• Journal of the Korean Geosynthetics Society
• /
• v.12 no.2
• /
• pp.35-42
• /
• 2013

Recently, construction of reinforced earth structure using geosynthetics has been increased because it has advantages such as construction efficient, cost effectiveness and appearance aspect against existing gravity or cantilever retaining wall. However due to the climate change in Korea excessive inflow of ground water and surface water from heavy rainfall could affect the stability of reinforced retaining wall seriously. So the discharge capacity of drains should be evaluated by using experimental method in the design of reinforced earth wall. In this study, instead of concrete block used in most of the retaining wall, eco-friendly porous soilbag was used. This paper describes the test method and result of the laboratory testing for determination of discharge capacity utilizing PBDs.

• Journal of the Korean GEO-environmental Society
• /
• v.5 no.1
• /
• pp.5-12
• /
• 2004

Soft foundation is extensively distributed in coastal areas including our local regions. Embankment load on such soft foundation causes displacement due to lack of base ground supports. Long-term consolidation can result in settlement and destruction of shear failure and structure. Therefore, a variety of vertical drain methods are applied to construction sites to prevent base from breaking and changing for secure construction. This study analyzed the patterns of changes displacement to determine efficient range of improvement since range of vertical drain material determines vertical and horizontal changes based on the width range of under ground improvement. Changes of intensity with distance from embankment edge were also analyzed in the field study of embankment slope.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.32 no.6C
• /
• pp.239-247
• /
• 2012

Some methods were proposed to predict lateral flow due to embankments for road constructions on soft grounds, in which vertical drains were placed. In order to investigate the prediction methods of lateral flow, 200 field monitoring data for embankments in thirteen road construction sites at western and southern coastal areas of the Korean Peninsula were analyzed. For analyzing the relationship between the safety factor of embankment slope and the horizontal displacement in soft grounds where horizontal drain mats were placed, it was reliable to apply the maximum horizontal displacement in soft ground instead of the horizontal displacement at ground surface. The maximum horizontal displacement was developed less than 50mm in fields where the safety factor of slope was more than 1.4, while the one was developed more than 100mm in fields where the safety factor of slope was less than 1.2. In safe fields where the maximum horizontal displacement were developed within 50mm, lateral flow would not happen since shear deformation was not appeared. On the other hand, shear failure would happen in the fields where the maximum horizontal displacement were developed more than 100mm. In such fields, embankments might be continued after some appropriate countermeasures should be prepared. Safe embankments can be performed on soft grounds, in which the stability number is less than 3.0 and the safety factor for bearing is more than 1.7. However, if the stability number is more than 4.3 and the safety factor for bearing is less than 1.2, shear deformation would begin and even shear failure would happen.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.8 no.2
• /
• pp.123-136
• /
• 2004

Terzaghi's one-dimensional consolidation theory has some important assumption, which can't be applicable to predict the behavior of soft clay ground. Especially, predictions using infinitesimal strain and linear material function related with permeability can give rise to mistake in comparison with the result of real behavior in site. For this reason, Gibson et al. established a rigorous formulation for the one-dimensional nonlinear finite strain consolidation theory, which can consider non-linearity of material function. But it is difficult to apply this theory to predict the behavior of common soft clay ground with vertical drain. In this study, consolidation model which can consider the vertical and horizontal flow of a fully saturated clay layer, self-weight of soil and nonlinear characteristics of compressibility and permeability are derived. Numerical analysis scheme, which can be applied to consolidation analysis by derived consolidation model in this study was developed. The characteristics of material function were examined using laboratory testing such as standard consolidation test, Rowe-cell test and modified consolidation test.

• Journal of the Korean Geosynthetics Society
• /
• v.9 no.2
• /
• pp.1-9
• /
• 2010

At present, the sand mat method is actively used for improvement of soft ground. But, there are some problems related with sand mat which has been used as a way to accelerate consolidation settlement. First of all, insufficiency of sand due to imbalances in market supply and demand is the one of the biggest problems, which makes price high of sand and delays a term of total construction work. Moreover, it is necessary to preserve integrity of environment from natural disruption caused by indiscreet quarrying and dredging operation to supply sand for soil improvement construction site. This paper presents the feasibility study to use of Precious Slag Ball instead of sand mat as the replacing material through the basic soil property tests, the medium of discharge capacity test and analysis of settlement property. It is also evaluates the performance of Precious Slag Ball as a sand mat in terms of discharge capacity, ground settlement by the K-Embank program based on field experimental work.

• Journal of the Korean GEO-environmental Society
• /
• v.13 no.3
• /
• pp.29-37
• /
• 2012

This study is to find out the characteristics of the behavior of Geosyntehtic Reinforced Retaining Earth Wall(GRREW) through the laboratory experiment with the reduced-scale model, and to verify the effect of reinforcement by materials of GRREW. The loading tests after combining nonwoven geosynthetic, re-bar mesh nets and drainage blocks respectively among the components of the GRREW were performed in three cases of their slopes. In the cases of the behavior analysis including all of the components of the GRREW, the maximum horizontal displacement was generated 8.4mm at the location of 0.57H in the slope of 1:0.3; 3.8mm at the location of 0.57H in the slope of 1:0.6; 3.6mm at the location of 0.86H in the slope of 1:1.0. On average, the horizontal displacements of the GRREW were reduced by 83.8% against those of the original slopes. Lastly, seepage analysis and slope stability analysis were performed by modelling section of field, to confirm the effect of installation of drainage block in GRREW. We can confirm to compare increasing the slope safe factor and decreasing ground water in accordance with drainage blocks.

• Journal of the Korean GEO-environmental Society
• /
• v.11 no.9
• /
• pp.55-60
• /
• 2010

This study are carried out to an lab model tests to develop a construction method that solidifies high-water content cohesive soil by using filter type drain and vacuum pressure, and that stabilizes the ground by accelerating horizontal drain at incline or in tunnel. The calibration chamber was designed within length of 1.5m and height of 50cm, and a drainage hole for preconsolidation, a switchgear and a piezometer were installed at the bottom part of the chamber. Also, a settlement gage was installed at the top part so that it can measure the settlement by time. The calibration ground basis was made in a form of thin layer from kaolinite and bentonite in 9:1 ratio stirred at 130% water content condition. A filter type drain was installed at chamber center and a vacuum pressure of 0.8MPa was applied through a hose linked to the cap at the top part, then, the settlement was measured in every 1 hour interval. After experiment, the moisture contents were measured by position, then, verified the increase of solidity of the ground through a triaxial compression test on undisturbed profile. After 11 days from the effective date, it was observed that the settlement decreased by maximum 35mm and the water content ratio was reduced by 38% at most while the solidity of the ground increased by 5~8 times greater than before preconsolidation.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2005.10a
• /
• pp.174-187
• /
• 2005

Recently, because of environment, cost, supply and demand factors, though applying sea-sand as horizontal drains is getting difficult that usage of Gravel has been growing in large size of construction sites, Study on engineering properties and behavior characteristics of Gravel stratum is not thoroughgoing enough. We have applied Gravel Mat as the horizontal drains in O O construction site. We also conducted several field tests such as Material property test, Geosynthetics damage test with Repeated load, Discharge capacity test performed by inflow of upper soil and In-situ PBD Penetration test to review the application of Gravel Mat. Test results show that Gravel Mat is not only advantageous in Trafficability and Water drainage by Consolidation due to its great Internal friction angle and Permeability, but also easy to penetrate with Mandrel and has great discharge capacity and guarantee of the stability against geosynthetics damage at the same time. With these benefits Gravel Mat shows great application in fields.

• Journal of the Korean Geotechnical Society
• /
• v.16 no.6
• /
• pp.43-50
• /
• 2000

충북단양군 영춘면 휴석동 지역에 위치한 위험사면은 1972년 456mm의 집중강우에 의해 사면붕괴가 발생하여 가옥 2채붕괴 등의 피해를 유발시켰으며, 지속적인 지반침하가 진행되고 있다. 남한강 하류에 접하고 있는 상기의 위험사면은 산사태에 의한 토사의 이동시 남한강을 덮치게 되어 그 유로의 변화를 일으켜 영춘면의 지역의 침수피해의 대규모의 재해를 일으킬 수 있는 위험성이 내재되어 있다. 본 연구는 상기 위험사면에 대한 지반조사, 지하수 특성 조사 등을 통해 붕적토 사면의 안정해석을 수행하여 최적의 조강 대책안을 제시하고 이에 따른 재해 예방을 도모하고자 한다. 보강대책을 붕적토 사면의 거동특성과 위험사면의 지형적 특성 등을 고려하여 집수정, 수평배수공, 앵커공 및 보강토 옹벽의 복합공법에 의해 위험사면의 안정성을 확보하는 방안을 제안하였다.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2009.09a
• /
• pp.1158-1163
• /
• 2009

In this study, PSD system to improve the soft ground was developed by using a horizontal drainage pipe. PSD system is direct drain method for the disappearance of excess pore-water pressure which is caused by fill on soft ground. To conduct the field test construction in order to evaluate application of the PSD system. To estimate the behavior characteristics on settlement in which constructed by PSD system and compared the behavior characteristics with the conventional soft ground improvement method result.