• Journal of the Korean Geosynthetics Society
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• v.19 no.1
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• pp.103-110
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• 2020

The DMM (Deep mixing method) is a construction method in which an improved pile is installed in the soft ground by excavation ground using an auger and then mixing ground stabilizer with soil. Improved pile installed in the soft ground by the DMM may have different compressive strength depending on the properties and characteristics of the soil. In the previous study, laboratory tests were performed on the ground stabilizer for the DMM developed by using the ash of the circulating fluidized bed boiler as a stimulator for alkali activation of the blast furnace slag. And the test results were analyzed to derive the correlation between the unit weight of binder (γ_B) and the uniaxial compressive strength (q_u). In this study, comparative reviews were conducted on the correlations derived from the same laboratory tests on soil material collected from the Saemangeum area and the stability of the site was evaluated by analyzing the test results performed at the site. As a result, the clay collected from the Saemangeum area satisfies the correlation between the unit weight of binder (γ_B) and the uniaxial compressive strength (q_u) derived from the previous study. And the result of the test at the field showed a higher uniaxial compressive strength than the standard strength at the field, indicating excellent stability.

• Geomechanics and Engineering
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• v.6 no.2
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• pp.173-194
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• 2014

Laboratory and field data showed that deep mixed (DM) columns accelerated the rate of consolidation of the soft foundations. Most analyses of consolidation of DM column-improved foundations so far have been based on the elastic theory. In reality, the DM columns may yield due to the stress concentration from the soft soil and its limited strength. The influence of column yielding on the degree of consolidation of the soft foundation improved by DM columns has not been well investigated. A three-dimensional mechanically and hydraulically-coupled numerical method was adopted in this study to investigate the degree of consolidation of the DM column foundation considering column yielding. A unit cell model was used, in which the soil was modeled as a linearly elastic material. For a comparison purpose, the DM column was modeled as an elastic or elastic-plastic material. This study examined the aspects of stress transfer, settlement, and degree of consolidation of the foundations without or with the consideration of the yielding of the DM column. A parametric study was conducted to investigate the influence of the column yielding on the stress concentration ratio, settlement, and average degree of consolidation of the DM column foundation. The stress concentration ratio increased and then decreased to reach a constant value with the increase of the column modulus and time. A simplified method was proposed to calculate the maximum stress concentration ratios under undrained and drained conditions considering the column yielding. The simplified method based on a composite foundation concept could conservatively estimate the consolidation settlement. An increase of the column modulus, area replacement ratio, and/or column permeability increased the rate of consolidation.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09c
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• pp.135-139
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• 2010

A construction technique to install the soil-bentonite (SB) cut-off wall for in-situ geoenvironmental containment by employing the trench cutting and re-mixing deep wall method is first presented in this paper. The laboratory test results on the hydraulic barrier performance of SB in relation to the chemical compatibility are then discussed. Hydraulic conductivity tests using flexible-wall permeameters as well as swell tests were conducted for SB specimens exposed to various types and concentrations of chemicals (calcium chloride, heavy fuel oil, ethanol, and/or seawater) in the permeant and/or in the pore water of original soil. For the SB specimens in which the pore water of original soil did not contain such chemicals and thus the sufficient bentonite hydration occurred, k values were not significantly increased even when permeated with the relatively aggressive chemical solutions such as 1.0 mol/L $CaCl_2$ or 50%-concentration ethanol solution. In contrast, the SB specimens containing $CaCl_2$ in the pore water had the higher k values. The excellent linear correlation between log k and swelling pressure implies that the swelling pressure can be a good indicator for the hydraulic barrier performance of the SB.

• Journal of the Korean GEO-environmental Society
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• v.13 no.6
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• pp.83-90
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• 2012

Generally, the effect of the cement deep mixing method on the improvement of clay ground is far greater than the effect of physical improvement. Although it leads to great improvement strength in the initial stage, there are not many constructional precedents in Korea and it is hard to manage quality according to the cement-clay mixing method. In order to figure out the strength characteristics according to the mixing ratio of cement, sand, and clay and the improvement characteristics of weak ground according to the forms of the specimens to be improved, marine clay was used in this study to conduct the uniaxial compression test and soil bin model test. The test piece specimens for the uniaxial compression test were mixed with sand in a fixed ratio with the criterion of the water cement ratio. The cement was mixed with clay in the ratios of 10%, 20%, 30%, and 40% to the clay weight. The moisture content of the soil ground was made in the ratios of 40%, 60%, and 80%. The test piece specimens went through curing by moistening for 7, 14, and 28 days and underwent the uniaxial compression test according to the curing period. For the bearing test, the soil bin models were made and the ground improved in the Mat type was formed. After that, the bearing strength was compared in this study according to the improvement ratio and analyzed the intervening effect between the walls of the improved specimens.

• Geomechanics and Engineering
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• v.28 no.4
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• pp.385-396
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• 2022

The accurate determination of the subgrade reaction modulus (K_s) of soil is an important factor for geotechnical engineers. This study estimated the K_s of soft soil improved with floating deep cement mixing (DCM) columns. A novel prediction model was developed that emphasizes the accuracy of identifying the most significant parameters of K_s. Several multi-layer perceptron (MLP) models that were trained using the Levenberg Marquardt (LM) backpropagation method were developed to estimate K_s. The models were trained using a reliable database containing the results of 36 physical modelling tests. The input parameters were the undrained shear strength of the DCM columns, undrained shear strength of soft soil, area improvement ratio and length-to-diameter ratio of the DCM columns. Grey wolf optimization (GWO) was coupled with the MLPs to improve the performance indices of the MLPs. Sensitivity tests were carried out to determine the importance of the input parameters for prediction of K_s. The results showed that both the MLP-LM and MLP-GWO methods showed high ability to predict K_s. However, it was shown that MLP-GWO (R = 0.9917, MSE = 0.28 (MN/m²/m)) performed better than MLP-LM (R =0.9126, MSE =6.1916 (MN/m²/m)). This proves the greater reliability of the proposed hybrid model of MLP-GWO in approximating the subgrade reaction modulus of soft soil improved with floating DCM columns. The results revealed that the undrained shear strength of the soil was the most effective factor for estimation of K_s.

• Journal of the Korean GEO-environmental Society
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• v.12 no.9
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• pp.71-78
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• 2011

Cement treating technique, such as deep mixing method, has been used widely to stabilize the dredged clayey soil for many years. Despite of its effectiveness in treating soil by cement, several efforts have also been made to try to reduce the side effect of the cement that used to stabilize the dredged clay. However, authors considered that more detailed study on the physical and mechanical properties of lean-mixed soil-cement has been required to establish the design procedure to apply the practical problems. Therefore, in this study, the curing time and mixing ratio was used as key parameters to estimate the physical and mechanical properties including long-term behavior. The unconfined strength of lean-mixed soil-cement increase continuously during curing period, 270 days, while increasing rate becomes low in ordinary cement-treated dredged clay. We also concluded that cement-treated dredging clay shows apparent quasi overconsolidation behavior even in low cement proportion. By this study, fundamental approach was carried out for effective reuse of very soft dredged clayey soil both in mechanical and environmental aspect. It can be also expected that this study can propose a basic design data to use the lean-mixed soil cement.

• Journal of the Korean Geosynthetics Society
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• v.18 no.2
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• pp.37-44
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• 2019

The compressive strength of the soil stabilizer in the deep mixing method (DMM) depends on kinds of soil, particle size distribution, and water content. Because of this, Laboratory test has to perform to estimate the unit weight of binder to confirm the satisfaction of the design strength. In this study, uniaxial compression strength was measured by mixing the soil stabilizers developed in the previous study with clay in Busan, Yeosu, and Incheon area. And the strength enhancement effect was evaluated comparing with blast furnace slag cement (BFSC). Also, the relationship between the unit content of binder and uniaxial compressive strength was investigated in order to easily calculate the unit weight of binder required to ensure the stability of the ground at the field. As the results of the analysis, the relationship between the unit content of binder and the uniaxial compressive strength are ${\gamma}_B=(108.93+0.0284q_u){\pm}35$ when W/B is 70%, and ${\gamma}_B=(122.93+0.0270q_u){\pm}40$ when W/B is 80%.

• Journal of the Korean Geotechnical Society
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• v.30 no.4
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• pp.5-19
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• 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 GEO-environmental Society
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• v.24 no.2
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• pp.5-12
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• 2023

In this study, the amount of heaving soil and the heave characteristics of the heaving soil generated at the actual site were quantitatively analyzed through DCM laboratory test construction. By reproducing a series of construction processes of the DCM method in a large-scale soil tank close to the actual site, the amount of heaving soil was predicted and the elevation characteristics such as elevation, diffusion range, diffusion angle and amount of elevation of the heaving soil were evaluated. As a result of the laboratory test construction, the actual elevation in terms of similarity within the DCM improvement section is 0~8.18m, and an average of 3.50m is observed. The actual diffusion range of the heaving soil converted to the similarity ratio is distributed from 28.0 to 38.0m on the left and right sides of the improvement section. The total amount of heaving soil calculated by the SUFFER program based on the results of the laboratory test construction is 19,901m³. Compared with the injected slurry amount of 16,992m³, the amount of heave compared to the injected amount is analyzed as 85.4%. The diffusion angle of DCM heaving soil, which analyzed the results of DCM laboratory test construction with the SUFFER program, is measured to be 30.0~38.0° at a depth of 50.0m, and is evaluated as an average of 34.0°. On the other hand, based on the DCM laboratory test construction and the analysis results using the program performed in this study, the amount of heaving soil at the DCM depths of 40.0m and 60.0m is predicted.

• Advances in concrete construction
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• v.14 no.3
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• pp.185-194
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• 2022

For producing cement and concrete, the construction field has been encouraged by the usage of industrial soil waste (or) secondary materials since it decreases the utilization of natural resources. Simultaneously, for ensuring the quality, the analyses of the strength along with durability properties of that sort of cement and concrete are required. The prediction of strength along with other properties of High-Performance Concrete (HPC) by optimization and machine learning algorithms are focused by already available research methods. However, an error and accuracy issue are possessed. Therefore, the Enhanced Deep Neural Network (EDNN) based strength along with durability prediction of HPC was utilized by this research method. Initially, the data is gathered in the proposed work. Then, the data's pre-processing is done by the elimination of missing data along with normalization. Next, from the pre-processed data, the features are extracted. Hence, the data input to the EDNN algorithm which predicts the strength along with durability properties of the specific mixing input designs. Using the Switched Multi-Objective Jellyfish Optimization (SMOJO) algorithm, the weight value is initialized in the EDNN. The Gaussian radial function is utilized as the activation function. The proposed EDNN's performance is examined with the already available algorithms in the experimental analysis. Based on the RMSE, MAE, MAPE, and R² metrics, the performance of the proposed EDNN is compared to the existing DNN, CNN, ANN, and SVM methods. Further, according to the metrices, the proposed EDNN performs better. Moreover, the effectiveness of proposed EDNN is examined based on the accuracy, precision, recall, and F-Measure metrics. With the already-existing algorithms i.e., JO, GWO, PSO, and GA, the fitness for the proposed SMOJO algorithm is also examined. The proposed SMOJO algorithm achieves a higher fitness value than the already available algorithm.