• Journal of the Korean Geosynthetics Society
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• v.16 no.2
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• pp.149-158
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• 2017

Permeating injection is commonly known as an ideal type of injection in grouting reservoir embankment, yet often-combined permeating and fracturing injection grouting operation can disturb the original soil. A grouting method has been regarded as effective and developed to ameliorate the possible disturbance problem. It involves compaction grouting with low expansive pressure near the injection hole and repetitive injection and compaction with grout material that allows ideal permeating injection. This thesis develops Hybrid Grout (ie. HG grout) that allows various application in any ground condition combined together, has high fineness and low viscosity, and expands permeation injection to silty sand. It researches on the injection effect of permeable compaction grout which is done with PC packer and is a combination of HG grout and expansion agent to obtain permeation compaction effect on the area near grout injection spot by developing Permeable Compaction Type Packer(ie. PC packer). As the developed PC packer, HG grout, and and expansion agent (HI-E) are applied to reservoir embankment reinforcement grouting, possibile permeation compaction effect that satisfies reservoir embankment grouting standard is confirmed according to the research.

• Journal of the Korean Geotechnical Society
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• v.18 no.5
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• pp.37-42
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• 2002

Artificial neural networks are efficient computing techniques that are widely used to solve complex problems in many fields. In this paper a liquefaction potential was estimated by using a back propagation neural network model applicated to cyclic triaxial test data, soil parameters and site investigation data. Training and testing of the network were based on a database of 43 cyclic triaxial test data from 00 sites. The neural networks are trained by modifying the weights of the neurons in response to the errors between the actual output values and the target output value. Training was done iteratively until the average sum squared errors over all the training patterns were minimized. This generally occurred after about 15,000 cycles of training. The accuracy from 72% to 98% was shown for the model equipped with two hidden layers and ten input variables. Important effective input variables have been identified as the NOC,$D_10$ and (N$_1$)$_60$. The study showed that the neural network model predicted a CSR(Cyclic shear stress Ratio) of silty-sand reasonably well. Analyzed results indicate that the neural-network model is more reliable than simplified method using N value of SPT.

• Journal of the Korean Geotechnical Society
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• v.32 no.9
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• pp.17-27
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• 2016

Parial drainage characteristics of clayey silt with low plasticity from the west coast (Incheon and Hwaseong) was analyzed using CPTU based existing correlation equations and compulsory replacement method. Generally, the estimated $OCRs={\kappa}{\cdot}((q_t-{\sigma}_{vo})/{\sigma}^{\prime}_{vo})$ using Powell and Quartman(1988) were higher than those obtained by the oeodometer tests. These trends were noticeable for the layers containing a lot of silty and sand soils. The assessment of partial drainage conditions was performed through Schnaid et al. (2004)'s equation; it is based on plotting the normalized cone resistance, $Q_t$ versus the pore pressure parameter, $B_q$ in combination with the strength incremental ratio, $s_u/{\sigma}^{\prime}_{vo}$ to the CPTU data. It is evident that more than half of the data fall in the range where $B_q$ < 0.3, corresponding to the domain in which the partial drainage prevails when testing normally consolidated soils at a standard rate of penetration (2 cm/s). To estimate the replacement depth of clayey silt with low plasticity, back analysis was carried out to evaluate the internal friction angle based on where the design depths are equal to the checked depths using bearing capacity equation. The internal friction angels obtained from the back analysis tended to increase as the plasticity index decreases, which is ranged approximately from ${\varphi}^{\prime}=2^{\circ}$ to ${\varphi}^{\prime}=7^{\circ}$.

• Korean Journal of Soil Science and Fertilizer
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• v.47 no.4
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• pp.262-268
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• 2014

The management of soil chemical properties is very important to sustainable agriculture of many horticultural crops, including cucumber. This study was conducted to find the optimal soil properties of environmentally friendly agriculture in controlled horticulture. Soil chemical properties of 267 samples were collected from soil in Chungnam Province. The average of pH, EC, OM, available $P_2O_5$, exchangeable K, Ca, and Mg was 6.1, $5.38dS\;m^{-1}$, $34g\;kg^{-1}$, $1,321mg\;kg^{-1}$, $1.50cmol_c\;kg{-1}$, $10.3cmol_c\;kg{-1}$, and $3.4cmol_c\;kg{-1}$, respectively. The organic matter content in silty clay loam was significantly higher than in the other soil textures, whereas the pH, EC, exchangeable K, and Mg in loamy fine sand showed significantly lower among soil textures. The EC value and exchangeable Mg concentration were highest in mountain foot-slope soils. The frequency distribution within optimum range of soil chemical properties was 26.2%, 30.3%, 2.3%, 3.8%, 3.4%, and 6.7% for pH, OM, available $P_2O_5$, exchangeable K, Ca, and Mg, respectively. Especially, excessive portion of available $P_2O_5$ and exchangeable Ca were 94.0% and 94.4%, respectively. The EC value and organic matter content of soil samples were positive correlation with all chemical properties except soil pH. In principle component analysis of chemical properties in soil samples, the percentage of variance explained by PC 1 was 52.2%, while PC 2 explained 21.3% of the variance, for a cumulative total of 73.5%. In conclusion, these results are considered to improve soil nutrient management for sustainable controlled horticulture.

• The Journal of Engineering Geology
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• v.31 no.3
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• pp.333-342
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• 2021

In this study was conducted to measure the water content and dry unit weight of the ground using TDR (Time Domain Reflectometry) in order to supplement the problems of the conventional compaction management method. The Flat TDR system is a device that does not cause ground disturbance, and in order to verify the measured values, the dry density and water content were measured for samples of the ground subject at 7 sites other than Jumunjin Standard Temple. The water content section was divided into 6 sections of 3, 6, 9, 12, 15, and 18%, and the experimental results were confirmed according to the unified classification method. As a result of the indoor experiment, the water content showed an error of about 0.7% for the SP sample and about 1.3% for the SM sample. In addition, the dry unit weight confirmed an error of about 7% for the SP sample and about 5% for the SM sample. It was confirmed that stable values were derived in sandy or silty sandy ground except for clay or gravel. Through the experimental results, it was confirmed that the measured values of the flat TDR system derive similar values to the existing traditional compaction management method, and it was determined that the flat TDR equipment was suitable for construction sites that require quick constructability and economic feasibility.

• Journal of the Korean Geotechnical Society
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• v.34 no.12
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• pp.105-113
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• 2018

In this study, the engineering properties including bearing capacity of subgrades stabilized with a binder are analyzed by laboratory and field experiments. The main components of the binder are CaO and $SO_3$. After the binder was mixed with a low plasticity clay, the passing rates were relatively decreased as the sieve mesh size increased. Not only did the soil type change to silty sand, but engineering properties, such as the plasticity index and modified California bearing ratio (CBR), were improved for the subgrade. A comparison of the compaction curves of the stabilized subgrade and field soil compacted with the same energy demonstrated an increase of approximately 6% in the maximum dry unit weight, slight decrease in optimum moisture content, and considerable increase improvement in grain size. In the modified CBR test, the effect of unit weight and strength increase of the modified soil (with a specific amount of binder) was remarkably improved. As the proportion of granulated material increased after the addition of binder, the swelling was reduced by 3.3 times or more during initial compaction and 6.5 times by final compaction. The unconfined compressive strength of the specimens was maintained at the homogeneous value with a constant design strength. The stabilized subgrade was validated by applying it in the field under the same conditions; this test demonstrated that the bearing capacity coefficients at all six sites after one day of compaction exceeded the target value and exhibited good variability.

• Journal of the Korean Geotechnical Society
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• v.37 no.9
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• pp.25-36
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• 2021

Recently, the intelligent compaction technology for quality control of earthworks has brought attention as a quality control standard for earthworks. In this study, intelligent compaction technology and earthwork quality control methods were investigated and earthwork quality control procedures using intelligent compaction technology were considered based on field tests. Through the field compaction test of the silty sand (SM) fill material, it was confirmed that CMV and bearing capcaity index from plate load tests increased as the number of compactions increased. Based on the field test data, the average CMV and quality control target CMV were derived. The target CMV (34.2) was calculated through the correlation with the bearing capacity index of the plate load test, and the target CMV (36.6) was calculated through the analysis of the CMV increase rate. In this paper, the on-site compaction quality management procedure and methodology using intelligent compaction technology were discussed, and an intelligent compaction quality management method was proposed to promote the applicability of the technology.

• Journal of the Korean Geosynthetics Society
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• v.21 no.4
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• pp.69-78
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• 2022

Geotextile tubes are widely used to prevent erosion in coastal areas and to replace the backfill for shore slopes in the reclamation of land using dredged soil. In this study, The triaxial confining pressures were chosen as 10kPa, 50kPa, or 100kPa for the specimens reinforced with geotextile considering the condition in the site. The strain behavior under various compressive stresses was then identified. At strains 0% to 7%, the stress-strain behavior was the same due to the effect of initial strain hardening, in which the force was exerted according to the relaxation of the geotextile regardless of the confining pressure (≤100kPa). At strains of 7% or more, the specimen with the small confining pressure had smaller deformation under load, which increases the tensile resistance provided by the reinforcing geotextile. Brittle fracture was then observed due to strain softening and the deviator stress abruptly decreased. This is different from the phenomenon in which the shear strength increases as the confining pressure increases in general triaxial compression tests. In the geoxtile-confined tests, geotextiles are primarily subjected to tensile displacement. Thereafter, the modulus of elasticity increases rapidly, which exhibits the elastic behavior of the geotextile.

• Journal of the Korean Geotechnical Society
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• v.22 no.9
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• pp.61-68
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• 2006

Recently the large scale civil engineering projects are being implemented by reclaiming the sea or utilizing seashore and river embankment areas. The reclaimed land and utilized seashore are mostly soft ground that doesn't have sufficient bearing capacity. This soft ground consists of fine-grained soil such as clayey and silty soils or large void soil like peat or loose sand. It has high ground water table and it may cause the failure and crock of building foundation by uplift pressure and ground water leakage. In this study, the permittivity and the transmissivity were evaluated with the applied normal pressure in the laboratory. The laboratory model tests were conducted by utilizing geocomposite drainage system for draining the water out to release the uplift pressure. The soil used in the laboratory drainage test was dredged soil from the reclaimed land where uplift pressure problems can arise in soil condition. Geocomposite drainage system was installed at the bottom of apparatus and dredged soil was layered with compaction. Subsequently the water pressure was supplied from the top of specimen and the quantities of drainage and the pore water pressure were measured at each step water pressure. The results of laboratory measurements were compared with theoretical values. For the evaluation of propriety of laboratory drainage test, 2-D finite elements analysis that can analyze the distribution and the transferring of pore water pressure was conducted and compared with laboratory test results.

• Journal of the Korean Geotechnical Society
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• v.25 no.9
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• pp.67-76
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• 2009

The problems of bearing capacity, settlement and shear deformation occur when constructing a structure such as harbor, airport and bridge on soft ground of marine clay, silty clay or sandy soil. Various ground improvement methods are applied to obtain preceding settlement of soft ground and strength increase. In this study, to analyze the applicability of PBD method in deep soft ground, the compound drainage capacity test was operated in comparison with SD. As a result of the test, a minimum drainage capacity of drain material was estimated to be more than $10\;cm^3/sec$ at a more than $400\;kN/m^2$ and less than $5\;cm^3/sec$ at a more than $500\;kN/m^2$ confining pressure in case of single core PBD. In case of double core PBD, it was estimated to be more than $10\;cm^3/sec$ at a more than $500\;kN/m^2$ confining pressure.