Pressure characteristics of rectangular box jacking considering box-soil-lubricant interaction

As a lubricant, bentonite slurry is widely used in rectangular box jacking projects with large lengths and large sections under complicated geological conditions. Furthermore, the box-soil-lubricant interaction strongly influences the pressure distribution of the box segment. To determine the pressure characteristics of rectangular box jacking under the box-soil-lubricant interaction, this study considers the data of contact pressure around the box during the entire construction period of the Suzhou Yuanhetang rectangular box jacking project, and the temporal and spatial distribution characteristics of the contact pressure under lubricant injection are discussed. Then, the box-soil-lubricant contact model is established, and the calculation methods for the vertical earth pressure and friction resistance are proposed on the basis of this model. Finally, the theoretical models and methods are verified using the field measured data. The results show that the contact pressure around the box varies during the process of lubricant injection and dissipation, and the contact pressure at different positions of the box segment is markedly affected by the lubrication conditions. Further, one side box-soil interaction is the primary contact status resulting in a distinct lower limit of the contact pressure at each position of the box segment. The measured contact pressure and jacking force can be effectively included within the ranges of the proposed calculation methods, which can a serve as a reference for predicting the friction resistance and contact pressure.