Shear strengths of fissures in ledge rock before and after grouting

Conclusions

• 1. Cement grouting of fissured ledge rocks leads to a marked reduction in slip deformation due to an inclined load. The effect of cementation is most marked in badly fractured rocks, the slip of which in the natural state is characterized by an elongated horizontal-displacement graph.

• 2. Cement grouting leads to an increase in the shear strength of hard rocks. Cementation is most effective in badly fractured rocks without fine earth filling, owing to the efficient filling of the cracks by the cement solution. (We must, however, remember that such conditions are not always found in natural rock masses.)

• 3. The use of cement solutions based on dispersed cement (colloidal cement or dry-vibromilled cement) permits cement grouting to be more effective than with ordinary cement.

• 4. The presence of badly broken sections in a rock foundation is not necessarily a reason for reduced slip resistance parameters or for removal of much of the rock, and in such cases we should always consider whether it is advantageous to use cement grouting to improve the quality of the rock.