Device and method for real-time monitoring of moisture migration inside rock and soil during freeze-thaw process

Abstract

The invention discloses a device and method for real-time monitoring of moisture migration inside rock and soil during the freeze-thaw process, including a nuclear magnetic resonance system, a temperature control system and a water replenishment system. The nuclear magnetic resonance system includes a nuclear magnetic resonance host, which is placed on the nuclear magnetic resonance host The nuclear magnetic coil in the detection cabin, the nuclear magnetic coil is a cylinder with both ends open, the two ends of the nuclear magnetic coil are all provided with detachable end caps, the inner wall of the nuclear magnetic coil is provided with an insulating layer, the The interior of the insulation layer is provided with a sample chamber, and the temperature control system includes a computer, a data acquisition module, a cooler and a temperature controller. The number of the coolers is two, and the two coolers are symmetrically installed on the nuclear magnetic coil Inside the end caps at both ends. Using the device and method of the present invention to detect the distribution of water phases in different regions of the rock and soil body in real time during the freezing and thawing process can realize real-time and accurate measurement of the unfrozen water content at any cross-section inside the sample without destroying the structure of the rock and soil sample.

Description

technical field [0001] The invention belongs to the technical field of research on moisture migration inside rock and soil, and in particular relates to a device and method for real-time monitoring of moisture migration inside rock and soil during freezing and thawing. Background technique [0002] With the in-depth implementation of the national "Land Silk Road New Economic Belt" strategy and the "Western Development" strategy, large-scale infrastructure construction will be carried out in western China in the next few decades. Most of the above-mentioned areas are in seasonal (perennial) freeze-thaw areas such as plateaus and mountains, and the freeze-thaw effect is strong. The damage and deterioration of rock and soil mass under the action of freeze-thaw will cause a series of engineering geological problems. There are two main mechanisms that cause freeze-thaw damage to rock and soil: one is the volume expansion mechanism during in-situ freezing of pore (crack) water; t...

AI Technical Summary

Problems solved by technology

Most of the existing schemes adopt the design of constant positive temperature at one end and constant positive temperature at the other end, which cannot effectively simulate the natural freeze-thaw environment

For example, the patent application number 201510299172.8 discloses a device for tracking the moisture migration process in frozen soil and its experimental method. It adopts a temperature control scheme with a constant negative temperature at the upper end and a constant positive temperature at the lower end, which cannot study the interior of the soil in a natural freeze-thaw environment. Moisture migration; the patent application No. 201110185451.3 discloses a device for measuring the temperature and resistivity distribution of the phase transition process in the frozen soil test. Negative temperature to create a constant temperature gradient

[0005] (2) Moisture migration in rock and soil cannot be measured in real time and accurately

The second scheme deploys moisture sensors at different positions of the soil to measure the changes in water content at the measuring points during the freeze-thaw process. Although this method can obtain real-time data, it is limited to the number of sensors, and the measurement of the moisture distribution is also rough. In addition, the accuracy of the sensor itself is easily disturbed by factors such as temperature and humidity, and the internal test error is relatively large in the frozen state or in soil with low water content

For example, the patent application No. 201520663814.3 discloses a simulation test system for moisture migration in frozen soil under indoor snowfall conditions. The system uses multi-layer humidity sensors to monitor moisture migration. The square grid is evenly laid out, and the two adjacent floors are laid out at equal intervals of 0.5m. There is a problem that the distance between sensors is too large

The third scheme adopts the tracer method. The soil sample is placed in a transparent container, and the camera is used with a specific tracer method to monitor the migration of water. Although this method can visually observe the migration process of water, there is a problem Poor effect and other problems, and only the water migration on the surface of the sample can be observed, the results are not representative

[0006] (3) The sensor itself will cause serious disturbance to the sample structure

The sensor and the connecting wire itself occupy a certain space. Due to the limited size of the indoor test sample, especially for small samples, the presence of the sensor will significantly change the structure of the sample; in addition, the sensor is generally made of metal with good thermal conductivity. , it is easy to form anomalies in the temperature field and moisture field at the placement point, resulting in errors in test results

[0007] (4) There is no special equipment at home and abroad to monitor the water migration inside the rock during the freeze-thaw process

Existing monitoring methods are difficult to achieve high-precision monitoring without destroying the overall structure of the rock

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