SETTLEMENT OF COMPOSITE FOUNDATION – A CASE HISTORY WITH REINFORCEMENT OF STEEL PIPE MICRO-PILE

Jianping Sun , Junhua Xiao , Qingpeng Wang

ABSTRACT: This paper presents a case history of high-rise building that is located in deep alluvium deposits with composite foundation. When the building construction approached completion, the monitoring data showed that the foundation settlement and the latest settlement rate was approaching or far more exceeding the control values. Foundation reanalysis demonstrated that even though the foundation capacities could satisfy the design requirement, the total final settlement would be more than 200mm due to the thick compressible soils, which couldn’t meet the designed settlement requirement. To guarantee the building security, steel pipe micro-pile as settlement reducer was utilized for its clean construction environment to control post-settlement. The total 624 micro-pile of 18 meter long and 30mm in diameter had been pressed tipping into fine sand layer within 50 days. During and after micro-pile construction, settlement monitoring was carried out by the settlement remarks installed at the columns. The monitoring data demonstrated that during the reinforcement construction the building steadily settled down due to construction disturbance and the differential settlement almost could be negligible. Six months later the settlement tended to convergence and the settlement rate had satisfied the relevant code standard. The method of foundation reinforcement is feasible and successful.

Keywords: Composite foundation, foundation settlement, steel pipe micro-pile; foundation reinforcement, monitoring data.