Study on the Influence of Sampling Technology on the Quality of Soil Sample in Saturated Soft Clay

Obtaining undisturbed high-quality samples is a challenge in geotechnical investigation, and soil samples will be disturbed to some extent in the process of drilling and sampling. In order to study the influence of sampling technology on the quality of soil samples when sampling in saturated soft clay strata, this paper takes a typical silt in Wenzhou, Zhejiang Province, as the research object. Firstly, the stratigraphic distribution of the site was understood by cone penetration test (CPT). Then, comparative tests on the quality of soil samples were conducted by using cryptomorphic shaft-valve type soil sampler, conventional thick wall sampler and open end thin wall sampler, respectively. Through a comparative analysis and research on the appearance morphology, unconfined compressive strength and sensitivity index, disturbance index of soil samples, a quantitative analysis and evaluation of the influence of different sampling technology on the quality of soil sample of the saturated soft clay was finally obtained. The results of the study showed that using the cryptomorphic shaft-valve type soil sampler has the least disturbance and the highest quality on sampling, the open end thin wall sampler is the second, and the conventional thick wall sampler has the highest disturbance and the worst quality. The cryptomorphic shaft-valve type soil sampler has 20.2% higher unconfined compressive strength average value than the conventional thick wall sampler and 10.3% higher than the open end thin wall sampler. Using the rate of change of pore ratio under self-weight stress as a quantitative indicator of the magnitude of soil sample disturbance, the conventional thick wall sampler with the worst soil quality has 11.0% greater than the average value of the best cryptomorphic shaft-valve type soil sampler. The sampling technology of the cryptomorphic shaft-valve type soil sampler takes soil samples of relatively highest quality in saturated soft clay, and the geotechnical parameters obtained after the test are relatively close to the physical and mechanical characteristics of the real stratum.