The Bachy Soletanche Balfour Beatty Ground Engineering joint venture (known as SB3) has had a busy first half of the year delivering the geotechnical works on the HS2 project in the West Midlands.

Working on behalf of Balfour Beatty VINCI JV (BBV), the N1 and N2 contract comprises the piling and ground improvement works for the Long Itchington to North Birmingham section of the new high-speed line, as well as the section into the new Birmingham station.

Since the beginning of 2023, SB3 has completed 21 assets across the scheme, which has included the construction of 2,250 piles, 170 diaphragm wall panels and over 8,250 rigid inclusions. The JV has also successfully trialled a range of low-carbon equipment and developed several cutting-edge solutions to improve operational efficiency.

Key assets delivered in 2023:

Water Orton Cutting

Within 600 working days, SB3 constructed over 27,000 m² of diaphragm wall for the Water Orton Cutting asset. This involved the construction of 131 diaphragm wall panels using a Hydrofraise® and two grabs, which were in operation for more than 2,200 hours in total at this site.

Water Orton Abutments

To support the two new viaducts at Water Orton, SB3 installed 24 large diameter rotary bored piles (2,100mm dia.) to support the abutments. Working simultaneously on each abutment, SB3 exceeded its planned production levels, managing to consistently deliver five piles per week instead of three.

Carol Green Underbridge

SB3 was tasked with delivering 219 piles for a retaining wall and underbridge at Carol Green, using a combination of large diameter and rotary bored techniques. The piles were 1,200mm in diameter and installed to depths of up to 27m.

With two 90-tonne mobile cranes creating a congested working environment, SB3 followed detailed procedures and worked extended hours to safely conduct the lifting operations. Despite these challenges, the JV exceeded its forecasted outputs by 60% and concluded all piling for Carol Green within six months.

HS2 2023 six months progress - Carol Green Underbridge

Carol Green Underbridge

HS2 2023 six months progress - Delta Curdworth Box

Delta Curdworth Box

Additional Works

Along with these key milestones, SB3 has delivered several other assets on its N1/N2 contract this year: the Cromwell Lane Bridge Diversion, Curzon 3 Viaduct, Duddeston Mill Road Underbridge, Lawley Middleway Viaduct and the M42/M6 Link. The team has also completed two assets for the M6 South Viaduct, four assets for the Streethay Cutting Retaining Structure and Phase 2 of the Attleboro Lane Overbridge.

In addition to this, the JV is progressing well with its rigid inclusions work, having recently completed the Mercote Mill Lane Embankment site – this saw the installation of 327 rigid inclusions and two O-Cell piles.

Investing in sustainable plant

During the delivery of the N1/N2 contract, SB3 has continued to support HS2’s environmental commitment. So far in 2023, the JV has trialled a range of the industry’s latest cleanest low-carbon equipment, including electric rigs, fuel efficient plant and tracked concrete pumps.

Earlier this year on the Burton Green Retaining Structure, SB3 installed over 1,000 secant piles using just one rig – despite the original requirement for three conventional rotary bored piling rigs.

At the Curdworth North asset, the JV used the Bauer eBG33 electric rig for four months of the programme. By opting for the eBG33 instead of a traditional diesel-powered rig, SB3 significantly reduced emissions and noise pollution.

Other plant that has been piloted on the project recently includes the new Casagrande B175 piling rig. Compared to older models, this rig offers increased efficiency thanks to a Smart Power Management (SPM) system. Moreover, it benefits from greatly reduced noise emissions as a result of sound-absorbing materials and oil heat exchangers.

In addition to this, SB3 has invested in a modern, compact Hydrofraise®, which is more fuel efficient, consuming less diesel than traditional models. The JV has also procured tracked concrete pumps for use across its sites, which consist of just a single length of hose with no intermediate section. The concrete pump set up requires no cranes or concrete agitator, which is increasing productivity and reducing health and safety risks.

HS2 2023 six months progress - Bromford TBM Water Orton

Water Orton Cutting

Adopting an innovative approach

Alongside these environmental achievements, SB3 has been responsible for several valuable geotechnical innovations. While working on HS2’s Streethay site, SB3 designed and fabricated a ring-shaped frame to support the tremie hopper during the removal of temporary casing from a bearing pile. The frame allows the tremie hopper to be easily detached and reattached to the lifting equipment. The innovation provides a safer and more efficient method than the traditional technique of suspending the hopper from a Kelly bar. Due to its success, SB3 has adopted the solution for all piles installed on the M42/M6 site.

During the delivery of rigid inclusions, SB3 designed a plunger tool to help install CFA reinforcement cages and central steel bars to the correct level. This innovation has been successfully deployed across all rigid inclusion sites on the N1/N2 contract. The plunger works by controlling the position of the reinforcement in the pile. Therefore, the tool provides increased accuracy and efficiency as it removes the need for operatives to manually control the position of the reinforcement.

Another creative solution implemented by SB3 was the use of the cutting-edge O-Cell (Osterberg Cell) technique to carry out pile tests on the Water Orton site. An O-Cell is a hydraulically driven, calibrated, sacrificial jacking device installed within a pile to enable full scale static load testing. The team chose to use O-Cells due to insufficient space for anchor piles. Unlike other static load testing methods, the O-Cell requires a much smaller working area and is capable of testing high-capacity, large diameter bored piles.

Related Insights…