Effect of loading rate and time delay on the tangent modulus method(TMM)in coal and coal measured rocks

查看全文 作　　者：Zulfiqar [1]Ali;Murat [1]Karakus;Giang [1]D.Nguyen;Khalid [2,3]Amrouch 机构地区：[1]School of Civil,Environmental and Mining Engineering,University of Adelaide,Adelaide,SA 5000,Australia;[2]Australian School of Petroleum and Energy,University of Adelaide,Adelaide,SA 5000,Australia;[3]Geology&Sustainable Mining,Mohammed VI Polytechnic University,43150 Benguerir,Morocco 出　　处：《International Journal of Coal Science & Technology》索引2022年第9卷第6期,共13页 基　　金：financially supported by the Australian Coal Association Research Program(ACARP)under project C29010. 摘　　要：Non-destructive techniques of in-situ stress measurement from oriented cored rocks have great potential to be developed as a cost cost-effective and reliable alternative to the conventional overcoring and hydraulic fracturing methods.The tangent modulus method(TMM)is one such technique that can be applied to oriented cored rocks to measure in-situ stresses.Like the deformation rate analysis(DRA),the rock specimen is subjected to two cycles of uniaxial compression and the stress-tangent modulus curve for the two cycles is obtained from the stress-strain curve.A bending point in the tangent modulus curve of the first cycle is observed,separating it from the tangent modulus curve of the second cycle.The point of separation between the two curves is assumed to be the previously applied maximum stress.A number of experiments were conducted on coal and coal measured rocks(sandstone and limestone)to understand the effect of loading conditions and the time delay.The specimens were preloaded,and cyclic compressions were applied under three different modes of loading,four different strain rates,and time delays of up to one week.The bending point in the stress-tangent modulus curves occurred approximately at the applied pre-stress levels under all three loading modes,and no effect of loading rate was observed on the bending points in TMM.However,a clear effect of time delay was observed on the TMM,contradicting the DRA results.This could be due to the sensitivity of TMM and the range of its applicability,all of which need further investigation for the in-situ stress measurement. 关 键 词：Tangent modulus method TMM Deformation rate analysis DRA Time delay Strain rate