Przyczynek do znajomości wpływu deformacji podłoża na kinematykę osuwisk

Abstract

Dokonano analizy elementów strukturalnych podłoża (południowy stok wzgórza Kłodne w Klęczanach) pod kątem ich wpływu na deformacje osuwiskowe. Ustalono rolę poszczególnych elementów w kolejnych etapach deformowania się zbocza.CONTRIBUTION TO THE KNOWLEDGE OF INFLUENCE OF BEDROCK DEFORMATIONS ON THE KINEMATICS OF LANDSLIDESThe paper presents the results of studies on rejuvenation of successive types of discontinuities in the Flysch bedrock along with development of landslide processes. Differences in scale of structural elements and in their orientation in relation to surface of the deformed slope impede full reconstruction of regularities at the present stage of studies.The studies covered southern slope of the hill Kłodne (614 m a.s.l) at the KIęczany village, the Beskid Wyspowy Range (Fig. 1, Table I, Fig. 5). The slope displays strong tectonic disturbances. It is situated at the boundary of tectonic window of the Ropa Pisarzowa unit and the Magura nappe. Its lower and middle parts are built of shale series of the Grybów and Inoceramus Beds, and·the upper - of the Magura Sandstones. The slope relief is determined by differences in tectonics and lithology. Here are differentiated valley depressions and three landslides - A, B and C. The landslide B was studied in detail (Fig. 2).In analysis of structural elements of bedrock, there . were taken into account: 1 - strike and dip of strata, and 2 - discontinous deformations - major dislocation lines, secondary fractures parallel to the major dislocation lines, and tectonic and decompressional-gravitational joint. )The slope surface is insequent in relation to dip of strata which resuted in structural-insequent slide nature of the originating landslides. However, the undercutting of slope was deep enough for development of subsequent and consequent slide (Fig. 3). The major dislocation lines were determining development of valley depression and western margins of niches of landslides A and C. Secondary fractures parallel to the major dislocation lines (Table I, Fig. 6), and tectonic joint T1 – T1’ (Table II, Fig. 7) are responsible for the course of western margin of niche of the landslide B. Tectonic joint (T2) and decompressional-gravitational fractures (Table II, Fig. 8) facilitated further development of the landslide B, involving insequent slide consistent with inclination of the slope and accompanying development of fissures parallel to valley axis. Joint T2 and L became manifested at the final stage in development of that landslide, when a· part of its plate became sheared off and consequent slide developed in its lower, western part, subjected to load of rocks sliding downhill.The revealed interrelationships between bedrock structure and the landslide kinematics may be useful as an index in prognoses of development of landslides on slopes built of flysch rocks.In the course of studies on the slope of the hill Kłodne, there were gathered some new data on conditions of development of landslides in areas subjected to strong tectonic deformations. A large accumulation of sinter which, due to its hygroscopic properties, is reducing friction at the slide surface, was found in the substratum. This indicates that besides the well known agents, there may be active some others, still poorly known but which contribution to decrease in slope stability is fairly important.