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二維拉張爆破定向致裂機理研究及工程應用

Study on directional fracturing mechanism and field application of two-dimensional tensile blasting

  • 摘要: 鉆爆法在巖體開挖領域得到了廣泛應用,定向斷裂控制爆破是其中的重要應用方向之一。為此,針對巖石材料力學特性,提出一種爆破后僅在孔壁預設方向產生一個近似二維單裂面的控制爆破技術——二維拉張爆破。分析了二維拉張爆破定向致裂原理,采用自主研制的試驗系統開展了二維拉張爆破可視化試驗,并在煤礦現場進行了二維拉張爆破定向切頂試驗。研究結果表明:(1)二維拉張爆破技術通過非炸藥材料(膨脹劑)瞬間反應在孔內產生高溫高壓氣體對介質產生瞬時脹裂效果,并通過二維拉張爆破裝置控制裂縫起裂及擴展方向;(2)二維拉張爆破技術通過二維拉張爆破裝置的調控作用使得孔壁在預裂方向產生集中拉應力,從而通過拉張作用在試件預裂方向產生I型裂縫,變常規炸藥爆破的隨機、分區破裂為定向、單一破裂;(3)二維拉張爆破技術在復合頂板條件下可取得理想的定向斷裂效果,有望為井工煤礦巷道定向切頂卸壓提供一種非炸藥爆破方法。研究結果有助于揭示二維拉張爆破機理,促進二維拉張爆破技術在定向破巖領域的應用。

     

    Abstract: The drilling and blasting method has been widely used due to its efficiency, ubiquity, and cost-effectiveness in the field of rock excavation, and directional fracture-controlled blasting is one of the important applications. Therefore, in response to the characteristic that the tensile strength of rock mass is much lower than its compressive strength, a blasting technique called two-dimensional tensile blasting (2D blasting) is proposed, which only produces an approximate two-dimensional single crack surface in the predetermined direction of the hole wall after blasting. The directional fracturing principle of 2D blasting was analyzed, the visualization experiments on the expansion of two-dimensional tension blasting cracks were conducted using a self-developed experimental system, and a directional roof cutting test using 2D blasting technology waw conducted at an actual coal mine. The research results indicate that: (1) The 2D blasting generates high-temperature and high-pressure gas in the hole through the instantaneous reaction of expander, which produces instantaneous expansion and cracking effect on the medium, meanwhile controls the direction of crack initiation and propagation through 2D blasting device. (2) The 2D blasting generates concentrated tensile stress on the hole wall in presplitting direction through the control of the 2D blasting device, resulting in mode I cracks through tensile fracturing, transforming the random and partitioned rupture of conventional blasting into a directional and single rupture. (3) Compared with conventional blasting, 2D blasting has a longer reaction time after initiation, about 200 ms, while conventional blasting only has less than 0.2 ms, a difference of 1000 times. This indicates that 2D blasting technology has a much smaller loading rate than conventional explosive blasting, resulting in a much smaller strain rate in the specimen than conventional explosives. Therefore, the 2D blasting technology eliminates the blasting crushed zone and makes it easier to achieve the desired directional fracture effect. (4) The 2D blasting can achieve ideal directional fracture effect under the condition of composite roof. The observation results of 10 cut holes within a 100 m test section on site show that the average crack rate inside the holes can reach over 90%. Therefore, 2D blasting technology is expected to replace explosives and become a new type of directional pressure relief technology for the mine roadway. The research results contribute to revealing the mechanism of 2D blasting and promoting the application of 2D blasting technology in the field of directional rock breaking.

     

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