• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.3
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• pp.229-242
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• 2009

Numerical analysis has been performed to estimate maximum settlement, maximum horizontal displacement and total settlement volume at the ground surface due to tunnel excavation varying ground condition, tunnel depth and diameter, and construction condition (volume loss at excavation face). The maximum surface settlement from the numerical analysis has been compared with the maximum settlement at tunnel crown considering ground condition, tunnel depth and diameter, and construction condition, and it has been also compared with the maximum horizontal displacement. In addition, the volume loss ($V_L$) at tunnel excavation face has been compared with the total surface settlement volume ($V_s$) with the variation of ground condition, tunnel depth, and tunnel diameter. The results from the numerical analysis have been compared with field measurements to confirm the applicability and validity of the results and by this comparison it is believed that the numerical results in this study can be utilized practically in analyzing the ground movements due to tunnel excavation.

• Journal of agriculture & life science
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• v.45 no.2
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• pp.1-7
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• 2011

Three evergreen ground-cover species were tested and evaluated for cold acclimation with different lights in central Korea to enrich the varieties of ground cover plants for over-wintering. Nandina domestica which recently started to be planted in central Korea had high chlorophyll unit with shade condition in both locations, Banpo and Gwacheon during winter. Light condition had no influence on chlorophyll unit in Banpo after April, meanwhile full sun condition decreased chlorophyll unit significantly in Gwacheon, which is exposed to cold wind from north. Ophiopogon japonicas had more than double chlorophyll unit in shade condition compared to that in full light condition in both investigation areas in February. In addition, higher value of L and b in shade condition had been maintained than in full sun condition throughout investigation period. However, leaves in Gwacheon were de-colorized in full sun condition after over-wintering. Pachysandra terminalis had more higher chlorophyll unit in shade condition compared to in full sun condition in both investigation areas in February. But light conditions had not effect the difference of chlorophyll unit of Gwacheon in April. Therefore, The present results suggest that evergreen ground covers with shade condition would be used as landscape materials in the capital area.

• Interaction and multiscale mechanics
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• v.5 no.1
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• pp.75-90
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• 2012

This paper investigates the effects of sports ground materials on the transfer characteristics of the landing impact force using a coupled foot-shoe-ground interaction model. The impact force resulting from the collision between the sports shoe and the ground is partially dissipated, but the remaining portion transfers to the human body via the lower extremity. However, since the landing impact force is strongly influenced by the sports ground material we consider four different sports grounds, asphalt, urethane, clay and wood. We use a fully coupled 3-D foot-shoe-ground interaction model and we construct the multi-layered composite ground models. Through the numerical simulation, the landing impact characteristics such as the ground reaction force (GRF), the acceleration transfer and the frequency response characteristics are investigated for four different sports grounds. It was found that the risk of injury, associated with the landing impact, was reduced as the ground material changes from asphalt to wood, from the fact that both the peak vertical acceleration and the central frequency monotonically decrease from asphalt to wood. As well, it was found that most of the impact acceleration and frequency was dissipated at the heel, then not much changed from the ankle to the knee.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.5
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• pp.381-389
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• 2011

In this study, we are focusing our attention on lift characteristics of the low aspect wings for Wing-In Ground effect crafts (WIG). Experimental measurements at an open-type wind tunnel are carried out and results are comparatively presented. In order to simulate the realistic ground condition in where the WIG craft is flying, moving ground is implemented by a conveyor belt rotating with the same velocity of the inflow. We consider two different wings (NACA0012 and DHMTU section) which have four different aspect ratios (0.5, 1.0, 1.5 and 2.0). Forces acting on the wings are measured and lift characteristics are elaborately investigated for various different conditions. In addition, end-plate effects are estimated. Results are validated by comparing with theoretic solutions of the symmetric airfoil. Present results show that ground effects are differently generated in moving or fixed ground conditions, and hence left characteristics are affected by the ground condition. Consequently, accurate aerodynamic forces acting on the WIG craft are guaranteed in a realistic moving ground condition.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.6
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• pp.386-394
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• 2019

In this study, according to drainage condition (undrained and drained) in ground, the settlement and horizontal displacement of caisson quay wall and apron in Yeongilman port due to excess pore water pressure in ground induced by the magnitude 5.4 earthquake in Pohang on November 15, 2017. In general, seismic response analysis was carried out under undrained drainage condition, but in this study, drain drainage analysis was conducted to estimate displacement during earthquake as well as an additional displacement due to dissipation of excess pore water pressure after earthquake. The result of after earthquake can not be known under undrained drainage condition. Results cleary showed that the behavior of structure and ground was dependent on drainage condition in ground. Especially, based on the drained drainage condition, the additional displacement was clearly detected due to dissipation of excess pore water pressure after earthquake. Which indicates that both results are different to drainage condition in ground, and therefore, drainage condition analysis is necessary to accurately estimate the behavior of ground and structure in seismic response analysis.

• Journal of Biosystems Engineering
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• v.35 no.4
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• pp.231-238
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• 2010

The purpose of this paper was to investigate experimentally the steering torque characteristics of a tractor operated in various ground conditions. The experiments were conducted with the tractor reconstructed for steering torque test of the tractor at two different off-road conditions (ground-I and ground-II) and a on-road condition (ground-III), three different levels of tire inflation pressures (69 kPa, 138 kPa and 207 kPa), and four different levels of axle loads (4120 N, 4730 N, 5340 N and 5950 N). The results of this study are summarized as follows: 1) The steering torque was increased with the increase in steering angle for all experimental levels of ground conditions, axle loads and inflation pressures of tire. 2) As the axle load increased, the steering torque of the tractor increased for all ground conditions, and the increasing rate of the steering torque with the increase of axle load was greater at on-road than at off-road. 3) As the tire inflation pressure decreased, the steering torque increased. Also the increasing tendency of the steering torque with decreasing the tire inflation pressure showed that the harder the ground was, the larger the effect was. But for the soft ground condition, ground-I, no specific trend with inflation pressures was found. 4) Steering angle-steering torque relationship with ground conditions showed that the increasing rate of the steering torque was greater at on-road than off-road for small steering angle under 10 degree, and was greater at off-road than on-road for large steering angles over 10 degree.

• Journal of the Korean Geosynthetics Society
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• v.19 no.3
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• pp.35-44
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• 2020

This study described the result of laboratory model tests, in order to compare the improvement effect of the DCM column installed on the soft ground according to DCM column type. In the laboratory model test, the non-reinforced type and the 3 types of DCM column were applied, and the behavior (settlement, lateral flow) of soft ground was evaluated under the surcharge load condition for each type. The settlement evaluation result showed that the settlement of soft ground without DCM column occurred rapidly under the low load condition, but the settlement of the soft ground with the DCM column had relatively small settlement. The evaluation result of lateral flow in the soft ground showed that the soft ground with DCM column had lower lateral displacement than the soft ground without DCM column. Especially, the lateral displacement under the same load condition decreased in the order of pile type, wall type, and grid type. Therefore, it confirmed that the improvement effect of soft ground was excellent when the DCM of grid type was applied for settlement and lateral flow.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.660-670
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• 2009

Neighboring construction becomes mainstream of Ground excavation in downtown area. This causes the displacement, deformation, stress condition, etc of the ground surroundings. Therefore Neighboring construction have an effect on Neighboring structure. All these years a lot of Neighboring construction carried out, and the accumulation of technology also get accomplished. But earth retaining structure collapse happens yet. Types of earth retaining structure collapse are 12. 1. Failure of anchor or strut system, 2. Insufficiency of penetration, 3. H-pile Failure on excessive bending moment, 4. Slope sliding failure, 5. Excessive settlement of the back, 6. Deflection of H-pile, 7. Joint failure of coupled H-pile, 8. Rock failure when H-pile penetration is rock mass, 9. Plane arrangement of support systems are mechanically weak, 10. Boiling, 11. Heaving, 12. Over excavation. But field collapses are difficult for classification according to the type, because collapse process are complex with various types. When we consider the 12 collapse field, insufficient recognition of ground condition is 4 case. Thorough construction management prevents from fault construction. For limitations of soil survey, It is difficult to estimate ground condition exactly. Therefore, it should estimate the safety of earth retaining system, plan for necessary reinforcement, according to measurement and observation continuously.

• Geomechanics and Engineering
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• v.33 no.5
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• pp.463-475
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• 2023

Tunnel construction activity, conducted mainly in mountains and within urban centres, causes soil settlement, thus requiring the relevant management of slopes and structures as well as evaluations of risk and stability. Accordingly, in this study we performed a three-dimensional finite element analysis to examine the behaviour of piles and pile cap stability when a tunnel passes near the bottom of the foundation of a pile group connected by a pile cap. We examined the results via numerical analysis considering different conditions for reinforcement of the ground between the tunnel and the pile foundation. The numerical analysis assessed the angular distortion of the pile cap, pile settlement, axial force, shear stress, relative displacement, and volume loss due to tunnel excavation, and pile cap stability was evaluated based on Son and Cording's evaluation criterion for damage to adjacent structures. The pile located closest to the tunnel under the condition of no ground reinforcement exhibited pile head settlement approximately 70% greater than that of the pile located farthest from the tunnel under the condition of greatest ground reinforcement. Additionally, pile head settlement was greatest when the largest volume loss occurred, being approximately 18% greater than pile head settlement under the condition having the smallest volume loss. This paper closely examines the main factors influencing the behaviour of a pile group connected by a pile cap for three ground reinforcement conditions and presents an evaluation of pile cap stability.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.268-275
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• 2006

Excavation works of cylindrical shafts and tunnels for the construction of a variety of infrastructures have been frequently going on in the urban areas. When ground excavations of cylindrical shafts and shallow tunnels proceed in the ground condition of high water level and silt particle component, ground water drawdown involving soil particle migration causes loosening of ground around tunnels and shafts, causes settlement and deformation of ground. Damages due to ground sinking and differential settlement can occur in the adjacent ground and structures. The extent and possibility of damage relevant to ground water drawdown and soil particle migration can't be so precisely expected in advance that we will face terrible damages in case of minor carefulness. This paper introduces two examples of construction management where using incremental deformation graph of inclinometer, we noticed the possibility of soil migration due to ground water drawdown in the excavation process of vertical shaft and shallow tunnel, analysed a series of measurement data in coupled connection, properly prepared countermeasures, so came into safe and successful completion of excavation work without terrible damages. The effort of this article aims to improve and develop the technique of design and construction in the coming projects having similar ground condition and supporting method.