بررسي عددي تأثير سيستم كيسه - خاك در بهبود ظرفيت باربري ژئوتكنيكي خاك بستر

Numerical study of the effect of soilbag system to improve geotechnical bearing capacity of the bed soil

به‌كارگيري عناصرتسليح كننده در بهسازي و اصلاح خواص مهندسي خاك از ديرباز موردتوجه بشر بوده است. در سال‌هاي اخير پيشرفت‌هاي فراواني در زمينه استحصال زمين‌هاي غير‌مرغوب و تقويت آن‌ها صورت پذيرفته است. امروزه تسليح خاك به‌عنوان روشي كارآمد در بهسازي لايه‌هاي خاك به‌منظور افزايش ظرفيت باربري و كاهش نشست‌هاي آن مورداستفاده قرار مي‌گيرد. سيستم كيسهخاك يكي از مصنوعات پليمري نوين است، كه مي‌تواند به‌عنوان عنصر تقويت‌كننده‌ي خاك در پروژه‌هاي مختلف عمراني استفاده شود. در راستاي افزايش ظرفيت باربري خاك و كاهش نشست‌هاي آن، سيستم كيسهخاك ابداع‌ شده است. در اين نوشتار با استفاده از روش عددي، مدل خاك بستر در شرايط مسلح و غيرمسلح (دست نخورده) بررسي‌شده است. بررسي عددي با استفاده از نرم‌افزار اجزاي محدود Abaqus در حالت سه‌بعدي انجام‌شده است. همچنين در اين نوشتار، تأثير سيستم كيسه خاك در افزايش ظرفيت باربري و كاهش نشست مورد ارزيابي قرارگرفت. تطبيق مناسبي ميان نتايج به‌دست‌آمده از بررسي‌هاي عددي و پژوهش‌هاي ميداني پژوهشگران ديگر وجود دارد. افزون بر آن نتايج نشان مي‌دهد ظرفيت باربري بستر تسليح شده با سيستم كيسه‌خاك تقريباً 2 برابر بيشتر از بستر غيرمسلح است.

Using of reinforcement elements in improving geotechnical properties of soil has been considered by a human for many years. In recent years, many improvements have been made in the field of improving poor soils and reinforcing them. Soil reinforcement is used as an effective method to improve the soil layers in order to increase the bearing capacity and reduce the settlement. Soilbag system is one of the new polymer products. That can be used as a soil reinforcing element in various projects. Soilbag system was developed in order to increase the bearing capacity of the soil and reduce its settlement. The kind of filling materials mostly depends on the application of soilbag system and availability of materials. The most important characteristic implemented into the structure of soilbag system is tension strength of the polymer implemented in the bag. Bags implemented into soilbag system are generally built of polyethylene or polypropylene polymers. When soilbag system undergoes vertical loading, tension force produced into the bag cover causes to increase vertical force (N), consequently, this causes to increase the force between soil particles (= soil friction coefficient and F=.N). Earth reinforcement using of soilbag system causes to increase bearing capacity and it causes to minimize transformation of foundation bed influenced by the imposed load. The results of simple pressure test on the foundation reinforcement with soilbag system by Yongfu Xu show that when soilbag system is exposed on external load, it exhibits high strength which a fundamental portion of this strength is resulted from tension force generated in the cover of polymeric bag. Of other characteristics of soil bags, the absorption of vibrations resulted from traffic load can be addressed. In this study, the bed soil models in reinforced and nonreinforced conditions have been investigated using numerical method. Numerical studies have been done in three dimensional cases using finite element method (Abaqus). In this method sand and polypropylene polymer bag behavior were defined by using Mohrcoulomb and Elastic Perfect Plastic models. Also, the effects of soilbag system in increasing the bearing capacity and reducing settlement were evaluated. Another resistancebased parameters of soilbag system which was examined in this research, is the effect of internal friction angle of soil on the bearing capacity of soilbag system. Regarding the results of numerical method, it is observed that the maximum tension concentration in the abovementioned model is placed in the corners of polymeric bag. The results show that the more is the friction angle between soils particles, the resistance of soilbag system will also be increased against the external loading. There are proper matching between the results obtained from numerical studies and field studies done by other researchers. The results show that the bearing capacity of reinforced bed is almost 2 times bigger than the nonreinforcement bed.