Research On Dislocation Response And Fault Resistance Performance Of Tunnel Structures Across Active Faults Considering Dislocation Modes

Active faults of various scales are widely distributed in western my of country.With the rapid development of transportation and water conservancy construction in western mountainous areas,a large number of long-term linear projects under construction or planned construction often cannot avoid active faults.There are more and more cases of tunnel projects crossing active faults.more.Fault dislocation can easily lead to serious damage or even collapse of the tunnel structure,endangering the structural safety and causing heavy economic losses.Enhancing the fault-resistance performance of the tunnel support structure system has become an important technical problem to be solved urgently in the engineering of tunnels crossing active faults.At present,for the fault displacement model of tunnel faults,most of the existing studies adopt centralized faults,ignoring the influence of the fault displacement distribution mode.In addition,studies on the fault resistance of tunnels crossing active faults focus on the lining segment joints and shock-absorbing layers,and less consideration is given to improving the fault resistance of the lining itself.Based on this,this paper relies on a tunnel project crossing active faults in Yunnan Geqiao Expressway,and according to the fault-resistant fortification and support structure system adopted in the project,a 1:25 scale fault dislocation model test of the tunnel structure across faults is carried out,and the tunnel is established.The numerical calculation model of the fault fault response is used to compare and analyze the structural fault dynamic response and damage characteristics of the model test and numerical simulation.On this basis,considering the centralized and distributed displacement displacement modes,the influence of displacement displacement modes on the dynamic response of the tunnel structure is discussed.Fiber-reinforced engineering cementitious composites(ECC)is further introduced to construct a new material combined support structure,and the fault resistance performance and parameter sensitivity of the new material combined support structure are studied.The main research contents and conclusions are as follows:(1)Based on the support structure type of the tunnel engineering crossing the active fault section,the dislocation response model test and numerical simulation were carried out.The results show that the dislocation damage of the tunnel support structure is mainly characterized by dislocation,cracking and local spalling.Structural damage is concentrated in the fault fracture(2)zone and hanging wall area near the dislocation plane,located in the inverted arch,wall foot and side wall.Under each fault dislocation,the structural damage is limited to a certain range,and there is no overall collapse damage,and the supporting structure has certain fault-resistant applicability.The displacement response of the lining structure,structural damage location and failure characteristics obtained by the numerical simulation are basically consistent with the model test,and the numerical simulation can better restore the fault dislocation response characteristics of the tunnel structure.(3)Using centralized displacement displacement and linear and "S" type two typical distributed displacement displacement methods,a numerical model of tunnel fault displacement response considering fault displacement model is established,and the influence of displacement displacement mode on tunnel structure is studied.Effects of misaligned responses.The results show that: under the centralized displacement mode,the limit dislocation amount of tunnel structural dislocation damage is about 280 mm,while the limit dislocation amount of the distributed displacement mode reaches more than 1000 mm,and the concentrated dislocation is more likely to cause structural fault damage.Compared with distributed dislocation,the damage of lining under centralized dislocation is more concentrated,and the development degree of damage is obviously higher than that of distributed dislocation.The stress response and damage and failure characteristics of the lining under the linear and "S" dislocation displacement modes in the distributed dislocation are roughly the same,and there is no big difference.(4)Combined with the model test and numerical simulation results,a reinforced ECC(R/ECC)lining is introduced in the expected dislocation lining segment,and a calculation model for the dislocation response of the new material composite support structure under the distributed dislocation load mode is established.Analysis of fault-resistance performance of material combination support structure.Compared with the traditional reinforced concrete(RC)lining,the R/ECC lining significantly improves the applicable deformation capacity of the tunnel.Under the same dislocation displacement conditions,the RC lining in the fault zone area was severely damaged in a large area,while the R/ECC lining was only severely damaged locally.Compared with RC lining,the distribution range of tension and compression damage of ECC lining is reduced by 6%～35% and 17%～49%,respectively,and the proportion of serious tension and compression damage is reduced by 30%～45% and 7%,respectively.～44% range.Combining the damage degree of the lining and comparing the stress levels of the two structures,it can be seen that the stress of the RC lining is already in the post-peak residual stress state.The R/ECC combined support structure shows better fault resistance performance.(5)Considering different fault surrounding rock conditions and fault types,the fault-resistance applicability of ECC composite support structure is preliminarily discussed.The results show that under distributed dislocations,keeping the quality of the surrounding rock in the fault zone unchanged and increasing the strength of the upper and lower rock masses will strengthen the constraint of the rock mass on the structure,which will increase the deformation difference of the structure under the same dislocation,resulting in a The stress response of the structure at the junction of the pan rock mass and the fault fracture zone is more severe and the damage is more serious.Keeping the quality of the upper and lower wall rock mass constant,the stress response and damage degree of the regional structure of the fault zone are reduced with the decrease of the strength of the surrounding rock in the fault fracture zone.The damage characteristics of structures under normal fault dislocation are mainly tensile damage,while reverse fault dislocation is characterized by more serious compressive damage.Compared with reverse fault dislocation,the structural damage distribution and damage degree of normal fault dislocation under the same dislocation are larger,and the structural damage is more serious.