A New Classification Method of Karst Vertical Morphology in Bridge Site Area Based on Drilling Data

Finding out the karst vertical morphology is the key to determine the bridge foundation form and pile-end position. A new classification method of karst vertical morphology based on drilling data is proposed in this paper and applied to the analysis and evaluation of bridge foundation. In this paper, the CW Bridge in Longzhong County of Hubei Province is taken as an instance, it is proposed that the karst cave floor elevation is the primary index, and the limestone top elevation and the karst cave accumulated height are the secondary indexes, through the statistical analysis of karst development elevation, buried depth and height, etc. As well as, two concepts of shallow corrosion datum and shallow corrosion height are put forward. Based on the karst borehole data, shallow corrosion datum and shallow corrosion height, the karst vertical morphology zoning map is drawn, which is divided into four zones in the vertical direction. According to the different combinations of limestone top elevation and karst cave floor elevation located in zone, the karst vertical morphology is divided into four categories. Finally, different types of karst vertical morphology are summarized and the classification method of karst vertical morphology is formed. The results show that the classification method of karst vertical morphology proposed could not only describe the karst vertical morphology in the bridge site area in detail and identify the karst development intensity, but also determine the reasonable foundation form and pile-end position. Through a large number of engineering practices, this method could guide the engineering design and construction effectively.