Engineering-geological scientific study investigating the relationship of slope gradients to two basic types of rock masses in the Czech Republic

The presented scientific study evaluates and quantifies the relationship of slope gradients to two fundamental types of rock masses in the Czech Republic. Investigating slope gradients within engineering geological zones of soil or rock and weathered rock masses (these areas were analyzed using a 1:50,000-scale map, whereas a previously published study used only a 1:500,000-scale map) is a fundamental scientific inquiry, as it compares the behaviour of these two basic mass types in engineering geology, geotechnics and geospatial analysis based on slope gradient values. Slope gradient is essentially the sole parameter observable on the surface across the entire country, allowing us to compare the behaviour of these two mass types. The study was divided into two parts, with the first study evaluating a group of engineering geological zones with Quaternary and pre-Quaternary geological structures (Study 1). The second study, which is of greater scientific significance (Study 2) assessed two groups of engineering geological zones with rocks and weathered rocks and their eluvium (rocks and weathered rocks), and zones with soil engineering geological characteristics. For all variations and zones, statistical characteristics were determined (average slope gradient, 25% quantile, 50% quantile, 75% quantile, and maximum slope gradient). It was found that the groups exhibit significant statistical differences in slope gradients in the Czech Republic. The most significant finding from Study 2 was that the group of engineering geological zones with rocks and weathered rocks and their eluvium (Group 2A) and the group of soil zones (Group 2B) had a difference between the minimums of average slope gradients of 3.0°, representing a 41% share of the total differences. In contrast, the difference between the maximums of average slope gradients in both groups of masses was even greater at 4.4°, representing a 59% share. When comparing the difference between the minimum and maximum of average slope gradients in the first (2A) and second group (2B), a difference of 5.6° (57% share of the total differences) was found in the first group, whereas in the second group, it was lower at 4.2° (43%). It is evident that soil masses and masses of rocks and weathered rocks must manifest differently due to primarily distinct physical-mechanical properties. This is logically reflected in slope gradients, as demonstrated and quantified in the Czech Republic through this study. Soil masses have lower slope gradients compared to masses of rocks and weathered rocks with their eluvium, which is entirely logical and corresponds to their material nature and the structure of the rock mass, reflecting in physical-mechanical properties observed on the surface in a single parameter, namely the assessed slope gradient.