Abstract
The depth of mineral resources like coal continuously increases due to the exhaustion of shallow resources, and the characteristic of high ground stress in deep ground inevitably affects fracture of rock blasting. Combining with high‐speed photography technology, the digital image correlation method (DIC) is introduced into experimental study on explosive mechanics. And strain evolution process of blasting under high stress condition is obtained by using the model experiment method. The preliminary results show that high stress condition has no obvious effects on the propagation law of blasting stress wave or its stress peak in the medium. In addition, it is found that medium in the “elastic vibration area” by conventional blast zoning is not always “elastic,” and on this basis, the concepts of “plastic area” and “quasielastic area” are put forward. The high stress condition does not influence partition range of above “plastic area” or “quasielastic area,” but in the “plastic area,” the high stress condition decreases both plastic strain value and its decay rate of relevant gauging points.
Highlights
In recent years, the state of mineral resource exploitation like coal is shifted from the open air to the underground and from the shallow to the deep; resource exploitation environment is more complex, and the exploitation difficulty increases dramatically
Eight gauging points are selected in each specimen for strain monitoring as shown in Figure 3. e polar coordinate system is established with the center of borehole as the coordinate origin. e distance s between gauging points G1, G2, G3,···, G8 and the borehole is respectively 35 mm (7d), 40 mm (8d), 45 mm (9d), and 70 mm (14d)
Based on the experimental results, it is suggested that the “elastic vibration area” in traditional blasting partition should be further modi ed as “plastic area” and “quasielastic area.”
Summary
The state of mineral resource exploitation like coal is shifted from the open air to the underground and from the shallow to the deep; resource exploitation environment is more complex, and the exploitation difficulty increases dramatically He [1] pointed out that the high ground stress is a significant difference between deep mining and shallow mining, which is a problem that must be faced and solved by deep mining. Bai [4] found the ground stress field has a guiding effect on the expansion of blasting induced crack, and main direction of the crack propagation tends to the direction of the maximum principal stress. The full field strain evolution of blasting under high stress condition is analyzed by model experiment with experimental system of high-speed digital image correlation
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