瞬变电磁法和地震反射波法在不良地质洞段超前地质预报中的应用

Application of Transient Electromagnetic Method and Seismic Reflection Wave Method in Advance Geological Prediction of Hole Section with Poor Geological Conditions

物探方法是超前地质预报的主要手段,通过不良地质体与围岩物性参数差异,及时发现和预测地质条件的变化。较完整一完整围岩岩体物性参数与不良地质体物性参数存在较明显差异,有利于分辨出不良地质体;但是在地质条件差洞段的不良地质体与围岩岩体物性参数差异极小,不利于分辨出不良地质体,使得岩体质量情况和地质灾害风险预报难度极大。本次采用瞬变电磁法与地震反射波法的综合物探法,在滇中引水工程大理Ⅱ段Ⅴ_(特)类岩体开展专项超前地质预报工作,主要利用岩体视电阻率、应力梯度、纵波波速、横波波速等参数对未开挖段岩体质量和可能存在的地质灾害风险进行预测。创造性地通过“日进尺”这一指标间接对开挖岩体破碎程度进行评价,经对比,预报成果中符合长度占实际开挖过程中问题段长度的85.1%,预报结果与开挖成果较为吻合;此外,对坍塌失稳段、突泥涌水段也有明显反映,为该方法组合在不良地质洞段超前地质预报中的应用提供了借鉴。

Geophysical methods as the main means of advanced geological forecasting can detect and predict changes in geological conditions by using the differences in physical parameters between unfavorable geological bodies and surrounding rocks.When the physical parameters of the intact or nearly intact rock bodies and the unfavorable geological bodies are significantly different,it is easier to identify the unfavorable ones.However,when the geological conditions are poor,the differences in physical parameters between the unfavorable geological bodies and the intact or nearly intact rock bodies are very small,making it difficult to identify the unfavorable geological bodies,it is extremely difficult to predict the rock mass quality and geological disaster risks.This study integrates the geophysical method of transient electromagnetic method and seismic reflection wave method in the special advanced geological forecasting work for class V special rock mass in the II section of the Dali section of the Yunnan-Guizhou water diversion project.The method mainly uses the parameters of rock body resistivity,stress gradient,longitudinal wave velocity,and transverse wave velocity to predict the rock mass quality and possible geological disaster risks in the unexcavated sections.This study integrates the“daily progress”indicator in the creative evaluation of rock fragmentation in the excavated sections,the forecast results are 85.1%consistent with the excavation results,which have obvious reflection on the collapse and instability sections,and the sudden inrush of water and mud sections,providing reference for the application of the methods integration in the advanced geological forecasting of unfavorable geological sections.