| In deep alluvium,Freezing sinking shaft method have become one of the most effective wellbore construction methods.As the thickness of the alluvium increases,in order to withstand strong external loads,the shaft lining thickness and concrete strength grade also increase.Due to the high hydration heat and large temperature difference during construction,the concrete cracks in the shaft lining also increase.When the frozen wall melts,the leakage of the shaft lining is serious,which has become a major engineering technical problem in the freezing sinking shaft method.In response to this technical problem,this paper carried out the preparation,performance test and microscopic analysis of fiber hybrid and micro-expansion high performance shaft lining concrete.Firstly,the paper first carried out the trial test of fiber concrete and expansive concrete.Through the four-factor and three-level orthogonal test,the optimum mixing ratio of fiber hybrid and micro-expansion high-performance concrete is water:cement:NF-F:expansion agent:polyvinyl alcohol fiber:imitation steel fiber:sand:Stone=166.112:410:130:32.8:1.092:5:615.992:1095.096.Then,the compressive strength,tensile strength,impermeability,limiting expansion ratio,expansion self-stress,early crack resistance,temperature self-stress and other related properties and comparative tests of fiber hybrid and micro-expansive high performance shaft lining concrete were carried out.The X-ray diffraction and scanning electron microscopic analysis of the shaft lining concrete under different curing status were carried out,and the main results were obtained:(1)The results of experimental studies indicate that the hybrid fibers can produce positive effects,and the compressive and splitting tensile strength of the hybrid fibers are better than that of the single fibre concrete.Under the condition of limited curing,the compressive strength of fiber hybrid and micro-expansive shaft lining concrete is increased by 9%,and the splitting tensile strength is increased by 28.2%,which can meet the requirements of compression and splitting tensile strength of shaft lining concrete drilled by freezing method.(2)Under the condition of limited curing,the impermeability of single-mixed hybrid fiber concrete decreased by 41.896%,and the impermeability of concrete with single-expansion expander increased by 94.822%.The combination of fiber hybrid and expansion agent improved the impermeability of shaft lining concrete by 86.954%,so this new composite shaft material has superior impermeability.(3)Fiber hybrid and expansive agent composite concrete has the advantages of moderate expansion stress and small drop of expansive stress.The addition of hybrid fibers and expansive agent to the concrete in the shaft lining avoids the occurrence of early cracking.(4)The average temperature expansion coefficient of the new concrete material with fiber mixing and expansive agent is only 5.722x10-6/,which is 43.099%lower than that of the reference group.The temperature self-stress measurements also show that the new concrete with fiber mixtures and expansive admixtures can reduce the temperature self-stress by 48.12%.(5)X-ray diffraction analysis and scanning electron microscopy analysis of concrete under different curing status show that Ca(OH)2 crystal is the main expansion source of expansive concrete.Fiber hybrids does not have much influence on the Ca(OH)2 diffraction peak,and the dosage of expansive agent affects the Ca(OH)2 crystal content;At the same time,limiting the curing state will restrict the growth of Ca(OH)2 crystals to a certain extent,which is conducive to the formation of crystallization pressure.Therefore,the Fiber hybrid and micro-expansive composite shaft lining concrete is used to improve the internal pore structure of the concrete and restrict the development of micro-cracks,thereby reducing the water seepage channel and improving the impermeability of the shaft lining concrete.Figure 34 Table 26 Reference 90... |
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