ارزیابی استاتیکی و چند‌مرحله‌یی مقاومت بیرون کشش ژئوسل ها در خاک های دانه یی

به منظور بررسی رفتار بیرون‌کششی استاتیکی و چندمرحله‌یی ژئوسل‌ها در خاک‌های دانه‌یی، یک مطالعه‌ی آزمایشگاهی به وسیله‌ی دستگاه بیرون‌کشش زرگ‌مقیاس انجام شده است. آزمایش‌های بیرون‌کششیِ سرعت ثابت و چندمرحله‌یی به ترتیب برای بررسی رفتار استاتیکی، تناوبی و پساتناوبی ژئوسل مدفون در خاک‌های دانه‌یی ترتیب داده شده است. مقاومت بیرون‌کشش نهایی به‌دست آمده از آزمایش بیرون‌کشش، شامل: مولفه‌های متفاوتی است که هر یک از آن‌ها توسط یک روش تئوری محاسبه شده است. درنهایت مشاهده شد که رفتار بار بیرون‌کشش جابه‌جایی ژئوسل‌ها به صورت سخت‌شونده بوده است که مقدار آن وابسته به مولفه‌ی مقاومت پاسیو و اصطکاکی بسیج شده است. همچنین مقاومت بیرون‌کشش نهایی پساسیکلی به‌دلیل شکسته یا ضعیف شدن برخی از قفل و بست‌ها بین دانه‌های مصالح پُرکننده و خاک اطراف در هنگام حرکت رفت و برگشتی فاز سیکلی، کمتر از مقاومت نهایی استاتیکی بوده است.

evaluation of the static and multistage geocell pullout behavior in coarse grained soil

geocell mattresses are one type of threedimensional honeycomb soil reinforcements that is manufactured from polyethylene sheets using ultrasonically welded joints. this type of geosynthetics is commonly used to stabilize geotechnical problems in which the pullout failure is likely to occur. the present study has been conducted to evaluate the pullout behavior of a geocell by considering the effect of soil grain size. a series of 18 monotonic and 24 multistage geocell pullout tests were performed in sandy and gravely soil. the obtained geocell pullout loads were divided into two components: passive and frictional resistance. a previously made theoretical approach was used to measure the mobilized frictional and passive resistance components to evaluate the contribution of each mechanism. the results obtained from monotonic geocell pullout tests showed that the geocells exhibited hardening pullout behavior and the pullout failure occurred when the geocell material did not have any more pullout capacity to resist external load. increases in the geocell height and soil grain size had significant effects on the passive component and it was seen that the contribution of geocell height developed passive resistance higher than the soil grain size. furthermore, the multistage test results indicated that for removal of the geocell, the ultimate postcyclic pullout load was less than the monotonic pullout load. this was the result of a reciprocating motion from loading caused by the interlock between the geocell infill soil and the surrounding material, which weakened and broke during the cyclic phase. as the coarseness of the soil increased, the interfacial strength increased. the theoretical approach did not single out the passive component between monotonic and multistage tests and the obtained passive resistance values were the same in these calculations. however, the cyclic loading could affect this component. also, the soil particle size had a significant effect on the cumulative displacement during the cyclic phase.