Development and application of a piston-type dual-mode ultra-low disturbance core sampling drilling tool

Abstract:

To address the technical challenges encountered during ICDP lake drilling， specifically， frequent encounters with fluid-plastic lacustrine silt （water content>80%， penetration resistance<10kPa） where conventional coring methods and drilling techniques for small-diameter cores result in high core disturbance and low recovery rates， a ?122.60 mm small-diameter piston-type dual-mode sampler was innovatively developed. Utilizing a triple-tube， non-rotating penetration design and hydrostatic control technology， this system successfully recovered lacustrine silt core samples over 58 runs totaling 127.40m in length from the depths of below 101.70m water during the Second Tibetan Plateau Scientific Expedition at Nam Co Lake， Tibet. The cores exhibited a disturbance coefficient η of less than 0.15 and a recovery rate of more than 80%， representing a major breakthrough in low-disturbance coring. The CL-1G borehole reached a final depth of 510.20m， setting a new domestic record for drilling depth in high-altitude deep-water lakes. This technology provides critical drill core samples for reconstructing the glacial-interglacial climate evolution sequence of the Tibetan Plateau， offering valuable data for paleoenvironmental reconstruction and future climate prediction. The successful application of this sampler significantly enhances core quality and achievable drilling depth limits in lake sediments， particularly in ultra-soft plastic formations， providing reliable technical equipment support for global paleoenvironmental research in deep-water lakes.