Trenchbox Shoring

Series S100   Series S600   Series S300 Spindle Unit

General

The TWF trench boxes are a mechanised trench shoring system for nearly all sites and ground conditions and offer maximum performance in depths from 2-4 m. The trench boxes are manipulated, installed and extracted by a hydraulic backhoe excavator of 20-30 tons operating weight. Shoring plates are available in various lengths and heights for trench depths up to 6200 mm (depending on ground conditions). The standard sizes of different trench box systems as well as the clear head room below the bottom strut are as follows:

Main parts:

One trench box consists of following main parts:

• Trench box plates (base plates and top plates)
• Spindles with mushroom fittings, pins and spring clips
• Spindle extensions from 500-4000 mm

Advantages:

The TWF trench boxes offer following main advantages:

• Useable in all soil conditions (with proper dewatering system)
• Excellent performance (6-10 sections per day = 18-40 m per day)
• Large head room below buttom strut for large diameter pipes
• Only one excavator and two men for manipulation, installation and extraction
• No crane, power pack or vibrator is required
• Lowest cost per m2 and use compared to other shoring systems
• Long durability and little cost for repairs and maintenance
• Designed according to DIN and latest international standards

Part Details:

The box plates are made either of steel profiles or as sandwich construction with a reinforced top section and a cutting edge at the bottom. Two vertical C-sections at both ends of the plate house the spindle units (consisting of the threaded spindle and two mushroom fittings with springs) which are locked in position by steel pins and secured by safety clips. The mushroom fitting limits the spindle to swivel vertically for +/- 8 degrees allowing the independent movement of the plates during installation and extraction without damage.

The plates are available in different sizes and thickness, starting from 2000 mm length and 600 mm height up to 4000 mm length and 2600 mm height. Various series (S100, S300 and S600) and sizes with different load capacities meet every project requirement starting from cable ducts in small utility trenches up to the installation of large ø1400 mm concrete pipes below the bottom spindle.

The most popular trench box worldwide is the series S600, length 3500 mm and height 2600 mm. Together with top plates (which are supported by only two spindles) of 1400 mm height a trench of ~ 4000 mm depth can be supported safely and efficiently. Depending on the soil condition no other shoring system offers easier installation and better performance in trench depths up to 4 m. The standard spindle units provide an inner trench width of 980 to 1280 mm which can be extended by spindle extensions in steps of 500 mm up to 4000 mm width. For special requirements even larger extensions can be provided.

Assembling:

Every project starts with the assembling of the trench box. The spindles are adjusted to the required trench width and sled with the mushroom fitting into the C-profile of the plate. After locking the spindle into position by the pin and securing the pin by the spring clip the two springs of the mushroom fittings are released which holds the plates always in a 90 degree position when the box stands on the ground. After assembling the trench box the spindle length should be fine-tuned to the requested trench width whereby the bottom of the trench box has to be 20 to 30 mm (depending on the soil condition) wider than the top for easier installation and extraction.

Installation:

Trench boxes are installed by one hydraulic backhoe excavator and two men during excavation using the lower-and-cut method. After making a first cut of 1-1.5 m depth (depending on the soil stability) the trench box is lifted by the excavator into the trench by a 4-leg steel rope or chain. The excavator cuts with the bucket along the box plates and pushes them down with the full bucket alternating on both sides until the necessary depth is reached. If more depth is needed the trench box can be extended by a trench box top which has to be fixed to the base by 4 plate connectors (each having two bolts with safety clips). To avoid any damage of the plate top when pushing with the bucket the use of heavy duty plate protectors is strongly recommended. The work continues in the same way. After a small first cut the next trench box is lifted into the trench and sunken down as described before. If the excavator pushes the new box gently to the already installed one any gap between the boxes can be reduced to a minimum.

Extraction:

After pipe laying the trench boxes can be extracted by the excavator whereby the compaction instructions have to be observed. It is recommended to place the backfill material at first, then to lift the trench box and to compact the backfill in layers against the nature ground avoiding any ground settlements to a minimum.

Safety:

Please observe the following carefully (this is not a complete listening):

• All our trenchboxes areapproved by the German TBG for a certain working load (i.e. 44.70 kN/m2 for the S600, length 3500 mm) which is shown in our leaflets and technical data sheets. Always check the actual soil pressure and make sure that it is within the limits of the approved working load.
• Special care has to be taken with the groundwater. All recommendations for a certain installation depth are made under the precondition that the groundwater is removed before installing any trench shoring equipment. Beside for safety reasons the groundwater in the trench creates great problems for the excavation (bucket full of water, limited visibility, etc) and reduces the possible working performance significantly.
• Take special precautions that nothing can fall into the trench. The safest way is to let the shoring system stand 150 mm above the ground.
• Never use bended spindles as their buckling loads reduced.
• All pins have to be secured by proper safety clips.
• Top boxes have to be connected to the base by plate connectors.
• No worker should stand in the trench while the shoring is sunken down as the excavator operator has limited sight to the working area.
• Workers have to wear hard hats, gloves and safety shoes and observe all standard safety regulations carefully.