公路煤系地层隧道揭煤全岩断面爆破掏槽优化研究

Study on Optimization of Uncovering Coal Whole Rock Section Blasting Cut of Highway Coal-bearing Strata Tunnel at Rock Cross-cut

全岩断面爆破掏槽好坏直接决定公路煤系地层隧道揭煤全岩断面爆破效果。通过理论分析确定了公路煤系地层隧道揭煤全岩断面掏槽形式为二阶二段掏槽,并分析了其爆破成腔力学机理。以某高速公路隧道为研究对象,基于理论计算,给出了煤系地层隧道揭煤全岩断面二阶二段掏槽技术参数。采用数值分析方法,建立了公路煤系地层隧道揭煤全岩断面二阶二段掏槽计算模型,对不同掏槽参数的掏槽效率和爆破振动效应进行了分析,得到了揭煤全岩断面最优掏槽参数为:中心孔装药直径32 mm,一阶孔垂深1.2 m,一阶孔倾角70°,二阶孔垂深2.4 m和二阶孔倾角75°。在其他掏槽参数不变的情况下,进行了一阶掏槽孔参数的现场爆破试验与测试,其结果为:一阶孔装药直径由32 mm增大到35 mm时,槽腔岩石破碎程度增大不明显,约为3.5%,但爆破振动速度增大显著,约为27.5%,不利于振动控制;一阶孔深度为由1.2 m增大到1.4 m时,爆破槽腔体积减小,约为12.5%,不利于槽腔形成;一阶掏槽孔倾角由70°增至75°后,掏槽效率降低,约为8.2%,不利于掏槽。现场爆破试验结果与理论研究结论一致。研究结果为该隧道全岩断面掏槽爆破设计提供了重要依据。

The effect of the whole-rock section blasting of highway coal-bearing strata tunnel uncovering coal at the rock cross-cut is determined by the quality of cut in whole rock section blasting.Through theoretical analysis,it is determined that the cut mode of uncovering coal whole rock section in highway coal-bearing strata tunnel at the rock cross-cut is 2-step 2-segment cut,and the mechanical mechanism of the blasting cavity formation is analyzed.Taking an expressway tunnel as the research object,the technical parameters for 2-stage 2-segment cut of uncovering coal whole rock section in coal-bearing strata tunnel at the rock cross-cut are obtained by theoretical calculation.The model of 2-step 2-segment cut of uncovering coal whole rock section in coal-bearing strata tunnel at the rock cross-cut is built by numerical analysis.The cutting efficiency and blasting vibration effect with different cut parameters are analyzed obtain the optimal cut parameters of uncovering coal whole rock section blasting:the diameter of central hole charge is 32 mm,the vertical depth of the first-step hole is 1.2 m,the inclination angle of the first-step hole is 70°,the vertical depth of the second-step hole is 2.4 m,and the inclination angle of the second-step hole is 75°.Under the condition that other cut parameters remain unchanged,the field blasting test and measurement of the first-step cutting hole parameters are carried out.The result shows that(1)when the charging diameter of the first-step hole increases from 32 mm to 35 mm,the crushing degree of the rock in the cut cavity does not increase significantly,about 3.5%,but the blasting vibration speed increases significantly,about 27.5%,which is not conducive to vibration control;(2)when the depth of the first-step hole increases from 1.2 m to 1.4 m,the volume of the blasting cavity decreases by about 12.5%,which is not conducive to the formation of the cavity;(3)when the inclination angle of the first-step cutting hole increases from 70°to 75°,the cutting efficiency decreases by about 8.2%,which is not conducive to cutting.The field blasting test result is consistent with the theoretical research conclusion.The result provide an important basis for the design of cut blasting of the whole-rock section of the tunnel.