The Interaction Analysis And Application Of Composite Support And Surrounding Rock Under High Geo-stress Condition In Highway Tunnels

Highway tunnel excavation and support processes often encountered inlarge deformation, rock outburst and even roof collapse and other problems,supporting structure in high stress conditions often under great supportingpressure, therefore, the interaction between supporting structure andsurrounding rock needs in-depth study, optimization analysis supportingstructure of the design parameters and timing have great significance to theimproving safety and economy of engineering.Surrounding rock bolting as a support method with the traditional typesof reinforcement technology’s main advantage is: As the essence of boltmechanical mechanism is transformed and used the mechanical properties ofrock itself, transform the original outside rock to the part self-bearing body,ensure the stability and security of the entire project; improving the quality ofthe surrounding environment and engineering; saving engineering materialsand shorten the construction period.Although the application of bolting technology maturing, the bolt actionmechanism study are still at an exploratory stage, the key method to identifythe bolting parameters at this stage is engineering analogy method, while thelack of practical theoretical analysis method often leads to unreasonabledesign. Some projects support intensity is too large, resulting in wastage;others strength is too low, bring construction security risks. However, fieldtest time-consuming, laborious, and subject to the venue, geology andconstruction constraints, resulting in test results is not representative, it isdifficult to promote a different location in tunnels. With the rapiddevelopment of computer technology in recent years, numerical simulationmethod has been widely used in the tunnel bolt analysis, numerical simulationbased on research needs, to change the model size, material, nature and effect of factors, by numerical processing and display bolt and surrounding rockstress and deformation. The numerical simulation results combined withexperimental data, provide a basis for the anchor design.Using the Hou-Yun-Tai-Shan highway tunnel engineering atLianyungang as the background, The the numerical simulation of excavationand support processes of multi-cases tunnel is made in this paper.Contentsand resulting achievement of this paper are as follow:(1)Based on the factors affecting the stability of tunnel surrounding rockand the instability failure mode, the mechanism of the the fully grouted rockbolt anchored in the mass,reveal distribution of the stress is studied. using theFinite Element Software,the paper reveals the distribution of the stress alongthe length of the bolt under different conditions of pullout load、rock masslevel、bolt diameter and bolt length。(2)By changing the parameters of the bolt length, bolt interval and boltdiameter,the simulation analysis of the characteristics of the tunneldeformation are taken under different conditions of rock mass level and depthof tunnel.According to the design information and rock parameters of Hou-Yun-Tai-Shan tunnel, the simulation analysis of different lengths, differentintervals and different diameters of bolt are taken. The resultS show that theimpact on surrounding rock displacement of the three factors can be sorted as:bolt length>bolt interval>bolt diameter.(3)Simulate the time effect of the concrete lining support of full facemethod, three-step cut method and twin-side heading method,analysis thedistance changes between and under different excavation methods for thestability of the tunnel excavation. As the distance between concrete lining andworking face increased gradually, the tunnel crown settlement values aregradually increased, shear stress, first principal stress, the second principalstress, the third principal stress is also increased.Different methods ofexcavation affect the tunnel crown settlement greatly, twin-side headingmethod reduce effectively of the tunnel vault settlement. (4)Proposed the method of the stability analysis in bolt-support tunnel,the stability analysis of the Hou-Yun-Tai-Shan highway tunnel is made.Theresults of simulation indicate that the tunnel surrounding rock is stable and thestructural safety meets the design requirement.