Static tensile mechanical properties and engineering application of constant resistance and large deformation anchor cable

Deep engineering is faced with mechanical phenomena, such as substantial soft rock deformation and in situ stresses, that results in frequent disasters because the energy of the surrounding rock cannot be released normally after excavation. Traditional support materials have low elongation and safety reserves, cannot adapt to large deformations of the surrounding rock, and cannot apply high preload, making it difficult to absorb energy. This study introduces a new type of constant resistance and large deformation (CRLD) cable through static tensile experiments, and compared the results of which with those of ordinary high-strength (HS) cables. Our results showed that the CRLD cable had an obvious constant resistance stage, with a constant resistance value of approximately 415 kN and an elongation rate as high as 25%, which is 3.9 times that of the HS cable. Furthermore, the energy absorption of the CRLD cable was 3.5 times that of the HS cable. Before the first steel strand broke, the temperature of the entire cable was approximately 33 degrees C, and the energy was absorbed evenly without obvious energy concentration. After breaking, the standard deviation of the segmental elongation of the steel strand was 4.16 mm, with a small degree of dispersion. The deformation of each section of the steel strand was uniform lengthwise and the necking rate of the fracture was 8.5%, indicating that there was no obvious necking. On this basis, a comprehensive mechanical performance evaluation index of the cable, that is, the static toughness UT, was proposed, reflecting the strength, elongation, and energy absorption density of the cable. Compared with the HS cable and another widely used He cable with excellent energy absorption characteristics, the UT of the CRLD cable was 117% higher than that of the HS cable and 38.1% higher than that of the He cable. This study also proposes a support and design principle for the CRLD cable and applies a CRLD cable to a roadway with a buried depth of 1050 m. Our results show that, owing to the high-strength reserve of the CRLD cable, the applicable preload can reach more than 85% of the breaking load of the cable, which is 2.3 times that of the HS cable. After this new support was adopted, the maximum deformation of the surrounding rock of the roadway was 180 mm, which is 36% of that of the traditional support. The deformation of the roadway was controlled and the surrounding rock was stable.