Damage and rupture dynamics at the brittle-ductile transition: The case of gypsum

被引:81
作者
Brantut, N. [1 ]
Schubnel, A. [1 ]
Gueguen, Y. [1 ]
机构
[1] Ecole Normale Super, Geol Lab, CNRS, UMR 8538, F-75231 Paris 05, France
关键词
PORE PRESSURE EXCESS; ACOUSTIC-EMISSION; DEHYDRATING SYSTEM; DEFORMATION; EARTHQUAKES; ROCKS; PROPAGATION; EVOLUTION; FRACTURE; STRESS;
D O I
10.1029/2010JB007675
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
Triaxial tests on gypsum polycrystal samples are performed at confining pressure (P-c) ranging from 2 to 95 MPa and temperatures up to 70 degrees C. During the tests, stress, strain, elastic wave velocities, and acoustic emissions are recorded. At P-c <= 10 MPa, the macroscopic behavior is brittle, and above 20 MPa the macroscopic behavior becomes ductile. Ductile deformation is cataclastic, as shown by the continuous decrease of elastic wave velocities interpreted in terms of microcrack accumulation. Surprisingly, ductile deformation and strain hardening are also accompanied by small stress drops from 0.5 to 6 MPa in amplitude. Microstructural observations of the deformed samples suggest that each stress drop corresponds to the generation of a single shear band, formed by microcracks and kinked grains. At room temperature, the stress drops are not correlated to acoustic emssions (AEs). At 70 degrees C, the stress drops are larger and systematically associated with a low-frequency AE (LFAE). Rupture velocities can be inferred from the LFAE high-frequency content and range from 50 to 200 m s(-1). The LFAE amplitude also increases with increasing rupture speed and is not correlated with the amplitude of the macroscopic stress drops. LFAEs are thus attributed to dynamic propagation of shear bands. In Volterra gypsum, the result of the competition between microcracking and plasticity is counterintuitive: Dynamic instalibilities at 70 degrees C may arise from the thermal activation of mineral kinking.
引用
收藏
页数:19
相关论文
共 60 条
[51]  
Tarantola A., 2005, INVERSE PROBLEM THEO
[52]   Premonitory acoustic emissions and stick-slip in natural and smooth-faulted Westerly granite [J].
Thompson, B. D. ;
Young, R. P. ;
Lockner, D. A. .
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 2009, 114
[53]   Observations of premonitory acoustic emission and slip nucleation during a stick slip experiment in smooth faulted Westerly granite [J].
Thompson, BD ;
Young, RP ;
Lockner, DA .
GEOPHYSICAL RESEARCH LETTERS, 2005, 32 (10) :1-4
[54]   Fracture in Westerly granite under AE feedback and constant strain rate loading: Nucleation, quasi-static propagation, and the transition to unstable fracture propagation [J].
Thompson, Ben D. ;
Young, R. Paul ;
Lockner, David A. .
PURE AND APPLIED GEOPHYSICS, 2006, 163 (5-6) :995-1019
[55]   WEAK ELASTIC-ANISOTROPY [J].
THOMSEN, L .
GEOPHYSICS, 1986, 51 (10) :1954-1966
[56]  
Tullis J., 1992, FAULT MECH TRANSPORT, P89, DOI DOI 10.1016/S0074-6142(08)62816-8
[57]   DEFORMATIONAL KINKS IN BRUCITE AND GYPSUM [J].
TURNER, FJ ;
WEISS, LE .
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 1965, 54 (02) :359-&
[58]   Dehydration reactions and micro/nanostructures in experimentally-deformed serpentinites [J].
Viti, Cecilia ;
Hirose, Takehiro .
CONTRIBUTIONS TO MINERALOGY AND PETROLOGY, 2009, 157 (03) :327-338
[59]   Acoustic emission in single crystals of ice [J].
Weiss, J ;
Grasso, JR .
JOURNAL OF PHYSICAL CHEMISTRY B, 1997, 101 (32) :6113-6117
[60]   Generation and maintenance of pore pressure excess in a dehydrating system .2. Theoretical analysis [J].
Wong, TF ;
Ko, SC ;
Olgaard, DL .
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 1997, 102 (B1) :841-852