Project Details
Projekt
Fully automatic large-scale rock shearing machine in a cold chamber
Subject Area
Geography
Term
Funded in 2023
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 524663687
Globally, degrading permafrost in high alpine rock faces leads to a sharp increase in rockfall, rock avalanches, and also large landslides. We presented a comprehensive rock-ice mechanical model in 2013 that includes the (i) rock mechanical, (ii) ice mechanical, and (iii) mechanical changes at the rock-ice interface. To parameterize the rock-ice mechanical model for (i) different lithologies, (ii) different pressure and temperature conditions, (iii) relevant deformation mechanisms and velocities globally, we need a shear device that can comprehensively simulate (i)-(iii). We have published >40 articles with field and laboratory preliminary tests on rock freezing behavior, often with self-modified laboratory devices, and are a leading international research group in this field. For universal applicability of the rock ice mechanics model, we need a (i) large-scale cold shear test system, with (ii) freely scalable deformations and loads, (iii) the capability for trajectory-dependent long-term creep tests (iv) with cyclic temperature changes and simultaneous measurement of (v) key geophysical parameters. The central object of this procurement activity is a fully automated rock shear tester to determine shear strengths, creep properties, and cyclic material fatigue of rock, rock/ice specimens, and other naturally occurring, predominantly frozen materials that have significant relevance to slope movement. In addition, unconfined compression tests and indirect tensile tests will be possible. For accurate control of the frozen specimens, it is necessary to place the instrument in a cold chamber with thermal dynamic trajectories (down to about -20°C). Since scale effects are relevant, it should be possible to test specimens up to 300 x 300 x 200 mm. In addition, smaller specimens can be tested in a rock shear device in the cold chamber with max. 100 kN to increase efficiency. The shear force of 500 kN and normal force of 1000 kN and the thermal conditions place special demands on the rigidity and strength of the test frame in order to be able to measure translations in the 0.01 mm range, at shear rates of up to 500 (1000 kN) and 2000 mm/min (100 kN). At the same time, acoustic emission, P- & S-waves, and in the future also the electrical self-potential/resistivity, have to be measured. The tests, which can last up to one month, and the samples, which are difficult to obtain (high mountains, Arctic), require a high level of process reliability, which is guaranteed with the machine described.
DFG Programme
Major Research Instrumentation
Major Instrumentation
Vollautomatisches Großfelsschergerät in Kältekammer
Instrumentation Group
2940 Spezielle Baustoff- und Bodenprüfgeräte, Schergeräte
Applicant Institution
Technische Universität München (TUM)
