In this study, eight basic maps were produced drawing: urban areas, lithology, unconsolidated materials in addition to geomorphological map showing slopes, water resources, engineering geological zoning and distribution of geological–geotechnical environmental problems based on information collected through field and laboratory investigations. The region was divided into nine engineering geological zones analyzed in terms of geohazard susceptibility and foundation, excavation and waste disposal conditions.

Piezometric variations in the basaltic massif beneath the Itaipu hydroelectric plant (Brazil/Paraguay border): Right Buttress Dam

This article describes a case study of the changes in the hydrogeotechnical behavior of a portion of the foundation block of the Itaipu Dam, which is located on the Parana River on the border between Brazil and Paraguay. The study focuses on the foundation buttress blocks of the Right Buttress Dam, where the most permeable regions of the massif are monitored by standpipe piezometers. The behaviors of two features within the basalt layers, a basaltic breccia and a fracture, were evaluated. In general, the uplift pressure distribution models of the foundations of concrete dams only consider the hydraulic loads caused by the presence of the reservoir and the tailwater elevation. However, this study demonstrates that the hydrogeotechnical behavior of the massif in a given period may also depend on the local variation in rainfall. The primary conclusion is that although the rocky massif has received several foundation treatments (waterproofing and drainage work), the natural hydraulic conditions of the massif govern the pressure variations within the monitored features. Studying the behavior of these features is of fundamental importance to all large concrete dams, as a statistical analysis of ruptures in several types of dams conducted by the International Commission on Large Dams has demonstrated that accidents involving this type of dam are primarily caused by foundation collapse, particularly by collapses related to internal erosion problems and low shear resistance.

Erosion feature reclamation in urban areas: typical unsuccessful examples from Brazil

Erosion is responsible for environmental degradation in continental and coastal areas with varying degrees of intensity and spatial range. In continental areas, rills and gullies affect urban and non-urban areas and may occur isolated or in groups. In urban areas, many forms of degradation occur, ranging from relief modifications (with runoff and other hydrological changes) to channel and reservoir silting. Other forms of degradation include the destruction of infrastructure items, such as streets, power lines and pipelines. Many mechanical, structural, agricultural, ecological and bioengineering measures can be adopted to control and restore these areas, with various results. In many cases, the applied techniques are unsuccessful and worsen the environmental problems. To illustrate such cases in Brazil, this study examines the adoption of different techniques to restore gullies in the cities of São Pedro, Franca, São Carlos, Casa Branca and Cajuru, in the state of São Paulo. These areas are characterized by sandy geology in a variety of landscapes, and the erosion processes result from natural and anthropogenic conditions. Additionally, Brazil’s coastal area has been affected by erosion, as in Fortaleza (in the state of Ceará). This study demonstrates that the primary factor associated with erosion in coastal and continental urban areas is the lack of territorial planning that considers the geological, hydrological and geotechnical limitations. In some of the studied areas, positive results have been achieved. However, unsatisfactory results predominate primarily because appropriate geological, environmental and geotechnical studies were not performed before the interventions were selected and implemented.

Aspectos de sorção para os materiais inconsolidados da região de São Carlos (SP), Brasil

The transport of liquid and gaseous pollutants through porous geological media depends on the physical and chemical characteristics of the unconsolidated material, rocks and water, associated with the characteristics of the pollutants. Of these characteristics, the sorption aspect is of fundamental importance and is a function of the mineral proportions, pH, Eh and void aspects encountered in the porous media. In the Sao Carlos region, located in the eastern-central part of the State of Sao Paulo, Brazil, there are basically two types of unconsolidated materials: the first is a residual from sandstones cemented with fines and the secondarily composed of claystones, siltstones and conglomerates from the Cretaceous Period that constitute the Itaqueri Formation; the second is a sandy sediment of the Tertiary Period. These geological conditions are found in areas where chemical products are disposed of, characterized as either diffuse or point pollutions sources. Because of this situation, a study was developed to evaluate the sorption aspects of some inorganic cations that are frequently found in these sources, in varied concentrations. Taken into consideration were their physical/chemical properties, such as: specific weight, grain size, mineralogy, cationic exchange capacity, pH, hydraulic conductivity. Batch tests were run using solutions of KCl, ZnCl2 and CuCl.H2O at three different pH values, and then with a combined solution (KCl + ZnCl2 + CuCl.H2O), also at three different pH values.

Evaluation of weathering of basaltic lithotypes based on pH, electrical conductivity, and point-load strength tests

This paper presents the results of an evaluation of the weathering of different basaltic lithotypes (dense basalts, vesicular-amygdaloidal basalts, and basaltic breccias) from four basaltic flows of the Serra Geral Formation of the Itaipu Dam region. Samples were classified according to their degree of weathering based on analysis with a 200X digital microscope and were subjected to pH, electrical conductivity, and point-load strength tests. The results show that pH and electrical conductivity values are effective for the evaluation of weathering, especially when tactile-visual classification does not provide an accurate evaluation of the rocks different degrees of weathering.

Avaliação da condutividade hidráulica em área de recarga do aqüífero Botucatu

This work shows the results of the hydraulic conductivity from infiltration tests developed in the Vacununga watershed, in the region of Luis Antonio, northeastern portion of the state of Sao Paulo. This basin is constituted of sandstones of Botucatu Formation (more than 90%) and Sandy residual unconsolidated materials (unconfined aquifer Botucatu) that were responsible for the selection of this watershed for this study. The soil properties and its hydraulic conductivity were obtained by laboratory and field tests (double ring). Results showed that the water movement is significantly affected by the land uses and management practices, although the region presents geological homogeneity.

How to Perform Hydraulic Conductivity Upscaling in the Daily Practice of Geotechnical Modeler

Although important for many geotechnical issues, hydraulic conductivity heterogeneity is rarely considered in geotechnical practice for two main issues. First, it is almost impossible to sample the entire area of interest. Second, it is very difficult to account for scale effects in our numerical models. In this paper, we divulgated an important result obtained in a previous work [1], where those two problems were faced. An innovative approach in geotechnics based on simple averaging process is showed. That approach incorporates spatial variability, multiscale data, and uncertainty treatment into a workflow that could be implemented in the daily practice of geotechnical engineers in order to perform hydraulic conductivity upscaling. The approach described allows a practical and reliable hydraulic conductivity upscaling for the studied soil, proving itself as a good solution for the daily practice of the geotechnical modeler.

Stochastic upscaling of hydrodynamic dispersion and retardation factor in a physically and chemically heterogeneous tropical soil

Stochastic upscaling of flow and reactive solute transport in a tropical soil is performed using real data collected in the laboratory. Upscaling of hydraulic conductivity, longitudinal hydrodynamic dispersion, and retardation factor were done using three different approaches of varying complexity. How uncertainty propagates after upscaling was also studied. The results show that upscaling must be taken into account if a good reproduction of the flow and transport behavior of a given soil is to be attained when modeled at larger than laboratory scales. The results also show that arrival time uncertainty was well reproduced after solute transport upscaling. This work represents a first demonstration of flow and reactive transport upscaling in a soil based on laboratory data. It also shows how simple upscaling methods can be incorporated into daily modeling practice using commercial flow and transport codes.

Mapping groundwater pollution vulnerability with application in a basin in southern Brazil

This study presents the criteria and conditions that supported the development of a proposed vulnerability index and its application in the Córrego do Ribeirão do Feijão Basin, which is located in the central portion of the state of São Paulo, southeastern Brazil. This basin was selected, because it is representative of very large areas in the south, west, and southeast regions of Brazil, is the main source of freshwater for the municipality of São Carlos, and has been undergoing accelerated changes due to diversified anthropogenic activities, thus increasing the number of contaminant sources. The proposed index is based on a hierarchy of information that includes a total of 46 attributes categorized into groups (4 rainfall attributes, 6 point contaminant sources, 5 non-point contaminant sources, 5 unconsolidated material 1, 4 unconsolidated material 2, 4 rock substrate 1, 4 rock substrate 2, 1 relief, 6 unconsolidated material 3, 4 rock substrate 3, and 3 groundwater), which were obtained from principles and procedures of engineering geological mapping and laboratory tests. The final vulnerability index for each land unit was obtained as a percentage using the total vulnerability index, which is the sum of the partial indices (these indices are normalized eigenvectors of the unit) and the maximum value that a unit can reach, considering the classes of maximum influence in vulnerability. The basin was divided into 29 categories controlled by engineering geological units and types of land uses, resulting in 94 land units, of which 17 were classified as Class 1, with the highest vulnerability; 41, 23, and 13 were classified as Classes 2, 3, and 4, respectively, with decreasing degrees of vulnerability. The results verify that the proposed index enables an adequate subdivision of the region and classification of the units, respecting the natural variability and the anthropogenic aspects. The attributes associated with land units and the datasheet used for data treatment permit a dynamic vulnerability analysis, because it is easier to identify and characterize the anthropogenic changes (mainly related to contaminant sources) per land unit in situ and to obtain new results that will require new control or planning measures.