A Smarter Alternative for Launch Pits, Receiving Pits and Tank Excavations
For deep pits and large excavations, sheet piling has often been the go-to solution. On the right project, slide rail can be faster, lower-vibration and more cost-effective.
Sheet piling has been the default for deep pits for a long time. Bring in a piling contractor, drive the sheets, dig it out. It works, but it also brings a rig, a crew, a vibration exclusion zone and a mobilisation cost before the bucket goes in the ground.
Legend Hire’s Slide Rail Shoring System is built for deep excavations, launch and receiving pits, pump stations, large tank installations and other jobs where you need strong ground support without the complexity of traditional sheet piling. The system is installed progressively as the excavation advances, giving continuous wall support and helping minimise ground movement.
Here’s how it works, and how to tell whether your excavation is a fit.
What is slide rail shoring?
Slide rail shoring is a modular ground support system built from steel posts and steel panels. The posts have a double guideway and the panels slide down inside it. Instead of installing the shoring first and digging second, both happen together, dig down in stages, push the panels lower, repeat until you reach depth.
Legend Hire runs a double slide rail system using 3.0 m and 5.5 m panels with corner and rolling struts, so box sizes and pit shapes are built to suit the excavation rather than the other way around.
Shore as you dig
The installation method is the part that changes how the job runs.
There is no separate shoring stage. The excavator digs down in stages, the rails and panels are pushed lower as the excavation advances, and the walls stay supported the whole way down. The excavation is not left open and unsupported waiting on plant or a subcontractor.
Two things follow from that. Ground movement stays under control, because the soil is never given the chance to relax into an open cut. And nobody works next to an unsupported face.
No piling rig, no piling crew
Driven sheet piling needs specialist plant, a piling rig, plus vibratory or impact equipment to drive with. That means a separate contractor, a separate mobilisation and a separate line on the program.
Slide rail is installed from the surface with an excavator, on most jobs, a machine that’s already on site.
On tight urban sites, that difference is often the whole argument. If a rig can’t get through the gate, or a second mobilisation can’t be justified on a short-duration pit, slide rail avoids the problem.
Why lower vibration matters
Driving sheets sends energy into everything around the excavation. Slide rail panels are pushed rather than hammered, which reduces vibration compared with driven sheet piling.
That’s worth checking on any site near:
- existing buildings and heritage structures
- live underground services
- roads and rail infrastructure
- other vibration-sensitive structures, plant or equipment
- confined urban sites and neighbouring properties with dilapidation reports in place
Where a vibration monitoring regime is already making sheet piling difficult, slide rail is usually the next system worth assessing.
Clear-span excavation, getting the struts out of the way
Conventional strutting creates a problem of its own. The excavation is well supported, but the precast tank or structure now has to be lowered through a grid of cross struts.
Legend Hire can engineer a clear-span slide rail configuration using a top clamping device and a bottom support known as a lost beam.
The clamping device locks the posts and panels together above ground, keeping the system square and rigid at the top. At the bottom of the excavation, the lost beam ties the opposing rails together and transfers load through the excavation floor. Between them, they take on the work the cross struts would have done — from above and below, rather than through the middle.
The result is an open working area. Room to land large tanks and precast structures, run boring equipment, place pump station components and large-diameter pipe, and carry out lifts without threading loads through steelwork.
Clamping device and bottom support: a worked example
A worked example of a clear-span configuration, how the components lock together to brace a wide excavation with no cross strut across the opening.
Clamping device and beam
A beam-mounted clamp locks each slide rail post to the panels above ground, holding the whole frame square and rigid as the excavation goes down.
Bottom support – lost beam
At the base, a lost beam ties the opposing rails together and transfers load through the excavation floor. It’s sized to the static requirements of each project.
Plate and double slide rail
Steel plates slide inside the double rail’s guideway, giving continuous groundside support the full depth of the trench, up to 6.5 m of rail in this example.
In the arrangement drawn above, a trench roughly 4.8 m wide gives a working width of about 3.8 m, and around 4.2 m between the plates, at a trench depth of approximately 4.5 m. No cross strut crosses the opening at any point.
These are the figures for this particular configuration, not the limits of the system. Panel lengths, rail arrangement and the lost beam are engineered to each excavation.
Slide rail vs sheet piling at a glance
| Slide rail shoring | Driven sheet piling | |
| Plant required | Excavator already on site | Piling rig, vibratory or impact hammer |
| Specialist crew | Not usually | Piling contractor |
| Installation method | Progressive dig-and-push | Driven ahead of excavation |
| Vibration | Low | Significant |
| Working area | Clear span achievable | Depends on bracing design |
| Removal | Panel by panel during backfill | Extracted with rig |
| Components | Modular, reusable | Often left in place or extracted |
| Best suited to | Launch and receiving pits, tank installations, pump stations, deep pits | Very deep walls, permanent works, water-retaining applications |
Slide rail won’t replace sheet piling everywhere. Some excavations need sheet piling, secant piles or another engineered system, and the geotechnical information will point to which. But on a lot of pits, the shoring method gets specified out of habit rather than assessment
Where slide rail earns its keep
Bore launch and receiving pits. A large supported excavation with clear access for boring equipment, pipework and lifting. This is the application slide rail is best known for.
Tank and vessel installations. A clear-span configuration means the tank can be lowered into an open pit.
Pump and lift stations. Room to sequence precast components and services without working around bracing.
Large-diameter pipelines. Panel and strut arrangements can be configured to suit large pipe and culvert sections; our temporary works team will confirm achievable clearances for your pipe diameter.
Deep excavations in poor ground. Because the walls are supported as the dig advances, slide rail can handle ground that would be difficult to hold in an open cut. Legend Hire has run the system successfully in sandy conditions where progressive support was the reason the method worked, the steel plates slide within the double rail guideway and provide continuous groundside support through the depth of the excavation.
Our Newcastle underground water tank project is a good example: high groundwater, a constrained site, and a stable, compact excavation held with a modular slide rail system.
Getting it back out again
Installation gets most of the attention, but removal is where deep excavations can cause trouble.
A large trench box can be difficult to extract from a deep excavation because of ground pressure and suction across the full panel area, and there’s usually only one attempt at pulling it in one piece.
Slide rail comes out progressively. Panels are extracted one at a time as the excavation is backfilled, so the full panel area is never being broken free at once. Legend Hire also has extraction tools available to help break suction and assist removal on deeper excavations.
What you actually save
On a suitable launch pit, receiving pit, tank installation or deep excavation, the savings tend to come from a few places:
- Faster installation. shoring happens during the dig, not before it
- One mobilisation. no separate piling contractor or rig
- No specialist plant hire. the excavator on site does the work
- Progressive excavation and shoring. one operation instead of two stages
- Lower vibration. fewer restrictions, less monitoring, fewer neighbour issues
- Clear working area. no lost time sequencing lifts around struts
- Simple removal. panel by panel, during backfill
- Reusable modular components. hire what the pit needs and return it