Abstract
In order to investigate the influence of the joint on the failure mode, peak shear strength, and shear stress-strain curve of rock mass, the compression shear test loading on the parallel jointed specimens was carried out, and the acoustic emission system was used to monitor the loading process. The joint spacing and joint overlap were varied to alter the relative positions of parallel joints in geometry. Under compression-shear loading, the failure mode of the joint specimen can be classified into four types: coplanar shear failure, shear failure along the joint plane, shear failure along the shear stress plane, and similar integrity shear failure. The joint dip angle has a decisive effect on the failure mode of the specimen. The joint overlap affects the crack development of the specimen but does not change the failure mode of the specimen. The joint spacing can change the failure mode of the specimen. The shear strength of the specimen firstly increases and then decreases with the increase of the dip angle and reaches the maximum at 45°. The shear strength decreases with the increase of the joint overlap and increases with the increase of the joint spacing. The shear stress-displacement curves of different joint inclination samples have differences which mainly reflect in the postrupture stage. From monitoring results of the AE system, the variation regular of the AE count corresponds to the failure mode, and the peak value of the AE count decreases with the increase of joint overlap and increases with the increase of joint spacing.
Highlights
In order to investigate the influence of the joint on the failure mode, peak shear strength, and shear stress-strain curve of rock mass, the compression shear test loading on the parallel jointed specimens was carried out, and the acoustic emission system was used to monitor the loading process. e joint spacing and joint overlap were varied to alter the relative positions of parallel joints in geometry
The curve of the S-15-22-45 sample produces two sudden drops of stress, and the varied form of the acoustic emission count has two peaks. e variation rules of acoustic emission counts with the di erent spacing are similar, and the peak value of the AE count increases with the increase of the joint spacing. e similar variation is due to the same failure mode of the specimens. e peak value of the AE count is related to the shear strength of samples. e shear strength of the specimen increases with the increase of the joint spacing. e larger the peak shear strength is, the greater the energy of the emission is. us, the peak value of the AE count is greater
The following conclusions can be drawn: (1) According to the relationship between the failure surface and the shear stress plane and the joint surface, four basic failure modes of the specimen are coplanar shear failure, shear failure along the joint plane, shear failure along the shear stress plane, and similar integrity shear failure. e joint dip angle plays a decisive role in the failure mode of the specimen. e joint overlap a ects the crack development of the specimen but does not change the failure mode of the specimen. e joint spacing can change the failure mode of the specimen, and the degree of in uence is related to the joint inclination
Summary
Fissure geometry is de ned by three geometrical parameters: joint dip angle, joint overlap, and joint spacing. E in uence of joint orientation and joint overlap on the mechanical behavior of jointed rock mass was investigated by varying α and L0, while keeping other geometric parameters constant E in uence of joint orientation and joint spacing on the mechanical behavior of jointed rock mass was investigated by varying α and d, while keeping other geometric parameters constant (e.g., L0 15 mm, Lr 20 mm, Lj 15 mm). Each specimen was assigned an ID number using the notation S-a-b-c, where S stands for the sample, a represents joint overlap L0, b is the joint spacing, and c is the inclination angle α. All specimens are loaded until specimen failure, and the load-displacement curves of the jointed samples are recorded simultaneously via a data acquisition system
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