The Rehabilitation of Drainage Canal Embankment

Thanadol Kongsomboon

Civil Engineering Department, Srinakarinwiroj University, Rangsit-Nakorn-Nayok Road, Ongkarak Nakornnayok, 26120, Thailand.


The new drainage canal is a main water flood drainage channel from the north Samrong canal at Samutprakarn province to the Gulf of Thailand. The construction of the canal involves excavation in very soft clay. Which a group of soil-cement columns (diameter: 0.6 m, length: 8-15 m) was used to reinforce the soil slope and road foundation. During a test excavation, a soil failure occurred even when its Factor of Safety; F.S. = 1.3 (during construction period) and F.S. = 1.5 (working period) was calculated by slope stability analysis. This result implied that conventional slope stability analysis method that considers only a force ratio may not be appropriate for analyzing very soft soil reinforced with a very high modulus material like a soil cement column. It was possible that, the strain compatibility behaviour of two materials was not considered. Because of a high displacement of very soft clay decreased its modulus to develop shear strength. Its behaviour becomes like a liquid flow even it was designed with a high safety factor. The remedial slope failure concept is considered therefore not only an enough shear resistant of soil cement column but also reducing an active force by transferring a soil weight to a hard layer beneath and increasing a passive force using a soil berm as well as a quickly drain water in the excavation pond after finishing the excavation. However, a slope failure can also be prevented by proper construction control which could reduce the rate of lateral displacement.

Keywords: Slope failure; soil-cement column; earth reinforcement.

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