Research On Performance Of Rubber Powder Modified Concrete Used In High Speed Railway’s Bridge-subgrade Transition Section

High-speed railway has a higher regularity requirement for railway line compared withthe ordinary railway, the line of high-speed railway is composed of subgrade, bridge, tunnel,culvert and other structures of different rigidity, there is settlement difference at connectionsof these different structures caused by the rigidity difference, which will result in the rregular-ity of railway line, the settlement difference becomes more obvious at ridge-subgrade transiti-on section.In view of the problem that the rigidity of bridge-subgrade transition section in existinghigh-speed railway is relative big, settlement difference exists between transition section andsubgrade, which results in tensile failure of the transition section under train loads, an ideathat rubber concrete being used as the modified material of bridge-subgrade transition sectionis proposed. Through indoor test, physical and mechanical indexes of reference concrete andvarious types of rubber concrete are tested; the indexes include working performance, density,gas content, standard cubic compressive strength and prism compressive strength. Finite ele-ment software Midas/GTS is used to analyze the stress and settlement of bridge-subgrade tra-nsition section under static and dynamic load when the reference concrete, different kinds ofrubber concrete and the combination of reference concrete and rubber concrete is respectivelyused. The following conclusions are drawn:1. The working performance of concrete almost has no change after it is mixed with rub-ber powder; and when it is mixed with rubber powder, the density will decrease, while the airentraining content will increase, when the mixing proportion is5%,10%,15%and20%, theaverage value of density of three kinds of rubber concrete is respectively2.14g/cm3,2.07g/c-m3,1.97g/cm3and1.93g/cm3.2. Mixing rubber powder into reference concrete will reduce the strength of rubberconcrete, the larger amount the mixed rubber powder, the more the strength of rubberconcrete will decrease. As for28d cubic compressive strength, when the mixing proportion ofthree kinds of rubber concrete is5%,10%,15%and20%, the average decreasing value is17.85%,49.13%,82.78%and93.05%.3. Using Midas/GTS software to apply static and dynamic load on the bridge-subgradetransition section model, the results show that concentrated tensile zone appear in transitionsection, and the maximum tensile stress of transition section of the same material under dyna-mic load is20%higher than that under static load, by using rubber concrete of low strength asthe transition structural material, the stress value of tensile zone can be reduced. When respec-tively applying static and dynamic load under60%strength reduction ratio compared with re-ference concrete, the maximum tensile stress of tensile zone is respectively decreased by40.2- 6%and42.37%, the maximum tensile stress at the inverted trapezoidal structure of bridge-subgrade transition section can reduce the risk of broken of the structural concrete at tran-sition section under the effect of upper train load.4. As for bridge-subgrade transition section under the effect of load, when the referenceconcrete is used as the material of bridge-subgrade transition section, settlement curve at thecenter of structure presents a convex shape, and when the rubber concrete is used as the mate-rial of bridge-subgrade transition section, the settlement becomes larger. Combination of80mesh rubber concrete with60%strength reduction and reference concrete is selected to con-stitute the new type of bridge-subgrade transition section. Investigate the changing rule of str-ess and settlement of the new type of bridge-subgrade transition section when the filling thic-kness of rubber concrete is respectively1m,2m,3m and4m. The results show that, when therubber concrete is filled above the reference concrete, the maximum stress of bridge-subgradetransition section reduces significantly, the average reduction value is34.82%, while the rub-er concrete of different thickness is filled in bridge-subgrade transition section, the maximumtensile stress almost has no change. But with the increasing of the filling thickness, settlementcurve of transition section changes from convex state into linear, when the filling thickness ofrubber concrete is2~3m, the transition from transition section to subgrade body can realize asmooth state.