Strižne lastnosti razpok v hribini

Debeljak, Barbara (author), Fifer Bizjak, Karmen (mentor)

Z novejšimi raziskavami je bilo dokazano, da na strižno trdnost kamninske razpoke vpliva njena celotna geometrija. Napredek tehnologije v zaznavanju topografije nam omogoča natančen opis geometrije v treh dimenzijah. Za opis površine razpoke so bili uvedeni 3D površinski parametri hrapavosti in tako nadomestili pomanjkljiv 2D opis razpok z enim profilom. Na osnovi večjega števila direktnih strižnih preiskav so bili izpeljani novi empirični kriteriji za izračun vrhunske strižne trdnosti po razpoki, ki v svojem zapisu vključujejo površinske parametre hrapavosti. V magistrski nalogi sem preverila primernost do sedaj znanih kriterijev za napoved vrhunske strižne trdnosti. V ta namen je bilo z Robertsonovim strižnim aparatom preiskanih 24 vzorcev različnih litologij, katerim so se izračunali tudi 3D površinski parametri hrapavosti razpok. Yang-ov kriterij in Tang-ov kriterij sem modificirala glede na rezultate analiziranih strižnih preiskav. Dobljene rezultate preiskav sem primerjala tudi s podatki preiskav iz literature, ki so bile izvedene v veliki strižni celici. Izmed vseh analiziranih kriterijev Yang-ov kriterij najbolj točno napove vrhunsko strižno trdnost na vzorcih iz literature, njegova modifikacija pa na preiskanih vzorcih. Podobno oceno točnosti ima pri podatkih iz literature tudi Grasselli-jev kriterij medtem, ko na rezultatih preiskanih vzorcev ne doseže dovolj nizke ocene napake. Ker so bili kriteriji osnovani na podlagi preiskav vzorcev večjih dimenzij v direktni strižni celici, sklepamo, da je potrebno kriterije za uporabo na manjših vzorcih, preiskanih z Robertsonovim strižnim aparatom, modificirati. Modificirana kriterija, predlagana v magistrski nalogi, sta podala najbolj točno in sprejemljivo oceno vrhunske strižne trdnosti v primerjavi z ostalimi kriteriji. Izvedla sem tudi parametrično analizo, s katero sem ugotavljala vpliv posameznega parametra na kriterije. Izmed vseh površinskih parametrov ima parameter hrapavosti C največji vpliv.

• Language: Slovenian
• Keywords: kamninska razpoka, strižna trdnost, 3D površinski parametri, kriterij vrhunske strižne trdnosti, Robertsonov strižni aparat, hrapavost
• Work type: Master's thesis/paper
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Year: 2019
• PID: 20.500.12556/RUL-107506
• COBISS.SI-ID: 1479006
• Publication date in RUL: 21.04.2019

Secondary language

• Language: English
• Title: Shear properties of rock joints

Abstract

Recent results of research have shown that the shear strength of a rock joint is affected by its overall geometry. Technology advancement in the perception of the topography enables us to give a precise description of the geometry in three dimensions. 3D surface roughness parameters were introduced to describe the surface of the joints, thus replacing the inadequate 2D description along one profile of a rock joint. Based on a large number of direct shear tests, new empirical criterions for the calculation of peak shear strength of a rock joint were derived. New criterions take into account 3D surface roughness parameters. In my master's thesis, we examined these known criterions for predicting peak shear strength. For this purpose, 24 samples of different lithologies were investigated with Robertson's shear apparatus. We also calculated 3D surface roughness parameters to use them in criterions. Yang's and Tang's criterions were modified according to the results of the analyzed shear tests. Obtained results of the investigations were also compared with data from literature where investigations were carried out in the large shear cell. Among all the analyzed criteria, Yang's criterion most accurately predicts peak shear strength of a rock joint on the samples from the literature. Modified Youns's criterion also gives the best results on the investigated samples. Accuracy assessment of the Grasselli's criterion is similar to Young's on literature samples, while the results of the investigated samples do not reach a sufficiently low error rate. Since the criterions were based on the investigation of bigger samples in the direct shear cell, it is concluded that the modification of criterions for the use on small samples studied by Robertson shear apparatus is required. The modified criterions gave more accurate and acceptable assessment of peak shear strength of a rock joint compared to unmodified criterions. I also carried out a parametric analysis to determine the influence of an individual parameter on the criterions. Among all 3D surface roughness parameters, parameter C has the greatest impact.

• Keywords: rock joint, shear strength, 3D morphology parameters, shear strength criterion, Robertson´s shear box, roughness