• Journal of the Korean Geotechnical Society
• /
• v.16 no.1
• /
• pp.131-143
• /
• 2000

Several theoretical analyses are performed to predict the vertical load on embankment piles with cap beams. The piles are installed in a row in soft ground below the embankment and the cap beams are placed perpendicular to the longitudinal axis of the embankment. Two failure mechanisms such as the soil arching failure and the punching shear failure are investigated according to the failure pattern in embankment on soft ground supported by piles with cap beams. The soil arching can be developed when the space between cap beams is narrow and/or the embankment is high enough. In the investigation of the soil arching failure, the stability in the crown of the arch is compared with that above the cap beams. The factors affecting the load transfer in the embankment fill by soil arching are the space between cap beams, the width of cap beams and the soil parameters of the embankment fill. The portion of the embankment load carried by cap beams decreases with increment of the space between cap beams, while it increases with the embankment height, the width of cap beams, the internal friction angle and cohesion of the embankment fill. Thus, the factors affecting load transfer in embankment should be appropriately decided in order to maximize the effect of embankment load transfer by piles.

• The Journal of Engineering Geology
• /
• v.26 no.3
• /
• pp.315-324
• /
• 2016

Because of a fissility characteristics of shale in the Gyoungsang super-group, it breaks down to debris when daylighted by construction work and causes a slope unstability. To assess the durability property of shale, a series of slake durability tests was conducted by controlling test conditions such as shape of specimen, number of specimen, revolution speed, revolution number, drying temperature and pH of submerging liquid. For the specimen shape, cube one showed relatively lower durability index than cuboid and/or fan shape one. The test with the more number of specimens showed the less durability index because of a higher friction among specimens in the drum. The durability index is linearly decreased by increasing the total number of revolution, while the revolution velocity could not affect the index. And the durability index is also decreased by increasing the drying temperature of specimen and by decreasing the pH of submerging liquid. Because the durability index of shale is almost similar to that of crystalline rocks, the disintegration characteristics of shale could not be assessed by the slake durability test recommended by ISRM, and thus a new test method by changing the total revolution number may be required for the shale having fissility characteristics.

• Composites Research
• /
• v.13 no.6
• /
• pp.1-8
• /
• 2000

The fabrication Process of $Al_2O_{3p}$/AC8A composites by pressureless infiltration technique and the effects of additive Mg content and volume fraction of particulate reinforcement on mechanical and wear properties were investigated. It was found that the bending strength decreased with increasing volume fraction of $Al_2O_{3p}$ particles. Whereas hardness increased with volume fraction of $Al_2O_{3p}$ particles. The decrement of strength in case of high volume fraction of $Al_2O_{3p}$ particles was attributed to high porosity level. In terms of additive Mg content, $Al_2O_{3p}$/AC8A composites containing around 5~7wt% of additive Mg indicated the highest strength, and hardness values increased with additive Mg contents. Wear resistance of AC8A alloy were improved by reinforcement of $Al_2O_{3p}$ particles especially at high sliding velocity. Wear property of $Al_2O_{3p}$/AC8A composites and AC8A alloy exhibited different aspects. $Al_2O_{3p}$/AC8A composites indicated more wear loss than AC8A alloy at slow velocity region. However a transition point of wear loss was found at middle velocity region which shows the minimum wear loss and wear loss at high velocity region exhibited almost same value as at slow velocity region, whereas wear loss of AC8A alloy almost linearly increased with sliding velocity. It was found that $Al_2O_{3p}$/AC8A composites containing $Al_2O_{3p}$ volume fraction of 20% exhibited abrasive wear surface regardless of sliding velocity and $Al_2O_{3p}$/AC8A composites containing $Al_2O_{3p}$ volume fraction of 40% showed slightly adhesive wear surface at low sliding velocity, and it progressed to severe wear as increasing the sliding velocity.

• The Journal of Engineering Geology
• /
• v.25 no.3
• /
• pp.357-368
• /
• 2015

Brittle failure of Mesozoic granite in the Daejeon region is predicted using empirical analysis and numerical modeling techniques. The input parameters selected for these techniques were based on the results of laboratory tests, including damage-controlled tests. Rock masses that were considered to be strong during laboratory testing were assigned to "group A" and those considered to be extremely strong were assigned to "group B". The properties of each group were then used in the analyses. In-situ stress measurements, or the ratio of horizontal to vertical stress (k), were also necessary for the analyses, but no such measurements have been made in the study area. Therefore, k values of 1, 2, and 3 were assumed. In the case of k=1, empirical analysis and numerical modeling show no indication of brittle failure from the surface to1000 m depth. When k=2, brittle failure of the rock mass occurs at depths below 800 m. For k=3, brittle failure occurs at depths below 600 m. Although both the Cohesion Weakening Friction Strengthening (CWFS) and Mohr-Coulomb models were used to predict brittle failure, only the CWFS model performed well in simulating the range and depth of the brittle failure zone.

• Elastomers and Composites
• /
• v.46 no.1
• /
• pp.70-77
• /
• 2011

A new piece of test equipment, the slurry wear tester (SWT), was proposed in this study to evaluate the wear behavior of rubber vulcanizate in environmental contact with slurry. Natural rubber (NR) and chloroprene rubber (CR) were chosen as the basic matrices to test the slurry wear. The fluids used to fill the chamber of the SWT were 35% HCl and NaCl solution. The Akron abrasion test was used for comparison with SWT. According to the results of the Akron abrasion test, CR vulcanizate abraded more rapidly than NR vulcanizate under same test condition. It was found that the hysteresis of rubber was key factor contribute to the wear behavior. However, the slurry wear rate of the NR and CR vulcanizates did not change significantly, even with changes in the concentration of acid and the immersion time in both HCl and NaCl solutions; the fluid decreased the friction between the abrasive paper and the specimen. It also reduced the heat generated from repeated deformation and wear debris at the surface of the SWT's abrasion arm. Thus, these phenomena affected the wear behavior of rubber vulcanizate and caused different results in the conventional Akron abrasion test. This outcome could have resulted in an incorrect analysis if the slurry wear behavior of the rubber vulcanizate was estimated by the conventional abrasion tests, which are operated under dry conditions.

• Journal of the Korean Geotechnical Society
• /
• v.29 no.2
• /
• pp.47-56
• /
• 2013

There are many technical problems, which can not be resolved by the concept of saturated soil mechanics. Unsaturated soils show an apparent cohesion due to negative pore pressure and relatively lower permeability due to entrapped air compared to saturated soils. The determination of engineering properties of soils with various moisture content is very important to evaluate shear strength and stability of natural and engineered soils. So various researches should be made on unsaturated soils. Especially, sandy soils are widely distributed near Nakdong river, one of the four rivers where Restoration Projects were carried out. Many structures such as dams, flood control facilities, detention facilities and reservoirs have been built in this area. In this study, unsaturated triaxial compressive tests were conducted on sands or silty sands at Nakdong river in order to provide their fundamental characteristics for design and construction of geotechnical structures. As a result of the tests, the maximum deviator stress increased as the confining stress and matric suction increased. The cohesion increased non-linearly as the matric suction increased, but the angle of internal friction was marginally changed.

• The Journal of Engineering Geology
• /
• v.31 no.3
• /
• pp.381-393
• /
• 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 the Korean Geotechnical Society
• /
• v.25 no.6
• /
• pp.17-29
• /
• 2009

There has been an increase in the investigation of deep sea sediments with a consequent increase in the amount of energy required to undertake these investigations. The geotechnical characteristics of Ulleung Basin sediment are explored by using depressurized specimens following methane production tests carried out on pressured core samples obtained at 2,100 m water depth and 110 m below sea floor. Geotechnical index tests, X-ray diffraction, and scanning electron microscope are conducted to identify the geotechnical index parameters, clay mineralogy, chemical composition, and microstructure of the sediments. Compressibility, and elastic and electromagnetic wave parameters are investigated for two samples by using a multi sensing instrumented oedometer cell. The strength chatracteristics are obtained by the direct shear tests. The dominant clay minerals are mostly kaolinite, illite, chlorite, and calcite. The SEM shows a well-developed flocculated structure of the microfossil. Void ratio, electrical resistivity, real permittivity, conductivity, and shear wave velocity show bi-linear behavior with the effective vertical stress: as the vertical effective stress increases. The friction angle obtained by the direct shear test is about $21^{\circ}$, which is similar to the value observed in the Ulleung Basin sediments. This study shows that the understanding of the behavior acting on the diatomaceous marine sediment is important because it often maintains the useful energy resources such as gas hydrate and so will be the new engineering field in the next generation.

• Tunnel and Underground Space
• /
• v.33 no.3
• /
• pp.109-125
• /
• 2023

Disposal repository for high-level radioactive waste secures its safety by means of engineered and natural barriers. The performance of these barriers should be tested and verified through various aspects in terms of short and/or long-term. KAERI has been conducting various in-situ demonstrations in KURT (KAERI Underground Research Tunnel). After completing previous experiment, a conceptual design of an improved in-situ experiment, i.e. K-COIN (KURT experiment of THMC COupled and INteraction), was established and detailed planning for the experiment is underway. Preliminary characterizations were conducted in KURT for siting a K-COIN test site. 15 boreholes with a depth of about 20 m were drilled in three research galleries in KURT and intact rock specimens were prepared for laboratory tests. Using the specimens, physical measurements, uniaxial compression, indirect tension, and triaxial compression tests were conducted. As a result, specific gravity, porosity, elastic wave velocities, uniaxial compressive strength, Young's modulus, Poisson's ratio, Brazilian tensile strength, cohesion, and internal friction angle were estimated. Statistical analyses revealed that there did not exist meaningful differences in intact rock properties according to the drilled sites and the depth. Judging from the uniaxial compressive strength, which is one of the most important properties, all the specimens were classified as very strong rock so that mechanical safety was secured in all the regions.

• Journal of the Korean Geotechnical Society
• /
• v.39 no.12
• /
• pp.37-46
• /
• 2023

Dynamic soil properties are essential factors for predicting the detailed behavior of the ground. However, there are limitations to gathering soil samples and performing additional experiments. In this study, we used an artificial neural network (ANN) to predict dynamic soil properties based on static soil properties. The selected static soil properties were soil cohesion, internal friction angle, porosity, specific gravity, and uniaxial compressive strength, whereas the compressional and shear wave velocities were determined for the dynamic soil properties. The Levenberg-Marquardt and Bayesian regularization methods were used to enhance the reliability of the ANN results, and the reliability associated with each optimization method was compared. The accuracy of the ANN model was represented by the coefficient of determination, which was greater than 0.9 in the training and testing phases, indicating that the proposed ANN model exhibits high reliability. Further, the reliability of the output values was verified with new input data, and the results showed high accuracy.