With the continuous expansion of urban underground space development, stratum disturbance induced by shield construction has an important impact on the safety of existing underground structures and surrounding environment. Through the independent research and development of the shield tunneling test device, the load of different stratum stress levels was realized, and the change law and influence range of the stratum disturbance in shield construction under different burial depth conditions were analyzed. The results show that the change rate of earth pressure in the strata around the tunnel decreases with the increase of the horizontal distance from the tunnel. The ratio of soil pressure after shield tunneling to initial soil pressure is about 60%-80%. The change of buried depth ratio has little influence on the soil stress path at the vault and bottom. The stratum disturbance degree based on the change of stress is defined, and the stratum disturbance degree gradually decreases with the increase of the burial depth ratio, indicating that the deep burial condition will reduce the disturbance effect of shield excavation on the stratum. After the completion of the shield tunneling, the height of the vertical influence range of the disturbance is between 0.5D and 0.8D above and below the tunnel (D is the diameter of tunnel), the width of the horizontal disturbance range is about 0.5D when the shield reaches the monitoring section, and approximately 1.2D to 1.5D when the shield passes far away.

A series of physical model tests and cyclic triaxial tests were performed on a dry sand to investigate the effects of excavating an adjacent pit on the settlement behaviour of a footing under cyclic loading. The excavation is simulated by moving a retaining wall between loading cycles in the physical model tests. The excavation induced stress disturbance on soil elements is modelled by reducing cell pressure between loading cycles in triaxial tests. The results indicate that nearby excavation leads to reduction in lateral stress in ground and therefore increases the settlement of footing in the subsequent loading cycles. However, there is no clear relationship between the settlement increment and the magnitude of wall movement, when the lateral movement of the wall is within the range of 0.1% to 0.37% of the wall height. The lateral excavation does not have great impact on the influence zone of the footings under cyclic loading. An empirical model is proposed to estimate the cyclic loading-induced strain accumulation of sand with the consideration of lateral unloading effects between loading cycles. After being validated using cyclic triaxial tests results, the proposed model is employed to predict cyclic loading-induced settlement of the footing before and after the excavation.

Changing the deviatoric and spherical stresses could affect the accumulative deformation behaviour of soils under cyclic loading. Drained cyclic triaxial loading tests were performed on saturated sand to study the dependence of cyclic loadinginduced axial and volumetric strain accumulations on changing the deviatoric and spherical stresses in between loading cycles. The change in the stresses was simulated by changing cell pressure and axial load along different stress paths. The variation of axial and volumetric strain accumulations before and after changing the stresses is compared and discussed. It is found that changing the stresses could have different impacts on the axial and volumetric strain accumulations, as the accumulations are affected by different mechanisms. The axial strain accumulation after changing the stresses is affected by the average stress ratio and precedent stress history. The volumetric strain accumulation is hardly affected by changing the stresses unless an increase in the average stress ratio is caused. Both axial and volumetric strain accumulations show independence on the stress path of the disturbance. For the samples with decreasing average stress ratio, the strain accumulation direction after changing the stresses cannot be fully described using Modified Cam Clay flow rule.