Analytical prediction for tunnelling-induced ground movements in sands considering disturbance

• A series of triaxial tests were performed to study the effect of the initial relative density on the properties of sands.
• A general disturbance function considering the relative density was proposed based on the classical DSC theory.
• Relationships between the shear modulus and the disturbed degree were obtained.
• An analytical solution was proposed for predicting the ground movements with consideration of construction disturbance.

Construction inevitably leads to the disturbance to soils, which will change the properties of soils. Therefore, the physical and mechanical parameters obtained by the laboratory tests only reflect the properties of soils at a certain state, but not the true properties of soils during the whole process of construction. It is found that the initial relative density has a strong effect on the strength-deformation properties of sands on basis of a total of twenty-four triaxial compressed tests of dry sands. Based on Disturbed State Concept theory (Desai, 1974), a unified disturbance function is proposed by taking the relative density as the disturbance parameter. Furthermore, a novel approach that related the shear modulus with the degree of disturbance is developed. Then, according to former studies (Kondner and Zelasko, 1963 and Kondner and Horner, 1965) and the proposed approach an analytical solution for ground movements considering construction disturbance is established. To study the validity of the proposed analytical solution one example is analyzed. It is found that both the positive (decrease in relative density) and negative (increase in relative density) disturbance have an obvious influence on the ground movements of the soil around the tunnel. The construction disturbance should be considered in predicting the ground movements by using the analytical solution.