Experimental and theoretical study on the mechanical behavior of flexible pipe joints under differential ground motion

The bearing capacity of buried flexible pipes depends closely on the support provided by the surrounding soil, and the interaction forces between the pipe and the soil are crucial for ensuring the stable operation of the pipeline. When differential ground motion occurs, the flexible pipe is susceptible to angular damage at the joints due to uneven support. This paper investigates the mechanical behavior of flexible pipe joints under differential ground motion through laboratory model test. Using the Winkler elastic foundation beam theory, theoretical formulas are proposed for calculating the rotational angle of flexible pipe joint under conditions of fully released moment, partially transmitted moment, and fully transmitted moment. These proposed formulas are then analyzed and verified using model test data. The research reveals that the deformation of flexible pipe joint is closely linked to the amount of differential ground motion. Compared to the formula for fully released moment joints, using the formula for partially transmitted moment joints yields a more accurate calculation of the rotational angle of the pipe joint under differential ground motion. As the pipe diameter, burial depth, and internal friction angle of the backfill material increase, the maximum allowable differential ground motion that the pipe joint can handle decreases accordingly. Additionally, the joint rotational angle shows trends of linear, logarithmic, and exponential growth, respectively. Furthermore, with the increase in differential ground motion, these growth trends become increasingly pronounced.