hadi atapour

As part of the stabilization systems for excavations and slopes, shotcrete today plays an extensive role in civil and mining engineering practices. A great number of efforts have been made during recent years to improve the strength and ductility of shotcretes. Fiber incorporation can be named as one of these efforts. Based on the type and characteristics of fibers, reinforced shotcretes display different properties. As a result, advantages and disadvantages of each type of fiber are being studied. This study presents the results obtained from experimental investigations of the influence of waste tire textile fiber addition on strength, ductility, and energy absorption capacity of shotcretes. After preparing specimens reinforced at fiber contents of 0.5%, 1%, 1.5%, and 2%, unconfined compressive strength, Brazilian tensile strength, and three-point bending strength were conducted on all samples. The results show that using the fibers inhibits the brittle behavior of specimens and increases energy absorption capacity. Several advantages of using this fiber can be named such as high entanglement in the matrix, low specific weight of the fibers as compared with mesh and steel fibers, easy pumping, and high durability in damp and acidic environments. Moreover, due to the fact of being waste materials, using these fibers leads to lowering the costs of projects as well as tackling the environmental hazards ensued by burying or burning them.

The Schmidt hammer provides a quick and inexpensive measure of surface hardness that is widely used for estimating the mechanical properties of rock material such as uniaxial compressive strength and Young’s modulus. On the other hand, Schmidt rebound hardness can be used for a variety of specific applications. In the mining industries, it is used to determine the quality of rock, which is common practice when constructing rock structures such as those found in long wall mining, room and pillar mining, open-pit mining, gate roadways, tunnels, dams, etc. However, a number of issues such as specimen dimensions, water content, hammer type, surface roughness, weathering, testing, data reduction and analysis procedures continue to influence the consistency and reliability of the Schmidt hammer test results. This paper presents: a) a critical review of these basic issues and b) avaluate the effect of temperature, moisture and uniaxial compressive stress on Schmidt hammer hardness. It was found that water content has a significant effect on the Schmidt rebound hardness (SRH) of rocks. So that increase of water content substantially reduced the SRH of samples. Temperature also had a considerable influence on the SRH. However, relationship between SRH decreases with increasing temperature for tested samples were linear. Also tests results showed that uniaxial loading of samples increases the SRH values.