پديد آورندگان :
نصيرزاده قورچي، رضا دانشگاه تهران - دانشكدۀ مهندسي - گروه معدن , اميني، مهدي دانشگاه تهران - دانشكدۀ مهندسي - گروه معدن , معماريان، حسين دانشگاه تهران - دانشكدۀ مهندسي - گروه معدن
كليدواژه :
تحليل احتمالاتي , نرم‌افزار SLIDE , تحليل قطعي , سرريز آزاد سد كوار شيراز , مونت كارلو
چكيده فارسي :
طراحي و اجراي شيروانيها يكي از حساس‌ترين و مهم‌ترين مسائل در پروژه هاي عمراني و معدني محسوب ميشود. در علم ژئوتكنيك، به‌دليل دسترسي نداشتن به اطلاعات كافي و مطمئن پيرامون كميتهاي طراحي، ارائه يك مدل كاملاً قطعي غيرممكن است. از اين‌رو، در سالهاي اخير، براي تحليل پايداري شيروانيها بيش‌تر به‌روش احتمالاتي مراجعه شده است. در اين تحلي لها، كميتهاي تأثيرگذار در پايداري شيرواني به‌صورت توزيعهاي آماري در نظر گرفته ميشوند و در نتيجه ضريب اطمينان نيز يك توزيع آماري خواهد شد. از اين‌رو، ابتدا خلاصه‌اي از تحقيقات انجام شده روي تحليل احتمالاتي شيروانيها ارائه شده و برتري تحليل احتمالاتي نسبت به تحليل قطعي در طراحي شيروانيها بررسي ميشود. در ادامه، براي شفاف شدن توصيفهاي مذكور، شيرواني مشرف به سرريز آزاد سد كوار شيراز با روش شبيه‌سازي مونت كارلو به‌صورت احتمالاتي با استفاده از نرم‌افزار SLIDE تحليل ميشود. اين تحليلها نشان مي‌دهند ضريب اطمينان محاسبه شده به‌وسيلۀ تحليل احتمالاتي به‌صورت يك تابع توزيع ارائه ميشود كه نسبت به تحليل قطعي كه نتيجه آن صرفاً يك مقدار مشخص است، تصوير روشن‌تري از شكست ارائه مي‌كند. هم‌چنين نتايج تحليل احتمالاتي نشان مي‌دهد كه مي‌توان شيب شيرواني را بهينه كرد به‌نحوي كه كاملاً پايدار بماند و حجم عمليات سنگ‌برداري نيز بهينه شود. از اين‌رو به‌كمك تحليل احتمالاتي شيب بهينه اين شيرواني تعيين شد كه در اين حالت ميزان سنگ‌برداري حدود 28000 متر مكعب كم‌تر ميشود.
چكيده لاتين :
One of the most sensitive and important issues in some civil engineering projects is slope design and application. The process of slope design always involve many uncertainties. Hence, it is impossible to accurately comment on its stability or instability. Most of the uncertainties in the slope stability analysis are related to the nature of materials, geometry, environmental conditions, model errors, and measuring errors as well. Therefore, the slope stability analysis with a deterministic approach which uses the concept of safety factor would often not result satisfactory. Consequently, the use of probabilistic methods is more advised. Accordingly, in recent years, the probability analysis has been used to slope stability analysis. In these analyses, the effective quantities of slope stability are considered as statistical distributions, and the reliability coefficient would then be a statistical distribution. Likewise, one of the approaches to simulate uncertainties in the probabilistic analysis is to use the variation coefficient. If the variation coefficient changes, the probability of failure will change accordingly. When the variation coefficient becomes a larger number, costly solutions are required to reduce the probability of failure. If the variation coefficient becomes low, the reliability will be increased and the required costs to reduce the probability of failure will be decreased. Therefore, determining the amount of variation coefficient in these analyses is very important. Furthermore, the correlation coefficient between the quantities is another effective parameter in computing the probability of failure.
Material and methods
In this research, the stability analysis of the slope facing the spillway of the Shiraz Kavar dam has been done in two probabilistic and deterministic methods. Since circular slip probability is more likely than other types of failure, in the analysis of the stability of this slope, the problem of circular failure is very important, and an appropriate equilibrium program should be used for circular failure analysis. Therefore, SLIDE software was used to slope stability analysis. For material behavior, the Hook-Brown failure criterion was applied. In order to determine the strength parameters of the criterion, Geological Strength Index (GSI), uniaxial compressive strength (UCS) and rock constant parameter mi were used. For crushed rock with a moderate quality of crushing, the GSI quality of the rock mass was about 23 to 38, which the average value of that for the rock mass of the overflow was assumed 35. Also, the uniaxial compressive strength of the rock was evaluated about 50 to 100 MPa with an average value of 75 MPa. In addition, the value of mi was 10, and due to mechanized drilling, the disturbance factor was considered to be 1. The amount of unit weight was assumed to be 22 kN/m3. The initial model used for deterministic and probabilistic analyses, is the Morgenstern-Price model. To conduct probabilistic analyses, Monte Carlo simulation was performed using random sampling method (RS-MC) and 200,000 sampling were used to converge the simulation results. To determine the coefficient of variation and the probability distribution of UCS, GSI and mi, the proposed values of Hook (1998) were applied and for unit weight (γ) James Rodriguez and Sitar (2007) studies were used. Also, the minimum and maximum values of UCS and GSI are determined based on the results of experiments, and Third Sigma rule was utilized for mi and γ quantities. Since the earthquake phenomenon is rarely of great intensity and the number of small earthquakes is higher, therefore the truncated exponential distribution function can be in good agreement with the results of the earthquake. Usually, the maximum magnitude of the earthquake acceleration coefficient is twice that of the average.
