This study aims to develop a nonlinear constitutive model to address the mechanical properties of magnesia-cement- solidified soil under different contents of solidified agent (Wg) on the basis of the results of a series of laboratory tests. Firstly

a new type of environmentally magnesia cement composite curing agent was adopted to solidify the sludge. Then

the scanning electron microscope (SEM) tests

the one-dimensional consolidation tests and the undrained triaxial tests were carried out on the magnesia cement solidified soil with different contents of Wg. The test results show that there exists a strong structure in the inner of the magnesia-cement-solidified soil and the associated structural yield stress becomes larger and larger with the increase of Wg. The cohesion between the soil particles increased due to the binding material produced by the hydration reaction

which produces the material to fill the soil void. As such

the stress-strain behaviour of the magnesia-cement-solidified soil transformed from work hardening to work softening. Based on the aforementioned test results

a constitutive model was developed to investigate the transformation of the stress-strain relationship of the magnesia-cement-solidified soil

in which the effect of solidified agent content (Wg) could be also accounted for. The numerical examples show that the proposed constitutive model behaves well in predicting the stress-strain behaviour of the magnesia-cement-solidified soil at any amount of Wg.