MASW - Applcations

Shear-wave velocity (Vs) information of subsurface materials is directly related to the stiffness property of the materials, which is the key property dealt in all geotechnical engineering projects. In this sense, the MASW method can be applied to any geotechnical engineering project that requires subsurface mapping of the stiffness in 1-D, 2-D, and 3-D formats.

The most common type of application has been the soil-bedrock mapping that delineates topographic boundary between soil and bedrock by an interface of significant velocity (Vs) increase (e.g., from 300 m/sec to 1000 m/sec). It also shows vertical and horizontal variation of soil stiffness by displaying velocity (Vs) variations within the soil range (e.g., 100 m/sec - 300 m/sec). This boundary often shows a gradual change in velocity over a certain depth range rather than a sharply-defined interface, indicating the possible weathered zone on top of the bedrock. More recently, applications to detect subsurface anomalies are merging. These anomalies may include localized low-velocity zones created by various reasons such as existing utility tunnels, void development due to collapse, severely weathered bedrock, loss of cohesiveness in filled materials, etc. In this case, the detection is often facilitated by non-velocity mapping approaches such as back-scattering analysis and common-offset section generation. Another type of application is the performance evaluation that is executed before and after a specific operation is applied. This includes the compaction evaluation for surface and shallow subsurface materials during road and building construction.

Site classification according to EC8 and DIN4149

In order to quantify the design load for buildings due to an earthquake the Eurocode 8 (EC8) and the DIN4149 require the classification of the ground. The dominating or average shear wave velocity in depths down to 30 m is most often used for this classification. Beyond that the standards request certain design features as flexible foundation beams based on the class of the subsoil which are affecting the costs of a building. A seismic survey can often reduce the costs because otherwise necessary safe assumptions concerning the classification are avoided. Surface wave measurements such as MASW are especially suited to determine shear wave velocity profiles at these shallow depths.

Example:

MASW measurements were made in the planning phase of a warehouse to classify the building site and to determine the necessity of flexible foundation beams. The result in the figure to the left shows the calculated shear wave velocity profile, where the velocity depth profile is assigned to the middle of the geophone array. The average shear wave velocities determined at depths of 3 to 20 m is the so called dominating shear wave velocity. This velocity is used to classify the foundation site according to DIN 4149. For this example the site was assigned as subsoil class B with dominating shear wave velocities between 350 and 800 m/s. For class B foundation sites, situated in low risk earthquake zones, the use of flexible foundation beams is not required.

The measurement of the Earth’s Magnetic field is an important Geophysical discipline that has wide applications in various fields

• Mineral exploration
• Mining ore body delineation
• Buried pipelines and other utilities
• Archeological studies
• Un-eXploded Ordnance (UXO)
• Marine ship wrecks
• Marine anchors, chains and other items
• Marine cables, pipelines, etc.

G-859. A self contained, “Back Pack” configuration that can collect high quality magnetic data at “walking speed”. The integrated GPS enables data collection without the necessity to set-out grid lines prior to the survey

MAP Mode

New mode allows 2D files collected with GPS data to be viewed in 3D. See the actual spatial view of collected data.

Enhanced and Simplified 3D Viewing

QuickDraw module provides improved 3D viewing options in a single dialog box. Animation from any slice with any other slice. Z width control always available. Stretch, shrink and zoom as desired. Fit a large file into a single view or zoom in on any section.