Experimental Study On Mechanical Properties Of High Performance Hybrid Fiber Concrete For Shaft Lining

In recent years,with the gradual depletion of shallow coal resources in China and the deepening of depth,engineering geological conditions are increasingly complex,shaft lining is vulnerable to mining and construction mechanical blasting shock wave problems in the initial stage of construction,which also has higher requirements for shaft lining material design.Therefore,through static and dynamic experiments and digital image correlation method,it is of great significance to explore the mechanical law of shaft lining concrete in the application process of deep coal mining in China.Therefore,in this paper,the mechanical properties of hybrid fiber concrete with different volume content and different aspect ratio under dynamic impact load were studied by combining experiment and DIC method.In this paper,the material and experimental design of concrete are introduced first,and then the statics equipment is used to test the mixed fiber concrete with different dosage and different aspect ratio,and the compressive strength and splitting tensile strength are obtained.The experimental results show that the compressive strength of concrete of each fiber group increases by 14.6%-25%compared with that of the reference group,and the splitting tensile strength of concrete of each fiber group increases by 13.8%-60.4%compared with that of the reference group.Secondly,in order to obtain the dynamic mechanical properties of hybrid fiber concrete,dynamic splitting test was carried out on the specimens using SHPB experimental system.The dynamic splitting strength,stress-strain curve,dynamic toughness and energy characteristics of hybrid fiber concrete with different content and different aspect ratio were compared and analyzed.The results show that the increase of pp volume content on dynamic splitting strength of concrete is in the order of 0.1%>0.05%>0.15%.Polypropylene length-diameter ratio of concrete dynamic splitting strength increased by 6000>3000>9000;In terms of the dynamic toughness,the increase of concrete of each fiber group is 27.8%～81.9%compared with that of single steel fiber group.The results show that appropriate polypropylene content and aspect ratio can effectively improve the reflected energy and reduce the absorbed energy of concrete specimens,and thus reduce the energy impact of concrete specimens under dynamic loading.Based on the digital image correlation method,the DIC strain cloud map,concrete crack failure mode and combined displacement are analyzed comprehensively.The results show that the DIC strain cloud pattern and failure crack of each group show two different variation processes.In terms of compound displacement,the compound displacement of each hybrid fiber group concrete is significantly reduced compared with that of reference group concrete and single steel fiber group concrete,and the maximum reduction range is 331.07 and 296.23%,respectively.The minimum compound displacement value is obtained when the volume content of polypropylene fiber is 0.1%and the aspect ratio is 6000,respectively.It provides a basis for the design of deep shaft lining.Figure 44 Table 13 Reference 89...