Geotechnical Drilling

Geotechnical drilling involves assessing the physical properties and structural integrity of subsurface materials. It is crucial in the planning and design of infrastructure and facility projects, as it helps engineers understand soil behavior, foundation requirements, and the potential for subsurface hazards such as soft or hard soils, undocumented fills, and karst.

Instrumentation Installations

Instrumentation installations in drilling refer to the placement of monitoring devices, sensors, and data collection equipment within boreholes. These instruments help track changes in subsurface conditions, such as groundwater levels, soil moisture, movements, and pressure, providing valuable data for research and engineering projects.

Power Auger Borings

Power auger borings are commonly used for shallow drilling projects, such as soil sampling for construction sites. These machines use a rotating helical screw to excavate soil and collect samples efficiently. Samples collected from power auger borings are often used to assess the presence of fill materials, and to evaluate the potential for re-use of onsite soils during construction.

Rock Coring

Rock coring is employed when drilling through hard rock formations. It involves the use of diamond-tipped core bits to extract cylindrical rock samples. This technique is invaluable in geology, mining exploration, and structural engineering to determine the properties of rock strata.

Standard Penetration Tests

The standard penetration test (SPT) is a geotechnical test that assesses the relative density of soil at various depths. It involves driving a standard sampler into the ground using a defined energy and counting the number of blows required to achieve a specific penetration depth (per ASTM D1586 requirements). SPT results are used to evaluate soil strength in clays, relative density in cohesionless soils, and estimate soil bearing capacity. Disturbed soil samples are also collected during performance of SPT, allowing for classification of soils encountered with depth.

Thin Wall Tube Sampling

Thin wall tube sampling is a specialized technique used to collect undisturbed soil samples for laboratory analysis that complies with ASTM D1587 requirements. It involves carefully extracting undisturbed soil specimens without altering their physical characteristics, ensuring accurate assessments of soil properties. These specimens are then able to be subjected to various laboratory strength tests such as Unconfined Compression (UC) and Unconsolidated Undrained (UU) Triaxial Compression tests, and laboratory compressibility tests such as Consolidation tests, to evaluate in situ soil properties.

Texas Cone Penetration Test (CPT)

The Texas Cone Penetration Test (Texas CPT) is a geotechnical testing method that measures the resistance of soil layers to penetration. It provides data on soil properties, such as shear strength and stratigraphy, particularly in plastic soils.

Vane Shear Test (VST)

A Vane shear test (VST) is performed to estimate the in situ undrained shear strength of cohesive soils. The test is performed by pushing a four-blade vane into the subgrade soil at distinct depths within a borehole and slowly rotating the vane under a measured torque at regular intervals until the soil shears. The peak torque at shear is then used to determine the undrained shear strength of the soil in accordance with ASTM D2573.

Cone Penetrometer Testing (CPT)

Cone Penetrometer Testing (CPT) is a supplemental geotechnical investigation method that uses an instrumented cone, which is hydraulically advanced into the ground at a controlled rate, to measure geotechnical properties of the soils and to delineate soil stratigraphy. The CPT cone can contain numerous instruments capable of measuring such properties as tip resistance (Qt), sleeve resistance (Fs), pore pressure (u), and shear wave velocities (Vs) to develop geotechnical engineering properties.  Additionally, the soil behavior type (SBT) will be inferred from established relationships between tip resistance, sleeve friction, and pore pressure which can assist with soil classification.  Because the CPT is advanced continuously to the termination depth of the test, strata interfaces and changes in soil properties can be more distinctly defined than with intermittent sampling normally conducted through drilling alone.

Seismic Piezocone (SCPT)

The CPT equipment can be outfitted to perform seismic CPTs (SCPTs), which measure shear wave velocities using an electronic piezocone containing an enclosed geophone in accordance with ASTM D 7400-08. The seismic testing can provide measured values of the soil shear wave velocity (Vs), which can be correlated to shear modulus (Gs), Poisson’s ratio (ν), and elastic modulus (E). These parameters are then used in engineering foundation stiffness design and verification of Seismic Site Classification. The calculation of the soil elastic modulus is also useful in evaluation of soil settlement.

Dissipation Testing

As part of the CPT capabilities, pore water dissipation testing can also be conducted to provide valuable data for performing settlement calculations. From the measured pore water dissipation rates, time-rate of settlement parameters can be refined in consolidation settlement analyses (ex. in the areas of proposed tanks, surcharge loadings, etc.).