• Journal of Korean Tunnelling and Underground Space Association
• /
• v.13 no.6
• /
• pp.463-499
• /
• 2011

Control of ground water is one of the most important factors for long-term operation of tunnel because most tunnels are located under the ground water level. In case of a drainage tunnel, there is no pore water pressure on the lining when the drainage system is properly working. After long-term operation, however, residual pore water pressure can be developed on the lining due to the deterioration of the drainage system. In this study, the water pressure distribution under obstruction condition of drainage material and conduit on the tunnel is numerically investigated using the ICFEP program and compared with the current value being applied to the residual water pressure for rational application plan of residual water pressure on the tunnel linings.

• Geomechanics and Engineering
• /
• v.28 no.2
• /
• pp.107-116
• /
• 2022

The steady state of unsaturated soil takes a long time to achieve. The soil seepage behaviours and hydraulic properties depend highly on the wetting/drying rate. It is observed that the soil-water characteristic curve (SWCC) is dependent on the wetting/drying rate, which is known as the dynamic effect. The dynamic effect apparently influences the scanning curves and will substantially affect the seepage behavior. However, the previous models commonly ignore the dynamic effect and cannot quantitatively describe the hysteresis scanning loops under dynamic conditions. In this study, a dynamic hysteresis model for SWCC is proposed considering the dynamic change of contact angle and the moving of the contact line. The drying contact angle under dynamic condition is smaller than that under static condition, while the wetting contact angle under dynamic condition is larger than that under static condition. The dynamic contact angle is expressed as a function of the saturation rate according to the Laplace equation. The model is given by a differential equation, in which the slope of the scanning curve is related to the slope of the boundary curve by means of contact angle. Empirical models can simulate the boundary curves. Given the two boundary curves, the scanning curve can be well predicted. In this model, only two parameters are introduced to describe the dynamic effect. They can be easily obtained from the experiment, which facilitates the calibration of the model. The proposed model is verified by the experimental data recorded in the literature and is proved to be more convenient and effective.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.17 no.3
• /
• pp.227-236
• /
• 2015

In impermeable ground, water pressure is applied due to discontinuity such as joint or fissure. Therefore, water pressure should be considered in design regardless of ground condition. However, when the shape of segmental lining is circular, water pressure may reduce the lining member force, so it is important to define the assumption and the concept of design in case of high water pressure. This paper presents the concepts of design of the lining of shield tunnel at high water pressure and in impermeable ground condition. In addition, the member forces in various load conditions were compared in this study. (elastic equation, closed form solutions, beam-spring model).

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2005.11a
• /
• pp.43-50
• /
• 2005

This study is for the isolated water-Proofing method using Poly-ethylene sheet in the underground water tank which is not affected by construction environments such as wet, low temperature and surface condition. The special features of this water-proofing method are that the construction and management control are very easier and more effective than the existing construction method.

• Proceedings of the KSR Conference
• /
• 2007.11a
• /
• pp.974-981
• /
• 2007

Seoul Metro has operated the air cooling equipment established in a machine room of a station building to improve our services focused on our customers who use Seoul Metro during the summer season. However, a new set of problems has arisen with the cooling tower to support a heat exchange of cooling water. One of them is loss of efficiency in the air conditioner. The leading cause of this problem is that we use an underground type of the cooling tower. As the machine room of a station building is located in the underground of inner city because of the nature of the subway, it is difficult to establish the cooling tower on the ground. The underground structure of the No. $1{\sim}4$ subway line is unsuitable for the location requirements of the underground type of the one because it has a limited space to set up the air cooling equipment, for example, the cooling tower and a ventilating opening. As a result of such an unfavorable condition, the cooling tower doesn't work efficiently and the warmth of cooling water because of insufficiency of a heat exchange and a refrigerator's technical obstacle such as a high-temperature and a high-pressure has arisen. Accordingly, the efficiency of the air conditioning is getting lower and lower. Another problem is too wasteful with water. Each station uses the water over 30 tons every day with waterworks to replenish the cooling tower such as a evaporation, a scattering and a distribution of water. Nevertheless, the more an air conditioner increase, the more the use of water supply increase. For this reason, we can't help wasting an enormous amount of water and discharging the congelation of a low temperature(about $15^{\circ}C$) occurred in a heat exchanger inside an air conditioner. The purpose of this study is to analyze the utility of congealing water to improve efficiency of the air cooling equipment and save energy as a supplementary water for the cooling tower.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2018.11a
• /
• pp.31-32
• /
• 2018

Lately, cement mixed siliceous powder waterproofing coating has been used as a waterproofing material in the wet environment condition of an underground concrete structure. Underground is exposed to environmental influences such as pressure of ground water, pressure of soil. However, the quality standard for pressure (water pressure, earth pressure) is not specified in the specification of the cement mixed siliceous powder waterproofing coating. Therefore, in this study, the permeability test was carried out based on the assumption that the durability should be verified in consideration of the environmental aspects of the material in actual field. As a result of the test, the permeability was generated from the inorganic single type material, but it was caused by the sealing failure and the test error, and the permeability was not generated in most of the materials. The results of this study will be analyzed by reviewing the physical properties of the material, and the research direction will be resumed.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.14 no.3
• /
• pp.391-399
• /
• 2001

Three-dimensional dynamic analysis of underground openings subjected to explosive loadings considering the effects of water saturation is carried out in this study. The surrounding rock mass is assumed to be the limestone with 13.5% of porosity. Two calculations are compared using as identical explosive charge; the first in dry rock of 13.5% porosity, the second in the identical rock, but in a fully saturated condition. It is shown that velocity, displacement, and stress time histories are higher in saturated rock than those in dry rock through numerical studies. It is also shown that underground openings in saturated rock masses could be significantly more vulnerable to the potential damages associated with shear failure than those in dry medium.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 1998.11a
• /
• pp.156-161
• /
• 1998

As grouting materials for ground improvement, silicate materials such as water glass, silica-sol and so forth are used worldwide. However, they may pollute underground water. In this study, fish poison test(Korean standard industrial code KS M 0111) which estimates toxicity for fish is applied to evaluate the toxic effect by grouting materials. From the test result of the sample made of LW, LC50(Median Lethal Concentration) reaches within 24 hours. In case of the silica-sol, it does not even in 96 hours. Therefore, we can conclude that the sililca-sol grouting method is more free from the danger of underground water pollution. From the result that the mortality of fish under the condition of pH 8.6 is 0% within 96 hours, the groundwater can be saved by controlling pH below 8.6 for the grouting in the field.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2000.10a
• /
• pp.281-288
• /
• 2000

Three-dimensional dynamic analysis of underground openings subjected to explosive loadings considering the effects of water saturation is carried out in this study. The problem considered in this study is an unlined circular tunnel subjected to a finite cylindrical charge placed at the center of the proposed tunnel. The surrounding rock mass is assumed to be the limestone with 13.5% of porosity. Two calculations are compared using an identical explosive charge; the first in dry rock of 13.5% porosity, the second in the identical rock, but in a fully saturated condition. It is shown that underground openings in saturated porous medium could be significantly more vulnerable to the potential damages associated with high motions and shear failure than those in dry medium.

• Structural Engineering and Mechanics
• /
• v.90 no.5
• /
• pp.493-504
• /
• 2024

This paper presents the methodology and results for the investigation of the structural safety of 40 aged underground water tanks to support the weight of photovoltaic (PV) systems that were supposed to be placed on their roof reinforced concrete (RC) slabs. The investigation procedure included (1) review of available documents; (2) visual inspection of the roof RC slabs; (3) carrying out a series of nondestructive (ND) tests; and (4) analysis of results. Out of the 40 tanks, eleven failed the visual inspection phase and were discarded from further investigation. The roof RC slabs of the tanks that passed the visual inspection were subjected to a series of ND tests that included infrared thermography, impact echo, ultrasonic pulse velocity (UPV), Schmidt hammer, concrete core compressive strength, and water-soluble chloride content. The NDT results proved that eight more tanks were not suitable to support the PV systems. Based on the results of the visual inspection and testing, a probabilistic decision-making criterion was established to reach a decision regarding the structural integrity of the roof slabs. The study concluded that the condition of the drainage filter was essential in protecting the tanks and its intact presence can be used as a strong indication of the structural integrity of the roof RC slabs.