Book•
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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Dissertation•
01 Jan 2018
TL;DR: In this paper, the authors compared the results of analyses from PLAXIS or hand calculation with the DNV method with a good approximation for the failure path for moment loading in hand calculation and FEM results are expected to match.
Abstract: The ultimate bearing capacity is at its maximum when the foundation is under pure vertical loading. In the field, pure vertical loading is the least likely load combination to happen but, it is mostly combined loading condition applying on a foundation which causes a bearing capacity reduction. The offshore condition is where a structure faces more various load combination of vertical, horizontal and moment loads in different directions. This report determines the ultimate bearing capacity for different load combinations by using PLAXIS 3D which is a finite element(FE) software. Also, several hand calculations based on a method proposed by DNV is executed. The main idea of this thesis is to compare the results of analyses from PLAXIS or hand calculation. The foundation is a rectangular mudmat foundation. It has outer skirts embedded for one meter in the soil and no inner skirts are modelled. The soil is assumed as soft clay which has its shear strength increasing with depth. The foundation plates are set elastic and rigid, so it won't fail under loading. Knowing that the plates and soil have interactions, so the interfaces are fully bounded therefore there will be no gap between the plate and soil due to loads on it. The transiently uplifting loads could be resisted by negative pore pressure due to the gap and it might compromise the assumption of untrained condition assumed in this case study. The vertical bearing capacity of mudmat foundation resulted from PLAXIS 3D and hand calculation with the DNV method with a good approximation is the same. However, the horizontal bearing capacity differs slightly which seems to be due to the meshing system on PLAXIS which would lead to a more accurate answer if the mesh is finer. Also, assumption of roughness ratio as zero on hand calculation could be another reason. Second reason could be that PLAXIS 3D is modelling a three-dimensional environment while DNV method is based on a review through Hansen and Davis & Booker methods which are plane strain methods. Analysing the model on PLAXIS is time taking. Having a proper computer with high analysing properties is a must to work in 3D environment. Generally, the results from FE software are more accurate when it is generated by elements which are smaller in length but more in number. The assumption for hand calculation was not to have any tension loading though PLAXIS involves tension in the calculation. It is possible to use tension cut-off option on PLAXIS model as well. The model presented in this paper is having this condition to have comparable results. Hence, the failure path for moment loading in hand calculation and FEM results are expected to match. The results are closer when the moment is acting on the shorter edge than the longer one which is because of some forces on the 3D environment having influence on the results which are not seen in hand calculation. Further studies over torsional and cyclic loading is recommended.
6 citations
Cites background or methods from "Foundation analysis and design"
...To understand the different methods Bowles et al. (1996) is a good recourse....
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...To understand the different methods Bowles et al. (1996) is a good recourse. The Hansen (1970), Meyerhof (1953) and Davis et al....
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...To understand the different methods Bowles et al. (1996) is a good recourse. The Hansen (1970), Meyerhof (1953) and Davis et al. (1985) were the next papers to check. Reading through these methods helped to a better understanding DNV. (1992) method. Doing hand calculation was mostly based on this method. PLAXIS 3D is a software based on the finite element analysis (FEA). It provides a three-dimensional space to do modelling. PLAXIS has a big family of FEM software. The PLAXIS 3D Foundation version 2017 is what is used in this report to Work on bearing capacity on the mudmat foundation . To get to learn 3D modelling on PLAXIS, its manual reference by PLAXIS (2017) is reviewed and used. Offshore environment has many different loads. Loads on a structure could be a combination of vertical and horizontal loads with eccentricity in different directions causing moments. Cyclic loads are a plus. These loads have various resources and their nature differ. Therefore, load combination studies have been done many times such as Mana et al. (2012b); Dunne (2015);...
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...To understand the different methods Bowles et al. (1996) is a good recourse. The Hansen (1970), Meyerhof (1953) and Davis et al. (1985) were the next papers to check....
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...To check details about each factor reviewing Bowles et al. (1996) is recommended....
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01 May 2001
TL;DR: In 1996, the Colorado Department of Transportation (CDOT) completed the construction of a unique mechanically stabilized earth (MSE) wall with an independent full-height facing (IFF) for the ramp connecting northbound Interstate-25 to Interstate -70 in Denver, Colorado as discussed by the authors.
Abstract: In 1996, the Colorado Department of Transportation (CDOT) completed the construction of a unique mechanically stabilized earth (MSE) wall with an independent full-height facing (IFF) for the ramp connecting northbound Interstate-25 to Interstate -70 in Denver, Colorado. The new MSE/IFF wall has four major components: 1) a self-stable welded wire fabric (WWF) reinforced soil mass, 2) full-height concrete facing panels not attacked to the soil reinforcements (i.e., independent) that are allowed to tilt around their base, 3) flexible face anchors to provide for attachment of facing panels to the reinforced soil mass and accommodate movements of the wall system, and 4) a trench with flowfill to brace the panels during construction only (before the face anchors are placed). Since this MSE wall system is the first of its kind, it was considered experimental and a comprehensive instrumentation and monitoring program was performed. The main objective of this study was to upgrade the I-25/I-70 MSE/IFF wall for future standard use of this wall system by identifying modifications and additions to the design and construction of the I-25/I-70 MSE/IFF wall that would improve performance and save money and time. This report provides insight into material, construction, construction problems and corrective actions, monitoring, performance and design assessment of the I-25/I-70 MSE/IFF wall. The wall system performed as intended in the design. The flexibility of the MSE wall system smoothly accommodated the movements of the wall system, especially those induced by heavy compaction close to the facing, and allowed for the mobilization of tensile resistance in the WWF reinforcements, thus taking most of the lateral load off the facing panels. The average lateral earth pressure measured on the facing was a low value of 32 psf. After five years in service, the structure performance has been excellent with no signs of distress and the facing remained properly aligned.
6 citations
25 Mar 2014
TL;DR: In this article, a wind turbine generator (WTG) structure is typically supported by a large octagonal mass of reinforced concrete that, in turn, rests on the foundation soil.
Abstract: A wind turbine generator (WTG) structure is typically supported by a large octagonal mass of reinforced concrete that, in turn, rests on the foundation soil. The foundation soil must provide for adequate bearing capacity, rotational stiffness, and limit differential settlement. However, the pressure acting on the foundation soil varies temporally and spatially as a function of wind speed and direction and the soil properties. Field verification of dynamic responses and pressure distribution assumptions are highly relevant to establishing mechanistically correct WTG foundation behavior. Two WTG foundations in the Midwest have been instrumented, with emphasis on evaluating the dynamic forces and the soil response to in-service wind actions. According to field measurements, WTG foundation soil deformation and pressure distribution ranged from 0.0005 mm to 0.02 mm and 20 kPa to 110 kPa, respectively. The soil deformation profile and pressure distribution were not uniform and depend on depth below the foundation, offset from the centerline, and eccentricity of the dynamic load.
6 citations
TL;DR: In this article , a new technique is adopted to investigate the performance of replacement and geosynthetic reinforcement materials to improve the gypseous soil behavior through experimiential set up manufactured loaclally specially for this work.
Abstract: Existence of these soils, sometimes with high gypsum content, caused difficult problems to the buildings and strategic projects due to dissolution and leaching of gypsum by the action of waterflow through soil mass. In this research, a new technique is adopted to investigate the performance of replacement and geosynthetic reinforcement materials to improve the gypseous soil behavior through experimential set up manufactured loaclally specially for this work. A series of tests were carried out using steel container (600*600*500) mm. A square footing (100*100) mm was placed at the center of the top surface of the bed soil. The results showed that the most effective thickness for the dune sand layer with geotextile at the interface, within the tested range, was found to be almost equal to the width of foundation. Therefore, under this depth, the soil was reinforced with geogrid and geotextile. It can be shown that (Collapse Settlement Reduction Factor) increases to (72%) when using two layers of geogrid and one layer of geotextile under depth of replacement equal to the width of footing. In addition, the results showed that the bearing capacity increases to (1.5-2.0) time under concentric loads and (2.5-3) under eccentric loads after replacement and reinforcement of gypseous soil
6 citations
TL;DR: In this article, the authors used finite-difference code fast Lagrangian analysis of continua to evaluate the active earth pressure behind a retaining wall with one relief shelf placed at different levels with a variable width.
Abstract: Various studies of retaining walls with relief shelves tend to rely on the proposition of reducing soil pressures behind the wall, according to the location and the width of relief shelf. The previous numerical studies did not predict the optimum reduction rate of earth pressure and the shape of failure mechanism. The finite-difference code fast Lagrangian analysis of continua is used to evaluate the active earth pressure behind a retaining wall with one relief shelf placed at different levels with a variable width. The soil behind the wall is modelled by an elastoplastic constitutive model with a Mohr–Coulomb yield criterion. The effects of soil non-associativity as well as the interface of soil–wall and relief shelf–soil are investigated. The reduction of earth pressure is estimated by the rate R, defined as the ratio of the reduced active thrust to the total active thrust of a wall without a relief shelf. The rate R is evaluated numerically and by using Klein’s solution. The obtained results enable determination of the appropriate position and width of the relief shelf to evaluate the optimum values of R.
6 citations