地质岩土英文文献翻译.docx

1、地质岩土英文文献翻译International Journal of Rock Mechanics and Mining SciencesAnalysis of geo-structural defects in flexural topplingfailureAbbas Majdi and Mehdi AminiAbstractThe in-situ rock structural weaknesses, referred to herein as geo-structuraldefects,such as naturallyinduced micro-cracks,areextremely

2、responsivetotensilestresses. Flexural toppling failure occurs by tensile stress caused by the momentdue totheweightof theinclinedsuperimposedcantilever-likerockcolumns.Hence,geo-structural defects that may naturally exist in rock columns are modeled by aseriesofcracksin maximum tensilestressplane.Th

3、e magnitude and locationofthemaximumtensilestressin rockcolumnswithpotentialflexuraltopplingfailurearedetermined.Then, theminimum factorofsafetyforrockcolumns arecomputed by meansof principlesofsolidand fracturemechanics,independently.Next,a new equationis proposed to determine the length of critica

4、l crack in such rock columns. It hasbeen shown thatifthelengthof naturalcrack issmallerthan the lengthof criticalcrack, then the result based on solid mechanics approach is more appropriate;otherwise,theresultobtainedbased on theprinciplesof fracturemechanicsismoreacceptable.Subsequently,forstabiliz

5、ationof the prescribedrockslopes,some newanalytical relationships are suggested for determination the length and diameterof the required fullygrouted rock bolts. Finally, for quickdesign ofrock slopesagainst flexural toppling failure, a graphical approach along with some designcurvesare presentedbyw

6、hich an admissible inclination of such rock slopes andorlengthofallrequiredfullygroutedrock boltsaredetermined.Inaddition,a casestudy has been used for practical verification of the proposed approaches.Keywords Geo-structural defects, In-situ rock structural weaknesses, Criticalcrack length. . .1.In

7、troductionRock masses are natural materials formed in the course of millions of years.Since during their formation and afterwards, they have been subjected to highvariable pressures both vertically and horizontally, usually, they are notcontinuous, and contain numerous cracks and fractures. The exer

8、ted pressures,sometimes, produce joint sets. Since these pressures sometimes may not besufficiently high to create separate joint sets in rock masses, they can producemicro joints and micro-cracks. However, the results cannot be considered asindependent joint sets. Although the effects of these micr

9、o-cracks are not thatpronounced compared withlargesize joint sets, yetthey may cause a drastic changeof in-situ geomechanical properties of rock masses. Also, in many instances, dueto dissolution of in-situ rock masses, minute bubble-like cavities, etc., areproduced, which cause a severe reduction o

10、f in-situ tensile strength. Therefore,one should not replace this in-situ strength by that obtained in the laboratory.On the other hand, measuring thein-siturocktensilestrengthdue totheinteractionofcomplex parameters isimpractical.Hence,an appropriateapproachforestimationof the tensile strength shou

11、ld be sought. In this paper, by means of principles of solid and fracture mechanics, a new approach for determination of the effect of geo-structural defects on flexural toppling failure is proposed.2. Effect of geo-structural defects on flexural toppling failure2.1. Critical section of the flexural

12、 toppling failureAs mentioned earlier, Majdi and Amini 10 and Amini et al. 11 have proved that the accuratefactor of safety is equal to that calculated for a series of inclined rock columns, which, byanalogy, is equivalent to the superimposed inclined cantilever beamsas shown in Fig. 3. Accordingto

13、the equations of limit equilibrium, the moment M and the shearing force V existing in variouscross-sectional areas in the beams can be calculated as follows:(5)( 6)Since the superimposed inclined rock columns are subjected to uniformly distributed loads. . .caused by their own weight, hence, the max

14、imum shearing force and moment exist at the very fixedend, that is, at x= :(7)(8)If the magnitude of from Eq. (1) is substitutedof shearing force and the maximummoment of equivalentinto Eqs. (7) and (8), then the magnitudes beam for rock slopes are computed as follows:(9)(10)where C is a dimensionless geometrical parameter that is related to the inclinations