Study On Defect Diagnosis And Classification Of High-speed Railway Tunnel Lining In Construction Period And Its Impact On Tunnel Structure Safety

Today's China not only has the longest high—speed rail operation mileage in the world,but also ranks first in the number of tunnel engineering in the world.On the other hand,the defects and diseases of tunnel lining become more and more prominent with the increase of tunnel engineering in China.At present,the research on the safety of tunnel lining at home and abroad mainly focuses on the treatment of tunnel lining diseases in operation,and the research on the influence of tunnel lining defects in construction on tunnel safety is insufficient.In this paper,through the on-site diagnosis of a large number of high-speed railway tunnel lining quality,the tunnel lining defects found in the diagnosis were statistically analyzed,and the distribution of defects was obtained.By analyzing the causes and distribution laws of the main defects,the corresponding defect prevention schemes are proposed,and the tunnels under different distribution patterns of different surrounding rock grades,different defect types and defects are calculated by numerical simulation calculation based on the “load-structure” model.The stress condition of the second lining structure was calculated.Based on the safety factor of the second lining structure,the evaluation system of the impact of the lining defects of the high-speed railway tunnel on the structural safety was established.Based on the “stratigraphic-structure” model,the stress of the tunnel lining under the typical defects of two sites was calculated.The evaluation system was applied to the evaluation of the actual defects in the field,and the reliability of the evaluation system was verified.The main research contents and results of this paper are as follows:(1)The diagnosis of a large number of high-speed railway tunnel lining defects is carried out,and the defects found in the test are statistically analyzed.It is known that among all the lining defects,the thickness of the second lining concrete is insufficient and the void behind the second lining is the largest,accounting for 47.7% and 36.5%.The defect distribution in the dome of the defect distribution is the most dense.(2)Explore the causes of major tunnel lining defects and suggest prevention.(3)Establish the finite element model of the tunnel with insufficient thickness of the second lining,calculate the internal force of the two linings under different parts and different defect grades and calculate the safety factor,and evaluate the safety of the tunnel defects accordingly.(4)Establish the finite element model of the tunnel under the condition of the second liner,and calculate the internal force of the second lining when different vacant widths and different vacancies are calculated,and calculate the safety factor.Based on this,the safety of the tunnel defects is evaluated.(5)Through the numerical simulation of the stress conditions of two typical defect tunnel linings on site,the safety factor of the two-liner structure is calculated,and the evaluation system is applied to the actual field,and its reliability is also verified.