The impact of agriculture drainage reconstruction on ground water recession close to the subgrade

Abstract

Good drainage to be the most important design consideration for a road, both to miniaturize road maintenance costs and maximize the time the road is operational. The lack of good drainage can lead to the infiltration of water into the road structure leading to structural damage and costly repairs. Many of roads are built in intensive drained agricultural land. The effective way to drain subgrades can be reconstruction of existing agricultural drainage. The impact of cross-subsurface drainage system on water level fluctuation was measured using PLAFI (Plane geofiltration mathematical model), one of 3D geofiltration modelling programs. The hydraulic permeability characteristics were determined in field of Pikeliai, close local road in Kėdainiai district, Lithuania. This object is composed of clay and loamy soils. Subsurface cross drains trenches spacing of 20, 30, and 40 m were simulated. The hydraulic permeability of cross drain trenches and lateral trenches modelled was from 0.006 m/a day to 6 m/a day. The simulation of cross drains trenches showed that the most effective distance between them are 20 m. The highest water depression occurs when the permeability of cross drain trenches and lateral trenches is ~ 6 m/day, at the distance of 20 m. The water recession is 20 cm lower, compared to the drainage systems without cross drains trenches. By installing cross drains trenches every 30 m water recession is 10 cm lower, when the trench ground permeability is about 6 m/day. Increasing the distance between the cross drains trenches up to 40 m, their influence disappears.