Kovačević, MS, Jurić-Kaćunić, D, Arbanas, Ž & Petrović, N 2008, 'Ground Improvement by Jet Grouting Method in St. Kuzam Tunnel — Monitoring of Performance ', in Y Potvin, J Carter, A Dyskin & R Jeffrey (eds), SHIRMS 2008: Proceedings of the First Southern Hemisphere International Rock Mechanics Symposium, Australian Centre for Geomechanics, Perth, pp. 73-84, https://doi.org/10.36487/ACG_repo/808_85
(https://papers.acg.uwa.edu.au/p/808_85_Kovacevic/)
Abstract: The St. Kuzam tunnel was constructed on the D8 Croatia state road, on the Orehovica-Draga-Sv. Kuzam section. The rock mass stability problem appeared during the construction of the tunnel. About 30 m of the constructed tunnel caved in while excavating from carbonate rock to the part with non-degraded and weekly degraded siltstone. For further excavation of the tunnel, the jet grouting method was used to improve the mechanical characteristics of the caved-in material. 

The paper shows the implementation of the quality control program of ground improvement by jet grouting. It has been established, with bored profiles and conducted laboratory testing, that a new, relatively homogeneous material of significantly improved mechanical characteristics, was produced by jet grouting in the caved-in tunnel zone. Mechanical characteristics of the new material, as well as the new ground improvement level, were successfully established by using the non-destructive method of the spectral analysis of surface waves (SASW).

The paper also shows back numerical analyses of the excavation and lining support system in the tunnel, that have been conducted based on ground movement measurement results around the underground opening with inclinometers and sliding micrometers. Numerical back analyses, combined with geotechnical measurements and monitoring, give the possibility to establish real mechanical characteristics of the ground where the underground excavation is carried out. Numerical back analysis is also used to verify or modify characteristics of primary lining support system elements, predicted progress length, estimated stability time of non-support span, as well as time and sequence of the implementation of all excavation stabilisation works.