Embankment construction projects on very soft soil often give rise to serious problems. This volume on geotechnics and soft soil engineering therefore treats all phases of the design and construction ...process exhaustively, from the first investigation step to the monitoring of constructed work. The book presents the development concepts necessary for the project stages and discusses in great detail construction methods, displacement estimations, stability analyses, monitoring, and various other aspects involved. Extensive attention is furthermore paid to the application of geosynthetics as a tool to improve the stability of soft soils and embankments. Including various tables and practical data for many geographical areas in the world, this reference volume is essential reading for engineers and researchers in geotechnical engineering, construction, and related disciplines.
AbstractThis article presents mass stabilization studies performed on very soft organic clay, with very high water content, very low pH value, and high clay activity, treated with high early strength ...dry portland cement. The specimens were prepared in a laboratory with differing cement contents and subjected to unconfined compression tests under different preloading conditions and curing times. Undisturbed samples of the mass stabilized soil were collected in situ and subjected to unconfined compression tests. The results showed that the preloading during the curing period and the amount of cement directly influenced the strength and the secant modulus of the organic clay stabilized in the laboratory, reducing the porosity of the specific blends studied. The strength measured in the laboratory specimens was about twice as high as the strength measured in the field specimens, which, in turn, was about five times higher than the strength of unstabilized soil. Finally, it can be concluded that for the highly organic clay and cement blend conditions studied in this paper, the porosity controls the mechanical properties of the blends.
Embankment construction projects on very soft soil often give rise to serious problems. This volume on geotechnics and soft soil engineering therefore treats all phases of the design and construction ...process exhaustively, from the first investigation step to the monitoring of constructed work. The book presents the development concepts necessary for the project stages and discusses in great detail construction methods, displacement estimations, stability analyses, monitoring, and various other aspects involved. Extensive attention is furthermore paid to the application of geosynthetics as a tool to improve the stability of soft soils and embankments. Including various tables and practical data for many geographical areas in the world, this reference volume is essential reading for engineers and researchers in geotechnical engineering, construction, and related disciplines.
Centrifuge Modeling of the Seismic Behavior of Soft Clay Slopes Soriano Camelo, Cristian Yair; de Almeida, Maria Cascão Ferreira; de Almeida, Marcio de Souza Soares ...
Journal of geotechnical and geoenvironmental engineering,
11/2022, Volume:
148, Issue:
11
Journal Article
Peer reviewed
Open access
AbstractThis paper presents the experimental results and analysis from two centrifuge experiments that simulated the seismic response of a gentle slope in soft clay. The two models consisted of a ...three-degree and a six-degree slope in soft clay, respectively, which are representative of typical slopes found on marine seabeds on the continental margins. The models were built in a laminar container in order to reproduce infinite slope boundary conditions. In-flight characterization investigations consisting of T-bar tests and air hammer tests were performed to obtain undrained shear strength profiles and shear wave velocities at various depths, respectively. A suite of earthquakes was applied, including sinusoidal waves and scaled real motions, in order to observe the response of the models in terms of the propagation of shear waves and the generation of lateral displacements at various depths in the slopes. The results showed that the model preparation approach ensures the repeatability of the experiments, enabling the evaluation of the impact of the slope angle on the seismic response of the gentle slopes studied. On average, the permanent displacements measured at the surface of the six-degree slope were three times greater than those measured at the top of the three-degree slope. In these slopes, nonlinear effects were observed in terms of the peak ground acceleration (PGA) that depended both on the slope angle and the intensity of shaking.
Risk stratification in secondary prevention has emerged as an unmet clinical need in order to mitigate the Number-Needed-to-Treat and make expensive therapies both clinically relevant and ...cost-effective. P wave indices reflect atrial conduction, which is a sensitive marker for inflammatory, metabolic, and pressure overload myocardial cell remodeling; the three stimuli are traditional mechanisms for adverse clinical evolution. Accordingly, we sought to investigate the predictive role of P-wave indices to estimate residual risk in patients with chronic coronary artery disease (CAD). The cohort included 520 post-Coronary Artery Bypass Grafting patients with a median age of 60 years who were followed for a median period of 1025 days. The primary endpoint was long-term all-cause death. Cubic spline model demonstrated a linear association between P-wave duration and incidence rate of long-term all-cause death (p = 0.023). P-wave >110ms was a marker for an average of 425 days shorter survival as compared with P-wave under 80ms (Logrank p = 0.020). The Cox stepwise regression models retained P-wave duration as independent marker (HR:1.37; 95%CI:1.05-1.79,p = 0.023). In conclusion, the present study suggests that P-wave measurement may constitute a simple, inexpensive and accessible prognostic tool to be added in the bedside risk estimation in CAD patients.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Understanding the dynamic behavior of soils is essential to the study of the influence of seismic loads on the instability of submarine slopes, an important issue in Brazil and other countries. The ...shear modulus and the damping ratio are two fundamental parameters for the study of this behavior. Determining these parameters for Speswhite kaolin clay is the object of the present study using resonant column tests and dynamic centrifuge tests with accelerometers and pairs of bender elements. The curves obtained in the laboratory are compared with empirical curves and comparable data in the literature. Good agreement was observed between experimental data and the empirical prediction for the degradation curve of the normalized shear modulus. The damping curve for very low strains, obtained with resonant column tests, was consistent with the empirical curve. However, consistent with a trend observed in the literature, the centrifuge test results presented considerable scatter (dispersion), attributable to the difficulty in modelling damping dissipation mechanisms in the centrifuge.
Although seismic activity in Brazil is low to moderate, some earthquakes with damage potential occurred in the past. Engineering structures located along the coast and those installed in deep waters ...need to comply with safety requirements. In addition, there is a need to address the public interest regarding the effects of seismically-induced landslides. Therefore, a probabilistic seismic hazard assessment was carried out for the offshore south/southeast regions of Brazil, in order to estimate potential levels of ground motion. A historical and recent instrumental seismicity catalog for this region has been compiled. A stochastic attenuation relation with different seismic source models and recurrence parameters was used in a hazard analysis with the CRISIS 2012 software. To capture the epistemic and aleatoric uncertainties in the hazard calculations, a logic tree approach was adopted, considering different seismic zone models, seismic activity parameters, and scaling factors in the Ground Motion Prediction Equation. It was verified that the Peak Ground Accelerations are mostly less than 2.0% g in the continental portion of the region (for 10% exceedance probability in 50 years). At a particular point of interest located offshore in the continental slope of the study area, the seismic hazard is also low, with the maximum acceleration for the probability of exceedance of 10% and 2% in 50 years reaching mean values of 3.2% and 19.1% g, respectively, for very hard rock conditions.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This chapter describes the geotechnical properties of very soft clays illustrated by the
case Sarapuí clay in Rio de Janeiro, probably the best studied soft clay deposit in
Brazil (Almeida and ...Marques, 2003). The overall elasto-plastic behavior of soft clays
is previously presented for background reference.
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