During monitoring measurements of the slope stability performed before construction of the D1 motorway in central Slovakia,a significant activation of landslides was observed in a motorway section long about 2 km.Such deep and active landslides were not taken into consideration during design stage.Therefore,it was decided to reassess the realization of the motorway in the originally designed route and to assess the possibility of choosing more favourable alternative route.To decide which alternative is the best one,a risk analysis of feasibility of the original(surface variant VI)and a newly proposed route(tunnel variant V2)were performed.In the article,the risks are assessed in detail-such as qualitatively or quantitatively expressed functions of probability of occurence of certain hazards and magnitude of its adverse consequences on vulnerable motorway sections and objects(vulnerability)within a certain time period(exposure).The considered exposure is usually the construction period or the service life of the motorway and its objects.The analysis focused on geological,geotechnical and hydrogeological risks.However,the decisive risk was the interference of the motorway route with the landslide area.Risks of the variant VI were evaluated for 10 sections and in the V2 variant four sections have been evaluated.The results of the risk analysis revealed that 35.5% of the VI route was classified to the highest risk,grade 5.In variant V2 only 8% of the route was classified to grade 5.So,it was advisable to consider changing the original motorway route with the alternative one.In the present,works to begin building the motorway in the new route,which was also recommended by the risk analysis,are underway.
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