ACSW
advanced Continuous Surface
Wave Testing
Advanced Continuous Surface Wave (ACSW) testing uses surface geophones to measure the speed at which surface Rayleigh waves generated by a vibratory 'shaker' travel through the ground over a range of frequencies. Using advanced software ACSW provides a representative shear wave velocity (Vs) profile, which can be used for site assessment or to provide highly accurate ground stiffness values
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Specialist ACSW testing & Analysis
The velocity of surface waves generated is directly related to ground stiffness. The speed of shorter wavelengths is influenced by the stiffness of shallower layers and the longer wavelengths by the stiffness of deeper layers, so measuring the velocity over a range of frequencies means a stiffness depth profile can be produced. GSS Advanced Continuous Surface Wave (ACSW) system is controlled and evaluated by GSS's bespoke C-DAS data acquisition and analysis software which provides easy-to-understand outputs. Importantly, as part of the analysis process a shear wave velocity (Vs) profile is generated which can be used for seismic design or site assessment.
Key benefits of ACSW Testing
Stiffness & Vs profile to typical 20 to 30ft depth or more
Measurements at known small-strain stiffness – so stiffness can be adjusted for design strains
A bulk stiffness/Vs value over a 10ft length of soil
About 30mins per test, including setup and packing up
Costs equivalent to Plate Load Test
Low risk
Non-intrusive, so no need for boreholes or lab time
A bright new wave in geotechnics.
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Realtime stiffness profiles in less then 10 minutes
Continuous Surface Wave (CSW) testing measures ground stiffness from surface down to depths of 6 to 10m or more.
Testing is undertaken from a self-contained 4WD test vehicle wherever access is possible to within 10m of test locations to ensure the fastest production rates. However as test equipment is portable testing can be undertaken remotely from the test vehicle where 4WD access is not possible.
Our advanced C-DAS data acquisition software completes each test in around 5 minutes, with preliminary results immediately displayed. On favourable sites with 4WD access 12 or more tests per shift are usually possible, allowing rapid site characterisation.
Continuous Surface Wave Testing Our Company
High quality ground stiffness data
Continuous Surface Wave (CSW) testing provides in-situ stiffness profiles without boreholes or sampling and the associated potential for sample disturbance. Stiffness is averaged over the test length, normally 3m, so gives a representative bulk sample, avoiding the problems of very local variation in ground conditions.
Unlike many other stiffness measurements CSW provides a small-strain stiffness (G0), a 'baseline' measurement at a known strain which can then be readily adjusted ('strain softened') to actual design strains. GSS provides stiffness data in an easy-to-use spreadsheet, allowing the user to input design strains. Data is also ideal for 3D ground modelling or BIM applications.
There is excellent published data to prove the equivalence of CSW data with other more expensive techniques such as downhole seismic testing or large scale load tests.
Cost-effective ground profiling
Continuous Surface Wave (CSW) testing does not require boreholes or the use of additional plant. Combined with the speed of testing (typically 12 per shift) this makes it an extremely cost-effective way of providing high quality stiffness data. CSW also provides non-intrusive shear wave velocity (Vs) profiles for seismic design, liquefaction assessment and preliminary ground charachterisation using published correlations with soil parameters. In rock Vs profiles can be used to assess rock quality and excavatability.
The non-intrusive nature of CSW also means that it is sustainable and low risk, hence it can be used in many situations where the presence of sensitive services or structures would make other types of testing impossible. The portable nature of equipment and speed of testing means it is ideal for use in difficult to access, time-restricted situations such as the rail environment.
The cost of each CSW test is only around that of a conventional plate load test, but provides a stiffness profile to depths of 6 to 10m or more of equivalent quality to the most expensive stiffness measurement techniques.