Advance Geological Forecast Method And Its Engineering Application In Xuda Railway Karst Tunnel

Since the reform and opening-up, accompanied with the rapid development ofeconomy and transport in China, tunnel engineering and underground engineeringalso entered a period of speedy development. However, the large distribution of thekarst area and the various karst landforms caused frequent occurrence of geologicaldisasters during the tunnel construction process, which is a serious threat to theconstruction safety. Therefore, scientific and effective using of advance geologicalforecast technology plays an important role in tunnel construction safety, which isalso a difficulty need to be solved in nowadays.In this article, Xuda railway karst tunnel was chose for research. Based on thecollection of previous research data and the analysis of basic characteristics of avariety of detection methods, the basic principles and methods of TSP and GroundPenetrating Radar (GPR) were studied. Moreover, with the research of these twomethods’ particle engineering application, the comprehensive advance geologicalforecast system was established. By summarizing, the conclusions are as follows:（1）Based on the systematic analysis of regional engineering geologicalconditions of tunnel setting, the types of harmful geology structure development weredetermined by geological analysis, and corresponding detection methods weredecided: the ground penetrating radar was applied in karst caves, while the groundpenetrating radar and TSP were used together in fracture zone and water-rich zone.（2）As ground penetrating radar was used in the excavation of smallcross-section, its arrangement way of survey line was studied. According to threecommonly used excavation way in karst tunnel, the arrangement ways of survey linewas determined respectively:“octothorpe shaped line” and “A horizontal and threevertical shaped line” were used in full-section excavation;“octothorpe shaped line”and “one survey line along with the outline of tunnel face on the upper bench and two horizontal survey lines in the middle and bottom” were used in bench excavation;“ring shaped line along with the tunnel face” was used in reserved core soil cyclemethod.（3）Geological radar image corresponding realations with the typical harmfulgeology structure was summarized. According to the engineering applications ofground penetrating radar, We choose homophase property、amplitude and wavefoemcharacteristic as index, study on four types of harmful geology structures’ detection,including fracture zone, close jointed zone, water-rich zone and karst cave.（4）The study on the application of TSP geological in karst tunnel find that thecorrect choice of sidewallwhich laid embrasure is a key factor of ensure data quality,TSP technology is not at prediction the structural plane that developed approximatelyparallel to the tunnel axis and unable to detect the cave developed location and itssize.（5）Based on the above results，We suggest the comprehensive advancegeological forecast system. Based on the geological analysis method, define therelated geophysical parameters，use TSP, a long-term method, and GPR, a short-termmethod, together, compare the prediction result with the actual excavation, andconstantly feed back and summary.