Test Study And Finite Element Analysis Of The Work Mechanism Of The Rock Anti-float Anchor

With the rapid development of the city basic construction,the available ground of the city becoming more and more lacking.And then there are a lot of underground garages,subsidence plazas, underground markets,subways,basements which are expanding to multilayer and exceeding deep and other underground buildings appeared. However there is a large number of groundwater exist in the hole of the soil and the cranny of the rock.The effect which the groundwater have on the underground building couldn't be ignored.and the project accident was brought about by the groundwater flotage also often occoured.So the engineering field starting make a point of dealing with the problem of the groundwater flotage too.The paper mostly studies the rock anti-float anchor which is specially efficiency to deal with the groundwater flotage which is on the rock groundwork.The following studies have been done in this thesis,including:1 .Through the analysis of the groundwater,the paper educe the effect factors of the groundwater flotage.Which include the keeping state of the groundwater,the seepage character,the position of the underground structure,the basement additional trough and the resistance of the basement outside wall.And discussed the calculation of the float force about the multilayer groundwater .2.Through the pull force destructive tests about the three anti-floating anchors which the strain gauges were sticked on and were in the moderately weathered granite,educe the following conclusions.When the anti-floating anchor which is in the moderately weathered rock is pulled,the load is not equally distributed along the anchor, which is gradually decreasing from the top to the bottom of anchor,and at the definite extent of the anchor bottom there almost is not force.The distortion of the anchor is developmental from the elastic stage to the plastic stage.As the load increasing the plastic zone is moving down.The ultimate withdrawal resistance of the anti-float anchor what is in the moderately weathered rock was given by the tests,and gave the average ultimate banding power between the moderately weathered granite and the anchor is 439 kPa.By contrasting found that the banding power between the rock and the anchor is defferent in defferent region.3. Through making use of the finite element analysis software ANSYS analysed the anti-float anchor which had defferent length and was in the rock that owned defferent feature respectively,and analysed the group anchor effect.Give the following conclusion.The anchoring length of the anchor is longer the displacement is larger when reaching the ultimate pull-out resistance.So the rock anti-float anchor shoud have an economy and reasonable length.exceeds the length if want to make full use of its side frictional resistance will make a larger displacement,that is unfavourable to the stabilization of the structure.The feature of the rock has a larger effect on the bearing capacity of the anti-float anchor.The group anchor effect makes the ultimate pull-out resistance of the single anchor among the anchor group decrease to about 0.6 times of ultimate pull-out resistance of the single anchor.So in order to ensure the anti-float anchor has enough assurance coefficient.the design value of the pull-out resistance of the anchor shoud be reduced bases on the test of the single anchor when the anti-float anchor being designed.