Importance of grouting for tunneling in karstic and complex environment (a case study from Türkiye)

Abstract In the planning of tunnel support system, besides detailed investigation geological-geotechnical conditions, it is also important to investigate structure-tunnel interaction. Especially structures located in close vicinity tunnels built unpredictable geological conditions should be considered as a part system design and performed. However, strong heterogeneity anisotropy characteristics karstic environments affect planning. this study, single-track railway excavated relatively thin-bedded, limestone Gebze Köseköy Railway project investigated terms interaction importance grouting. The fact that tunnel, center two piers Osmangazi Suspension Bridge approach viaducts, on Gulf Izmit, passes through shallow overburden, an difficulty tunnel. Some caves are determined limestones its heavily fractured nature. It concluded there possibility damage bridge result different settlements under viaduct during construction with performed only filled order prevent possible damages. along route strengthened from surface by injection mixture water, cement, bentonite, sand. after 2D 3D numerical analysis excavation works started. With construction, measurements taken inside piers, values very predicted deformation limits were obtained analysis, successfully completed. Despite extremely difficult main reason why no problems encountered