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Qin S.-L.,CAS Wuhan Institute of Rock and Soil Mechanics | Yang L.-Q.,CAS Wuhan Institute of Rock and Soil Mechanics | Yang L.-Q.,Zhejiang Engineering Investigation Institute | Gao H.,CAS Wuhan Institute of Rock and Soil Mechanics | Chen S.-X.,CAS Wuhan Institute of Rock and Soil Mechanics
Yantu Lixue/Rock and Soil Mechanics | Year: 2015

Acoustic emission (AE) will evidently accompany in the process of deformation and grain crushing of the coarse aggregates. Monitoring the acoustic emission signal characteristics of the coarse aggregates under the action of external force can be used to study the crushing mechanism. This paper studies the acoustic emission characteristics of sericite schist coarse aggregates. It uses the coupled acoustic emission large-scale triaxial test apparatus to carry out the conventional consolidated drained triaxial tests, the constant volumetric stress p and the constant deviatoric stress q tests on sericite schist coarse aggregates. The acoustic emission signals are monitored. The test results show that the acoustic emission of coarse aggregates is mainly from the particle breakage, sliding friction and rolling friction. The activities of inter-particle sliding, rolling and particle breakage are severely affected by different confining pressures and different stress levels. So the proportions of frictional AE and fractured AE are different at different stress levels. Under the constant p stress path test, the inflection point of accumulative acoustic emission signals appears, which can judge the strain softening point. The acoustic emission during the constant q test is obviously lower than that during the constant p test. The growth rate of accumulative acoustic emission parameters is gradually increased with the volumetric stress increasing in the constant p test. However, the growth rate of accumulative AE parameters is gradually decreased with the deviatoric stress increasing in the constant q test. It can be deduced that the acoustic emission of coarse aggregates is greatly influenced by shear stress. ©, 2015, Academia Sinica. All right reserved. Source


Qin S.-L.,CAS Wuhan Institute of Rock and Soil Mechanics | Yang L.-Q.,CAS Wuhan Institute of Rock and Soil Mechanics | Yang L.-Q.,Zhejiang Engineering Investigation Institute | Chen R.-H.,CAS Wuhan Institute of Rock and Soil Mechanics | Chen S.-X.,CAS Wuhan Institute of Rock and Soil Mechanics
Yantu Lixue/Rock and Soil Mechanics | Year: 2014

In order to further clarify the effect of particle breakage on strength and deformation of soft rock coarse aggregates, consolidation drained triaxial shear tests of two groups of different initial dry densities of sericite schist coarse aggregates are carried out. The law of particle breakage and its influence on mechanical properties of sercite schist coarse aggregates are discussed. The result shows that the relative particle breakage index of sercite schist coarse aggregates increases with confining pressure. But the growth rate of particle breakage is greatly influenced by the initial dry density. The relationship between particle breakage and confining pressure might be described by a linear function. The particle breakage of high density samples is significantly higher than low density samples under the same stress level because of the influence of the initial porosity. So influence of particle breakage on shear strength decrease under the high density is higher than the influence of low density samples; this might cause stress strain curve of two different dry densities to intersect somewhere. Finally, the shear strength of low density is greater than the high density samples. The porosity of high density sample is small and its dilatancy factor always stay near 1.The porosity of low density sample is larger and the particle breakage and dilatancy delay the impact on its dilatancy factor. So the lower density of samples, the larger volume change is. However, the volume change is very small because of the influence of particle breakage and dilatancy of sericite schist coarse aggregates. ©, 2014, Academia Sinica. All right reserved. Source


Qin S.,CAS Wuhan Institute of Rock and Soil Mechanics | Yang L.,CAS Wuhan Institute of Rock and Soil Mechanics | Yang L.,Zhejiang Engineering Investigation Institute | Gao H.,CAS Wuhan Institute of Rock and Soil Mechanics | And 2 more authors.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2014

Coarse aggregates of sericite schist are widely used in the construction of Gucheng-Zhuxi expressway as subgrade fillings. In order to study the mechanical properties of coarse aggregates of sericite schist, a series of large-scale triaxial tests under different stress paths were carried out, including the conventional drained triaxial, conventional undrained triaxial and constant p tests. All of the stress-strain curves under the low confining pressures exhibited the strain hardening phenomenon. However, the stress-strain curves exhibited the weak strain softening behavior under the high confining pressures. The volumetric strains were found to be mainly shear contraction under different confining pressures, and no shear dilatancy behavior appeared under low confining pressure. The reason of the abnormal strain change behaviour was explained through the analysis of the breakage characteristics of particles. In addition, it is verified that the Duncan's nonlinear strength criterion has a good applicability for the sericite schist coarse aggregates. Source

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