• Geomechanics and Engineering
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• v.16 no.2
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• pp.159-168
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• 2018

In this study, a real-time grouting management system based on the clogging theory was established to manage injection procedure in real time. This system is capable of estimating hydraulic permeability with the passage of time as the grout permeates through the ground, and therefore, capable of estimating real time injection distance and flow rate. By adopting the Controlled Injection Pressure (CoIP) model, it was feasible to predict the grout permeation status with the elapse of time by consecutively updating the hydraulic gradient and flow rate estimated from a clogging-induced alteration of pore volume. Moreover, a method to estimate the volume of the fractured gap according to the reduction in injection pressure was proposed. The validity of the proposed system was successfully established by comparing the estimated values with the measured field data.

• Journal of the Korean Geotechnical Society
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• v.20 no.6
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• pp.95-107
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• 2004

In this paper, the rheological characteristics of slurry used fur slurry-shield tunnels were studied with emphasis on penetration characteristics. The slurry penetration was modeled by soil-filter clogging theory. The coefficient of particle deposition was suggested as an indicator of sin clogging during tunnel construction and calculated through model tests. The measured slurry weight, clogged in the base soil, was compared with the value obtained from clogging theory. Based on the testing results, a stability analysis of a tunnel face was performed to pinpoint the most influential factor affecting stability of slurry-shield tunnels. It was found that the stability of tunnel face is dependent on the ratio of infiltration velocity to the coefficient of particle deposition, and the penetration distance of slurry increases with the ratio of infiltration velocity to the coefficient of particle deposition. Since the stability of tunnel face decreases with the slurry penetration distance, it was necessary to add some additives in order to reduce the slurry penetration distance. It was found that the ground condition needs additives when the soil has the effective particle diameter$(D_{10})$ larger than 0.75mm. It was also found that the tunnel face stability due to slurry penetration is significantly affected by the tunnel advance rate.

• Journal of the Korean Geotechnical Society
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• v.30 no.6
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• pp.23-39
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• 2014

An artificial rainwater reservoir installed in urban areas for recycling rainwater is an eco-friendly facility for reducing storm water effluence. However, in order to recycle the rainwater directly, the artificial rainwater reservoir requires an auxiliary system that can remove non-point source pollutants included in the initial rainfall of urban area. Therefore, the conventional soil filtration technology is adopted to capture non-point source pollutants in an economical and efficient way in the purification system of artificial rainwater reservoirs. In order to satisfy such a demand, clogging characteristics of the sand filter layers with different grain-size distributions were studied with real non-point source pollutants. For this, a series of lab-scale chamber tests were conducted to make a prediction model for removal of non-point source pollutants, based on the clogging theory. The laboratory chamber experiments were carried out by permeating two types of artificially contaminated water through five different types of sand filter layers with different grain-size distributions. The two artificial contaminated waters were made by fine marine-clay particles and real non-point source pollutants collected from motorcar roads of Seoul, Korea. In the laboratory chamber experiments, the concentrations of the artificial contaminated water were measured in terms of TSS (Total Suspended Solids) and COD (Chemical Oxygen Demand) and compared with each other to evaluate the performance of sand filter layers. In addition, the accumulated weight of pollutant particles clogged in the sand filter layers was estimated. This paper suggests a prediction model for removal of non-point source pollutants with theoretical consideration of the physical characteristics such as the grain-size distribution and composition, and change in the hydraulic conductivity and porosity of sand filter layers. The lumped parameter ${\theta}$ related with the clogging property was estimated by comparing the accumulated weight of pollutant particles obtained from the laboratory chamber experiments and calculated from the prediction model based on the clogging theory. It is found that the lumped parameter ${\theta}$ has a significant influence on the amount of the pollutant particles clogged in the pores of sand filter layers. In conclusion, according to the clogging prediction model, a double-sand-filter layer consisting of two separate layers: the upper sand-filter layer with the effective particle size of 1.49 mm and the lower sand-filter layer with the effective particle size of 0.93 mm, is proposed as the optimum system for removing non-point source pollutants in the field-sized artificial rainwater reservoir.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.2
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• pp.485-500
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• 2018

The behavior of cement-based permeation grouting is divided into three different groups depending on the grain size distribution of the soils: (1) zone of cement-based permeation grouting not feasible; (2) zone of cement-based permeation grouting feasible; and (3) zone in which an accelerating agent should be added to limit the penetration depth. In the cement-based permeation grouting feasible zone, the concept of a representative pore radius was proposed. The ratios of the representative pore radius to the mean pore radius were obtained by performing laboratory test and comparing with clogging theory; these values were in the range of 1.07 and 1.35 depending on the grain size distribution of the soils. In addition, a functional relationship between the lumped parameter (${\theta}$), the representative pore radius and the w/c ratio were derived by comparing and matching experimental results with predictions from theory. In the zone in which the accelerating agent should be added, the controlling process of gel time to limit the penetration depth was experimentally verified. The test results matched well with those obtained from theory utilizing the developed grout penetration program on condition that the viscosity increasing tendency of grout suspension with time is properly taken into account.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.4
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• pp.401-413
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• 2013

Slurry shield tunnelling ensures stability by pressurizing the tunnel face with the slurry contained in the chamber. It resists water and earth pressure in order to prevent the failure in the tunnel face during tunnel excavation. If the ground is relatively coarse, slurry can not clog the tunnel face and excessive slurry infiltration will occur. In this case chemical compounds or additives should be added to the slurry in order to improve the clogging phenomena at the tunnel face. In this study, the effect of the carbon dioxide gas as an additive to the slurry instead of chemical compounds on the capability of enhancing the clogging in the tunnel face is investigated. Bubbles arising from the carbonate-added slurry are trapped in the soil voids enhancing the clogging capability. This effect is studied in this paper by performing laboratory model tests simulating in-situ conditions, and by adopting the fine particle clogging theory. Tunnel face stability analysis was also performed and it was found that the effective size ($D_{10}$) of soils which can guarantee tunnel stability utilizing the carbonate-added slurry increased from 1.0 mm up to 2.6 mm. Moreover, Stability analysis showed that the tunnel face is stable if the ${\lambda}$(deposition coefficient) value is greater than $0.007sec^{-1}$.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.414-423
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• 2006

Many construction projects adopt grouting technology to prevent the leakage of groundwater or to improve the shear strength of the ground. Recognition as a feasible field procedure dates back to 1925, Since then, developments and field use have increased rapidly. According to improvement of grout materials, theoretical study on grout penetration characteristics is demanded. Fluid of grout always tends to flow from higher hydraulic potential to lower and the motion of grout is also a function of formation permeability. Viscosity of grout is changed by chemical action while grout moves through pores. Due to the increment of viscosity, permeability is decreased. Permeability is also reduced by grout particle deposits to the soil aggregates. In this thesis, characteristics of new cement grout material that is developed recently is studied: injectable volume of new grout material is tested in two different sizes of sands, and the method to calculate injectable volume of grout is suggested with consideration of change in viscosity and clogging phenomena. The calculated values are compared with injection test results. Viscosity of new grout material is found to be an exponential function of time. And lumped parameter $\theta$ of new grout material to be used for assessing deposition characteristics is estimated by comparing deposit theory with injection test results considering different soil types and different injection pressure.

• Journal of the Korean Geotechnical Society
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• v.23 no.4
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• pp.5-13
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• 2007

Many construction projects adopt grouting technology to prevent the leakage of groundwater or to improve the shear strength of the ground. Recognition as a feasible field procedure dates back to 1925. Since then, developments and field use have increased rapidly. According to improvement of grout materials, theoretical study on grout penetration characteristics is demanded. Fluid of grout always tends to flow from higher hydraulic potential to lower one and the motion of grout is also a function of formation permeability. Viscosity of pout is changed by chemical action while grout moves through pores. Due to the increment of viscosity, permeability is decreased. Permeability is also reduced by grout particle deposits to the soil aggregates. In this paper, characteristics of new cement grout material that has been developed recently are studied: injectable volume of new grout material is tested in two different grain sizes of sands; and the method to calculate injectable volume of grout Is suggested with consideration of change in viscosity and clogging phenomena. The calculated values are compared with injection test results. Viscosity of new grout material is found to increase as an exponential function of time. And lumped parameter $\delta$ of new grout material to be used for assessing deposition characteristics is estimated by comparing deposit theory with injection test results considering different soil types and different injection pressures. Injection test results show that grout penetration rate is decreased by the increase of grout viscosity and clogging phenomena.

• Proceedings of the KIEE Conference
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• 1999.07b
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• pp.715-717
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• 1999

In this study, an intelligent solenoid valve controller has been developed for automatic maintaining of filters in a dust collecting system. This controller has automatic controllability of solenoid valves' ON/OFF time depending on the clogging status of filters, and then it can extend the filters' lifetimes, decrease the power consumption, and make effective operation of the system possible. This controllability has been executed by the fuzzy theory that utilizes the workers' experimental knowledges, the control expert's knowledges and the differential pressures between the inlets and outlets measured by the sensors.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.53 no.2
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• pp.82-88
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• 2004

In this study, an intelligent solenoid valve controller has been developed for efficient maintaining of filters in a dust collecting system. This controller has automatic controllability of solenoid valves' ON/OFF time depending on the clogging status of filters, and then it can extend the filters' lifetimes, decrease the power consumption, and make effective operation of the system possible. This controllability has been executed by the fuzzy theory that utilizes the workers' experimental knowledges, the control expert's knowledges and the differential pressures between the inlets and outlets measured by the sensors. The system's operation is under the continuous surveillance by using a current transformer, which warns the operators and lets them take necessary actions in case of abnormal operation.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.1929-1931
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• 2001

An adaptive fuzzy logic controller to regulate molten steel level in the strip casting process is presented, where parameters of fuzzy controllers are adapted stably by using Lyapunov-stability theory and a switching controller is used together to deal with the approximation error of fuzzy logic system. The level error is proven to converge to zero asymptotically. In the simulation, the clogging/unclogging of a stopper nozzle is considered and overcome by the proposed controller. Robustness to uncertainty is shown to be superior to conventional PI controller.