Numerical Analysis of Screw Micropiles Under Lateral Loads via BNWF Method
摘要
Screw micropiles are a new type of pile designed for lightly-loaded structures, generally available in small diameters compared with traditional driven or cast-in-place piles, and include threads along the middle and the bottom portions. However, there is a lack of research on their complex soil-pile interactions under lateral loading. To address this, a numerical model was developed using the Open System for Earthquake Engineering Simulation (OpenSEES) platform, employing the Beam-on-Nonlinear-Winkler-Foundation (BNWF) method to simulate the lateral behavior of screw micropiles in both cohesive and cohesionless soil. The models comprehensively considered various soil-pile interactions, including lateral shaft resistance, vertical shaft resistance, thread bearing resistance, and lateral thread resistance. These interactions were modeled using zero-length elements with p-y, t-z, q-z, and th-y uniaxial spring materials. The numerical model was then validated by comparing the results with lateral load field tests on both instrumented and un-instrumented screw micropiles. The results showed that the numerical model predicted the lateral capacities and load behavior of screw micropiles adequately. By examining the mobilization of various soil-pile interactions, it was validated that the lateral response was predominantly influenced by the lateral shaft reaction, while the impact of the lateral thread reaction was minimal. Finally, sensitivity analyses were conducted to examine the effect of soil properties and pile geometrical features on the lateral response.