Stresses in reinforced-concrete roof bolts
- 28 Downloads
At the contact with the reinforcing rod, the cement cladding of a reinforced concrete roof bolt is in a stress-strain state, and as a result the cohesive stresses τCO along the bolt are nonuniformly distributed. Breakage of the set cement at one place causes changes in the cohesion in a remote zone of the bolt.
The zone of active interaction of the rod with the cement cladding,lac, is variable. It depends mainly on the length of the bolt, the ratio between the diameters of the borehole and the bolt, and the force applied to the rod.
Sincelac is not equal to the total length of the bolt, and since the distribution of τCO along the shank is nonuniform, it is necessary to take the maximum value (on the τCO distribution curve) as the permissible cohesive stress. If the permissible value of τCO is found by the method of extraction, the length of the embedded part must be taken as 7–10 da.
Investigations in pits reveal that a reinforced concrete roof bolt actively interacts with the roof rocks. In bedded rocks with rooms not more than 8 m wide, it is permissible to use reinforcing rods 14–16 mm in diameter.
Further pit and laboratory experiments on the cohesion between the reinforcement and the cement in reinforced concrete roof bolts should be directed towards finding standard relations between τCO and the most important factors, with the aim of developing a scientifically well-founded method of calculation.
KeywordsCasing Roof Rock Cohesive Stress Resistance Strain Gage Remote Zone
Unable to display preview. Download preview PDF.
- 1.“Aspects of the cohesion between reinforcement and concrete,” in: Nauchn. Tr. Chelyabinsk. Politekhn. In-ta, No. 56, Chelyabinsk (1968).Google Scholar
- 2.I. Guyon, Prestressed Concrete [Russian translation], Gosstroiizdat, Moscow (1959).Google Scholar
- 3.G. T. Nesterenko, B. S. Skozobtsov, and Yu. S. Afanas'ev, Gorn. Zh., No. 3 (1967).Google Scholar
- 4.V. P. Chirkov, Beton i Zhelezobeton, No. 10 (1962).Google Scholar