fig 1
fig 2
The video cone was used to confirm depth of the contact between the sand and gravel and the highly weathered Chalk, which is sometimes hard to distinguish from normal CPT's. The results from using the video cone can be of economical importance saving a true indication of the amount of grout needed, and importantly reducing the danger of under grouting so eliminating chances of a costly failure. Figures 4, 5 and 6 show the different soils.
fig 4: Sand
fig 5: Clay
On Thursday 18th April Lankelma CPT Ltd demonstrated the future in cone penetration testing, the video cone. The cone, developed by GeoDelft, uses a small video camera mounted in the side of the cone with a halogen light behind sapphire glass to record a constant image as it is pushed into the ground, see figure 1.
The resulting imagery gives you a clear undisturbed picture of the ground with 7 times magnification allowing you to see individual grains and colours of the material.
The demonstration was carried out on a site where there are large solution features in chalk in filled by sand and gravel. The solution features are to be grouted to improve their stability, see figure 2.
Conventional CPT's were used to profile these large features (some up to 30m in length), see figure 3
fig 3
fig 6: Chalk
