Assistant professor, Northeastern University, Boston, MA
Staff geotechnical engineer, Sverdrup Engineering Services, Boston, MA
The paper describes the automation and calibration of a hydraulic Rowe consolidation cell that tests 151-mm-diameter by 60-mm-high specimens. The associated measurement instrumentation for the cell and specimen preparation procedures are also described. The cell was used to perform a set of one-dimensional constant rate of strain (CRS) tests at two vertical strain rates, 0.1 and 1%/h. The nonlinear CRS theory of Wissa et al. (1971) is presented, including methods for interpreting test results at higher strain rates. The results from the Rowe cell tests conducted on resedimented Boston Blue Clay are compared to those from more conventional incremental loading (IL) oedometer tests (63.5-mm-diameter by 23-mm-high specimens). For both the 0.1%/h tests (in which negligible excess pore pressure was generated at the undrained specimen base) and the 1%/h tests, the compression curves compare well with the baseline IL oedometer test curves. Values of preconsolidation pressure, σ′p, averaged 94.0 kPa in the Rowe tests and 94.5 kPa in the IL oedometer tests. The compression ratios, CR = Δεv/Δ log σ′v, in the virgin compression range were slightly lower in the Rowe cell tests (average 0.156 versus an average CR = 0.173 in the IL oedometer tests), which may be due to different testing conditions (e.g., back pressure in the Rowe cell) or the larger Rowe cell specimen. The coefficient of consolidation and hydraulic conductivity values computed from the Rowe cell tests are essentially identical with regard to stress level to the IL oedometer tests. The automated Rowe cell data indicate that the device offers a reliable and potentially rapid method for determining consolidation parameters, including hydraulic conductivity.
Paper ID: GTJ10713J