Experimental study on high pressure nitrogen blasting fracture for coal and rock mass

FIGURE 1: High pressure nitrogen blasting and cracking experimental system of coal and rock mass.FIGURE 2: Molding experimental blocksFIGURE 3: Release tube and its dimensional drawing. (a) Release tube; (b) dimensional drawing of release tube.FIGURE 4: The macroscopic crack morphology on the experimental blocks’ surface under the designed condition of 1L gas volume. (a) P=5MPa; (b) P=7.5MPa; (c) P=10MPa.FIGURE 5: The macroscopic crack morphology on the experimental blocks’ surface under the designed condition of gas pressure of 10 MPa. (a) V=1L; (b) V=2L; (c) V=3L.FIGURE 6: p-t curve of high pressure nitrogen fracturing under different design gas pressure conditions. (a) P=5MPa; (b) P=7.5MPa; (c) P=10MPa.FIGURE 7: p-t curve of high pressure nitrogen fracturing under different design gas volume conditions. (a) V=1L; (b) V=2L; (c) V=3L.

图1：煤岩体高压氮气爆破致裂实验系统。
图2：成型实验块。
图3：泄压管及其尺寸图纸。(a) 泄压管；(b) 泄压管尺寸图纸。
图4：气体容积为1L的预设工况下实验块表面宏观裂纹形貌。(a) P=5MPa；(b) P=7.5MPa；(c) P=10MPa。
图5：气体压力为10MPa的预设工况下实验块表面宏观裂纹形貌。(a) V=1L；(b) V=2L；(c) V=3L。
图6：不同预设气体压力工况下高压氮气压裂的压力-时间（p-t）曲线。(a) P=5MPa；(b) P=7.5MPa；(c) P=10MPa。
图7：不同预设气体容积工况下高压氮气压裂的压力-时间（p-t）曲线。(a) V=1L；(b) V=2L；(c) V=3L。