Disturbance of shield tunnel excavation and compensation grouting to surrounding soil: laboratory tests and numerical simulations

Compensation grouting, as an effective remedial measure, is often adopted to deal with the soil loss engendered in shield tunneling. The model tests with two different scales in dry sand are performed to investigate the disturbance of tunnel excavation and compensation grouting to the surrounding soil. By “tunneling” and “grouting” sequentially in the test, the effect of compensation grouting on both surface settlements and soil stresses in the presence of soil loss is studied. The test data indicate that the surface settlements caused by tunnel excavation can be effectively predicted by the Peck formula, and the maximum settlement value is approximately proportional to the volume loss. During the stage of tunneling, the soil can be divided into three zones corresponding to the stress changes, i.e., the positive arching zone, the unloading zone and the plastic zone. During the stage of grouting, the soil can be divided into two zones according to the stress changes, i.e., the effective upheaval zone and the arching compensation zone. The two-dimensional finite element analysis considering small-strain behavior of the soil is carried out to reproduce the test data, and the simulated results correspond well to the test data, helping to further validate the disturbance mechanism by both “tunneling” and “grouting” revealed in model tests.