تاثير كميت هاي برشي بين خاك و بلوك ها‌ بر پايداري شيرواني‌هاي مخلوط سنگي

The Influence of Shear Parameters of Matrix-Blocks Interface on Bimslope Stability

محيط برخي از شيرواني ­ها از مجموعه ­اي از بلوك ­هاي سنگي كه در ميان خاك قرار گرفته ­اند تشكيل شده است كه به آن­ها شيرواني ­هاي مخلوط سنگي اطلاق مي­ گردد. در اين شيرواني­ ها، بخشي از سطح لغزش احتمالي در محيط خاكي قرار مي­ گيرد و بخش ديگر آن از محل تماس بين بلوك ­هاي سنگي و خاك عبور مي­ كند. بنابراين كميت­ هاي برشي بين بلوك­ هاي سنگي و خاك روي پايداري شيرواني­ هاي مذكور تاثير به سزايي دارند. تا كنون اين موضوع به صورت كمي توسط محققين مورد بررسي قرار نگرفته است. در اين مقاله با تحليل حساسيت، تاثير ضريب چسبندگي و زاويه اصطكاك سطح تماس بين خاك و بلوك‌هاي سنگي بر روي پايداري شيرواني مخلوط سنگي بررسي مي‌گردد. به اين منظور از روش عددي المان محدود و ساخت 146 مدل تئوري استفاده شده است. نتايج اين پژوهش نشان مي‌دهد، در كل، حساسيت شيرواني به زاويه اصطكاك بين خاك و بلوك بيشتر از ضريب چسبندگي بين اين واحدها است. همچنين تغيير در كميت­ هاي فوق مي­ تواند تا 50 درصد فاكتور ايمني شيرواني مخلوط سنگي را تغيير دهد. بنابراين براي تحليل پايداري شيرواني ­هاي مذكور، كميت­هاي مذكور بايد حتماً به طور خاص مورد توجه قرار گيرد.

Many geotechnical projects are faced with mixture masses of rock and soil (matrix). The behavior identification of these complex masses which called “bimrocks” (block-in-matrix rocks) is very considerable. The bimrocks are defined as mixtures of rocks composed of geotechnically significant blocks within a bonded matrix of finer texture such as melanges, fault rocks and weathered rocks. In terms of interface type of between matrix and blocks, the bimrocks are divided into two categories: welded and unwelded bimrocks. Unwelded bimrocks refers to an environment that the strength of interface between matrix and blocks is less than the matrix strength. Bimslopes are made from bimrocks and usually are seen in weathered and shallow environments. In this paper, by doing sensitivity analysis, the influence of cohesion and friction angle of interface between blocks and matrix on stability of bimslopes are investigated. For this purpose, the Finite Element Method (FEM) and making of 146 theoretical models are utilized. The obtained results show that the strength parameters of interface have a significant impact on the stability bimslopes, so that regardless of cohesion and friction of interface reduce the safety factor about 50 percent rather than the identical welded bimslope. Introduction The process of slope stability analysis is one of the most important stages in design of some civil and mining projects. Bimslopes are made from bimrocks. The bimrocks usually have a specific block size. One of the most important factors affecting strength of bimrocks is VBP (Volumetric Block Proportion). For a bimrock mass, the VBP is defined as ratio of blocks volume to the total volume of mass. Previous studies show that the strength properties of interface between matrix and blocks have an important role on the stability of bimslopes. In this paper, The influence of cohesion and friction of this interface are surveyed. Methodology and Approaches The FEM by Phase2 8.0 is used to study on the strength parameters of interface between matrix and blocks. In numerical models, the values of cohesion and friction angle are changed in a bimslope with specified blocks arrangement. Also, the influence of blocks arrangement on the obtained results is investigated. Results and Conclusions The results show that the strength parameters of interface have a significant influence on stability of bimslopes and should be considered in the stability analysis. The minimum normalized safety factor of bimslopes has a logarithmic relation with strength ratio of interface. The obtained results are approximately independent of blocks arrangement.