Abstract: A deep excavation site in Guizhou was in the read clay soils. After completion of the drilling of the planned double row supporting piles, the design excavation depth increased by three meters. After further evaluation, it was decided to maintain the original double row pile supporting structure with additional internal support with rakers. Other measures, improved walers, increasing the reinforcement in the cast-in-place concrete piles, preserving the rock layer in front of the soldier pile were also utilized. Furthermore, the construction monitoring results indicated that the strength of red clay is higher than the code suggested reduction values. The paper also recommends that geotechnical investigation during construction should be performed so that the site conditions could be better understood. The recommended horizonal displacement value at the bottom of the excavation should be 5 mm.

Key words: Deep Excavation, Red Clay, Deformation Monitoring, Informative Construction, Double Row Piles