| The operation tunnels are critical infrastructure on the railway lines, and the technology of the operating tunnel directly impacts the traffic safety. Both defects caused by deficiencies, such as construction quality and construction error, and diseases due to the long-term operation can reduce the safety stock of the lining bearing capacity, shorten its residual life, and are serious threat to the use of the tunnel. Currently, there is lack of research on the operating tunnel technology, especially the assessment of residual life of the tunnel lining. In this paper, the main technical parameters which affect the lining operation are obtained by effective investigation and detection, and reasonable model is built to assess the residual life of the lining structure. This will have important reference value for the repair and maintenance of the operating tunnel and the design of the new tunnel engineering.Study on calculation method of structure safety of operating railway liningThe factors which affect the safety of the tunnel lining are deeply studied, such as the tunnel load types and values, the lining structure dimensions and material properties, structural calculation model, and so on. Then the calculation method based on the actual technical state of the operating tunnel is put forward, and its legitimacy is verified by a numerical example. The calculation results obtained by this method compared with the results by the proposed tunnel project are more targeted, and more similar to the actual situation of the operating tunnel.Study on safety evaluation of operating railway tunnelsReferring to the research results from home and abroad, as well as adopting the research methods integrating theory with practice, the current situation of the operation and management on the railway tunnels was analysed, and seven main parameters was summarized. The parameters were graduated by correspondence indexes. And then the model and method of indexes and parameters which were combined in qualitative and quantitative was set up. The model of safety evaluation of the operation railway tunnels was based on expression and indication for safety information of operation tunnel. In order to obtain more reasonable assessment results, all the indexes are divided into three levels, and the three-level fuzzy synthetic evaluation method for the safety of the operating railway tunnel is proposed in accordance with the fuzzy mathematics theory. Furthermore, the evaluation process by means of this method is illustrated by an engineering example. The results show that the evaluation results obtained by means of this method is correspondent with the results by the evaluation method based on empirical judgments, which proves that this evaluation method is feasible and reasonable.Study on assessment model of residual life of lining structureIn this paper, the integral lining of the railway tunnel is chosen as the study object. The factors which affect the residual life of the tunnel lining are studied, such as the contact state between the lining and the surrounding rock, deterioration state of the surrounding rock, the lining dehiscence, leakage water and frost damage, deterioration of the lining materials, computational model and so on, and the assessment model of the residual life of lining structure is established according to the load-structural model. In this assessment model, the lining concrete strength is chosen as variable parameter, and the lining structural internal force is calculated combined with the current status of the lining. Then the lining safety factors of each cross-section are calculated by means of the plastic stage design method. Besides, the damage of three cross-sections is considered as the standards of the end of the residual life of the lining structure. Finally, the residual life of the lining is determined. The assessment model makes good use of the bearing capacity of the tunnel lining, and better reflect the actual situation of the operating tunnel. A numerical example shows that the lining diseases will greatly reduce the safety stock of the lining carrying capacity and reduce residual life of the lining.The evaluation process of the residual life of the lining structure is shown, and the acquisition method of the main parameters of the assessment model is studied. The geometric dimensions of lining structure and the contact state between the lining and the surrounding rock can be obtained by tunnel clearance measurement combined with ground penetrating radar (GPR). Lining concrete material properties, especially concrete strength can be obtained through a large number of laboratory tests and nondestructive tests. The state of the surrounding rock including the material properties of the surrounding rock and the backfill behind the lining, the surrounding rock loose height (rock pressure) detection, can be obtained by laboratory tests, in situ testing and GPR detection. Lining structure breakage, leakage water and frost damage can be gained by field investigations and observations, and the scope and development of the lining crack, water pressure, the surrounding rock frost heaving force should be considered when the lining diseases are more serious.Simulation test of GPR detection of railway lining state The integral lining and composite lining which are the common-mode on single-track railway are chosen to be studied, and lining specimen and the model of the tunnel bottom are built, where the type of working conditions including the empty behind the lining, uncompacted backfill are set. Then GPR detection simulation test is performed. The test results show that the GPR detection can reflect the types of working conditions pre-set in the test, and identify dielectric layers in the model, whose thickness can be quantitative analysed. GPR detection is an effective way to detect geometric dimensions of lining structure and the contact state between lining and surrounding rock. |
