Erosion of irrigation facilities in Cambodia paddy farming region and the measures for protection

摘要

This study investigates the erosion condition of irrigation earth structures and determines the measures for erosion protection in Cambodia paddy farming regions. Most irrigation facilities are earth structures (embankment), and due to heavy rainfalls and high erodible soils used for construction of embankments, the occurrence of erosion has increased in irrigation systems. Two irrigation sites: Thomney and Kandal Steung, were selected to investigate the situation of erosion on embankments and soil properties. The soils were consequently identified as sandy clay or sandy silt, and they have a low resistance to erosion process. The field densities were measured, and the compaction degrees of the embankments D values existed within 81-88% indicated as a loose condition. One attempt of the use of cemented soils has been conducted to prevent further erosion for one paddy farming region in Thomney. To clarify fundamental mechanical properties and effectiveness of cemented silty soils, a silty soil named DL clay mixed with cement was used and tested under triaxial consolidated and drained conditions. In triaxial compression tests, 30 specimens with 3 confining pressures: 50, 100 and 200 kPa, 4 cement contents: 0, 3, 5 and 7%, and 3 curing times: 7, 14 and 28 days, were tested. The results showed that peak shear strength of the cement mixed soil increased with an increase in cement contents. The peak strength values until 91 days normalized by the peak strength q(f7) at 7 days curing time could be estimated by a hyperbolic equation of curing time t.