Uncertainties in rock and soil engineering are connected with the cognitive boundaries and with the natural variability of the relevant variables. In particular, uncertainties are linked to geometrical and mechanical aspects and the model used for the problem schematization. While nothing can be done to remove the randomness of natural variables, except defining their variability boundaries with stochastic studies, the uncertainties due to the cognitive gaps could be filled by improving the quality of measuring instruments and numerical codes. The present paper considers uncertainties connected to the design of protection barriers against rockfall and contains a simple application of interval analysis to the problem, in order to quantify spacing influence on predicting rock block volume. A case study is also presented: block volume calculated from interval analysis is compared to results obtained from a non-contact survey and validated with in situ measurements. Also kinetic energy calculation is performed in order to show block volume influence on the design of a protection barrier.


The design of a geotechnical structure has inevitably to include the identification and the evaluation of a series of uncertainties due to the characteristics, the complexity and the non-homogeneous nature of the involved medium, either soil or rock. If the design concerns slope stability problems, the amount of uncertainties is further complicated. In fact, not only the time factor has to be considered as an additional variable, but also the spatial dimensions of the potentially involved areas. Therefore, for a better design in the rock engineering field, it is necessary to focus the attention on the involved uncertainties [1]. The nature of the uncertainties in rock engineering is extensively discussed in literature. In [2], for example, sources of errors in sampling are classified as:

• Sampling error;

• Estimation ("statistical") error;

• Measurement error.

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