The Principles And Pragmatic Research Of Suspension Bridge Tunnel-Type Achorage In Montainouse Areas

With the development of economy and transportation business, long-span suspension bridge, as a more and more popular form, has been applied in civil construction in mountainous area. Compared with gravity-type anchorage, tunnel-type anchorage is adopted in long-span suspension construction on the basis of the following advantages: less works quantity, more cost-effective, better utilization of the geological conditions of the anchorage zone and less disturbance of environment. However, because of the non-systematical design standards, codes, uncertain parameters for tunnel-type anchorage and special requirements for design in mountainous area, it becomes highly crucial to calculate and evaluate the rock displacement, stress and plastic deformation scope around the anchorage and stable loaded condition.This thesis gives a thorough introduction of main structural form of tunnel-type anchorage, the historical and present status of its application around the world, relative theory of its mechanism of action and stability and basic function of ABAQUS and its constitutive relations and solution procedure through literature review, and makes a deep research on the damage mode of surrounding rock in anchorage area to establish a stress function method for stress field at initial site.Finally, based on the Puli suspension bridge project in Puxuan Express Way in Yunnan province, anchorage structure system deformation surrounding rock, stress data under designed load through data simulation analysis on working procedure like excavation and shoring of tunnel-type anchorage cave, backfill of anchor, etc will be analyzed. Upon this we get following conclusions about the stability of surrounding rock:(1)Main stress of the rock: the largest tensile stress appears at the surroundings of the joint of back anchor house rock and the anchorage, while the smallest appears at the top of back end of the back anchor house. During the process of raising the main cable power from 100% to 750%, the tensile stress changes a lot and the compressive stress changes less.The change regularity of rock shear stress around the anchor is almost the same:The shear stress gradually decreases from the largest near the back anchor towards the front part.(2) Location of rock plastic deformation: under the 500% of designed cable stress, partial plastic deformation areas occurs at both sides and bottom end of the rock's back anchor house;under the 750% of designed cable stress, the plastic deformation areas at the rock's back anchor house goes through the tunnel and no plastic deformation occurs at the surrounding rock around the anchorage.From above we can conclude that under 750% of designed cable stress, the movement of rock and the stress are all within control, the plastic deformation scope of rock is limited and tunnel-type anchorage is stable and safe. The design scheme meets the design requirements with >6 safety degree.Analysis based on the evaluation of the tunnel-type anchorage and rock stability of Puli suspension bridge project is supposed to provide a reference to the design and construction of projects of the similar type.