Figure 4. Photograph of the sensor array used to measure sample stress and strain in the triaxial cell. Lateral strains are measured by four pairs of LVDTs in a ring at sample midsection (1) and axial strains by a pair of LVDTs attached to rings spanning the central section of the sample (2). Axial stress is measured with a load cell mounted above the upper platen (3). Pore fluid can be drained from either or both ends of the sample (4) and compressional seismic transducers are imbedded in both platens (5).