• Geomechanics and Engineering
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• v.35 no.1
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• pp.41-54
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• 2023

The use of a skirt, a vertical projection attached to the footing, is a recently developed method to increase the bearing capacity of soils and reduce foundation settlements. Most of the studies were focused on vertical skirted circular footings resting on clay while neglecting the rigidity and inclination of skirts. This study employs finite element limit analysis to investigate the bearing capacity enhancement of flexible and rigid inclined skirts in cohesionless soils. The results indicate that the bearing capacity initially improves with an increase in the skirt inclination but subsequently decreases for both flexible and rigid skirts. However, the rigid skirt exhibits more apparent optimum skirt inclination and bearing capacity enhancement than the flexible one, owing to differences in their failure mechanisms. Furthermore, the bearing capacity of the inclined skirted foundation increases with the skirt length, footing depth, and internal friction angle of the soil. In the case of rigid skirts, the bearing capacity increases linearly with skirt length, while for flexible skirts, it reaches a stable value at a certain skirt length. The efficiency of the flexible footing reduces as the footing depth and soil internal friction angle increase. Conversely, the efficiency of the rigid skirt decreases only with an increase in the depth of the footing. The paper also presents a detailed analysis of various failure patterns, highlighting the behaviour of inclined skirted footings. Additionally, nonlinear regression equations are provided to quantify and predict the bearing capacity enhancement with the inclined skirts.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.376-387
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• 2009

Piled raft foundation is a geotechnical composite construction to support the superstructure by pile-soil-raft interaction. General conventional design for piled raft doesn't consider the contribution of a raft. This is very conservative and requires more piles to satisfy the factor of safety. It is important to evaluate the load sharing features of piled raft. In this research, this characteristics of piled raft evaluated using both centrifuge and numerical modelings. The ultimate bearing capacity of piled raft foundation was also evaluated and predicted through comparisons of ultimate bearing capacity of single pile (SP), unpiled raft (UR), freestanding pile group (FPG) and piled raft (PR). $\xi_{pr}$ and $\eta$ were determined by centrifuge model tests to simply evaluate the ultimate bearing capacity of piled raft and bearing capacity of piled raft was predicted using the calibrated numerical model based on the centrifuge tests and laboratory tests data.

• Geomechanics and Engineering
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• v.31 no.6
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• pp.599-614
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• 2022

One of the methods of stabilizing retaining walls, embankments, and deep excavations is the implementation of plate anchors (like the Geolock wall anchor systems). Back-to-back Mechanically Stabilized Earth (BBMSE) walls are common stabilized earth structures that can be used for bridge ramps. But so far, the analysis of the interactive behavior of two back-to-back anchored walls (BBAW) by double-plates anchors (constructed closely from each other and subjected to the limited-breadth vertical loading) including interference of their failure and sliding surfaces has not been the subject of comprehensive studies. Indeed, in this compound system, the interaction of sliding wedges of these two back-to-back walls considering the shear failure wedge of the foundation, significantly impresses on the foundation bearing capacity, adjacent walls displacements and deformations, and their stability. In this study, the effect of horizontal distance between two walls (W), breadth of loading plate (B), and position of vertical loading was investigated experimentally. In addition, the comparison of using single and equivalent double-plate anchors was evaluated. The loading plate bearing capacity and displacements, and deformations of BBAW were measured and the results are presented. To evaluate the shape, form, and how the critical failure surfaces of the soil behind the walls and beneath the foundation intersect with one another, the Particle Image Velocimetry (PIV) technique was applied. The experimental tests results showed that in this composite system (two adjacent-loaded BBAW) the effective distance of walls is about W = 2.5*H (H: height of walls) and the foundation effective breadth is about B = H, concerning foundation bearing capacity, walls horizontal displacements and their deformations. For more amounts of W and B, the foundation and walls can be designed and analyzed individually. Besides, in this compound system, the foundation bearing capacity is an exponential function of the System Geometry Variable (SGV) whereas walls displacements are a quadratic function of it. Finally, as an important achievement, doubling the plates of anchors can facilitate using concrete walls, which have limitations in tolerating curvature.

• Geotechnical Engineering
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• v.11 no.2
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• pp.51-70
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• 1995

Types of foundation of high rise buildings are primarily determined by loads transmitted from super structure, soil bearing capacity and available construction technology, The use of deep foundation of the buildings considered in this study due to the fact that rock of enough bearing capacity is not found down until 90~l00m. When a concentration of high soil pressure must be distributed over the entire building area, when small soft soil areas must be bridged, and when compressible strata are located at a shallow depth, mat foundation may be useful in order to have settlement and differential settlement of variable soils be minimized. The concept of mat foundation will also demonstrate some difficulties of applications if the load bearing demand directly carried down to the load -bearing strata exceeds the load -bearing capacity. This paper introduces both the analysis and design of mat type foundation for high rise buildings as well as the method-ology of modelling of the soil foundation, especially, engineered to redistribute the stress exceeding the soil bearing capacity. This process will result in the wide spread of stresses over the entire building foundation.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.1144-1154
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• 2008

In this paper, the behaviour of shell foundation was studied. In order to perform this study, three studies such as theoretical, numerical and experimental programs were performed. In the theoretical program, the general shallow foundation theories and failure mechanism developed by Terzaghi, Mayerhof and others were reviewed and compared. Based on the previous shallow foundation behaviour, the shell foundation theory was developed using the upper boundary theorem. In the numerical study, the 2 and 3 dimensional FEM simulations were carried out using an uncoupled-analysis approach. From the analysis results, the adequate depth of shell foundation was evaluated. It was also evaluated the bearing capacity according to the shell angle ($120^{\circ}$, $90^{\circ}$, $60^{\circ}$). In the experimental study, the laboratory model tests were carried out for five cases of different foundation shapes including the rectangular and circular foundation in order to verify the theoretical and nemerical study. According to the results of this study, the bearing capacity of shell foundation was theoretically about 15% larger than that of general foundation. However, in the model test, the bearing capacity of shell foundation was about 25 to 30% larger than that of general foundation. In the case of shell angle, the maximum bearing capacity of shell foundation shows when the shell angle of foundation was $60^{\circ}$. In addition, Even if the shell foundation has the various advantages compared with the general foundations as described above, the practical verifications in full scale size will be necessary to use in the field and will be helpful in the technical development of other special foundations.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.10a
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• pp.281-292
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• 2001

The evaluation of the allowable bearing capacity is the most important step in the design of a foundation. An accurate evaluation of the effect of all factors such as the physical properties of the soil located beneath the area, the size of the area, the depth of foundation, and the position of the water table is impracticable Therefore, the designer is compelled to estimate the allowable bearing capacity on the basis of simple semiempirical rules under cohesionless soils. This paper deals with semiemperical rules for determining allowable bearing capacity based on observed relations between the results of standard penetration test. Additional comparisions between the results of the theoretical methods and the emperical rules are performed to suggest more conservative design for the engineer.

• Journal of the Korean Geotechnical Society
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• v.31 no.7
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• pp.29-39
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• 2015

The vertical load imposed on the bucket foundation is transferred from the soil inside the bucket to the bottom of the foundation, and also to the outer surface of the skirt. For the design of a bucket foundation installed in sand, the vertical load transfer characteristics have to be clearly identified. However, the response of bucket foundations in sand subjected to a vertical load has not been investigated. In this study, we performed two-dimensional axisymmetric finite element analyses and investigated the vertical load transfer mechanism of bucket foundation installed in sand. The end bearing capacity of bucket foundation is shown to be larger than that of the shallow foundation, whereas the frictional resistance is smaller than that for a pile. The end bearing capacity of the bucket foundation is larger than the shallow foundation because the shear stress acting on the skirt pushes down and enlarges the failure surface. The skin friction is smaller than the pile because the settlement induces horizontal movement of the soil below the tip of the foundation and reduces the normal stress acting at the bottom part of the skirt. The calculated bearing capacity of the bucket foundation is larger than the sum of end bearing capacity of shallow foundation and skin friction of pile. This is because the increment of the end bearing capacity is larger than the reduction in the skin friction.

• Journal of Ocean Engineering and Technology
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• v.21 no.5
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• pp.25-32
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• 2007

The piled-raft foundation, a new design concept, is one of the most effective kinds of foundation for reducing settlement of structures. An alternative piled-raft system with disconnection cap and a sand cushion between the pile and raft was also investigated to compare the influence of ultimate bearing capacity and settlement. Load-settlement relation curves were used to evaluate the ultimate bearing capacity. In the numerical analyses, a plane strain elasto-plastic finite element model (Mohr-Coulomb model) was used to present the response of the piled-raft foundation.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.430-440
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• 2009

Top-Base Foundation(TBF) was developed in Japan as a factory made concrete product. It is actively used in 6,000 sites by the end of 1980s in Japan and applied for a domestic patent in 1985. It is a shallow foundation whose effectiveness is proven by many relevant researchers and engineers. TBF was introduced to Korea in 1991 and has been applied mainly to architectural structures to date. Currently, the effectiveness in bearing capacity and settlement of TBF is being underestimated for civil engineering structures. Characteristics of Top-Base Foundation studied in Japan and Korea is known as follows: (1) as concrete part and crushed stone behave together, they perform the function of rigid mat; (2) the conical part and pile part of TBF disperses load by interaction with the crushed stone; (3) by preventing lateral strain and differential settlement on lower ground, it improves bearing capacity and constrains settlement at the same time. In Korea, it is used mostly in clayey soft grounds. The formula of bearing capacity and settlement of TBF suggested in Japan give the values of the underestimated. bearing capacity while its settlement is overestimated in comparison with the values measured from the field loading test. Therefore, in this study, the stress delivery mechanism of Top-Base Foundation developed in Japan and Floating Top Base developed in Korea is investigated through numerical analysis and laboratory model test.

• Geotechnical Engineering
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• v.13 no.3
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• pp.77-86
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• 1997

Laboratory model test results for the ultimate bearing capacity of a surface strip foundation supported by a near-saturated clayey soil reinforced with layers of geogrid have been presented. The optimum values for the width of the reinforcement layers, the depth of reinforcement, and the location of the first layer of geogrid for mobilization of maximum bearing capacity have been determined. Based on the model test results, an empirical procedure to estimate the ultimate bearing capacity has been developed.