This paper presents the impact of selected essential aspects of geological structure on the state of slope stability as assessed by changes in the safety factor (SF). The engineering geological slope features that were analysed include: (i) changes in soil cohesion and internal friction angle, (ii) presence of a weak soil layer and its span, (iii) structural discontinuity (i.e. fault), (iv) soil permeability properties and water conditions (i.e. groundwater level, long and heavy rainfall). A certain scheme of slope stability calculations has been proposed for a case involving complex geological conditions. The numerical modelling of a hypothetic slope was performed using the shear strength reduction method based on the finite element method.

This study concerns the creep impact on strength parameters of the selected very cohesive soils (PI = 30–70%). The analysis refers to Neogene clays characterized by a complex structure, resulting directly from a complicated load history in the geological time scale and identified glacitectonic deformations. In the process of samples’ preparation for strength tests as well as during the interpretation of the post-failure state, particular attention was paid to the soil structure. The imaging methods (X-ray densitometry and computer microtomography) enabled the comparison of the soil structure and the selection of samples with similar characteristics. The completed program of strength tests consisted of two series of tests in the triaxial stress state, differentiated by the occurrence of the initial creep stage, preceding the typical strength test scheme under undrained conditions. This study allowed to obtain a quantitative assessment of the influence of the creep process on the strength parameters of tested soils. Constant stress lower than 60% of the shear stress deviator leads to the deceleration creep course (m parameter 0.64–0.89). As a result, higher values of internal friction angle (20% increase comparing to triaxial tests without creep stage) and cohesion reduction are obtained from triaxial creep tests. Creep parameter m is found to be a valuable indicator for differentiation of landslide activity trend. The tests proved low values of axial strains (1–5%) at failure, which was associated with lithogenesis. By the implementation of obtained strength parameters into the 3D finite element model of the slope, the potential influence of the creep process on the stability of an exemplary cross section of the Warsaw slope could be determined.

Imaging of the surface of materials by atomic force microscopy under tapping and phase imaging mode, with use of modified probes is addressed. In this study, the circularly shaped holes located in varying distance from the probe base, were cut out by focused ion beam. Such modification was a consequence of the results of the previous experiments (probe tip sharpening and cantilever thinning) where significant improvement of image quality in tapping and phase imaging mode has been revealed. The solution proposed herein gives similar results, but is much simpler from the technological point of view. Shorter exposition time of the tip onto gallium ions during FIB processing allows to reduce material degradation. The aim of this modification was to change harmonic oscillators' properties in the simplest and fastest way, to obtain stronger signal for higher resonant frequencies, which can be advantageous for improving the quality of imaging in PI mode. Probes shaped in that way were used for AFM investigations with Bruker AFM nanoscope 8. As a testing material, titanium roughness standard sample, supplied by Bruker, was used. The results have shown that the modifications performed within these studies influence the oscillation of the probes, which in some cases may result in deterioration of the imaging quality under tapping mode for one or both self-resonant frequencies. However, phase imaging results obtained using modified probes are of higher quality. The numerical simulations performed by application of finite element method were used to explain the results obtained experimentally. Phenomenon described within this study allows to apply developed modelling methodology for prediction of effects of various modifications on the probes' tip, and as a result, to predict how proposed modifications will affect AFM imaging quality.