نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه مهندسی معدن، واحد علوم و تحقیقات، دانشگاه آزاد اسلامی، تهران، ایران
2 دانشکده مهندسی معدن، نفت و ژئوفیزیک، دانشگاه صنعتی شاهرود، شاهرود، ایران
3 دانشکده فنی و مهندسی، دانشگاه تربیت مدرس، تهران، ایران
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Summary
One of the geomechanical parameters that is very important in the design and analysis of various rock engineering projects is the in situ stress state of the rock mass. In this research, acoustic emission signal processing has been used to determine the Kaiser effect point of the experimental data on Phyllite rock by discrete wavelet transform method.
Introduction
There are different methods to determine in situ stress. In this regard, direct measurement methods are the best and most accurate in situ stress measurement methods. However, these methods are very time-consuming and costly. Therefore, nowadays laboratory and indirect rock core-based methods for estimating in situ stress have been taken into consideration. One of the laboratory methods is the acoustic emission method based on Kaiser effect. In this method, determining the Kaiser effect point is usually done by the parameters of acoustic emission signals, which in some cases, determining the Kaiser effect point by parametric method are ambiguous and do not have sufficient clarity. Signal processing based on wavelet transform is a powerful tool to process acoustic emission signals, which has been used in several papers.
Methodology and Approaches
In this study some Phyllite samples were used to be loaded under indirect tensile loading (Brazilian test). The acoustic emission test consisted of two cycles. In the first cycle, the samples were preloaded to a predetermined level, and in the second cycle, they were reloaded until reaching the failure. Before using the discrete wavelet transform, the appropriate mother wavelet was selected. Then, the signals obtained from the acoustic emission test were processed using wavelet transform. The maximum approximation coefficient parameter was used as a suitable feature for the analysis. Using K-means method, the obtained data are clustered in five clusters. Then, the highest density of data in the fifth cluster was considered as the occurrence point of the Kaiser effect.
Results and Conclusions
The results show that according to the parameters of correlation coefficient and noise to signal ratio and the type of acoustic signals the mother wave db6 was suitable for analysis. Among the parameters that can be used for analysis, the maximum approximation coefficient parameter is also selected as a suitable feature for analysis. Also, the results of the discrete wavelet transform method were in good agreement with the results of the parametric method, so that the occurrence times of the Kaiser effect obtained from the two methods are mutually acceptable.
کلیدواژه‌ها [English]
به‌طورکلی سنگ‌ها و اغلب مواد زمانی که تحت تنش قرار می‌گیرند از خود صدا و سیگنال‌های لرزه‌ای با فرکانس زیاد ساطع می‌کنند. این پدیده انتشار آکوستیک نام دارد. در سال‌های اخیر به‌کارگیری روش انتشار اکوستیک که جزء آزمایش‌های غیر مخرب به‌حساب می‌آید رو به فزونی گذاشته است و این روش به‌طورکلی کاربرد زیادی درزمینه‌ی مهندسی معدن، عمران، علم مواد، زلزله‌شناسی و معدن یافته است. آزمایش انتشار اکوستیک یک روش با حساسیت زیاد برای دریافت این امواج در یک ماده بوده که از آن در زمینه‌های رفتار نگاری در مصالح جامد نظیر سنگ، فلز، شیشه و سرامیک که تحت تنش قرار دارند و نیز بررسی فرآیند شکست در این مواد استفاده می‌شود.
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