Geotechnical field tests

Field tests include alongside direct ground explorations (borings and trial pits), indirect exploration methods using sounding apparatus, as well as geophysical and seismic measurements. The indirect methods make it possible to explore the condition of the ground while causing only minimum disturbance, if any, to the ground structure.

Direct ground exploration

Direct ground exploration is usually contracted out to suitable companies while the Federal Waterways and Shipping Offices are responsible for supervision. Well drilling experts from BAW carry out random checks. In special cases, driven core sounding and hollow stem auger drilling is carried out by BAW staff.

Indirect exploration methods

For indirect exploration, field tests are carried out partly by BAW and partly by external companies to obtain results that allow conclusions to be drawn about the structure of the ground and its properties. BAW uses the following geotechnical equipment and methods:

• Dynamic probing light (DHL)
• Dynamic probing heavy (DPH)
• (modified) standard penetration test (BDP)
• Cone penetration test (CPT)
• Flat dilatometer
• Air pressure probing
• Field vane test
• In-situ determination of density
• Freeze core sampling
• Plate Load test
• Dynamic plate load test

Geophysical measurements

Geophysical measurements are used to establish soil models or investigate geological and anthropogenic disturbance zones and bodies. The appropriate deployment of geophysical methods depends on the presence of contrasts in the physical parameters of the ground (density, specific electrical resistance, dielectric constant, velocity of seismic waves, etc.)

The following methods are used:

• Geoelectric methods
• Seismic methods
• Georadar
• Borehole geophysical methods

Geodynamic field tests

BAW has developed low-cost field tests and analysis procedures for replacing elaborate and expensive methods such as trial pile driving and trial detonations. These consist of:

• Simulating pile hammer
• Simulating vibratory driving
• Underwater trial detonations for simulation the vibrations caused by detonation for the demolition of structures under water

Geohydraulic field tests

The use of different field test methods allows the geohydraulic properties of aquifers, e.g. their hydraulic conductivity or specific storage coefficients, to be calculated and groundwater flow velocities to be recorded in situ. Depending on the boundary conditions of the specific site and the issues being investigated, the BAW will choose suitable techniques from a wide range of test methods, accompany the execution of the tests and evaluate the test results. Tests include:

• Pump tests for the calculation of the large-scale conductivity and storage properties of an aquifer,
• Hydraulic borehole tests (constant rate injection, drill-stem, slug-and-bail and water pressure tests) to calculate local conductivity and storage values in the vicinity of the borehole,
• (Thermal mass) flow meter measurements to find out preferential inflow zones in boreholes or near well screens,
• Thermal measurements to locate leaks in impervious canal bed linings,
• Tracer tests (introducing natural and artificial tracers into the aquifer) to plot groundwater flows,
• Groundwater sampling to calculate the concentrations of substances in the water.

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Overview