• Geomechanics and Engineering
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• v.37 no.5
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• pp.511-525
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• 2024

Micropiled raft has been used to support the existing and new structures or to provide the seismic reinforcement of foundation systems. Recently, research on micropile or micropiled raft has been actively conducted as the usage of micropile has increased, and the reinforcement effect of pile for the raft, the pile installation methods, and methods for calculating the bearing capacity of micropiled raft have been proposed. In addition, existing research results show that the behavior of this foundation system is different depending on the pile conditions and can be greatly influenced by the characteristics of the upper or lower ground depending on the conditions of pile. In other words, considering that the micropile is a friction pile, it can be predicted that the reinforcing effect of micropile for the raft and the bearing capacity of micropiled raft may depend on the cohesion of upper soil layer depending on the pile conditions. However, existing studies have limitations in that they were conducted without taking this into account. However, existing studies have limitations as they have been conducted without considering these characteristics. Accordingly, this study investigated the reinforcing effect of micropile and the bearing characteristics of micropiled raft by varying the cohesion of upper soil layer and the stiffness of pile which affect the behavior of micropiled raft. In this results, the reinforcing effect of micropile on the raft also increased as the cohesion of soil layer increased, but the reinforcing effect of pile was more effective in ground conditions with decreased the cohesion. In addition, the relationship between the axial stiffness of micropile and the bearing capacity of micropiled raft was found to be a logarithmic linear relationship. It was found that the reinforcing effect of micropile can increase the bearing capacity of raft by 1.33~ 3.72 times depending on the cohesion of soil layer and the rigidity of pile.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.11-19
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• 2004

When pile foundation constructed by driving method, it is desirable to perform monitoring and estimation of pile drivability and bearing capacity using some suitable tools. Dynamic Pile Monitoring yields information regarding the hammer, driving system, and pile and soil behaviour that can be used to confirm the assumptions of wave equation analysis. Dynamic Pile Monitoring is performed with the Pile Driving Analyser. The Pile Driving Analyser (PDA) uses wave propagation theory to compute numerous variables that fully describe the condition of the hammer-pile-soil system in real time, following each hammer impact. This approach allows immediate field verification of hammer performance, driving efficiency, and an estimate of pile capacity. The PDA has been used widely as a most effective control method of pile installations. A set of PDA test was performed at the site of Donghea-1 Gas Platform Jacket which is located east of Ulsan. The drilling core sediments of location of jacket subsoil are composed of mud and sand, silt. In this case study, the results of PDA test which was applied to measurement and estimation of large diameter open ended steel pipe pile driven by underwater hydraulic hammer, MHU-800S, at the marine sediments were summarized.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.06a
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• pp.11-29
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• 2002

Current design of pile group is based on the estimation of the overall bearing capacity of a pile group from that of a single pile using a group efficiency. However, the behaviors of a pile group are influenced by various factors such as method of pile installation, pile-soil-pile interaction, cap-soil-pile interaction, etc. Thus it is practically impossible to take into account these factors reasonably with the only group efficiency, In this paper, a new method for the design of pile groups is proposed, where the significant factors affecting the behavior of a pile group are considered separately by adopting several efficiencies. Furthermore, in the proposed method, the load transfer characteristics of piles and the difference of pile behaviors with respect to the pile locations in group can be taken into account. The efficiencies for the method are determined using the settlement failure criterion, which is consistent with the concept of allowable settlement for structures. The efficiencies calculated from the results of existing model tests are presented, and the bearing capacity of a pile group in the other model test is calculated and compared with that from the test result, to verify the validity of the proposed method.

• Geomechanics and Engineering
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• v.16 no.6
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• pp.589-597
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• 2018

Centrifuge model tests were used to simulate pile-raft composite foundation and pile-geogrid composite foundation with different pile spacing for researching the time effect of negative skin friction of rigid piles in high-speed railways. The research results show that the negative skin friction has a significant impact on the bearing capacity of composite foundation. Pile-raft composite foundation has higher bearing capacity compared to pile-geogrid composite foundation to reduce the effect of negative skin friction on piles. Both the foundation settlement and negative skin friction have significant time effect. The distribution of skin friction can be simplified as a triangle along the pile. The neutral point position moves deeper in the postconstruction stage at larger pile spacing. For pile-geogrid composite foundation, the setting of pile-cap affects the position of neutral point in the post-construction stage. Reinforced cushion with geotextile may promote the better performance of cushion for transmitting the loads to piles and surrounding soils. Arching effect in the cushion of the composite foundation is a progressive process. The compression of the rigid piles contributes less than 20% to 25% of the total settlement while the penetration of the piles and the compression of the bearing stratum below the pile tips contribute more than 70% of the total settlement. Some effective measures to reduce the settlement of soils need to be taken into consideration to improve the bearing capacity of pile foundation.

• Journal of the Korean Geotechnical Society
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• v.17 no.6
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• pp.99-110
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• 2001

Open-ended pipe piles are often used for the foundations of both land and offshore structures because of their relatively low driving resistance. In this study, load tests were performed on model pipe piles installed in calibration chamber samples in order to investigate the effects of pile installation method on soil plugging and bearing capacity. Results of the test program showed that the incremental filling ratio (IFR), which is used to indicate the degree of soil plugging in open-ended piles, decreased (i) with increasing hammer weight for the same driving energy and (ii) with increasing hammer weight at the same fall height. The base and shaft resistance of the piles were observed to increase (i) with increasing hammer weight for the same driving energy and (ii) with increasing hammer weight at the given same fa11 height. The jacked pile was found to be have higher bearing capacity than an identical driven pile under similar conditions, mostly due to the more effective development of a soil plug in jacking than in driving.

• The Journal of Engineering Geology
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• v.30 no.1
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• pp.59-69
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• 2020

Pull-out load tests were performed on a CPR (Compaction grouting compound Pile with Reinforce) test pile, with skin friction being evaluated by the yield load and allowable bearing capacity after analyzing load-displacement curves and load-settlement curves. Results of the CPR test piles analyzed from the load-displacement curves show that the yield load and allowable bearing capacity of the large-diameter CPR test pile were about 1.4 times larger than that of the small-diameter pile. Results of the load-settlement curves reveal that the allowable bearing capacity of the CPR test pile with diameter of D500 was 1.2~2.1 times greater than that of the pile with diameter of D400. However, the allowable bearing capacity calculated using Fuller's analysis differed substantially from that determined using the P (Pull-out load) - S (Settlement) and log P - log S curves. Therefore, calculation of the allowable bearing capacity using Fuller's analysis is shown to be inappropriate.

• Journal of the Korean Geotechnical Society
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• v.32 no.9
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• pp.5-16
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• 2016

New PHC piles, where short steel pipes are attached to the pile toe, are developed to increase the base load capacity of bored pre-cast piles embedded in weathered rock. In this study, new bored pre-cast piles using the new PHC piles are installed at 7 test sites with different soil conditions, and static and dynamic pile load tests are performed to investigate quantitative characteristics on the base load capacity of new bored pre-cast piles. In addition, based on the static pile load test results, a new empirical equation for estimating the base load capacity of new bored pre-cast piles is proposed. A comparison between predicted and measured base load capacities shows that the proposed empirical equation produces conservative predictions for the new bored pre-cast piles. However, the existing design criterion significantly underestimates the base load capacity of new bored pre-cast piles.

• The Journal of Engineering Geology
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• v.30 no.4
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• pp.635-648
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• 2020

Performance improvement of helical piles in static load tests using hexagon joints that do not require welding or bolting was investigated. Two sites were selected for pile field tests to evaluate their bearing capacity. Static and pull-out load tests were undertaken to assess the method for estimating bearing capacity. The field tests indicated that the bearing capacity of the gravity grout pile was ≥600 kN in the static load test, consistent with the AC 358 Code. The non-grout pile had a bearing capacity of ≤600 kN, suggesting that gravity grouting is required. Field pile load-test results were used to establish the bearing capacity equation, based on a small number of helical pile.

• Proceedings of the Korean Geotechical Society Conference
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• 1992.03a
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• pp.69-102
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• 1992

The estimation of pile bearing capacity is important since the design details are determined from the result. There are numerous ways of determining the pile design load, but only few of them are chosen in the actual design. According to the recent investigation in Korea, the formulae proposed by Meyerhof based on the SPT N values are most frequently chosen in the design stage. During construction pile driving formulae are used and sometimes the pile loading tests are performed. In this paper the three methods are studied and compared. It is concluded that except the estimation made by pile loading test, the reliability of estimation is very poor. And the analysis of pile loading test would involve serious errors unless the end bearing capacity is measured separatly from the skin friction capacity. It is thus suggested that the separate measurement of end bearing capacity and skin friction capacity is the most reliable way of determining the pile design load.

• Journal of the Korea Concrete Institute
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• v.28 no.5
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• pp.563-570
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• 2016

The composited structural member in which two or more materials having different stress-strain relationships (steel & concrete) has increased greatly in recent years. This paper presents the experimental results of flexural capacity of the composited H-Pile subjected to bending moment. Eight composited beams were tested under direct loading condition using the frame tester. Based on the experimental results it is noted that flexural capacity of composited H-Pile increased about 20~30% and ductility ratio significantly increased. Limit state analysis of the specimens was conducted and the result shows that flexural strength by limit state analysis is conservative.