• Geomechanics and Engineering
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• v.18 no.1
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• pp.29-39
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• 2019

In this paper, it was presented an investigation on the load-settlement and vertical stress analysis of the ring footings on the loose sand bed by conducting both laboratory model tests and numerical analyses. A total of twenty tests were conducted in geotechnical laboratory and numerical analyses of the test models were carried out using the finite element package Plaxis 3D to find the ultimate capacities of the ring footings. Moreover, the results obtained from both foregoing methods were compared with theoretical results given in the literature. The effects of the ring width on bearing capacity of the footings and vertical stresses along the depth were investigated. Consequently, the experimental observations are in a very good agreement with the numerical and theoretical results. The variation in the bearing capacity is little when $r_i/R_o$ <0.3. That means, when the ring width ratio, $r_i/R_o$, is equal to 0.3, this option can provide more economic solutions in the applications of the ring footings. Since, this corresponds to less concrete consumption in the ring footing design.

• Geomechanics and Engineering
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• v.30 no.1
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• pp.51-66
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• 2022

The article presents the results of finite element analyses carried out on skirted footings. The bearing capacity increases with the provision of the flexible and rigid skirt, but the effectiveness varies with various other factors. The skirts are more efficient in the case of cohesionless soils than cohesive and c-ϕ soils. Efficiency reduces with an increase in the soil strength and footing depth. The rigid skirt is relatively more efficient compared to the flexible skirt. In contrast, to the flexible skirt, the efficiency of the rigid skirt increases continuously with skirt length. The difference in the effectiveness of both skirts becomes more noticeable with an increase in the strength parameters, skirt length, and footing depth. The failure mechanism also changes significantly with the inclusion of a rigid skirt. The rigid skirt behaves as a solid embedded footing, and the failure mechanism becomes confined with an increase in the skirt length. Few small-scale laboratory tests were carried out to study the flexible and rigid skirt and verify the numerical study results. The numerical analysis results are further used to develop nonlinear equations to predict the enhancement in bearing capacity with the provision of the rigid and flexible skirts.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.5
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• pp.223-234
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• 1993

The main characteristics of PHC piles is that silica material and autoclave curing technique are used when manufacturing to have higher strength than PC piles. In this paper, pile drivability and bearing capacity characteristics of the PHC piles are studied through numerical analysis based on wave propagation theory, driving records and pile load tests in situ. It is found that we can have higher bearing capacity by using the PHC piles rather than the PC on condition that the most effective driving equipment is chosen when driving the pile. In other words, since the PHC piles have higher resistance to driving energy, the heavier ram can be used in the driving process, which results in the higher bearing capacity.

• Magazine of the Korean Society of Agricultural Engineers
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• v.30 no.1
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• pp.38-49
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• 1988

This paper presented as follows results of laboratory model tests with various shaped footings on soil bed reinforced with the strips on the base of behaviour of soil structure according to the loads and triaxial test results reinforced with geotextiles. Their parameters studied were the effects on the bearing capacity of a footing of the first layer of reinforcement, horizontal and vertical spacing of layers, number of layers, tensile strength of reinforcement and iclination load to the vertical 1.Depending on the strip arrangement, ultimate bearing capacity values could be more improved than urreinforced soil and the failure of soil was that the soil structure was transfered from the macrospace to microspase and its arrangement, from edge to edge to face to face. 2.The reinforcement was produced the reinforcing effects due to controlling the value of factor of one and permeable reinforcement was never a barrier of drainage condition. 3.Strength ratio was decreased as a linear shape according to increment of saturation degree of soil used even though at the lower strength ratio, the value of M-factor was rot influenced on the strength ratio but impermeable reinforcement decreased the strength of bearing capacity. 4.Ultimate bearing capacity under the plane-strain condition was appeared a little larger than triaxial or the other theoretical formulars and the circular footing more effective. 5.The maximum reinforcing effects were obtained at U I B=o.5, B / B=3 and N=3, when over that limit only acting as a anchor, and same strength of fabric appeared larger reinforcing effects compared to the thinner one. 6.As the LDR increased, more and more BCR occurred and there was appeared a block action below Z / B=O.5, but over the value, decrement of BCR was shown linear relation, and no effects above one. 7.The coefficient of the inclination was shown of minimum at the three layers of fabrics, but the value of H / B related to the ultimate load was decreased as increment of inclination degree, even though over the value of 4.5 there wasn't expected to the reinforcing effects As a consequence of the effects on load inclination, the degree of inclination of 15 per cent was decreased the bearing capacity of 70 per cent but irnproved the effects of 45 per cent through the insertion of geotextile.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5C
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• pp.343-350
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• 2006

The resistance bias factors for driven steel pipe piles are evaluated as a part of study to develop the LRFD(Load and Resistance Factor Design) for foundation structures in Korea. The 43 data sets of static load tests and soil property tests performed in the whole domestic area were collected and analyzed to determine the representative bearing capacities of the piles using various methods. Based on the statistical analysis of the data, the Davisson's criterion is proved to be the most reasonable method for estimation of pile bearing capacity among the methods used. The static bearing capacity formulas and the Meyerhof method using N values are applied to calculate the design bearing capacity of the piles. The resistance bias factors of the driven steel pipe piles are evaluated respectively as 0.98 and 1.46 by comparison of the bearing capacities for both of the static bearing capacity formulas and the Meyerhof method. It is also shown that uncertainty of the static bearing capacity formulas is relatively less than that of the Meyerhof method.

• Journal of the Korean Geotechnical Society
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• v.33 no.6
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• pp.17-25
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• 2017

In this research, post grouting methods were applied on PHC piles, and static load tests were conducted to confirm the effect of post grouting on bearing capacity enhancement of PHC piles. Grouting pressures of 1.9 MPa and 3.5 MPa were applied, and bearing capacities of grouted piles were compared with that of non-grouted pile. From the static load test results, the bearing capacities of grouted piles were about 3 times higher than that of non-grouted pile. In addition, the design efficiency (allowable bearing capacity/nominal bearing capacity) increased from 32% to 97% after post grouting, and the axial stiffness of piles also increased by about 1.3 times per grouting pressure.

• Journal of the Korean Geotechnical Society
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• v.20 no.3
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• pp.85-96
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• 2004

The ultimate bearing capacity of surface foundations on a sand layer overlying clay has been theoretically investigated. First, a review of previous studies on the bearing capacity problems for this type of foundation was performed and a discussion was presented concerning the practical application. Second, the kinematic approach of limit analysis was used to calculate the upper bound of the true ultimate bearing capacity. The kinematic solutions are upper bounds and their accuracy depends primarily on the nature of the assumed failure mechanism. This approach makes it convenient to create design charts, and it is possible to trace the influence of parameters. Third, the commercial finite element program ABAQUS was applied to obtain the ultimate bearing capacity based on the elasto-plastic theory. Results obtained from the kinematic approach were compared with those from the program ABAQUS and the limit equilibrium equations proposed by Yamaguchi, Meyerhof and Okamura et al. Finally, the validities of the results from the kinematic approach, the results from the program ABAQUS and the limit equilibrium equations were examined.

• Geomechanics and Engineering
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• v.20 no.1
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• pp.75-86
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• 2020

This study aims to simulate the stabilization process of fibrous peat samples using end-bearing Cement Deep Mixing (CDM) columns by three area improvement ratios of 13.1% (TS-2), 19.6% (TS-3) and 26.2% (TS-3). It also focuses on the determination of approximate stress distribution between CDM columns and untreated fibrous peat soil. First, fibrous peat samples were mechanically stabilized using CDM columns of different area improvement ratio. Further, the ultimate bearing capacity of a rectangular foundation rested on the stabilized peat was calculated in stress-controlled condition. Then, this process was simulated via a FEM-based model using Plaxis 3-D foundation and the numerical modelling results were compared with experimental findings. In the numerical modelling stage, the behaviour of fibrous peat was simulated based on hardening soil (HS) model and Mohr-Coulomb (MC) model, while embedded pile element was utilized for CDM columns. The results indicated that in case of untreated peat HS model could predict the behaviour of fibrous peat better than MC model. The comparison between experimental and numerical investigations showed that the stress distribution between soil (S) and CDM columns (C) were 81%C-19%S (TS-2), 83%C-17%S (TS-3) and 89%C-11%S (TS-4), respectively. This implies that when the area improvement ratio is increased, the share of the CDM columns from final load was increased. Finally, the calculated bearing capacity factors were compared with results on the account of empirical design methods.

• Journal of the Korean Geotechnical Society
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• v.40 no.2
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• pp.41-53
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• 2024

Micropiles are small, cast-in-place piles with a diameter of 300 mm or less, primarily used to reinforce existing structures and support new constructions. As the application of these piles has expanded, extensive research has been conducted on their bearing characteristics, particularly in micropiled rafts. These studies have consistently demonstrated the positive impact of micropiles on foundation reinforcement. However, previous research often overlooked the potential variations in behavior between micropiled and conventional piled rafts based on different pile conditions. Furthermore, the influence of the cohesive characteristics of the soil layer beneath the foundation on the reinforcing effect of the micropiles has not been adequately addressed. This study, therefore, undertook 3D numerical analysis to assess the reinforcing effect of micropiles, considering both pile conditions and the cohesive characteristics of the soil layer beneath the foundation. The findings revealed that micropiles are significantly more effective in non-cohesive soil layers compared to cohesive ones, with the potential to increase the bearing capacity of the raft by up to 3.7 times.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.30-37
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• 2009

In doing the foundation work in the downtown, the popular complaints by means of Noise and vibration have been became heavy burden. Therefore, the noise & vibration-free screw PHC pile method will contribute to the foundation work by removal of the popular complaints and improvement of the constructability. In this paper, the load bearing capacity and displacement characteristics of the noise & vibration-free screw PHC pile were analyzed. The noise & vibration-free screw PHC pile's behavior was better well than the existing PHC pile's one.