# Investigation of Rock Joint and Fracture Influence on Delayed Blasting Performance
## 6 Conclusions  
Under the condition of a 24 m highwall bench and large-diameter vertical drilling at a Barun mine, the distribution of blasting-induced stress under a delayed detonating explosive within fractured rock mass is analyzed. The following conclusions are obtained:  
1. By constructing a nonlinear joint blasting model and introducing the detonation wave propagation velocity simplification into the vibration velocity of the incident particle at the joint interface, the incident P-wave incident joint is obtained. The peak value is at 3.0 s with a peak vibration velocity of 0.33 m/s; the S-wave reflected from the joint interface is first reflected backward and then forward. The peak vibration velocity of the particle is 0.027 m/s.
2. By combining with the relevant theories of stress and displacement field at the crack end of type I and II cracks, it is obtained that the joint presents asymmetric characteristics around the stress field. The end \(\sigma_{x}\) is positive in the direction of 0\({}^{\circ}\)-330\({}^{\circ}\) subject to tensile stress, whereas \(\sigma_{y}\) is positive in the direction of 0\({}^{\circ}\)-180\({}^{\circ}\) under tensile stress; the longitudinal stress \(\sigma_{y}\) of the joint is low around the compressive stress distribution area. At this point, the rock material does not fail, and the stress concentration appears in the lower-right position. The lateral displacement of the joint ends is significantly affected by the stress components in both directions.
3. Based on the analysis results of ANSYS, it is found that the intensity of the shock wave after detonation is greater than the strength of the rock. Then, the sub-layer shock wave supplements the energy of the shock wave that is not enough to break the rock and induces further cracking. Based on the analysis results on the attenuation of detonation wave energy, the stress exhibits a decreasing trend in the process. By constructing a variation diagram of the peak effective stress, it is found that the peak value first increases to 10-12 MPa and then shows a downward trend.  
The main contents of this research are as follows:  
Firstly, the construction of a simulation model for a jointed rock mass model under blasting is presented. This is achieved by combining a nonlinear joint model, hyperbolic joint constitutive model (BB model) of normal nonlinear deformation, and tangential linear deformation. Subsequently, the function of the P-wave joint incident propagation is deduced. By selecting \(\delta\) as the factor of the stress wave function, the relationships between reflecting and incident wave points, the peak value of vibration velocity, and time  
Figure 6: Change in peak effective stress at selected points. (**a**) Finite element simulation results, (**b**) theoretical calculation results.  
were investigated. MATLAB is used to analyze changes in the stress and displacement of particles around the joints.  
Based on existing technological conditions, the influence of stress distribution of rock mass under delayed blasting of the jointed rock mass is studied. The analysis results show that the peak stress first reaches 10-12 MPa, followed by a decreasing trend. The particle changes of the two analysis methods have the same trends, which are subsequently verified by the results of a finite element simulation and mathematical analysis.  
Conceptualization, P.Z. and X.S.; methodology, P.Z.; software, P.Z.; validation, P.Z., X.S. and T.W.; formal analysis, X.S.; investigation, X.S.; resources, T.W.; data curation, T.W.; writing--original draft preparation, P.Z.; writing--review and editing, P.Z.; visualization, P.Z.; supervision, R.B.; project administration, R.B.; funding acquisition, R.B. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The study did not involve humans.  
The authors declare no conflict of interest.