Study On The Properties Of Polypropylene Fiber Concrete And Its Application In Tunnel Engineering

In recent years,the crack problem of the concrete is more and more outstanding in engineering practice and also such in the tunnel engineering particularly,it puts forward the test to the safety and durability of the structure.The tunnel concrete lining cracking is one of several tunnel diseases to take place with more rate,how to resolve that problem by the root is the special regardful item for the large number of technical personnel of the tunnel engineering.That adopting the polypropylene fiber concrete to be the tunnel concrete lining and resolving the problem of the concrete appearing crack is a kind of new extensively studies and applications path in recent years. Its principle mainly lies in: the cement in the concrete is the gelatinization material to bone to the fibers, These fibers are similar to very small distributed reinforcing steel bar in function, consuming the energy of the concrete cracking,raising the concrete toughness,bracketing aggregates and reducing the concrete segregation and bleeding,thus they control the generation and expansion of the internal microscopic checks of the cement,and raise the concrete crack resitance.This thesis introduces two kinds of the fiber-reinforced concrete mechanism, namely the composite material theories and the fiber-spacing interval theories, and deduces the formula of the first-crack strength of extension and the ultimate strength of extension of the composite materical.At the same time, through these check experiments between the fiber concrete and the common concrete,such as working performance,compression strength,strength of extension,elastic radio,dry shrink-age,crack resistance,durability,toughness and high temperate endurance, the paper analyzes synthetically the performance of the fiber concrete,and gets the knowledges of the predominance of the fiber concrete on the physical and mechanical properties.Moreover,according to the actual engineering item,we still make the experiments of the sprayed fiber concrete on the spot, also prove that the fiber concrete can raise the strength stability of sprayed concrete, reduce its rebound elasticity, improve obviously the construction conditions, raise the construction quantity, prolong the service life of structure.