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| Titel |
A new state-of-the-art tool to investigate rock friction under extreme slip velocities and accelerations: SHIVA |
| VerfasserIn |
André Niemeijer, Giulio Di Toro, Stefan Nielsen, Piergiorgio Scarlato, Gianni Romeo, Giuseppe Di Stefano, Steven Smith, Fabio Di Felice, Sofia Mariano |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250034883
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| Zusammenfassung |
| Despite considerable effort over the past several decades, the mechanics of earthquakes
rupture remain largely unknown. In order to complement fault drilling projects and field and
seismological observations, recent friction experiments strive to reproduce as closely as
possible in-situ (natural) conditions of slip velocity and acceleration on intact and fault
rocks.
In this contribution, we present a novel state-of-the-art experimental rotary shear
apparatus (SHIVA or Slow to HIgh Velocity Apparatus) capable of shearing samples at
sliding velocities up to 10 m/s, accelerations of ~ 40 m/s2 and normal stresses up to 50 MPa.
In comparison with existing high speed friction machines, this apparatus extends the
range of sliding velocities, normal stresses, sample size and, more importantly,
accelerations.
The apparatus consists of a pair of brushless electric motors (a low velocity motor,
10-6-10-3 m/s, power 5 kW, and a high velocity motor, 10-3 – 10 m/s, power 270
kW), that are connected by a gear system that allows a switch between motors
without loss of velocity and force. The motors drive a rotary shaft which clamps
ring-shaped samples (diameter 40- 50 mm). On the other side of the rotary shaft,
a stationary shaft holds the other half of the sample assembly. The shaft is held
stationary by a pair of stainless steel arms, one of which is attached to the side of
the concrete-filled base where torque is measured by a tension cell. Axial force
(maximum 37 kN) is applied on this side by a piston-cylinder couple with an arm to
increase the force. The entire machine measures by 3.5 by 1.2 meters and weighs 3700
kg.
We aim to perform experiments on rock samples of a variety of compositions using slip
velocities and accelerations that simulate slip velocity functions that occur during
earthquakes. In addition, we plan to develop a pore fluid system and a pressure vessel in order
to perform experiments that include the physical-chemical processes that occur
during slow interseismic periods. Moreover, experiments will be run where we
control the shear stress rather than the shear displacement. By doing so, we will
be able to simulate the transient load variation expected during seismic failure on
natural faults and measure the related dynamic weakening, frictional evolution and
slip velocity on the sample. The characterization of rock frictional behavior under
combined conditions of low to high slip velocity and extreme and rapidly variable
load, is expected to provide important insights into the mechanics of earthquakes. |
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