In order to economically and reasonably solve the problem of mineshaft support in complex geological conditions, the mechanical properties of high-performance steel-fiber-reinforced concrete (HPSFRC) and its application in mineshaft lining structures were investigated in this study. Firstly, the mix proportion of HPSFRC for the mineshaft lining structure was obtained through raw material selection and preparation testing. Then, a series of mechanical property tests were conducted. The test results showed that the compressive, flexural, and tensile strengths of HPSFRC were 9%, 71%, and 53% higher than that of ordinary concrete, respectively. The fracture toughness of HPSFRC was 75% higher than that of the ordinary concrete and the fracture energy of HPSFRC was 16 times that of the ordinary concrete. Finally, the model test results of the HPSFRC shaft lining structure showed that the crack resistance, toughness, and bearing capacity of the shaft lining structure had been significantly improved under a non-uniform confining load because of the replacement of ordinary concrete with HPSFRC. HPSFRC was proved to be an ideal material for mineshaft support structures under complex geological conditions.
To address the cracking and leaking of concrete in frozen shaft linings in deep and thick topsoil layers in coal mines, hybrid-fiber-reinforced concrete (HFRC) was developed. First, the composition of the reference concrete was obtained by investigating high-strength concrete commonly used in shaft linings, and two dosages of polyvinyl alcohol fiber (PVAF) and polypropylene plastic steel fiber (PPSF) were obtained by the mixing test. Then, tests of early cracks of concrete were conducted; results showed that HFRC could almost avoid early cracks, exhibiting an advantage in early crack resistance. Thus, HFRC can play a significant role in improving the durability of frozen shaft linings in complex underground environments. Furthermore, a series of mechanical property tests were carried out. The results showed that the compressive strength of HFRC was similar to that of the reference concrete, but the tensile and flexural strength of HFRC was 42.7% and 35.1% higher than that of the reference concrete, respectively. Finally, an analog simulation model test of shaft linings was conducted. The new type of shaft lining structure containing hybrid fibers (HFs) exhibited plastic deformation characteristics under load, and the maximum hoop strain was −3562 με. It addressed the problem of high brittleness of frozen shaft lining structures of ordinary high-strength concrete and improved the toughness and crack resistance. HFRC is an ideal material for frozen shaft lining structures in deep and thick topsoil.
7 May 2019 in Advances in Materials Science and Engineering
To economically and reasonably solve the difficult problem of mine shaft support subject to complex geological conditions, we studied the mechanical properties of polypropylene macrofiber-reinforced concrete (PPMFRC). First, we selected test raw materials through an investigation and comparison of technical parameters. Second, using a preparation test, we obtained the composition of reference concrete of PPMFRC for the mine shaft lining structure, and test specimens were manufactured according to relevant test technical regulations. Finally, the mechanical properties of the specimens were compared, and the results show that the compressive, flexural, and tensile strengths of PPMFRC were increased by approximately 3%, 30%, and 20%, respectively, for mixtures with polypropylene macrofibers. The fracture toughness of PPMFRC was between 0.26 and 0.35, and the fracture energy was between 382.7 N/m and 485.6 N/m, which is significantly higher than that of plain concrete. The test results show that PPMFRC is an ideal material for the lining structure of a mine shaft under complex geological conditions, and we have provided technical parameters for engineering applications.
1 May 2021 in European Journal of Mechanics - A/Solids
Woven fabric composites made from commingled fibreglass and polypropylene fibres have the potential to make lightweight structural parts to replace metal structures in automobiles when competitively produced using thermostamping techniques. To expedite the acceptance of such composites, a credible design tool needs to be available to study the associated manufacturing process. For such a numerical method, a material model is required. Because the tows of the fabric are essentially inextensible, shear is the major deformation mode for assuming the stamped shape. The shear mechanical behaviour of fabric is obtained from a shear-frame test. A finite element model using a combination of truss and 2D solid elements is proposed. The truss elements represent the tows and use a nonlinear material model for capturing the increasing stiffness of the tows with increasing tensile strain. The 2D Solid elements capture the interaction between tows and the viscosity of the resin. The bias-extension test is a valuable test for investigating the shear performance of woven fabric composites. Using the finite element method, the bias-extension test is modelled, analysed and compared experimentally to verify the credibility of the woven-fabric material model.
1 January 2022 in Probabilistic Engineering Mechanics