This paper investigates the pullout behaviours of horizontal rectangular plate anchors under inclined loading in sand using three - dimensional finite element (3D-FE) analysis. An advanced bounding surface plasticity model incorporating the critical state framework is developed to capture the stress-strain relationship of sand. The model is firstly validated against various analytical solutions and centrifuge test data. Then, a series of FE analysis is conducted to consider the effects of plate anchor aspect ratio, initial embedment depth, sand relative density and inclined loading angle on the pullout capacities. Results show that shallow anchors develop failure zones reaching the soil surface, and vertical pullout capacity exceeds that under pure vertical loading when the load is slightly inclined. For deep anchors, failure zones are confined below the surface, and horizontal pullout capacity exceeds that under pure horizontal loading when the load is slightly inclined. The transitional embedment depth depends on anchor aspect ratio and sand density. A modified analytical solution is proposed to estimate the vertical pullout capacity of plate anchors from shallow to deep depths. Failure envelopes established from probe tests provide practical guidance for assessing rectangular anchor failures under various inclined loadings.
