Abstract: The load transfer methods for piled embankments are mostly based on 3 soil arching effect models. Most of these methods do not take into account changes of the arching effect mechanism under different fills and parameters for the difficulty of observing the macro soil arching. For each method, the same arch shape is always applied to all the situations. 3 groups of soil arching effect model tests with different pile spacings and sand-filling heights are done by using a model test apparatus. In the model tests, the settlement of soils is controlled by the displacement control device accurately. The soil pressures are measured and the pictures are collected during the settlement continuously and synchronously. Then, the photographic survey technique is used for measuring the overall displacement of the sand fills. The pile-soil pressure ratios are calculated and the feature point in the pile-soil pressure ratio curves are picked out. The force transfer mechanism of the piled embankment with sand fills is discussed. Triangular slide planes in the sand filling and the angles of slide planes’ change with the pile-spacing ratio are discovered. An initial triangular arching effect model is put forward based on these comprehensive analyses. A formula for the pile-soil pressure ratio is derived from the new arching effect model. The pile-soil pressure ratios under the model test situations are calculated by using the Rogbeck method, BS8006 method, Terzaghi method and a new method. The new triangular soil arching effect method is proved to best fit the actual measurements.