Abstract
The frequency, spacing and trace length of rock mass discontinuities appear to follow a negative exponential distribution. However, in some cases this distribution has limitations. To overcome this, it is necessary to choose a target distribution which is flexible enough to simulate the spacing and trace length of the discontinuities. The paper shows how the two parameter negative exponential (TPNE) distributions can meet the requirements. An improved constitutive equation of rock mass based on this new distribution has been determined from which a new method to calculate rock mass elastic modulus (Em) is proposed, taking into account the rock mass anisotropy. It was found that the geo-stresses influence Em in two ways: it varies with changes in the orientation of the geo-stress and with the size of geo-stress. The work is illustrated by a case study on the abutment slope of the 295 m high arched dam of the Xiao wan hydroelectric power station in Yunnan province, Southwest of China.
Résumé
La fréquence, l’espacement et la longueur de trace de discontinuités de masses rocheuses apparaissent suivre une distribution exponentielle négative. Cependant, dans certains cas, cette distribution ne convient pas. Afin de surmonter cette difficulté, il est nécessaire de choisir une distribution cible suffisamment souple pour représenter l’espacement et la longueur de trace de discontinuités. L’article montre comment les distributions exponentielles négatives à deux paramètres peuvent répondre au problème. Une loi de comportement améliorée de la masse rocheuse, basée sur cette nouvelle distribution, a été déterminée, à partir de laquelle une nouvelle méthode de calcul du module d’élasticité d’un massif rocheux est proposée, prenant en compte l’anisotropie du massif rocheux. Il a été montré que les contraintes géostatiques influencent le module d’élasticité de deux façons : il varie avec les changements d’orientation du champ de contrainte géostatique et avec son intensité. Ce résultat est illustré par une étude de cas concernant l’appui rocheux d’un barrage voûte de 295 m de hauteur de la centrale électrique de Xiao Wan dans la province du Yunnan, dans le sud-ouest de la Chine.
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References
Carbonell R (2004) On the nature of mantle heterogeneities and discontinuities: evidence from a very dense wide-angle shot record. Tectonophysics 388:103–117
Dershowitz WS, Einstein HH (1988) Characterizing rock joint geometry with joint system models. Rock Mech Rock Eng 21(1):21–51
Fossum AF (1985) Effective elastic properties for a random jointed rock mass. Int J Rock Min Sci 22(6):467–470
Gerrard CM (1982) Equivalent elastic moduli of a rock mass consisting of orthorhombic layers. Int J Rock Mech Min Sci 19:9–14
Goodman RE (1976) Methods of geological engineering in discontinuous rocks. West Publishing Co., St. Paul
Hudson JA, Priest SD (1983) Discontinuity frequency in rock masses. Int J Rock Min Sci Geomech Abstr 20(2):73–89
Jimenez-Rodriguez R, Sitar N (2006) Inference of discontinuity trace length distributions using statistical graphical models. Int J Rock Mech Min Sci 43:877–893
Oda M (1984) Similarity rule of crack geometry in statistically homogeneous rock masses. Mech Mater 3:119–129
Oda M (1986) An equivalent continuum model for coupled stress and fluid flow analysis in jointed rock masses. Water Resour Res 22(13):1845–1856
Priest SD (2004) Determination of discontinuity size distributions from scanline data. Rock Mech Rock Eng 37(5):347–368
Priest SD, Hudson JA (1976) Discontinuity spacings in rock. Int J Rock Min Sci 131:35–139
Priest SD, Hudson JA (1981) Estimation of discontinuity spacing and trace length using scanline surveys. Int J Rock Min Sci 18:183–197
Warburton PM (1980) A stereological interpretation of joint trace data. Int J Rock Mech Mining Sci Geomech Abstr 17:181–190
Wei ZQ, Hudson JA (1986) The influence of joints on rock modulus. In: Proceedings of the international symposium on eng complex rock formation, Science Press, Beijing, China, pp 54–62
Wines DR, Lilly PA (2002) Measurement and analysis of rock mass discontinuity spacing and frequency in part of the Fimiston Open Pit operation in Kalgoorlie, Western Australia: a case study. Int J Rock Mech Min Sci 39:589–602
Wu F, Wang S (2001) A stress–strain relation for jointed rock masses. Int J Rock Mech Min Sci 38:591–598
Wu F, Wang S, Song S, Lu J (1994) Statistical principles in mechanics of rock masses. Chin Sci Bull 39(6):493–503
Yashinaka R, Yamabe T (1986) Joint stiffness and the deformation behaviour of discontinuous rock. Int J Rock Min Sci 23(1):19–28
Zhang L, Einstein HH (1998) Estimating the mean trace length of rock discontinuities. Rock Mech Rock Eng 31(4):217–235
Zhang L, Einstein HH, Dershowitz WS (2002) Stereological relationship between trace length and size distribution of elliptical discontinuities. Geotechnique 52(6):419–433
Zhou W, Maerz NH (2002) Implementation of multivariate clustering methods for characterizing discontinuities data from scanlines and oriented boreholes. Comput Geosci 28:827–839
Acknowledgments
The authors would like to thank to Senior Engineer Zhuang Huaze, Dr. Liu Tong, Dr. Yan Changgen, Dr. Chai Jianfeng and Dr. Yang Xiaoyong; most of the field work was undertaken by them. Dr. Qi Shengwen, Dr. Tao Bo and Dr. Liu Haiyan also took part in the field investigations, and their work is appreciated. Dr. Qi Shengwen kindly read and revised the manuscript. The Work was supported by The Key Laboratory of Engineering Geomechanics, Institute of Geology and Geophysics, Chinese Academy of Sciences.
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Hu, X., Wu, F. & Sun, Q. Elastic modulus of a rock mass based on the two parameter negative-exponential (TPNE) distribution of discontinuity spacing and trace length. Bull Eng Geol Environ 70, 255–263 (2011). https://doi.org/10.1007/s10064-010-0321-z
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DOI: https://doi.org/10.1007/s10064-010-0321-z
Keywords
- Rock mass elastic modulus
- Discontinuity
- Negative exponential distribution
- Constitutive equation
- TPNE
- China