The Gillibrand Arms, Chorley

This contract, won by competitive tender and carried out for Daniel Thwaites Brewery, called upon a number of Anvil Foundation’s specialist techniques. Piled underpinning with needle beams, pin piling to upgrade the existing floor slab and piled ground beams for new construction were all employed to stabilise an existing public house suffering severe differential subsidence.

The brewery employed Shepherd Gilmore Consulting Engineers and Quantity Surveyor Brian Chaddock to supervise and control the works. Along with the stabilisation work, Thwaites took the opportunity to carry out extensive refurbishment works during the shut down.

The public house was constructed in the 1970’s on a thin, shallow raft. Fill deposits were encountered to depths varying from 2.8-7.3m. The material consisted of a random mix of stone,sand, clay ash, brick, topsoil, and peat with occasional pieces of timber and plastic. The natural drift consisting of firm to stiff clay deposits contained a high proportion of shale. Immediately below the clay, the solid deposits of highly weathered shale were encountered, albeit at greatly
varying depths.

Settlement was attributed to: compression of fill due to self-weight and imposed loading; collapse compression of fill due to water inundation; compression of weak deposits below fill;decomposition of organic matter within fill; collapse and migration of materials into possible mine shaft; collapse of possible shallow mine workings.

Probing failed to find evidence of the historic shafts and so a solution involving piles at closely spaced centres was chosen for the main floor slab area. Concentrated reinforcement was installed at the roof support columns using piles and r.c. concrete needle beams. Due to the variation of sub-soil conditions pile