Steel Fiber Reinforced Concrete Application Research In The Tunnel Weak Positions Primary Support

Steel fiber reinforced concrete is a kind of new multi-phase composite material formed by adding ordinary steel to chaotic steel fibers.These chaotic steel fibers can effectively hinder the expansion of microcracks and the formation of macroscopic cracks in the concrete,which affects the concrete failure modes of steel fiber concrete and improve the tensile,bending,impact and anti-fatigue of concrete.Performance,with good ductility.The main work of this paper is as follows:1.According to the "Fiber Reinforced Concrete Test Method Standard"(CECS13-2009),the steel fiber concrete test block was made and the test scheme design and data analysis were carried out according to the orthogonal experiment method.The influence of different steel fiber volume fraction on the compressive strength of steel fiber reinforced concrete cubes was studied by 100 × 100 × 100 mm steel fiber concrete cube compression test and multiplied by strength scale conversion factor.The experimental data and analysis show that the addition of steel fiber does not have obvious regularity and influence on the axial compressive strength of concrete.When the content of steel fiber is small(volume fraction ?0.5%),the compressive strength of steel fiber reinforced concrete will be slightly lower than that of plain concrete compressive strength.However,the toughness of steel fiber reinforced concrete is not obvious,but the toughness is greatly improved,and the failure mode of concrete specimen is improved.This is due to the addition of steel fibers to improve the toughness of the pressure damage.From the destruction of the form point of view,steel fiber reinforced concrete under pressure.No obvious pieces or caving,still remain intact.3.Based on the 100 × 100 × 400 mm steel fiber concrete cube flexural strength test,the three-point loading method was used to study the effects of different steel fiber types(milling corrugated type,end hook type,shear straight type),concrete strength grade,steel Effect of Fiber Volume Ratio and Different Fine Aggregate and Water-cement Ratio on Flexural Strength of Steel Fiber Reinforced Concrete.The experimental data and analysis show that the flexural strength of the test piece is obviously enhanced with the increase of the volume fraction and the aspect ratio of the steel fiber,and the flexural strength is enhanced when the volume fraction of 1% ? 3% fiber is less than 1.5%.The failure of the test piece is that the steel fiber is pulled out,and the peeling of the aggregate during the destruction process is more than the concrete,the damage surface is more rough.This is mainly due to the failure of the surface after the cracks between the test piece and steel fiber through the cohesive force between the load,continue to load steel fiber and the bond between the substrate to reach the limit,the steel fiber gradually pulled out from the matrix until the cross-section fracture.At the same time can be seen,joined the steel fiber,the test piece of ductility has been improved.4.The effects of different steel fiber types(milling corrugated type,end hook type,shear straight type),steel fiber volume ratio and water to cement ratio were studied by 150 × 150 × 150 mm steel fiber concrete crack splitting tensile strength test.Effect on splitting tensile strength of steel fiber reinforced concrete.The tensile strength of steel fiber reinforced concrete increases with the increase of steel fiber volume ratio,and the reinforcement effect of the end steel fiber is better than that of the other three types.5.The influence of different steel fiber volume fraction on the impermeability grade of concrete was studied by making the steel fiber concrete impermeability test module with the upper opening diameter of 185 mm,the lower diameter of 175 mm and the height of 150 mm.6.Combining Fracture Mechanics with Layered Steel Fiber Concept,ABAQUS was used to simulate the axial compressive and three-point bending(bending)test of steel fiber reinforced concrete,and compared with the experimental data.7.The steel fiber reinforced concrete is applied to the initial support of the weak part of the Taishan Mountain tunnel,and its surrounding rock pressure,reinforced stress and vault subsidence are measured and compared with the measured mechanical properties of ordinary shotcrete,and the numerical simulation analysis.