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Foundation analysis and design
01 Jan 1968-
TL;DR: In this paper, Fondation de soutenagement et al. presented a reference record for Dimensionnement Reference Record created on 2004-09-07, modified on 2016-08-08.
Abstract: Keywords: Fondation ; Mur de soutenement ; Pieux ; Capacite portante ; Ancrage ; Dimensionnement Reference Record created on 2004-09-07, modified on 2016-08-08
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01 Jan 2008
TL;DR: In this article, the authors studied the bearing behavior and failure mechanism of the geo-material under a footing foundation under such conditions, and they found that the bearing capacity of such foundations may be reduced because of the influence of the slope.
Abstract: Shallow footing located on/behind the crest of a slope is encountered frequently. To reduce the cost and to improve the performance of structure supports, structures are usually placed on the slope crest or at a setback distance from the slope crest. However, the bearing capacity of such foundations may be reduced because of the influence of the slope. The understanding of the bearing behavior and failure mechanism of the geo-material under a footing foundation under such conditions is essential. In general, the bearing-failure mode of a foundation on soil depends on soil compressibility and loading type. These types of failure mechanisms are essentially plastic in nature. On the other hand, the bearing-failure mode of a footing foundation on rock can be attributed to the discontinuities or the intact rock properties in a rock mass [1]. Landanyi [2] studied the punching failure of a nonporous brittle rock; he observed various fracturing stages as the bearing pressure approached the ultimate bearing capacity. These fracturing stages included initiation, growing, and finally coalesce forming, which resulted in the areas of crushed rock. Unlike foundations on soil, the feature of the failure mechanism of rock is essentially brittle. For many young and poorly cemented rocks, the function of lithification with particle cementation and perfect lock-up cannot be achieved due to short period of lithification age [3]. The poorly cemented rock commonly observed in the northern and western foothills of Taiwan is a typical example of this type of geo-material. It usually displays distinctive engineering characteristics including
3 citations
Journal Article•
TL;DR: In this article, a generalized formulation for the classical single-parameter Winkler's subgrade model is presented, where all the normal components of the stress tensor are taken into consideration, whereas the shear stresses are intentionally dropped with the purpose of providing a useful perspective, with which the Winkler model and its associated coefficient of subgrade reaction can be viewed.
Abstract: Based on an isotropic elastic continuum of thickness H overlying a rigid stratum, a generalized formulation for the classical single-parameter Winkler's subgrade model is presented. In this formulation, all the normal components of the stress tensor are taken into consideration, whereas the shear stresses are intentionally dropped with the purpose of providing a useful perspective, with which Winkler's model and its associated coefficient of subgrade reaction can be viewed. The formulation takes into account the variation of the elasticity modulus with depth. It only demands specifying a relationship between the vertical and horizontal normal stresses. Accordingly, two such different assumptions are made to obtain two new Winkler-type subgrade models with the corresponding closed-form relations for the subgrade modulus. The models give consistently larger stiffness for the Winkler springs as compared to previously proposed similar continuum-based models that ignore the lateral stresses. It has also been pointed out that it is only if the shear stress components of the subgrade are taken into consideration that a multi-parameter model evolves regardless of whether the lateral normal stresses are included. Finally, the effective stiffness per unit area of the multiple beds of springs of such a higher order model is exactly the same as the subgrade modulus of the corresponding single-parameter Winkler model presented in this work. Keywords: Heterogeneous subgrade, Reissner's simplified continuum, Shear interaction, Simplified continuum, Winkler model, Winkler-type models.
3 citations
TL;DR: In this paper, the authors make an effort to understand the damage of earthen dams under static and seismic loading condition. But, their work is limited to two-dimensional and three-dimensional finite element analysis under static loading conditions.
Abstract: Abstract The present study makes an effort to understand the damage of earthen dams under static and seismic loading condition. To make the investigation more realistic, behaviour of earthen dams considering the occurrence of a phreatic line indicating the submerged zone due to seepage within the dam body is considered. In case of earthen dams, homogeneous or nonhomogeneous, the consideration of the occurrence of a phreatic line or seepage line through the dam body is an important part of the earthen dam design methodology. The impervious material properties in the submerged zone below the phreatic line due to seepage may differ a lot in magnitudes as compared to the value of the same materials lying above this line. Hence, to have the exact stress distribution scenarios within the earthen dam, the different material properties above and below the phreatic line are considered in this present study. The study is first carried out by two-dimensional as well as three-dimensional finite element analysis under static loading condition. The work is further extended to observe the effect of seepage due to the consideration of the phreatic line on dynamic characteristics of earthen dams. Free vibration analysis and seismic analysis based on the Complete Quadratic Combination (CQC) method by considering twodimensional and three-dimensional modeling are carried out to present the frequencies, mode shapes and the stress distribution pattern of the earthen dam.
3 citations
01 Jan 2012
TL;DR: In this paper, the stability of a model soil slope, comprising of an embankment with two canal bunds at different stages of construction, was analyzed and results have been plotted in the form of variation of factor of safety with horizontal seismic acceleration coefficient (kh).
Abstract: The performance of soil slope during an earthquake is generally analyzed by three different approaches which are pseudo-static methods, Newmark's Sliding Block method and numerical techniques. In pseudo-static approach, the effects of an earthquake are represented by constant vertical (kv) and horizontal (kh) seismic acceleration coefficients and the factor of safety is evaluated by using limit equilibrium or limit analysis or finite element method of analysis. Newmark's sliding block method evaluates the expected displacement of slope subjected to any ground motion obtained from the integration of the equation of motion for a rigid block sliding in an inclined plane. Numerical methods determine the expected displacements obtained from the stress - strain relationship of a soil mass. In this paper the stability of a model soil slope, comprising of an embankment with two canal bunds at the top, at different stages of construction, i.e. only embankment, embankment with empty canal bunds and embankment with canal bunds filled with water, with different foundation soils in different seismic zones have been analyzed and results have been plotted in the form of variation of factor of safety with horizontal seismic acceleration coefficient (kh). The critical case has been further analyzed under dynamic conditions. Dynamic analyses have been carried out by plotting the response spectrum curve and selecting 2001 Bhuj earthquake motion as the typical ground motion.
3 citations
TL;DR: In this paper, critical threshold water pressures at which hydraulically induced fracturing of the FAS rock matrix may occur were determined for tensile and microfracture development failure modes.
Abstract: Potential for hydraulically induced fracturing of the Floridan Aquifer System (FAS) and the overlying Hawthorn Group deposit exists due to operation of seven potential aquifer storage and recovery facilities planned to be developed in south-central Florida to enhance Everglades restoration. The purpose of this study was to determine critical threshold water pressures at which hydraulically induced fracturing of the FAS rock matrix may occur. Several FAS rock matrix samples were collected, tested, and evaluated to define representative mechanical properties, which were then used in relation with in situ stresses to determine critical threshold water pressures. Three hydraulically induced fracturing failure mode evaluation methods based on shear, tensile, and microfracture development were utilized. Microfracture development requires the lowest critical threshold water pressure to induce fracturing, followed by tensile and then shear failure modes. Predictive critical threshold water pressures for tensile and microfracture development failure modes can potentially be achieved during full-scale operation of the planned aquifer storage and recovery facilities; therefore, appropriate design considerations and operational precautions should be taken to minimize water pressures that exceed this operational constraint. If hydraulically induced fractures are developed in the FAS, their propagation into the Hawthorn Group deposit would likely be arrested by or re-directed along the discontinuity zone at the contact of these two deposits. Additionally, the Hawthorn Group deposit exhibits a significantly lower modulus of elasticity than the FAS, which would tend to effectively arrest hydraulically induced fracture propagation.
3 citations