• Journal of Korean Society of Water and Wastewater
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• v.31 no.1
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• pp.21-28
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• 2017

This study was performed to propose the sewer defect scoring, and grading protocols for sewer condition assessment. For this, sewer defect scoring methods were comparatively analyzed and reviewed for four international condition assessment protocols, which are established based on WRc manual. As a result, we proposed a new protocol for sewer condition assessment, in which characteristics of sewer pipes are considered by segment. In reference to the PIM-3, the extent of ground subsidence was adopted to be of importance, and renewal scores increased in accordance with weighting of defects causing structural backfill materials. Also, defect grades of 'Hole' were extended to 5 levels of the grading, and 'Surface Damage' was excluded in defect assessment. The addition of 'Buckling' resulted in reduction of weights in 'Surface Damage' and 'Lining Defects'.

• Journal of the Korean Geosynthetics Society
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• v.17 no.3
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• pp.47-55
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• 2018

Recently, increasing number of urban ground subsidence occurrences has been identified. This situation is mainly due to the increased number of underground cavities. This study is intended to develop the method that prevents ground settlement caused by deteriorated or damaged sewers, which are the main cause of land subsidence. To that end, GPR exploration was conducted using CCTV monitoring of deteriorated sewer at the location with high settlement potential. Through such CCTV monitoring and GPR investigation, abnormal ground behavior was monitored at the site where sewer was damaged, joint was cracked and soil was deposited. According to site investigation in this study, evaluation method using correlation analysis of CCTV monitoring and GPR investigation results is expected to prevent ground settlement attributable to damaged sewer.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2008.11a
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• pp.358-363
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• 2008

도시 광역화와 인구의 집중에 따라서, 도시 거주민의 삶의 질 향상을 위해서는 많은 기반이 필요하다. 이중에서 깨끗한 위생 환경을 위해서 용수의 공급 및 하수의 처리는 매우 중요한 문제라고 할 수 있다. 이를 위하여 많은 조사와 보수가 이루어지고 있지만, 관로의 내면을 조사하는 다양한 기법은 활발하게 이루어지고 있는 반면, 도로의 침하나, 관로 내부로의 침입수 또는 침출수 등을 유발할 수 있는 관로 배면의 상태를 조사하는 기법은 아직 미비한 상태라고 할 수 있다. 따라서 본 연구에서는 이러한 관로의 배면에 대한 정보를 취득하기 위하여 매질을 통과하여 정보를 취득할 수 있는 지중탐사레이더(GPR)을 이용하여 관로의 배면 상태를 탐사하기 위한 기본 반사 특성을 조사하고 이를 기준으로 실제대상물의 반사 특성을 조사 분석하여 관로 배면 지반의 특성을 조사, 평가하고자 한다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.4
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• pp.421-431
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• 2023

Sewer deterioration models can offer important information on prediction of future condition of the asset to decision makers in their implementing sewer pipe networks management program. In this study, Markov chain model was used to estimate sewer deterioration trend based on the historical structural condition assessment data obtained by CCTV inspection. The data used in this study were limited to Hume pipe with diameter of 450 mm and 600 mm in three sub-catchment areas in city A, which were collected by CCTV inspection projects performed in 1998-1999 and 2010-2011. As a result, it was found that sewers in sub-catchment area EM have deteriorated faster than those in other two sub-catchments. Various main defects were to generate in 29% of 450 mm sewers and 38% of 600 mm in 35 years after the installation, while serious failure in 62% of 450 mm sewers and 74% of 600 mm in 100 years after the installation in sub-catchment area EM. In sub-catchment area SN, main defects were to generate in 26% of 450 mm sewers and 35% of 600 mm in 35 years after the installation, while in sub-catchment area HK main defects were to generate in 27% of 450 mm sewers and 37% of 600 mm in 35 years after the installation. Larger sewer pipes of 600 mm were found to deteriorate faster than smaller sewer pipes of 450 mm by about 12 years. Assuming that the percentage of main defects generation could be set as 40% to estimate the life expectancy of the sewers, it was estimated as 60 years in sub-catchment area SN, 42 years in sub-catchment area EM, 59 years in sub-catchment area HK for 450 mm sewer pipes, respectively. For 600 mm sewer pipes, on the other hand, it was estimated as 43 years, 34 years, 39 years in sub-catchment areas SN, EM, and HK, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.3
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• pp.585-592
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• 2017

Most sewer lines buried in the city are likely to be collapsed due to serious aging. Also, due to the high concentration of development and high population density and traffic, the collapse of the sewer will cause enormous social and economic damage. Therefore, proactive maintenance is required to prevent accidents caused by deteriorated sewer pipe. In order to utilize limited budget effectively, risk-based prioritization methods should be proposed that simultaneously consider the consequence of failure and the probability of failure. In this study, the method of risk-based prioritization of sewer was examined by reviewing various cases of overseas studies and applied to the urban sub-catchment. First, the impact factors that can be secured through the sewer GIS DB in Seoul were derived, and the weight, sub-criteria, and impact score of each impact factor were determined and the consequence of failure was calculated by weight sum method. In addition, the probability of failure was calculated by dividing the service life by the estimated useful life, and the consequence of failure and the probability of failure were classified into five grades by the Jenks natural breaks classification method. The prioritization method was applied to sub-catchment in the Seoul to derive a risk matrix and a risk grade. As a result, 26% of all subjects were selected as the inspection priority subjects with 4-5 risk grade. Therefore, using the risk-based CCTV prioritization methodology, it will be possible to systematically determine the objects that need investigation first.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.6
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• pp.623-634
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• 2016

Sewer condition assessment involves the determination of defective points and status of aged sewers by a CCTV inspection according to the standard manual. Therefore, it is important to establish a reliable and effective standard manual for identifying the sewer defect. In this study, analytic reviews of the CCTV inspection manuals of the UK, New Zealand, Canada and South Korea were performed in order to compare the defect codes and the protocols of condition assessment. Through this, we also established the standardized method for defect code and revised the calculation method of assigning the condition grade. Analyses of the types and frequencies of sewer defects that obtained by CCTV inspection of 7000 case results, showed that the joint defect and lateral defect were the most frequent defects that occurred in Korea. Some defect codes are found to be modified because those did not occur at all. This study includes a proposed new sewer defect codes based on sewer characteristics.

• Journal of the Korean GEO-environmental Society
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• v.19 no.7
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• pp.13-18
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• 2018

Recently, road subsidence has been increasing in urban areas, threatening the safety of citizens. In the lower part of the road, various road facilities such as water supply and drainage pipelines and telecommunication facilities are buried, and the deterioration of the facilities causes the road subsidence. In particular, in the case of old sewer pipes which are attracting attention as a main cause of road subsidence, the management of sewer pipe replacement, repair and reinforcement is being performed depending on the burial year. Therefore, in this study, we tried to suggest a reliable road subsidence risk assessment method considering various sewer specifications and surrounding environment information and CCTV exploration result and GPR exploration result.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2006.05a
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• pp.163-168
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• 2006

본 연구는 도시의 근간 시설인 하수도 관거를 관리하는데 있어 필요한 정보를 취득하기 위하여 사용되어왔던 과거의 폐쇄회로 카메라에 의한 영상 취득 방식이 가지고 있는 한계를 극복하고, 자세한 정보를 취득하기 위하여 영상을 이용한 도면화 방안에 대한 방법을 도출하는데 목적이 있다. 측면 카메라를 이용하여 취득된 영상을 수치영상처리과정을 통하여 처리하고, 영상 모자이크 기법을 적용하여 합성의 과정을 거친 후 위치 정보와 결합하는 과정을 통하여 하수관거에 대한 정밀한 정보를 취득하는 과정을 개발하였으며, 이에 필요한 장비를 개발하였다. 이러한 연구의 과정을 통하여 도출된 결과는 하수관거의 내부 정보를 정밀하게 취득할 수 있었으며, 향후 지형정보체계 등과 결합하여 효율적인 정보의 운용이 가능할 것으로 사료된다.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.8
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• pp.462-469
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• 2017

Eutrophication and shortage of phosphate ore raise the necessity of phosphate removal and recovery from wastewater treatment plants. Especially, a sludge treatment system containing highly concentrated phosphate should be targeted for phosphate removal and recovery. This study thus aimed to evaluate the capability of the struvite crystallization process for phosphate removal and recovery from a sludge treatment system of a wastewater treatment plant. Analysis on phosphate concentrations and masses in the sludge treatment system revealed that digested sludge and centrate have phosphate concentrations and masses, high enough to adopt the struvite crystallization process. Chemical equilibrium modeling indicated that the struvite crystallization reaction substantially occurred with pH higher than 8 and $Mg^{2+}$ concentration 1.2 times higher than its theoretical requirement. A series of batch tests with digested sludge and centrate indicated that the phosphate removal reaction by struvite crystallization followed a first-order kinetics and reached over 80% removal efficiency at equilibrium. Aeration in the batch tests was found to purge $CO_2$ in sludge or centrate and increase pH up to 8.7, without adding NaOH. Thus, we concluded that the struvite crystallization process could be an efficient and economical process for phosphate removal and recovery from a wastewater treatment plant.