Ruchy masowe na zboczach zbudowanych z ilów krakowieckich (na przykładzie doliny Wisły i Sanu)

Abstract

Najbardziej charakterystycznymi typami powierzchniowych ruchów masowych na zboczach zbudowanych z iłów krakowieckich w dolinie Wisły i Sanu są klasyczne osuwiska, zsuwy i spełzywanie. O stateczności tych zboczy decydują przede wszystkim powierzchnie osłabienia i resztkowe parametry wytrzymałości na ścinanie. Okres stabilizacji zboczy w iłach krakowieckich zależy od drenażu wód i w przypadku zboczy silnie zawodnionych jest on długotrwały.

MASS MOVEMENTS ON THE SLOPES COMPOSED OF THE KRAKOWIEC CLAYS (EXEMPLIFIED IN THE VISTULA AND SAN V ALLEYS)

Almost on the whole area of the Krakowiec clays occurrence, the slopes of the great river valleys show the features of the slide origin morphology and recently in many places, significant activity of mass movements can be observed. Many years' observations of natural slopes of the Vistula Valley (between Baranów Sandomierski and Tarnobrzeg) and the San Valley (between Krzeszów and Zarzecze near Nisko) have given information on character and dynamics of slide process development in various geological conditions (including hydrogeological conditions) and on effects of the letter on the process of the slope stabilization. The paper presents the major conclusions resulting from analysis of the above dependences regarding to properties of the internal structure of the massif composed of the Krakowiec clays.

The properties of the clays, particularly the over consolidated clays (to which the Krakowiec clays belong) depend on time. With lapse of time they absorb water and the primary mainly negative, pore pressure is subject to diffusion, the water content increases, and effective strength decreases. This picture is complicated by natural surface of weakening, both the sedimentation type and discontinuity type. The strength along these surfaces is close to the residual strength. The residual angle of internal friction ranges from 8 to 10° in the maximum value 16-18°. \

High sensiveness on egzogenic factors is a very important feature of the Krakowiec clays. Under the influence of cyclic drying and wetting they are subject to convert from soil of very good strength properties into the weathering soil eluvium with low strength parameters. The following major conclusions resulted from the investigation:

1. The most characteristic types of surface mass movements developed on natural slopes of the investigated river valleys are classica1 slides, weathering cover slides and creeps.

2. Surfaces of weakening and residual shear strength parameters determine mainly the stability of profiled slopes in the non-weathering Krakowiec clays.

3. The period of the slope stability in the Krakowio: clays depends on water drain. In case of highly watered slopes the process is longlasting.

4. No visible with deformations are observed on slopes with inclination less then 7-8°. These slopes are stable.