Main Client Environment Agency Commitment Innovation Sustainability Case Study Case Study The Problem The Solution The Verdict www.mgf.ltd.uk Volker Stevin at Hexham Head Office: 01942 402700 North East: 0191 378 2100 Yorkshire: 01977 521930 North West: 01942 896282 Midlands: 01889 574777 South West: 01179 820706 London North: 01296 663250 London City: 01322 344520 Date 2005 Contractor/Customer Volker Stevin In August 2005, Volker Stevin were working for the Environment Agency on a Flood Alleviation Scheme at Hexham, Northumberland. As part of the installation of a new culvert system, a thrust pit was required to pass underneath an existing heavy goods railway line. A 3.5m deep cofferdam, 23.0m by 7.5m was required approxi- mately 3.0m away from the railway line. A clear span of 15.5m was required to allow easy installation of the 12.5m long, 900mm Ø pipe sections, but movement was critical, with the maximum allowable deflection of 10mm due to the close proximity of the rail. The ground conditions consisted of granular fill, loose sand and dense gravel overlying a band of silt. Groundwater was encountered at 4.96m below commencing level. Additional loading came from surcharges for plant and the railway, and haystacks were placed along the side of the excavation to reduce noise pollution to the nearby neighbourhood. A propped cantilever style cofferdam was designed by MGF utilising 6.5m long 4A Sheet Piles toed 3.0m into the dense gravel with a frame at 0.5m below ground level. In order to withstand the high load whilst maintaining a large clear span with minimal deflection, MGF’s new Super Tank Brace with 120Te Hydraulic Powerpacks was used. A high capacity 120Te Mechanical Strut was positioned 7.5m from one end in order to keep within allowable deflection limits, while sustaining enough working room to lower in the 12.5m long pipe sections with ease. The excavation was quick and easy to install as the sequence was un-complicated with no need for re-location of struts. The high bending capacity of Super Tank Brace meant that the clear opening required was easily achieved and only a single frame was required to withstand the loadings. Movement of the nearby railway was monitored closely throughout the excavation and defections were kept within allowable limits. The Method The sheet piles were pre-driven to full depth prior to any excavation taking place. The first 1.0m of material was excavated and the frame was laid out level and plumb. The hydraulic components were pumped out to gain a tight fit within the sheets piles. Hanging chains were attached and hung from the top of the piles and the cross strut was installed. Excavation continued to formation level at 3.5m below commencing level. A concrete base was cast and the pipes were installed. Once the permanent works were complete, the excavation was backfilled to the underside of the frame, and the frame was then removed. The introduction of MGF’s Super Tank Brace range has had a dramatic impact on our approach to large cofferdams and deep excavations. Huge clear spans are now achievable under heavy loading without the need for twinning frames up and the versatility of the system and its ancillary products mean that this off the shelf product can be used to suit more bespoke schemes. MGF Super Tank Brace

MGF Excavation Safety Solutions - Volker Stevin at Hexham · 2019. 1. 30. · minimal deflection, MGF’s new Super Tank Brace with 120Te Hydraulic Powerpacks was used. A high capacity

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Page 1: MGF Excavation Safety Solutions - Volker Stevin at Hexham · 2019. 1. 30. · minimal deflection, MGF’s new Super Tank Brace with 120Te Hydraulic Powerpacks was used. A high capacity

Main ClientEnvironment Agency

Commitment Innovation Sustainability

Case StudyCase Study

The Problem

The Solution

The Verdict

www.mgf.ltd.uk

Volker Stevin at Hexham

Head Office: 01942 402700 North East: 0191 378 2100 Yorkshire: 01977 521930 North West: 01942 896282 Midlands: 01889 574777 South West: 01179 820706 London North: 01296 663250 London City: 01322 344520

Date2005

Contractor/CustomerVolker Stevin

In August 2005, Volker Stevin were working for the Environment Agency on a Flood Alleviation Scheme at Hexham, Northumberland. As part of the installation of a new culvert system, a thrust pit was required to pass underneath an existing heavy goods railway line. A 3.5m deep cofferdam, 23.0m by 7.5m was required approxi-mately 3.0m away from the railway line. A clear span of 15.5m was required to allow easy installation of the 12.5m long, 900mm Ø pipe sections, but movement was critical, with the maximum allowable deflection of 10mm due to the close proximity of the rail.

The ground conditions consisted of granular fill, loose sand and dense gravel overlying a band of silt. Groundwater was encountered at 4.96m below commencing level. Additional loading came from surcharges for plant and the railway, and haystacks were placed along the side of the excavation to reduce noise pollution to the nearby neighbourhood.

A propped cantilever style cofferdam was designed by MGF utilising 6.5m long 4A Sheet Piles toed 3.0m into the dense gravel with a frame at 0.5m below ground level. In order to withstand the high load whilst maintaining a large clear span with minimal deflection, MGF’s new Super Tank Brace with 120Te Hydraulic Powerpacks was used. A high capacity 120Te Mechanical Strut was positioned 7.5m from one end in order to keep within allowable deflection limits, while sustaining enough working room to lower in the 12.5m long pipe sections with ease.

The excavation was quick and easy to install as the sequence was un-complicated with no need for re-location of struts.

The high bending capacity of Super Tank Brace meant that the clear opening required was easily achieved and only a single frame was required to withstand the loadings.

Movement of the nearby railway was monitored closely throughout the excavation and defections were kept within allowable limits.

The MethodThe sheet piles were pre-driven to full depth prior to any excavation taking place.

The first 1.0m of material was excavated and the frame was laid out level and plumb.

The hydraulic components were pumped out to gain a tight fit within the sheets piles.

Hanging chains were attached and hung from the top of the piles and the cross strut was installed.

Excavation continued to formation level at 3.5m below commencing level.

A concrete base was cast and the pipes were installed.Once the permanent works were complete, the excavation was backfilled to the underside of the frame, and the frame was then removed.

The introduction of MGF’s Super Tank Brace range has had a dramatic impact on our approach to large cofferdams and deep excavations. Huge clear spans are now achievable under heavy loading without the need for twinning frames up and the versatility of the system and its ancillary products mean that this off the shelf product can be used to suit more bespoke schemes.

MGF Super Tank Brace