• Journal of the Korean Geotechnical Society
• /
• v.17 no.6
• /
• pp.37-46
• /
• 2001

Pile load tests were carried out to investigate the contribution of the pile cap to the carrying capacity of a pile group and load transfer characteristics of piles in the group. A group of 24 piles$(4 \times6 array)$ of 92.5mm diameter steel pipe were installed to the depth of 3m fron the ground surface, the top of weathered rock. A maximum load of 320ton was applied to the pile cap, $1.5\times2.3m$, in contact with the ground surface. At the maximum load of 320ton, the pile cap has carried 22% of the total load. Average ultimate capacity of pile in the pile group was estimated to be 16.4ton, substantially higher than that of single pile, installed at the corner and tested before pile cap construction. For the same magnitude of settlement, the pile in the center carried less load than the pile at the perimeter due to strain superposition effect. Piles in the group showed almost constant contribution(approx. 60%) of side friction to the total capacity for all of the loading stages, while that of single pile decreased from 82% to 65%.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.36 no.4
• /
• pp.705-713
• /
• 2016

For the soft ground construction, the factors not considered in the design stage occurs in the construction stage so that they cause the increase of the construction cost due to the structural stability and the design change. The subject of the study is the construction section of the industrial complex access road made in the Ochang region of Chungcheongbuk-do. The study is concerned with selecting the soft ground handling method such as the replacement method using rock debris and the surcharge reflecting the service load as the soft ground handling measure and analyzing the effect of reducing the construction cost with the stability of structures and the reduction of the construction period. The soft ground in the study section consists of sandy and cohesive soil and is 2.4m to 5.5m deep. It is distributed unevenly between the 1.5m to 5.9m stratums under the ground surface. Settlement is not serious, but the future uneven settlement and difference are expected so that the future settlement behavior is estimated by analyzing the site measurement results after the soft ground treatment. Moreover, in consideration of the regional characteristics and economic efficiency, soil with good quality is replaced with rock debris as the replacement material so that 29% of the construction cost is reduced due to the increase of stability and the reduction of duration. If the estimation of the dispersion of the pore water pressure within the dam body and the change of the underground water level and the relation of the actually measured soft ground with consolidation is studied further on the basis of the study, it is expected that the behavior of the soft ground will be correctly estimated in various site conditions.

• Journal of the Korean Geotechnical Society
• /
• v.28 no.6
• /
• pp.31-38
• /
• 2012

In this present study, the long-term consolidation tests were performed using the remolded Kwang-Yang port clayey soil to clarify the effect of stress history and over-consolidation ratio (OCR) on the long-term consolidation characteristics of the soft clayey soil. For the over-consolidated state clayey soils, in case OCR exceeds 1.5, there are no great differences of secondary consolidation settlement and final settlement even if OCR increases from 2.0 to 3.0. Therefore, it has been understood that the value of OCR applied on the field site to reduce the secondary consolidation settlement and the final settlement is about 1.5. In addition, in order to investigate the relationship between the pre-loading period and the characteristics of long-term consolidation behavior obtained from the test results using the remolded Kwang-Yang port clayey soils, the influence on long-term consolidation behavior was not large though the pre-load was unloaded with the consolidation degree 70~80% exceeded.

• Journal of the Korean GEO-environmental Society
• /
• v.2 no.4
• /
• pp.63-72
• /
• 2001

As construction cases on soft ground are increasing, the necessity of ground improvement is also increasing. Granular pile is one of the methods for soft clay and for loose sandy soil. In our country, SCP(Sand Compaction Pile) method using sand material has been mainly used to improve soft ground, but Granular pile with crushed-stone was not used much. However, alternative material such that crushed-stone is needed to substitute for sand due to the environmental and economical problems. In this study, staged load test and consolidation test were performed in the laboratory to observe the behavior of soft ground improved by Granular pile. In order to evaluate the characteristics such as bearing capacity, drainage, and settlement, sand and crushed-stone were applied as each pile material. The test results show that crushed-stone has higher bearing capacity and less settlement than those of sand under similar pore water pressure condition. Therefore, crushed-stone is determined to be appropriate as substitute for sand.

• Journal of Industrial Technology
• /
• v.18
• /
• pp.405-415
• /
• 1998

This thesis is an experimental and numerical research on bearing capacity acting retaining walls close to rigid slopes with stiff angles. Experiments were performed with changing the roughness of adjacent slope to the wall, its inclination, distance between wall and slope. Vertical stress and applied surcharge loads were measured by miniature earth cells and a load cel respectively. Stress distribution Vertical Settlement of surcharge load of rigid model footing were measured by LVDTs. Bearing capacities of surcharge loads were compared with theoretical estimations by using several different methods of limit equilibrium and numerical analysis. For limit equilibrium methods, the modified silo and the wedge theories, proposed by Chung sung gyo and Chung in gyo (1994) were used to analyze test results Based on those modified theories, the particular solution with the boundary condition of surcharge loads on the surface of backfill was obtained to find the stress distributions acting in the backfill and to compare with test results. From results of surcharge test with model wall being very close to the slope, analyzed results by the modified silo theory and to be in the better agreements than other methods.

• Geomechanics and Engineering
• /
• v.10 no.1
• /
• pp.95-107
• /
• 2016

Deep soil mixing with cement and cement-lime mixtures has been widely used for decades to improve the strength of soils. In this study, small-scale laboratory model tests of polymer columns in soft clayey soil were conducted to evaluate the feasibility of using various polymeric compounds as binders in deep soil mixing. Floating and end bearing polymer columns were used to examine the load-settlement relationship of improved soft clayey soils for various area replacement ratios. The results indicate that polymer columns show good promise for use in deep mixing applications.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2000.11a
• /
• pp.269-276
• /
• 2000

Granular compaction piled raft systems have been effectively used in soft ground foundation to improve not only settlement but also bearing capacity. In the present study, to examine the behavior characteristics and bulging failure zone on granular compaction piled raft system, carbon rod tests have been performed. The test results are compared with the zone of bulging failure and the effects of pile-pile interaction obtained from the analytical approaches. In addition, parametric studies are peformed with considering pile slenderness ratio, Poisson's ratio and load sharing ratio.

• Journal of the Korean Society for Railway
• /
• v.9 no.3 s.34
• /
• pp.298-304
• /
• 2006

An active application of concrete track is being expected for the future constructions of Korean railroad. For the successful concrete track construction and design in earthwork areas, the roadbed behavior should be reasonably estimated using the proper analysis method. In this paper, behaviors of concrete track on the reinforced roadbed constructed with the standard stiffness and depth were estimated thorough numerical analyses and field measurements. A three dimensional finite difference method was employed to model the concrete tracks and subground. The settlement and vertical pressures caused by train load were estimated by the numerical method and compared with the field measurement results. The bearing characteristics of roadbed were presented and the proper method for the analysis of concrete track was proposed.

• Journal of the Korean Geotechnical Society
• /
• v.30 no.4
• /
• pp.5-19
• /
• 2014

In this study, the structural analysis is performed on the method of shallow block and deep cement mixing pile, and then their characteristics and associated behaviors were analyzed. In the case of continuous beam analysis, the predicted settlement was very small, and shear force and bending stress are somewhat overestimated. The frame method is similar to numerical analysis in the internal force shallow block and long pile, but because the settlement of pile is underestimated, the additional calculation using the reaction of the long pile is necessary. For soil arching method and piled raft foundation method, the excessive axial force of long pile was predicted because the load sharing of pile is very large compared to the other methods. In the behavior of the shallow block and deep pile method, the settlement of shallow block and contact pressure are much in the center than the edge. In the estimating method considering the interaction between improved material and ground, the load sharing of the soil-cement pile ranges from 20% to 45%, and the stress ratio is 2.0~5.0 less than piled DCM. The maximum member forces at the boundary conditions of pile head are similar, but in fixed head the axial force and vertical displacement are different in accordance with pile arrangement.

• Journal of the Korean Geotechnical Society
• /
• v.37 no.11
• /
• pp.7-22
• /
• 2021

In this study, inverse analysis was performed on the bi-directional axial compressive load test conducted on drilled shafts. And the bearing capacities were analyzed by numerical analysis of various pile tip ground conditions of silt clay, silt sand, sand silt, sand gravel, weathered rock, and soft rock. The bearing capacities were analyzed using the P-S method, the Davisson method, and the allowable sttlement of 25.4 mm. The minimum allowable bearing capacities analyzed by three methods were found to be 19.64 MN ~ 24.96 MN. At this time, the base resistances were sharing a 2% ~ 12% of a head load, shaft resistance were shared 88% ~ 98% of the head load. The greater the strength of pile tip was found to increase the allowable bearing capacity. However, the difference between the maximum allowable bearing capacity and the minimum allowable bearing capacity was 5.32 MN, and the increase in the allowable bearing capacity was only 27% depending on the pile tip.