To clarify the bearing characteristics of bolt-grouting support in shallow fractured surrounding rock of roadway

comparative bolt-grouting bearing capacity test was carried out with different rock particle sizes

lithologies

and number of bolts. The results show that: 1) the bearing capacity of the bolt-grouting increases first and then decreases with increasing the particle size. Compared with the non-anchored specimens under the same conditions

the peak stress of the anchored specimens increases by 53.38% on average

and the peak strain decreases by 46.43% on average. 2) Under anchored condition

the free surface opposite to the supporting surface and its vicinity are the preferred area for macro-fracture development. The failure of supporting surface generally lags behind the free surface

and the specimens gradually transit from mainly tensile failure to tensile-shear mixed failure; tensile failure is the main failure mode of specimens under the condition of no anchor. 3) With the increase of bolt number

the bearing capacity of bolt-grouting increases gradually

but the growth rate slows down gradually. The peak strain slows down

which is consistent with the inflection point of peak stress growth. 4) The specimens have three characteristics of progressive destruction: firstly

the cracks generated before peak stress continue to propagate after peak stress; secondly

the surface material of support surface spalls with the crack stretching; thirdly

the cracks gradually develop from surface to inside of the specimens

the rock fragments fall off first

and then the macro-damage develops to the anchor area

resulting in the loss of overall specimen bearing capacity.