Experimental investigation of shear strength of soils from the Dobkovičky landslide area and development of correlations between soil strength and their physical properties

Critical and residual states are key soil conditions relevant to slope stability. Evaluating the available shear strength in relation to these conditions is crucial for reliable stability analyses. The best way to determine the strength parameters is through properly selected laboratory tests of soil mechanics. However, in specific cases, these parameters can be estimated based on other material properties of soils. The work clarifies the applicability of various correlation equations from the literature and proposes new relationships, created from laboratory- determined results of strength and index parameters of soils from the Bohemian Central Mountains. It shows how different equations or different material properties of soils can predict the required value of strength. The work also describes how the residual strength of soils and its estimation can be affected. This is mainly caused by the clay fraction proportion and by the shear rate used in its laboratory determination. The results are applied to a specific geotechnical problem - to estimate the critical state and the residual friction angle of soils from the selected study area of the D8 motorway, which is well known thanks to the stability problems. Last but not least, various errors and misunderstandings are discussed, which are often..