Study On Surrounding Rock Stability And Construction Technology Of High Risk Karst Tunnel

With the continuous development of economy and construction technology and the protection of natural environment,tunnel is widely used in highway construction in China.Due to the vast territory of China,various geological conditions will be met in the process of tunnel construction,and karst geology is one of them.This kind of bad geological phenomenon of karst often brings safety risks to tunnel excavation and operation.In the construction of tunnels in karst areas,there are often threats of water gushing,mud gushing,surrounding rock deformation,instability and local collapse,block falling and rock falling in the excavation.Due to the complex structure and engineering characteristics of rock and soil,it is difficult to predict the karst disaster.An-ping tunnel in Qiu-zhu village,Wen-tang town is such a complex tunnel.Through collecting the surveying and mapping,exploration,test and other data of An-ping tunnel,theoretical calculation and numerical simulation methods are used to study the stability of surrounding rock during the excavation of karst tunnel.The main research results are as follows:(1)Through collecting the data of An-ping karst tunnel and investigation,the development of karst cave is analyzed.Through field investigation and laboratory test,the development and distribution characteristics of karst in this area are studied.It is known that the risk caused by karst is the main factor affecting the excavation of An-ping tunnel.On this basis,the analysis model of top hidden karst cave An-ping tunnel is established.(2)This paper analyzes all kinds of constitutive models applicable to the hidden karst cave and the surrounding rock stratum of the tunnel,analyzes the principles of each constitutive model from the theoretical and software levels respectively,and concludes that the Drucker Prager principle is more suitable for the study of the stability of the surrounding rock of the tunnel by the hidden karst cave,which is verified by the actual engineering case.(3)The finite element software ABAQUS CAE 2016 is used to simulate the construction process of excavation with CD method when An-ping tunnel passes through karst section.By comparing the influence of different size karst caves on the stress and displacement of the surrounding rock of the tunnel crown and the arch side,the change diagram of the stress field and displacement field of the surrounding rock of the tunnel caused by different size karst caves is drawn,the change rule of the surrounding rock of the tunnel caused by the karst caves in the karst area is analyzed,and the influence of the change of the size of karst caves and the distance between tunnels on the stability of the surrounding rock is obtained.