Project 2

Compaction, strength reduction, and stress estimates in shocked porous sandstones

Project directors:

Thomas Kenkmann, Insitute for Geosciences, University Freiburg (ALU)
Georg Dresen, German Research Centre for Geosciences (GFZ)
Hans-Rudolf Wenk, Berkeley, CA, USA (BER)

Research staff:

Elmar Buhl (PhD student, GFZ/ALU)

Summary

The proposed project in the framework of the MEMIN program is devoted to better understand deformation processes and structural changes in porous sandstones in impact craters. The investigations comprise (i) the determination of strength properties of target rocks prior and after shock loading to infer the degree of strength reduction upon impact cratering. The compression of porous rocks by shock and pressure waves leads to substantial changes in the rock fabric.

We will investigate (ii) different modes of compaction including the localized pore collpase that could lead to the formation of compaction bands as a function of radial distance in the floor of laboratory produced impact craters. The results will be compared with compactive britte deformation features formed in quasi-static loading tests.

(iii) The state of damaging of impact-deformed rocks will be quantified by determination of the densities of micro-cracks and defects. These data will be related to elastic parameters that are gained from inversion of ultrasonic measurements obtained in Project 4. (iv) Finally, we intend to test and calibrate a novel natural pressure gauge, namely the formation of Dauphin√© twins, in shock deformed sandstones and determine the residual stresses of the rocks applying the novel synchrotron microfocus Laue diffraction technique. 

Results

You can find the results here.