Abstract:

In order to improve the accuracy of the surrounding rock classification in tunnel survey work and reduce the alteration rate of surrounding rock classification during tunnel construction, the analysis of alteration of surrounding rock classification of Funing Tunnel on YunGui Railway is carried out. Some conclusions and suggestions are drawn as follows. (1) The main reasons for the alteration of surrounding rock classification of the tunnel are inaccurate interpretation of geophysical prospecting results caused by abnormal drift, overwide interpretation of broken fault and interpretation errors, the karst development, the interlayer crushing of the rock mass, and the groundwater development. (2) The alteration amount of surrounding rock classification caused by karst development is large; hence attention should be paid to surrounding rock classification determination of karst section to avoid long section of high grade of surrounding rock. (3) Due to the interlayer crushing of the rock mass and groundwater development, the alternation rate of surrounding rock classification is generally small, which needs to be alternated combining with advance geological prediction. (4) The geomagnetic method is suitable for the long and deep tunnel with complex geological conditions; however, problems in geophysical interpretation process should be solved; and drilling should be arranged to verify the geophysical anomaly area and improve interpretation accuracy. (5) The comprehensive survey method is still the main method to determine the surrounding rock classification in railway tunnels; and the advance geological prediction and geological work in construction should be paid attention to.

Key words: Funing Tunnel, surrounding rock classification, geophysical prospecting, surrounding rock classification alteration, advance geology prediction