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دانلود رایکان مقاله انگلیسی ISI با موضوع تاثیر تنش اصلی میانگین بر شکست سنگ و مقاومت سنگ در نزدیکی مرز حفاری

عنوان فارسی مقاله:

تاثیر تنش اصلی میانگین بر شکست سنگ و مقاومت سنگ در نزدیکی مرز حفاری (از نظر مدل سازی عددی)

عنوان انگلیسی مقاله:

Influence of intermediate principal stress on rock fracturing and strength near excavation boundaries—Insight from numerical modeling

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3. Conclusions

The influence of the intermediate principal stress on rock fracturing and strength is studied using a FEM/DEM combined numerical tool. At the boundary in an underground setting, the intermediate principal stress is often parallel to the tunnel axis, the minimum stress is zero, and the maximum principal stress is the tangential stress. A loading condition of s3 ¼ 0, s16¼0, and s26¼0 thus exists at the boundary. It is seen from the simulation that the generation of tunnel surface parallel fractures (onion skins, spalling and slabbing) is attributed to the existence of moderate intermediate principal stress and low to zero minimum confinement. Material heterogeneity also plays a major role as local tensile stresses need to be generated for crack initiation and propagation. The intermediate principal stress confines the rock in such a way that fractures can only be developed in the direction parallel to s1 and s2. This fracturing process changes the rock behavior from the original isotropic state to an anisotropic one. Hence, consideration of the effect of the intermediate principal stress on rock behavior should focus on the stress-induced anisotropic strength and deformation behavior of the rocks. Under s3 ¼ 0 condition, it is found that the intermediate principal stress has limited influence on the peak strength of the rock. The large percentage increase of rock strength due to s2, as observed from the laboratory tests, is mainly attributed to the end effect of the testing system. Further experimental and numerical study is needed to study the impact of s2 on peak strength. In the next phase of the research, it is planed to model the loading platens in ELFEN to quantify the end effect on rock strength.