Open AccessDetermination of the basic friction angle ϕb of joints using the field tilt test: results of various “fast” tests on outcrops
Author(s) -
Luis Jordá Bordehore,
Leandro R. Alejano,
Roberto Tomás,
Silvia Loaiza,
Mishel García-Vela,
Rubén Galindo,
Ignacio Pérez–Rey,
A. Riquelme-Guill,
Miguel Cano,
César Borja-Bernal,
Rubén Medinaceli Tórrez
Publication year - 2021
Publication title -
iop conference series. earth and environmental science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.179
H-Index - 26
eISSN - 1755-1307
pISSN - 1755-1315
DOI - 10.1088/1755-1315/833/1/012048
Subject(s) - tilt (camera) , geology , classification of discontinuities , joint (building) , slumping , lithology , direct shear test , field (mathematics) , shear (geology) , geotechnical engineering , structural engineering , geometry , mathematics , engineering , petrology , mathematical analysis , geomorphology , pure mathematics
The basic friction angle of rock joints is usually obtained from tilt tests, being the most common the laboratory tilt tests. This test has been standardized according to the ISRM. However, most of the times when calculating the shear strength of discontinuities, reference tables are used to obtain the basic friction value for the lithology under study. These tables omit some lithologies complicating the search of adequate references. An alternative, straightforward and economical way to obtain ϕ b is through the field tilt test, which is carried out by sliding two blocks aside a joint. It is a well-known test, but there are few references to its implementation. In this test, unlike the laboratory tilt test, the samples are not “polished” and it is necessary to evaluate the roughness of the joint and the normal component to the weight of the upper blocks. The idea is to calculate the term of ϕ b from the Barton-Bandis’ equation and include the tilt angle α . Various tilt-test measurements were carried out with field blocks on both sides of the same joint, considering different lithologies (granite, limestone, andesite, dacite, coal and slate) and block sizes, evaluating the ideal ranges of applicability of the test.