Vplivni dejavniki globine spodjedanja flišnih plasti na slovenskih obalnih klifih

Zorn, Mateja (author), Verbovšek, Timotej (mentor)

Klifi na slovenski obali predstavljajo strma in razmeroma nestabilna pobočja, ki so zaradi heterogene litološke zgradbe, kjer se menjavajo predvsem plasti laporovcev in peščenjakov, močno izpostavljena erozijskim procesom. Eroziji so najbolj podvrženi laporovci, saj preperevajo hitreje kot trši peščenjaki, ki ležijo nad njimi. Posledično prihaja do postopnega spodjedanja peščenjakov in nastajanja zajed, kar sčasoma vodi v njihovo odlamljanje ter padanje skalnih blokov. V okviru raziskave smo vzdolž obale določili 20 lokacij, kjer je morje skoraj v neposrednem stiku s klifom, ob njegovem vznožju pa se nahajajo nižje ležeče, debelejše plasti peščenjaka, ki so izpostavljene spodjedanju. Na izbranih lokacijah smo izvedli terenske meritve ter odvzeli kamninske vzorce za nadaljnje geomehanske analize in analize njihove sestave, s katerimi smo želeli bolje opredeliti lastnosti kamnin in njihovo odzivnost na erozijske procese. Cilj raziskave je bil določiti globino spodjedanja posameznih plasti peščenjaka ter preveriti morebitne statistične korelacije z izbranimi inženirsko-geološkimi in geomehanskimi parametri, pa tudi s parametri sestave kamnin. Rezultati kažejo, da je globina spodjedanja močno povezana z debelino plasti in razpoklinskim sistemom. Močna pozitivna korelacija med debelino plasti in globino spodjedanja (r = 0,78) nakazuje, da debelejše plasti omogočajo razvoj večjih previsov in s tem intenzivnejše spodjedanje. Pomemben dejavnik je tudi razdalja med razpokami, pri čemer družina razpok R2 kaže močne pozitivne korelacije tako z debelino plasti (r = 0,8) kot z globino spodjedanja (r = 0,68). Večje razdalje med razpokami vodijo v nastanek večjih in masivnejših kamnitih blokov, ki omogočajo razvoj izrazitejših spodjed. Korelacije globine spodjedanja s sestavo kamninskih vzorcev pa kažejo močne pozitivne povezave predvsem s cementom (r = 0,89) in siliciklastičnimi komponentami, zlasti s kremenom (r = 0,71). Večja vsebnost cementa in kremena povečuje trdnost kamnine, kar prispeva k večji odpornosti proti eroziji, hkrati pa postanejo takšni peščenjaki bolj izpostavljeni spodjedanju.

• Language: Slovenian
• Keywords: slovenski obalni klifi, fliš, peščenjak, spodjedanje, korelacije
• Work type: Master's thesis/paper
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Year: 2026
• PID: 20.500.12556/RUL-183960
• Publication date in RUL: 23.06.2026

Secondary language

• Language: English
• Title: Factors influencing depth of undercutting of flysch beds in Slovenian coastal cliffs

Abstract

Cliffs on the Slovenian coast represent steep and relatively unstable slopes, largely due to their heterogeneous lithological composition, where layers of marl and sandstone alternate. This structural variability makes them particularly vulnerable to erosion. Marls are more prone to weathering than the harder sandstones overlying them. Consequently, gradual undercutting of the sandstones occurs, leading to the formation of notches, which over time cause their detachment and the fall of rock blocks. In this study, 20 locations along the coast were identified where the sea is almost in direct contact with the cliff, and where lower, thicker sandstone layers at the cliff base are exposed to undercutting. Field measurements were conducted at the selected locations, and rock samples were collected for further geomechanical and mineralogical analyses, aiming to better characterize the properties of the rocks and their response to erosional processes. The aim of the study was to determine the depth of undercutting of individual sandstone layers and to investigate potential correlations with selected engineering-geological and geomechanical parameters, as well as parameters related to rock composition. The results show that the depth of undercutting is strongly related to the layer thickness and the joint system. A strong positive correlation between layer thickness and undercutting depth (r = 0,78) indicates that thicker layers allow the formation of larger overhangs, resulting in more intense undercutting. Another important factor is the spacing between joints, with the R2 joint set showing strong positive correlations with both layer thickness (r = 0,8) and undercutting depth (r = 0,68). Larger distances between joints lead to the formation of bigger and more massive rock blocks, which facilitate the development of more pronounced undercuts. Correlations between undercutting depth and rock composition show strong positive relationships, particularly with cement (r = 0,89) and siliciclastic components, especially quartz (r = 0,71). A higher content of cement and quartz increases the rock’s strength, contributing to greater resistance to erosion, while at the same time making such sandstones more susceptible to undercutting.

• Keywords: Slovenian coastal cliffs, flysch, sandstone, undercutting, correlations