With the rapid development of metro construction, shield machines inevitably have to traverse a variety of complex geological conditions, leading to the frequent occurrence of geological disasters, equipment failures, building vibration and other problems. Vibration, as an important feature of the shield tunneling process, has received more and more attention in recent years. This paper summarizes the relevant research progress of vibration monitoring during shield construction from 2015 to 2023. It analyzes the shield vibration generation mechanism, monitoring methods and application areas. Firstly, the shield vibration type is divided into mechanical vibration triggered by internal excitation and forced vibration triggered by external excitation, and the principles of vibration generated by shield main bearing, gearbox and disc cutter are discussed. Then, the commonly used vibration monitoring methods are outlined according to the installation location of the sensors (inside and outside of the shield). Finally, the applications of vibration signals in the diagnosis of shield faults, the identification of geologic conditions, and the evaluation of the current status of the interference with the buildings are summarized. This paper discusses the development trend of vibration monitoring during shield tunneling based on the current research situation and the current technology level, which provides valuable insights to enhance the safety and intelligence of shield construction.

In recent years, geological disasters such as water inrush during drilling and blasting operations have posed significant challenges in tunnel engineering. This paper presents a novel continuous-discrete coupling method based on LS-DYNA, combining the finite element method (FEM) and smoothed particle hydrodynamics (SPH), to simulate the water inrush phenomenon in blasting engineering. The proposed FEM-SPH model effectively captures the propagation of explosion shock waves, simulates small deformation areas with solid grids, and models water behavior using SPH. This study systematically investigates the dynamic evolution of water inrush, divided into three distinct phases: the rupture of the water-resistant rock layer, the emergence of fluid-conducting channels, and the onset of large-scale water influx. Results indicate that under blasting load, the stress of the surrounding rock increases sharply, leading to instantaneous water inrush. The FEM-SPH model demonstrates superior performance in simulating the complex interactions between blasting stress waves, water pressure, and rock mass damage. This research provides new insights and methods for water control in tunnel engineering and offers significant potential for preventing water inrush disasters in underground construction.

The durability of cement mortar in structural engineering is very important to the structural safety and stability, especially under the action of sulfate erosion, and the deterioration speed is faster and more serious. However, the fracture performance of mortar is not clear, so this paper studies the durability and fracture energy law of cement mortar in structural engineering in the process of sulfate erosion. The sulfate corrosion test of ordinary Portland cement mortar with water-cement ratio of 0.4, 0.5 and 0.6 was carried out. The appearance damage of specimens was observed at different erosion ages and the content of sulfate ions in the samples was measured. And the permeability and transmission law of sulfate in cement mortar were studied. The results show that the sulfate attack on the mortar is from the surface to inside, and the smaller the water cement ratio is, the stronger the ability to resist sulfate attack. With the deep penetration depth, the free sulfate ion content And the content of free sulfate ions decreased with the decrease of water-cement ratio. In contrast, the content of sulfate ions in the reaction increased first and then decreased, and finally stabilized. For the mortar surface, the smaller the water-cement ratio, the more the content of sulfate ions, and for the mortar interior, high water-cement ratio of the reaction of the sulfate ion content of the reaction is higher. In the fracture energy aspect, the test pieces with small water-cement ratio first increase and then decrease, and the bigger the water-cement ratio is, the shorter the age of fracture initiation is.

Numerical dispersion limits the accuracy of finite-difference elastic-wave modeling, particularly when relatively short spatial stencils are used. This study evaluates staggered-grid spatial-derivative coefficients obtained using a constrained simulated-annealing procedure and compares their spectral and numerical behavior primarily with Taylor-expansion coefficients within the same numerical framework. The coefficient design minimizes the maximum absolute spectral approximation error over a prescribed normalized-wavenumber interval while enforcing first-derivative consistency and an alternating, decreasing-magnitude coefficient pattern. The homogeneous and modified Marmousi examples indicate reduced visible dispersion relative to Taylor coefficients at the same stencil half-length. Least-squares coefficients are retained only as an additional qualitative reference in the homogeneous-model tests. The conclusions are limited to the tested two-dimensional isotropic models, grid spacing, time step, and source frequencies.