Resumo em Inglês:

Abstract This study presents the evaluation of the performance of grain silos reinforced by rigid inclusions in soils of the Central-West region of Brazil, during its construction and operation. Therefore, a group of eight silos with 32.4 m in diameter, 30 m in height, and 12,000 t of storage capacity (each silo) was numerically analyzed using the three-dimensional Finite Element Method (FEM, Plaxis 3D). The stratigraphy of the Experimental Field of the University of Brasilia, Brazil (CEGUnB) was considered in the analysis. The performance of using a system of rigid inclusions to reinforce the soil beneath the raft was compared with the behavior of an isolated raft. Two models were developed: in the first one, an independent silo was considered, its behavior was analyzed during its construction and operation stages by varying the length of the inclusions; in the second model, the group of eight silos was considered and their behavior was studied for different combinations of loading. The rigid inclusions system proved to be an efficient foundation solution that allows controlling total and differential displacements during the construction and serviceability stages of the silo, helping to prevent the formation of cracks in the structural elements and grain contamination by the excessive opening of the raft-perimeter beam structural joint.

Resumo em Inglês:

Abstract This study had the objective to evaluate the application of the Marchetti Dilatometer Test (DMT) on compacted residual soil, analyzing the influence of suction on the parameters obtained. For this, a sample of residual diabase soil was collected and compacted in the laboratory at its optimum moisture content. Granular matrix suction sensors (GMS) were installed inside the compacted sample to monitor the suction during the experiment. The GMS allowed the monitoring of suction profile variations during the drying of the specimen submitted to ambient conditions. The DMT blade was statically inserted at 6 different points of the specimen surface with measurement of parameters A and B at every 10 cm deep. It was observed that with the increase of suction, there is an increase in both: material index value (ID) and dilatometric module (ED), but a reduction in the horizontal stress index (KD) value. The increase in ED value and reduction in KD value indicates that there is an increase in deformability modulus (E) and a decrease in coefficient of at-rest earth pressure (K0). The DMT correctly detected the trend in variations in geotechnical parameters as a function of variation in soil suction profiles.

Resumo em Inglês:

Abstract The use of thin clayey soil as a liner plays an important role in many geotechnical and geo-environmental engineering applications, such as open channel and reservoir sealant, contaminant barrier etc. Their functional performance and sustainability depend primarily on the desiccation characteristics of these liners and barriers. A number of studies have been undertaken to quantify the degree of improvement achieved by using natural and synthetic fiber reinforcement. However, there is a lack of studies to understand the desiccation behavior of reinforced clay. This study aimed to explore the desiccation and cracking behavior of clayey soil reinforced with two natural fibers (coir and jute fiber) in addition to the degree of improvement in tensile strength. A series of direct tension and desiccation cracking tests have been conducted in the laboratory on clay-coir and clay-jute fiber mixes. The results demonstrate that when coir and jute fibers are used, the tensile strength of fiber-reinforced soil rises by up to 475 percent and 215 percent, respectively, when compared with the tensile strength of unreinforced soil at the same moisture content. Desiccation test results also show that blending of fibers reduces the breadth and depth of cracks significantly. The characteristics of unreinforced and fiber-reinforced clayey soil under desiccation and direct tension are briefly discussed in this paper. Findings of the present study will be important for professionals dealing with clay liners and trying to reduce cracking problems associated with drying soil.

Resumo em Inglês:

Abstract 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 constant terms. In this study, the electrical conductivity of the pore solution was obtained from a soil-cement leaching test after curing, and the conductivity of the monolithic soil-cement, by applying continuous voltage between 12-35 V onto electrodes of 1 mm thick copper plates. The influence of cement content and dry density on the electrical properties and water absorption was studied and discussed for curing times of 7 and 28 days. The samples molded with higher dry densities and cement contents presented higher Formation Factor for Soil Cement and higher unconfined compression strength. The Formation Factor and the unconfined compression strength are linearly related. Due to the methodology adopted, the Formation Factor was predominantly influenced by the conductivity of the pore solution and was related to the open porosity by means of a power function. Therefore, the Archie’s Law can be applied to soil-cement. In this case, the cementation coefficient varies until 28 days of curing, tending to stabilize around 8 from that age onwards. The volumetric coefficient can be adopted as a constant with a value of 1012.

Resumo em Inglês:

Abstract Engineering always deals with uncertainties, and efforts are needed to quantify them. A probabilistic analysis considers the statistical information of the problem to this quantification. In the geotechnical area, uncertainties play a particular role in structure design because it deals with naturally formed materials. Evaluating spatial variability has become progressively important. However, studies on the correct reproduction of this variability and conditional simulations are limited. In this paper, a geostatistical-based enhancement of the Random Finite Element Method (RFEM) is presented. The main aim of this study is to incorporate an advanced multivariate geostatistical technique (i.e., Turning Bands Co-simulation, TBCOSIM) to reproduce the coregionalization model of soil properties correctly in order to investigate the effects regarding this reproduction. It is illustrated in a real case of soil slope. The results showed that, for the unconditional simulation, the presented approach reached a perfect agreement with the coregionalization model, while the conditional simulation inserted some disturbances to this agreement, but it still satisfactorily reproduced the model. The original RFEM failed to reproduce this structure, leading to lower variances than the presented approach, which would cause a non-conservative design. Furthermore, disregarding the local uncertainty (i.e., the nugget effect) may introduce bias to analysis and, depending on its magnitude, may also lead the conditional analysis to not show a worthwhile reduction in variances of results. Finally, this paper shows that correctly determining the coregionalization model and reproducing it on probabilistic analysis may meaningfully influence the results.

Resumo em Inglês:

Abstract This work had as objective to carry out the construction of typical soil profiles of the main existing deposits in the city of Maceio from a database of SPT boreholes, built in GIS environment. In total, 1,686 records of drilling were specialized in sediments of the Barreiras Formation, Coastal Deposits, and lagoons-river, presenting the most frequent characteristics, exemplified through representative profiles. The Barreiras Formation, which covers about 75% of the urban area of the city, presented profiles with a predominance of clayey, without water level records. The deposits lagoons-river, located in the vicinity of Mundaú lagoon, were characterized by the significant presence of soft and organic clays, sometimes peat, it can reach large thicknesses and with the water table rising in certain regions. In the coastal plain, where the highest vertical construction indices in the city are concentrated, it presented an area with a predominance of fine to medium sand, with or without silt, and a water table varying between 1,00 m and 5,00 m. The analysis also allowed for the identification and mapping of the occurrence of limestone rock, sandstone rock, soft and organic clay rocks in the coastal plain, presenting a typical profile of their occurrence, helping to understand the geotechnical behavior of these materials in the studied region.

Resumo em Inglês:

Abstract This paper presents a numerical evaluation, using PLAXIS 2D finite element software, of the effects of varying the distance of the heavy compaction from the face in a geosynthetic reinforced soil wall (GRSW). The main effects studied were the tensions in the reinforcements and the horizontal deformations of the face, including the influence of the type of shear strength envelope (total stresses or effective stresses) of the soil. In this study, a young gneiss residual soil (silty sand) was studied to obtain the grain size distribution, index properties and parameters of strength and deformability. This soil was considered for backfill in hypothetical sections of GRSW. The numerical results contributed to a better understanding of the GRSW behaviour, with evaluations closer to real field conditions. In the analyses carried out, when increasing the heavy compaction distance from the face, there are tendencies pointing to the reduction of the tensions in the reinforcements, displacement toward the interior of the soil mass of the points at which the maximum reinforcement tension occurs and reduction of the horizontal deformations of the face.

Resumo em Inglês:

Abstract Transversal applications of 3D-printing (or Additive Manufacturing) have been recently implemented in the field of Geomechanics. In a 3D-printing process, the printed volume is obtained from successive layering of adjacent soil filaments. In this work, the fabric of an as-printed soil has been carried out by combining Mercury Intrusion Porosimetry (MIP) tests and Scanning Electron Microscope (SEM) observations, with the aim to highlight how the particle arrangements and the orientation and shape of pores are linked to the printing operation. The microstructural analyses showed that macropores are the result of the relative position of the filaments and their initial distortion in quasi-undrained conditions. Particle arrangement within the soil filament is strongly anisotropic, due to the rotative movement of the soil in the extruder.

Resumo em Inglês:

Abstract The seasonal variability of geotechnical parameters in the unsaturated zone is typically neglected in the design of geotechnical works. In most of the geotechnical projects the parameters are determined only for the saturated condition. Although it is known that this condition is the most critical to soil strength and deformability, this conservative approach may neglect a possible important contribution of the unsaturated condition, resulting in an increase in the cost of the geotechnical solution. This paper presents and discusses the site characterization of the active zone of an unsaturated sandy soil profile under different suction conditions. Laboratory tests with controlled suction (retention curves, triaxial compression with bender elements and oedometer tests) were carried out on undisturbed samples collected from 1.0 to 5.0 m depth. The results show that strength and deformability parameters are strongly affected by soil suction and are less influenced by confinement stress up to 5.0 m depth. All the investigated subsoil profile shows a collapsible behavior, more pronounced closer to the ground surface and under the effect of higher suction values. The findings highlight the importance of incorporating the suction influence in the site investigation, parameter determination, and geotechnical design for more economical, reliable, and environmentally sustainable solutions.

Resumo em Inglês:

Abstract This paper aims to analyze the behavior of a soil-nailed excavation located in Salvador, Bahia, Brazil. Numerical stress-strain modeling was conducted, using finite element method. The horizontal displacement profiles obtained for the wall face in the numerical analysis presented a good correlation compared to field instrumentation monitoring with inclinometers. The results showed that the magnitude of the maximum numerical and experimental displacements was lower than the simplified models recommended by international manuals and technical literature. However, the monitoring data was compatible with other cases of instrumented nailed excavations in silt-sandy soil in the city of Salvador. Numerical models also adequately represented the distribution of tensile forces in nails. The maximum tensile forces observed numerically were smaller than those calculated using analytical methods. It was emphasized that the results of field monitoring and numerical models correspond to a stage immediately after the end of the retaining structure execution, not considering the evolution of deformations in long term.

Resumo em Inglês:

Abstract The purpose of this article is to present predictive models of dilation and shear stress of rock discontinuities by applying the neuro-fuzzy technique, which uses a) the high capacity of artificial neural networks (ANN) to understand and to model complex multivariate phenomena, and b) the concepts of fuzzy sets theory to consider the variability of the input parameters in the proposed models’ responses. To develop the proposed models, experimental results were obtained from large-scale direct shear tests performed on different types of rock discontinuities and boundary conditions. The input variables of the proposed neuro-fuzzy models are the normal boundary stiffness, the ratio of fill thickness to asperity height, the initial normal stress, the joint roughness coefficient, the uniaxial compressive strength of the intact rock, the basic friction angle of the intact rock, the friction angle of the infill, and the shear displacement. The proposed models for dilation and shear stress provided results that fitted satisfactorily the experimental data, and the analyses of their performances indicated that they can represent the influence of the input variables on the shear behavior parameters of the rock discontinuities. The results from the neuro-fuzzy systems developed are also closer to the experimental data than those estimated by using traditional analytical methodologies existing in Rock Mechanics. This occurs because once considering the uncertainty of the input data, a more representative shear behavior prediction can be made by the neuro-fuzzy models.

Resumo em Inglês:

Abstract For predicting the size of rock fragments during drilling and blasting operations, this article uses GPR, RVM, and MPMR. The current analysis makes use of a blast data set generated in a prior investigation. In this study, a portion of the blast data was utilized to train a model to determine the mean particle size arising from blast fragmentation for each of the similarity groups generated. The particle size was modeled as a function of seven different variables. The dataset contains information about the bench height and drilled burden ratio (H/B), spacing to burden ratio (S/B), burden to hole diameter ratio (B/D), stemming to burden ratio (T/B), powder factor (Pf), modulus of elasticity (E), and in-situ block size (XB) are the input and output is X50. By comparing forecasts with actual mean particle size values and predictions based on one of the most widely used fragmentation estimation techniques in the blasted literature, the capacity of the generated models may be established. The statistical parameters, actual vs predicted curve, Taylor diagram, error bar, and developed discrepancy ratio are used to analysis the performance of models. A comparative study has been carried out between the developed RVM, GPR, and MPMR. The results show the developed models have the capability for prediction of X50. From these comparisons, the MPMR has the highest value with a high degree of precision and robustness in the size of rock fragments X50.

Resumo em Inglês:

Abstract This research aims to present a deterministic and probabilistic analysis of the stability in 2D/3D of a road slope, located in the state of São Paulo, Brazil, in the Serra Pelada region, incorporating scenarios with and without surface suction and water level, and predict the movement of the mobilized-mass volume. The results of the stability analysis showed the variability of the safety factor, the probability of failure, and the mobilized-mass volume, in the twenty-six simulated scenarios. The results of the runout analysis of the mobilized-mass volume indicated that any possible landslide would interdict, at least, two of the three lanes of traffic, equivalent to 59.7% of the lanes. Therefore, it can be concluded that a 2D and 3D stability analysis combined with the material point method to predict the post-failure soil displacement provides a better understanding of all processes involved in a landslide, which helps to establish more adequate and effective mitigation and remedial measures for each situation. Finally, in conclusion, the studied slope, with a maximum failure probability of 1.24%, is safe in terms of its overall stability for all twenty-six simulated scenarios.

Resumo em Inglês:

Abstract This work aims to analyze the behavior of a new post-grouted micropile setup developed in tropical soil. Its main innovation is the use of high mechanical resistance steel pipes (N80 class) for drilling and as a structural component of the micropiles. The pipes have special manchette valves uniformly spaced to allow neat cement grout injection into the soil. Two instrumented micropiles with 0.3 m diameter (after injection) and lengths of 19.4 m and 21 m were installed at Experimental Site III of the University of Campinas (Unicamp). The geological profile of this site presents a sandy clay surface layer (porous and collapsible) followed by a layer of sandy silt (diabase residual soil). The piles were subjected to compressive slow maintained loading tests and were instrumented along their depth with strain gages. No geotechnical failure was observed during the load test. The maximum load achieved by the MC1 and MC2 micropiles were 2.210 kN and 2.470 kN, respectively. The load test data were extrapolated to estimate the ultimate geotechnical pile capacity. The extrapolated geotechnical failure load was above 2.500 kN for both micropiles and similar to those estimated by the Federal Highway Administration FHWA (2005) load capacity method. It was verified that (1) the pile material undergoes creep under stress above 25 MPa on the transversal section of the pile and (2) the debonding effect during the loading process. The micropiles showed higher values of skin friction compared with other piles installed in the same geological-geotechnical context (tropical soil).