Reproducing Field Measurements Using Scaled-Down Hydraulic Model Studies in a Laboratory

Little efforts have been made to the value of laboratory model study in closing the gap between results from idealized laboratory experiments and those from field data. Thus, at first, three bridge sites were selected and equipped with fathometers to find the bed elevation change in the vicinity of bridge pier over time. After and during the flooding, the stream flow variables and their bathymetry were measured using current viable technologies at the field. Then, to develop and suggest a laboratory modeling techniques, full three-dimensional physical models including measured river bathymetry and bridge geometry were designed and fabricated in a laboratory based on the scale ratio except for the sediment size, and the laboratory results were compared with the field measurements. Size of uniform sediment was carefully selected and used in the laboratory to explore the scale effect caused by sediment size scaling. The comparisons between laboratory results and field measurements show that the physical models successfully reproduced the flow characteristics and the scour depth around bridge foundations. With respect to the location of the maximum scour depth, they are not consistent with the results as in the previous research. Instead of occurring at the nose of each pier, the maximum scour depths are located further downstream of each pier column in several experimental runs because of the combination of complex pier bent geometry and river bathymetry, and the resulting unique flow motions around the pier bent

Multidirectional instability of the shoulder – current concept

A guest editorial on the multidirectional instability of the shoulde

A Study on water shut off period and countermeasure for effective water supply maintenance

Thesis(Master) -- KDI School: Master of Public Management, 2022Since the 1960s, Korea''s water supply has been rapidly expanded through state-led facility investment along with economic development, with 99.4% of the people receiving water supply services as of 2020. Korea''s water supply has reached the world''s highest level in terms of facility capacity and supply rate, but as of 2020, 34.8% of Korea''s buried water pipes have passed more than 20 years and their performance is rapidly decreasing. In 2019, 630,000 citizens were damaged by the supply of discolored tap water for up to 67 days due to inappropriate work procedures, and waterworks business operators suffered more than KRW 6.6 billion in financial losses due to compensation for citizens'' damage. It is time to pay attention to maintenance to preserve stable functions so that this situation does not occur again, and the Ministry of Environment recently enacted ‘Detailed Standards for Maintenance of Waterworks Network Facilities’ to require water supply businesses to conduct regular water pipe cleaning. However, like other maintenance tasks such as emergency construction and altering waterworks system, cleaning of water pipes will cause shut off of tap water supply unless it is under special conditions such as double track supply. Accordingly, measures to improve the efficiency of maintenance work and reduce citizens'' inconvenience were investigated through interviews with experts in consideration of loss, such as civil inconvenience, and benefits from regular maintenance of water facilities. Based on the experience of experts, the results of analyzing the optimal time and interval for maintenance work to the level of dissatisfaction of citizens according to water shut-off and finding out promotional and support measures to minimize dissatisfaction in the event of water shut off are as follows. f there is sufficient prior notification of water shut off, citizens should not sensitively complain of discomfort until the water shut off duration of 12 hours and should perform it during late night time (23:00-05:00) when water consumption is low. In addition, detailed work schedules for each time period should be established in consideration of citizen inconvenience such as noise from excavation work at night, and maintenance work needs to be carefully planned at intervals of at least one month to prevent citizen inconvenience caused by repeated water shut-off. As a way to minimize inconvenience to citizens in the event of water shut-off, it is most important to notify citizens in advance, and it is desirable to notify them about a week in advance by various ways, such as sending individual SMS and posting banners. On the other hand, frequent guidance should not cause inconvenience to citizens due to the burden of fatigue. In addition, it was suggested that if water shut-off is to be carried out for a long time, a plan to support bottled water and water-tank trucks to be provided to the victims should also be set up.1. Introduction 2. Literature review. 3. Research questions and method 4. Research results. 5. Policy or Administrative Recommendations 6. ConclusionmasterpublishedSeung-Ho LE