Characteristics of stresses and settlement of ground induced by train

By introducing the concept of equivalent stiffness, solutions of stresses in the ground induced by train are obtained based on the model of an Euler-Bernoulli beam on the elastic half-space subjected to the moving load. The characteristics of stresses in the ground including the spatial stress distribution and the stress path are studied. It is found that stresses induced by the train increase with the increasing of the moving speed of the train, and their values will be considerable if the moving speed of the train approaches the Rayleigh-wave speed of the soil. The stress path of the soil is very complex even for those elements beneath the central motion line of the load. Dynamic triaxial tests are carried out to study the dynamic properties of soft clay under train-induced stresses, in which those stresses are simplified as cyclic sinusoidal loadings. Dynamic strength of natural clay and remolded clay as function of the number of cycles is presented. Dynamic strength of the former decreases rapidly with the increasing of confining pressure and then goes to an asymptotic value, but the influence of confining pressure on the dynamic strength of the latter is limited. Based on the theoretical results and the limited minimum cyclic strength obtained by tests, the settlement of ground surface induced by train is estimated. Large settlement might happen due to destruction of the soil structure, accumulation of the deformation and enlargement of the disturbed area.