• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2000.05a
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• pp.37-40
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• 2000

Acoustically enhanced soil flushing method is a newly developed in-situ remediation technique. However, there has not been an analytical method that can be used to evaluate the effectiveness of ultrasonic wave under different conditions. This study was undertaken to investigate the degree of enhancement in contaminant removal due to ultrasonic energy on the soil flushing method. The test conditions included different levels of ultrasonic power and hydraulic gradient. The test soils were Ottawa sand, a fine aggregate, and a natural soil, and the surrogate contaminant was a Crisco Vegetable Oil. The test results showed that sonication could increase contaminant removal significantly. Increasing sonication power increased pollutant removal. The faster the flow is, the smaller the degree of enhancement will be. The pollutants in dense soils are more difficult to be removed than in loose soils.

• Journal of the Korean Society of Groundwater Environment
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• v.4 no.3
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• pp.161-167
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• 1997

A numerical model (SK-EST) for estimating hydraulic conductivity using monitoring data of underground LPG storage cavern was developed. The model calculates hydraulic conductivity from matrix equation which is established from the distribution of hydraulic potential. To verify the applicability of this model, an inverse analysis was performed using the monitoring data of pressure cell of an operating underground LPG storage cavern. And also using the water pressure parker test data which were obtained to look over the operation capability of pressure cell, conductivity variation with depth was estimated using the developed numerical model (SK-EST) and was compared with in situ results.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.476-481
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• 2009

Bi-directional load test is one of O-cell tests. The O-cell test is a system which may be used for performing static load tests on cast in situ reinforced concrete bored piles. The technique was devised and developed by Osterberg of Northwestern University(USA) and has been in use around the world. The principle of the method is that an O-cell is installed in a cast in situ bored pile base. Once the pile concrete reaches its design strength the cell is connected to an hydraulic pump and pressured. Pressurization causes the cell to expand, developing an upward force on the section of pile above the cell loads, pile movements and strains within the pile then enable the capacity of the pile and its load settlement curves to be ascertained. The O-cell pile load test with variable end plate is operated on second steps - the first step is to confirming end bearing capacity with variable end plate and the second step is similar to the conventional O-cell test. In the study, To calculate ultimate capacity of bi-directional load test using model with the pile with variable end plate O-cell.

• Magazine of the Korea Concrete Institute
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• v.6 no.6
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• pp.159-172
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• 1994

The relmund hammer test and ultrasonic pulse velocity test methods are commonly used to determine the in-situ compressive strength of concrete. One of the special feature of these methods is that they cannot give consistent and reliable results for variety of structures. In particular, very old existing structures have been generally received sreious environmental affectsand thus the strength prediction will be different from normal structures. The purpose of the present study is, therefore, to propose realistic equations to predict the in-situ strengths of actual old concrete structures. The rebound hammer and ultrasonic pulse velocity tests, carbonation depth measurments and core compressive strength measurements have been carried out for very old hydraulic and seacoast concrete structures spanning from one to about seventy years in age. From these test results, the strength-rebound number relations, the strength-pluse velocity relatinns and the strength-rebound number-pluse velocity relations have been obtained through multiple regression analysis. The present study indicates that the existing equations by nondestructive tests give quite different results from the present data. The proposed equations reasonably well predict the measured data for old concrete structures, especially for low strength concrete. The prediction equations proposed here can be efficiently used in determining the in-situ strength of old concrete structures.

• Tunnel and Underground Space
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• v.21 no.2
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• pp.128-137
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• 2011

The shut-in pressure calculated in common hydrofracturing test for vertical borehole equals generally to the minimum horizontal principal stress, so it should be considered as an essential parameter for determining the in-situ stress regime around the rock mass. It shows usually an ambiguous value in pressure-time history curves, however, because of the relationship between the behavior of hydraulic fractures and the condition of remote stress regime. In this study, a series of numerical analyses have been carried out to compare several methods for determining the shut-in pressure during hydrofracturing. The hydraulic-mechanical coupling has been applied to numerical analysis for simulating the fracture propagation by hydraulic pressure, and the different discontinuity geometry has been considered in numerical models to examine the effect of numerical element shape on fracture propagation pattern. From the numerical simulations with the four different discontinuity geometries, it was revealed that the shut-in pressure obtained from graphical methods rather than statistical method was relatively small. Consequently a care should be taken in selecting a method for determining the shut-in pressure when a stress anomaly around borehole and a fracture propagation with complicate mechanism are considered.

• The Journal of Engineering Geology
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• v.33 no.4
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• pp.519-530
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• 2023

Moye's analytical solution was examined as a method for constant-head tests under steady-state conditions, and results were compared with transient-state analyses in in situ hydraulic tests. The sensitivity of hydraulic conductivities calculated using Moye's method increased with the length of the test section, which should be as large as possible under test conditions. Particularly in low-permeability media with less than 10^-8 m/sec of hydraulic conductivity, hydraulic conductivity is lower than that under transient-state conditions and can be recalculated by adjusting the boundary between radial and spherical flow assumed in Moye's equation. Constant-head tests performed in the research borehole at the KAERI Underground Research Tunnel (KURT) indicated that transmissivities derived from the constant-head withdrawal test under transient-state conditions in low-permeability media were higher than those derived from steady-state tests, likely because the groundwater flow boundary was smaller than the "half of the test-section length"assumed by Moye's equation. When interpreting constant-head test results for crystalline rock, the hydrogeological properties of the medium may be better understood by considering assumed conditions accompanying analysis of the steady-state condition and comparing them with results for the transient-state analysis, rather than simply assuming properties based on steady-state analyses.

• Journal of Korean Tunnelling and Underground Space Association
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• v.3 no.1
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• pp.51-62
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• 2001

In-situ stress measurement using AE (Acoustic Emission) and DRA (Deformation Rate Analysis) is usually carried out under uniaxial loading in the laboratory and it consumes delay time from drilling to testing. Therefore, it should be considered how the lateral stress and delay time influence on the test results for the in-situ stress determination. As the delay time increased, the accuracy of estimating the pre-stress decreased. The pre-stress of the specimen loaded only axially was determined within an error of less than 9% (using AE) and 4% (using DRA). And the specimen on which axial pre-stress and the confining pressure were loaded had an error of less than 17% (using AE) and 14% (using DRA). The results of AE and DRA for field specimens were very similar with each other but smaller than those of hydraulic fracturing method.

• Economic and Environmental Geology
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• v.27 no.3
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• pp.295-311
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• 1994

A comprehensive in-situ tests are performed to define the hydrogeologic and hydrodispersive characteristics such as hydraulic conductivities, longitudinal dispersivity, and average linear velocities as well as conducting flow-net analysis at the study area. The results show that the study area is very heterogeneous so that hydraulic conductivities range from $6.45{\times}10^{-7}$ to $1.15{\times}10^{-5}m/s$ with average linear velocities of 0.34~0.62m/day. Whole groundwater in upper-most aquifer is discharging into the sea with specific discharge rate of $7.2{\times}10^{-3}$ to $1.3{\times}10^{-2}m/day$. The longitudinal dispersivity of the aquifer is estimated about 4.8m through In-situ injection phase test. The area is highly vulnerable to potential contaminant sources due to it's high value of DRASTIC index ranging from 139 to 155 and also under water table condition with very shallow groundwater level. To delineate contaminant plumes of toxic NaOH and carcinogenic benzene when these substances are assumed to be leaked through existing TSDF at the study area by unexpected accidents or spill, Aquifer Simulation Model (ASM) including Flow and Transport Model is used. Te simulated results reveal that the size of NaOH plume after 5 years continuous leak is about $250{\times}100m$ and benzene after 10 years, $490{\times}100m$. When the groundwater is abstracted about 50 days, which is maximum continuously sustained no-precipitation period during 30 years, with pumping rate of $100m^3/day$, THWELL program shows that the groundwater is adversly affected by sea water intrusion.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.653-657
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• 2005

This study applied the NDS method to the creek levee and the foundation of a building, for the purpose of ground improvement and cut-off. The conclusions are shown in the following. (1) The results of the field tests in the creek levee are as follows; the N value of the standard penetration test is $2{\sim}3$ before NDS grout and $9{\sim}21$ after NDS grout; in the alluvial layer, $7{\sim}11$ before NDS grout and $14{\sim}23$ after NDS grout. This confirms increasing ground strength with consistency ranging from stiff to very stiff. (2) The result of the permeability test in the creek levee shows that the ground had a great hydraulic conductivity with complete leakage before ground improvement but that the hydraulic conductivity has significantly increased to $3.17{\times}10^{-5}{\sim}4.65{\times}10^{-5}cm/sec$ after ground improvement by the NDS method. (3) The result from the field test of the foundation of the building confirms great reinforcing effects, showing that the allowable bearing capacity has increased from Pa = 5.0 $t/m^2$ before reinforcement to Pa = 25.0 $t/m^2$ after reinforcement.

• Tunnel and Underground Space
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• v.31 no.4
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• pp.243-269
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• 2021

Since the early 2010s, the social importance of research and practical projects targeting deep geological disposal of high-level nuclear waste, underground CO₂ storage and characterization of deep subsurface by borehole investigation has been increasing. In this regard, there is also a significant increase in the need for in situ test technology to obtain quantitative and reliable information on the hydraulic characteristics of deep rock mass. Through years of research and development, we have independently set up Deep borehole Hydraulic Test System (DHTS) based on the key apparatuses designed and made with our own technology. Using this system, high precision constant pressure injection tests were successfully completed at the two 1 km boreholes located in Mesozoic granite and sedimentary rock regions, Gyeongju. During the field tests, it was possible to measure very low flow rate below 0.01 l/min with micro flow rate injection/control module. In this paper, the major characteristics of DHTS are introduced and also some results obtained from the high precision field tests under the deep and low permeable rock mass environment are briefly discussed.