摘要：In recent years,a new type of foundation named composite piled raft foundation (also called long short composite piled raft) has been *** designing shallow foundations would mean unacceptable settlement,or other environmental risks exist which could impair the structure in the future,composite piled raft foundations could be *** element method was applied to study the behavior of this type of foundation subjected to vertical *** order to determine an optimal pile arrangement pattern which yields the minimum settlement,various pile arrangements under different vertical stress levels were *** show that with increasing the vertical stress on the raft,the effectiveness of the arrangements of short and long piles become more *** addition,a new factor named "composite piled raft efficiency" (CPRE) has been defined which determines the efficiency of long short piles arrangement in a composite piled raft *** factor will increase when short piles take more axial stresses and long piles take less axial *** addition,it is found that the changes in settlements for different long short piles arrangement are in a well agreement with changes in values of CPRE ***,CPRE ratio can be used as a factor to determine the efficiency of piles arrangements in composite piled raft foundation from the view point of reducing raft settlements.