Miniature LVDT setup for local strain measurement on cement-treated clay specimens

ABSTRACT

Miniature submersible linear variable differential transformer (LVDT) is commonly used for small strain stiffness measurement. However, it has not been widely used on cement-treated clays. This paper proposes a method of installing and setting up submersible LVDT to minimize testing problems and errors for cement-treated clays. In soft clay testing, the LVDT mount can be anchored to the specimen by pressed-in anchor pins or rods. However, this cannot be done on cement-treated clay due to the latter’s hardness. Preliminary trials also indicate that direct attachment of the LVDT mounts to the membrane without anchor pins is not feasible owing to the tendency of the LVDT to tilt and detach from the specimen. The system adopted involves pre-casting holes for the insertion of anchor pins during placement of the admixture into the moulds. The diameter of the anchors pins was found to have significant effect on the results; smaller diameter pins give more consistent results with those of resonant column and bender element tests. This can be attributed to the effect of stress concentration around the anchor pins. The results showed that, used appropriately, submersible LVDTs can give small strain measurements which have a high degree of inner consistency with results from resonant column and bender element tests.