When simulating the directional blasting process, many researchers focus on the cutting and splitting effects who might pay more attention on the crushing effects when studying conventional cut blasting. In this case, a numerical tool capable of capturing the strong discontinuity processes of quasi-brittle materials is highly preferable, where many blasting parameters should be calibrated and inputted. In this work, a hybrid finite-discrete elements method with explicit iterative procedure named Continuous-Discontinuous Elements Method (CDEM) is adopted to study the directional rock blasting processes. Landau model is used to capture the detonation effects, where the parameters are calibrated by comparing to the results provided by published literatures. We found that: i) The crack propagation mode of directional rock blasting is similar to those found in Brazilian splitting tests where the crack initiates from the midpoint of the connecting line of blast holes; ii) Compared with traditional cut blasting, the free surface has no significant influence on the blasting effect of directional cut blasting, while the spacing of the hole has great influence on the cutting effect. The index of fracture degree can be used to evaluate the blasting effect quantitatively. This work partly reveals some cracking patterns and rules of directional rock blasting, which may assist the engineers to develop improved precise blasting technologies.

During blasting, rock failure is caused by blasting wave and explosive gas pressure, as a multi-field coupled process. Most numerical models focus on the effect of blasting wave where the gas pressure is commonly accounted for by empirical relations, ignoring the penetration and permeation of gas flow in cracks. This can underestimate the failure region. In this work, a novel multi-field model is developed in the framework of a continuous-discontinuous element method (CDEM), which is a coupled finite-discrete method with explicit integration strategy. The deformation and cracking of rock mass and the distribution of gas pressure are captured. The proposed method is verified by comparing the results to other results provided in published literature. Especially, by simulating the cases with blocked and unblocked blasting hole, we found that: (i) The fracture degree of the case with blocked blasting hole was 30% higher than that of the unblocked blasting hole. (ii) The radial main cracks in the fracture area are mainly caused by the explosive gas, and the tiny and dense cracks near the hole are induced by the explosion stress wave. (iii) The explosion crushing zone is mainly formed by the action of explosion stress wave, while the crack zone is formed by the combined action of the explosion stress wave and explosive gas. The proposed method provides a useful tool to properly simulate a rock blasting process.

To analyse the feasibility of the low-grade highway as a launch site in military applications and improve the pavement crushing technology in civilian applications, this study investigates the evolution characteristics of a low-grade highway under impact load, including deflection, crack, and energy, via the continuum–discontinuum element method (CDEM). To this end, this paper proposes an energy statistics algorithm, and the correctness is verified. Then, a quarter three-dimensional numerical model of an asphalt concrete highway is established, and the effectiveness of CDEM in simulating the deflection of the highway under impact load is validated. Finally, an existing asphalt concrete highway structure is selected to study the evolution characteristics via numerical simulation. The results demonstrate the consistency between the variations of deflection at the load centre and the impact load. The deflection is primarily caused by the compressive deformation of subgrade. Crack planes mainly occur when the impact load increases rapidly. The variation of various constituent energies is different but closely related to the change in impact load.