Study on mechanical properties of polypropylene fiber cement mortar under impact load

In order to study the support potential of sprayed mortar mixed with polypropylene fiber (PPF) on the soft rock roadway when the instantaneous failure occurs in the application of reinforcement of the mine, cement mortars with water-cement ratios of 0.3, 0.4, and 0.5 were prepared and mixed with PPF at volume fractions of 0, 1%, 1.25%, and 1.5%, respectively, and were cast into cylindrical specimens of 50 mm×25 mm. A split Hopkinson pressure bar (SHPB) of 50 mm was used to conduct shock compression tests on the above-mentioned specimens with three loading pressures of 0.25, 0.35, and 0.45 MPa, respectively. By comparing and analyzing the dynamic mechanical properties of mortar specimens with different water-cement ratios and different PPF volume contents under impact load, the effects of water-cement ratio and PPF volume contents on the impact load of jet mortar were studied respectively. The test results show that the failure characteristics of typical specimens has the strain rate effect and the fragmentation size decreases with the increase of strain rate. The dynamic stress-strain curve of PPF reinforced mortars can be divided into four stages of elastic deformation, crack expansion,〖LM〗plastic deformation and failure. In the stage and failure stage, with the increase of the strain rate, the plastic deformation stage is correspondingly strengthened; when the volume content of PPF is the same, the mortar specimen with higher porosity and high water-cement ratio is beneficial to absorb stress wave energy and show better impact resistance; when the volume content of PPF is 1.25%, the fibers evenly distributed in the mortar change the stress propagation path, relieve the phenomenon of stress concentration, and make the jet mortar have better deformation coordination ability through bridging and reinforcement. Moreover, the dynamic compressive strength and ultimate toughness of the PPF reinforced mortar with the current dosage are the highest, and it has a better ability to resist instantaneous load damage. The above test results have a certain reference value for regulating the mortar ratio and enhancing the ability to absorb waves and absorb energy.