AAAnnnaaalllyyytttiiicccaaalll aaannnddd NNNuuummmeeerrriiicccaaalll AAAnnnaaalllyyyssseeesss fffooorrr RRRoooccckkk SSSlllooopppeee SSStttaaabbbiiillliiitttyyy UUUsssiiinnnggg ttthhheee GGGeeennneeerrraaallliiizzzeeeddd HHHoooeeekkk- Brown Criterion Jiayi Shen AAA ttthhheeesssiiisss sssuuubbbmmmiiitttttteeeddd fffooorrr ttthhheee dddeeegggrrreeeeee ooofff Doctor of Philosophy SSSccchhhoooooolll ooofff CCCiiivvviiilll,,, EEEnnnvvviiirrrooonnnmmmeeennntttaaalll aaannnddd MMMiiinnniiinnnggg EEEnnngggiiinnneeeeeerrriiinnnggg TThhee UUnniivveerrssiittyy ooff Adelaide Australia July 2013 TTTToooo mmmmyyyy ppppaaaarrrreeeennnnttttssss MMMMeeeeiiiihhhhuuuuaaaa aaaannnndddd BBBBiiiinnnnyyyyiiiinnnngggg V Statement of Originality I certify that this work contains no material which has been accepted for the award of any other degree or diploma in any university or other tertiary institution and, to the best of my knowledge and belief, contains no material previously published or written by another person, except where due reference has been made in the text. In addition, I certify that no part of this work will, in the future, be used in a submission for any other degree or diploma in any university or other tertiary institution without the prior approval of the University of Adelaide and where applicable, any partner institution responsible for the joint-award of this degree. I give consent to this copy of my thesis when deposited in the University Library, being made available for loan and photocopying, subject to the provisions of the Copyright Act 1968. The author acknowledges that copyright of published works contained within this thesis resides with the copyright holder(s) of those works. I also give permission for the digital version of my thesis to be made available on the web, via the University’s digital research repository, the Library catalogue and also through web search engines, unless permission has been granted by the University to restrict access for a period of time. Name: Jiayi Shen Signature: Date: 17th July 2013 VI VII Acknowledgments I gratefully acknowledge my supervisors Dr. Murat Karakus, Associate Prof. Chaoshui Xu and Prof. Stephen Priest, for their invaluable guidance, encouragement and constructive criticism during my candidature period. Without their great contribution this thesis would not be possible. I am particularly grateful to Dr. Murat Karakus for not only gives research supports but also offers encouragement and emotional supports in the past three years. I would like to sincerely thank the China Scholarship Council and the University of Adelaide for providing the joint PhD scholarship. I would like to express my gratitude to Mrs Barbara Brougham for editing the submitted and published journal papers which are composed of the thesis. Many thanks go to Associate Prof. Rafael Jimenez for supervision and cooperation on the rock failure criterion research topic when I was a visiting scholar in the E.T.S.I Caminos, Canales y Puertos at the Universidad Politécnica de Madrid, Spain. Many thanks go to Prof. Jian Zhao for hosting me as a visiting scholar at Laboratory for Rock Mechanics at the Swiss Federal Institute of Technology Lausanne, Switzerland. Many thanks go to all the staff of the School of Civil, Environmental and Mining Engineering for their individual help and support. I am especially grateful to Dr. Stephen Carr for helping to install research softwares and for providing IT supports. Finally, I would also like to thank my parents, for supporting me emotionally during my PhD research. VIII IX Introduction Design of rock slope is one of the major challenges at every stage of open pit mining operations. Providing an optimal excavation design based on a robust analysis in terms of safety, ore recovery and profit is the ultimate goal of any slope design. The rock slope stability is predominantly controlled by the strength and deformation of the rock mass which characteristically consists of intact rock materials and discontinuities. Initially, movement of the slope occurs due to stress relaxation as a result of removal of rocks which used to provide confinement. This behavior of slope can be attributed to linear elastic deformation. In addition to this, sliding along discontinuity surfaces and dilation in consequence of formation of cracks can occur. Ultimately all these instabilities lead to failure of the slopes. Therefore, formulation of slope designs plays critical role in the process of slope stability. In conventional approaches for assessing the stability of a homogeneous slope, such as the limit equilibrium method (LEM) and shear strength reduction (SSR) method, rock mass strength is usually expressed by the linear Mohr-Coulomb (MC) criterion. However, rock mass strength is a non-linear stress function. Therefore, the linear MC criterion generally do not agree with the rock mass failure envelope, especially for slope stability problems where the rock mass is in a state of low confining stresses that make the nonlinearity more dominant. With the aim of better understanding the fundamental rock slope failure mechanisms and improving the accuracy of the rock slope stability results, this research focuses on the application of the Hoek-Brown (HB) criterion, which can ideally represent the non-linear behavior of a rock mass, on the rock slope stability analysis. There, three major sections are available in the thesis. The first section, from Chapters 1 to 4, proposes new methods for estimating the intact rock and rock mass properties, which will be X used for slope stability analysis. In the second section studied in Chapter 5, a new non-linear shear strength reduction technique is proposed for the analysis of three-dimensional (3D) slope modeling. In section three (Chapter 6), novel stability charts are proposed, which have the merit of estimating factor of safety (FOS) for a given slope directly from the HB parameters and rock mass properties. These charts can provide a quick and reliable assessment of rock slope stability. The major research contributions and outcomes of the overall researches are presented in six journal publications which are forming the thesis. The titles of Chapters 1 through 6 reflect the titles of the journal papers. In Chapter 1, laboratory tests conducted on Hawkesbury sandstone obtained from New South Wales are carried out to investigate the relationship between the HB constant m and i uniaxial compressive strength (UCS) of intact rock. Based on the analysis of the laboratory tests and the existing database, a new method that can estimate the HB constant m values from UCS i and rock types is proposed. The proposed method can reliably be used in the HB criterion for intact rock strength estimation when the triaxial tests are not available. In Chapter 2, an analytical solution for estimating the instantaneous MC shear strength from the HB failure criterion for highly fractured rock mass is presented. The proposed solution is based on the assumption that the HB parameter, s is equal to zero. The proposed solution has the merit of producing very accurate shear strength for highly fractured rock mass where the Geological Strength Index (GSI) is less than 40. In Chapter 3, an analytical solution, which can calculate the shear strength of rock masses accurately for the whole range GSI values, is proposed as an extension to the work in Chapter 2. The proposed approach is based on a symbolic regression analysis performed by genetic programming (GP). The proposed solution not only can be implemented into the LEM to XI