woongju mun - Academia.edu (original) (raw)
Papers by woongju mun
Tunnelling and Underground Space Technology, 2006
Reinforcing effect of bolt system in cohesionless soils was studied. The laboratory model tests w... more Reinforcing effect of bolt system in cohesionless soils was studied. The laboratory model tests were carried out for the simple beam model, which was built by sand and reinforced by bolts with various lengths, distances, and types. Stiffness of the test beam was calculated from the measured deflection. Experiment results showed that bolt distance gaves more contribution to the reinforcing effect than the bolt length did. It also showed that the fully grouted bolts were more effective than the end bearing bolts. As conclusion, reinforcing effect of the bolt system could be estimated from the test beam stiffness, which increases the apparent Young's modulus. (A) This paper was presented at Safety in the underground space - Proceedings of the ITA-AITES 2006 World Tunnel Congress and the 32nd ITA General Assembly, Seoul, Korea, 22-27 April 2006. For the covering abstract see ITRD E129148. "Reprinted with permission from Elsevier".
Geotechnical and Geological Engineering, 2017
This paper involves an evaluation of a relationship describing the evolution in yield 4 stress of... more This paper involves an evaluation of a relationship describing the evolution in yield 4 stress of unsaturated soils during hydraulic hysteresis, and an application of this relationship in an 5 elasto-plastic framework to predict the compression curves of unsaturated soils under drained (free 6 outflow of air and water with constant suction) or undrained (constant water content with no 7 outflow of water and varying suction) conditions. The yield stress was quantified as the apparent 8 mean effective preconsolidation stress obtained from compression tests reported in the literature 9 on specimens that had experienced different hydraulic paths. It was observed that the 10 preconsolidation stress does not follow a hysteretic path when plotted as a function of matric 11 suction, but does when plotted as a function of the degree of saturation. Accordingly, an existing 12 logarithmic relationship between the preconsolidation stress and matric suction normalized by the 13 air entry suction was found to match the experimental preconsolidation stress results. This same 14 relationship was also able to satisfactorily predict the trends in preconsolidation stress with degree 15 of saturation by substituting the hysteretic soil-water retention curve (SWRC) into the place of the 16 matric suction. The relationship between preconsolidation stress and suction was combined with 17 an elasto-plastic framework to predict the compression curves of soils during drained compression, 18 while the wetting-path relationship between preconsolidation stress and degree of saturation was 19
Canadian Geotechnical Journal, 2015
This paper investigates the compression behavior of unsaturated clay under mean stresses up to 16... more This paper investigates the compression behavior of unsaturated clay under mean stresses up to 160 MPa and different drainage conditions. A new isotropic pressure cell was developed that incorporates matric suction control using the axis-translation technique, and a high-pressure syringe pump operated in displacement-control mode was used to control the total stress and track specimen volume changes. In addition to presenting results from characterization tests on the cell, results from a series of isotropic compression tests performed on compacted clay specimens under drained and undrained conditions are presented. These results permit evaluation of the hardening mechanisms and transition points in the compression curve with increasing effective stress. As expected, specimens tested under undrained conditions were much stiffer than those tested under drained conditions. In the drained tests, the rate of compression was sufficient to permit steady-state dissipation of excess pore-wa...
Soils and Foundations
Unconsolidated-undrained (UU) triaxial compression tests were performed on low-4 plasticity clay ... more Unconsolidated-undrained (UU) triaxial compression tests were performed on low-4 plasticity clay specimens compacted to the same void ratio but different initial degrees of 5 saturation to evaluate the impact of axial strain rates ranging from 0.1 to 150 %/min on the 6 undrained shear strength. Although an effective stress analysis cannot be performed on the 7 results, they are useful to evaluate the relative roles of initial hydraulic conditions (i.e., matric 8 suction and degree of saturation) and compaction effects (i.e., potential changes in soil structure 9 with compaction water content). This evaluation is relevant due to difficulty in measuring shear-10 induced pore water and air pressures in consolidated-undrained (CU) compression tests on 11 unsaturated clay. In all tests, the undrained shear strength quantified as the maximum principal 12 stress difference increased log-linearly with axial strain rate, with rates of increase ranging from 13 4.1 to 9.7% per log cycle of axial strain rate for specimens having initial degrees of saturation 14 ranging from 0.99 to 0.59. The undrained shear strength, rate of increase in undrained shear 15 strength with axial strain rate, and secant moduli all increased nonlinearly with decreasing initial 16 degree of saturation, although compaction effects played an important role in these trends. The 17 increase in undrained shear strength with axial strain rate can be attributed to a reduction in the 18 magnitude of excess pore water pressure, with similar reductions in magnitude for all the degrees 19 of saturation considered. A comparison between the measured undrained shear strength values 20
Journal of Geotechnical and Geoenvironmental Engineering, Oct 1, 2017
The roles of particle breakage and drainage conditions on the quasi-static compression response o... more The roles of particle breakage and drainage conditions on the quasi-static compression response of sand were evaluated by comparing the results from drained and undrained isotropic compression tests on dry and saturated specimens up to a mean total stress of 160 MPa. For dry sand specimens, the compression curves from drained and undrained tests were similar due to the high compressibility of air. The isotropic compression curves of the dry sand specimens at mean stresses greater than 30 MPa reflect a transition toward void closure, reaching a minimum void ratio of 0.04 at 160 MPa. Dry sand specimens with different initial relative densities showed similar behavior during isotropic compression in drained conditions for mean stresses greater than approximately 30 MPa. As expected, saturated specimens tested under undrained conditions showed a much stiffer response than in drained conditions, with a bulk modulus greater than that of water. Increasing trends in particle breakage quantified using the breakage factors of Marsal and Hardin with increasing mean stress were observed for the dry sand specimens, but negligible particle breakage was noted for the saturated specimens tested in undrained conditions. To highlight the linkage between particle breakage and the transition to void closure at high mean effective stress, an empirical relationship was developed using Hardin's relative breakage index to match the experimentally-derived compression curves of dry sands under drained conditions.
Journal of Geotechnical and Geoenvironmental Engineering
Journal of Geotechnical and Geoenvironmental Engineering, Apr 1, 2017
This paper proposes a constitutive model to describe the isotropic compression response of unsatu... more This paper proposes a constitutive model to describe the isotropic compression response of unsaturated, compacted clay under undrained conditions over a wide range of mean stresses. The total stress-based model captures the impacts of the initial degree of saturation on the apparent preconsolidation stress and the slope of the compression curve up to the point of pressurized saturation. The points of pressurized saturation for specimens with different initial degrees of saturation were predicted using a modified form of Hilf's pore pressure analysis. The compression response for pressure-saturated specimens was dominated by the pore water, although dissolved air and soil structure may play a role for some soils. The model was calibrated using results from a series of compression tests on compacted clay specimens having initial degrees of saturation ranging from 0.6 to 1.0 and the same initial void ratio. The model was found to provide a good match to the experimental data for mean stresses up to 160 MPa, in particular due to the improvements in Hilf's analysis to evaluate the points of pressurized saturation.
Tunnelling and Underground Space Technology, 2006
Reinforcing effect of bolt system in cohesionless soils was studied. The laboratory model tests w... more Reinforcing effect of bolt system in cohesionless soils was studied. The laboratory model tests were carried out for the simple beam model, which was built by sand and reinforced by bolts with various lengths, distances, and types. Stiffness of the test beam was calculated from the measured deflection. Experiment results showed that bolt distance gaves more contribution to the reinforcing effect than the bolt length did. It also showed that the fully grouted bolts were more effective than the end bearing bolts. As conclusion, reinforcing effect of the bolt system could be estimated from the test beam stiffness, which increases the apparent Young's modulus. (A) This paper was presented at Safety in the underground space - Proceedings of the ITA-AITES 2006 World Tunnel Congress and the 32nd ITA General Assembly, Seoul, Korea, 22-27 April 2006. For the covering abstract see ITRD E129148. "Reprinted with permission from Elsevier".
Geotechnical and Geological Engineering, 2017
This paper involves an evaluation of a relationship describing the evolution in yield 4 stress of... more This paper involves an evaluation of a relationship describing the evolution in yield 4 stress of unsaturated soils during hydraulic hysteresis, and an application of this relationship in an 5 elasto-plastic framework to predict the compression curves of unsaturated soils under drained (free 6 outflow of air and water with constant suction) or undrained (constant water content with no 7 outflow of water and varying suction) conditions. The yield stress was quantified as the apparent 8 mean effective preconsolidation stress obtained from compression tests reported in the literature 9 on specimens that had experienced different hydraulic paths. It was observed that the 10 preconsolidation stress does not follow a hysteretic path when plotted as a function of matric 11 suction, but does when plotted as a function of the degree of saturation. Accordingly, an existing 12 logarithmic relationship between the preconsolidation stress and matric suction normalized by the 13 air entry suction was found to match the experimental preconsolidation stress results. This same 14 relationship was also able to satisfactorily predict the trends in preconsolidation stress with degree 15 of saturation by substituting the hysteretic soil-water retention curve (SWRC) into the place of the 16 matric suction. The relationship between preconsolidation stress and suction was combined with 17 an elasto-plastic framework to predict the compression curves of soils during drained compression, 18 while the wetting-path relationship between preconsolidation stress and degree of saturation was 19
Canadian Geotechnical Journal, 2015
This paper investigates the compression behavior of unsaturated clay under mean stresses up to 16... more This paper investigates the compression behavior of unsaturated clay under mean stresses up to 160 MPa and different drainage conditions. A new isotropic pressure cell was developed that incorporates matric suction control using the axis-translation technique, and a high-pressure syringe pump operated in displacement-control mode was used to control the total stress and track specimen volume changes. In addition to presenting results from characterization tests on the cell, results from a series of isotropic compression tests performed on compacted clay specimens under drained and undrained conditions are presented. These results permit evaluation of the hardening mechanisms and transition points in the compression curve with increasing effective stress. As expected, specimens tested under undrained conditions were much stiffer than those tested under drained conditions. In the drained tests, the rate of compression was sufficient to permit steady-state dissipation of excess pore-wa...
Soils and Foundations
Unconsolidated-undrained (UU) triaxial compression tests were performed on low-4 plasticity clay ... more Unconsolidated-undrained (UU) triaxial compression tests were performed on low-4 plasticity clay specimens compacted to the same void ratio but different initial degrees of 5 saturation to evaluate the impact of axial strain rates ranging from 0.1 to 150 %/min on the 6 undrained shear strength. Although an effective stress analysis cannot be performed on the 7 results, they are useful to evaluate the relative roles of initial hydraulic conditions (i.e., matric 8 suction and degree of saturation) and compaction effects (i.e., potential changes in soil structure 9 with compaction water content). This evaluation is relevant due to difficulty in measuring shear-10 induced pore water and air pressures in consolidated-undrained (CU) compression tests on 11 unsaturated clay. In all tests, the undrained shear strength quantified as the maximum principal 12 stress difference increased log-linearly with axial strain rate, with rates of increase ranging from 13 4.1 to 9.7% per log cycle of axial strain rate for specimens having initial degrees of saturation 14 ranging from 0.99 to 0.59. The undrained shear strength, rate of increase in undrained shear 15 strength with axial strain rate, and secant moduli all increased nonlinearly with decreasing initial 16 degree of saturation, although compaction effects played an important role in these trends. The 17 increase in undrained shear strength with axial strain rate can be attributed to a reduction in the 18 magnitude of excess pore water pressure, with similar reductions in magnitude for all the degrees 19 of saturation considered. A comparison between the measured undrained shear strength values 20
Journal of Geotechnical and Geoenvironmental Engineering, Oct 1, 2017
The roles of particle breakage and drainage conditions on the quasi-static compression response o... more The roles of particle breakage and drainage conditions on the quasi-static compression response of sand were evaluated by comparing the results from drained and undrained isotropic compression tests on dry and saturated specimens up to a mean total stress of 160 MPa. For dry sand specimens, the compression curves from drained and undrained tests were similar due to the high compressibility of air. The isotropic compression curves of the dry sand specimens at mean stresses greater than 30 MPa reflect a transition toward void closure, reaching a minimum void ratio of 0.04 at 160 MPa. Dry sand specimens with different initial relative densities showed similar behavior during isotropic compression in drained conditions for mean stresses greater than approximately 30 MPa. As expected, saturated specimens tested under undrained conditions showed a much stiffer response than in drained conditions, with a bulk modulus greater than that of water. Increasing trends in particle breakage quantified using the breakage factors of Marsal and Hardin with increasing mean stress were observed for the dry sand specimens, but negligible particle breakage was noted for the saturated specimens tested in undrained conditions. To highlight the linkage between particle breakage and the transition to void closure at high mean effective stress, an empirical relationship was developed using Hardin's relative breakage index to match the experimentally-derived compression curves of dry sands under drained conditions.
Journal of Geotechnical and Geoenvironmental Engineering
Journal of Geotechnical and Geoenvironmental Engineering, Apr 1, 2017
This paper proposes a constitutive model to describe the isotropic compression response of unsatu... more This paper proposes a constitutive model to describe the isotropic compression response of unsaturated, compacted clay under undrained conditions over a wide range of mean stresses. The total stress-based model captures the impacts of the initial degree of saturation on the apparent preconsolidation stress and the slope of the compression curve up to the point of pressurized saturation. The points of pressurized saturation for specimens with different initial degrees of saturation were predicted using a modified form of Hilf's pore pressure analysis. The compression response for pressure-saturated specimens was dominated by the pore water, although dissolved air and soil structure may play a role for some soils. The model was calibrated using results from a series of compression tests on compacted clay specimens having initial degrees of saturation ranging from 0.6 to 1.0 and the same initial void ratio. The model was found to provide a good match to the experimental data for mean stresses up to 160 MPa, in particular due to the improvements in Hilf's analysis to evaluate the points of pressurized saturation.