DPSH testing to help identify founding conditions

Geomech Africa was contracted to conduct a DPSH investigation in Langebaan, Western Cape to help identify the founding conditions and levels for a three-storey residence. Previous DCP tests had not identified the details of the ground conditions with enough certainty and so more rigorous tests were required.

The test positions were situated on the steep (20’) slope overlooking the Mykonos Marina. The requirement was to conduct two tests at the top of the slope and a further two tests halfway down the slope. Given the access challenges, we opted to conduct the testing with our smaller more portable DPSH machine rather than our trailer mounted DPSH. This small portable DPSH machine allows access to small, restricted locations but in contrast to the larger trailer mounted unit, it requires more manpower.

Fortunately access to the two locations at the top of the slope was relatively simple and with some brute strength we were able to manoeuvre the portable DPSH machine onto position. The remaining two test were to be conducted 5m down a 20’ slope – not such an easy proposition.

With the assistance of an anchor line and a crew member stationed at each corner of the DPSH machine, we managed to slowly lower and guide the machine down the sandy slope onto the first location situated halfway down the slope. Once the test was completed, we shifted the machine through thick sands and groundcover some 4 meters to the next test location. Given that the testing conducted on this portable DPSH is largely a manual operation and given the site conditions, this was a physically demanding project.

With the final test completed it was now time to demobilise our DPSH machine and equipment from site. Our options were either try to haul this machine back up the slope through the thick sands and groundcover or to slowly lower and guide the machine down the balance of the slope to the bottom. The decision was taken to lower the machine down and rather drive our 4x4 vehicle around and across the sand to load all our equipment. After a taxing 2 hours of working in thick soft sands we were finally loaded and ready to leave site.

All four tests founded at similar levels and no large boulders were identified which would have impacted on the foundation design. The results were compiled and sent with a full project report to Cedric Brown at CTC Consulting Engineers West Coast. According to Mr Brown, “The Geomech Africa response was fast, with the tests being complete within a week of our initial enquiry and resulting in no delays to the project.”