تثبيت ماسه‌ي سيلتي مسيله‌دار با استفاده از ميكروسيليس و آهك جهت كاهش ميزان تورم و افزايش توان باربري

Stabilization of Problematic Silty Sands using Microsilis and Lime to Decrease Swelling Potential and Increase Bearing Capacity

ماسه‌ي سيلتي سولفاته، خاك تشكيل‌دهنده‌ي مناطق وسيعي از كوير مركزي ايران است، كه مقاومت فشاري ناچيز و پتانسيل تورم زياد ناشي از وجود سولفات گچ دارد. راه‌سازي در اين مناطق مستلزم تثبيت خاك بستر و لايه‌هاي روسازي است. در اين پژوهش، با افزودن درصدهاي مختلف ميكروسيليس و آهك و انجام آزمايش‌هاي مقاومت فشاري محدودنشده، CBR و تورم تثبيت اين خاك مورد مطالعه قرار گرفته است. نتايج آزمايش‌ها نشان مي‌دهند كه با مقادير بسيار كم ميكروسيليس و آهك، مقاومت نمونه‌ها به‌طور چشمگيري افزايش و پتانسيل تورم كاهش مييابد. عدد CBR نمونه‌ي تثبيت‌شده با 1% ميكروسيليس و 1% آهك حدود 80 به دست آمد كه براي عمليات راه‌سازي بسيار مناسب است. عكس‌برداري ميكروسكوپ الكتروني هم نشان‌دهنده‌ي نقش اصلي ميكروسيليس در تشكيل ريزساختارهاي كريستالي و در نتيجه، افزايش قابل توجه مقاومت نمونههاي تثبيت‌نشده‌ي خاك است.

Silty sands contain sulfates, which are the main constituents of the central desert of Iran. Due to the presence of sulfates, a dilative behavior is observed. Also, the unconfined compressive strength of this kind of soil is negligible. These two mentioned reasons make it an unsuitable construction material for roads. In order to make it an applicable material in road construction, it should be effectively stabilized. In this study, to investigate the behavior of stabilized silty sands, two different additives, microsilis and lime, were added to the built samples in different percentages. Then, the unconfined compressive strength (UCS) test, California bearing ratio (CBR) and swelling test were conducted on the stabilized samples. Furthermore, to truly study and interpret the changes in the soil structure as a consequence of stabilization, the SEM technique, scanning electron microscope, was implemented. The results obtained from the experimental study show that adding microsilica microsilis and lime together to the sulfate silty sand was conducive to causing a considerable rise in the value of the CBR number. Moreover, the swelling potential of the samples was decreased by adding the additives, and actually decreased the swelling of the samples. Nevertheless, adding 1% lime without any amount of microsilis considerably increased their swelling potential. In addition, the results conferred from the scanning electron microscope emphasized that by adding microsilica microsilis to the samples, crystalline textures will be made in the internal structure of the samples. As an important result, the mixture of 1% microsilis-1% lime was shown to be the optimum additive for usage in construction projects, and made the samples show unconfined compressive strength 12 times higher than the intact samples.