Salt Drainage Efficiency and Anti-Clogging Effects of Subsurface Pipes Wrapped with Geotextiles

Abstract

Subsurface drainage pipes covered with filters and geotextiles are the key to preventing clogging and ensuring efficient drainage. To improve the salt discharge efficiency of these subsurface drainage pipes, different layers of geotextiles were set outside the pipes with the aid of uniform gravel filters. This paper reports our findings from laboratory simulation of subsurface drainage pipes and experiments. The study examined the influence of different layers of geotextiles on the drainage efficiency, salt discharge effects of subsurface drainage pipes, and the effect of superimposed geotextiles on the salt drainage efficiency as well as the anti-clogging effect of subsurface drainage pipes. The results are as follows: (1) The geotextile and filter material wrapped around the subsurface pipe facilitated the movement of water towards the subsurface pipe, which could promote the salt discharge of the subsurface pipe. However, in the single leaching experiment, the reduction in soil pH was not significant for different scenarios. (2) The salt removal rate of the geotextile-wrapped subsurface pipes was more than 95%. The salt removal rate of the double-layer geotextile scenario was the highest (96.7%), and the total salt content of soil profiles was 8.3% and 31.3% lower than those of the single-layer and triple-layer geotextile scenarios, respectively. The drainage efficiency of the double-layer geotextile scenario was the highest, and the salt distribution in the 0–60 cm profile was relatively uniform, ranging from 2.3 to 3.0 g∙kg−1. (3) The clogging in the triple-layer geotextile scenario was caused by the geotextile, i.e., a dense filter cake layer formed on the surface of the geotextile. The clogging in the single-layer and double-layer geotextile scenarios was the clogging of the geotextile itself, i.e., soil particles retained in the fiber structure of geotextiles. (4) In the case of the single-layer and double-layer geotextile scenarios, the soil particles failed to completely clog the selected geotextiles, and there were still a large number of pores retained. The double-layer geotextiles integrate filtration, clogging prevention, and drainage promotion to provide the best salt drainage with the subsurface pipe. This study reveals the influence of the filter on soil water salt and salt discharge and provides a theoretical explanation and technical justification for the application of the subsurface pipes salt discharge technology in saline soil ameliorate.