2استاد گروه مهندسی عمران،دانشگاه شهید باهنر کرمان،کرمان،ایران
چکیده
روانگرایی پدیده‌ای است که طی آن رسوبات سست اشباع هنگامیکه تحت بارهای دینامیکی قرار می‌گیرند، مقاومت شان بطور چشمگیری کاهش یافته و یا از بین می‌رود لذاشناخت هر چه بهتر روانگرایی و عوامل موثر بر آن اهمیت زیادی دارد. در تحقیق حاضر تأثیر دانسیته نسبی و میزان ریزدانه غیرخمیری بر پتانسیل روانگرایی و نشست ماسه اشباع با استفاده از دستگاه میزلرزه بررسی شده است .نتایج حاصله نشان می دهند که با افزایش تراکم نسبی حتی درتکانهای نسبتاً شدید، فشار آب حفره‌ای بطور محسوسی کاهش یافته و در دانسیته های بالا نیز احتمال روانگرایی کاملاً از بین می رود. بعلاوه مقدار نشست سطحی خاک نیز بصورت قابل توجهی کاهش خواهد یافت. همچنین با زیاد شدن مقدار ریزدانه غیرخمیری، فشار آب حفره‌ای افرایش و در مقابل میزان نشست خاک کاهش خواهد یافت. بعلاوه با افزایش میزان دانسیته نسبی و در درصدهای سیلت بالا، حالت روانگرایی سریعتر از بین می رود.
Laboratory study of the effects of relative density and non-plastic fines on liquefaction potential and settlement of saturated sand
نویسندگان [English]
Hadi Bayati1؛ mohammad hossein bagheripour2
1Shahid Bahonar University of Kerman, Kerman
2Professor of Civil Engineering department, Shahid Bahonar University of Kerman, kerman, iran
چکیده [English]
In liquefaction occurrence, shear strength of loose cohesionless deposits of saturated soil is considerably reduced or even is lost when subjected to dynamic or seismic loads. The earthquake-induced liquefaction can cause significant damage to existing facilities and structures. It is, therefore, of prime importance to deeply understand the liquefaction mechanism and the related and affecting parameters on this phenomenon. In the current study, using a semi- automated shaking table, the effect of the relative density and the percentage of non-plastic fine content of soil material on the liquefaction potential and the settlement of saturated sand layers were investigated. Acceleration of the shaking table in all tests was adopted to be constant and equal to 0.3g having a frequency of approximately 4.7 Hz. In contrast to many other researchers conducted in recent years, loose and very loose sands are considered for experimental studies. Further, shaking table studies conducted here on these materials are considered as relatively large scale tests which notably differ from those conducted mostly by common triaxial tests in the past. The results obtained showed that the higher the relative density, the lesser is the pore water pressure even if the shaking level is high and that the probability of liquefaction is reduced to the lowest level. In addition, the surface settlement of soil layer is significantly reduced. It was also observed that, despite the existing challenges and even opposing point of views among researchers, an increase in the percent of non-plastic fine content in the soil material would lead to a reduction in settlement of soil layer and, ironically, to an increase in pore water pressure. Other observations on the experiments conducted in this research verified that the time during which soil remains in liquefied state is reduced if and/or percentage of fine content of soil material is high.
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