Lime cement columns

At the request of Keller Ground Engineering, Lankelma carried out a phase site investigation as part of the installation and testing of lime cement columns at Tilbury Docks, SE England.  The columns were installed as the gound improvement system for this particular site.


Tests

The works comprised cone penetration tests, mostap sampling through previously installed lime cement columns and pull-out resistance tests (PORTs) using a wing cone.

CPTs were used to determine the engineering properties of the lime cement columns.  Continuous 65mm diameter Mostap samples were obtained for subsequent laboratory testing by the Client.

Pull out resistance

At selected column locations, 500mm wide wing cones were installed at the base of the columns with attached pull-out cables run out to ground level. 

Following the column curing, one of Lankelma’s 20 tonne crawler units, with modified 20 tonne capacity hydraulic rams, was used to connect up to the cable and pull the flat vane to ground surface.

As with CPTs, the force required to pull the vane through the column back to ground surface was recorded and downloaded using a modified and calibrated pressure gauge, data logger and logging software.


Results

The results obtained were used to determine the undrained shear strength (and so working strength) of the individual lime cement columns tested.  The net pressure was determined by dividing the net force used to retract the wing cone by its cross-sectional area.   A factor of 0.1 was then applied to derive the undrained shear strength profile for the column.