Safe and secure trenching

A new era of shoring safety and efficiency in trench construction has hit our shores with the arrival of the Krings DGVP double slide rail.  

Trench Shoring New Zealand (TSNZ), a specialist in the hire and sale of purpose designed and built shoring equipment, now has a license from Krings International France (KIF) to distribute and hire its equipment throughout New Zealand, Australia and the Pacific Islands.

Since the company was set up in June 2007, Trench Shoring has focused solely on the Krings KS100 trench box. Over its first year of operation TSNZ has successfully established a well supported hire business, and the KS100 hire stock has been in constant demand throughout the country. The KS100 effectively shores trenches to a depth of 3.5 metres and, in some cases up to five metres.

The company recognised that deeper trench excavations  required a heavy duty shoring system with the flexibility to be deployed at greater depths and widths, and with the capability for very high clearances that enable large diameter pipe to be laid.

Sliderail systems were developed to overcome problems with deep trenching. In particular, there are very high forces required to extract shoring boxes from trench depths of more than four metres, and the most commonly used other option of sheet-piling is laboriously slow, noisy and expensive.

Krings International France have a wide range of shoring equipment available from small trench boxes to the largest DGVP Double Slide Rail system.

Abbotts Way project

TSNZ did not have to wait long or look too far for an opportunity to come up for a slide rail system for use in New Zealand. In late 2007 the company got an opportunity to promote the DGVP Double Slide Rail system to engineers who were designing and planning the Auckland City Council Abbotts Way roadway. This projects is for a new and large diameter storm water pipeline to that will be laid along the very busy Abbotts Way roadway that cuts through Remuera in central Auckland.

When the project was tendered in early 2008, one company enthusiastically embraced the slide rail concept as the best shoring alternative available in the country. Kerry Drainage called on the combined knowledge of Krings International and TSNZ to develop a shoring proposal for this project, and subsequently was awarded the contract.

TSNZ went to work to import the almost 50 tonnes of shoring equipment from a manufacturing facility in Germany. Since late July, the DGVP Double Slide Rail system has been in use on the Abbotts Way project, providing very safe and efficient shoring for Kerry Drainage to lay the heavy 1950mm diameter Class Y concrete storm water pipes. The large diameter storm water line is 470 metres long and is being installed immediately adjacent to the kerb at depths of approximately five metres to the pipe invert.

Abbotts Way is a relatively narrow road but is a highly used route across this part of Auckland, posing traffic management challenges for the contractor. Using the Krings DGVP Double Slide Rail is enabling Kerry Drainage to quickly and safely excavate without compromising the remainder of the road. Heavy vehicles can pass close to the excavation without risk of subsidence.

The configuration of Double Slide Rail in use is up to four sections of rails and panels, allowing a total excavated length of 17.5 metres. Inside width is three metres to allow enough space for the 1950mm concrete pipe to be laid. A key feature of slide rail systems is the ability of the “boogie car”, or slide frame, which can be raised and lowered to accommodate operations in the trench and for large diameter pipe to be manoeuvred into position without any interference from shoring cross bracing as with the fixed spindle set ups of smaller systems.

Additionally, the double slide rail is so named for the combination of inside and outside shoring panels. Outside panels are positioned and installed first and, as the excavation proceeds to greater depths the inside panels are installed without a high degree of friction or lateral force. This makes the installation easy and the extraction straight forward.

Base panels on the TSNZ system here in New Zealand are four metres long and extension panels are 1.3 metres high, giving a combined continuous shoring depth capability of up to six metres. Slide rails are six metres long to accommodate this.

Innovative sheet piles

Another innovation in New Zealand shoring is the Krings KKP sheet pile frame and sheet piles that TSNZ has also provided to Kerry drainage for the Abbotts Way project.

The sheet pile frames are four metre long and can be installed in the slide rail system or with the KS100 system. Each sheet pile frame can accommodate seven of the 6.5 metre long by 8mm thick sheet piles supplied by TSNZ. Their purpose is to provide shoring around services that cross the trench.

The frames are installed near the top of the trench and sheet piles are guided into position either side of the cross trench service and, if necessary, to the top of the service. Installation is by the same dig and push method used on all of the Krings/TSNZ shoring solutions. This eliminates the need for a lot of force, vibration or other disruption associated with traditional sheet piling.

Corner side rails

Part of the slide rail system imported by TSNZ are corner slide rails. These can be used with the same shoring panels to provide four sided pits, ranging from four metres square to eight metres square and five metres to six metres in depth, for a variety of general construction such as underground tanks, treatment tanks for sewer or stormwater and access pits for pipe thrusting or boring.

The DGVP Double Slide Rail system has been supplied to Kerry Drainage by TSNZ in conjunction with TSNZ’s distributor, Humes Pipeline Systems.