Abstract: Model tests on rectangular closed diaphragm walls a new type of bridge foundation,were conducted.In the tests,the load transfer mechanism,distribution and development of inner shaft resistance,outer shaft resistance,soil resistance under the cap were studied.It was observed that the vertical load bearing capacity of closed diaphragm walls was composed by the inner shaft resistance,outer shaft resistance,toe resistance and soil resistance under the cap.The outer shaft resistance was developed from the top of the wall to the toe.On the contrary,the inner shaft resistance was developed from the toe to the top.For the "weakening effect" of the cap,the top inner shaft resistance was close to 0.Distribution character istics of the soil resistance under the cap were that the soil resistance in the corner was the largest,secondly in the border and thirdly in the center.With the increase of load,the shaft resistance increased slowly and its load-shearing percent decreased gradually.At the same time,the increments of toe resistance and soil resistance under the cap were enlarged gradually,and the most of load increment was partaken by the toe resistance and soil resistance under the cap.