Faculty of Mining, Geology and Petroleum Engineering University of Zagreb
Abstract
On the site of Maslenica bridge structural tectonic, geophysical and engineering geological investigations, geotechnical drilling and laboratory sample testings were performed. Maslenica anticline is characteristic for the investigated area. It is built from the limestone of Cretaceous age. The anticline has an asymmetrical form with the vergence of the axial plane towards the north. Reverse faults with recent activities are present. The recent activity was proved by the discovery of the broken stalactite with the displacement of 11 cm, whose age is 36000 years. On quite young stalactites (stalagmites) in the cave on the west side, no displacements were noticed. For the next period of 500 years the maximal possible displacement of 2.0 cm is foreseen. Smaller caves with the dimensions of 1 m3, were formed on the intersections of the reverse faults and greater joints. The canyon Novsko ždrilo was formed in the fault shear zone with tectonic transport to the right.
According to the range of fracture, three characteristic types of rock masses were separated by engineering geological investigations. According to »Geomechanical classification« (RMR) the first type corresponds to II to III class, while the second type corresponds to IV class, and the third type corresponds to V class (mylonite).
Because of the complexity of the terrain structure, original engineering geological bases of design have not enabled the direct application of the analysis of stress-strain behaviour. Because of that the simplified geotechnical models were done. They enabled the projecting of foundation in the rock mass and renewal of poor quality rock mass.Na lokaciji Masleničkog mosta urađena su strukturno-tektonska. geofizička i inženjerskogeološka istraživanja, istražna bušenja i laboratorijska ispitivanja uzoraka. Za istraživano područje karakteristična je Maslenička antiklinala. Izgrađena je od vapnenaca kredne starosti. Antiklinala ima asimetričan oblik s vergencijom osne ravnine prema sjeveru. Prisutni su reversni rasjedi s recentnom aktivnošću. Recentna aktivnost dokazana je nalazom presječene sige s pomakom od 11 cm, čija starost je 36000 god. Na sasvim mladim sigama u špilji na zapadnoj strani nisu uočeni pomaci. Za povratni period od 500 godina progno¬ziran je mogući maksimalni pomak veličine do 2,0 cm. Manje špilje dimenzija do 1 m3 nastale su na presjecištima reversnih rasjeda i većih pukotina. Kanjon Novsko ždrilo nastao je u zoni smicanja rasjeda s desnim tektonskim transportom.
Prema stupnju razlomljenosti izdvojene su inženjerskogeološkim istraživanjem tri karakteristične sredine. Prema »Geomehaničkoj klasifikaciji« (RMR) prva sredina odgovara II, do III. klasi, druga sredina odgovara IV. klasi, a treča sredina odgovara V. klasi (milonit).
Originalne inženjerskogeološke podloge nisu omogućile, zbog složenosti građe terena, direktnu primjenu u analizi odnosa naprezanja i deformacija. Zbog toga su izrađeni simplificirani geotehnički modeli. Oni su omogućili projektiranje temeljenja u stijenskoj masi i saniranja dijelova slabe kvalitete
