Central Alliance's CSW testing system uses a ‘vibrator' with an operating range of 5-100Hz to produce surface or ‘Rayleigh' waves, which propagate across the ground surface. These waves are detected by a system of geophones and analysed by software to provide a stiffness versus depth profile. If required, office-based post-processing can provide shear wave velocity profiles and subsequently mechanical properties of the ground such as shear modulus and elastic (Young's) modulus.

CSW testing brings a number of benefits to all ground investigation (GI) contractors including rail and those in crane pad design as well as consultants offering a non-intrusive, portable and economic depth-profiling solution, compared to traditional ground profiling methods.

Specifically, Central Alliance's CSW testing provision provides depth profiling up to 30m. It also delivers rapid results without invasive testing and enables the measurement of ground stiffness, comparable to results of CBR and SPT testing through the use of published research. Automated test software allows customisable testing for areas of interest and the equipment is lightweight and portable.

Speaking about the launch of the new CSW service Craig White, joint managing director of Central Alliance, said: "The addition of CSW testing to the company's portfolio of testing and surveying techniques greatly widens the options available to our clients in both the rail sector where this technique will find particular application, and the wider constriction industry. With CSW being portable, economic and non-invasive, as well as providing comparable results to CBR and SPT testing, its benefits will make a real difference to depth profiling applications."