• Journal of the Korean GEO-environmental Society
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• v.17 no.11
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• pp.55-64
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• 2016

Recently, it has been made many adjacent construction of inter-facility by the expansion of urban infrastructure facilities using the underground space. The complaints relating to the stability of the facility by adjacent construction is common. In this study, it was conducted for the subway line 5 Gimpo airport station structure in the upper Gimpo urban railway to determine the behavior characteristics of station structure according to adjacent construction. It was performed evaluation of the safety zone and excavation method for station structure. And after a review of damage evaluation, track irregularities and structural calculation by using a numerical analysis, stability of the station structure according to adjacent construction was evaluated to be secured. This study is expected to be used as basic data in advance if you need to review the effects of nearby structure according to adjacent construction.

• Journal of the Korean Geotechnical Society
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• v.21 no.1
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• pp.93-103
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• 2005

Both static pile load test with load transfer measuring system and the pile dynamic load test are performed to estimate the skin friction and behavior characteristics of a large drilled shaft. And the numerical modeling of large drilled shaft is performed by applying the FDM program. Since the magnitude of friction resistance depends on the relative displacement between soil and shaft, load and displacement at the arbitrary depth along the large drilled shaft are estimated to analyze the correlation. According to the measuring results of load transfer, unit skin friction along the large drilled shaft was fully mobilized at gravel layer in the middle of shaft and the frictional resistance transmitted to bedrock was relatively small. Also, even for the same drilled shaft, the results of PDA and static load test are different with each other and the difference is discussed.

• Journal of the Korean Geotechnical Society
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• v.21 no.1
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• pp.81-91
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• 2005

This paper is the results of experimental and numerical works on the investigating design factors influencing the bearing capacity, the ratio of stress concentration, and the failure mechanism of the clay ground improved with sand compaction piles (SCP). In order to find the behavior of the clay ground improved with SCP, extensive centrifuge model experiments were carried out for each of the SCP replacement ratio of 20, 40, and $70\%$, the non-plastic fine contents in sand of 5, 10, and $15\%$, and the ratio of the improved width to the loaded area (W/B) of 1, 2, and 3. The commertially available software of FEM, CRISP, was used to analyze test results by performing numerical estimations. In these numerical analyses the sand compaction piles and the clay ground were simulated as a linear elastic and plastic constitutive model and the modified Cam-clay model, based on Critical State Soil Mechanics, respectively.

• Geotechnical Engineering
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• v.7 no.4
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• pp.35-48
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• 1991

Based on centrifuge model tests, the failure mechanism of reinforced earth retaining wall under strip load was investigated in this paper. Tests were performed by changing the materials of reinforcing strips, strip lengths, and strip arrangements. The strips were strain-gauged to measure the tensions in strips. The results were analyzed and compared with various design methosds in use to verify their feasibility. Consequently, a centrifuge model test was an effective method of investigating the behavior of reinforced earth retaining wall. The 2 : 1 stress diffusion method showed comparable results with tests in estimating the capacity of the reinforced earth wall under strip load. The superposition of tensions due to selfweight of the backfill and strip load was valid to estimate total tensions mobilized in strips. Using the elasticity theory to estimate the maximum tension mobilized in strips due to surcharge, while solutions of Boussinesq and Westergaard underestimated less tensions than the measured valises, Frohlich solution showed the comparable results with tests.

• Geotechnical Engineering
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• v.9 no.1
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• pp.31-44
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• 1993

Model tests in calibration chamber with open -ended steel pipe pile have been performed in sand deposit to clarify effect of soil plug on bearing capacity, load transfer mechanisms in soil plug, and behavior of soil plug under dynamic and static conditions. Model piles were devised so that bearing capacity of open -ended pile could be measured separately into outside skin friction, inside skin friction due to soil plug -pile interaction and end bearing force on the section of steel pipe pile. It may be concluded, form the test results, that the plugging level of open -ended pile is more correctily defined by specific recovery ratio, y, rather than by plug length ratio, PLR, and the major part of inside skin friction is generated within the range of three times as long as the inner diameter of the pile from the pile tip. The ratio of inside skin friction to total bearing capacity is much larger than that of outside skin friction to total bearing capacity. Therefore, the bearing capacity of pile could not be well predicted, unless the inside skin friction is properly taken into account.

• Geotechnical Engineering
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• v.9 no.1
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• pp.45-58
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• 1993

Paper drain method is one of the methods used for the improvement of soft clay as hydraulic fill sites or the seaside industrial complex. This method adopts a card board as the drain materials instead of sand piles in sand drain method. In this paper 3 types of drain board are used to fond out the characteristics of consolidation by vacuum consolidation model test. So does the no drain board test. This test causes the reduction of pore water pressure to promote the settlement without change of ground water level. Conclusively, the vacuum consolidation shows 3-dimensional behaviors and pore water pressure reaches a negative value in a short time. In addition, it is expected to have a comparatively good consolidation effect using non -woven board, and vacuum loading results in increasing the shear strength at the bottom and top of call layers.

• Geotechnical Engineering
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• v.14 no.3
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• pp.47-62
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• 1998

The disturbed state concept (DSC) proposed here is based on the idea that a deforming material element can be treated as a mixture of two constituent parts in the relative intact (Rl) and fully adjusted (FA) states, referred to as reference states. Based on this idea, DSC provides a unified constitutive model for the characteristics of saturated sands under cyclic loading. The model parameters for saturated sands are evaluated by using data from truly triaxial test device, The laboratory test results are also used for the verification of D SC model. In general, the model predictions are found to provide satisfactory correlation with the test results. From the results of this research, it can be stated that the DSC model is capable of characterizing the cyclic behavior of saturated sands under dynamic loading.

• Journal of the Korean Geotechnical Society
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• v.21 no.4
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• pp.123-134
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• 2005

A coupled three-dimensional pile group analysis method (YSGroup) was developed considering nonlinear pile head stiffness matrices and compared with other analytical methods (elastic displacement method, Group 6.0 and FBPier 3.0). In this method, a pile cap was modelled by four-node flat shell element, a pier was modelled using 3 dimensional beam element, and individual piles were modelled as beam-column elements. Through the comparative studies on a piled pie. subjected to lateral loads in linear soil, it was found that present method (YSGroup), elastic displacement method and Group 6.0 gave similar results of lateral pile head displacement, but FBPier 3.0 was estimated to show somewhat larger displacements than those from the three methods. Displacements of superstructure (pier), including nonlinear soil behavior, could be estimated by present method (YSGroup) and FBPier 3.0 because these two methods modelled the superstructure directly by finite element techniques. It was found that pile groups in pinned pile head condition had a tendency to cause excessive rotation of the pile cap.

• Journal of the Korean Geotechnical Society
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• v.15 no.1
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• pp.79-98
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• 1999

In the present study, a simple finite element method of analysis to predict non-uniform settlements at the interface between the mat foundation and foundation soils is proposed. Based on the proposed finite element method of analysis, the method to evaluate load sharing ratios of the foundation soils adjacent to the granular group piles is also presented. Further proposed is a procedure to estimate ultimate bearing capacity of the skirted granular group piles in a square pattern. To verify validity of the proposed methods and the estimated ultimate bearing capacity of the skirted group piles, comparisons are made with the results analyzed by using the PENTAGON3D FEM program. Finally, behavior characteristics with different reinforcement patterns of the skirts and the effect of an increase of ultimate bearing capacity due to the skirts are analyzed in connection with the design parameters.

• Journal of the Korean Geotechnical Society
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• v.15 no.1
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• pp.175-183
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• 1999

Recently, problems related to vibrations of decomposed granite soils have acquired increasing attention in Korea because those soils cover approximately one third of the country. Both resonant column and cyclic triaxial test were performed to investigate deformation characteristics of unsaturated and cement-mixed decomposed granite soils in Suwon region. The important soil parameters in this respect are the shear moduli, dynamic moduli of elasticity and damping ratios. The dynamic parameters are influenced by variables such as strain amplitude, ratio of loading cycles, and degree of saturations, etc. Test results and data have shown that the optimum degree of saturation to the maximum shear modulus due to a capillary menisci effect was about 17~18 % at low strain amplitude and 10~15 % at intermediate strain amplitude. This paper suggests the range of threshold strain and mean shear modulus of decomposed granite soils in Suwon region. It also proposed the empirical relationship between the dynamic parameters for cement-mixed and non-mixed decomposed granite soils.