Axial stress–strain relationships of fine roots of Beech and Larch in loading to failure and in cyclic loading

Abstract

Vegetation roots contribute to the bearing capacity and stability of soils. In existing models of soil reinforcement by roots (land slide models), axial stress–strain relationships of roots play a central role. Such relationships were measured on fine roots of beech and larch. Results of loading to failure are presented by failure stress and failure strain. Results of cyclic loading are presented for each loading cycle by overall moduli of stiffness in loading and unloading, and elastic and plastic strain increments. The thinnest roots lost up to 60% of their water content during loading to failure, and showed failure strains up to 16%. The shape of the stress–strain curves was non-linear, but independent of diameter of tested roots. The modulus of stiffness was relatively low and incremental plastic strain was relatively high for the first loading cycle. The incremental plastic strains in cyclic loading tended to decrease with increasing root diameter.