The Geological Characteristics of Buried Karst and Its Impact on Foundations in Hong Kong, China

In the past 20 years, new towns development in Hong Kong resulted in the discovery of areas of buried marble and karstic cavities. The buried karst has caused serious problems which significantly impact on foundation design and construction. Carbonate rocks include Carboniferous marble, Permian limestone and. Jurassic marble clast-bearing igneous rocks. These different carbonate rock types show various degrees of karst development. Based on a detailed ground investigation, the most intense karst development and the largest cavities occur in massive pure marble, in which the karst zone can extend to depths of more than –127 mPD. The degree of karst development of impure marble is less than that of pure marble. Marble clast-bearing igneous rocks show the least karst development, with large cavities being rare and smaller-scale honeycomb weathering being more typical. The influence factors of buried karst on foundation engineering are also recognized. These factors include geological structure, rock types, hydrogeology, paleogeomorphology and geomechanics. Among these factors, correct classification of rock types is very important in the design of ground investigation and construction works. The misinterpretation may increase property development costs substantially.