• The Journal of Engineering Geology
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• v.27 no.2
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• pp.153-164
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• 2017

The geological factors for causing ground subsidence are very diverse. It can be affected by any geological or extrinsic influences, and even within the same geological factor, the soil depression impact factor can be determined by different physical properties. As a result of reviewing a large number of papers and case histories, it can be seen that there are seven categories of ground subsidence factors. The depth and thickness of the overburden can affect the subsidence depending on the existence of the cavity, whereas the depth and orientation of the boundary between soil and rock are dominant factors in the ground composed of soil and rock. In case of soil layers, more various influencing factors exist such as type of soil, shear strength, relative density and degree of compaction, dry unit weight, water content, and liquid limit. The type of rock, distance from the main fracture and RQD can be influential factors in the bedrock. When approaching from the hydrogeological point of view, the rainfall intensity, the distance and the depth from the main channel, the coefficient of permeability and fluctuation of ground water level can influence to ground subsidence. It is also possible that the ground subsidence can be affected by external factors such as the depth of excavation and distance from the earth retaining wall, groundwater treatment methods at excavation work, and existence of artificial facilities such as sewer pipes. It is estimated that to evaluate the ground subsidence factor during the construction of underground structures in urban areas will be essential. It is expected that ground subsidence factors examined in this study will contribute for the reliable evaluation of the ground subsidence risk.

• The Journal of Engineering Geology
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• v.29 no.1
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• pp.23-35
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• 2019

Landslides occur due to heavy rainfall in the summer season. Some of water may infiltrate into the ground; it causes a high saturation condition capable of causing a landslide. Soil properties are crucial in estimating slope stability and debris flow occurrence. The main study areas are Gwanaksan, Suraksan and Bukhansan (Mountain) in Seoul. A total of 44 soil samples were taken from the study area; and a series of geotechnical tests were performed. Physical and mechanical properties were obtained and compared based on region. As a result, among well-graded soils, they are classified as a clayey sand. Coarse-grained and fine-grained contents are approximately 95% and 5%, respectively, with very low amount of clay content. Density, liquid limit and dry unit weight are ranged in $2.62{\sim}2.67g/cm^3$, 27.93~38.15% and $1.092{\sim}1.814g/cm^3$. Cohesion and internal friction angle are 4 kPa and $35^{\circ}$ regardless of mountain area. Coefficient of permeability is varied between $3.07{\times}10^{-3}{\sim}4.61{\times}10^{-2}cm/sec$; it means that it results in great seepage. Permeability is inversely proportional to the uniformity coefficient and is proportional to the effective particle size. In the formal case, there was a difference by mountain area, while in the latter, the tendency was almost similar.

• The Journal of Engineering Geology
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• v.31 no.3
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• pp.381-393
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• 2021

Physical, mechanical, hydraulic, and geophysical tests were applied to validate methods of inspecting the effectiveness of grouting on an agricultural reservoir dam. Data obtained from series of in situ and laboratory tests considered four stages: before grouting; during grouting; immediately after grouting; and after aging the grouting for 28 days. The results of SPT and triaxial tests, including the unit weight, compressive strength, friction angle, cohesion, and N-value, indicated the extent of ground improvement with respect to grout injection. However, they sometimes contained errors caused by ground heterogeneity. Hydraulic conductivity obtained from in situ variable head permeability testing is most suitable for identifying the effectiveness of grouting because the impermeability of the ground increased immediately after grouting. Electric resistivity surveying is useful for finding a saturated zone and a seepage pathway, and multichannel analysis of surface waves (MASW) is suitable for analyzing the effectiveness of grouting, as elastic velocity increases distinctly after grouting injection. MASW also allows calculation from the P- and S- wave velocities of dynamic properties (e.g., dynamic elastic modulus and dynamic Poisson's ratio), which can be used in the seismic design of dam structures.

• Journal of Environmental Health Sciences
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• v.48 no.2
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• pp.86-95
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• 2022

Background: As high concentrations of uranium and radon have been detected in some areas in Korea, it is considered necessary to investigate natural radioactive materials in the Gwangju area. Objectives: This study aimed to identify the hydrochemical characteristics of groundwater in Gwangju and investigate the distribution characteristics of uranium and radon, which are naturally radioactive substances. Methods: To determine the uranium and radon concentrations in groundwater according to the geology of the Gwangju area, we measured 62 groundwater wells. A geological distribution map of uranium and radon content was prepared for this study. Results: The groundwater type, defined using a Piper diagram, was mainly Ca-HCO₃. The concentration of uranium in the groundwater ranged from 0 to 29.3 ㎍/L, with a mean of 3.3 ㎍/L and a median of 0.9 ㎍/L. The median concentration of uranium in groundwater was highest in alluvium, granitic gneiss, and biotite granite (classified by geological unit), in that order. The concentration of radon in the groundwater ranged from 4.8 to 313.2 Bq/L, with a mean of 75.6 Bq/L and a median of 59.6 Bq/L. The median concentration of radon in groundwater was highest in biotite granite, alluvium, and granitic gneiss, in that order. As a result of the correlation analysis of groundwater in the study area, there was no significant correlation between uranium and radon. Conclusions: In this study area, uranium was shown to be far below the concentrations allowed by drinking water quality standards, but radon concentrations exceeded drinking water quality monitoring standards in 11% of the samples. It was judged that appropriate measures, such as the installation of radon reduction facilities, will be required after a thorough review of high-concentration radon detection sites of in the research area.

• The Journal of Engineering Geology
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• v.32 no.4
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• pp.585-596
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• 2022

This study determined major factors influencing landslide occurrence along a forest road near Sangsan village, Sancheok-myeon, Chungju-si, Chungcheongbuk-do, South Korea. Within a 2 km radius of the study area, landslides occur intensively during periods of heavy rainfall (August 2020). This makes study of the area advantageous, as it allows examination of the influence of only geological and tomographic factors while excluding the effects of rainfall and vegetation. Data for 82 locations (37 experiencing landslides and 45 not) were obtained from geological surveys, laboratory tests, and geo-spatial analysis. After some data preprocessing (e.g., error filtering, minimum-maximum normalization, and multicollinearity), structural equation model (SEM) and logistic regression (LR) analyses were conducted. These showed the regolith thickness, porosity, and saturated unit weight to be the factors most influential of landslide risk in the study area. The sums of the influence magnitudes of these factors are 71% in SEM and 83% in LR.

• The Journal of Engineering Geology
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• v.32 no.1
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• pp.173-191
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• 2022

In this study, the shear wave velocity of the ground was measured using Flat TDR, and the precision analysis of the measured value and the verification of field applicability were performed. The shear wave velocity measurement value was derived in the field using the piezo-stack combined in the Flat TDR. analyzed. As a result of the experiment, the average value of the change in shear wave speed at the time of grout material injection was 10.15 m/s at the beginning of age, and the average value of the change in shear wave speed after the 7th to 14th days was 65.99 m/s, showing a tendency to increase with age. Also, it was found that dry density and shear wave speed increased as the water content increased on the dry side, and that the dry density and shear wave rate decreased as the water content increased on the wet side as the water content increased. The shear modulus value derived from the field test was confirmed to be a minimum of 17.36 MPa and a maximum of 28.13 MPa, confirming a measurement value similar to the reference value. Through this, it can be seen that the measured value of the shear modulus using Flat TDR is reliable data, and it can be determined that the compaction management of the site can be effectively managed in the future.

• The Journal of Engineering Geology
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• v.34 no.1
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• pp.137-146
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• 2024

The pertinent Korean Industrial Standard (KS F) requires that rocks dried at 105 ± 5℃ be taken out of the oven into air and weighed on a scale. However, when rocks are exposed to air after the drying process, they absorb moisture, meaning that their weight will increase. In this study, eight cubic samples of Hwangdeung granite of different sizes were used to measure and compare the dry weight. The dry singularity weight measured in air was smaller than that measured in the drying oven. The difference in dry weight showed a positive correlation with sample size. Conversely, the difference in dry weight per unit weight of rock showed a negative correlation with sample size. The weight of a rock sample exposed to air is determined by the magnitude of the influence of convection currents occurring around the heated rock and the influence of moisture absorption in air. A singularity occurs when the magnitudes of these two effects are equal. The larger the rock sample, the longer the time taken for the singularity to occur, the greater the weight loss of the sample, and the longer the time taken for the sample to return to the initially measured weight on account of the greater moisture absorption for larger samples than smaller samples. In the future, research into the singularity and dry weights measured inside the drying oven will help to identify and address the limitations of the current KS F testing regulations.

• Advances in environmental research
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• v.9 no.3
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• pp.175-189
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• 2020

Municipal solid waste disposal is considered as one of the most important risks for environmental contamination which necessitates the development of strategies to reduce destructive consequences on the ecosystem as related especially to heavy metal accumulation. This study investigates heavy metal (i.e., As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Zn) accumulation in the Tonekabon region, NW of Iran that is related to city waste disposal and evaluates the environmental impact in the Caspian Sea coastal region. For this purpose, after performing field studies and collecting 50 soil specimens from 5 sites of the study area, geochemical tests (i.e., inductively coupled plasma mass spectrometry, atomic absorption spectroscopy and x-ray fluorescence) were conducted on the soil specimens collected from the 5 sites (named as Sites A1, A2, A3, A4 and A5) and the results were used to estimate the pollution indices (i.e., geo-accumulation index, normalized enrichment factor, contamination factor, and pollution load index). The obtained indices were utilized to assess the eco-toxicological risk level in the landfill site which indicated that the city has been severely contaminated by Cu, Mn, Ni, Pb and Zn. These levels have been developed along the stream towards the nearshore areas indicating uptake of soil degradation. The heavy metal contamination was classified to range from unpolluted to highly polluted, which indicated serious heavy metal pollution in the study area as related to municipal solid waste disposal in Tonekabon.

• Water for future
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• v.8 no.2
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• pp.30-40
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• 1975

Hydrogeological survey and geophysical prospecting have been carried out in Saudi Arabia for the purpose of finding groundwater in the soil and rock at the request of General trading company in Jeddah, Saudi Arabia. The surveyed area is located on $38^{\circ}-39^{\circ}$ 30' in longitude and $26^{\circ}-26^{\circ}$ 30' in latitude. The topography of this area is dominated by northwest southeast mountain range composed mostly of precambrian rocks and basalt of tertiary period. Geology is mainly composed of greenstone, granite, andesite, diorite rhyolite of pre-cambrian era and sandstone of cambrian period which are underlained by basalt and andesite of tertiary period and alluvium of quaternary unconformably. The instruments used in this investigation are TR-18B2 radioactivity unit which isjapanese patented and A.C. Terrameter, a resistivity meter manufactured by ABEM of Stockholm, Sweden. Radioactivity method has been conducted along the Alula-Khaybar road, totally 164Km by the car-borne. As a result of the above survey 16 places have been selected and these anomalies show 1.2N-1.6N compared to background of each area in intensity with width of 10-50m. Resistivity vertical profiling which made use of Schlumberger configuration method has been made over selected areas by radioactivity method to provide hydrogeological information for a water resources survey. The result of resistivity shows that good aquifers are located in the western part of surveyed area where sedimentary rock is distributed. The strata showing 10-50, ${\Omega}-m$ in resistivity are thought to be waterbearing layer. The variations in aquifer resistivity found, are thought to be due to verying clay content, which could be related to aquifer yield. It has proved impossible to detect small salinity variation in the buried aquifer by geophysics. As a result of resistivity prospecting 10 places are recommended to be drilled at the anomalies as shown attached map. yields from the proposed holes have been estimated approximately from $20m^3$ to $200m^3$ per day. Prior to drilling for groundwater, test boring using ${\c}4"$ should be drilled in order to obtain more reliable hydrogeological information for the construction of perfect wells.ells.

• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.2
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• pp.161-174
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• 2003

Applicability of the Decision Aids for Tunneling (DAT) technique is investigated in this study to better understand the efficiency of the decision making process during tunnel construction. For this, a traffic tunnel under construction is adopted and information on the construction procedure, i.e., overall geology, unit cost and construction time for each excavation process, is provided periodically. Various scattergrams in which cost-time simulation results are plotted are obtained according to the simulation methods and final prediction on the construction time/cost is made. It is found that the uncertainty in the cost distribution is greater than the uncertainty in the time distribution for each cycle simulation and the uncertainties in time and cost for the one time simulations are comparable. Future work will be concentrated on the updating scheme using the face mapping data and various parametric studies will also be performed.