Dynamic shear modulus and damping of lightweight sand-mycelium soil

Lightweight geomaterials have been widely used as seismic buffers in geotechnical engineering. A kind of biobased lightweight geomaterial, lightweight sand-mycelium soil (LSMS), which consists of host soil, substrate material (wheat bran), and hyphae, was proposed in this study. To investigate the dynamic properties of LSMS, a series of strain-controlled cyclic triaxial tests were performed. The effect of substrate material content and effective confining pressures on the dynamic properties of LSMS was studied. The results showed that the LSMS is capable of self-sustaining because sand particles and wheat bran are bonded by mycelium from fungal growth. The normalized shear modulus (G(d)/G(0)) of LSMS decreased, and the influence of effective confining pressures on G(d)/G(0) was weakened with increasing substrate material content (W-s). The damping ratio of LSMS was strain dependent, and there is a threshold in the shear strain where the influence of W-s on the damping ratio becomes different. Based on the experimental results, the models considering the influence of W-s on LSMS are proposed for shear modulus and damping ratio characteristics. The dynamic characteristics of LSMS show that as a lightweight geomaterial, it can be used as a seismic buffer.