Study on the net buoyancy dissipation characteristics of synchronous grouting in shield tunnels and its effect on segment floating[J]. Chinese Journal of Geotechnical Engineering. DOI: 10.11779/CJGE20240857
Citation:
Study on the net buoyancy dissipation characteristics of synchronous grouting in shield tunnels and its effect on segment floating[J]. Chinese Journal of Geotechnical Engineering. DOI: 10.11779/CJGE20240857
Study on the net buoyancy dissipation characteristics of synchronous grouting in shield tunnels and its effect on segment floating[J]. Chinese Journal of Geotechnical Engineering. DOI: 10.11779/CJGE20240857
Citation:
Study on the net buoyancy dissipation characteristics of synchronous grouting in shield tunnels and its effect on segment floating[J]. Chinese Journal of Geotechnical Engineering. DOI: 10.11779/CJGE20240857
In view of the problem of segment floating that often occurs during shield tunnel construction, the variation rule of net buoyancy with time in typical single-component grout and two-component grout has been revealed through the self-developed test device, and the ExpDec2 model has been used to establish the general mathematical expression for the change of net buoyancy with time. Subsequently, considering the net buoyancy dissipation characteristics of the grout, the self-weight of the segment, the shield thrust, the ground load and the shield tail constraints, the ABAQUS is used to establish the computational model of the segment floating. The floating pattern of segment lining structure under the action of typical single-component grout and two-component grout is proved, and the reasonableness of numerical calculation is verified by the measured data of the actual project. The results show that: 1) The process of grout net buoyancy dissipation with time can be divided into two stages, which is the linear section and curve section. And when the net buoyancy falls to zero, the grout is still in the state of flow plasticity, far from reaching the final setting time; 2) The established calculation model of segment-grouting can reveal the floating characteristics of the segment wrapped by the gradual cementing grout, which is basically consistent with the measured data and can provide a basis for the design of segment floating; 3) Compared with single-component grout, the buoyancy dissipation time and physical final setting time of two-component grout are very short, which can quickly restrict segment and greatly reduce the amount of segment floating. Therefore, if the floating of the segment is serious in the actual project, a grout with fast setting time and high early strength is recommended.