Projects

Railways

The Complete Railway Site Investigation

Rail embankments are a common place to find problems with earth movement on the Rail Network. The investigation of these embankments to establish the problem can be as problematic as actually working out a solution.

Lankelma recently carried out an investigation to such a problematic site. The embankment was situated in Norfolk near to Diss. The embankment was roughly 6m high and constructed on a Peat Bog. It was these underlying soil conditions that were causing subsidence in the embankment.

The aim of the investigation was to find the properties of the material below the embankment, and to provide a profile through the embankment.

The investigation was carried out in two different stages. The first stage was to investigate the soil properties of the material below the embankment. This was done either side of the embankment at its toe. 11 PCPT’s were carried out on the east side and 9 PCPT’s were carried out on the west side.

Lankelma’s 15 tonne crawler unit was used for the entirety of the works. On this first stage of the works the crawler was best suited to the ground conditions. As it was a boggy site a wheeled vehicle could not be used. The crawler, with its low ground bearing pressure was able to reach all parts of the site.

The depth of the PCPT’s were 20m, with some going down to 30m depending on the client’s instructions. At four locations MOSTAP soil sampling was carried out. This system was advantageous for two main reasons. The first being that there was no need to mobilise another piece of equipment as the CPT Rig was already on site, saving money. The second was because of the high quality samples that you can get from this type of push sampling.

The sampling went down to maximum depth of 20m, into the competent Chalk. The samples were 65mm diameter and 1m long. All samples were taken from the site to a local laboratory.

Due to the nature of the job being on an embankment, monitoring was required to assess what was happing to the water regime over a period of time and during remediation works. The PCPT results were assessed the following day from when the test was carried out to decide where to place the piezometers.

Eight vibrating wire piezometers where installed along the toe of the embankment at varying depths. They were installed by pushing them to the required depth and then were left in the ground. Bentonite was placed in the hole to prevent creating an artificial pathway. These are being monitored every two weeks.The second stage of the investigation was to carry out CPT’s at the top of the embankment on the track. This was carried out with the same CPT rig that is especially designed to work on the rail network. This stage of works was carried out during Saturday night possessions.

Over a three-weekend period, 10 CPT’s were carried out to a depth of around 15m.

This case study shows how best suited CPT’s are to the rail industry. Due to their high quality, speed and quick turn around with results, CPT’s can be adapted to the constraints of short possession times and restricted access issues.

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.

Lankelma - Approved Rail Supplier

Lankelma is now a rail approved supplier under the Link Up Scheme. For more information contact us.

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