• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.225-232
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• 1999

Construction case of PRD (Percussion Rotary Drill) pipe pile and matters to be attended in construction of PRD pile were reviewed. The compressive and uplifting static pile load tests for PRD piles were performed and, also, analysis by Pile Driving Analyzer was done. Based on these results, bearing components in each resisting part (that is: steel toe, external skin, and internal skin) were measured separately. The measured resisting force was compared to the value calculated by the estimated formula. The pile capacity was mobilized in steel toe area and the external skin friction and the internal friction were not produced. Thus, it could be considered that toe of PRD pile should be supported in hard bearing stratum (for example, the fresh soft rock).

• Journal of the Korean Geotechnical Society
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• v.23 no.3
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• pp.61-75
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• 2007

Deep foundations have been popularly installed in hard stratum such as gravels or rocks in Korea. However, it is necessary to consider sand or sandy gravel layers that locate at the mid-depths as the bearing stratum of piles in the thick Nakdong River deltaic deposits, as done in the Chaophraya (Bangkok) and Mississippi River deltas. This study was focused on the finding of suitable methods for estimating bearing capacity when driving prestressed high-strength concrete (PHC) piles to a required depth in the deltaic area. Ground investigation was performed at five locations of two sites in the deltaic area. Bearing capacity of the driven piles has been computed using a number of proposed methods such as CPT-based and other analytical methods, based on the ground investigation and comparison one another other. Five PDA (pile driving analyzer) tests were systematically carried out at the whole depths of embedded piles, which is a well-blown useful technique for the purposes. As the results, the bearing capacities calculated by various methods were compared with the PDA and static load testing results. It was found that the shaft resistance is significantly governed by set-up effects and then the long-term value agrees well with that of the $\beta$ method. Also, the design methods for toe resistance were determined based on the SLT result, rather than PDA results that led to underestimation. Moreover, using the CPT results, appropriate methods were proposed for calculating the bearing capacity of the piles in the area.

• Geomechanics and Engineering
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• v.21 no.1
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• pp.23-33
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• 2020

An advancing cutting roof for gob-side entry retaining with no-pillar mining under specific geological conditions is more conducive to the safe and efficient production in a coalmine. This method is being promoted for use in a large number of coalmines because it has many advantages compared to the retaining method with an artificial filling wall as the gateway side filling body. In order to observe the inner structure of the gateway cutting roof and understand its stability mechanism, an equivalent material simulation experiment for a coalmine with complex geological conditions was carried out in this study. The results show that a "self-stabilization bearing structure" equilibrium model was found after the cutting roof caving when the cut line deviation angle was unequal to zero and the cut height was greater than the mining height, and the caving roof rock was hard without damage. The model showed that its stability was mainly controlled by two key blocks. Furthermore, in order to determine the optimal parameters of the cut height and the cut line deviation angle for the cutting roof of the retaining gateway, an in-depth analysis with theoretical mechanics and mine rock mechanics of the model was performed, and the relationship between the roof balance control force and the cut height and cut line deviation angle was solved. It was found that the selection of the values of the cut height and the cut line deviation angle had to conform to a certain principle that it should not only utilize the support force provided by the coal wall and the contact surface of the two key blocks but also prevent the failure of the coal wall and the contact surface.