铁路双线隧道围岩爆破松动范围测试分析

Test Analysis on the Broken Rock Zone of the Surrounding Rock Blasting for Railway Double-Line Tunnel

在地处典型石灰岩地层的贵广铁路牛王盖双线隧道,选择IV级围岩地段的3个断面进行围岩爆破松动影响范围的测试。每个断面钻7个直径40 mm、深4.0～4.5 m的探孔,采用超声波方法测试并分析围岩爆破松动圈的大小、形状及主要影响因素。结果表明:围岩爆破松动圈内比松动圈外的围岩声波波速小10%～20%,松动圈内岩体的破碎程度与围岩声波的波速降低相关;采用控制爆破,总装药量在180 kg和最大一段装药量在28 kg时,Ⅳ级围岩爆破松动圈的范围一般为0.9～1.5 m,当围岩附近有溶洞或破碎带时,该处的围岩爆破松动范围将成倍增加,需要采用拱架支护,以防塌方。

Niuwanggai double line tunnel of Gui-Guang Railway is located in the typical limestone stratum,in which three sections of IV-level surrounding rock were chosen to detect the broken rock zone of the surrounding rock blasting.Seven holes with the diameter of 40 mm and the depth of 4.0～4.5 m were bored in each section.The range and the form of the broken rock zone were detected and studied with the ultrasonic method,and the dominating factors deciding the broken rock zone was also analyzed.The results indicate that the acoustic wave velocity of the surrounding rock within the broken rock zone is 10%～20% lower than that outside the broken rock zone,and the degree of the rock mass breaking is correlative with the acoustic wave velocity of the surrounding rock.The tunnel is constructed with the controlled blasting technology,the range of the broken rock zone of the tunnel in Ⅳ-level lime surrounding rock is 0.9～1.5 m when the total mass of the charge is 180 kg and the maximum charge for the largest interval is 28 kg.If there is karst cave or faultage around the tunnel,the broken rock zone of the surrounding rock blasting will be doubled.Accordingly,the arch support should be required against collapsing.