To examine the impact of blasting source and free surface conditions on the energy proportion of rock blasting seismic waves, this study conducted two field single-hole blasting tests and vibration monitoring. The measured energy proportion of blasting seismic waves under various conditions was then analyzed in detail. A calculation model for seismic energy radiation was developed based on the crack boundary of rock blasting. Using the number of initial free surfaces as a key variable, the influence of blasting source conditions on the blasting seismic energy proportion was further investigated through numerical simulations. The results show that the measured energy proportion of blasting seismic waves in the field tests ranges from 0.83% to 11.70%. Significant variations were observed among different monitoring points, influenced by factors such as distance, propagation path of seismic waves, and blasting source conditions. Adding an additional free surface to the bench blasting with two free surfaces reduced the measured energy proportion of seismic waves by an average of 19.02%. The blasting seismic energy proportion is closely related to the computational boundary and the loading process. By consistently selecting the crack boundary of rock blasting as the computational boundary, the actual proportion of blasting seismic energy radiated outward from the blasting source can be accurately determined. The number of initial free surfaces primarily affects the energy proportion by altering the crack boundary area, with the energy proportion decreasing as the number of free surfaces increases. Under conditions with one, two, and three initial free surfaces, the blasting seismic energy proportions were 9.47%, 7.82%, and 6.36%, respectively.

The K_R resistance curve for hydraulic crack propagation in a concrete beam was determined and discussed. A semi-analytical method was introduced to calculate the hydraulic crack propagation in concrete. A series of concrete beams with various hydraulic pressures and initial crack depths were tested, and the hydraulic crack propagation in these beams was calculated. The calculated P-CMOD curves were first verified, and then the calculated K_R resistance curve for hydraulic crack propagation was determined. Based on the test results and calculation results, the following conclusions can be drawn: The proposed analysis method can accurately predict the hydraulic crack propagation process in concrete. The K_R resistance to hydraulic crack propagation in concrete decreases with the increase in hydraulic pressure but is less influenced by the initial crack depth of the test beams. In addition, the concrete beams collapse immediately under hydraulic fracturing once the K_Iw curve reaches the K_R resistance curve. This indicates that the failure of concrete structures under hydraulic fracturing occurs immediately once the driving force of crack propagation, dominated by the hydraulic pressure in the crack, becomes significant.