Active optical fiber temperature change-based in-situ testing method for unsaturated soil permeability coefficient

Abstract

The invention provides an in-situ testing method for an unsaturated soil permeability coefficient by combining an active optical fiber temperature change-based in-situ distributed measurement method for water content with a soil water characteristic curve on the basis of a traditional transient profiling method. Long-distance and rea-time distributed measurement of soil mass volume water content can be achieved, and calculation of the unsaturated soil permeability coefficient is achieved on the basis of a measured profile of the volume water content, so that the shortcoming that a volume watercontent distribution function needs to be assumed on the basis of a water content point measurement result or the volume water content is indirectly calculated through the soil water characteristic curve in the prior art is overcome; and the calculation accuracy of the unsaturated permeability coefficient is improved.

Description

Technical field [0001] The invention belongs to the technical field of research on the permeability coefficient of unsaturated soil in geotechnical engineering and geological engineering, and specifically relates to a method for testing the permeability coefficient of unsaturated soil based on optical fiber active temperature change. Background technique [0002] Unsaturated soil is composed of three phases: solid, liquid and gas. Due to the existence of matrix suction, the permeability of unsaturated soil is a function of the change of water content. Permeability coefficient is one of the important parameters of the theory of unsaturated flow movement, which is of great significance for engineering construction and geological disaster prevention in areas with deep groundwater buried. [0003] The measurement of the permeability coefficient of unsaturated soil is a difficult point in the study of unsaturated soil. At present, there are mainly two methods: indirect method and direct...

AI Technical Summary

Problems solved by technology

[0007] In the traditional temperature measurement system, it is necessary to increase the spatial resolution of the test (generally m level) by laying out the temperature measurement optical cable in a spiral shape. However, with the advancement of distributed temperature sensing and demodulation technology, the highest spatial resolution has reached cm level, so it is no longer necessary

At present, the bottleneck of this technology is mainly that the active heating method of the optical cable has problems such as too long heating time, uneven heating along the length, and great interference to the soil moisture field, which makes it difficult to implement on-site and the test error is too large, which hinders the project. Field application of technology

Images