水平缓倾岩层隧道爆破参数优化研究

Optimization of Tunnel Blasting Parameters in Horizontal Layered Sand-shale Stratum

在水平缓倾岩层中进行隧道爆破开挖时,由于水平软弱夹层的存在,导致隧道爆破施工时各部位出现严重的超欠挖问题。以穿越水平砂页岩互层的成昆铁路保安营隧道为工程依托,采用LS-DYNA软件对不同厚度的砂页岩互层隧道爆破效果进行模拟分析,提出了合理的爆破控制参数,并通过现场爆破试验验证了参数的可靠性。主要研究成果为:①在水平岩层中爆破开挖时,岩体沿水平方向损伤范围较大,岩体裂纹沿水平方向扩展较深,尤其是砂岩与页岩交界的地方;而沿垂直方向破损范围较小,炸药能量利用率较低。②水平砂岩互层围岩爆破效果受炮孔间距和软弱页岩厚度影响显著;页岩夹层厚度较薄时,应选用较小炮孔间距;随着页岩夹层厚度的增大,布置较大炮孔间距并结合空孔则可以有效地生成可控裂缝,取得较好的光面爆破效果。③确定了不同厚度砂页岩互层围岩爆破的最优炮孔间距:页岩厚度为5 cm、10 cm、15 cm、20 cm、30 cm时,炮孔间距最优取值分别为42 cm、46 cm、50 cm、54 cm;在水平岩层中采用钻爆法施工时,必须严格把控炮孔位置,尽可能降低爆破振动。

When excavating a tunnel in a gently sloping strata,serious overcut and undercut problems occur in various parts of tunnel blasting construction due to the existence of horizontal weak interlayer.Based on the project of Baoanying tunnel of Chengdu-Kunming Railway which passes through horizontal sand-shale interlayers,LS-DYNA software is used to simulate the blasting effect with different layer thicknesses to propose reasonable blasting control parameters.And the reliability of the parameters is verified by field blasting tests.The main research results are as follows:(1)When blasting excavation in a horizontal rock layer,the damage range of rock mass along the horizontal direction is large with long cracks,especially at the junction of sandstone and shale.On the contrary,the damage range along the vertical direction,with a small explosive energy utilization rate.(2)The blasting effect of horizontal sand-shale interlayered surrounding rock is significantly affected by hole spacing and the thickness of soft shale.When the thickness of shale interlayer is thin,smaller hole spacing should be selected.With the increase of the shale interlayer thickness,the controllable cracks can be effectively generated by arranging the hole spacing and empty holes to achieve a better smooth blasting effect.(3)The optimal hole spacing of the surrounding rock blasting with different thickness of sand-shale interlayer is determined.When the shale thickness is 5 cm,10 cm,15 cm,20 cm and 30 cm,the optimal hole spacing is 42 cm,46 cm,50 cm and 54cm,respectively.At the same time,the position of the blast hole must be strictly controlled to reduce the blasting vibration as much as possible.