ارزيابي تاثير شكل سطح تسليم در تحليل‌هاي استاتيكي و ديناميكي سازه‌هاي ژيوتكنيكي

Evaluation of the Effect of Yield Surface Shape on Static and Dynamic Analyses of Geotechnical Structures

در اين پژوهش، دو مدل رفتاري MCH و DPH معرفي شده اند، كه ساختاري كاملاً مشابه دارند و تفاوت آنها فقط در معيار تسليمي است كه براي آنها در نظر گرفته شده است. اين دو مدل رفتاري در حقيقت از تلفيق مدل هذلولي، به ترتيب با سطوح تسليم موهر– كولمب و دراكر– پراگر پديد آمده اند. پس از كاليبره‌كردن اين مدل هاي رفتاري با داده هاي آزمايشگاهي در يك مسير تنش خاص، نحوه ي عملكرد آنها در مسيرهاي ديگر تنش با توجه به داده هاي آزمايشگاهي مورد ارزيابي قرار گرفته است. سپس به كمك زبان برنامه‌نويسي Fish، اين دو مدل رفتاري به نرم‌افزار FLAC معرفي شده‌اند، تا زمينه‌ي مناسب براي انواع تحليل هاي عددي فراهم آيد. به اين ترتيب نحوه ي عملكرد اين مدل هاي رفتاري و در نتيجه تاثير سطوح تسليم در تحليل هاي عددي استاتيكي و ديناميكي مربوط به مسايل مختلف ژيوتكنيك (مثل ظرفيت باربري پي، تونل، و گودبرداري) مورد ارزيابي قرار گرفته است. در يك نگاه كلي، پيش بيني مدل هاي رفتاري به‌كاررفته در اين پژوهش، با توجه به مسير تنش كاليبراسيون (يعني آزمايش سهمحوري متداول)، در بارگذاري پي كمترين انطباق و در مسيله‌ي گود بيشترين انطباق را نشان داده‌اند.

In geotechnical engineering, yield surface (criterion) is a subject that has attracted the attention of a large number of researchers in both fields of experimental and constitutive modeling. Various yield surfaces have been introduced by different investigators, of which, Mohr-Coulomb and Drager-Prager criteria are the most famous. Generally, yield criteria are used in constitutive model structures. On the other hand, the final aim is to apply these constitutive models in numerical analyses of geotechnical engineering problems. Therefore, the question which arises here is; how high is the degree of effect of these yielding surfaces on numerical analyses of geotechnical problems, and also, is a more accurate yielding criterion needed or not? In this paper, two constitutive models of MCH and DPH have been introduced in such a way that they have quite similar structures and the only distinction between them is their supposed yield surfaces. In fact, these models have been originated by a combination of the hyperbola model with Mohr-Coulomb and Drager-Prager criteria, respectively. After calibration of the two constitutive models by experimental data on a specific stress path, their performance on other stress paths were also evaluated using laboratory data. Then, using Fish programming language, the two constitutive models were introduced into the FLAC program to enable investigation of various numerical analyses. In this way, performances of these constitutive models and, consequently, the effect of the yield surfaces on the static and dynamic analyses of geotechnical structures (such as foundation bearing capacity, tunnel and excavation), were evaluated. Therefore, a better insight into the degree of effect of various yield surface shapes on numerical analyses of different geotechnical problems could be obtained for engineers who use different constitutive models for design and numerical investigation, and also for researchers who study constitutive models.