Abstract
The shape of a free surface is an important factor that determines the effect of bench blasting. The structural dynamics theory was applied to establish a structural failure model of the layered rock considering the impact of a blasting gas intrusion. Combined with the continuous-discontinuous element method (CDEM), the influence of rock strata on the failure mechanism of back-break was analyzed. The results show that structural failure characteristics of stratum with different dip angles are different. The bending failure characteristics of dipping-in-face stratum are stronger than that in dipping-out-of-face stratum. With the increase of the dip angle and height of rock stratum, the bending failure length of dipping-in-face stratum increases and the maximum value reaches 5.24 m. The trend of failure along the stratum surface towards the bottom increases, which is an important reason for the formation of an unfavorable shape of free surface. However, the failure depth of the gently dipping stratum and dipping-out-of-face stratum is relatively uniform; the average value is about 0.5 m. Finally, combined with the results of the bench blasting field test of the Changjiu (Shenshan) limestone mine, which is the largest in the production of sand and gravel aggregates, we verify the correctness of the theoretical analysis results. Relevant research results can provide a theoretical basis and technical support for controlling the bench blasting effect.
Highlights
The unevenness of the free surface is often caused by back-break, which increases the difficulty of the blast hole layout
By using the single degree of freedom dynamic analysis method, the stress characteristics of the rock mass behind the blast hole were analyzed and the failure law of the rock mass behind the blast hole was analyzed from the perspective of structural dynamics
(2) Combined with the continuousdiscontinuous element method (CDEM) numerical calculation method, the dynamic response characteristics of the structure were obviously different in variably dipping strata
Summary
The unevenness of the free surface is often caused by back-break, which increases the difficulty of the blast hole layout. The unreasonable shape of a free surface is easy to make the resistance line uneven and directly affects the crushing effect of the blasted rock mass [3]. It will affect the distribution of the excavated rock mass and the shape of blasting pile and increase the formation probability of the bottom foundation [4]. In bench blasting, we should pay attention to the rock breaking effect of the blasted rock and control the reasonable shape of the free surface after blasting and study the influence mechanism of the rock layer characteristics on the shape of the free surface after blasting, which is of great significance in controlling the bench blasting effect and improving the engineering efficiency
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