Strength behavior of plain cement concrete subjected to true triaxial compression

True triaxial compression test was conducted on 100 mm x 100 mm x 100 mm cubical sample of plain cement concrete using the true triaxial testing machine. A total of 30 tests were conducted on two concrete mixes having characteristic strengths of 24.39 MPa and 34.67 MPa. The minor and intermediate principal stresses were varied from 2.5 MPa to 10 MPa and 2.5 MPa to 30 MPa respectively. The samples were loaded until failure under the stress rate of 1 MPa/min. The failure mode and direction of fracture planes were observed carefully. It was observed that the ratio of intermediate and minor principal stress had an incremental effect on the strength of the concrete. The results obtained from our experimental study as well as the true triaxial compression test data published in literature has been used to conduct a quantitative evaluation of three commonly used failure criteria presented for the concrete. The three failure criteria considered are Drucker-Prager (DP) criterion, Bresler-Pester (BP) criterion, and Hsieh-Ting-Chen (HTC) criterion. It was observed that for the normal strength concrete, the HTC criterion predicts the strength with least error while for the high strength concrete, the DP criterion gives better predictions. Overall the DP and BP criteria underestimate the strength while the HTC criterion overestimates.