Zuochun Li

Sheet piles are extensively used as foundation structures in urban environments. However, the vibrations associated with sheet pile construction can potentially adversely affect existing buildings, as well as cause discomfort to nearby residents. This study aims to analyze ground vibration response during the driving and extraction of sheet piles. To this end, field tests of U-shaped sheet piles were conducted in Beijing silty clay, during which ground vibrations in the near-field were monitored. Subsequently, a numerical model was developed using the coupled Eulerian–Lagrangian method to simulate the pile–soil interaction characteristics and to investigate ground vibration intensity in the far-field. The research results indicate that the ground vibration response modes during the driving and extraction of sheet piles are distinctly different. Due to the entry effect, the critical depth during pile driving typically occurs in shallow soil layers, while during pile extraction, the critical depth generally corresponds to the pile’s embedded depth to overcome the soil locking effect. Ground vibrations rapidly decrease in the near-field (6 m), the attenuation rate significantly slows down. Vibrations can be widely perceived by residents at radial distances of less than 12 m. Through a systematic assessment, it was concluded that sheet pile construction is unlikely to directly damage surrounding buildings but may inconvenience nearby residents. Additionally, a parametric analysis of the vibration source revealed that appropriately adjusting the driving frequency and amplitude can effectively reduce vibration levels.

Acrylate is a popular polymer grouting material that has been widely used to control groundwater seepage. However, the vulnerability of acrylate slurry to dynamic water washout restricts its application in groundwater environments characterized by high flow velocity and water pressures. In this paper, lithium bentonite (Li-B) was used to modify the traditional magnesium acrylate (AC) grouting material. The influence of Li-B to AC ratios on the modified materials’ washout resistance was explored, and the modification mechanism was analyzed using X-ray diffraction (XRD), infrared spectroscopy (IR), and scanning electron microscopy (SEM). Finally, the anti-washout ability of the modified slurry was verified through engineering applications. Results revealed that LiB-AC grout had adjustable setting times (10.5 to 395.6 s), minimal bleeding (0.1%), higher viscosity (65 mPa·s) and expansibility (350%), stronger anti-water dispersibility (24 times that of pure AC slurry), higher mechanical strength (compressive strength is 0.386 MPa, tensile strength is 0.088 MPa), and better impermeability (2.23 × 10⁻⁸ m/s). The lithium bentonite was beneficial to the setting time, bleeding, viscosity, slurry retention rate, impermeability, and mechanical strength of the acrylate grout. However, it diminished the expansibility of the acrylate grout. At the optimal acrylate content (20%), the mechanical strength and impermeability of the LiB-AC grout were the highest. The better performance of LiB-AC grout was attributed to the formation of a more stable and dense interlaced spatial network structure after the modification by Li-B. The LiB-AC grout was used in the dynamic water grouting project of a metro shield tunnel segment and achieved better anti-washout performance than cement-water glass and pure AC slurry.