Electric signal time-varying interpretation method in seasonal freezing and thawing environment

Abstract

The invention discloses an electric signal time-varying interpretation method in a seasonal freeze-thaw environment, and the method comprises the steps: obtaining an electric signal based on ERT equipment, and building a function relation between the resistivity and the mechanical performance of a soil body under different moisture contents and freeze-thaw cycle conditions through a numerical simulation method; and interpreting the electric signals into visual mechanical parameters for judging whether the roadbed has defects or not. According to the invention, the ERT detection devices are placed at fixed points in different areas to regularly detect the highway subgrade in the cold region, the electric signals are remotely transmitted to the host for interpretation, the effective mechanical parameters for judging the defects of the highway subgrade are obtained, and the method has the advantages that the disturbance of a measurement mode to a soil body is small, and the electric signals are interpreted into intuitive soil mechanical parameters. The method is simple in construction process, simple in structural hierarchy, suitable for field long-term fixed-point detection and free of manual data acquisition, and monitoring can be started after instruments are arranged after data such as the maximum depth are set.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of defect detection of highway subgrade in cold regions, and relates to an electrical signal time-varying interpretation method, in particular to an electrical signal time-varying interpretation method under seasonal freeze-thaw environment. BACKGROUND

[0002] In the durability research of subgrade in cold regions, freeze-thaw action is a very important factor, and the main filler of subgrade in cold regions is generally coarse-grained soil, so the frost heaving disease of highway subgrade in cold regions in winter is closely related to the mechanical properties of coarse-grained soil under freeze-thaw action. How to accurately and conveniently detect the damage of subgrade in cold regions under freeze-thaw environment is an inevitable problem in the maintenance of highway in cold regions.

[0003] Nowadays, the resistivity tomography technology is mostly used for electrode design measurement system, and has been used for dam quality detection or loess slope water infiltration in the field of civil engineering. Considering that freeze-thaw cycle has a great influence on the electromechanical properties of coarse-grained soil in high-cold regions, the electrical resistivity of coarse-grained soil increases with the increase of freeze-thaw cycle times under freeze-thaw action, and the mechanical parameters have a significant downward trend, so a mathematical model about electrical resistivity and soil mechanical properties can be established by numerical simulation method. In practical application, the collected electrical signals can be transmitted back to the host computer for data processing through the ERT detection equipment arranged, and the electrical signals are interpreted into intuitive mechanical parameters for judging whether the subgrade has defects. SUMMARY

[0004] In order to improve the deficiencies of the prior art, the application provides an electrical signal time-varying interpretation method under seasonal freeze-thaw environment. The method detects the highway subgrade in cold regions by placing ERT (Electrical Resistivity Tomography) detection equipment at different positions, remotely transmits the electrical signals to the host computer for interpretation, obtains effective mechanical parameters for judging the defects of highway subgrade, and has the advantages of small disturbance to soil body in measurement mode, electrical signal interpretation into intuitive soil mechanics parameters and the like.

[0005] The purpose of the application is realized by the following technical scheme:

[0006] An electrical signal time-varying interpretation method under seasonal freeze-thaw environment, comprising the following steps:

[0007] Step 1: The subgrade of railway in cold regions to be detected is segmented, and the original parameter setting is changed for specific places with poor environment;

[0008] Step 2: The maximum measurement depth of different measuring points is determined according to the freeze depth calculation method in the freeze-heave prevention design of subgrade of railway in cold regions;

[0009] Step three, arrange the improved ERT device, determine the number of electrodes and arrangement spacing according to the arrangement site, and then adjust the power supply voltage and current according to the electrode spacing;

[0010] Step four, establish a sensor detection system composed of temperature sensors and moisture sensors, the moisture sensor is used for measuring the dielectric constant, which directly reflects the water content of the soil p w The temperature sensor is used for calibrating the water content and resistivity, so as to introduce a mathematical model for calculation;

[0011] Step five, it is specified that N groups (N is specified according to actual conditions, and the reliability is sufficient) of data are collected for each periodic detection, and the interval between each group of data is M hours (M is specified according to actual conditions, and the reliability is sufficient), after remote data transmission, the two groups of data with the largest resistivity change are taken for analysis;

[0012] Step six, the resistivity of the soil under different water content conditions after different freeze-thaw cycles is determined in a laboratory environment p The resistivity of the soil is taken as a variable to analyze the law of the soil cohesion and the internal friction angle by Matlab software fitting, and the change cloud diagram of the resistivity, the soil cohesion value and the internal friction angle of the region under the action of the freeze-thaw cycle number and the water content is obtained;

[0013] Step seven, according to the Mohr-Coulomb strength theory, the shear stress on the shear fracture surface is taken as the shear strength value, and a mathematical model meeting the shear stress is established Wherein, alpha and beta are to be determined coefficients, and n is the freeze-thaw cycle number;

[0014] Step eight, the data obtained by the ERT device monitoring are inverted by using Res2dinv software, the resistivity profile of the highway subgrade is obtained, and the function relationship between the resistivity and the shear strength is established, so as to convert the resistivity profile into the shear strength profile;

[0015] Step nine, if the shear strength is less than the specified safety value, it is determined that there is a defect in the part, if the calculation result of step eight does not meet the safety value, the system identifies the defect part in the shear strength profile and issues a warning, otherwise, the data collection and operation are repeated according to the determined detection time.

[0016] Compared with the prior art, the present application has the following advantages:

[0017] 1. The present application can interpret the resistivity measured by the ERT device into shear strength, and establish a corresponding shear strength distribution map, so as to directly judge whether the highway subgrade has defects.

[0018] 2. The construction procedure of the present application is simple, the structure level is simple, and the instrument can be arranged after setting the maximum depth and other data, and then the monitoring can be started.

[0019] 3. This invention is suitable for long-term fixed-point detection in the field, eliminating the need for manual data collection.

[0020] 4. The detection method selected in this invention causes minimal disturbance to the soil itself, thus minimizing soil damage caused by the placement of the detection device.

[0021] 5. The detection method selected in this invention has a large penetration depth, high accuracy, and high resolution. Attached Figure Description

[0022] Figure 1 This is a flowchart of the overall method for interpreting time-varying electrical signals under seasonal freeze-thaw conditions. Detailed Implementation

[0023] The technical solution of the present invention will be further described below with reference to the accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0024] This invention provides a time-varying interpretation method for electrical signals under seasonal freeze-thaw conditions. The method acquires electrical signals using an ERT device and establishes a functional relationship between resistivity and soil mechanical properties under different moisture contents and freeze-thaw cycles using numerical simulation. The electrical signals are then interpreted into intuitive mechanical parameters for determining the presence of defects in the roadbed. Furthermore, since shear strength determines the bearing capacity of the roadbed, shear strength is selected as the interpreted mechanical parameter. Figure 1 As shown, the specific steps include the following:

[0025] Step 1: Divide the railway subgrade in the cold region to be tested into sections to differentiate the parameter settings under different conditions. For specific locations with harsh environments, change the original parameter settings.

[0026] Step 2: Based on the frost depth calculation method in the design of railway subgrade frost heave prevention in cold regions, determine the maximum measurement depth of different measuring points according to the actual situation of different measuring points in the plan.

[0027] Step 3: Deploy the improved ERT device. Determine the number of electrodes and their spacing based on the deployment location. Initially, set 80 electrodes to be connected, with a spacing of 0.8m. Adjust the power supply voltage and current according to the electrode spacing. The improved ERT device consists of a main unit, a monitoring unit, a converter, and electrodes. It uses a servo power supply. The monitoring unit is responsible for collecting data related to moisture content and resistivity, and transmitting the data to the main unit for processing to obtain a shear strength profile. Data analysis of the shear strength is used to determine whether an alarm is needed. The improved ERT device features accurate data acquisition, remote data acquisition, and convenient post-processing.

[0028] Step four, a sensor detection system is established, which is mainly composed of a temperature sensor and a moisture sensor, the moisture sensor is used for measuring the dielectric constant, and the moisture content of the soil is directly reflected p w The temperature sensor is used for calibrating the moisture content and resistivity, so as to introduce a mathematical model for calculation.

[0029] Step five, ten groups of data are collected for each periodic detection, the interval between each group of data is 3h, after remote data transmission, the two groups of data with the largest resistivity change are taken for analysis.

[0030] Step six, the resistivity of the soil under different water contents after different freeze-thaw cycles is determined in the laboratory environment p The resistivity of the soil is taken as a variable, the law of the soil cohesion and the internal friction angle is analyzed by Matlab software fitting, and the change cloud diagram of the resistivity, the soil cohesion and the internal friction angle of the region under the action of freeze-thaw cycle times and water content is obtained.

[0031] Step seven, according to the Mohr-Coulomb strength theory, the shear stress on the shear fracture surface is taken as the shear strength value, and a mathematical model satisfying the shear stress is established Wherein, alpha and beta are undetermined coefficients, and n is the freeze-thaw cycle times.

[0032] Step eight, the data obtained by the ERT device monitoring are inverted by Res2dinv software, the resistivity profile of the highway subgrade is obtained, and the function relationship between the resistivity and the shear strength is established, and the resistivity profile is converted into the shear strength profile.

[0033] Step nine, if the shear strength is less than the specified safety value, it means that there is a defect in the part, if the calculation result of step eight does not satisfy the safety value, the system identifies the defect part in the shear strength profile and sends out a warning, otherwise, the data collection and operation are repeated according to the established detection time.

[0034] In the application, the improved ERT device is used for strictly conducting cold resistance measurement, and the cold resistance element is used, so that the element failure in cold area can be avoided to cause abnormal data.

[0035] In the application, double lines are adopted in remote data transmission, so that the detection data can not be interrupted due to abnormal data transmission, and the real data can be obtained in time.

[0036] In the application, the moisture content and freeze-thaw cycle times are taken as variables in the laboratory environment, the mechanical experiment of the coarse-grained soil sample in the region is conducted, and the safety value of the shear strength is specified.

[0037] In the application, the arrangement of ERT device emission and reception (field monitoring is arranged according to 0.8 meter interval electrode, obtains the space-time distribution data of resistivity field) divides the measured soil into equidistant units, considering that the resistivity can reflect the structural characteristics of the frozen soil, combining the relationship between the resistivity and the shear strength of the coarse-grained soil under the action of freeze-thaw cycle, the collected resistivity data is reprocessed and converted into the corresponding shear strength. According to the resistivity profile, the corresponding shear strength profile can be obtained, and the part with shear strength lower than the set safety value is considered to have defects.

Claims

1. A method for interpreting time-varying electrical signals under seasonal freeze-thaw conditions, characterized in that... The method includes the following steps: Step 1: Divide the railway subgrade in the cold region to be tested into sections, and change the original parameter settings for specific locations with harsh environments; Step 2: Based on the calculation method for freezing depth in the design of railway subgrade frost heave prevention in cold regions, determine the maximum measurement depth at different measuring points; Step 3: Arrange the improved ERT device. Determine the number of electrodes and their spacing based on the location, and then adjust the power supply voltage and current according to the electrode spacing. Step 4: Establish a sensor detection system consisting of a temperature sensor and a moisture sensor. The moisture sensor is used to measure the dielectric constant, directly reflecting the soil moisture content. ρ w Temperature sensors are used to calibrate moisture content and resistivity so that they can be imported into mathematical models for calculations. Step 5: Collect N sets of data for each periodic test, with an interval of M hours between each set of data. After the data is transmitted remotely, take the two sets of data with the largest change in resistivity for analysis. Step Six: Laboratory environmental determination of soil resistivity under different moisture contents after different freeze-thaw cycles. ρ By fitting and analyzing the soil cohesion and internal friction angle with resistivity as a variable using Matlab software, cloud maps of the changes in resistivity, soil cohesion and internal friction angle in this region under the influence of freeze-thaw cycles and water content were obtained. Step 7: Based on the Mohr-Coulomb strength theory, using the shear stress on the shear failure surface as the shear strength value, establish a mathematical model that satisfies the shear stress. Where α and β are undetermined coefficients, and n is the number of freeze-thaw cycles; Step 8: Use Res2dinv software to invert the data obtained from the ERT device monitoring to obtain the roadbed resistivity profile. Combine the established functional relationship between resistivity and shear strength to convert the resistivity profile into a shear strength profile. Step 9: If the shear strength is less than the specified safety value, the part is considered to have a defect. If the calculation result of Step 8 does not meet the safety value, the system will mark the defective part in the shear strength profile and issue an early warning. Otherwise, the data acquisition and calculation will continue to repeat according to the predetermined detection time.

2. The method for interpreting time-varying electrical signals under seasonal freeze-thaw conditions according to claim 1, characterized in that... In step three, 80 electrodes are initially set up, with a spacing of 0.8m between them.

3. The method for interpreting time-varying electrical signals under seasonal freeze-thaw conditions according to claim 1, characterized in that... In step three, the improved ERT device consists of a host, a monitoring host, a converter, and electrodes. It adopts a servo power supply method. The monitoring host is responsible for collecting moisture content and resistivity, and transmitting the data to the host for processing to obtain a shear strength profile. By analyzing the shear strength data, it is determined whether an alarm is needed.

Images