Detection Of Sudden Mud And Water Gushing In Jiudingshan Tunnel And Study On Disaster Mechanism

With the increasing number of tunnel projects,there are more complicated geological situations in construction,and with the increasing possibility of geological structures such as water inrush and mud gushing,the construction safety of tunnels is strictly controlled.In order to ensure the safe construction of the tunnel,it is particularly important to predict the advanced geology of the tunnel,so it has become an indispensable part in every stage before,during and after the tunnel construction,and the analysis of water inrush and mud inrush disaster has also become an important link of disaster prevention and control.In this paper,based on Jiudingshan Tunnel in the high-speed test section of Chu-Da Line,the principles of geological radar,infrared water detection,borehole photography,transient electromagnetic and other methods are summarized.Through in-depth study on the prediction principle and application technology of the above methods,effective measures are also adopted to analyze the water and mud inrush sections in Jiudingshan Tunnel,and the catastrophic mechanism of water and mud inrush in the structure is summarized and analyzed.The main research contents and results of this paper are summarized as follows:(1)This paper summarizes the basic principles of geological radar,borehole camera and transient electromagnetic technology,analyzes the applicability and pertinence of several means,and effectively combines various means to carry out systematic forward simulation and imaging research on fault fracture zone and karst cave at different distances and sizes,so as to realize accurate and rapid advance prediction of geological structure in front of tunnel face.(2)Based on the disaster monitoring of mud inrush and water gushing section and the geological structure of the proposed tunnel,the law of mud inrush and water gushing is summarized:(1)Time law: intermittent water gushing,the time interval is generally 11-14 hours,with regular periodicity;(2)Increasing flow rate: from the first to the fourth,the seventh and eighth water inflow statistics are increasing every time;(3)Weather impact: according to the statistical data of water flow and climate;In rainstorm weather,the water flow increases,and it can be confirmed that there is surface water supply;(4)The sediments are consistent: after each water gushing,the sediments in the tunnel are fine sand such as granite,hornblende and Shi Ying,and there is nothing mixed with elliptical SIO2 colloid and kaolin;(5)Short water gushing time: the water gushing time basically ends in 5-10 minutes,and the eighth time lasts for 20 minutes.(3)According to the detection data and disaster monitoring data,the causes of water gushing and mud bursting in the fully weathered granite tunnel are summarized and analyzed: during tunnel excavation,the fully weathered granite above is disturbed by excavation,loosened and cracked,and connected with the limestone fissure water above.Under the softening action of water,the rock mass disintegrates and destroys,resulting in the failure of the initial support,the tunnel collapses,and then the limestone fissure water is replenished.The rock mass around the collapsed body continues to soften and disintegrate under the soaking of water,and the collapse range is further expanded.When the landslide area develops to the upper mixed rock stratum,the mixed rock stratum is relatively complete and hard,so it will not continue to develop.At the same time,the lower breach is blocked by the landslide body,which prevents the water inrush and mud gushing in the tunnel.(4)According to the example of Jiudingshan tunnel project,a set of prevention and treatment measures for mud inrush and water gushing in karst tunnel are summarized: "exploration"-multi-means comprehensive advanced detection;"Cut off"-backfill the sinkholes and deep pits on the surface of the top of the cave,plug the cracks and cut off the surface water supply;"Discharge"-PRD-180 CBR multifunctional drilling rig is adopted for the right arch waist,and a discharge pipe with an inclination angle of 35,a depth of 45 m and a diameter of 108 mm is installed;"Curtain" —The full-section curtain grouting is carried out by using the integrated drilling and grouting technology of multifunctional drilling rig,so that the tunnel can safely pass through karst water-rich areas.