特大断面隧道倒T型掏槽爆破研究与应用

Investigation and application of inverted T cut blasting for super-large cross section tunnel excavation

提出特大断面隧道倒T型掏槽爆破方法,并分析了该方法的爆破原理.以龙南隧道为工程背景,利用数值模拟对比分析了现场单楔形掏槽爆破方法与倒T型掏槽爆破方法的爆破效果,并将倒T型掏槽爆破方法运用到工程实践.研究结果表明:在掏槽爆破作用下,距炮孔底部1/4位置处爆破形成的破碎范围最大,当掏槽孔爆破时该位置受爆破作用影响最大;倒T型掏槽爆破成腔体积大于单楔形掏槽爆破成腔体积.除自由面附近的单元外,倒T型掏槽爆破作用下单元有效应力约为单楔形掏槽方式爆破作用下同一位置单元有效应力的4倍.在自由面附近,两种掏槽方式爆破产生的有效应力接近.现场试验炮孔利用率平均为90.2%,炸药单耗由试验前的0.78 kg/m^3降低到0.75 kg/m^3,光面爆破效果提高,加快了现场施工进度,节约了施工成本.

A method of inverted T cut blasting for super-large cross-section tunnel excavation was put forward.Besides,the formation mechanism of blasting cavity and were studied.Based on the engineering background of Longnan tunnel,the blasting effect of on-site single wedge and inverted T cut blasting are comparative analyzed by numerical simulation.Finally,the blasting effect of the inverted T cut blasting was verified by the field experiments.Results show that the maximum damage zone occurs at the location 1/4 blasthole length from the blasthole bottom and the location is mostly affected by cut blasting.The volume of the blasting cavity formed by the inverted T cut blasting is larger than that by the single wedge cut blasting.And the effective stress under the inverted T cut blasting is four times as large as that under the single wedge cut blasting at the same location except for the free surface.At the location near the free surface,the effective stress under two cut blasting methods is basically same.When the inverted T cut blasting is used for the tunnel blasting excavation,an average utility of 90.2%of the blasting holes can be reached,the specific charge reduces from 0.78 kg/m^3 to 0.75 kg/m^3 and the smooth blasting effect is improved obviously,which speed up the construction progress and save the construction cost.