Abstract: The limiting state equations are established based on the consolidation design parameters that are calibrated with the monitoring data from the case histories. The equivalent reliability indices of the variables in the current design code are identified. The structure importance factor and the resistance factor for the embankment stability are adjusted based on the reliability theory on the soil improvement projects. The limiting state design approach of the horizontal drainage method is established. In the paper, the soil improvement design for the case histories of XinChang and GuangZhu railway projects are compared with both conventional and limiting state approaches. The results indicate that both methods yield similar results.

Key words: Horizontal Drainage Method, Limiting State Design Method, Itemized Factors.