Abstract: In urban and mine geological exploration,obtaining undisturbed soil samples for related indoor tests is one of the important ways to acquire geotechnical parameters.However,the process of drilling and soil sampling will cause a certain degree of disturbance to the soil samples.To study the impact of exploration soil sampling techniques on the quality of soil sam ples in soft soil layers,taking the soft soil layers in Shanghai as an example,three drilling techniques,namely,threaded drill, three-wing drill and core tube,were combined with two soil sampling techniques,namely,conventional thick-walled soil sampler and galvanized iron sheet soil sample tube,and the invisible shaft valve soil sampler and the bow-shaped single slit interlocking soil sample tube,respectively,for soil sampling comparison tests.Through the comparative analysis of the appearance of soil samples,unconfined compressive strength index and disturbance index,the influence of different exploration soil sampling tech niques on the quality of soil samples was analyzed.The study results show that the influence of soil sampling techniques on the quality of soil samples is greater than that of drilling techniques.Among the drilling techniques,the soil sampling quality of the threaded drill drilling technique is the best,followed by the three-wing drill,and the core tube is the worst.The quality of soil samples obtained by the soil sampling technique combining the invisible shaft valve soil sampler and the bow-shaped single slit interlocking soil sample tube is better than that of the combination of the conventional thick-walled soil sampler and the galva nized iron sheet soil sample tube.The average unconfined compressive strength of soil samples taken by the threaded drill drill ing technique is about 15% higher than that of the three-wing drill and about 21% higher than that of the core tube.Using the change rate of void ratio under self-weight stress as a quantitative index of soil sample disturbance,the average change rate of void ratio of soil samples obtained by the worst exploration soil sampling technique is 30.8% higher than that of the best.The study reflects that choosing the optimal exploration soil sampling technique can significantly improve the quality of soil samples in soft soil layers,which is of great significance for obtaining more accurate geotechnical parameter data and improving the quality of urban and mine geological exploration.

Key words: urban geology,mining geology,drilling technique,sampling technique,quality of sampling,soil sample dis turbance