STRENGTH AND FRACTURE CHARACTERISTIC OF ROCK MASS CONTAINING PARALLEL FISSURES

In order to investigate the strength characteristic and crack extension law of rock mass containing parallel fissures, uniaxial compression tests of rock-like samples with different fissure angles were conducted combined with the digital photography measurement system. The results show that the degradation of peak strength and elastic modulus of samples is about 10.84%~35.62% and 9.79%~54.17% respectively with the effect of preset fissures. With the increase of the fissure angle, the peak strength of samples decreases first and then increases, forming a typical characteristic of “U” type, and it reaches the minimum value as θ is 45°. The failure form is closely related to the fissure angle. The extending types of secondary cracks are mainly inclined cracks and central cracks when the joint angle is 15° or 30°, and the final instability fracture mode is due to the inclined cracks. However, when the joint angle is 45°, 60° or 75°, the extending types of secondary cracks are mainly wing cracks and coplanar cracks, and the final instability fracture mode mainly depends on the coplanar cracks.