Study On The Invert Arch Deformation Mechanism And Remediation Measures Of Hong Shan Tunnel

With the rapid development of my country's railways,the construction scale and number of railway tunnels are also increasing.Because the geological environment of the tunnel is complex and changeable,the deformation of the bottom arch of the bottom structure occurs from time to time,which seriously affects the safety of railway operation and engineering construction.Therefore,it is important to carry out research on the deformation mechanism of the tunnel arch and its treatment technology.Theoretical significance and practical value of engineering.Based on the Beijing-Shenzhen High-speed Railway Hongshan Tunnel Uplift Control Project,through the on-site practice and data collection,a detailed analysis of the Hongshan Tunnel's base deformation law,causes,and conditions is carried out;conventional physical tests and triaxial compression tests are carried out on the tuffaceous sandstone to study The deterioration of the mechanical properties of the surrounding rock and the evolution law of deformation are analyzed;through the FLAC3 D numerical simulation software,the numerical analysis of the displacement changes of the tunnel arch structure and the base wall rock is carried out,and the vertical displacement changes of the arch before and after remediation are obtained.The displacement of the arch was monitored,and the monitoring data was compared with the numerical simulation results to obtain the following conclusions:(1)Four failure modes of invert uplift deformation: squeeze flow deformation,water deformation of expansive rock,flexural fold deformation,shear dislocation deformation;the mechanical action of invert is roughly divided into three categories: horizontal beam action,Pressure-bearing effect,reinforcement of weak surrounding rock;introduction of surrounding rock deterioration theory,found that the main reason for the decrease in strength of surrounding rock and long-term deformation of the tunnel is the decrease in shear strength(c,?).The strength degradation model can effectively show the actual strength and deformation of the surrounding rock.(2)The data obtained from the triaxial compression test of tuffaceous sandstone under different water content and different confining pressures found that as the water content of the specimen increases,the compressive strength of the specimen decreases significantly,and the strain continues to expand.In the compression test,the specimen was affected by water and showed obvious strain softening characteristics;as the moisture content changes from 0% to 10.8%,the shear strength cohesion gradually decreases,and the reduction ratio is 11%,22%,31%.(3)Numerical simulation results show that under the condition of the same thickness of the loose layer,the lower the cohesion of the surrounding rock,the greater the displacement of the basement uplift.When the cohesion is reduced by 10%,20%,and 30%,the maximum displacement of the monitoring point is 2mm,2.7mm,6.45 mm,respectively.Under the same deteriorating conditions of the surrounding rock,with the increase of the thickness of the loose layer at the bottom of the surrounding rock,the uplift displacement of the bottom structure gradually increases.The design of the anchor rod was optimized and numerical analysis was carried out.It was found that when the length of the anchor rod was 4m and the diameter was 28,the treatment effect of the bottom drum was the most significant.(4)The results of the monitoring data show that the vertical displacement values of each monitoring section have decreased to varying degrees,and the maximum displacements all appear in the middle of the tunnel invert,which has obvious "spatial effects".Compared with the related monitoring values before treatment,the displacement value has decreased,and the maximum displacement of the basement decreased by 5.3mm,from 9.6mm to 4.2mm,indicating that the renovation effect is significant.(5)The use of longitudinal beams,sleeve valve tubes,and pre-stressed anchor rods form a comprehensive treatment system that forms a common force system.Through on-site monitoring,it is found that the maximum displacement of the tunnel bottom structure has dropped from 6.3 mm to 2.47 mm,and the structure is under tension.Significant reduction,especially the state of surrounding rock at the midline of the invert has been improved.According to the comparison between the simulation results and the monitoring results,the vertical displacement simulation value and the monitoring value are not much different,the deformation law is basically the same,the treatment effect is significant,and the maximum displacement value is reduced by 5mm.