Editorial

The writer is pleased to have been given this opportunity to offer an Editorial to Issue 4,Volume 7,2015,of our journal,for the frst time.The major focus of this Editorial is on the paper,“A theoretical derivation of the Hoek-Brown failure criterion for rock materials”by Jianping Zuo,Huihai Liu and Hongtao Li,published in this Issue.In the following,this paper will be referred to as Zuo et al.(2015).Using this paper as a vehicle,some comments will be offered on this journal’s important peer review system.

The paper is one of a great many that have appeared in the rock mechanics literature over the last 25-30 years dealing with the Hoek-Brown empirical strength criterion for rocks and rock masses.In the writer’s opinion,the present paper is one of the best and most valuable of those papers.Some of these papers have criticised the criterion,others have sought to modify or adapt it in various ways,while still more have used the criterion in developing analytical or numerical solutions to real or imagined rock engineeringproblems.Thegreatvalueof thepaperbyZuo et al.(2015) is that it considers the basis and derivation of the Hoek-Brown criterion for intact rock using a fundamental,mechanically rigorous, fracture mechanics approach.Interestingly,in a review paper prepared in 2008,the writer(Brown,2008)referred positively to a then recentlypublished paperbyZuo et al.(2008)that isreferenced in their present paper.

The Hoek-Brown empirical strength criterion was developed in the mid-to late 1970s during the preparation of the book by Hoek and Brown(1980)in order to fll a perceived need in the tools and techniques then available in rock mechanics and rock engineering.The initial development was the work of Dr.Evert Hoek who,as indicated in the important recent paper by Hoek and Martin(2014), had worked on brittle fracture and Griffth crack theory early in his career.It is not often acknowledged that the original form of what came to be known as the Hoek-Brown criterion given by Eqs.(25) and(26)in Zuo et al.(2015)was chosen to be mathematically similar to the classical Griffth criterion discussed by Zuo et al. (2015)in their Introduction.This mathematical form is refected by the square root terms in Eqs.(25)and(26).

The present paper by Zuo et al.(2015)shows how the Hoek-Brown criterion for intact rock material may be derived from frst principles using micro-mechanics principles.Importantly,a comparison of Eqs.(24)and(26)shows that the Hoek-Brown parameter,m,may be expressed as m=μσc/(βσt),whereσcandσtare the uniaxial compressive and tensile strengths of the rock,respectively;μis the coeffcient of friction for the pre-existing sliding crack surfaces,andβis a fracture mechanics parameter defned by Zuo et al.(2015).

Brown(2008)showed that,under some reasonable assumptions,μ/β≈1,so that m≈σc/σt.The paper also makes a signifcant contribution to the understanding of the brittle-ductile transition concept.Importantly,Eq.(28)shows that the confning pressure,at which internal micro-failure processes are completely constrained and the brittle-ductile transition is triggered,is also a function of the parametersμ,β,σcandσt.It is also shown that the value of the ratioσc/σtinfuences the value of the confning pressure at the brittle-ductile transition.

Obviously,the international reputation and standing of ajournal such as this depends on the quality of the papers that it publishes. Equally obviously,the quality of those papers refects primarily the qualityof thework carried out bythe authors,but it also refects the quality of the journal’s internal review and editorial processes.It is essential that the review process be intellectually rigorous,thorough,honest and constructive,all with a view to ensuring that only high quality,original papers are accepted for publication.It is one of the responsibilities of reviewers to suggest improvements tothe paper wheretheyareable todo so.Inthis journal,wealso ask authors to declare whether or not they have any confict of interest in submitting the paper for publication.The Editorial Board and Editorial Offce depend greatly on the voluntary contributions of the journal’s many reviewers.A list of the almost 300 people who acted as reviewers in 2014 was published on the last page of Volume 6,Issue 6.

A feature of the review process is that the identities of the two independent reviewers normally chosen to review each paper submitted for consideration for publication are not revealed to the authors.This is an essential safeguard for the overall integrity of the review process.However,the writer is now about to break this convention of confdentiality in order to make a salient point.The writer acted as one of the reviewers of the paper by Zuo et al. (2015)published in this Issue.Because he was already familiar with theworkof Dr.Zuo and his colleagues through theirearlierpaper(Zuo et al.,2008),because he had a close personal connection with the subject of the paper,and not least because of the overall quality of the paper,the writer found his review task to be straight-forward,stimulating and enjoyable.He was pleased to be able to recommend unhesitatingly that the paper be accepted for publication and,as is almost invariably the case even with the very best of papers,he may have suggested that a small number of minor changes be made to the text.

However,when he came to read the“in press”or online version of the paper before preparing this editorial,the writer quickly discovered a small number of errors in the text,one of them not exactly minor,that he had apparently overlooked in his initial review.(Thankfully,the Editorial Offce has now corrected these errors in the printed version of the paper.)This was a salutaryexperience for the writer who immodestly considers himself to be an experienced reviewer and editor having a good eye for detail.It also demonstrates how the quality of published papers depends,in part,on the rigour and thoroughness brought to their important tasks by our many volunteer reviewers.We are most grateful to them and to the authors who offer their contributions for publication in our journal.We all must be eternally vigilant in order to achieve and maintain the highest publication standards.

Brown ET.Estimating the mechanical properties of rock masses.In:Potvin Y, Carter J,Dyskin A,Jeffrey R,editors.Proceedings of the 1st Southern Hemisphere International Rock Mechanics Symposium(Vol.1),Perth.Perth, Australia:Australian Centre for Geomechanics;2008.p.3-22.

Hoek E,Brown ET.Underground excavations in rock.London,UK:Institution of Mining and Metallurgy;1980.

Hoek E,Martin CD.Fracture initiation and propagation in intact rock-a review. Journal of Rock Mechanics and Geotechnical Engineering 2014;6(4):287-300.

Zuo JP,Li HT,Xie HP,Ju Y,Peng SP.A nonlinear strength criterion for rocklike materials based on fracture mechanics.International Journal of Rock Mechanics and Mining Sciences 2008;45(4):594-9.

Zuo JP,Liu HH,Li HT.A theoretical derivation of the Hoek-Brown failure criterion for rock materials.Journal of Rock Mechanics and Geotechnical Engineering 2015;7(4):361-6.

E.T.Brown,

Honorary Editor-in-Chief

Golder Associates Pty.Ltd.,PO Box 1734,

Milton,QLD 4064,Australia

E-mail address:tbrown@golder.com.au.

Available online 25 June 2015

Peer review under responsibility of Institute of Rock and Soil Mechanics, Chinese Academy of Sciences.

1674-7755?2015 Institute of Rock and Soil Mechanics,Chinese Academy of Sciences.Production and hosting by Elsevier B.V.All rights reserved.

http://dx.doi.org/10.1016/j.jrmge.2015.06.002