More than 50 % of Croatia’s area is situated in karst terrain which is characterized by dissolution of limestones, dolomites and other soluble rock masses under the influence of water, CO 2, temperature etc. As a consequence of this process, often referred to as ‘karstification’, a large number of karst phenomena is linked with engineering activities and directly influence existing infrastructure, especially national highways and roads. Since many highway sections, out of 1 300 km in total, are constructed in karstification susceptible terrain, phenomena such as faults or caverns can have large impact both on construction works as well as on structure behaviour during exploitation. The latter became more obvious in last few years since number of exploitation issues have been reported. Few of these phenomena are presented in this paper, including cavern near Bosiljevo exit, suffosion sinkhole near tunnel Sv. Marko and bulging of pavement near tunnel Veliki Glozac due to karstificiation of bottom layers. Besides describing the nature of these phenomena, this paper presents a methodology for their remediation combining different non-invasive geophysical methods whereas method of seismic refraction will be shown in this paper since it yields best results for fulfilment of task. The main advantage of this methodology is to obtain relatively precise information about presence, distribution and size of karst features in fast and simple manner. Based on these data, a technical documentation including remediation measures was prepared and the remediation works were conducted, or will be conducted, accompanied by detailed quality control program.

karstification; highways; cavern; suffusion sinkhole; seismic refraction