High-pressure compressibility and shear strength data for soils

Soil behaviour is often an important consideration in the design of protective systems for blast and impact threats, as the properties of a soil can greatly affect the impulse generated from buried explosive devices, or the ability of a soil-filled structure to resist ballistic threats. Numerical modelling of these events often relies on extrapolation from low-pressure experiments. To develop soil models that remain accurate at very high pressures there is a need for data on soil behaviour under these extreme conditions. This paper demonstrates the use of a high-pressure multi-axial test apparatus to provide compressibility and shear strength data for four dry sandy soils. One-dimensional compression experiments were performed to axial stresses of 800 MPa, where the effects of particle-size distribution were observed with respect to compressibility and bulk unloading modulus. Each soil followed a bilinear normal compression line (NCL): more uniform soils initially had higher compression indices, but all four NCLs began to converge at void ratios below e ≈ 0.3. The failure surface of a sand was characterized to mean effective stress P' > 400 MPa using reduced triaxial compression experiments, removing the need to rely on extrapolation from low-pressure data.