Abstract: Gneiss and granite bedrock are widely distributed in the southeast of Shandong Peninsula, and the bedrock is shallow deposited or even exposed. A typical soil/rock profiles that is frequently encountered in the deep excavation projects consists of the following special strata that is locally called “soil overlying bedrock”, namely, from top down: Quaternary unconsolidated deposits; strongly weathered bedrock and moderately to slightly weathered bedrock. This paper presents a case history of deep excavation supporting structure that is consisting of anchored concrete filled, point bearing steel pipe pile in the upper soil layer and rock socketed micropile with rock anchors in the lower bedrock layer. This supporting structure has the advantages of cost effective and high efficiency. Compared with drilled and castinpace concrete piles, this supporting structure can be easily installed in the bedrock layer. Based on the analysis and construction monitoring results, the supporting system could meet the deformation requirements of the deep excavation and the safety of the adjacent structures and utilities were warranted.

Key words: deep excavations, point bearing piles, soil overlying bedrock, concrete filled concrete piles, deformation