BSP hammer aids Breheny Contractors to reinstate sea wall collapse
Sea walls are the frontline defense against strong tides and winter storms which relentlessly pound coastal regions, especially along Britain’s eastern coastline. Despite being constructed of reinforced concrete the sturdiest of seawalls can occasionally be breached in extreme weather conditions. If not repaired immediately further and more serious damage can result.
This was the case last January when Needham Market-based J Breheny Contractors was working on sea wall repairs at Kings Cliff Promenade, Clacton on Sea, Essex, when freak storms caused approximately 40m of the sea wall at nearby Holland on Sea to collapse.
Detailed investigations found the cause to be erosion of the sand beneath the walls, resulting in a section of the promenade wall breaking away and slipping down towards the sea. Emergency repairs were required as any delay could lead to further sections of the wall collapsing totally into the sea. With no effective barrier to stop it, the sea was also causing damage to the promenade itself.
Tendring District Council (TDC) approached Breheny to advise and put forward a design to reinstate the sea wall. In partnership with Haydon Evans Design Consultants and TDC a design and price were agreed. Work to repair the wall began at the end of February.
The existing sea wall was stabilised by pinning it with 6m Larson piles to prevent further erosion and slippage. Remedial work then continued to complete a total repair of the sea wall and promenade.
Approximately 150 x 9m PU 18 piles have been used, and driven to a depth of approximately eight metres into sand and claystone. The overall length of the piling work along the front was approximately 40 metres. Because the only access to the damaged sea wall was via the crumbling promenade all materials and equipment had to be carefully transported along the sea front using a steep vehicular access ramp approximately half a mile south of the failure. This operation had to be supervised by a full time banksman as this length of sea front is lined with beach huts which are fully open to residents and the general public.
The work was carried out in shifts under tidal conditions by a team of 10 of Breheny’s directly employed specialist staff. Equipment used included Breheny’s own NCK Pennine C40 crawler crane, with a 35 tonne capacity, and two mini excavators while the piles were driven by a BSP SL20da piling hammer, powered by a BSP Hydropack, and a vibrating unit all hired from Watson and Hillhouse, the independent Ipswich-based piling equipment specialist.
Following the installation of the sheet piles, an insitu concrete capping beam was cast on top of the new piles at beach level together with an insitu concrete landing beam cast on top of the old seawall. In addition, placing of pre-cast concrete step/wall units and the necessary insitu in-fill along with repairs to the existing foul and surface water drainage as well as the restoration of the promenade, are due to be completed in July.
Throughout the project the works have been continuously planned and carried out in consultation with the Council. Regular meetings of the project delivery team has ensured the works have been carried out economically, swiftly and with minimum disruption
Established in 1963 Breheny has gradually expanded to become one of the largest privately-owned civil engineering companies in the UK. Today the company’s activities encompass everything from design and build to highway construction and maintenance, bridge building, landfill site operations and coastal defence projects.
The popular compact SL20da piling hammer and its larger stablemate the SL30da with drop weights of 1.5 tonnes and 2.5 tonnes respectively, have been designed and manufactured by BSP International Foundations for driving single sheet piles and small bearing piles of concrete, steel or timber with an
ultimate load bearing of up to 1800kN depending on site conditions. A low hook weight and relatively small hydraulic power required to operate make these hammer an economical option for the construction of pile walls, coffer dams and temporary earthworks.
Using BSP’s innovative double acting (da) cylinder, the ram is accelerated on its downward path to achieve higher impact energy. This energy is developed from a short stroke leading to a higher blow rate and greater pile productivity compared to an equivalent single-acting hammer.
In the past piling equipment has been virtually dominated by specialist contractors and piling divisions of large civil engineering companies. However, growth in the rental sector led BSP to develop the SL and the larger CX range of piling hammers.
Watson & Hillhouse has been a leading UK independent piling equipment company which has specialised in this sector of the market since 1972. The company says its investment of more than £5 million represents the country’s most comprehensive range of piling equipment and a policy of continual replacement makes plant available for second-user sales alongside its hire and new equipment sales business.
-- ENDS --