Geotechnical slope stability assessmentJune 25, 2018, 8:14 am
We were commissioned by our client to investigate evidence of slope instability and settlement of an industrial unit adjacent to a retaining wall in the Walker area of Newcastle.
Our remit was to establish the cause and mechanism of failure and to recommend suitable options for remediation so that the client could determine the risk to adjacent structures / property, and to return the industrial unit back to use.
Initially we carried out a visual inspection to assess the site and to check access constraints for a ground investigation. The building was showing obvious signs of subsidence including cracks in the external brickwork and internal plaster, and gaps between window and door frames. The slope also showed signs of movement relative to fixed objects and a tension crack was visible along the crest.
We decided to drill a Cable Percussion borehole at the crest of the slope and toe of the retaining wall; Windowless Sampler boreholes along the crest and toe of the failing section; hand-held Windowless Sampler boreholes along the slope itself; and finally, hand-dug pits to expose the existing foundations.
Exploratory holes revealed that the buildings and retaining wall were founded on a relatively complex series of superficial deposits ranging from clay to gravel. Samples from the boreholes were tested to derive material parameters of the soils so that the slope failure could be analysed using specialist computer software.
Analysis indicated a tendency for shallow slip surfaces within the clay embankment slope, which, combined with consolidation and creep of the slope was considered to be the cause of failure leading to the settlement of adjacent building.
We then carried out an options appraisal of viable remediation techniques for the site and were able to recommend a two-phase approach. Firstly, stabilising the embankment slope using an embedded, interlocking, steel sheet pile cantilever wall; and secondly remediating the building settlement by underpinning with jacking or geo-polymer injection to lift the existing foundations.
If you require geotechnical investigation for slope stability we are highly experienced in this field – please do not hesitate to contact a member of the team on 0191 230 4521.