On-Specimen Measurement

The GCTS Soil Deformation Devices (DEF-AXC Series & DEF-SRCP Series) measures axial and average radial strain directly on a specimen, providing extremely accurate measurements. The DEF-AXC Series consists of upper and lower LVDT support rings that can be used with submersible or standard LVDTs. The Transducer supports are split in two halves, clamped using rubber bands and guided in order to prevent rotation or “folding” while allowing for lateral expansion. For soft specimens, the clamps can be set onto the top and bottom platen to prevent damage to the specimen.

The DEF-SRCP Series consists of a circumferential roller assembly made with anodized aluminum links and Teflon rollers to ensure smooth displacements. This material combination has a small mass and high stiffness to minimize device compliance. The DEF-SRCP includes an integrated submersible proximity sensor with 5 mm range. The standard DEF-SRCP can be configured to accommodate specimens with an initial diameter from 35 mm to 75 mm by adding or removing assembly links. Additional links can be purchased to accommodate specimens with up to 150 mm in diameter.

The GCTS Large-Scale Deformation Device (DEF-SRCP-600) is composed of two, three, or four DEF-S1610 Axial Deformation Gages and one or two DEF-SRCP-600 circumferential deformation gauges. Each DEF-S1610 includes one LVDT holder with a 150 mm radius, one road extension holder with the same radius, and one rod extension for measuring the axial strains. This device measures the axial strains within the middle half of the specimen height to avoid platen end effects. The two holders are attached to the specimen using tension springs and are guided by a precision bearing and light shaft to maintain parallelism. Different size extension rods are available from GCTS to measure axial deformation over different gauge lengths. Several DEF-S1610 devices can be installed in one specimen to measure the average axial deformation. The standard DEF-SRCP-600 device includes a 10 mm (0.4 inch) range water-submersible LVDT. This LVDT can be positioned in three different locations on the device to provide three different deformation ranges. These 3 different mechanical ranges translate roughly to 10%, 2.5% and 1% radial strain ranges on a 300 mm diameter specimen.