SPEGRA INŽENJERING d.o.o.

The scope of works on the bridge Stari Most in Mostar foresaw consolidation and reinforcement of the existing abutment structures of Stari Most, by drilling of grout holes of Ø 56 mm, in grid of one hole/m2, of depth exceeding 5,0 m’, and grouting with grout compounds. Such design solution, which foresees boreholes of large diameter on the stone surface of the existing abutment structures (left and right bank of the Neretva River), was considered a destructive and unsuitable approach to reinforcement. Therefore, we proposed to the Investor a more appropriate solution to grouting works – by drilling through joints (fugues) of a larger number of holes, about 4 – 5 / m2, of smaller profile and various depths, depending on the thickness of the grouted stone wall.

Our opinion about changing the grouting method of abutment structures, beside the objectively more efficient and quality grouting method, was supported by the fact that during archaeological investigation the embankment of abutment structures was excavated (about 1200,00 m3 of rock fill was excavated), after which it could be seen that the abutment structures consist of:

- dominant abutment block
- inner abutment walls of various thickness
- external abutment – wing walls lined with ashlars.

We elaborated our proposal at a special work meeting in Sarajevo, held on Feb. 19th 2003, in the presence of the Investor, Supervisory Team and Special Expert Committee of UNESCO, where our proposal was accepted, providing we prepared a test field, which was done.