بررسي نشست پي سطحي مستقر بر ماسه مسلح به تراشه لاستيكهاي فرسوده با استفاده از تحليل هاي شبه استاتيكي

Pseudo Static Analysis of Shallow Foundationʹʹs Settlement Located on Reinforced Sand by Waste Tire Chips

وجود مقادير بسيار زياد لاستيكهاي فرسوده و لزوم دفع بهداشتي و يا بازيافت آنها از مسايل جدي زيست محيطي است. از سوي ديگر با مخلوط كردن اين مصالح و خاك مي توان به خاك مسلح دست يافت و از خاصيت افزايش مقاومت برشي خاك استفاده نمود. در اين مطالعه پي نواري مستقر بر روي ماسه كه با خرده لاستيكهاي فرسوده مخلوط شده است مورد بررسي قرار گرفته است. جهت مسلح سازي، از 3 درصد متفاوت 15، 30 و 50 درصد لاستيك استفاده شده و خاك زير پي، با ضخامتهاي مختلف از مخلوط ماسه و خرده لاستيك مسلح، مدل گرديده و تحليل هاي شبه استاتيكي انجام شده است. در تحليل هاي صورت گرفته توسط نرم افزار دو بعدي PLAXIS ، مدل تحت شتابهاي افقي زلزله مختلف قرار گرفته و تاثيرات مسلح سازي بر روي نشست مورد بررسي قرار گرفته است. مطابق تحليل هاي صورت گرفته و نتايج به دست آمده مي توان بيان داشت كه استفاده از لاستيكهاي فرسوده در زير پي ها به دليل خاصيت ميرايي لاستيك، به ميزان زيادي منجر به كاهش نشست زير پي شده است.

Reusing or hygienic burial of huge amount of waste tires released in the nature is a big environ-mental problem. In some cases, soils should be improved for the use in geotechnical projects. To overcome the environmental problems and also, reusing of these waste materials, researchers are studying about civil engineering aspects of usage of waste tires. These factors may come together, leading to finding appropriate applications of waste tires. Waste tires can be used as a whole tire, chips and also shreds. A number of investigations have been carried out on shredded and chips waste tires reinforcing sands. These are, to the date, limited to those carried out on the randomly distributed of shreds in sand-shred mixtures. Using soil-tire mixture as a reinforced soil increases the soil shear strength parameters in geotechnical branch of civil engineering aspect. Results of large scale direct shear tests show that with increasing normal stress, shred contents, and degree of compaction of shred-sand mixtures, the friction angle of sand-shredded mixtures increases. Also results show that the aspect ratio of shredded tires has an important effect on shear strength parameters of reinforced sand. It is shown that for a given width of shredded tires, there exists only a sole optimum aspect ratio, which gives the absolute maximum friction angle of the mixture, regardless of shred contents and compaction degree. In this research, strip shallow foundations located on a reinforced soil by tire is modeled. Using three different contents of tire in the reinforced sand; 15%, 30% and 50%, different depth of reinforced soil (sand-tire chips mixture) beneath the foundation is pseudo statically analyzed. The analyses are based on 2D PLAXIS software and foundation settlement excited by different horizontal pseudo static accelerations are studied. Using sand-tire shreds shear strength parameters based on laboratory large scale direct shear tests in numerical 2 dimensional models, the settlement of reinforced soil is studied in static and pseudo static analyses. The results are compared with the results based on unreinforced sand. Two different degrees of compaction sand-tire chips are numerically studied, loose and compacted mixture degree of compaction. The results show that the benefits of using these sand-tire shreds mixtures, in loose compaction are more important and economical. Although the effects of compaction degree are important, it seems that tire shred contents as well as the width and depth of using sand-tire mixture, are also important and should be understood. Therefore, in this research, these different parameters are numerically studied in both static and pseudo static analyses. The obtained results show that using soil-tire shred mixture beneath the strip foundation reduces the settlement and also pseudo statically forces effects to the foundation. It can be understood that using the waste tires can reinforce the sand, increase the shear strength parameters and also reduce the settlement beneath the strip foundations.