CN114487012B - Soil body surface crack development pre-judging method - Google Patents
Soil body surface crack development pre-judging method Download PDFInfo
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Abstract
The invention discloses a soil body surface crack development pre-judging method, and belongs to the field of infrared remote sensing-geological engineering. It comprises the following steps: s1, shooting the surface of a soil body to be monitored by adopting an infrared thermal imaging camera to obtain a soil body surface temperature field; s2, drawing a soil isothermal map according to a soil surface temperature field; and S3, determining a main crack development area on the soil surface according to the soil isothermal line graph. According to the invention, the surface temperature field change in the soil body cracking process is analyzed through the real-time acquired soil surface temperature field information, so that the crack development of the soil body surface is predicted, the crack development of the soil body surface can be effectively and rapidly monitored, and the soil body crack development prediction method is a simple and efficient soil body crack development prediction method.
Description
Technical Field
The invention belongs to the field of infrared remote sensing-geological engineering, and particularly relates to a soil body surface crack development pre-judging method.
Background
All objects with surface temperatures above absolute zero (-273.15 ℃) will continuously radiate electromagnetic waves to the outside. When the surface temperature of the object changes, the radiation intensity and the wavelength distribution characteristics of the electromagnetic wave also change. Electromagnetic waves having a wavelength of 2.0 μm to 1000 μm are called thermal infrared rays. The penetration of thermal infrared rays into most solid and liquid substances is extremely poor, so that the object only shows surface radiation to external thermal infrared radiation. When the thermal infrared rays are transmitted in the atmosphere, the thermal infrared rays are absorbed by substances consisting of the atmosphere, the strength is obviously reduced, and the thermal infrared rays have better penetration rates only in two wave bands of 3 mu to 5 mu and 8 mu to 12 mu. The infrared imaging device can realize inversion of the surface temperature field of the target object by capturing the thermal infrared rays of the two wave bands to perform instant calculation. By utilizing the characteristic, the infrared thermal imaging camera captures thermal infrared rays of the two characteristic wave bands radiated by the soil sample, and calculates and inverts the temperature field distribution of the soil sample surface according to the radiation intensity of the thermal infrared rays. The technology is effective and convenient, is a nondestructive monitoring mode, is firstly applied to forest fire prevention and electric fault detection, is then popularized and applied to stress fields and crack monitoring of rocks and concrete, is mainly limited to measuring the water content and the heat conductivity coefficient in soil, and is relatively late in monitoring and starting about soil surface cracks.
Under the action of drought climate, the natural soil can crack due to water loss and shrinkage, and develop a fracture network with transverse cross clusters on the surface. The generation of cracks damages the integrity of the soil body, and provides a convenient channel for the migration of moisture in the soil body, thereby causing various problems. The solution to this problem must be initiated by rapid monitoring of the soil fracture network. At present, the monitoring mode of soil body cracks is mainly divided into two modes: contact, non-contact. The contact fracture monitoring method comprises methods such as an optical fiber sensing technology (BOTDR), a high-density resistivity imaging technology (ERT) and the like, and optical fibers, probes or sensors are needed to be embedded in a soil body before the method is used, so that the soil body structure is damaged to a certain extent, the cracking process of the soil body is affected, and the soil body can cause deformation of an embedded object in the drying shrinkage process to cause inaccuracy of a monitoring result. The existing non-contact method such as digital image correlation technology (DIC) observes the change of the surface strain/displacement field in the dry shrinkage cracking process of the soil body, the nondestructive monitoring mode ensures the accuracy of in-situ monitoring of the soil body, and only the development direction of the crack can be deduced in advance, but the method has short prediction time in advance and is difficult to popularize in engineering application.
The prior art with publication number CN108398368A discloses a device and a method for extracting soil surface crack pores, the method limits the size and the placement position of a soil sample, an opaque studio is arranged outside a soil sample placement table, and a photographic device photographs and records through an opening at the top of the studio. The application of the technology is limited to indoor tests, and the technology is not related to crack monitoring under the in-situ state of the soil body. In addition, the technology only monitors and records the crack development condition of the soil body, but the development of the soil body cracks is closely related to the factors such as the environmental temperature, the moisture field in the soil body and the like, and the technology does not monitor and record the factors affecting the development of the soil body surface cracks.
The prior art with publication number CN109470595A discloses a soil body testing method with synchronous automatic weighing and crack photographing. According to the method, the photographing and weighing time is controlled to automatically photograph and weigh, so that the crack evolution condition and the water content change rule of the soil body can be accurately recorded, the disturbance to the pattern is small, and the method is convenient to use. But the method is only suitable for monitoring the surface cracks of the small-scale soil in a laboratory, and the monitoring of the water field of the soil in the evaporation process is only stopped on the water content of the whole soil.
The prior art with the publication number of CN103983514A discloses an infrared radiation monitoring test method for the crack development of coal and rock, which is suitable for researching the crack development monitoring generated in the deformation of coal and rock of mines, and the related cracking object is coal and rock. The prior art with the publication number of CN109696354A discloses an infrared radiation monitoring device and method in the fracture rock mass destruction evolution process. The infrared heat radiation difference in the monitoring process of the technology is derived from heat energy generated by deformation movement, while the infrared heat radiation difference in the soil mass crack development process is derived from evaporation of water in the soil mass. The engineering properties of rock and soil are obviously different, and the reasons for cracking are also different, so that the technology cannot be suitable for monitoring the fracture network of the soil.
In summary, aiming at the problem of dry shrinkage cracking of the soil body in nature, how to seek a more effective, more convenient and more accurate nondestructive technical means to realize the prejudgment of the development of the soil body surface cracks, so as to better know the mechanism of the dry shrinkage cracking of the soil body and know the area and the direction of the development of the soil body surface cracks in advance, is a problem to be solved urgently at present, and has positive significance for mechanism analysis in scientific research and disaster prevention and reduction in engineering.
Disclosure of Invention
1. Problems to be solved
In the prior art, although the soil surface fracture network can be rapidly monitored, most of the methods need to destroy the original structure of the soil, and are time-consuming and labor-consuming and influence the monitoring accuracy. Aiming at the problem that nondestructive prediction of the development of the soil surface cracks is difficult to realize in the prior art, the invention provides the soil surface crack development prediction method, which can more effectively, conveniently and accurately predict cracks under the condition of not disturbing the soil so as to predict the initiation and evolution of the soil cracks.
2. Technical proposal
In order to solve the problems, the technical scheme adopted by the invention is as follows:
a soil body surface crack development pre-judging method comprises the following steps:
s1, shooting the surface of a soil body to be monitored by adopting an infrared thermal imaging camera to obtain a soil body surface temperature field;
s2, drawing a soil isothermal map according to a soil surface temperature field;
and S3, determining a main crack development area on the soil surface according to the soil isothermal line graph.
Preferably, the method for determining the main fracture development area of the soil surface in the step S3 comprises the following steps:
s3-1, determining a low-temperature core area according to a soil isothermal diagram; the junction of the adjacent low-temperature core areas is a soil body surface main crack development area; and/or
S3-2, a soil body surface main crack development area along the isotherm direction.
Preferably, the low-temperature core region refers to a region in which the temperature of the isotherm decreases from outside to inside. The temperature of the low-temperature core area is obviously lower than the average temperature of other areas on the surface of the soil body.
Preferably, the average temperature of the low-temperature core area is greater than 1.5 ℃ with the temperature difference at the highest temperature of the soil body (the specific difference is determined according to the ambient temperature).
Preferably, the junction of the adjacent low-temperature core areas in the step S3-1 refers to the junction surrounding the isothermal lines of the two adjacent low-temperature core areas in the soil isothermal line map. For example, two adjacent low-temperature core areas form an 8-shaped area, and the junction of the adjacent low-temperature core areas is a connecting line of the 8-shaped concave parts.
It should be noted that the main fissure is defined as a fissure in which the development point in the soil mass does not start from other fissures.
Preferably, the main fissure of the soil surface in the step S3-1 develops along the direction of the boundary line of the junction of the adjacent low-temperature core areas.
At the junction between adjacent low temperature core regions, a main fracture develops and extends along the boundary line of the adjacent low temperature core regions. The reason for the phenomenon is that the temperature at the junction of the low-temperature core areas is higher, the temperatures at the two sides of the junction are low, soil bodies on the junction move towards the low-temperature core areas at the two sides continuously, as soil particles in different areas move oppositely, local soil bodies are in a tension state, tensile stress is continuously accumulated, and when the tensile stress exceeds the tensile strength of the soil bodies at the corresponding positions, cracks are generated at the junction.
Preferably, after step S3, further comprising:
s4, determining secondary cracks: a secondary fracture is created perpendicular to the primary fracture, the secondary fracture being a fracture created from a location in the primary fracture.
Preferably, the step S4 is performed to develop the crack in the direction of the isotherm.
Preferably, the soil surface main crack development region along the isotherm direction in the step S3-2 includes an edge of the low-temperature core region, and the edge of the low-temperature core region refers to an outermost isotherm region of the low-temperature core region.
At the edge of the low temperature core zone is a soil surface dominant crack development zone along the isotherm direction due to the large evaporation/shrinkage rate gradient at the edge of the low temperature core zone. From the earth surface temperature field, the temperature at the edge of the low-temperature core area is not completely consistent, the temperature gradually decreases from the edge to the core, and a temperature gradient exists. The temperature gradient indicates that there may be a gradient in evaporation/shrinkage rate perpendicular to the isotherm, i.e. a portion of the soil body shrinks fast (near the low temperature core region because of the fast evaporation) and another portion of the soil body shrinks slowly (near the temperature boundary region because of the slow evaporation). The fast shrinking soil mass is limited by the slow shrinking soil mass during the deformation process, so that the tensile stress concentration is caused, and the main tensile stress direction is also orthogonal to the isotherm direction, so that main cracks on the soil surface along the isotherm direction are generated.
The invention discloses a soil body surface crack development pre-judging method, which comprises the following steps:
(1) Determining the range of the monitored soil body, pasting a black 3M adhesive tape on the periphery of the soil body, erecting an infrared thermal imaging camera and a single-lens reflex camera (used for verifying the accuracy of the pre-judging method) and connecting a computer;
(2) Calibrating the ambient temperature;
(3) Inputting soil emissivity parameters, calibrating environmental temperature and relative humidity in software research IR, setting shooting interval time of an infrared thermal imaging camera and a single phase inverter, and starting automatic shooting;
(4) Monitoring the development condition of soil surface cracks in real time:
s1, shooting the surface of a soil body to be monitored by adopting an infrared thermal imaging camera to obtain a soil body surface temperature field;
s2, drawing a soil isothermal map according to a soil surface temperature field;
s3, determining a main crack development area of the soil surface according to the soil isothermal line map:
s3-1, determining a low-temperature core area according to a soil isothermal diagram; the junction of the adjacent low-temperature core areas is a soil body surface main crack development area; the low-temperature core region refers to a region with temperature decreasing from outside to inside of the isotherm; the junction of the adjacent low-temperature core areas is the junction surrounding the isothermal lines of the two adjacent low-temperature core areas in the soil isothermal line diagram; the main fissure of the soil surface develops along the direction of the boundary line of the junction of the adjacent low-temperature core areas; and/or
S3-2, a soil body surface main crack development area along the isotherm direction;
s4, determining secondary cracks: a secondary fracture is created perpendicular to the primary fracture. The secondary fissures tend to develop in the direction of the isotherm after production.
It should be noted that, the conditions of the steps S3-1 and S3-2 may exist at the same time, or only one of the conditions may exist, and when the soil surface has an adjacent low-temperature core area, the soil surface must have a main crack obtained by the S3-1 prejudging method; when the soil body surface does not have an adjacent low-temperature core area, if only an isolated low-temperature core area exists, the soil body surface does not have a main crack obtained by the S3-1 pre-judging method, but has a main crack obtained by the S3-2 pre-judging method; in either or both of the above-described primary fissures, the secondary fissures develop from a location on the primary fissure.
The soil body surface main crack development area along the isotherm direction of S3-2 comprises the edge of the low-temperature core area, the edge of the low-temperature core area refers to the outermost isotherm area of the low-temperature core area, and the soil body surface main crack along the isotherm direction of S3-2 is more easily generated in the area.
And when the monitoring result of the infrared thermal imaging camera is adopted to predict the development of the soil body surface crack, the single phase camera is adopted to shoot an image to verify the crack development process.
3. Advantageous effects
Compared with the prior art, the invention has the beneficial effects that:
(1) The method aims at the problem that the development condition of the surface fissure of the soil body needs to be prejudged in the original structure of the soil body in the existing monitoring means of the in-situ soil body cracking process, the surface temperature field of the early soil body evaporation stage obtained by infrared thermal imaging is adopted, the development starting position and the extension direction of the surface fissure of the soil body are prejudged in a nondestructive mode according to the temperature field distribution, the method can be used for successfully prejudging the development area and the development trend of the fissure for 48 hours at most before the fissure is formed, the soil body structural damage caused by the arrangement of monitoring facilities in the prior art is avoided, and the prediction time is greatly advanced compared with other fissure monitoring modes (such as ERT (resistivity tomography), DIC (digital image correlation technique) and the like), and the development dynamic trend of the surface fissure can be obtained earlier.
(2) The existing non-contact fracture monitoring means such as digital image correlation technology (DIC) and the like can only simply record the surface strain/displacement field of the soil body on the assumption that the soil body is an homogeneous mass with uniform water content of each point, but the initial position of the fracture can be estimated in advance, but the prediction time is short in advance, the influence of evaporation difference on each position of the soil body surface cannot be considered, and the water content difference of each point cannot be analyzed; the invention can record the temperature change of each point on the soil surface by utilizing the infrared thermal imaging technology to obtain the temperature field difference of each point, further predict the soil surface crack development according to the temperature field difference, and can predict the soil surface crack development up to 48 hours in advance.
(3) The device is simple, convenient to operate, accurate in monitoring result, free of limitation of environmental conditions in application range, and suitable for undisturbed soil body crack development monitoring in indoor tests and in situ sites.
Drawings
FIG. 1 is a schematic view of the apparatus of the present invention;
FIGS. 2 (a) -2 (f) are isothermal line graphs of the soil mass of the monitoring zone in example 1;
fig. 3 (a) -3 (f) are soil surface crack development diagrams at different moments photographed by a single lens reflex camera in example 1;
FIGS. 4 (a) and 4 (b) are an infrared imaging chart and a single-lens reflex camera image of the sample in example 2;
FIGS. 5 (a) -5 (d) are isotherm plots and single fracture predictions 48 hours prior to the creation of the first fracture in example 3;
fig. 6 (a) -6 (c) are isotherm plots and crack predictions 48 hours before the first crack in example 3 was generated.
In the figure: 1. a computer; 2. an infrared thermal imaging camera; 3. a temperature/humidity meter; 4. a single-lens reflex camera; 5. black 3M tape; 6. monitoring soil mass in a region; 7-11, and a crack.
Detailed Description
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs; the term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
The black 3M adhesive tape used in the invention is manufactured by 3M company in the United states, the model is 1500 black, and the emissivity parameter is 0.95; the infrared imager is FLIR-T620, the resolution of the camera is 640 multiplied by 480pix, the temperature measurement sensitivity is +/-0.04 ℃, and the precision is +/-0.1 ℃.
As shown in fig. 1, the erected infrared thermal imaging camera should be located right above the monitoring area and adjusted to be fixed at a proper height, so as to ensure that the soil mass and the black 3M adhesive tape of the monitoring area fill the viewfinder to the greatest extent. The single-lens reflex camera is erected above the monitoring area and is adjusted to be fixed at a proper height, so that the soil body of the monitoring area is ensured to fill the view finding frame.
The method for calibrating the ambient temperature comprises the following steps:
a) Measuring the ambient temperature by a thermometer;
b) Inputting a black 3M adhesive tape emissivity parameter and an ambient temperature into software research IR;
c) Measuring the temperature of the covered area of the black 3M adhesive tape by using an infrared thermal imaging camera;
d) Comparing the temperature of the adhesive tape in the step c) with the ambient temperature input in the step b), and ending the calibration if the temperature is consistent with the ambient temperature; and if the temperature of the black 3M adhesive tape is inconsistent with the temperature of the black 3M adhesive tape, changing the ambient temperature input in the step b), and repeating the step c) until the temperature of the black 3M adhesive tape is consistent with the ambient temperature.
For most types of soil, the thermal infrared emissivity of the surface of the soil is between 0.90 and 0.95. In the case of an undefined soil body specific thermal infrared emissivity, the average value of 0.925 is generally taken as the soil sample emissivity parameter.
The automatic photographing function of the infrared thermal imaging camera is realized by software research IR, the set photographing interval time is determined according to the cracking speed of the soil body, and 10 minutes is generally taken as the photographing interval time. The body thermal infrared radiation temperature field image is directly obtained by software research IR. The soil body thermal infrared radiation temperature data at each moment is directly led out by software research IR, and the soil body isothermal line diagram of the monitoring area at each moment is drawn by software Surfer 16.
The automatic photographing interval time of the single lens reflex is consistent with the automatic photographing time of the infrared thermal imaging camera.
The soil surface crack development pre-judging method comprises the following steps:
s1, shooting the surface of a soil body to be monitored by adopting an infrared thermal imaging camera to obtain a soil body surface temperature field;
s2, drawing a soil isothermal map according to a soil surface temperature field;
s3, determining a main crack development area of the soil surface according to the soil isothermal line map:
s3-1, determining a low-temperature core area according to a soil isothermal diagram; the junction of the adjacent low-temperature core areas is a soil body surface main crack development area;
the low-temperature core region refers to a region with the temperature of the isotherm decreasing from outside to inside; the junction of two adjacent low-temperature core areas is the junction surrounding the isothermal lines of the two adjacent low-temperature core areas in the soil isothermal line diagram; the main fissure of the soil surface develops along the direction of the boundary line of the junction of the adjacent low-temperature core areas; and/or
S3-2, a soil body surface main crack development area along the isotherm direction;
s4, determining secondary cracks: secondary fissures are created perpendicular to the primary fissures, which tend to develop along the isotherm after creation.
The soil body cracks are generally generated along the isothermal line at the junction of the adjacent low-temperature core areas or at the edge of the low-temperature core areas, the soil body cracks corresponding to the isothermal line at the junction of the adjacent low-temperature core areas or at the edge of the low-temperature core areas are high in extending speed, and the development degree of the cracks is high; and the soil body in the high temperature area has low crack extension speed and low crack development degree, but the crack width is expanded quickly and the whole shrinkage degree of the soil body is high. The high temperature region herein refers to a region where the isotherm decreases in temperature from the inside to the outside.
The parameters of the single lens reflex monitoring fracture are obtained by analyzing and processing photos by CIAS software which is independently developed by Nanjing university.
The invention is further described below in connection with specific embodiments.
Example 1
The soil body of the embodiment is an initial saturated soil sample of the lower holly soil, the sieved dry soil sample of the lower holly soil is mixed with distilled water, the mixture is fully stirred to prepare a saturated soil sample with the water content of 170%, and the saturated soil sample is vibrated on a vibrating table for 5min so as to eliminate bubbles generated in the slurry in the stirring process. The slurry was then sealed in a container and allowed to stand for 48h. After the slurry deposition was stabilized, the surface clear liquid was drawn out, and the water content was measured to be about 70%. The prepared slurry was poured uniformly into a 20X 20cm plexiglass box having a height of 4cm. The inner wall of the container, including the side plate and the bottom plate, is coated with vaseline for lubrication treatment, so that the influence of friction of the side wall of the container and the bottom plate on shrinkage cracking of soil body is reduced as much as possible. The prepared sample was dried in a room at a constant temperature of 31 ℃. Two fans are respectively placed at the left and right sides of the organic glass box to blow air to the soil surface, so that the temperature field distribution difference of the soil surface is caused.
(1) The container boundary edge shrinkage zone may be mistaken for a soil crack in the analysis, resulting in inaccurate monitoring results. In order to reduce the influence of the edge shrinkage area on crack prediction, only a part 18cm of the center of the sample is selected for monitoring, and a black 3M adhesive tape is stuck to the periphery of the soil body. An infrared thermal imaging camera is erected, and a camera view finding frame is filled with a monitoring area soil body and a black 3M adhesive tape.
(2) The calibrated ambient temperature is 31.0 ℃ according to the method of (one) calibrating the ambient temperature.
(3) Taking down the soil body of the hollyhock, wherein the emissivity parameter is 0.925, the calibrated environment temperature is 31.0 ℃, the relative humidity is 70% measured by a hygrometer, inputting software research IR, setting the photographing interval time to be 10 minutes, and starting to monitor the development condition of the surface cracks of the soil body.
(4) Monitoring the development condition of soil surface cracks in real time:
s1, shooting the surface of a soil body to be monitored by adopting an infrared thermal imaging camera, and monitoring the change condition of the current soil body surface temperature field in real time through software research IR to obtain a soil body surface temperature field;
s2, drawing a soil isothermal diagram according to a soil surface temperature field: obtaining a soil isothermal diagram of the monitoring area at each moment in the figures 2 (a) -2 (f) (t=15, 55, 115, 185, 265 and 305min analysis is taken);
s3, determining a main crack development area of the soil surface according to the soil isothermal line map:
and (3) predicting the development of the cracks according to the soil surface crack development predicting method.
S3-1 as shown in FIG. 2 (d) and FIG. 3 (d) at 12, a main crack develops at the boundary between the two low-temperature core regions and extends in the direction of the boundary line. The reason for the phenomenon is that the temperature at the junction of the low-temperature core areas is higher, the temperatures at the two sides of the junction are low, soil bodies on the junction move towards the low-temperature core areas at the two sides continuously, as soil particles in different areas move oppositely, local soil bodies are in a tension state, tensile stress is continuously accumulated, and when the tensile stress exceeds the tensile strength of the soil bodies at the corresponding positions, cracks are generated at the junction.
S3-2 is shown as 7-11 in FIG. 2 (b) -FIG. 2 (d) and FIG. 3 (b) -FIG. 3 (d), and as evaporation continues, a main soil surface crack along the isotherm direction is firstly generated at the edge of the low-temperature core region and extends along the isotherm of the temperature field. The reason for this is the large gradient in evaporation/shrinkage rate at the edges. From the earth surface temperature field, the temperature at the edge of the low-temperature core area is not completely consistent, the temperature gradually decreases from the edge to the core, and a temperature gradient exists. The temperature gradient indicates that there may be a gradient in evaporation/shrinkage rate perpendicular to the isotherm, i.e. a portion of the mass shrinks fast (near the core of the low temperature core region because of the fast evaporation) and another portion of the mass shrinks slowly (near the border region of the low temperature core region because of the slow evaporation). The fast shrinking soil mass is limited by the slow shrinking soil mass during the deformation process, so that the tensile stress concentration is caused, and the main tensile stress direction is also orthogonal to the isotherm direction, so that main cracks on the soil surface along the isotherm direction are generated.
In this embodiment, the S3-1 and S3-2 main cracks are present at the same time.
Experimental results: in the embodiment, the method can accurately obtain the soil surface temperature field distribution, so that the development form of soil surface cracks can be prejudged. The crack of the isothermal line graph of the soil body in the monitoring area can better correspond to the actual cracking condition of the soil body (shown in the figures 3 (a) -3 (f)).
Through verification of a single-lens reflex camera, the soil surface crack development prediction method reasonably predicts the development trend of the soil surface crack by the soil surface temperature field data of 170 minutes before the crack occurs, and has higher prediction accuracy.
Example 2
The soil conditions and related parameters of this example are the same as those of example 1, and the implementation steps are basically the same as those of example 1, except that:
vaseline is not smeared at the bottom of the organic glass box so as to achieve the effect of limiting the shrinkage of soil body (used for influencing the quantity and the width of cracks).
Experimental results: as shown in fig. 4, fig. 4 (a) is an infrared thermal imaging image, and fig. 4 (b) is a single-phase inverter image after 2 h. As shown in fig. 4 (a), according to the soil surface crack development prediction method S3-1, cracks are generated in the soil at the junction of two low-temperature core areas, the cracks are main cracks, and the cracks continuously develop along the boundary line. Its mechanism of formation is mainly due to moisture migration and soil particle movement. According to the soil surface crack development pre-judging method S4, secondary cracks are generated on the original main cracks, the crack development path of the secondary cracks is perpendicular to the original main cracks, the secondary cracks tend to develop along the isothermal line direction after the secondary cracks are generated, and the secondary cracks are a series of surface secondary cracks caused by friction.
This example is where only S3-1 primary and S4 secondary fissures are present.
The infrared thermal imaging image prejudging result can be better corresponding to the single-phase camera image.
Example 3
The kind and characteristics of the soil of this example are the same as those of example 1, and the procedure is basically the same as that of example 1, except that:
the water content of the saturated mud sample of the lower hollyhock soil during initial evaporation is 60 percent. The organic glass box container has a size of 40X 60cm and a height of 4cm. Considering the larger sample size, the sample was manually shaken for 15 minutes to remove internal air bubbles. Fans at both ends of the plexiglas box were removed and the sample evaporated naturally.
In this example, to reduce the impact of the edge shrinkage area on fracture prediction, only a 28×28cm portion of the center of the specimen was selected for monitoring.
Experimental results: FIG. 5 (a) shows the predicted path of the main crack growth at the junction of the low-temperature core region through an isothermal line graph according to S3-1 48 hours before the first crack is generated in the evaporation process, and FIG. 5 (b) shows the actual main crack (left in FIG. 5 (b)) and growth extension (right in FIG. 5 (b)) photographed through a single-phase inverter image after 48 hours; fig. 5 (c) shows the predicted path of the development of the main crack at the edge of the low-temperature core region by isothermal line drawing according to S3-2 48 hours before the first crack is generated in the evaporation process, and fig. 5 (d) shows the actual main crack (left in fig. 5 (d)) and development extension (right in fig. 5 (d)) taken by a single-phase inverter image after 48 hours. The method can be used for predicting the development extension direction of the crack in the evaporation process well by using isothermal line image energy obtained through infrared thermal imaging image data processing, and the prediction time is greatly advanced compared with other prediction modes.
FIG. 6 (a) shows an isothermal diagram 48 hours before the first fracture is generated, and according to the fracture determination methods S3-1, S3-2 and S4 of the present invention, the fracture prediction diagram shown in FIG. 6 (b) is obtained, and comparison can be seen that the actual fracture network shown in FIG. 6 (c) can be better corresponding.
The foregoing is illustrative of the present invention and embodiments thereof, and is not to be construed as limiting the invention, but rather as merely one of the embodiments thereof, as the practical construction is not limited thereto. Therefore, if one of ordinary skill in the art is informed by this disclosure, the structural mode and the embodiments similar to the technical scheme are not creatively designed without departing from the gist of the present invention.
Claims (7)
1. The soil body surface crack development pre-judging method is characterized by comprising the following steps of:
s1, shooting the surface of a soil body to be monitored by adopting an infrared thermal imaging camera to obtain a soil body surface temperature field;
s2, drawing a soil isothermal map according to a soil surface temperature field;
s3, determining a main crack development area on the surface of the soil body according to the soil body isothermal line graph;
the method for determining the main crack development area of the soil surface in the step S3 comprises the following steps:
s3-1, determining a low-temperature core area according to a soil isothermal diagram; the junction of the adjacent low-temperature core areas is a soil body surface main crack development area; and/or
S3-2, a soil body surface main crack development area along the isotherm direction; the soil body surface main crack development area along the isotherm direction comprises the edge of the low-temperature core area, and the edge of the low-temperature core area refers to the outermost isotherm area of the low-temperature core area;
the low-temperature core region refers to a region with temperature decreasing from outside to inside of the isotherm.
2. The method for predicting the surface crack development of the soil body according to claim 1, wherein the average temperature of the low-temperature core area is greater than 1.5 ℃ with the temperature difference at the highest temperature of the soil body.
3. The method according to claim 1, wherein the junction of the adjacent low-temperature core areas in step S3-1 is a junction surrounding the isothermal lines of the two adjacent low-temperature core areas in the soil isothermal line map.
4. A soil surface crack development pre-judging method according to claim 3, wherein the soil surface main crack of the step S3-1 develops along the direction of the boundary line of the junction of the adjacent low-temperature core areas.
5. The method of predicting soil surface crack development as claimed in claim 1, further comprising, after step S3:
s4, determining secondary cracks: a secondary fracture is created perpendicular to the primary fracture.
6. The method according to claim 5, wherein the fissure development tends to develop along the isotherm after the fissure is generated for the step S4.
7. The soil body surface crack development pre-judging method is characterized by comprising the following steps of:
(1) Determining the range of the monitored soil body, pasting a black 3M adhesive tape on the periphery of the soil body, erecting an infrared thermal imaging camera and connecting a computer;
(2) Calibrating the ambient temperature;
(3) Inputting soil emissivity parameters, calibrating environmental temperature and relative humidity in software research IR, setting shooting interval time of an infrared thermal imaging camera, and starting automatic shooting;
(4) Monitoring the development condition of soil surface cracks in real time:
s1, shooting the surface of a soil body to be monitored by adopting an infrared thermal imaging camera to obtain a soil body surface temperature field;
s2, drawing a soil isothermal map according to a soil surface temperature field;
s3, determining a main crack development area of the soil surface according to the soil isothermal line map:
s3-1, determining a low-temperature core area according to a soil isothermal diagram; the junction of the adjacent low-temperature core areas is a soil body surface main crack development area; the low-temperature core region refers to a region with temperature decreasing from outside to inside of the isotherm; the junction of the adjacent low-temperature core areas is the junction surrounding the isothermal lines of the two adjacent low-temperature core areas in the soil isothermal line diagram; the main fissure of the soil surface develops along the direction of the boundary line of the junction of the adjacent low-temperature core areas; and/or
S3-2, a soil body surface main crack development area along the isotherm direction comprises the edge of the low-temperature core area, and the edge of the low-temperature core area refers to the outermost isotherm area of the low-temperature core area.
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