• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.18 no.2
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• pp.1-9
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• 2022

A novel steel-pipe energy pile is introduced, in which the deformed rebars for main reinforcing are replaced with steel pipes in a large diameter cast-in-place energy pile. Here, the steel pipes act as not only reinforcements but also heat exchangers by circulating the working fluid through the hollow hole in the steel pipes. Under this concept, the steel-pipe energy pile can serve a role of supporting main structures and exchanging heat with surrounding mediums without installing additional heat exchange pipes. In this study, the steel-pipe energy pile was constructed in a test bed considering the material properties of steel pipes and the subsoil investigation. Then, the thermal performance test (TPT) in cooling condition was conducted in the constructed energy pile to investigate thermal performance. In addition, the thermal performance of the steel-pipe energy pile was compared with that of the conventional large diameter cast-in-place energy pile to evaluate its applicability. As a result, the steel-pipe energy pile showed 11% higher thermal performance than the conventional energy pile along with much simpler construction processes.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.70-77
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• 2010

In this paper, a case study of drivability and bearing capacity of large diameter steel pipe piles at PTT LNG site in Thailand is introduced. The LNG facilities were designed to be founded on steel pipe pile foundations driven into the weathered rock formation overlaid by sand layers. The drivability analyses of open ended pipe piles were carried out using GRL WEAP program and the bearing capacities of the piles were estimated. Dynamic load tests were performed to evaluate end bearing resistance, and it is shown that the measured end bearing resistance is smaller than the calculated end bearing because the plugging does not develop sufficiently in case of large diameter pipe piles.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.5
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• pp.325-337
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• 2021

On the road and rail tunnels, the evacuation pathway and facilities such as smoke-control and fire suppression system are essential in tunnel fire. In the long twin tunnels, the cross-connection tunnel is usually designed to evacuate from the tunnel where the fire broke out to the other tunnel. In twin shield tunnels, the segment lining has to be demolished to construct the cross-connection tunnel. Considering the modern shield TBM is mostly the closed chamber type, the exposure of underground soil induced by removal of steel segment lining is the most danger construction step in the shield tunnel construction. This case study introduces the excavation method using the thrust of large steel pipe and reviews the measured data after the construction. The large steel pipe thrust method for the cross-connection tunnel can stabilize the excavated face with the two mechanisms. Firstly, the soil in front of excavated face is cylindrically pre-supported by the large steel pipe. Secondly, the excavated face is supported by the plugging effect caused by the soil pressed into the steel pipe. It was reviewed that the large steel pipe thrust method in the cross-connection tunnel is enough to secure the construct ability and stability in soil from the measurement results about the deformation and stress of steel pipe.

• Journal of the Korean Geotechnical Society
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• v.35 no.12
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• pp.123-134
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• 2019

This study presents dynamic responses of circular pipe models as a part of fundamental studies on dynamic stability monitoring of the large circular steel pipe cofferdam with the ship collision. Small-scaled laboratory experiments are performed with a single and bolted circular steel pipes with a diameter, thickness, and height of 30, 0.4, 90 cm, respectively. The bolted circular steel pipe is configured with three segments of 30 cm in height. Circular steel pipe models are embedded in a soil tank, all 1 m in length, width, and height. The thickness of soil in the soil tank is set at 23 cm. The ship collision is simulated with a hammer impacting. The dynamic responses are investigated with different water levels of 25, 40, 55, and 70 cm. Experimental results show that a signal energy decreases with increasing water level. More sensitive reduction in the energy appears for the bolted circular steel pipe. A predominant frequency decreases with increasing water level for both single and bolted steel pipes. The minor reduction in the frequency appears for the bolted circular steel pipe under the water level of 70 cm. This study suggests that the signal energy and frequency response is useful for the dynamic stability monitoring of the large circular steel pipe cofferdam.

• Journal of the Korean Geotechnical Society
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• v.36 no.11
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• pp.71-81
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• 2020

The large circular steel pipe for a marine bridge foundation has been developed as a construction method capable of performing the role of the working platform and cofferdam. The objective of this study is to demonstrate the wireless remote sensing system for monitoring the stability of the large circular steel pipe during construction and operation through field tests. The artificial seabed ground with an water level of 4 m is constructed for field tests. The large circular steel pipe with a diameter of 5 m and height of 9.5 m is installed into the ground by suction, and the embedded depth is 5 m. The inclinometer and strain gauges are installed on different surfaces of the upper module, and the tilt angle and stress are monitored throughout the entire construction process. As results, tilt angles are measured to be constant during the suction penetration. However, the tilt angle is larger in the x-axis direction. In addition, even when installed on different surfaces, the tilt angle in the same axial direction is measured to be almost the same. The stresses measured by strain gauges increase during suction penetration and decrease during pull-out. Based on measured stresses, it is found that the eccentricity is acting on the large circular steel pipe. This study shows that a wireless remote sensing system built with an inclinometer and strain gauge can be a useful tool for the stability monitoring of the large circular steel pipe.

• Journal of Industrial Technology
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• v.24 no.A
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• pp.239-250
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• 2004

Numerical analysis were performed to investigate the stability and internal movement of tunnel located beneath the base of abutment of bridge according to the method of supporting tunnel. Two supporting methods of the multi-staged grouting method with steel pipes and the large diameter of pipe supporting method were used in the centrifuge model tests. The slip form of model lining, specially built to simulate the process of tunnel excavating under the condition of accelerated g-level, was used in the centrifuge model tests. Four centrifuge model tests were performed, changing the supporting methods of the multi-staged grouting method with steel pipes and the large diameter of pipe supporting method and the location of model abutment base of bridge. For internal displacement of tunnel, movements of the crown. The left and the right sides of spring line were measured during the proceeds of excavating tunnel in centrifuge model tests. Test results were compared with numerically estimated values of internal displacement of tunnel by using the commercially available FEM software of PENTAGON-3D. It was found that they were in good agreements and the large diameter of pipe supporting method was more stable than the multi-staged grouting method with steel pipes with respect to the internal movement of tunnel.

• Journal of Welding and Joining
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• v.10 no.3
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• pp.54-62
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• 1992

Large steel water pipes are joined prevalently by bell and method and welded at inside and outside of lapped parts. According to the Korean Standard(KS) for fabrication of water pipes, the weldments are designed to have the length of leg which is same as or larger than the thickness of the pipe. It is recently pointed out that the standard size of weldments is too large, which results in an excessive consumption of material and labor. In this study, several cases of weldments having different sizes were investigated to reduce the length of leg to the effective size. For each case, the analysis of stresses was carried out to evaluate the safety of the welded pipes by using a package program, ANSYS, under the consideration of the loading condition of water pipes which includes the soil pressure on the pipe, the load over the road, and temperature change of the pipe. The results of this study revealed that the weldment which has the length of leg of the size over 0.7*thickness of the pipe could provide a stress level below the yield strength. Especially when the length of leg is 85% of the wall thickness, the maximum equivalent stress is only slightly higher than that of the leg of fillet of the size of 1.0*pipe thickness.

• Journal of Mechanical Science and Technology
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• v.15 no.11
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• pp.1533-1540
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• 2001

A high-temperature sodium stainless steel heat pipe was fabricated and its performance has been investigated. The working fluid was sodium and it was sealed inside a straight tube container made of stainless steel. The amount of sodium occupied approximately 20% of the total volume of the heat pipe and its weight was 65.7gram. The length of a stainless steel container is 1002mm and its outside diameter is 25.4mm. Performance tests were carried out in a room air condition under a free convective environment and the measured temperatures are presented. The start-up behavior of the heat pipe from a frozen state was investigated for various heat input values between 600W and 1205W. In steady state, axial temperature distributions of a heat pipe were measured and its heat transfer rates were estimated in the range of vapor temperature from 50$0^{\circ}C$ to 63$0^{\circ}C$. It is found that there are small temperature differences in the vapor core along the axial direction of a sodium heat pipe for the high operating temperatures. But for the range of low operating temperatures there are large temperature drops along the vapor core region of a sodium heat pipe, because a small vapor pressure drop makes a large temperature drop. The transition temperature was reached more rapidly in the cases of high heat input rate for the sodium heat pipe.

• Journal of the Korean Society of Safety
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• v.30 no.1
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• pp.47-51
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• 2015

In the study, a new non-open cut tunnel steel pipe method using slot hole has been developed. As is overcomes shortcomings of conventional methods, it is applied to the field. The main concept of the new method is the steel pipe pumping system with slot holes which, by means of formation slot holes between each steel pipe, applied to the magnitude of the relaxed earth pressure caused by excavation to the ground to prevent ground displacement. The stability of the support members and effect of displacement control of the new method were verified through several ways as numerical analysis and site test. The new method was applied to the construction of a 11.5m wide, 7.4m high and 50m long section that passes side subway and large buildings in inner city. By applying the new method, tunnel construction was successfully completed in 6 months. It decreases the construction period to 30% compared to that of conventional methods, and ground was almost negligible.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.4
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• pp.21-27
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• 2015

Induction bending is a method that allows the bending of any material that conducts electricity. This technology applies a bending force to a material that has been locally heated by an eddy current induced by a fluctuating electromagnetic field. Induction bending uses an inductor to locally heat steel through induction. This results in a narrow heat band in the shape to be bent. In general, the reduction of thickness attenuation of a large-diameter steel pipe is not allowed to exceed 12.5%. In this paper, in order to meet the standard of thickness attenuation reduction, a non-uniform heating temperature jump-bending process was investigated. As a result, the developed bending technique meets the requirements of thickness attenuation reduction for large-diameter steel pipes.