In recent years, shield tunneling has shown many advantages with the development of underground rail traffic. Geological exploration plays a significant role in tunnel engineering, and detailed geological exploration results can guide the successful construction of a tunnel. This research relies on a super large-diameter shield tunnel construction, using microtremor exploration technology to collect data onsite. Combined with a comparative analysis of the borehole surveying, the reliability of microtremor exploration technology is verified. Moreover, the monitoring result of the impact of large-diameter slurry balanced shield construction on the surrounding environment is analyzed. The results show that microtremor exploration can obtain geological details that traditional detection methods cannot obtain, which can predict the possible local geology mutation in front of the tunnel in advance. The law of surface settlement curve conforms to the Peck formula. This can be divided into five stages: micro deformation, extrusion uplift, reciprocating uplift, detachment settlement, and consolidation settlement. The surface settlement on the eccentric loads side is more prominent. The maximum pressure outside the tunnel segment appears on the lower side of the monitoring section, approximately 0.41 MPa, which will increase with the grouting pressure and become stable in five days.

An exact solution is proposed to study the time-harmonic torsional vibration of an elastic pile embedded in a radially inhomogeneous saturated soil. The radially inhomogeneous saturated soil is composed of inner disturbed and outer semi-infinite undisturbed concentric annular regions, with the shear modulus of the inner region changing in an exponential form along the radial direction. The governing equation of each region of the saturated soil is solved through rigorous mathematical derivation and the soil torsional impedance is derived with an exact and explicit expression. Making use of the boundary and continuity conditions of the pile-soil system, the torsional complex stiffness at the pile top is obtained in an exact closed form in the frequency domain. Selected numerical results are presented to investigate the influence of the radial inhomogeneity of the surrounding soil on the vibration characteristics of the pile-soil system.

Synchronous grouting slurry is widely used in shield tunnel construction to fill the gaps between stratum and shield tail segments. However, as grout is nearly liquid in the initial stages, the tunnel lining segments recently separated from the shield tail are easily affected by the upward buoyancy generated by grout, causing issues such as longitudinal misalignment and opening of ring joints. Therefore, studying the upward buoyancy characteristics of synchronous grout is crucial. In this study, floating characterisation parameters of grout were investigated using buoyancy model tests, orthogonal tests, and comprehensive tests. The floating characterisation parameters are affected by distribution ratio and types of each grout component. The relationship between the floating characterisation parameters of grout and buoyancy was established. The results show that density, flow index, and shear strength can be used as the floating characterisation parameters. Binder–sand and water–binder ratios have the largest impact on the density. The bentonite–water ratio exerts a primary influence on the flow index, while the water–binder ratio contributes a secondary effect. In addition, bentonite–water and binder–sand ratios have the greatest effect on the shear strength. Furthermore, the particle size of sand and type of bentonite considerably influence the flow index and shear strength. A high-shear grout using well-graded fine sand and a high mesh of sodium bentonite was considered in this study. When the content of bentonite exceeds 7% (P2.2), Archimedes’ law is not applicable for calculating the upward buoyancy of grout. Buoyancy supply rate exhibits gradual enhancement with flow index elevation, yet with diminishing growth rates.

Synchronous grouting slurry is widely used in shield tunnel construction to fill the gaps between stratum and shield tail segments. However, as the grout is nearly liquid in the initial stages, the pipe segment rings recently separated from the shield tail are easily affected by the upward buoyancy generated by the grout, causing issues such as longitudinal misalignment and opening of ring joints. Therefore, studying the upward buoyancy characteristics of synchronous grout is crucial. In this study, floating characterisation parameters of grout were investigated using buoyancy model tests, orthogonal test, and comprehensive test. The floating characterisation parameters are affected by distribution ratio and types of each grout component. The relationship between the floating characterisation parameters of grout and buoyancy was established. The results show that density, flow index, and shear strength can be used as the floating characterisation parameters. Binder–sand and water–binder ratios have the largest impact on the density, while the bentonite–water ratio affects flow index the most. In addition, bentonite–water and binder–sand ratios have the greatest effect on the shear strength. Furthermore, the particle size of sand and type of bentonite considerably influence the flow index and shear strength. A high-shear grout using well-graded fine sand and a high mesh of sodium bentonite was considered in this study. When the content of bentonite exceeds 7% (P2.2), Archimedes' law is not applicable for calculating the up-ward buoyancy of grout. Buoyancy supply rate exhibits gradual enhancement with flow index elevation, yet with diminishing growth rates.

The axial force in assembly steel struts with servo systems is a critical indicator of stability in foundation pit support systems. Due to its high sensitivity to temperature variations and direct influence on the lateral deformation of the foundation pit enclosure structure, accurate prediction is essential for safety monitoring and early warning. This study proposes a novel method for predicting the axial force in assembly steel struts with servo systems based on a spatiotemporal adaptive network. The method begins by feeding historical axial force data from multiple steel struts into an LSTM network to extract temporal sequence features. A self-attention mechanism is then employed to capture the global dependencies within the axial force data, enhancing the feature representation. Concurrently, a convolutional neural network (CNN) is utilized to extract local spatial features. Additionally, excavation depth and excavated soil stratification data are processed through convolutional operations to derive stratification-related features. Subsequently, the temporal and spatial features of axial force are fused with stratification-related features derived from excavation data and further refined through a CNN, enabling more accurate predictions. Validation using deep foundation pit data from a metro station in Zhejiang Province demonstrated the method’s reliability and improved performance across multiple metrics compared to the existing approaches.

Using servo steel support system for active control of deformation during foundation fit excavation has high superiority. To investigate the coherence of the servo support axial force, PLAXIS 3D is used to carry out numerical analysis on the coherence of the axial force applied by the construction and compare with the field test results; Field tests were conducted on the diaphragm wall joint deformation during the axial force application based on the principle of the generation of axial force coherence. The results show that the farther away from the active axial force, from which suffered get the smaller influence, and the size of the applied axial force’s effect on the support in other directions in the order of horizontal, vertical, and oblique. Moreover, the higher the application position of the active axial force of the servo support, the greater the lateral axial force loss rate generated by other supports, while the opposite in vertical axial force loss rate is true. The maximum axial force loss rate is 19%. The deformation of the diaphragm wall joint in the servo steel support zone is more significant than that in the pre-stressed steel support zone. The deformation of the joint will, in turn, affect the axial force.