The Static Breaking Technique for Sustainable and Eco-Environmental Coal Mining

Abstract

The initiating explosive devices are prohibited in rock breaking near the goaf of the highly gassy mine. It is effective and applicable to cracking the hard roof with static cracking agent. By testing the static cracking of cubic limestone (size: 200 × 200 × 200 mm) with true triaxial rock mechanics testing machine under the effect of bidirectional stress and by monitoring the evolution process of the cracks generated during the acoustic emission experiment of static cracking, we conclude the following: the experiment results of the acoustic emission show that the cracks start from the lower part of the hole wall until they spread all over the sample. The crack growth rate follows a trend of “from rapidness to slowness.” The expansion time is different for the two bunches of cracks. The growth rates can be divided into the rapid increasing period and the rapid declining period, of which the growth rate in declining period is less than that in the increasing period. Also, the growth rate along the vertical direction is greater than that of the horizontal direction. Then the extended model for the static cracking is built according to the theories of elastic mechanics and fracture mechanics. Thus the relation formula between the applied forces of cracks and crack expansion radius is obtained. By comparison with the test results, the model proves to be applicable. In accordance with the actual geological situation of Yangquan No. 3 Mine, the basic parameters of manpower manipulated caving breaking with static crushing are settled, which reaps bumper industrial effects.

Study on unit energy damage and prediction model of concrete under hydraulic impact

“…Among them, the crushing process of the static crushing agent is slow, and the dosage of the crushing agent is not easy to control, which is difficult to ensure the accurate and rapid requirements of concrete crushing. 3,4 The vibration and dust problems caused by engineering blasting are more prominent, which has a great influence on the surrounding environment. 5,6 Mechanical crushing has high noise and low flexibility, and there are certain limitations for the parts that need accurate crushing.…”

Mechanism of Hard Rock Static Blasting-induced Crack Expansion

“…He does this by using microscopic and electromagnetic analysis of the static and dynamic cracking of rocks. In order to further explore the properties of the static splinter-causing test object under stress through sound-release technology, Hao B. Y. and colleagues [21] employed genuine three-axis double-stress loading experiments. Laefer D. F. et al's [22] investigation of static fissures in various probe comparative intensities under the influence of ambient temperature revealed that raising ambient temperatures, lowering design comparative temperatures, and increasing melting temperatures would all hasten the expansion of the fissures.…”

Experimental investigation on basic law of rock directional fracturing with static expansive agent controlled by dense linear multi boreholes

“…Compared to hydraulic fracturing which can produce a single fracture in the rock, multiple radial fractures can be observed around the injection borehole where the static expansive agent is used. Since the static expansive agent can produce a superior network of fractures, it has been applied to the rock fragmentation to enhance hard roof caving in underground mines [29]. However, the lack of knowledge about the static expansive agent controlled fracturing process is one of the main causes of its poor market value [14].…”