Permeability Characteristics and Foundation Pit Precipitation Measures of Coral Reef Limestone

The structure characteristics and permeability characteristics of coral reef limestone in East Java, Indonesia were analyzed by engineering geological drilling and water pressure test in borehole. And the foundation pit precipitation measures in coral reef limestone area were studied by field test. The results show that the upper part of the coral reef limestone in this area can be divided into plaster mixed with calcareous concretion of coral reef, fragmented coral reef limestone and columnar coral reef limestone according to the consolidation degree. The permeability rate of coral reef limestone is controlled by the degree development of the dissolved cave inside the rock mass and its connectivity, and the permeability rate of coral reef limestone is inversely proportional to the consolidation degree. The permeability rate of the plaster mixed with calcareous concretion of coral reef is infinite. The permeability rate of fragmented coral reef limestone is 31~74 Lu, and in the local area is infinite. The permeability rate of columnar coral reef limestone is 2.25~17 Lu, which decreases with increasing depth. The direct pumping and drainage measures can not effectively decrease the groundwater level of the foundation pit. The pressure grouting water-resisting curtain can greatly reduce the permeability rate of the coral reef limestone by filling the dissolved caves inside the rock mass, and can be used for the foundation pit dewatering in the coral reef limestone area.