Projects

Brown Field Sites

Push in instrumentation under an angle

One of the advantage of cpt rams are their versatility. We can make cpt's under any angle. Another use you can see on the accompanying photos is pushing in instrumentation under an angle. This makes otherwise awkward jobs relatively easy and mess free. We have carried out projects under buildings, railways, canals. Un unusual use was to survey the depth of the foundation of an old church by probing in a number of angles. In this case a detached set of rams is used using the hydraulics and counterweight of a truck. The detached set of rams can be used in all sorts of environments like cellars, tunnels and any place with limited access or headroom.

Flying High.....Pushing Deep

What do you do if you have a job beneath a rail bridge, with no access in or out; full of piles that can’t be touched and you need some ground investigation? You call Lankelma and their Minicrawler CPT rig!

Recently, Lankelma was approached to come up with a method of testing the ground beneath a railway bridge on the CTRL. The ground had been capped with concrete and grout pipes were sticking out of the surface which couldn’t be damaged. The underlying soils needed to be tested before it was treated with ground improvement methods, and then tested afterwards to verify that the ground improvement had worked.

Because of the access problems posed by the sites location, Lankelma sent its 3.5 tonne Minicrawler along to do the job. It was craned down onto the site using an onsite crawler crane. Once the rig had landed, it had to move carefully through the maze of pipes that covered the floor. Due to the rig only weighing 3,5 tonnes, extra reaction force was gained by bolting the rig down to the concrete floor.

The Mincrawler was able to carry out 5 tests over the two day period down to a depth of 5 to 10 metres.

The Minicrawler is a versatile CPT rig. Due to its size, it is able to work on sites where a standard CPT rig would not be able to gain access. With its multi-angle rams, it is designed for slope and embankment work. The reaction force of the rig can be increased by screw picks in the soil, bolting it down to concrete, or by adding kentledge weights.

Soil Moisture Probe (SMP)

The soil Moisture Probe (SMP) is installed directly behind the electric cone and permits the simultaneous acquisition of resistivity, soil moisture and geotechnical data. The SMP comprises two ring shaped and carefully isolated electrodes and an Application-Specific Integrated Circuit (ASIC). The ASIC uses synchronous detection for accurate measurements, free from electric interference Dielectric soil properties, capacitance and electrical conductivity, are governed mainly by the water content of the soil mass. By measuring these parameters between two electrodes, with the soil dielectric in between, the soil moisture can thus be determined.

The capacitance of dry soil is determined by its dielectric constant. For dry soil this constant is of the order of 3 to 6 and for water the constant is 80, that is, the capacitance between the two electrodes is dominated by the volume fraction of water.

In polluted soils non-aqueous phase liquids (NAPL’s), such as oil or chlorinated solvents, will replace part of the water in the soil matrix. As they do not dissolve easily in groundwater, they will occur as a film of pure product, often just above the groundwater table. Dense NAPL’s such as chlorinated hydrocarbons, which are denser than water, will penetrate the groundwater table and are typically found on top of impermeable layers. These pollutants affect the dielectric properties of the soil significantly and are detectable using the Soil Moisture Probe. Graph above of water content v. dielectric constant. By using this cone technique, time and cost can be saved.

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