Abstract In the past two decades, Europe has witnessed a significant transition in the design codes used for assessing foundation structures, with the widespread adoption of the Eurocodes (EC). This ...shift remains a pertinent topic within the engineering community, particularly concerning the transition from traditional design methodologies to those prescribed by the Eurocodes, as well as the potential for fully probabilistic design. While the Eurocodes’ methodology is described as probabilistic, it is crucial to recognize that the achievement of the target reliability level is predominantly facilitated through a system of partial safety factors. These factors are integrated into the calculation algorithm as fixed values, rendering the process essentially deterministic. To refine these calculations for more accurate reliability estimates—expressed in terms of failure probability—a genuinely probabilistic framework is required, termed as fully probabilistic computation. This paper aims to elucidate the fully probabilistic calculation approach for the broader professional community, using the geotechnical application of shallow foundations as an illustrative example. We present a comparative analysis of this advanced approach with the standard foundation design according to EC7 and ČSN 731001, the latter being a precursor in Europe for implementing the partial safety factor method. The discussion extends to a practical demonstration of full probabilistic design juxtaposed against the conventional partial safety factor method, using a shallow foundation case study. Furthermore, the paper delves into the impact of the tail behavior of uncertain or spatially varying soil parameters on the theoretical probability of failure, underscoring its significance in foundation design.
The article is focused on the medium-term negative effect of groundwater on the underground grout elements. This is the physical-mechanical effect of groundwater, which is known as erosion. We ...conduct a laboratory verification of the erosional resistance of grout mixtures. A new test apparatus was designed and developed, since there is no standardized method for testing at present. An erosion stability test of grout mixtures and the technical solutions of the apparatus for the test's implementation are described. This apparatus was subsequently used for the experimental evaluation of the erosional stability of silicate grout mixtures. Grout mixtures with activated and non-activated bentonite are tested. The stabilizing effect of cellulose relative to erosion stability has been also investigated. The specimens of grout mixtures are exposed to flowing water stress for a certain period of time. The erosional stabilities of the grout mixtures are assessed on the basis of weight loss (WL) as a percentage of initial specimen weight. The lower the grout mixture weight loss, the higher its erosional stability and vice versa.
The reinforcement of soil is used to improve its strength and stiffness. The standard method of soil reinforcement is an application of geosynthetics. Soil reinforcement by distributed discrete ...fibres represents an alternative to those techniques. Currently used fibres have a straight shape, uniform cross-section, and smooth surface, which is not optimal in terms of the fibre-soil interaction. In this study, fibres with a variable shape were utilized. The fibres were fabricated using a fused deposition modelling technology. Firstly, a brief theoretical background is presented. Then, the proposed shapes of the fibres and their manufacturing process are described. The mechanical properties of the soil-fibre composite were investigated through consolidated drained triaxial tests. Well-graded coarse sand and poorly-graded fine sand were used. A higher peak shear strength was observed in the case of fibres with a variable shape. The effect of the variable shape of the fibres on the peak shear strength was higher in the case of the coarse sand.
A variety of engineering activities require reliable evaluation of rock strength. For instance, the stability of rock slopes depends on structural geology of rock massif in which the slope is ...excavated. Hoek-Brown (HB) failure criterion applied in rock design practice introduces factors based on the properties of jointed rock. The non-linear finite element safety calculation is conveniently used for calculation safety the factor of slope stability. The Mohr-Coulomb (MC) failure (strength) criterion for soil is widely applied in geotechnical design. Therefore, the appropriate transformation from HB to the equivalent MC, employing angle of shearing resistance φ and cohesion c, is necessary. This article studies the effect of jointed rock massif properties on the transformed MC parameters by using Sobol’s global sensitivity analysis (SSA) and HB transformation equations. Statistical parameters needed for the evaluation of sensitivity analysis are processed using classical statistical methods upon the emulation of Latin Hypercube Sampling simulation methods. Developed and adapted by authors techniques are illustrated by processing real rock investigation data from survey of the trachyte massif located in the Czech Republic. The first and higher order effects of random inputs are identified using SSA. It is illustrated that the effects of inputs on the MC parameters varies significantly depending on the discontinuity distribution and height of the slope.
The paper presents the use of advanced stochastic simulation techniques for estimating the strength behavior of rock materials. The Shore Rebound hardness was measured on fifty rock specimens coming ...from eleven different geological localities in Czech Republic. The dry unit weight of every tested rock material was determined also. Uniaxial compressive strength of rock was evaluated then by conducting the compression test on every specimen. Empirical distribution of Shore hardness and dry unit weight variables obtained from laboratory tests was approximated by the best fitted theoretical probability distribution. The stochastic simulation using Latin Hypercube Sampling was conducted based on those distributions. Two different equations used for estimating the compressive strength of rock on the basis of Shore hardness in practice was used as model functions. Comparison and statistical evaluation of uniaxial compressive strength of rock determined by compression test and those obtained as a result of stochastic simulation is discussed. The description of probability distribution of uniaxial strength is obtained as a result of introduced analysis, which can be used as input for fully probabilistic design models of rock materials.
Shape optimization in connection with numerical modelling is used to reduce bending and associated flexural stresses in buried concrete arches. Modelling of the arch is carried out via a nonlinear ...finite element model that accounts for soil constitutive relations, soil–structure interactions, sequential construction stages and soil compaction. Centre line of the arch is parameterized by Bézier curve with three degrees of freedom that are subjected to optimization by genetic and Levenberg–Marquardt algorithm.
The paper presents a parametric study which aims to determine the optimal shapes for buried arches of various span/rise ratios, backfill depths and foundation soil types. In the second part of the paper it shows a theoretical reduction in tensile stresses obtained by shape optimization of concrete arch culvert with a 9.4m span tested at the University of Massachusetts at Amherst.
The paper presents an application of statistical and numerical methods for the determination of the forcedisplacement
curves and that of pullout capacity of prestressed grouted ground anchors ...installed in Miocene clay. A regression
analysis of data from a database of acceptance test records for ground anchors to create has been performed, the
force-displacement curve of the tested anchor corresponding to the range of loads applied for acceptance tests has been
created. A linear regression model, employing the weighted least squares method and robust standard errors techniques
were concluded to serve as a reliable statistical method suitable for achieving this goal. The discovered linear regression
dependence then served as a lower control limit for the displacement values calculated at the anchor head applying the
numerical model. A finite element model has been created to predict the behaviour of ground anchors being installed in
fine-grained soils. The developed numerical model that employs Mohr-Coulomb strength criterion constitutive model
evaluates the influence of high-pressure grouting by development additional radial stresses and that of an increment of
fixed length diameter.
The paper briefly presents an advanced material model for shotcrete involving many aspects of the actual behavior of concrete. However, the contribution is focused on determination and calibration of ...selected input parameter values for practical use of the model in structural analysis. Two cross sections of different geological conditions were chosen from a utility tunnel in Brno in order to obtain sprayed concrete samples. The laboratory tests conducted are described and then compared with results from numerical approximations.
The main purpose of this paper is to analyse the influence of pressure grouting on ground anchors pull out capacity in fine grained soils, using the finite element method (FEM). The grouting process ...is simulated by volumetric strain of grout body, which is determined from excavated test anchors. Three constitutive models (Mohr-Coulomb, Hardening soil model and Hypoplasticity model for clay) are applied. Obtained pull-out capacities for the cases with respectively without grouting simulation are compared with the results of appropriate analytical and empirical methods. Cylindrical cavity expansion theories are also applied for the purpose of results evaluation. The influence of consolidation process after pressure grouting simulation and the value of volumetric strain are later analysed. It can be concluded that pressure grouting simulation has a substantial effect on the anchors pull-out capacity. Consolidation analysis following grouting simulation turned to be an important factor. Results from study, in which volumetric strains were varied, confirmed that the influence of grouting diminishes with increasing volumetric strain/grouting pressure.
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