Action mechanism of wet shotcrete in roadway shotcrete support

Action mechanism of wet shotcrete in roadway shotcrete support
  Wet shotcrete has good mechanical properties and overcomes the deficiency of low strength of dry shotcrete
Its 28d uniaxial compressive strength can reach 30-50mpa The use of wet shotcrete and bolt support technology can effectively improve the stability of roadway
The reason is that the role of wet shotcrete bolt support in roadway support is mainly reflected in the following aspects: shotcrete bolt support wet shotcrete machine http://www
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  (1) Support function
The strength of wet shotcrete is 45% - 85% higher than that of dry shotcrete, and has higher early strength: when used in combination with anchor bolt in primary support, it can control the expansion deformation and failure of surrounding rock in the anchorage area, such as delamination, sliding, tension cracking and aging, improve the mechanical parameters such as rock strength, elastic modulus, cohesion and internal friction angle in the shotcrete and anchor area to varying degrees, and improve the mechanical properties of plastic deformation and broken rock mass, Significantly improve its post yield strength, change the deformation characteristics of rock mass after yield, maintain the integrity of surrounding rock in the anchorage zone to the greatest extent, avoid harmful deformation of surrounding rock, and improve the overall strength and stability of surrounding rock in the anchorage zone

  (2) Filling and isolation
Because the wet shotcrete slurry has good fluidity and is sprayed on the rock wall at high speed, the mortar and fine materials are squeezed into the rock cracks and joints, resulting in wedge effect, which can fully fill the cracks and joints of surrounding rock, and greatly improve the overall strength of rock mass
At the same time, there is good viscosity between the wet shotcrete layer and the rock wall
The wet shotcrete completely seals the surface of the surrounding rock, completely isolates the touch of air, water and the surrounding rock, effectively prevents the damage and spalling of the surrounding rock caused by weathering and deliquescence, and avoids the loosening of the surrounding rock and the weakening of its self-supporting capacity
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  (3) Stress transformation
High speed (30-120 M / s) spray on the rock surface to form a high-strength concrete layer, which has high adhesion, so that the concrete is closely combined with the surrounding rock, and the load of the rock layer between the anchor bolts is transmitted to the anchor bolt, so that the concrete layer, the anchor bolt and the surrounding rock form a mechanical system with large stiffness
For the tensile area, it can offset part of the tensile stress and improve the tensile capacity of the surrounding rock: for the shear area, The shear resistance of surrounding rock is improved by the friction generated by compressive stress
In addition, adding steel fiber or plastic fiber into the shotcrete can replace the traditional steel mesh, which can not only reduce the mesh hanging process, but also effectively improve the overall mechanical properties of the concrete, especially improve the tensile strength and deformation capacity of the shotcrete layer, and can deform together with the surrounding rock to achieve the purpose of proper pressure reduction and strengthening the primary support strength, which plays a very important role in the stability of the roadway