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The effect of lime admixture to trench backfill on the functioning of tile drainage in heavy soils
Author(s) -
Šaulys Valentinas,
Bastienė Nijolė
Publication year - 2006
Publication title -
irrigation and drainage
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.421
H-Index - 38
eISSN - 1531-0361
pISSN - 1531-0353
DOI - 10.1002/ird.262
Subject(s) - lime , drainage , soil water , tile drainage , water content , trench , geotechnical engineering , soil science , environmental science , environmental engineering , geology , chemistry , paleontology , ecology , organic chemistry , layer (electronics) , biology
Two sites in different locations in Lithuania were established for field experiments in order to assess the role of lime for drainage in heavy soils. Investigations were carried out in Pasvalys district and in Kalnujai located in Raseiniai district. The Pasvalys site was drained with single tile drains. Four different amounts of shale ashes (0.15, 0.30, 0.40 and 0.80% of active CaO for soil mass) were mixed with the silty clay soil and backfilled into drainage trenches. The results obtained show that (i) drainage coefficients ( q ) are strongly affected by the soil‐water content ( r = 0.82), and (ii) larger amounts of lime additives enhance water permeability of clay soil only to a certain degree. When water content increases from 23.0 to 27.0%, due to clay swelling, q decreases 13 times in non‐treated control variant. Adding lime to the trench backfill ensures stabilized clay soil structure and results in more stable q with increasing water content. With lime admixture of 0.15 and 0.30% CaO, q decreases 4.2 and 3.3 times respectively; with 0.40 and 0.80% CaO—only 2.6 times. The impact of lime on the drainage efficiency was most noticeable for lime admixture of 0.40% CaO. When the water content is less (23.0%), q values are 11 times higher than in the control variant; at higher water content (27%) q is even 55 times higher. A regression equation is given for the calculation of optimal lime rate to ensure the best water permeability in the trench. The Kalnujai site was drained by a composite subsurface drainage system, with drain spacing 16 and 24 m, drainage trenches backfilled with clay loam mixed with 0.6% CaO. The effect of drainage installation variants was evaluated on the basis of drain discharge and watertable depth in the main drainage season (January to April inclusive) in the period of 2000 to 2002. The peak drainage discharge measured in snow melt period was 6.7 mm d −1 , i.e. was 1.3 times higher than the design discharge (5.2 mm d −1 ) determined for a subsurface drainage according to soil texture and meteorological conditions. However, the differences of drainage discharge between the different treatments were insignificant. Lime amendments significantly lowered the watertable (0.21–0.25 m) and increased the surface water infiltration rate 1.5 times. Wider drain spacing from 16 to 24 m had no effect on water levels between drains and draining conditions in the area. Copyright © 2006 John Wiley & Sons, Ltd.