مدل سازي گسيختگي پيش رونده در شيرواني هاي خاكي با استفاده از روش درون يابي نقطه اي با توابع شعاعي تصادفي

در تحليل­هاي مرسوم گسيختگي شيب­هاي خاكي، پارامترهاي مقاومتي حتي در كرنش­هاي بزرگ بدون تغيير و به صورت قطعي فرض مي­شوند. اين در حالي است كه در حين گسيختگي، مقاومت خاك مقادير بيشينه و پسماند از خود نشان داده و استحكام آن به صورت پيش­رونده با افزايش كرنش خميري كاهش مي‌يابد. علاوه بر تغييرات پارامترهاي مقاومتي خاك طي مكانيزم پيش­رونده، ماهيت غيريكنواخت خاك نيز سبب ايجاد تغييرات مكاني اين پارامترها مي­شود. از اين رو سيستم­هاي ژئوتكنيكي بايستي با لحاظ عدم قطعيت مقادير پارامترهاي خاك به صورت غيرقطعي و با استفاده از مفاهيم آمار و احتمالات بررسي‌ شوند. شبيه­سازي گسيختگي پيش­رونده[1] به صورت قطعي يا غيرقطعي تنها با بكارگيري تكنيك‌هاي عددي نظير روش اجزاء محدود كه قادر به شبيه­سازي توسعه كرنش خميري انحرافي[2] هستند، ممكن مي­شود. اگر چه روش اجزاء محدود به طور گسترده در تحليل مسائل پايداري مورد استفاده قرار مي­گيرد، با اين حال اين روش با مشكلاتي كه اساساٌ به شبكه­بندي مربوط مي­شود، رويرو است. در اين تحقيق از روش درون­يابي نقطه­اي با توابع شعاعي در تركيب با ميدان تصادفي جهت مدل­سازي تغييرات مكاني خصوصيات مقاومتي خاك و تحليل ناپايداري شيب استفاده شده است. به منظور در نظر گرفتن گسيختگي پيش­رونده خاك، روش حل الاستوپلاستيك با مدل رفتاري مور كولمب توسعه داده شده جهت لحاظ قابليت نرم­شوندگي كرنش بكارگرفته شده است. براي انجام تحليل احتمالاتي نيز ميدان تصادفي پارامترهاي چسبندگي و زاويه اصطكاك و همچنين كرنش خميري حد آستانه بر اساس مقادير ميانگين و انحراف معيار آنها توليد مي­شوند. به منظور بررسي كاربرد روش درون­يابي نقطه­اي با توابع شعاعي تصادفي، يك شيرواني خاكي با هندسه مشخص به صورت قطعي و غيرقطعي مورد تحليل قرار گرفته و ضريب اطمينان مربوط به آن بررسي شده است. براساس تحليل بواسطه مدل­سازي گسيختگي پيش­رونده، نتيجه مي­شود كه گسيختگي واقعي خاك و وقوع جابجايي­هاي ادامه­دار به طور همزمان با شكل­گيري مكانيزم پيش­رونده زوال خاك و رسيدن مسير لغزش به سطح زمين به وقوع مي­پيوندند. در ادامه با انجام تحليل احتمالاتي و توليد ميدان­هاي تصادفي، توابع توزيع احتمالاتي ضريب اطمينان تعيين شده و پس از آن پارامترهاي آماري محاسبه شده­ اند.

Sustainability studies, from the point of view of regional identification with the potential of failure in the soil, and from the point of view of designing the new engineering structures, are considered as important issues in geotechnical engineering and have always been a significant part of the references in this field. Subject is dedicated. In the meantime, instability analysis in classical geotechnical problems such as the back of the retaining wall, bearing capacity of foundation and slopes and landslides with a progressive failure mechanism, is considered as a challenging topic in this discussion. These issues are in the category of issues with large displacements and have always attracted the attention of many scholars in recent years. With advances in computer technology and computational techniques, numerical methods such as finite difference, finite element, and boundary components have been widely employed in analyzing engineering issues. In the meantime, the finite element method, due to the ability of that method to control issues with geometry and complex conditions and modeling the behavior of soil shape change, has increased significantly compared to other numerical methods. In conventional analyzes of soil slopes failure, resistance parameters are assumed to be stable even in large strains without change. However, during the rupture, soil resistance exhibits maximum and residual amounts, and its strength increases prematurely by increasing the plastic strain. In addition to changing soil resistance parameters in the progressive mechanism, the non-uniform nature of the soil also causes spatial variations of these parameters. Therefore, geotechnical systems should be considered in terms of the uncertainty of soil parameters values uncertainly using the concepts of statistics and probabilities. The simulation of a progressive failure is definite or non-deterministic only by applying numerical techniques such as finite element method that are able to simulate the development of deviant plastic strain. Although the finite element method is widely used in the analysis of sustainability issues, however, this approach is based on problems that are essentially related to gridding. In this research, a radial point interpolation method in combination with a random field was used to model the spatial variations of soil resistance properties and slope instability analysis. In order to consider the progressive failure of soil, elastoplastic method has been developed with the Coulomb Moore's behavioral model for applying strain softness. For probabilistic analysis, the random field is also used to determine the cohesion parameters and the friction angle as well as the plastic strain threshold based on their mean values and standard deviation. In order to investigate the application of the point interpolation method with randomized radial functions, a geotechnical earthwork with definite and non-deterministic geometry has been analyzed and its reliability coefficients has been investigated. Based on the analysis of the progressive failure modeling, it is concluded that the actual failure of the soil and the occurrence of continuous displacements occur simultaneously with the formation of a progressive mechanism of soil degradation and the arrival of the slipping path to the ground. In the following, probabilistic distribution functions of the coefficient of reliability were determined by probabilistic analysis and the production of random fields, and then the statistical parameters are calculated.