FEATURES OF WATER BURST WHEN BUILD NANCHUAN TO DAOZHEN SANQUAN TUNNEL UNDER THE UNDERGROUND RIVER

On account of the complexity of the karst growth, it is difficult to predict water burst during tunnel construction. By methods of investigation and observation, this article take the Sanquan tunnel for example, to find the distribution, types, connectivity, and response after rainfall of water burst. The tunnel water burst range on K7+047 to K7+0130. The water burst is increased in the direction of rock tendency. Water burst mainly appear in the direction of underground river origin. Water burst points are connected. Under the influence of rainfall, rock fracture water burst vary in small amplitude, and karst pipe water burst vary sharply.