| Tunnel structure, as a kind of underground structure engineering, because of its complexenvironment, is affected by many factors, these factors include: geological condition,hydrological condition, design and construction, many diseases appear during the operationperiod after the completion of the construction of tunnel, these diseases threaten thesupporting and security of tunnel structure, based on two main diseases in Pandaoling tunnel,namely water seepage and leakage of lining and lining crack, the following research work arecarried out:(1) According to the current situation of tunnel diseases, the types of s water seepage andleakage of lining and lining crack are summarized, as well as the harm to the tunnel structure,and further analysis on the causes of water seepage and leakage and crack of lining isconducted.(2)Because that a large amount of groundwater exist in Pandaoling tunnel, and themineralization degree of groundwater is high, the change of chemical ion content in water isabnormal, chemical analysis of9typical water leakage points in Pandaoling tunnel isconducted, the results of these9points can be divided into5types, and by the comparisonwith the ion species, content and degree of mineralization of the same pile numbers at theconstruction phase in1990, it is found that the average ion content in groundwater is basicallyat the same level, the change is not obvious. But according to the normalization of parameterslike major ions and degree of mineralization of the9testing points of pile number, it is foundthat HCO3-and SO42-in underground water has strong variability, HCO3-and SO42-are themain ions in sulphate erosion and dissolved erosion of lining erosion, which illustrates thatthe erosion types of lining structure of Pandaoling tunnel are mainly sulphate erosion anddissolved erosion. Because of the high content of sulfate ion in Pandaoling tunnel, it results inthe degradation of the performance of underground concrete structure, and the degree ofdegradation has a direct relation to the degree of erosion damageD, which causes a decline inmechanical properties of concrete lining.(3) Cracks appear in a number of linings in Pandaoling tunnel, two typical sections intwo tunnels with serious diseases are selected to install the instruments and observe, theinstalled instruments include multi-point displacement meter, surface crack lining gauge andembedded strain gauge, crack development in a year is observed, and the influencing factorsof the development of cracks are studied. Starting from the angle of fracture mechanics, theresults expression of stress intensity factor of lining crack changing with different crack depthis calculated, and finite element analysis software ABAQUS is used to establish the numericalmodel of cracks, the propagation of cracks is simulated to calculate the stress intensity factor under different crack depth, which is compared with the theoretical value of intensity factor infracture mechanics, and the influence of different crack depth is studied.(4)Finally, starting from the causes of tunnel diseases, based on the hydrogeologicalcharacteristics of tunnel location, comprehensively and systemically investigate the way ofwater seepage and leakage, the amount of leaking water and water properties of all linings,and controlling measures for water seepage and leakage are proposed specifically, as for thelining crack, stating from the characteristics of crack, according to the different width andlength of cracks, different materials are used to treat the inclined and circumferential crack, allof which provide help and reference for the future treatment on tunnel diseases. |
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