| The rapid development of the high-speed railway transportation industry has greatly promoted the construction of China's comprehensive transportation system,and accompanied by new problems.It is necessary to solve the problem how to effectively detect and rectify the defects of the tunnel and ensure the normal passage and safety of the train in the tunnel.Therefore,it is necessary to study the cavity phenomenon which exists widely in tunnel lining and has impact seriously on tunnel lining,so as to provide a reference for the comprehensive treatment of tunnel lining in the later period of tunnel detection.Based on the analysis of test data,it is concluded that there are different degrees of lining cavity in the construction and operation of railway tunnels,which is concentrated in the position of the tunnel arch and the side wall.The geometric characteristics of cavity defects in lining are analyzed statistically,including the geometric size of the cavity,longitudinal length of cavity,radial height of cavity,cavity angle range,cavity geometry and so on.According to the results of statistical analysis,orthogonal multi-factor data grouping is designed to analyze the stress sensitivity of lining.The damage stage method is introduced to evaluate the deterioration degree of cavity.Finally,the criterion for judging the degree of stress deterioration is put forward,which is influenced by the geometrical characteristics of the cavity.Some key conclusions are obtained as follows in this dissertation:(1)Through statistical analysis of tunnel detection data,it is concluded that the carbonization depth and strength of lining concrete in the detected section can reach the safety and qualified conditions of tunnel engineering.It shows that the carbonization depth and strength of lining concrete are not the primary factors in the analysis,so it is necessary to study the lining cavity.The existence of lining cavity weakens the stress relationship between lining and surrounding rock,and the bearing capacity of lining bracing structure is discontinuous,and the overall stability of tunnel bracing structure is affected by the initial constraint condition of the structure.(2)According to the tunnel detection of section A of a passenger dedicated line,according to the location of the cavity,the height of the cavity in the arch top is higher than that in the arch waist and side wall.The probability of cavity in the arch roof and shoulder position in lining is higher than that of arch waist,and the side wall is relatively less.A large number of defects are located in the arch of the tunnel,which mainly include lining cracks,lining cavity,lining leakage and so on.The relation between the thickness of the lining and the height of the cavity is corresponding,and the influence of the height of the cavity on the range of the cavity is smaller.It is considered that the relationship between the height of the cavity and the stress state of the lining structure is weaker.The variation coefficient is used to analyze the cumulative line length data of thecavity height of the section.The cavity height shows obvious normal distribution in the range from 8cm to 24 cm.The longitudinal length of the cavity is analyzed by statistical analysis.The common value of the longitudinal length of the cavity is 3 ~ 6 m.There is no obvious correlation between the longitudinal length of the tunnel lining and the height of the cavity in the corresponding position.(3)Through the orthogonal data experiment design method,the cavity geometry and the cavity range are divided into groups.It is concluded that the tunnel cavity angle range has the greatest influence on the longitudinal stress and the circumferential stress,and the influence of the cavity shape is second.However,when the cavity range is small and enpty,the circumferential stress is negative,and the stress state in the local range of the lining is close to the original state.When there is a cavity in the arch roof,the sensitivity of dynamic response under dynamic load corresponds to the position of the tunnel side wall > arch foot > arch shoulder > arch top.When the lining geometric feature size is small,the cavity geometry has a greater influence on the longitudinal stress.The geometric shape of the cavity is the most serious in the state of rectangular force deterioration,and the development trend of the rectangular cavity is larger than that of the triangular cavity,and the triangle is larger than the circular arc cavity.The maximum value of the 40 cm range of cavity height is 6.25,and the state of force deterioration increases sharply at this point.(4)The ABAQUS finite element mechanical model of tunnel roof with cavity is established.The surrounding rock is asymmetrical using the non related flow rule by using the Druker-Prager criterion.The lining is realized by the concrete damage plastic CDP model,and the material damage calculation parameters are assigned.The tunnel lining model is completed by the Mappde multi fineness mesh division.The calculation results show that the dynamic response of the lining is related to the lining position,and the dynamic response of the side wall position is the strongest.The trend of the stress change of the tunnel upline and the downline is basically the same.(5)The damage stage method of lining is used to evaluate the deterioration of cavity force,and the safety factor analysis is introduced.The cross section safety factor controlled by different cavity shape,cavity range and cavity height is calculated by the method of damage stage.When the height of the cavity is greater than 50 cm,the safety factor reaches 7.2,and the degree of the local force of the cavity reaches serious disadvantage,which indicates that the safety level of the tunnel is dangerous.Finally,a criterion is proposed to judge the dimension of cavity geometry features,which provides a reference for defining the cavity geometry characteristics of lining deterioration. |
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