| Research background: located in Bijie City,Guizhou Province generous tunnel,the full length of 7130 m,is the new passenger line of Chengdu to Guiyang Leshan line to Guiyang section "four bridge thirteen tunnel" heavy and difficult project.The starting tunnels beneath the existing high embankment Hangrui highway(through start mileage D1K392+270 ~ D1K392+380).Highway tunnel vault only 26 m buried depth;embankment slope protection for all the body empty,big gap surface dry code stone,the lower part of the main body is the upper embankment dissolution karstified limestone,as the backfill clay and gravel breccia-poor stability;high speed highway traffic flow and in high embankment settlement risk;cross effect of tunnel pile No.D1K392+265 ~ D1K392+380,length 115m(corresponding to the expressway mileage is about K1741+700-+750)-long mileage.The main contents of the study are as following: to ensure the safe operation of the highway under the tunnel and the safe and smooth development of the tunnel.The significance of the study: to ensure the safety of the tunnel under the smooth safe operation of Expressway in construction process and under highway tunnel construction;accumulation of passing existing in the coexistence of a variety of adverse factors under the condition of the engineering experience.The main research contents: settlement control measures and the settlement of the underpass highway pavement;tunnel support system and the supporting measures of tunnel excavation blasting;control measures.Methods and results: after repeated trial and field survey,decided to follow the original design in the lining type V C,using three step excavation method reserved core soil method;also decided to adopt 80 m with 108 double long pipe shed advanced support and to control the highway tunnel settlement of embankment slope protection and reinforcement 76 steel tube pile grouting,combined with the surface of the highway subsidence monitoring and the settlement of the convergence monitoring measurement and other technical means to ensure the normal operation of the expressway,and the use of controlled blasting and supporting measures to strengthen control of tunnel surrounding rock convergence and vault settlement with HW175 steel frame steel frame to replace the I20 B.The precisely positioning of double-layer overlong pipe shielding of sizes ?108 during construction ensures the excavation safety and normal operation of expressway later on.Radial direction grouting from the surface of embankment of expressway places a solid foundation to prevent road surface from uneven settlement.Moreover,settlement monitoring of ground surface and tunnel inside survey and monitoring provide fundamentally data support for tunnel holes excavation.Through above measures Da'fang tunnel of Chengdu-Guiyang high-speed railway safely and successfully under-crossed Hangzhou-Ruijin expressway.Overlong pipe shielding,ground surface grouting,surface monitoring provides significant references and support especially in Yunan & Guizhou area characterized geological conditions. |
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