Engineering Geology

Engineering Geology

Effect of delay time on In Situ Stress Determination by Acoustic Emission

Abstract
The in-situ stress is one of the most important parameters in the design of underground structures. Conventional methods such as in-situ stress measurements using hydraulic fracturing method has two main disadvantages are time and cost of this methods. Acoustic emission is one of the indirect in-Situ stress measurement methods which is based on the theory of the Kaiser effect. When a rock is stressed, it release acoustic signals this phenomenon is called acoustic emission. Kaiser Effect is defined as lack of acoustic signals in the lower stress levels than the previous maximum stress level. In other words, as long as rock is not reached to the previous maximum stress level, do not show significant acoustic emission. Several factors affect on Kaiser Effect such as delay time, temperature, rock fabric, porosity, discontinuities, joints and geological structure. In this paper, effect of the delay time on Kaiser Effect has been presented. The time between coring operations and acoustic emission test is called delay time. The limestone rock is selected as main samples of test and after preloading, reloading and acoustic emission test were carried out with different delay times. The results showed that the felicity ratio is less than 1, when delay time is about 20 days and after three months has increased to be more than one.
Keywords

1. Yoshikawa S., Mogi K., "Experimental studies on the effect of stress history on acoustic emission activity-a possibility for estimation of rock stress", Journal of acoustic emission, vol. 8, No. 4 (1989) 113-123.## 2. Kurita K., Fujii N., "Stress memory of crystalline rocks in acoustic emission", Geophysical Research Letters, Volume 6, Issue 1 (January 1979) 9-12. ## 3. Momayez M., Hassani F.P., "Application of Kaiser effect to measure in-situ stresses in underground mines", Rock Mechanics, Tillerson JR and Wawersik, WR (eds), Proceeding og the 33rd US symposium on rock mechanics, Santa Fe, New Mexico, AA Balkema, Rotterdam (1992) 979-987. ## 4. Seto M., et al, "The relation between the variation of AE hypocenters and the Kaiser effect of Shirahama sandstone", Proc. 8th Int. Cong on Rock Mechanics, Vol. 1, Tokyo, Japan (1995) 201-205. ## 5. Jin Y., Z. Qi, et al., "Time-sensitivity of the Kaiser effect of acoustic emission in limestone and its application to measurements of in-situ stress", Petroleum Science 6(2) (2009) 176-180. ## 6. Li Y., Yang Y., Liu J., Zhao X., "Experimental and theoretical analysis on the procedure for estimating geo-stresses by the Kaiser effect", International Journal of Minerals, Metallurgy and Materials, Volume 17, Number 5 (October 2010) 514. ## 7. Lavrov A., "The Kaiser effect in rocks: principles and stress estimation techniques", International Journal of Rock Mechanics & Mining Sciences 40 (2003) 151-171. ## 8. Li H., Zhang B., "Laboratory determination of in-situ stress tensor using AE method", Rock Stress, Sugawara, Obara & Sato (eds), © 2003 Swets & Zeitlinger, Lisse, ISBN 90 5809 6394. ## 9. Amadei B., Stephansson O., "Rock stress and its measurement", Published by: Chapman & Hall, London (1997). ## 10. Villaescusa E., Seto M., Baird G., "Stress measurements from oriented core" Int. J. of Rock Mech. & Min. Sci. 39 (2002) 603-615. ## 11. Lehtonen A., Cosgrove J., et al. "An examination of in situ rock stress estimation using the Kaiser effect." Engineering Geology 124 (2012) 24-37. ## 12. نیکخواه مجید، بررسی آزمایشگاهی و عددی تأثیر بارگذاری سه‌محوره بر اثر کایزر، رساله دکتری، دانشکده فنی و مهندسی دانشگاه تربیت مدرس (1392). ## 13. The Working Group for estimating the primary state of stress in a rock mass using the acoustic emission technique, "Suggested method for in-situ stress measurement from a rock core using the acoustic emission technique", Proc, 5th International workshop on application of Geophysics in Rock Engineering, July 7, Toronto, Canada (2002) ## 14. آرینفر علی، مقایسه روش‌های AE و DRA دراندازه‌گیری تنش برجا و مطالعه موردی: سد سیمره، ،پایان نامۀ کارشناسی ارشد دانشکدۀ فنی و مهندسی دانشگاه تربیت مدرس (1390). ##