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Published By Lankelma

Lankelma is the foremost contractor for onshore in-situ soil testing in the UK. An acknowledged specialist in CPT, Lankelma also offers a worldwide consultancy and training service.

A.P. van den Berg develops, designs and manufactures geotechnical and environmental soil investigation equipment for onshore and offshore applications. Specialists in CPT systems and equipment.


Gardline Geosciences offers worldwide marine geotechnics, in-house consutancy and services with marine investigations ranging from nearshore to full ocean depth (down to 3000m).

About the Author

Hans Brouwer studied civil engineering at Delft University in The Netherlands. He has worked as a part-time lecturer at Amsterdam Polytechnic and was senior partner in a structural engineering consultancy. He has written a standard textbook in Dutch about the design of building foundations. He now lives in England where he writes technical textbooks in English, hopefully to reach a bigger readership.

Chapter 8

Push technology in the rail environment

Rail-specific rigs


A crawler is a very versatile rig in the rail environment. It can be used both on and off the rails and at the base of embankments. It can carry out sampling and CPTs. 
The rig has a high-lift jacking system which allows it to work on steep inclines. The rig can work at angles of up to 40° (Figure 68).
The crawler can also be mounted on a rail trailer to carry out CPTs in the 4-foot ballast bed. With its rear jacks, it can lift itself up to allow a trailer to be positioned beneath it.
Once mounted on the trailer, the rig is pulled by a road railer with the test being made through a hole in the trailer (Figure 69). It takes approximately 50 minutes to mount the rig onto the trailer and 30 minutes to take the rig off. A test down to 10 m will take approximately 30–40 minutes to carry out.

This rig is specially designed to work on steep embankments and restricted access areas (Figure 70). This means that there are plenty of uses for it in the rail environment.
The rig has specially designed rotation rams which allows it to carry out vertical CPTs on any slope it can negotiate. It can carry out inclined CPTs through the embankment with the system; and it has a winch system to help it get up the steeper slopes where traction becomes a problem.
It also has a screw pick system to allow it to screw itself into the ground to gain extra reaction. It is reaction that this rig lacks so to use on jobs that need a deep penetration you either have to increase the reaction by the screw picks or by putting extra weight on it.
The productivity of this rig is slower compared to the bigger rigs because of putting on and taking off the extra reaction ballast every time between tests.
The big advantage of this unit over the other rigs is its size. It is able to adapt to the cess (the shoulder of the track  ballast), and to travel up and down the cess with ease. It’s also small enough to fit where there are height restrictions.
An example of this was a job on the Channel Tunnel Rail Link where a ‘normal’ CPT rig could not get access so the mini-crawler was craned into position. Extra reaction was gained by screwing into the underlying concrete (Figure 71).  

Lightweight CPT unit
This rig was specially designed for use within rail tunnels. It was designed in conjunction with Tube Lines to work on their tunnel assessment projects.
It is designed to be half the size and weight of a standard set of CPT rams. This allows it to be carried by two people to the CPT locations.
The rig gets its reaction force from bolting onto a surface, either on a tunnel wall, the floor and specially constructed frames (Figure 72).
Using this method the CPT unit enables tests to be carried out horizontally. Due to the light weight nature of the rig, it can be mounted in any orientation as long as it can gain a reaction force from it.
The rig has been used across
the London Underground system and also in a twin track rail tunnel in London.


Excavator mounted rig
This new purpose-built CPT rig has been designed to overcome many of the problems found in the rail infrastructure. The CPT rams are fitted to the end of any excavator.
The rig has been designed to be used on rail tracks (Figure 74). The rig has a total reaction force of 10 tonnes, the CPT ram frame weighs 1.5 tonnes and the excavator provides the other 8.5 tonnes. It can also be used inside tunnels, pushing horizontally or even vertically upwards using a swivel hitch.
The rig, when mounted on the rail excavator, has a maximum reach of 6 m. The 10 tonnes reaction can be achieved at full reach and at any angle from the rig (Figure 75).
The CPT rams use the hydraulic system and electrical power of the rig making it selfcontained when mounted. The rig is fully assembled before the start of the shift so it is ready to travel straight to site when on track.
When mounted on the rail bug, the CPT rig is able to be used on the over-ground sections of the London Underground. The rail bug is approved to be used by both Tube Lines and Metronet.
The rig was designed with the help of Hydrex, the nationwide road–rail rental specialists. As Hydrex is based all over the UK, it enables it to keep down the mobilisation costs of this plant.
The rig is approved to be used in Network Rail. It is undergoing approval from Tube Lines and Metronet for use on the London underground system.  


One of the biggest innovations in rail-site investigation is a purpose built road-rail CPT unit. It is called The rail-truck. It has a reaction force of 19 tonnes which is more than enough for most rail sites. The unit has a central turntable mechanism which lifts the whole rig in the air and allows it to be rotated through 360° (Figure 77). This means it can easily gain access to rail tracks at most access points.
The rig is hydraulically driven by its rail wheels so that it can go as fast backwards as it can forwards. It also has a rear driving position, which enables it to be driven backwards safely, and is designed to fit inside a W6a gauge; this allows it to work in all parts of Network Rail and be isolated from electrical power sources.
Due to the nature and time constraints of rail work, the rig has been designed to be multifunctional so as to cut down on costs and reduce the numbers of possessions.
The rig will be allowed to carry people in the main cabin, cutting down the time to get operatives to a location. It has hydraulic and electric take off points to allow ballast sampling to be carried out during testing/CPT.
The rig has provision for a GPR system or differential global positioning system (DGPS) to obtain positional data for each test.
Figure 77 shows how the rail-truck is positioned for lowering onto the rail. The central turntable raises the whole rig, turns it so that the rail wheels are positioned above the rail, and then lowers it (Figure 78). 
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