| Ground fissure is a typical geological disaster and the hidden ground fissure is one of the ground fissureis geohazards. Usually the hidden ground fissure is neglected because of the covering strata above it. In recent years, the damage of many roads, bridges and houses caused by the movement of hidden ground fissure is so serious that more and more researches about hidden ground fissure have been carried out to prevent and mitigate this disasterIn China, the large-scale construction of high-speed railway is facing the threat of ground fissure geohazards. So far, 21 ground fissures have been found along Datong-Xi’an Passenger Dedicated Lines(High Speed Rail line)which passes Yuncheng, Linfen and Taiyuan basins. Theseground fissures intersect theDa-xi High Speed Rail line with 36 places, among which 9 are exposed or uncovered ground fissure, 27 are unexposed hidden ground fissure. Those unexposed hidden ground fissure accounts for 75% of the total number of ground fissures which may bring serious potential hazard to the safe operation of the Da-xi High Speed Railway. Meanwhile, few researches about the influence to high-speed railway Bridges caused by hidden ground fissure have been implemented both at home and abroad. Therefore, there is a great theoretical significance and engineering practical value on the studyof influence of hidden ground fissure on high-speed railway Bridge.Under the background of Datong-Xi’an high speed railway crossing the ground fissure, several researches have been developed. Firstly, based on field survey, special investigation and statistical analysis, the basic characteristics and activity of hidden ground fissure, developed along the Datong-Xi’an high speed rail in Shanxi province region, have been investigated, and evaluated the engineering design at several certain position. Then, adopted the regulations method, investigation method, mechanical analysis method and numerical simulation method, and determined the wide of the region of influence of typical group fissure is 25 m and 15 m in hanging wall and footwall, separately. Based on these results, comprehensively analyzed the failure model of soil-pile foundation-simply supported beam bridge from more than four inspects, including displacement, stress, strain and structural internal force. In the numerical calculation, Midas-GTS finite element analysis method have been adopted, and the several span length(24m, 32 m, and40m) and crossing angle(45°, 60° and 90°) have been considered. Then associated with the activity of hidden ground fissure, crossing angle and span length, explored the deformation and failure model of simply supported beam bridge,. Namely, with the crossing angle is decreasing(90°, 60° and 45°), the model of stress is the whole tension, local tension and whole tension-torsion. The box beam is in the state of compression in the hanging wall, while another section is in the state of tension in the under wall. The strain of box beam has the characteristic of dissymmetry, and the tension strain and compression strain is decreasing, while the span length is increasing. Finally, associated the different crossing angle between hidden ground fissure and bridge, determined the optimal span length. Namely, if the crossing angle is 90°, the span length is 32 m, or else the span length is 40 m. According to the safety and construction cost, preventive countermeasures of high speed rail bridge against the hidden ground fissure was put forward finally. |
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