초록
홍수터여과에서 원수공급체계의 설계인자를 얻기 위해 모래통 실험과 현장 출수대 실험을 수행하였다. 모래통 실험결과 침투율은 대략 토양의 투수계수에 비례하였으며, 짧은 시간의 휴지는 침투율에 거의 영향을 주지 않았다. 범람과 휴지를 고려한 일평균 침투율은 범람이 길어질수록 증가하여 일정한 값에 수렴하는 경향을 나타냈다. 실험범위에서는 대구와 물금의 토양에서 휴지/범람이 15분/30분일 때 최대 침투율로 각각 6.3 m/day와 1.4 m/day을 얻었으며, 이 값들은 포화투수계수 값의 42%와 70%씩이었다. 토양여과로 인해 투수계수는 완만히 감소하였으며 물금토양에서 8일 동안 27%가 감소하였다. 출수대 실험결과 상주와 구미의 토양에서는 유출유량이 증가함에 따라 범람반경이 증가하며 토양의 포화 투수계수가 클수록 그 증가율은 감소하는 형태를 보였다. 토양면을 완전히 적시는데 필요한 시간 즉, 유출 시작으로부터 범람반경에 도달하는데 필요한 시간은 3~4분에 불과한 것을 알 수 있었다. 또한, 1시간 이내의 휴지시간을 적용하는 경우 전체 범람시간 동안의 평균 침투율에는 거의 변화가 없었다.
Sand tank experiments were performed along with on-site supplier experiments in order to obtain design factors for the raw-water supply system in floodplain filtration. Results of the sand tank experiment elucidated that the infiltration rate was approximately proportional to the soil permeability and was not significantly influenced by short periods of rest. The average daily infiltration rate calculated by taking both flood and rest periods into account increased with increasing flood period, and was observed to reach an asymptote. Under the conditions of this study, the maximum infiltration rates obtained for both Daegu and Mulgeum soils with 15 min/ 30 min of rest/flood periods were 6.3 m/day and 1.4 m/day respectively, which were 42% and 70% of their hydraulic conductivities, respectively. The process of soil filtration resulted in a gradual decrease of hydraulic conductivity; a decrease of 27% was observed for the soil of Mulgeum over a period of 8 days. From the data obtained from the supplier experiment, it was evident that the radius of the flooded area increased as the supply rate increased for soils of Gumi and Sangju, however, there was an inverse correlation between hydraulic conductivity and the rate of increase in the radius. Results also showed that the time required to cover the entire soil surface with water, in other words, the time to reach the maximum flood radius from the commencement of the water emission was as short as 3 to 4 minutes for all the soils. Also, the average infiltration rate for the entire flood period did not change significantly when the rest period was shorter than an hour.
