Steel Strands for Soil/Rock Anchor System
The soil/rock anchor system is anchored into the rock mass by drilling holes in the weak structural surface of the rock, connecting the sliding rock mass with the stable rock layer, thereby changing the stress state of the slope rock mass and improving the integrity and strength of the unstable rock mass on the slope.
The soil/rock anchor system is to ensure the safety of the construction of the underground structure and the surrounding environment of the foundation pit, and it is a reinforcement and protection measure for the sidewall and its surrounding environment. With the development of science and technology, the soil/rock anchor system no longer uses wooden sticks, but now uses steel strands which improve the safety measures.
The soil/rock anchor system mostly adopts 1860MPa (270 grade) bonded or unbonded, high-strength, and low-relaxation steel strands. Its mechanical properties shall comply with the standard of GB/T5224-2015 and ASTM A416. The anti-corrosion grease of the unbonded steel strand should have good chemical stability, and should not contain harmful ingredients, and the coating amount should not be less than 50g/m. The thickness of the PE coat is 1.0 to 1.2 mm, and it should have certain toughness and hardness, as well as anti-corrosion and anti-aging properties.
For bonded steel strands, there should be no lubricant and oil on the surface of the strand, which may reduce the bond between the strand and the concrete. In prestressed construction, slight rust can be allowed on the surface of the steel strand used, but there shall be no visible rust and pits.