High pressure jet grouting can directly reinforce weak soil layers of soft soil foundations. In order to investigate the reinforcing functions of the direct reinforcement of weak soil layers to foundations

a group of model tests of natural foundations on weak soil layers and reinforced foundation is performed in comparison. In order to form reinforced foundation

a group of 3×3 piles is set in the weak soil layers.Test results show that direct reinforcement method of weak soil layers can greatly improve foundational settlement characteristics and bearing capacity. Upon reinforcement

piles are noted for good transfer loads

greatly reducing the compression of weak soil layers. Pile top load increases linearly with the increase of applied loads

and top loads of corner piles are the biggest

that ones of side piles are second

and that ones of center piles are smallest. Upper part of piles are subjected to negative friction

lower part of piles are subjected to positive friction

and the maximum axial force for pile is located 25 cm from the pile top. The average pile-soil stress ratio of reinforced area decreases with load increasing.