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| Titel |
Assessment of rock properties and slope stability at Pacaya Volcano, Guatemala |
| VerfasserIn |
Lauren Schaefer, Jackie Kendrick, Thomas Oommen, Yan Lavallée |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250092097
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| Publikation (Nr.) |
 EGU/EGU2014-6422.pdf |
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| Zusammenfassung |
| Pacaya is an active stratovolcano located 30 km south of Guatemala City, Guatemala. A large
(0.65 km3) sector collapse of the volcano occurred 0.6 - 1.6 ka B.P., producing a debris
avalanche that traveled 25 km SW of the edifice. The structural setting of the current cone,
along with two recent smaller-volume collapses in 1962 and 2010, suggest gravitational
instability of this volcano. Recent measurements of the geomechanical properties of lava and
breccia from Pacaya are used to improve our understanding of the destabilizing potential of
different volcanic processes. Room-temperature uniaxial and triaxial compressive tests, and
total porosity tests, were conducted on 17 breccia and 21 lava samples. The average
uniaxial compressive strength (Ïăci) of lava rocks was moderately strong (Ïăci = 72.4
MPa), with breccia rocks being 62.2% weaker (Ïăci = 27.4 MPa). These values can
partially be contributed to lava rock’s very low porosity (0.054) and breccia rock’s
higher porosity (0.19). We also find an apparent rate-dependent strengthening of the
samples as strain rate is increased from 10-5 to 10-1. Values of Poisson’s Ratio
(v) and Young’s Modulus (E) calculated from triaxial tests, are v= 0.28 and E =
13.9 GPa for breccia and v= 0.31 and E = 17.6 GPa for lava. These experiments
highlight the contrasting character of breccia versus lava, and suggest that sector
collapse may have initiated in the weaker breccia. Additionally, cohesion (c) and
friction angle (Ï) calculated from triaxial tests yielded values of c = 1.8 MPa and Ï
= 19.4° for breccia and c = 4.0 MPa and Ï = 41.4° for lava. Following sector
collapse, the frictional properties of the rocks partially dictate the flow and deposition
of the debris avalanche, and these were studied using high velocity rotary shear
experiments on ash and lava rock. Experimental results are combined to understand the
historical flank stability and assess the likelihood of future sector collapse at Pacaya. |
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