جانمایی بهینه تونل‌های غیر هم‌سطح با استفاده از یک رویکرد جدید احتمالاتی

یکی از مباحث مهم در طراحی تونل‌های غیر هم‌سطح، تعیین جانمایی بهینه تونل‌ها نسبت به هم هست. این موضوع در مناطق متراکم شهری که اغلب به‌صورت تونل‌های غیرمسلح انجام می‌شود، اهمیت بیشتری پیدا می‌کند. در این تحقیق به‌منظور جانمایی بهینه از دو عامل نشست سطح زمین و پایداری (ضریب ایمنی) تونل‌ها استفاده شده است. جانمایی بهینه تونل‌های غیر هم‌سطح در شرایط متنوع زمین‌شناسی بایستی از روش‌های احتمالاتی و قابلیت اعتماد استفاده کرد. از طرفی آگاهی از میزان تاثیر هر یک از پارامترهای طراحی در مقدار نشست سطح زمین و ضریب ایمنی می‌تواند منجر به کاهش صدمات سازه‌های سطحی شود. در این مقاله از نرم‌افزار المان محدود plaxis3d جهت مطالعه حالت‌های مختلف تونل‌های غیر هم‌سطح استفاده شده است. سپس به کمک الگوریتم جستجوی هارمونی دو تابع حالت حدی به‌صورت جدا برای ضریب ایمنی و حداکثر نشست سطح زمین تخمین زده شده است. در ادامه با استفاده از دو تابع حالت حدی به‌دست‌آمده از مرحله‌ی قبل و روش‌های قابلیت اعتماد مرتبه اول و شبیه‌سازی مونت‌کارلو در نرم‌افزار rt بهترین جانمایی برای حفر تونل جدید نسبت به تونل قبلی (موجود) بر مبنای داشتن بیشترین ضریب ایمنی و کمترین نشست سطح زمین پیشنهاد شده است. نتایج نشان می‌دهد که احتمال شکست تونل اول (موجود) تقریباً 0/3 درصد بوده و ازنظر پایداری و عکس‌العمل نسبت به موقعیت بهینه تونل جدید شرایط ایده‌آلی خواهد داشت.

Optimal location of nonlevel tunnels using a new probabilistic approach

SummaryOne of the important issues in designing nonlevel tunnels is determining the optimal location of tunnels relative to each other. In this research, to optimally locate the two factors of land subsidence and stability (safety factor) of tunnels have been used. Optimal placement of nonlevel tunnels in various geological conditions should use probabilistic methods and reliability. In this paper, PLAXIS3D finite element software is used to study different states of nonlevel tunnels. Then, using the harmony search algorithm, two limit state functions are estimated separately for the safety factor and maximum ground surface subsidence. Then, using the two limit state functions obtained from the previous step and the firstorder reliability methods and the Monte Carlo simulation in RT software, the best location for excavation of the second tunnel in relation to the previous (existing) tunnel is based on having the highest safety factor and lowest ground subsidence. Introduction Due to the complexity of the interaction between the tunnels and also due to the uncertainty in the design parameters, in this paper, using probabilistic analyzes such as the Monte Carlo simulation method and firstorder reliability, the optimal stability and placement of nonlevel tunnels in RT probabilistic software was discussed. Because RT software requires a correct and accurate limit state function, the harmonic search algorithm in MATLAB was used to calculate the stability and also to achieve this limit state function. Methodology and ApproachesIn this paper, using PLAXIS3D software, the tunnel was modeled in 32 different rock masses and the results are different in each of the 32 rock masses due to the inequality in the input parameters (safety factor and maximum settlement). To evaluate the reliability of the new tunnel excavation (existing subtunnel), 32 models which were analyzed by PLAXIS3D software were compared with the predicted model to achieve the lowest settlement rate and the highest safety factor by the harmony search algorithm. The comparison showed good consistency between the model predicted by the harmony search algorithm and the model performed by numerical methods. Therefore, due to the proximity of the performed model and the predicted model, the limit state function is accurate to obtain the probability of failure of the new tunnel. Results and ConclusionsAccording to the results obtained in both Monte Carlo simulation methods and firstorder reliability, the probability of failure (approximately 0.33%) and the highreliability index are shown and the tunnel position is in very good condition. According to the analysis of tunnel random variables by RT software, it was found that the geological durability index is very important and effective. It should be noted that the results of this study show that the reliability methods used in the RT program to stabilize and locate the new tunnel under the existing tunnel can be used as a highperformance method in analyzing underground space problems.