Abstract: Even during the final design stage, the complete distribution of the karst cavities under the proposed site is not possible. Usually, the rock pinnacles are well developed in these areas and a large amount of saturated loose sand with mud and abundant groundwater are existed in soil and rock interface. During the foundation excavation for the shallow foundation on natural soils, the poor and saturated soils are very difficult to be removed and the potential safety hazards are existed due to the underlying karstic cavities. The grouting method is a conventional ground improvement method for the karst soil treatment. However, due to the well-developed rock fissures, the result of the grouting is very difficult to predict, and the rock fissures cannot be completely filled. Therefore, the pipe piles can be applied to carry portion of vertical loads. This paper presents a high-raised residential building ground improvement case history of applying the grouting method and the pipe piles. The monitoring results indicate that no differential settlement was occurred and the cracks on the basement wall had no further development.

Key words: Grouting, Steel Pipe Piles, Karst Cavities, Ground Improvement