花岗岩差异性风化层的大地电磁法EH-4勘察效果研究

花岗岩地区的高速公路隧道开挖过程中,因岩体特有的差异性风化导致全、强风化层向下深切,这些岩体完整性差,裂隙发育、富水性强,存在施工安全隐患,深切的全、强风化层底界面起伏范围大且无规律,勘察难度较大。结合隧道工程勘察案例总结大地电磁法EH-4在探测花岗岩差异性风化形成的全、强风化层下切界面的效果,探索了利用物探解释划分围岩级别的可行性。最终经过工程验证,取得了较好的效果,在相似地质条件地区,值得推广。

Study on Exploration Effects of Magnetotelluric Method(EH-4)in Differential Weathering Layer of Granite

For the differential weathering of rocks,the fully-heavily weathered layer falls down in the excavation of expressway tunnel in the granite region.These rocks have poor integrity,fracture development and rich water which result in potential hazards.Wide fluctuation range and irregularity of the interface of fully-heavily weathered layer makes exploration difficult.This paper summarizes the effect of magnetotelluric method(EH-4)adopted to detect granite weathering zone,and explores the feasibility of interpreting and classifying rock grades with geophysics.This method is verified in the project and achieves better effects,which is suggested to be adopted in the ares with similar geological conditions.