A new method of measuring deformations in diaphragm walls and piles

A novel portable strain measuring device called the sliding micrometer iseth has been developed. The continuous direct measurement of strain along one or more straight lines is possible using the device. A hard pvc tube is connected into the structure containing steel ring-shaped measuring marks at 1 M intervals. The rings contain stops to hold the two heads of the portable device in position during readings. A linear displacement transducer is used to determine the relative displacement of the measuring marks as a measure of the strain in the surrounding concrete. The instrument with a base length of 1 M has an accuracy of strain measurement in the field of better than 3 microns. The linearity of the inductance transducer can be checked by using a calibration frame before and after any set of measurements. Examples are given showing how the apparatus can be used to determine the strain distribution, curvature and deflection of axially and laterally loaded piles and the strain distribution and curvature of a diaphragm wall at the excavation stage. A load-settlement diagram is given for top and bottom of an axially loaded pile. (TRRL)