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Owning to its special geological origin, columnar jointed rock mass is a special kind of geological structure with strong discontinuity and anisotropic. In this paper, influence of structural effect on the equivalent modulus of columnar jointed rock mass is discussed via Jointed Finite Element technique for the Baihetan project. It is noted in this paper that on the transverse plane, more the irregularity of the column is, the higher the equivalent modulus is. And this trend also aggresses with the increase of the column size. Columnar joints rock mass can be regarded as isotropic in the transverse plane. As the joint stiffness linearly increase, the equivalent modulus corresponding basically with the linear increasing. As for the longitudinal plane, more the spacing of the joint set II, the higher the equivalent modulus is. The equivalent modulus reaches its maximum value when the stagger ratio is 50%. Like on the transverse plane, as the joint stiffness linearly increase, the equivalent modulus linearly increase, correspondingly. The results of this paper agree well the existing field observations and 3-d numerical studies. The findings and conclusions of this paper may provide a reference for future studies. Introduction Abundant hydropower resources are available in southwest China, where a number of large-scale hydropower plants are currently either under construction or at design stage. Most of those plants are located in rock masses, falling or sliding of rock mass blocks or wedges defined by intersecting structural discontinuities is the most common type of failure, known as the structure effect of the jointed rock mass [1, 2]. Hence, the influences of the structure effect on the stability of these underground works would be a major geotechnical issue to be addressed during design and construction of these giant hydropower plants. As a distinctive type of rock mass structure, columnar jointed rock mass are characterized by strong discontinuity and anisotropy [3]. The relationship of the structural characteristics of the columnar joints and the macro equivalent deformation modulus of rock mass are the one of the most interest area in the research of the columnar jointed rock mass. The Baihetan hydropower plant is located on the Jinsha River in southwest China. It is one of the key elements of China's West-East Electricity Transmission Project and has been classified as a class I project, the most vital rank according to the Chinese code. The project involved the excavation of two large cavern complexes in both the left and right banks. The plant is mainly located in a rock mass of the Upper Emei Mountain Group of Permian age. The rock mass possesses an orientation of 120~145°/15~20° (dip direction/dip angle) and mainly consists of , , and stratum, where the existence of large amount of columnar jointed rock mass are detected. Those columnar jointed rock mass are vital to the engineering rock mass classification work, and eventually become a major geological problem of the plant[4]. The columnar jointed rock mass of Baihetan hydropower plants are taken as the research object in this paper. Influence of structural effect on the equivalent modulus of columnar jointed rock mass is to be discussed via Jointed Finite Element technique. The characterization parameters of the 3rd International Conference on Machinery, Materials and Information Technology Applications (ICMMITA 2015) © 2015. The authors Published by Atlantis Press 1599 structural e deformatio obtained th Principles The mai columnar j columnar j the develop into three c (1) Typ approxima Length of t Fig. 1(b). A column is a Set up t columnar j concept mo and the lon simulation respectivel Tradition the discret common c strain with affecting th made it po high accura with joint simulated b And, to ma of 10m×10 ffects are f n modulus at may serv n feature o oints are la oints is not ment char ategories[5 e I: The de tely 2~3 m he rock col nd (3) Ty pproximat Fig. 1 C he 2d num ointed rock del, as show gitudinal a , the rock y in Fig. 3 ally for roc e element ommercial merely o e reliability ssible to co cy for stres network sy y contact e ke sure tha m was adop irstly discu of the co e as techno f columnar yer-like de even, the si acteristics o ]. nsity of c , and 13~2 umn would pe III: the r ely 1.5~5 m lassificatio erical mod mass by n in Fig. 2 xis of the r mass are and 4. k mass mo method is numerical s ne Gauss i of research nsider such s calculatio stems. In J lement. In t t enough jo ted for the ssed. Then lumnar joi logical refe jointed rock veloped in ze and leng f columnar olumnar jo 5 for the e be 0.5~2.0 ock colum , and 0.5~2

Study on structural effect of equivalent elastic modulus of columnar jointed rock mass