• Journal of the Korean Geotechnical Society
• /
• v.19 no.4
• /
• pp.43-53
• /
• 2003

To get improved soil parameters in the laboratory tests, the effects of sample disturbance should be excluded as much as possible. A collaborative research between Dong-A University and PHRI (Japan) was conducted to investigate the effects of sample disturbance due to sampling techniques and samplers on Pusan clays. The results of unconfined compression and consolidation tests performed on the clay samples taken by them have been compared in terms of soil parameters and sample disturbance. As the result of the study, it was found that when the Korean sampler was used with a different technique of cleaning the borehole bottom and removing slime before inserting and penetrating the sampler tube, similar to the one commonly used in Japanese practice, the quality of samples could be greatly improved. Furthermore, the CRS test with the rate of 0.02%/min yielded larger values of consolidation parameters and better degree of sample disturbance than those of oedometer test, due to the difference in testing method.

• Journal of the Korean GEO-environmental Society
• /
• v.4 no.2
• /
• pp.5-13
• /
• 2003

The domestic design method for the shaft resistance of drilled shafts into a bedrock is based on the empirical method, where the uniaxial compressive strength of rock specimen is utilized for calculation of the shaft resistance. This method has uncertainties in prediction of capacity of drilled shafts and result in uneconomic engineering design. Recently a new improved design method was suggested, which reflects important factors that affect the strength of pile sockets. Socket roughness is one of the significant factors influencing the shaft resistance of drilled shaft socketed into rock. In this paper roughness information for the shaft resistance design of socket pile was suggested on the basis of statistical analysis of data measured from wall surface in the bore holes of drilled shafts.

• Geomechanics and Engineering
• /
• v.12 no.3
• /
• pp.523-539
• /
• 2017

Clay soils are typical for their swelling properties upon absorption of water during rains and development of cracks during summer time owing to the profile desorption of water through the inter-connected soil pores by water vapour diffusion leading to evaporation. This type of unstable soil phenomenon by and large poses a serious threat to the strength and stability of structures when rest on such type of soils. Even as lime and cement are extensively used for stabilization of clay soils it has become imperative to find relatively cheaper alternative materials to bring out the desired properties within the clay soil domain. In the present era of catastrophic environmental degradation as a side effect to modernized manufacturing processes, industrialization and urbanization the creative idea would be treating the waste products in a beneficial way for reuse and recycling. Bottom ash and ecosand are construed as a waste product from cement industry. An optimal combination of bottom ash-eco sand can be thought of as a viable alternative to stabilize the clay soils by means of an effective dispersion dynamics associated with the inter connected network of pore spaces. A CATIA model was created and imported to ANSYS Fluent to study the dispersion dynamics. Ion migration from the bottom ash-ecosand pile was facilitated through natural formation of cracks in clay soil subjected to atmospheric conditions. Treated samples collected at different curing days from inner and outer zones at different depths were tested for, plasticity index, Unconfined Compressive Strength (UCS), free swell index, water content, Cation Exchange Capacity (CEC), pH and ion concentration to show the effectiveness of the method in improving the clay soil.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.3 no.2
• /
• pp.109-117
• /
• 1983

Dynamic shear modulus of the compacted clayey soil was determined by the resonant column test to study the parametric effects of confining pressure, shear strain amplitude, molding water content, compaction energy, void ratio and the degree of saturation. The effect of each of these parameters on the dynamic shear modulus found to be significant and can be explained in terms of the changes in soil by compaction. Dynamic shear modulus of the compacted soil is increased significantly by compaction and compaction at the dry side of the optimum moisture content is much more effective. It is also found that the dynamic shear modulus showes a good correlation to the static shear strength of the compacted soil. Therefore the dynamic shear modulus of the compacted soil for a certain confining pressure may be obtained ea8i1y from the unconfined compression strength.

• Computers and Concrete
• /
• v.25 no.5
• /
• pp.383-400
• /
• 2020

Due to higher stiffness to weight, higher corrosion resistance, higher strength to weight ratios and good durability, concrete composite structures provide many advantages as compared with conventional materials. Thus, they have wide applications in the field of concrete construction. This research focuses on the structural behavior of steel-tube CFRP confined concrete (STCCC) columns under axial concentric loading. A nonlinear finite element analysis (NLFEA) model of STCCC columns was simulated using ABAQUS which was then, calibrated for different material and geometric models of concrete, steel tube and CFRP material using the experimental results from the literature. The comparative study of the NLFEA predictions and the experimental results indicated that the proposed constitutive NLFEA model can accurately predict the structural performance of STCCC columns. After the calibration of NLFEA model, an extensive parametric study was performed to examine the effects of different critical parameters of composite columns such as; (i) unconfined concrete strength, (ii) number of CFRP layers, (iii) thickness of steel tube and (iv) concrete core diameter, on the axial load capacity. Furthermore, a large database of axial strength of 700 confined concrete compression members was developed from the previous researches to give an analytical model that predicts the ultimate axial strength of composite columns accurately. The comparison of the predictions of the proposed analytical model was done with the predictions of 216 NLFEA models from the parametric study. A close agreement was represented by the predictions of the proposed constitutive NLFEA model and the analytical model.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.1
• /
• pp.406-411
• /
• 2012

The undrained strength of soils is open determined from the results of the piezocone penetration. The reliability of the value of the undrained strength lies on the cone factor value, whose evaluation needs a lot of experimental data and investigation for each site. In this study, the cone factors were evaluated for the northeastern part of Shiwha area in Gyunggi province using the experimental data of the field vane, unconfined compression, and UU triaxial compression tests. The values of the conventional cone factors $N_{kt}$, $N_{ke}$, $N_{{\Delta}u}$, and the new factor $N_e$ were determined to be 12, 11, 3, and 13, respectively. It was observed that there is a remarkable relationship between $N_{{\Delta}u}$ and the pore pressure ratio Bq.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.9 no.3
• /
• pp.115-123
• /
• 1989

This paper probabilisticly analyses the variance of the soil parameters on kinds of soil by conducting statistical analysis through the Unified Soil Classification System. Data used are the result of soil test which the Korea National Housing Corporation conducted in 176 sites of 74 cities throughout the country during the past 13 years from 1974 to 1986. In this paper, soil parameters such as natural water contents, specific gravity of soil particle, Atterberg limits, N-values, unconfined compression strength, compression index and shear strength parameter etc., is analysed. The result of the analysis is as follows. 1) The variance in physical properties of the soil is, when compared with coefficient of variation which is statistical variable, comparatively small. 2) The shear strength parameter is proved to be about 40% and compression index is about 32%. 3) The variance in specific gravity is 0.87-2.49% in granular soil and 0.91~5.03% in cohesive soil respectively. So, the degree of the variance is very small.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.31 no.6C
• /
• pp.241-250
• /
• 2011

The design method of IGM proposed by FHWA to predict bearing capacities of drilled shaft socketed in weathered granite has been used generally. In this study, site investigations were performed in a pilot test site, and disturbance and roughness were measured. Geotechnical properties were assorted as cohesive material and undisturbed and smooth surface. A simple relationship was proposed to predict unconfined strength ($q_u$) of weathered granite using static load test results, load transfer test results and N values. It was confirmed that the design method to estimate bearing capacities of drilled shaft could improve IGM's theory for weathered granite from this research.

• Journal of the Korean Geosynthetics Society
• /
• v.6 no.2
• /
• pp.17-20
• /
• 2007

In this study, a series of uniaxial unconfined compression test and constant-head test were performed to investigate the mechanical characteristics of porous concrete using recycled-aggregate for the varying unit weight and water-cement ratio. To enhance the permeability of the porous concrete, the recycled-aggregate with similar grain size in the range of $40{\pm}5mm$ was used and water-cement ratio that leads to the lean-mix was adapted. The mechanical characteristics of the porous concrete cured for 3 days were examined; the compressive strength and $E_{50}$ showed their maximum values with 40% water-cement ratio and $1.8t/m^3$ unit weight and the permeability coefficient was averagely measured in the range of $0.9{\times}10^0cm/sec$ regardless of water-cement ratio and unit weight.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.7 no.2 s.25
• /
• pp.35-44
• /
• 2007

Plowable fill is generally a mixture of sand, fly ash, a small amount of cement and water. Sand is the major component of most flowable fill mixes. Marine dredged soil was adopted for flowable fill instead of fly ash. Natural sea sand and in-situ soil were used for comparison. The flow behavior, hardening characteristics, and ultimate strength behavior of flowable fill were investigated. The unconfined compression test necessary to sustain walkability as the fresh flowble fill hardens was determined and the strength at 3-days appeared to correlate well with the water-to-cement ratio. The strength parameters, like cohesion and internal friction angle, was determined along the curing time. The creep test for settlement potential was conducted. Also, potable falling weight deflectometer(PFWD) test has been carried out for elastic modulus of each controlled low strength materials(CLSM). The data presented show that marine dredged soil and in-situ soil can be successfully used in CLSM.