Application of concrete-cored DCM piles in soft subgrade improvement of expressways

The reinforcement effect, load distribution and transfer mechanism are studied by means of the field tests on an engineering example of deep soft soil ground of highway reinforced by concrete-cored DCM piles. The results indicate that the control effect of settlement and horizontal displacement by using the concrete-cored DCM piles is better than that by using the DCM columns, and the differential settlement of subgrade cross section is small. The settlement occurs mainly in the range from the pile top to the bottom of precast core piles. The negative friction lies at the upper of concrete-cored DCM piles and the neutral point is located in the one third length of concrete core. The value of pile-soil stress ratio is 20007E;3 times that of the DCM columns and close to that of rigid piles. The embankment load is mainly shared by piles. The pore pressure of the composite ground with concrete-cored DCM piles rapidly decreases. The work characteristics of concrete-cored DCM piles of the composite ground with under embankment load are different from those obtained from the plate load tests. Finally, considering the control of settlement and bearing capacity the design method for the composite ground with concrete-cored DCM piles is introduced.