همبستگي سرعت موج برشي و مقاومت روان‌گرايي ماسه با ريزدانه‌ي غيرخميري

Correlation between Liquefaction Resistance and Shear Wave Velocity of Sand Containing Non-Plastic Fines

در اين مطالعه با انجام آزمايش‌هاي المان خمشي و سه‌محوري تناوبي، سرعت موج برشي و مقاومت روان‌گرايي يك نوع ماسه‌ي تميز و همچنين تركيب‌هاي مختلف آن با ريزدانه‌ي غيرخميري تا 25? اندازه‌گيري شده است. روش ساده‌ي نيمه‌تجربي- نيمه‌تحليلي براي ايجاد همبستگي بين سرعت موج برشي و مقاومت روان‌گرايي پيشنهاد شده است. ضمن بررسي تاثير ريزدانه‌ي غيرخميري در سرعت موج برشي و همچنين مقاومت روان‌گرايي ماسه‌هاي سيلت‌دار، تاثير ريزدانه‌ي غيرخميري در همبستگي اين دو پارامتر بررسي شده است. نتايج حاصل نشان‌دهنده‌ي كاهش سرعت موج برشي و همچنين مقاومت روان‌گرايي با افزايش سيلت به ماسه است. براساس نتايج پژوهش، همبستگي سرعت موج برشي و مقاومت روان‌گرايي تركيب‌هاي مختلف ماسه و ريزدانه‌ي غيرخميري، خاص آن تركيب است. روش‌هاي موجود ممكن است مقاومت روان‌گرايي ماسه‌هاي سيلت‌دار را دست كم و يا دست بالا پيش‌بيني كنند.

Soil liquefaction is one of the most complex and destructive geotechnical phenomena and, therefore, several methods have been used for the evaluation of liquefaction potential, among which the simplified method is mostly used. In this method, which is mainly based on the standard penetration test (SPT), cone penetration test (CPT) and shear wave velocity (Vs) measurement, a boundary curve is provided to separate liquefiable and non-liquefiable soil zones. Shear wave velocity measurement is a good alternative method to penetration-based methods (SPT and CPT tests). This is especially true in micro-zonation of the liquefaction potential. Although relatively large studies have been carried out to establish the correlation between shear wave velocity and liquefaction resistance for sands; there are uncertainties about the effects of non-plastic fines on the correlation. The objective of this research is to study the effects of fines on the correlation of shear wave velocity and liquefaction resistance. In this regard, cyclic triaxial and bender elements tests have been performed, and shear wave velocity and the liquefaction resistance of clean sand, and combinations of this sand with non-plastic fines up to 25%, have been measured. A simple, semi-empirical, semi-analytical method is proposed to establish a correlation between shear wave velocity and liquefaction resistance. The effects of non-plastic fines on the shear wave velocity and liquefaction resistance of silty sands have been examined in this study, and the effects of non-plastic fines on the correlations between these two parameters are considered. The results in this study show that an increase in the ratio of silt to sand will result in a decrease in shear wave velocity and liquefaction resistance. Based on these results, it is argued that the correlation between the shear wave velocity and liquefaction resistance of various combinations of sand and non-plastic fines is soil specific. Also, based on the results of this study, it is found that existing methods of liquefaction potential evaluation based on shear wave velocity may underestimate or overestimate the liquefaction resistance of silty sands.