اندازه گیری پیوسته ی درجه ی اشباع و مکش بافتی خاک های غیر اشباع با استفاده از دستگاه جدید منحنی مشخصه آب - خاک

در نوشتار حاضر، به بررسی عملکرد یک دستگاه جدید در بررسی تاثیر تراکم اولیه در اجزاء مختلف منحنی مشخصه‌ی آب خاک یک خاک ماسه‌یی پرداخته شده است. در دستگاه جدید، تغییرات مکش بافتی در بازه‌های خشک‌شدگی به صورت مستقیم و پیوسته و بدون نیاز به افزایش مصنوعی فشار هوای حفره‌یی توسط حسگرهای جدید مینیاتوری مکش بافتی اندازه‌گیری شده است. نتایج به‌دست آمده حاکی از کارایی حسگرهای جدید مینیاتوری مکش بافتی برای اندازه‌گیری مستقیم مکش بافتی خاک در مدت زمان در حدود 1 دقیقه و اندازه‌گیری کاملاً پیوسته‌ی منحنی مشخصه‌ی آب خاک در طول چند روز است. صحت عملکرد دستگاه جدید منحنی مشخصه‌ی آب خاک نیز با اندازه‌گیری مکش بافتی خاک در چند نقطه با استفاده از تنسیومترهای متداول بررسی شده است که نتایج به‌دست آمده حاکی از سازگاری مقادیر مکش بافتی اندازه‌گیری شده توسط هر دو روش است.

continuous measurement of matrix suction and degree of saturation of unsaturated soils with a new soilwater retention curve device

the relationship between matrix suction and degree of saturation within the soil is a fundamental parameter in studying many behavioral aspects of unsaturated soils and is referred to as the soilwater retention curve (swrc). due to difficulties associated with negative pore water pressure measurements in unsaturated soils, most swrc measuring techniques benefit from suction controlling methods such as axis translation or osmosis techniques. these methods provide only a few data points on the matrix suctiondegree of saturation relationship and cause a discrete measured soilwater characteristic curve. however, many swrc elements like drying and wetting curve slopes, air entry, and air expulsion values are fundamental parameters in describing the hydromechanical behavior of unsaturated soils. therefore, a realistic understanding of these parameters requires continuous measurement of the degree of saturationmatrix suction relationship at more points. to this end, this paper examines the performance of a new swrc device developed for the continuous measurement of the soilwater retention curve of unsaturated deformable soils along drying paths. the new apparatus is equipped with new miniature tensiometers enabling direct measurement of soil suction without the need for an artificial increase in pore air pressure. the variation of the degree of saturation is calculated by contiguous weighing of soil samples along drying paths. the credibility of the new swrc apparatus is examined to investigate the influence of initial compaction on the soilwater retention response of sandy soil along with drying. this was experimentally achieved by swrc tests on compacted soil samples with a range of void ratios between maximum and minimum void ratios to examine the influence of compaction on the slope of swrc along with drying and variation of air entry value. the results are thoroughly discussed and compared against other available data in the literature. also, the results suggest the fast performance of newly developed tensiometers for direct measurement of soil suction with a minute without the need for the application of elevated pore air pressure, which leads to the continuous swrc measurement of the soil samples within 3 to 5 days along drying paths. the credibility of the new swrc device is also examined with additional suction measurement tests using conventional jetfill tensiometers, showing consistent results.