岩溶区特大断面小净距隧道群综合探测成果分析

为保证某岩溶区特大断面小净距隧道群安全施工，采用高密度电阻率法勘探、钻探及声波测试对该隧道群围岩进行了综合探测。高密度电阻率法勘探成果显示测线内覆盖层厚度在0~1.3 m之间，强风化层厚度在4.0~21.0 m之间，基岩表面溶沟溶槽发育，并推测了存在溶洞的位置。声波测试结果显示隧道围岩为可溶岩，岩溶微发育；隧道围岩完整性系数在0.49~0.64之间。现场已施工的37个钻孔中，有2个遇溶洞/裂隙，钻孔遇洞率5%。高密度电阻率法勘探与钻孔及声波测试所得的地下地质体信息吻合。综合物探成果很好地解释了隧道群围岩的地质情况，可以作为岩溶区特大断面小净距隧道群隧道设计、施工的初步依据。

Analysis of Comprehensive Detection Results of Large Section and Small Clear Distance Tunnel Group in Karst Area

To ensure the safe construction of large section and small clear distance tunnel group in a karst area，the surrounding rock of a tunnel group was detected by high density resistivity method for prospecting，exploration drilling and acoustic testing. The prospecting results show that the thicknesses of overburden within the survey line are between 0-1.3 m，the thicknesses of strong weathering layer are in the range of 4.0-21.0 m，the karren and solution groove on bedrock surface are developed，and the location of karst cave is inferred. The acoustic wave test results show that the surrounding rock of the tunnel is soluble rock and karst is micro-developed；the intactness indexes of surrounding rock are between 0.49 and 0.64. Thirty seven boreholes have been constructed on site，and 2 of them have encountered Karst caves/cracks，with a hole encounter rate of 5%. The information of the underground geological body obtained by high-density resistivity method is consistent with that using borehole and acoustic tests. The complex geophysical prospecting results well explain the geological conditions of the tunnel surrounding rock and can be used as the preliminary reference for the design and construction of the tunnel group with large section and small clear spacing in karst area.