| Karst landforms are widely distributed in southwest China.During the excavation and construction of tunnels and underground projects,bad geology such as broken surrounding rock and karst development are often encountered.Once geological disasters such as water inrush and mud inrush occur,it will cause adverse consequences such as property loss,delay of construction period,and even casualties,which will seriously restrict the progress and development of the tunnel construction industry.Therefore,it is of important scientific value and practical significance to study the disturbance influence of tunnel excavation on water diversion channel and the technology of water disaster prevention and control.Taking Liujia Tunnel of Wengma Railway in Guizhou Province as the research background,through on-site investigation and observation,theoretical research,numerical simulation analysis,summary of experience and practical engineering application,this paper deeply studies the development law of water diversion channel in the surrounding rock fracture zone of karst tunnel,establishes the water disaster prevention system of karst tunnel,and applies it to Liujia tunnel,and obtains some research results.The geological characteristics and development law of water diversion channel in karst tunnel are studied and analyzed systematically.Through the study of geological data and literature at home and abroad,the formation conditions and development characteristics of water diversion channels are summarized,and their types are mainly divided into two types: natural water diversion channels and man-made water diversion channels;the factors affecting the development of water diversion channels are mainly geological factors and engineering factors.Taking the actual project as the research object,the geological and engineering factors affecting the development of water diversion channel in Liujia tunnel are studied in detail.It is found that stratum lithology is an important condition for the formation of water diversion channel,and excavation construction is the key inducing factor for the development of water diversion channel.The disturbance range of surrounding rock caused by excavation is studied based on elastic-plastic theory.Based on the theory of loose zone,the range of plastic zone and the thickness of loose zone of typical section of tunnel are analyzed and calculated.There is a great relationship between the disturbance range of excavation and the grade of surrounding rock and the development of fissures.There is a certain risk in the construction.The excavation process of Liujia tunnel is simulated by COMSOL numerical calculation software,and the change rules of stress field,displacement field and plastic zone of surrounding rock around tunnel before and after excavation under different working conditions are studied.It is concluded that the disturbance during blasting excavation is the strongest,which is the most unfavorable working condition.Based on the study of the factors affecting the development of water diversion channel in karst tunnel,and combined with the successful cases of tunnel water disaster prevention at home and abroad,a karst tunnel water hazard prevention system is established,which integrates advanced detection,grouting treatment and monitoring and measurement.And carry on the engineering application research of the technical system.After grouting treatment,the tunnel passes through the risk section smoothly,and the established water disaster prevention and control system has achieved good application results in Liujia tunnel water disaster prevention and control work,and has high practicability.There are 39 pictures,19 tables and 62 references. |
