On the reliability of pipeless drainage

Abstract

Purpose: Based on the analysis of the performed theoretical, laboratory and field studies of cavityless drainage, both the authors of this article and other researchers established the conditions for ensuring the reliability of its operation during the standard service life. Methods: analysis of the causes and quantitative assessment of the entry of silting particles into the pores of drains from the soil surrounding the drain showed, that in the case of protection of drains from silting with geotextiles, the inflow of particles smaller than 0.05 mm is due to the fact that such particles are colmatizing and geotextiles, in accordance with the requirements for it, must pass them. Another source of their entry is the possibility of formation of filtration deformations at the contact of the drain filler with the surrounding soil when the filtration flow reaches velocities exceeding the erosive ones. Geotextile materials, which are widely used as protective and filtering materials, must pass water into the drainage in the spring, even while still in a frozen state. Results: it has been established that in the laminar regime, filtration deformations in cohesive soils at the contact of the filler with the soil surrounding the drain do not occur in the absence of vibrodynamic loading. In cavityless drainage used in industrial and civil construction, as well as in the case of draining agricultural fields, clogging particles let through by geotextiles reduce the cross-sectional area of drains by no more than 10%. When draining the railway subgrade by pipeless drainage, it is not advisable to protect the drain filler from above. At the same time, the height of the silted part of the drains does not exceed 10 cm for 100 years, which must be taken into account at the design stage. In the case of using geotextile materials as protective and filtering materials, their water loss coefficient μ should be ≥ 0.65 with porosity ≥ 0.8.