Feasibility of the use of nonlinear solitary waves for the nondestructive measurement of Young's modulus of rocks and compacted materials

This article describes the development of a new device to measure the Young's modulus of geomaterials. This device bases its operation on the propagation of nonlinear solitary waves along a chain full of spheres. The chain is placed vertically on the sample's surface, and then an incident wave is generated at its top. The pulse travels through the chain of spheres from top to bottom, generating a reflected wave as a result of the interaction between the last element and the material tested. The time-lapse between the incident and reflected waves, measured using a piezoelectric load cell inserted in the middle of the chain of spheres, allows the estimation of the Young's modulus of the sample through a numerical model. The usefulness of the device is demonstrated in control samples of known elastic properties, rocks, and compacted soils. Besides, this paper proposes a modification of the device, which consists of placing a metal cylinder instead of the last sphere of the chain; This modification improves the results obtained when analyzing soft soils. The results show that Young's moduli calculated by the developed device are equivalent to the modulus measured by alternative tests. This device could become a useful nondestructive test for measuring Young's modulus of subgrade materials.