Deformation modulus determination from pressuremeter and dilatometer tests for crystalline rock

The deformation modulus is an important characteristic of the mechanical behaviour of rock mass. The deformation parameters of rock mass may be obtained by execution of in-situ tests. In situ testing comprises the most reliable and comprehensive methods to describe the mechanical behaviour of the rock mass. Results of pressuremeter and dilatometer tests for crystalline rocks and their interpretation are presented in the paper. Comparison of two types of in-situ geotechnical tests results was analysed based on ground investigation for new expressway in Slovakia. In the evaluated section, an extensive part of the expressway is situated on bridges. During geological investigation, 161 of dilatometer and 150 of pressuremeter tests were carried out to determine rock parameters. Logging measurements were conducted in each borehole in advance of geotechnical testing to select the best testing section of the borehole. Consequently, the pressuremeter and/or dilatometer tests were performed in selected boreholes. It was observed that the difference between deformation modulus determined by dilatometer and pressuremeter tests are significant especially for intact rock with high value of Rock Quality Designation (RQD). Correlations for estimating rock deformation parameters were derived based on analysis of the results from dilatometer and pressuremeter in-situ testing of crystalline rocks.