There are many geophysical methods for advanced geological
prediction. Due to the complexity of spatial distribution of Karst development
and diversity of fillings of Karst waterbearing media, single advanced
geological prediction method has limitations. It is necessary to select
suitable geophysical methods or combinations of geological prediction to
improve the accuracy of prediction results according to the geophysical
characteristics of Karst. The theoretical basis and method selection of
advanced geological prediction method for Karst tunnels are discussed by
analyzing the working principle, effective detection distance and geophysical
characteristics of main geophysical prediction methods such as TSP method,
geological radar method and transient electromagnetic method. Several main
advanced geological prediction methods and combinations used in Hejia Tunnel of
Jiujingqu Railway are discussed in detail during construction. Through
comparative analysis, the applicability and accuracy of prediction results of
several main geophysical prospecting methods are verified and summarized. The
applicable results show that: (1) Single advanced geological prediction method
has limitations and is difficult to cope with complex geological conditions and
high construction risk of Karst tunnels; it is necessary to adopt the measures
of "three combinations" and select different advanced prediction
methods as combinations to verify each other. (2) The TSP method fails to
distinguish between Karst and fault fracture zones, so it must be combined with
other methods to carry out comparative verification in order to distinguish
them; the combination of TSP method and geological radar method is a common
combination for simple Karst tunnels. (3) The transient electromagnetic method
has obvious effect in Karst tunnel detection with high accuracy of
interpretation, and is suitable for large stronglydeveloped
Karst areas. The combination of advanced horizontal drilling + transient
electromagnetic method + geological radar method + hydrological monitoring
geological prediction is an effective combination for advanced geological
prediction of complex Karst tunnels. The analysis of superimposed advanced
horizontal drilling and transient electromagnetic profiles can provide a
detailed analysis of the spatial distribution and morphological characteristics
of Karst.
YAN Jun
. Selection and Application of Several Main Geophysical
Methods for Advanced Geological Prediction of Karst Tunnels[J]. Tunnel Construction, 2020
, 40(S1)
: 327
-336
.
DOI: 10.3973/j.issn.2096-4498.2020.S1.042
