Laboratory Testing Equipment and Procedures
Soil Classification Tests
M+EG Technical Services (MTS) provides a variety of basic classification testing services for characterization of soils including sieve analysis, unit weight, water content, Atterberg limits, carbonate content, specific gravity, organic material, Max/Min Density, Compaction, etc. These services are provided to obtain basic engineering parameters and to supplement the advanced testing.
Static Strength of Soil
- Triaxial Tests
- Sample diameters of 36 mm (1.4”), 38 mm (1.5”) and 71 mm (2.8”) are available for testing.
- Capable of testing samples under isotropic/anisotropic stress conditions (full stress-path control), with confining pressure up to about 2 MPa depending on back-pressure conditions
- Samples can be sheared under the following drainage conditions:
- Unconsolidated Undrained (UU)
- Consolidated Undrained (CU) – compression or extension
- Consolidated Drained (CD) – compression and extension
- Direct Simple Shear (DSS) Test
- Sample diameters of 50 mm (2”) and 73 mm (2.9”) are available for testing.
- Capable of testing samples under either constant volume or constant load conditions with maximum vertical stress of 2800 kPa and strains up to about 30%.
- Standard shearing rate of 5%/hour can be adjusted to meet the needs of the project.
- Three different sample sizes are available for testing: 50.8 mm (2”), 63.5 mm (2.5”) and 76.2 mm (3”) diameter samples.
- Automated load increment ratio (LIR) consolidation or constant rate of strain (CRS) consolidation is capable of achieving maximum vertical pressures of up to 6 MPa.
- For CRS consolidation, an electro-mechanical water pump is attached to the load frame to complete the test setup (for 2.5” (63.5mm) diameter specimens only).
- Interchangeable load cells varying from 2.2 kN to 22 kN can be used to allow a tailored operating range based on the individual project requirements.
The MTS Resonant Column test (RCT) equipment is an equivalent Stokoe (1999) device built under contract at the University of Waterloo, Canada by Dr. Giovanni Cascante in 2003. The Resonant Column tests are performed within the framework of the ASTM D4015 standard with minor deviations to account for different devices.
- Sample diameters of 53 mm (2.1”) and 73 mm (2.9”) are available for testing.
- High-pressure testing of isotropically consolidated samples at confining pressures up to 3 MPa;
- Testing performed using either torsional or flexural excitation;
- Testing possible from small to intermediate strain range (from ~10-5 % to ~10-1 %) for measuring both the small strain shear modulus (Gmax) and minimum viscous damping (Dmin%), as well as the variation of both with strain level.
- Back-pressure saturation and volume change control panel are available to fully saturate the samples (if needed) using de-aired water under a sufficient backpressure and maintaining a constant specimen volume.
- The RC test data can be combined with the cyclic DSS results in order to define the complete modulus degradation (G/Gmax) and Damping (D%) variations with shear strain.
Cyclic Direct Simple Shear (CycDSS) Test
The cyclic simple shear apparatus, used for CycDSS tests on undisturbed or reconstituted soil samples, was designed and built by GDS Instruments in UK. The CycDSS tests are performed under constant volume conditions according to the ASTM D6528 norm.
- Sample sizes of 48 mm (1.9”) and 73 mm (2.9”) diameter can be tested in the CycDSS equipment. Samples can be used when extruded directly from thin-walled (3”) diameter Shelby tubes.
- Two Cyclic DSS equipment setups available capable of testing with vertical and lateral pressures up to 2400 kPa (for sample size of 73mm diameter).
- Testing covers the intermediate to large strain range (from 0.005% to about 10%) under cyclic loading.
- Operating frequency in the range from 0.1 Hz to 2.0 Hz.
- Cyclic stress-controlled and strain-controlled testing, as well as static strain-rate controlled DSS testing can be performed.
- Shear wave velocity measurements can be performed on DSS samples by using a special set of platens with embedded bender elements.
- Post-cyclic monotonic DSS test with maximum shear strain of 30%, or post-cyclic consolidation test can also be performed immediately after the CycDSS test.
Bender Element Velocity Measuring
Special end platens with embedded bender elements are used with the electro-mechanical DSS equipment to measure shear (S) wave velocities. The GDS bender element monitoring system (BEMS) is used to measure the shear wave velocity of the DSS samples immediately after initial consolidation to the in situ stress condition prior to shearing. The bender element signal generation and data acquisition is controlled by the GDS BEMS software package.
- Excitation of sinusoidal, square or user-defined wave forms.
- Data acquisition speed up to 2,000,000 samples/second, simultaneous sampling of both source and received signals.
- Resolution of data acquisition (bits) = 16 bit
- Available gain ranges for data acquisition = from x10 to x500
- Titanium inserts for reduced weight (particularly important for the top-cap).
- A plot of the transmitted and received signal with time is presented for each test performed. The shear wave velocity is simply calculated by using the travel time for the first arrival between the top and bottom of the sample. No data filtering / interpretation techniques are applied.