Bodenmechanische Charakterisierung der Scherfestigkeit von Braunkohlen des Mitteldeutschen Reviers

Characterisation of shear strength of brown coal from central Germany

This paper deals with experiments which were performed to determine the shear strength parameters of different varieties of Brown Coal (lignite) from central Germany. Object of investigation were the lignitic coal varieties with fragmentary structure (Yellow Coal and Brown Coal) of seam 23 in the Profen/Schwerzau mine and the compact coal of seam 1 in the Profen mine. The determined shear strength values were aimed at verifying the parameters used for stability analysis so far as well as for determining possible differences in shear strength between the Yellow Coal and Brown Coal varieties. An experimental program was realized including triaxial and in-situ shear tests. The sampling and the specimen preparation for laboratory testing required special measures due to the sensitive structure of the coal variety with fragmentary fabric. The shear strength of the variety Yellow Coal and Brown Coal was found to be nearly identical. However, the shear strength as determined from triaxial tests and in-situ shear tests differ from each other, which can be explained by the different structure of the material tested (small-fragmentary structure versus medium/large-fragmentary structure) at the one hand and by the different boundary conditions during the test.