Abstract: The present disclosure provides a method for measuring flow velocity distribution of groundwater using distributed optical fiber with active heating, comprising: setting and optimizing field test parameters; conducting a background temperature monitoring test; performing a line-source active heating distributed temperature measurement test, including conducting multiple rounds of heating tests; denoising the obtained thermal plume attenuation signal data of the groundwater; and fitting the groundwater velocity-depth curve in the borehole by monitoring and analyzing the temperature difference signal between the internal temperature and the external temperature of the composite heating optical cable in a single depth section of the borehole, thereby obtaining a distributed groundwater velocity data set.

Abstract: A method for detecting adsorption performance of microplastics for heavy metals using low-field NMR relaxation method, including: establishing a reference line reflecting a relationship between a target heavy metal ion concentration and a transverse relaxation time; conducting a heavy metal adsorption experiment on microplastics and obtaining samples at different time points; detecting transverse relaxation times of the multiple samples obtained; determining a heavy metal ion concentration of each sample based on the reference line of the target heavy metal ion concentration and the transverse relaxation time; analyzing data and implementing a model fitting process. The method according to the present disclosure does not require cumbersome and complicated sample pre-processing, it can be measured immediately after sampling, it is simple, fast and low-cost, the method has a wide detection limit, the detection is faster, non-destructive testing can be achieved.

Abstract: A method for detecting adsorption performance of microplastics for heavy metals using low-field NMR relaxation method, including: establishing a reference line reflecting a relationship between a target heavy metal ion concentration and a transverse relaxation time; conducting a heavy metal adsorption experiment on microplastics and obtaining samples at different time points; detecting transverse relaxation times of the multiple samples obtained; determining a heavy metal ion concentration of each sample based on the reference line of the target heavy metal ion concentration and the transverse relaxation time; analyzing data and implementing a model fitting process. The method according to the present disclosure does not require cumbersome and complicated sample pre-processing, it can be measured immediately after sampling, it is simple, fast and low-cost, the method has a wide detection limit, the detection is faster, non-destructive testing can be achieved.

Abstract: A clamp and a shear test device are provided, and relate to the technical field of rock mass mechanics tests. The clamp comprises a box body, wherein an opening is formed in one side of the box body, two clamping structures are oppositely arranged in the box body, a sample is arranged between the two clamping structures, each clamping structure comprises an adjusting mechanism, and a distance between the two clamping structures is adjusted through adjusting mechanisms of the two clamping structures. According to the clamp, real-time dynamic adjustment is conveniently and rapidly achieved, the stability of sample clamping is ensured, and therefore the requirement that the shear load can be truly and effectively transmitted to the sample through the box body is met.