VISION CONE PENETROMETER FOR DIRECT SUBSURFACE SOIL OBSERVATION

The cone penetration test (CPT) has gained wide acceptance for geotech nical site characterization and measurement of mechanical soil propert ies in situ. However, unlike the standard penetration test (SPT), soil specimens are not obtained in the CPT. Therefore, the soil type can o nly be estimated through empirical correlations with CPT sounding data or by retrieving field specimens adjacent to the test location. This technical note describes a new vision cone penetrometer (VisCPT), whic h permits observation and recording of subsurface images in real time as the VisCPT is pushed into the ground at the CPT standard advance ra te of 20 mm/s. A high- and low-magnification miniature charge-coupled device (CCD) camera system housed within the VisCPT provide images wit h fields of view of 2.3 and 18 mm, respectively (measured diagonally). A field video recording system allows the video sequence from each ca mera to be recorded in real time on two super VHS (S-VHS) format video recorders. Examples of images acquired in situ are presented.