• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.5
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• pp.836-841
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• 2012

The repair of road pavement and manhole has been resulted long construction times and traffic jams, environmental pollution from construction wastes, and budget waste due to excessive construction costs. In order to resolve such problems, we have developed the new construction method using C-ring, which can fix and raise the manhole securely. This technology is the method by driving in a wedge after inserting C-ring and expanding it in order to raise manhole to the regular height. This has been approved by the test reports of KOLAS(Korea Laboratory Accreditation Scheme), and was confirmed safety, durability and reliabilty in result. In this paper we approved this technology was able to short working times to around 20% and construction costs to around 50% with compare other construction methods. Also, environmental pollution and civil complaints will be prevented because there will be no longer any noises, vibrations, dust, or construction wastes.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.6
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• pp.619-625
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• 2008

Urban sewer systems are designed to operate in open-channel flow regime and energy loss at square manholes is usually not significant. However, the energy loss at surcharged manholes is considered as one of the major causes of inundation in urban area. Therefore, it is necessary to analyze the head loss associated with manholes, especially in surcharged flow. Hydraulic experimental apparatus which can change the manhole inner profile(CASE I, II, III, and IV) and the invert types(CASE A, B, C) were installed for this study. The experimental discharge was $16{\ell}/sec$. As the ratio of b/D(manhole width/inflow pipe diameter) increases, head loss coefficient increases due to strong horizontal swirl motion. The head loss coefficients for CASE I, II, III, and IV were 0.46, 0.38, 0.28 and 0.37, respectively. Side covers increase considerably drainage capacity at surcharged square manhole when the ratio of d/D(side cover diameter/inflow pipe diameter) was 1.0. The head loss coefficients for CASE A, B, and C were 0.45, 0.37, and 0.30, respectively. Accordingly, U-invert is the most effective for energy loss reduction at surcharged square manhole. This head loss coefficients could be available to evaluate the urban sewer system with surcharged flow.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.8
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• pp.996-1003
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• 2019

The undergrounding of diverse ground facilities has led to a decrease in issues, such as foul smell of water supply systems and wastewater, a fall of telephone poles, electromagnetic waves and breaking of wires caused by a railway work. On the other hand, there are new issues, including a fall accident, explosion affected by flammable gas, a choking accident by harmful gas and a lack of oxygen concentration, a fire coming from high-tension wire heating and flooding in the manhole. Besides, these issues damage the civil society and are an anxiety to public safety. Therefore, this paper is focused on a smart manhole device for stable communication environments inside and outside the manhole and wireless communication with various devices for managing facilities in the manhole, and aims to make a contribution to public safety by suggesting a direction of future underground facility management.

• Journal of Korea Water Resources Association
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• v.49 no.12
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• pp.1015-1025
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• 2016

In general, manholes installed as urban drainage facilities are a variety forms such as straight path manholes, 90 degree bend manhole, three-way combining manhole, and four-way combining manhole. In particular, the surcharged flow at a four-way manholes installed in the downstream of urban sewer system is the main cause of the urban inundation caused by the energy loss. Therefore, it is necessary to analyze the flow characteristics and estimate the head loss coefficients at surcharged four-way combining manholes. The hydraulic experimental apparatus which can change the manhole shapes (square, circle) and flow ratios were installed to estimate the head loss coefficients. In the experiments, two inflows ($Q_m$, $Q_{lat}$) were varied from 0 to $4.8{\ell}/sec$ and 24 combinations were tested in total. The flow ratios $Q_{lat}/Q_{out}$ were varied from 0 to 1 for a total flow $Q_{out}$ ($Q_{out}=Q_m+2Q_{lat}$) of 2, 3, 4, and $4.8{\ell}/sec$, respectively. The variation of head losses were strongly influenced by the lateral inflow because the head loss coefficient increases as the flow ratios $Q_{lat}/Q_{out}$ increases. It was estimated head loss coefficients of the circular manhole is slightly lower than those of the square manhole. However, there was no significant difference of head loss as discharges change. The range of head loss coefficients at four-way combining manhole according to the change of the lateral inflow ratio was estimated to be 0.4 to 0.8. Also, the relation equations between the head loss coefficients (K) and the lateral inflow ratios ($Q_{lat}/Q_{out}$) were suggested in this paper.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.3
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• pp.143-150
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• 2011

Energy loss at manholes, often exceeding friction loss of pipes under surcharged flow, is considered as one of the major causes of inundation in urban area. Therefore, it is important to analyze the head losses at manholes, especially in case of surcharged flow. The stream characteristics were analyzed and head loss coefficients were estimated by using the computational fluid dynamics(CFD) model, FLUENT 6.3, at surcharged square manhole in this study. The CFD model was carefully assessed by comparing simulated results with the experimental ones. The study results indicate that there was good agreement between simulation model and experiment. The CFD model was proved to be capable of estimating the head loss coefficients at surcharged manholes. The head loss coefficients with variation of the ratio of manhole width(B) to inflow pipe diameter(d) and variation of the drop height at surcharged square manhole with a straight-path through were calculated using FLUENT 6.3. As the ratio of B/d increases, head loss coefficient increases. The depth and head loss coefficient at manhole were gradually increased when the drop height was more than 5cm. Therefore, the CFD model(Fluent 6.3) might be used as a tool to simulate the water depth, energy losses, and velocity distribution at surcharged square manhole.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.3
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• pp.89-96
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• 2013

Now-a-days, a manhole adopted since the late 1990s and produced using the polymer concrete has widely used due to the various benefits. While entering the High oil prices times, however, and with the price increase of the petrochemical materials, the cost of manufacture of polymer concrete was elevated and the resulting polymer concrete's weakness is being put on. Accordingly, the development of economic cement concrete manholes, which can replace the outstanding bending strength of manhole made of high-price polymer concrete, has been required. In this study, based on the cement technology of fast hardening armorphous calcium aluminate (ACA), by minimizing the amount of cement using the industrial byproducts, to develop the eco-friendly high-toughness concrete manhole, which can reduce $CO_2$ reduction, was intended. As the results, the cement concrete manhole, which economic, eco-friend, and meeting the performance requirements, was developed.

• Journal of Korea Water Resources Association
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• v.45 no.8
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• pp.767-782
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• 2012

Accumulation of sediment within pipelines, manholes, and other components of urban sewer systems can have a bad influence on sewerage arrangements, such as the resistance of the passage of flows, the cause of urban flooding and the premature operation of combined sewer overflows, and the inevitable pollution of watercourses. Therefore, it is necessary to understand the movements and sedimentation of sediment loads in combining junction manholes by experiments. In this study, hydraulic experimental apparatus which can change the manhole shapes (square, circle) were installed to measure deposited sedimentation quantity. The quantity of deposited sediment loads was measured by different conditions, for instance, the inflow conditions of sediment (continuous and certain period), the amount of inflow sediment, and the variation of inflow pipe of sediment. The combining junction manhole that was set up a inclined benching have the considerable effect of reduction of sedimentation in manholes without apropos of the change of manhole shapes. Therefore, the improved manhole could be increased the drainage capacity of sewerage arrangements in urban sewer systems.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.427-427
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• 2021

During the rainy season, heavy downpours are always a source of concern for the world. Flooding and heavy rains can devastate communities, disrupt agriculture, and contribute to traffic accidents.. Weir and flow hall effect sensors are the conventional analytical methods for measuring flow rate; in this paper, we analyzed manhole flowrate statistics. The measurement of the flow rate of a notch/weir is a time-consuming task that necessitates continuous mathematical analysis. . We created three types of IoT sensors in this study: (HC-SR04 ultrasonic, YF-S201 magnetic, and HB100 radar), which take the sensor's real-time input signal and estimate the flow using a notch equation and a previously calibrated optimized coefficient of discharge. The proposed systems are cost-effective, but in terms of accuracy, we found that the HC-SR04 ultrasonic sensor is the best of the three systems

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.19 no.4
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• pp.381-389
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• 2009

Confined spaces are inherently dangerous workplace and many fatal and nonfatal accidents have been reported. Even though these accidents occur in various kinds of confined spaces, there has rarely been reported on the health hazard agent, i.e., the types of gases and their concentration ranges. Therefore in this study, we evaluated several toxic and asphyxiating gas concentrations in various confined spaces. We surveyed 57 manholes, 3 sewage treatment plants, 2 yellow radish manufacturing companies and 7 barges to measure the concentrations of oxygen($O_2$), hydrogen sulfide($H_2S$), carbon monoxide(CO), ammonia($NH_3$). Lower Explosion Limits(LEL) and Volatile Organic Compounds (VOCs). Those four types of confined spaces occupies 56% of accidents during last 9 years in Korea. In 57 manholes, the concentration varied according to the types of manholes; rainfall and sewage, and by location; residential and industrial areas. Sewage manhole in industrial area was evaluated as the most hazardous than other types of manhole like rainfall manholes, residential sewage manholes. The highest $H_2S$ concentration and the lowest $O_2$ concentration at sewage manhole in industrial area were 300 ppm, 8.7% respectively. In 3 sewage treatment plants, $H_2S$ and $NH_3$ concentrations were reached up to the 500 ppm and 200 ppm respectively. Two yellow radish manufacturing companies showed the concentrations of 316 ppm, 505.2 ppm, 90 ppm and 15.7% for $H_2S$, CO, VOCs and $O_2$, respectively. Seven barges showed 15.9%~20.9% oxygen concentration. Gas species and concentration ranges varied by the types and location of confined spaces; CO, $H_2S$, $O_2$ could be hazardous in manhole, especially manhole connected to sewage plants. CO, $H_2S$, LEL, $O_2$, $NH_3$ should be controlled in sludge silo and sluge pumping confined spaces in sewage treatment plant. The activity of lifting out radish from the storage tank was evaluated more hazardous rather than the other activities in yellow radish manufacturing industry. The employers must conduct the survey to identify all possible confined spaces in their local workplace prior to performing the tasks. At the national level to reduce the accidents in the confined spaces, we suggest that systemic approach and active education program including possible hazards, standard operation procedures, ventilation plan, and personal protective equipment in confined spaces should be implemented.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.521-528
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• 2013

Urban drainage systems are generally designed as open channel flow. The system, however, shows a partially surcharged flow in its body, especially at junctions or manholes. Thus, a special case of this condition needs to be explained as pressurized flow condition for designing the sewer system. This study considered the surcharged manhole flows during an unexpected rainfall event or an excess of design frequency. Overflows from surcharged manholes and urban flooding can occur from the effect of surcharged flows. Thus, sewer systems should be designed with the concept of open channel flow and pressurized flow. Also, energy losses in a manhole need to be considered. The aim of this study is to develop the numerical model which can evaluate the effect of the energy losses at the manhole. The numerical model was verified and compared with hydraulic model and SWMM. The results showed that the water depth of numerical model was in good agreement with hydraulic model at the each manhole. However, the SWMM underestimated the water depth because that model ignored the energy losses at manholes. Thus, the developed numerical model in this study could be a useful tool for the assessment of a conveyance of urban drainage system.