Mechanical characteristics of high constant resistance and large deformation anchor rope in coal mines

To deal with the problems associated with anchor rope support in tunnels with slow and instantaneous large deformation which occurred frequently in coal mines, an appropriate high constant resistance and large deformation anchor rope, which is made of the constant resistance device and anchor body, has been invented based on the oretical analysis, laboratory and field tests. The laboratory test showed that the constant resistance anchor rope provided a constant resistance of 350 kN and the displacement reached 300-950 mm under the static tension, and that the burst resisting force was 280-375 kN under the burst impact dynamic load when the limit elongation was not exceeding 1.6 m. the developed anchor rope displayed the detachment failure instead of breaking failure of traditional anchor rope. Once the anchor rope force exceeded the maximum constant value, the constant resistant cell began to slip. In the slipping stage, the temperature of the constant resistant cell increased rapidly first, then decreased slowly and approached stable finally. The highest working temperature is 35.6°. The external conjugate diameter of the constant resistant cellswasenlarged evenly along its axis, exhibiting a negative Poisson's ratio. The maximum value of radial expansion is 4.1 mm and the Poisson's ratio is between -0.5 and -2.0. In the blast impact failure test at backstopping tunnel, the high gas and constant resistance anchor rope entry retaining and the large section cut roof entry retaining, the maximum slipping value of constant resistant cell was 57 mm. The constant anchor rope has the advantage of low temperature, high pretightening force, and large elongation. © 2016, Science Press. All right reserved.