مطالعه ي آزمايشگاهي و عددي اثر مهار برگشتي در ظرفيت باربري پي منفرد روي خاك مسلح

Laboratory and numerical simulation of the effect of wraparound anchorage of reinforcements on the bearing capacity of spread footing

در پژوهش حاضر، اثر ايجاد مهار برگشتي در انتهاي مسلح‌كننده‌ها در افزايش ظرفيت باربري پي منفرد واقع بر ماسه‌ي مسلح شده با الياف پليمري بررسي شده است. ماسه‌ي بستر پي درون يك جعبه‌ي فولادي به ابعاد 100×100×70 سانتي‌متر و پي نيز با استفاده از يك صفحه‌ي فولادي به ابعاد 20×20×5/2 سانتي‌متر شبيه‌سازي شده است. براي مدل‌سازي مكانيسم اثر مهار برگشتي در ظرفيت باربري پي، از نرم‌افزار D3F‌L‌A‌C استفاده شده است. نتايج نشان مي‌دهد در صورتي كه طول برگشت مهار به اندازه‌ي كافي بزرگ باشد و انتهاي مهار در زير پي قرار گيرد، ظرفيت باربري پي مسلح شده با مهار برگشتي افزايش در مقايسه با حالتي كه مسلح‌كننده‌هاي بدون مهار با طول برابر استفاده شده است، حدود 27٪ خواهد داشت. ايجاد مهار برگشتي باعث افزايش محصورشدگي در خاك زير پي مي‌شود

In this research, the effects of the wraparound anchorage on the bearing capacity of a spread footing on sand reinforced by carbon fiber reinforced polymer strips were studied experimentally and numerically. A steel box with the dimensions of 100×100×70 cm was used as a test setup and the spread footing was simulated using a steel plate with the dimensions of 20×20×2.5 cm. Also, a numerical model was developed by FLAC3D software to simulate the physical model for further investigations. Laboratory tests were conducted on unreinforced and reinforced models with and without wraparound anchors with different lengths. The results of these investigations indicated that the effect of the wraparound anchorage on the bearing capacity of the foundation was highly dependent on the return length of the anchor. Its effect on the improvement of the bearing capacity of the foundation was noticeable when the length of the anchor was long enough that the end of the reinforcement placed under the footing. Otherwise, the effect of the wraparound anchor on the improvement of the bearing capacity of the footing was negligible. Depending on the length of the return anchor, two distinct load-settlement behaviors were observed. When the length of the return anchor was not long enough, the bearing capacity of the footing showed some improvement in low settlement levels, but it approached the bearing capacity of the footing with unanchored reinforcements as the settlement was increasing. There was at least 10% improvement in the bearing capacity in this situation. For models with long return anchors, increasing the settlement of the footing increased the bearing capacity of the footing when compared to the behavior of reinforced model without wraparound anchor. The improvement of the bearing capacity of the footing was up to 27% for long anchors depending on the length of the wraparound anchor. The results of the numerical simulations indicated that the wraparound anchorage changed the stress distribution and increased the confinement of the soil elements located under the footing. Increasing the length of the return anchors led to a uniform distribution of the confining pressure under the footing.