M A S W

Multichannel Analysis Surface Waves

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The MASW software

The MASW software implements the MASW method to determine the speed profile of Vs shear waves and, therefore, also the soil type according to the National and European technical regulation.MASW test on site

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SEISMIC GEOTECHNICAL CHARACTERIZATION OF SOILS

The new Italian O.P.C.M. n. 3274/2003 seismic regulations and ensuing amendments and integrations, and the European technical regulations, Eurocodes EC 7 and EC 8, give the right level of importance to the seismic geotechnical characterization of soils on which works of any nature will be executed (residential and industrial buildings, sides supporting and stabilizing works, road rises, infrastructural works, embankments, dams and hydraulic works, tunnels, bridges and structural works of large dimensions, etc..). Soil characterization, in particular from a seismic point of view and generally from a dynamic point of view, requires, as an indispensable element, the knowledge of the speed profile of Vs shear waves of soil strata on the site, down to a depth of at least 30 meters from the country plain, as required by the above-mentioned regulations. The profile of Vs shear waves in the first 30 meters of depth is needed to:

  • evaluate the design seismic action at the foundation level of any structure
  • evaluate the liquefaction risk of the soil on site
  • evaluate the instability risk of slopes and/or of support structures
  • evaluate the sinking of road rises, supporting works, and building foundations
  • evaluate the transmission of vibrations generated by trains, vibrating machines, surface or underground explosions, vehicle traffic

Based on the speed profile of Vs shear waves in the first 30 meters of depth, it is possible to determine a speed equal to Vs30 and representing the site under examination, according to which we can classify a site as soil of type A, B, C, D, E, S1, S2 according to the new Italian seismic regulations or the Eurocode 8 European regulations.

Classification of soil types according to the new O.P.C.M. n. 3274/2003 seismic regulations
Soil Geotechnical description Vs30(m/s)
A Lithoid formations or very rigid homogenous soils characterized by values of Vs30>800m/s, inclusive of any superficial alteration strata with a maximum thickness of 5m >800
B Deposits of very thickened gravels or sands or very consistent clays, with a thickness of several tens of meters, characterized by a gradual improvement of mechanical properties with depth and by Vs30 values between 360m/s and 800m/s 360800
C Deposits of medium thickened gravels or sands or medium consistent clays, with a thickness varying from several tens to hundreds of meters, characterized by Vs30 values between 180m/s and 360m/s 180360
D Deposits of granular matter, from loose to lightly thickened, or cohesive matter, of light to medium consistence, characterized by values of Vs30 < 180m/s <180
E Soil profiles made of alluvial surface strata, with Vs values similar to the C or D type and with a thickness between 5m and 20m, lying on a substratum of more rigid material with Vs > 800m/s  
S1 Deposits made of, or including, one stratum at least 10 m thick of clays/silts of low consistency, with a high level of plasticity (IP>40) and water content, characterized by values of Vs30 < 100m/s <100
S2 Deposits of soils that are subject to liquefaction, of sensitive clays or of any other soil category that cannot be classified in the previous types