Comprehensive survey technology for bridge pile foundation in pebble karst area

In highly developed pebble karst strata, there are problems such as low drilling efficiency, severe mud leakage, unstable hole walls that are prone to collapse, low rock core recovery percent during bridge pile foundation survey and construction. Moreover, drilling alone cannot accurately determine the spatial distribution of karst, which has a significant impact on engineering design. This article relies on a bridge pile foundation survey project, using a fully hydraulic drilling rig to combine multi-stage steel casing wall protection, SM plant rubber wall protection, down-the-hole hammer eccentric follow-up drilling, diamond rope coring, semi-closed action double tube coring, and other technologies for drilling and coring. The high-density electrical method was used to preliminarily delineate the development range of karst, and the cross-hole seismic wave CT method was used to further investigate the distribution of karst between boreholes. The tube wave method was used to detect each pile one by one, providing a reliable bearing layer for bridge pile foundations, forming a comprehensive survey technology that can be promoted and applied in similar geological surveys.