بررسي تاثير تثبيت‌كننده‌هاي شيميايي نوين در فرسايش داخلي در سدهاي خاكي

Investigation of Effectiveness of Modern Chemical Stabilizers on Internal Erosion in Embankment Dams

فرسايش داخلي دومين عامل اصلي تخريب سدهاي خاكي پس از سرريزشدن آب از تاج سد است. از اين رو مهم است كه مقاومت فرسايشي خاك‌ها با استفاده از روش‌هاي موثر و با هزينه‌هاي مناسب بهبود داده شود. يكي از كارهاي موثر جهت جلوگيري از فرسايش داخلي در سدهاي خاكي، استفاده از تثبيت‌كننده‌ها جهت اصلاح پتانسيل فرسايش خاك‌هاست. در اين پژوهش، از ماده‌ي شيميايي بر پايه‌ي ليگنين، ليگنوسولفونات جهت اصلاح فرسايش‌پذيري ماسه‌ي رس‌دار كايولينيتي استفاده شده است. بدين منظور ماسه‌ي رس‌دار كايولينيتي به‌صورت مجزا و سپس اختلاط با درصدهاي مختلف ليگنوسولفونات مورد آزمايش فرسايش در هدهاي مختلف قرار گرفته است. نتايج نشان مي‌دهد كه فرسايش‌پذيري ماسه‌ي رس‌دار كايولينيتي بسيار سريع است، كه با افزايش مقدار ناچيز ليگنوسولفونات به آن، فرسايش‌پذيري مصالح به طور چشمگيري كاهش مي‌يابد؛ به‌طوري ‌كه با اضافه‌كردن 3% ليگنوسولفونات به ماسه‌ي رس‌دار كايولينيتي، ضريب فرسايش خاك از 01020/0 به 000017/0 و فرسايش‌پذيري كيفي از گروه به‌شدت سريع به گروه نسبتاً آهسته كاهش مي‌يابد.

The two most common causes of earthen embankment failure are embankment overtopping and internal erosion. In order for a failure to occur from internal erosion or overtopping, three conditions must be met: There must be an existing flow path, there must be a source of water, and the hydraulic stresses must be great enough to cause the detachment of material. Due to internal erosion of an earth dam, water seeping through it carries soil particles away from its embankment, foundation, or abutments. Internal erosion may be a result of inadequate compaction during construction, differential settlement, desiccation, earthquakes, burrowing animals, and/or vegetation roots. The erodibility of the material in the internal erosion flow path and hydraulic stresses are the most important factors in determining the rate of erosion. The challenge in predicting failure due to internal erosion, is characterizing the material properties relevant to the rate of failure. Therefore, it is very important to improve the erosion resistance of soils using appropriate and cost effective techniques. Using chemical stabilizers is one effective method of preventing internal erosion in earth dams. In this study, a chemical stabilizer based on lignin; lignosulfonate, has been used for the treatment erodibility of kaolinity clay sand. The new stabilizer, lignosulfonate, is utilized to evaluate its effectiveness in increasing erosion resistance. To conduct this research, kaolinity clay sand has been treated with different dosages of lignosulfonate and tested with hole erosion apparatus under different hydraulic gradients. The results indicate that the erosion rate of kaolinity clay sand is extremely rapid, and chemical lignosulfonate stabilizer increases the resistance of kaolinity clay sand to erosion. It was also found that the erosion coefficient of erodible soil (kaolinity clay sand) decreased from 0.01020 to 0.000017 with the addition of 3.0% lignosulfonate, and its description has been changed from extremely rapid to moderately slow erosion.