كليدواژه :
ژئوسنتتيك , ژئوفوم (EPS) , خاك منبسط شونده , كاهش فشار تورمي
چكيده فارسي :
خاك هاي با پتانسيل تورمي جزو خاك هاي مسئله داري هستند كه در اثر جذب آب تغيير حجم داده و قابليت ايجاد فشار زيادي را به محيط اطراف خود دارند و از اين رو مي توانند بيشترين آسيب را به ابنيه و تاسيسات مجاور خود وارد سازند. از جمله آسيب هاي قابل مشاهده و با تكرار فراوان در مجاورت خاك هاي منبسط شونده مي توان به تورم كف در سازه هاي سبك، انحراف ديوارهاي نگهبان و تغيير شكل و يا شكستن لوله هاي مدفون اشاره كرد. در اين مقاله نتايج تحقيقات آزمايشگاهي جهت كاهش فشار تورمي وارد به لوله هاي مدفون وآسيب هاي ناشي از آن در محيط خاك منبسط شونده با استفاده از لايه محافظ ژئوفوم (EPS) ارائه شده است. در اين پژوهش چهار سري آزمايش بر روي يك نمونه لوله انعطاف پذير مدفون شده در خاك منبسط شونده از نوع بنتونيت انجام شد. در آزمايش اول لوله به تنهايي در خاك مدفون بوده و در آزمايش هاي دوم، سوم و چهارم به ترتيب لوله از طريق ژئوفوم به ضخامت هاي 4 و 20 و 40 ميلي متر مورد محافظت قرار گرفت. آزمايش هاي انجام شده نشان مي دهد كه استفاده از لايه محافظ ژئوفوم مي تواند تا حدود 90 درصد فشار تورمي وارد بر لوله و در نتيجه تغيير شكل آن را كاهش دهد.
چكيده لاتين :
Engineering problem related to Expansive soils is their changes in volume by moisture. This soil tends to expand by absorbing water, so if they are not allow to expand and constrained pressure swelling pressure will create. Swelling pressure can cause settlement and damage to structures which are supported by this soil. There are different solutions for overcoming on this problem but utilizing of Geofoams (EPS) is one of the most innovative approaches. In this paper, the results of tests were conducted on buried flexible pipe which supported by geofoam in the expansive soil are presented.
In these experiments, two boxes have been used in such a way that a smaller box is placed inside a larger box and space between two box was filled by water. Flexible pipe and geofoam (EPS) were located in the center of small box and then expansive soils were poured around the geofoam (EPS) and flexible pipe. The expansive soil which was used in this research was sodium bentonite. Sodium bentonite expands when wet, absorbing as much as several times its dry mass in water. Because of its excellent colloidal properties, it is often used in drilling mud for oil and gas wells and boreholes for geotechnical and environmental investigations. The property of swelling also makes sodium bentonite useful as a sealant, since it provides a self-sealing, low permeability barrier. It is used to line the base of landfills, for example
To investigating the influence of geofoam (EPS) in reduction of the swelling pressure and displacement was purpose of this experimental study. Four tests were done on flexible pipe, in the first test, flexible pipe was buried in expansive soil alone and in other tests geofoam (EPS) was used.Geofoams which used for protection of buried pipe, have 4 mm, 20 mm and 40 mm thickness respectively. each test was conducted in 32 days, because after 32 days the dial gage did not show any changes.
By comparison on the values of obtained swelling pressure and displacement, it became clear that using a geofoam (EPS) with thickness of 4mm and 20mm can decrease swelling pressure and displacement up to 50 and 80 percent, respectively. Also value of swelling pressure and displacement reduction for test with 40 mm thickness geofoam (EPS) was negligible. So it was found that increasing in geofoam (EPS) thickness can partially reduce swelling pressure and displacement of expansive soil, however, there is no direct correlation with increaseing the geofoams thickness
