Study On The Fire-Resistent Capability Of Habrid Fiber Concrete And Its Application In Tunnel Engineering

Hybrid fiber foncrete is a new field of fiber foncrete. It can buildup the strength of concrete and ameliorate the property of concrete through adopting complex overlapped mode. Come to light, no matter what high property concrete, just the same normal standard concrete, they have the same shortcoming, namely no fire-resistance. But the hybrid fiber concrete can ameliorate the fire-resistance of high property concrete through immingling the low melt point fiber and the high melt point fiber. So it has very important practical significance to study the fire-resistance of hybrid fiber concrete.Combining the guideline of fire protection design in tunnel structure, this paper adopts hybrid fiber concrete in tunnel structure to ameliorate the fire-resistant capability of concrete. Allow for economy and properties, this paper selects steel fiber and propylene fiber to jumble at small addition (by volume), and carry through following studies:1. The fire testing, surveying the inner temperature of different addition specimens.2. Mechanics properties experiments of the specimens before the fire testing and after fire testing include cubic strength of concrete, split tensile strength of concrete and loss of weight.3. Simulating fire of tunnel engineering with ANSYS analysis soft, the tunnel lining adopts reinforced concrete and five kinds of hybrid fiber concrete, analyzing inner temperature field distribution and temperature stress distribution.Through combining tests and computer simulate, this paper gained the following conclusion:1. The inner temperature conduction of concrete has visible melioration with the increase of propylene fiber. The inner calefactive speed and lapse rate are least when the propylene fiber addition is about 2.0kg/m~3.2. The hybrid fiber can enhance the cubic strength and split tensile strength of concrete after fire-testing, it can minish the loss of weight when the concrete happened blowout. The hybrid fiber concrete has aforesaid advantage which is constitutive of steel fiber (35kg/m~3) and propylene fiber (2.0kg/m~3).3. Comparing the inner calefactive curve of fire-testing and simulating fire of tunnel engineering with ANSYS analysis soft, this paper gained the heat physical parameter of different fiber concrete. 4. The hybrid fiber can enhance compression-shear strength of fiber concrete. The compression-shear strength has been enhanced 27.6 percent when the concrete is constitutive of steel fiber (35kg/m~3) and propylene fiber (2.0kg/m~3).5. Based on the compression-shear strength guideline of fiber concrete, analyzing the temperature stress of computer simulation, this paper gained that destruct area range and depth range of concrete are minished greatly with the increase of propylene fiber. The blowout phenomenon of concrete has visible melioration when the propylene fiber is 2.0kg/m~3-2.5kg/m~3.6. Integrating the results of tests and computer simulation, this paper gained the better fiber addition, which is constitutive of steel fiber (35kg/m~3) and propylene fiber (2.0kg/m~3-2.5kg/m~3). This kind of hybrid fiber concrete is the same with practical tunnel engineering.