Detailed Modelling of discontinuity roughness in UDEC

1993. Detailed Modelling of discontinuity roughness in UDEC / by Bernice, A.M. Baardman. - Delft : TUD, 1993. - 109 p. ; 30 cm. - Technical University Delft MSc-thesis. ABSTRACT, supervisor: Hack, thesis availability: Technical University Delft

ABSTRACT

In this research a recently failed slope and shearbox tests on six rock samples have been modeled in UDEC with the purpose of finding a 'UDEC roughness angle'. Additionally the roughness of the six samples has been described in various ways among which parameters Rp, Z2, and i at various sample intervals. These descriptions have been compared to the results of laboratory shear tests at very low normal loads.

UDEC is a two dimensional numerical program for discontinuous rock mass modeling. To model the roughness in UDEC the slope and the shearbox samples have been scanned with a newly constructed laser profile meter, the achieved accuracy is 0.1 mm in both horizontal and vertical direction. An acceptable way of processing the output data of the laser profile meter has been developed.

Slope modeling resulted in a stable slope at a joint friction angle of 1 deg, implying a UDEC roughness angle larger than the slope dip. Cause of this unrealistic result might be that the data had to be modeled in a wrong way, i.e. as a matched joint and as rigid material. Shear test simulations resulted in UDEC roughness angles for some samples but the found values depend strongly on specified input parameters as joint stiffness and shear velocity.

Of the various roughness descriptions the descriptions according to the Detailed Rock Mass Classification System corresponds best to shear strength at very low normal loads while tilt test results and dilations angles do not show a very good correlation. Further it has been demonstrated that the roughness parameters Rp, Z2, and i strongly depend on the sample interval at which they are determined; a sample interval of 2 mm seems to give best correlation to shear strength at very low normal loads.