Continuous Evaluation of Shear Wave Velocity from Bender Elements during Monotonic Triaxial Loading

Area of Science:

• Geotechnical Engineering
• Soil Mechanics
• Wave Propagation in Soils

Background:

• Low-strain shear wave velocity (Vs) is a key soil property.
• Experimental data on Vs during large strain deformations is limited.
• The insensitivity of Vs to large strains is not fully understood.

Purpose of the Study:

• To continuously measure low-strain Vs during monotonic shearing of sand specimens.
• To investigate the relationship between Vs and large strain deformations.
• To analyze the underlying micro-mechanical reasons for Vs stability.

Main Methods:

• Continuous measurement of low-strain Vs using bender elements (BE).
• Monotonic shearing of sand specimens in a triaxial device.
• Analysis using a micro-mechanical model based on contact theory.

Main Results:

• Low-strain Vs measurements were unaffected by increasing axial strains.
• The micro-mechanical model accurately predicted Vs values.
• Mean effective stress and inter-particle stiffness were identified as key controlling factors for low-strain stiffness.

Conclusions:

• Confirms that low-strain shear wave velocity is independent of large axial strains in sand.
• Highlights the importance of mean effective stress and inter-particle stiffness in controlling soil stiffness.
• Provides a validated micro-mechanical framework for understanding soil behavior under varying strain conditions.