# Experimental Study on the Compression Behavior of Ground Rock with Bi-Directional Penetrating Crack
###### Abstract  
Grouting is a common method of reinforcing fractured rock mass. The mechanical property of grouted rock is a major aspect of the reinforcement effect, which depends on the geometry of the crack, the angle (\(\beta\)) between the load direction and the crack, and other factors. Few studies have focused on grouted rock with bi-directional crack which can reflect well the grouting reinforcement in the stratum with developed fractures. To explore the grouting effect on fractured rock mass, uniaxial compression tests were carried out on grouted rock samples with different bidirectional widths (t) and angles cracks. The results showed that: (1) when the \(\beta\) was \(30^{\circ}\), the failure mode was sliding along the interface of rock and grout, when the \(\beta\) was \(45^{\circ}\), the failure mode was composite failure mode, and when the \(\beta\) was \(0^{\circ}\), \(60^{\circ}\), or \(90^{\circ}\), the failure mode was typical intact rock failure mode; (2) when the \(\beta\) increased from \(0^{\circ}\) to \(90^{\circ}\), the uniaxial compressive strength (UCS) decreased and then increased again; (3) when the \(\beta\) was \(30^{\circ}\), the UCS had nothing to do with the grout thickness, and when the \(\beta\) was not \(30^{\circ}\), the greater the grout thickness, the greater the compressive strength and the ultimate energy storage capacity. The test results can provide reference for grouting reinforcement construction and design in the underground excavation process. grouting reinforcement; fractured rock mass; penetrating crack; mechanical properties +
Footnote †: journal:[PERSON] et al. [11] quantitatively studied the reinforcement effect of permeation grouting on a jointed rock mass and pointed out that the geometric and mechanical characteristics of the joints affected the grouted rock mass. [PERSON] et al. [12] and [PERSON] et al. [13], based on the results of theoretical analyses and direct shear tests, developed a peak shear strength model. In addition, several shear tests were conducted on cemented concrete-rock joints to investigate rock-concrete interaction [14; 15; 16]. The interface between the grout and rock is only a part of the grouted rock, which cannot reflect the overall mechanical properties. In practice, the grout, interface, and original rock jointly bear the external force. At the same time, in the underground environment, the rock mass is more compressed rather than sheared. Therefore, the mechanical behavior of the whole grouted rock under compression is also one of the research focuses. The mechanical properties of the whole grouted rock depend on the geometry of the original cracks, the combination of the cracks and the original rock, the angle between the cracks and the principal stress, and the mechanical properties of the grout. At present, there are many studies on grouted rock with single or multiple unidirectional penetrating cracks. Generally, the standard sample with prefabricated cracks is used as the experimental subject, which is shown in Figure 1. [PERSON] et al. [17; 18; 19] comparatively analyzed the compressive behavior of grouted rock samples with single unidirectional penetrating cracks (as shown in Figure 1a) of different inclination angles, length, and width before and after grouting under uniaxial compression or triaxial compression. [PERSON] et al. [20] compared the reinforcement effect of different grouting materials in rock mass with single crack. [PERSON] et al. [21] analyzed the compression behavior of rock samples with two unidirectional penetrating cracks (as shown in Figure 1b) after grouting by particle mechanics model. [PERSON] et al. [22] analyzed the effect of grouting on the specimen with cavity and crack (as shown in Figure 1c) under uniaxial compression. The mechanical experiments of grouted rock with unidirectional through cracks can reflect the reinforcement effect and the process of crack re-expansion at the location where the local cracks are not well developed.