A two-dimensional similar material simulation test device and test method

Abstract

The present invention provides a two-dimensional similar material simulation test device and test method, which relates to the field of similar material simulation test, and adopts the scheme of: comprising a base, support beams are arranged on both sides of the base, a cross beam is arranged between the two support beams, a Z-direction pressure component is arranged on the cross beam, a front baffle and a rear baffle are arranged between the two support beams, a cavity for filling simulation material is arranged between the front baffle and the rear baffle, and the front baffle and the rear baffle are both made of transparent materials, and also comprises a heating car, a heating component is arranged on the heating car, and the heating component can gasify the simulation material of the mining area in the model. The present invention can realize the Y-direction constraint of the model, avoid the collapse caused by the instability of the overlying simulation material, and is suitable for the mining simulation of multi-coal seam coal mines and multi-interruption metal mines.

Description

Technical Field

[0001] The invention relates to the field of similar material simulation test, and in particular to a two-dimensional similar material simulation test device and a test method. Background Art

[0002] Similar material simulation tests can comprehensively consider the structure of underground projects and the mechanical state of rock masses. By matching different materials in reasonable proportions, a corresponding reduced-scale model of geological conditions can be scientifically constructed according to the actual geological conditions of the mine and the testing needs of the research object. Then, excavation or coal mining can be carried out in an orderly manner according to the research steps, and the movement, deformation and damage of the overlying coal (rock) layers can be observed. Combined with the existing theoretical basis, the mechanism of occurrence of on-site problems can be deduced, thereby providing important support criteria for safe and efficient mining of mines and the smooth implementation of geotechnical engineering.

[0003] In the prior art, the front and rear baffles of the two-dimensional similar simulation test model both use a grooved steel plate with a length of 300 cm and a height of 14 cm. The construction process of the two-dimensional similar simulation test model follows the installation order from bottom to top. Specifically, after the lowest baffle is installed, the modeling material simulated by the similar material is filled in the space between the baffles according to the design. After repeated compaction, the baffle at a higher position is installed again, and then the similar simulation modeling material is filled in. The cycle is repeated until all the model materials are filled in and compacted; then the model is dried to allow the similar simulation modeling material inside to have sufficient strength. When the model is dried to the extent that it can be excavated, in order to facilitate the observation of the dynamic situation of surface movement deformation and crack development of the simulated material, all the front and rear baffles need to be removed before excavation simulation.

[0004] By adopting the above technical scheme, for simulating large-scale mining conditions, such as multi-coal seam coal mines and multi-interruption metal mines, it is necessary to simulate excavation in multiple coal seams or multiple interruptions. However, since the baffles are removed during excavation, the entire model loses Y-axis constraints, and the overlying similar simulation materials are unstable, and the overall collapse of similar simulation materials is prone to occur, causing the test to fail. Even if it does not fail, the test results are inaccurate for simulating excavation of multiple coal seams or multiple interruptions. Summary of the invention

[0005] In order to solve the technical problem of inaccurate simulation of large-scale mining of multi-coal seam coal mines and multi-interruption metal mines by the two-dimensional similar material simulation test device in the above-mentioned prior art, the present invention provides a two-dimensional similar material simulation test device and test method, which can realize Y-direction constraint on the model to avoid collapse caused by instability of the overlying simulation material, and is suitable for mining simulation of multi-coal seam coal mines and multi-interruption metal mines.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is: a two-dimensional similar material simulation test device, including a base, support beams are arranged on both sides of the base, a cross beam is arranged between the two support beams, a Z-direction pressure component is arranged on the cross beam, a front baffle and a rear baffle are arranged between the two support beams, a cavity for filling simulation material is arranged between the front baffle and the rear baffle, the front baffle and the rear baffle are both made of transparent material, and also includes a heating vehicle, a heating component is arranged on the heating vehicle, and the heating component can vaporize the simulation material in the mining area in the model.

[0007] The present invention sets the front baffle and the rear baffle to be transparent, and simulates the mining of the mining area by heating. It is possible to increase the Y-direction constraint on the model without removing the baffles, avoid collapse caused by instability of the overlying simulated material, and improve the accuracy of mining simulation in multi-coal seam coal mines and multi-interruption metal mines.

[0008] Furthermore, the front baffle and the rear baffle are both segmented structures, and the front baffle and the rear baffle are both detachably connected to the support beam.

[0009] Furthermore, the heating vehicle includes a vehicle body, and the heating assembly includes a heating element 1, a telescopic arm and a heating element 2, wherein the heating element 1 is arranged on the top of the vehicle body, the telescopic arm is rotatably arranged on both sides of the vehicle body, and the heating element 2 is arranged at the end of the telescopic arm.

[0010] The present invention can achieve more comprehensive heating of the mining area through the cooperation of the heating element 1, the heating element 2 and the telescopic arm, more accurately simulate the excavation process, and improve the simulation accuracy.

[0011] Furthermore, it also includes a drying component, which is in a U-shaped structure and is laid along the two support beams and the base.

[0012] The present invention can accelerate the drying speed of the model and improve the test efficiency by arranging the drying component.

[0013] In a second aspect, the present invention further provides a two-dimensional similar material simulation test method, using the above-mentioned two-dimensional similar material simulation test device, comprising the following steps:

[0014] S01: Experimental model design to determine the mining area of ​​the excavation layer;

[0015] S02: Fill the cavity with similar materials required for the test model, bury sensors at set positions simultaneously, place a heating car in the set mining area in the cavity and fill the outside of the heating car with foam plastic to support the mining area. The uniaxial compressive strength and elastic modulus of the foam plastic should be comparable to those of other simulation materials of the excavation layer;

[0016] S03: Continue to fill the area around the mining area with similar materials required for the test model. After filling, dry it;

[0017] S04: When the similar material model is dried to the designed strength, a set pressure is applied through the Z-direction pressure component;

[0018] S05: Melt the foam plastic to simulate the excavation process, and control the heating vehicle to move along the set excavation direction to collect data;

[0019] S06: Data processing and analysis.

[0020] The present invention sets foam plastic and a heating vehicle in the mining area, thereby realizing excavation of the mining area by removing simulation materials by heating without removing the baffle, realizing Y-direction constraint on the model, and the foam plastic is discharged from the model after gasification without affecting the excavation simulation, thereby improving the accuracy of the excavation simulation of multiple coal seams and multiple intermediate faults.

[0021] Further, in S02, the heating vehicle is arranged on one side of the mining area.

[0022] The present invention can ensure that mining simulation is performed according to a set mining direction by arranging the heating vehicle on one side.

[0023] Furthermore, in S05, the heating element 1 and the heating element 2 are heated simultaneously, and the extension of the telescopic arm and the movement of the vehicle body are controlled according to the space generated after the foam plastic is melted.

[0024] Furthermore, in S02 and S03, the front baffle and the rear baffle are gradually increased in height as the model is laid.

[0025] Furthermore, in S02 and S03, after each layer of the corresponding simulation material is laid, it is smoothed and rolled, each layer of the simulation material is beveled to simulate the nodes, and mica powder is laid between two adjacent layers of simulation material to simulate the layers.

[0026] Furthermore, in S02, the sensors include stress sensors, strain sensors and acoustic emission sensors for monitoring the stress, strain and state changes of the corresponding overburden layers during the simulated excavation process. In S06, an industrial camera is used to collect data through close-range photogrammetry technology for monitoring model displacement changes.

[0027] It can be seen from the above technical solutions that the present invention has the following advantages:

[0028] The invention provides a two-dimensional similar material simulation test device and a test method. By setting a front baffle and a rear baffle to be transparent and simulating the mining of a mining area by heating, the Y-direction constraint on the model can be increased without removing the baffle, so as to avoid collapse caused by instability of the overlying simulation material, and improve the accuracy of mining simulation of multi-coal seam coal mines and multi-interruption metal mines; by the cooperation of heating element one, heating element two and a telescopic arm, it is possible to achieve more comprehensive heating of the mining area, more accurately simulate the excavation process, and improve the simulation accuracy; by setting a drying component, the speed of drying the model can be accelerated, and the test efficiency can be improved; by setting foam plastic and a heating vehicle in the mining area, it is possible to achieve excavation of the mining area in the form of removing the simulation material by heating without removing the baffle, and the Y-direction constraint on the model is achieved, and the foam plastic is discharged from the model after gasification without affecting the excavation simulation, so as to improve the accuracy of excavation simulation of multiple coal seams and multiple intermediate faults; by setting the heating vehicle on one side, it can be ensured that the mining simulation is performed in the set mining direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solution of the present invention, the accompanying drawings required for use in the description will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0030] Figure 1 This is a schematic diagram of the structure of the specific embodiment of the present invention after removing the heating car Figure 1 .

[0031] Figure 2 This is a schematic diagram of the structure of the specific embodiment of the present invention after removing the heating car Figure 2 .

[0032] Figure 3 The structure of the heating vehicle in the first embodiment of the present invention is shown in FIG. Figure 1 .

[0033] Figure 4 The structure of the heating vehicle in the first embodiment of the present invention is shown in FIG. Figure 2 .

[0034] Figure 5 This is a flow chart of a second specific implementation mode of the present invention.

[0035] In the figure, 1. base; 2. support beam; 3. front baffle; 4. Z-direction pressure assembly; 5. vehicle body; 6. heating element 1; 7. telescopic arm; 8. heating element 2; 9. rear baffle; 10. drying assembly. DETAILED DESCRIPTION

[0036] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in this specific embodiment. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of them. Based on the embodiments in this patent, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this patent.

[0037] In the prior art, when conducting a two-dimensional similarity simulation test, it is necessary to remove the baffle for the convenience of observation. However, for large-scale mining conditions of multi-coal seam coal mines and multi-interruption metal mines, excavation after removing the baffle loses the Y-axis constraint on the model. On the one hand, this is inconsistent with the actual conditions of large-scale mining and affects the accuracy of the results. On the other hand, after the model loses the Y-axis constraint, when excavating the multi-coal seam coal mine model and the multi-interruption metal mine model, the overlying similar simulation material is unstable and the overall collapse of the similar simulation material is prone to occur, resulting in test failure and increasing the difficulty of the test. To solve this technical problem, in at least one specific embodiment of the present invention, the inventor creatively adopts the technical concept of not removing the baffle, and in order to accurately simulate the excavation process without removing the baffle, further adopts the method of gasifying simulation materials for excavation, thereby improving the accuracy of simulated excavation of multi-coal seam coal mines and multi-interruption mines and the test efficiency. Specific implementation method 1

[0039] like Figures 1 to 4 As shown, this specific embodiment provides a two-dimensional similar material simulation test device, including a base 1, support beams 2 are arranged on both sides of the base 1, a cross beam is arranged between the two support beams 2, a Z-direction pressure component 4 is arranged on the cross beam, a front baffle 3 and a rear baffle 9 are arranged between the two support beams 2, a cavity for filling simulation material is arranged between the front baffle 3 and the rear baffle 9, the front baffle 3 and the rear baffle 9 are both made of transparent materials, and also includes a heating vehicle, a heating component is arranged on the heating vehicle, and the heating component can gasify the simulation material of the mining area in the model; in this specific embodiment, the transparent material adopts a single piece of cesium potassium fireproof glass, which has high strength on the basis of transparency.

[0040] This specific embodiment sets the front baffle 3 and the rear baffle 9 to be transparent, and simulates the mining of the mining area by heating. It is unnecessary to remove the baffles to increase the Y-direction constraint on the model, thereby avoiding collapse caused by instability of the overlying simulated material, and improving the accuracy of mining simulation in multi-seam coal mines and multi-interruption metal mines. At the same time, by using a heating vehicle, two mining directions can be simulated, which is more flexible to use. The simulated material is gasified after heating and does not need to be collected, which simplifies the overall structure. It is not affected by the location of the mining area and can be arranged at any height.

[0041] like Figure 1 and Figure 2 As shown, in order to ensure that the model can be laid conveniently and well, in this specific embodiment, the front baffle 3 and the rear baffle 9 are both segmented structures, and the front baffle 3 and the rear baffle 9 are both detachably connected to the support beam 2 by bolts, and screw holes are provided at corresponding positions of the support beam 2.

[0042] like Figure 3 and Figure 4 As shown, in this specific embodiment, the simulation material is arranged outside the heating vehicle. In order to ensure that the simulation material in the mining area is completely removed in the form of heating, in the specific embodiment, the heating vehicle includes a vehicle body 5, and the heating assembly includes a heating element 1 6, a telescopic arm 7 and a heating element 2 8. The heating element 1 6 is arranged on the top of the vehicle body 5, and the telescopic arm 7 is rotatably arranged on both sides of the vehicle body 5. In the specific embodiment, each side of the vehicle body 5 is respectively provided with a front and a rear telescopic arm 7, and the telescopic arm 7 adopts an electric telescopic rod. The rotating shaft of the telescopic arm 7 is rotatably arranged on the vehicle body 5 through a bearing. A corresponding rotating motor is arranged in the vehicle body 5, and the rotating motor drives the corresponding telescopic arm 7 to rotate through a gear set. The rotation of multiple telescopic arms 7 is independently controlled. A heating element 2 8 is arranged at the end of the telescopic arm 7. The heating element 1 6 and the heating element 2 8 are both heated by resistance wires. The heating temperature is controllable, and the heating temperature range is 100°C~250°C; in the specific embodiment, the inside of the vehicle body 5 A mobile motor is provided, and the mobile motor drives the wheels to move through a transmission mechanism. A controller is also provided in the vehicle body 5, and the controller is electrically connected to the mobile motor, the rotating motor and the telescopic arm 7. At the same time, the control module includes a remote control module, and the operator controls the movement of the vehicle body 5 and the rotation and extension of the telescopic arm 7 through remote control; in this specific embodiment, the size of the vehicle body 5 in the Y direction is basically the same as the Y direction size of the model. After such a setting, it is only necessary to control the vehicle body 5 to move in a straight line; the stroke of the telescopic arm 7 should not be smaller than the set size of the mining area in the Z direction; compared with the prior art that uses paraffin to simulate the coal seam and heats it through a heating plate or an electrode, the paraffin is affected by the heating conditions and will not be set too thick, otherwise it cannot be completely melted and affects the accuracy of the test simulation, but this affects the accuracy of the model establishment and is limited in use. In this specific embodiment, the telescopic arm that can be extended and rotated is driven by the vehicle body, so that comprehensive heating of the foam plastic can be achieved, and the size of the mining area can be arbitrarily set according to needs.

[0043] like Figure 1As shown, since the model must be dried to reach the set strength before excavation can be carried out, in order to increase the drying speed, in this specific embodiment, it also includes a drying component 10, and the drying component 10 is a U-shaped structure. The drying component 10 is laid along two support beams 2 and the base 1; the drying component 10 includes high-temperature resistant ceramic fiber cloth and a spiral heating wire, and the spiral heating wire can be connected to a power source. The high-temperature resistant ceramic fiber cloth is located between the model and the spiral heating wire, which can prevent the heating wire from moving and being contaminated by the simulation material.

[0044] like Figure 1 As shown, in this specific embodiment, the Z-direction pressure assembly 4 includes a plurality of hydraulic cylinders arranged in a line. Specific implementation method 2

[0046] like Figure 5 As shown, this specific embodiment provides a two-dimensional similar material simulation test method, using the two-dimensional similar material simulation test device of specific embodiment 1, including the following steps:

[0047] S01: Experimental model design to determine the mining area of ​​the excavation layer;

[0048] S02: Fill the cavity with similar materials required for the test model, bury sensors at set positions simultaneously, place a heating car in the set mining area in the cavity and fill the outside of the heating car with foam plastic to support the mining area. The uniaxial compressive strength and elastic modulus of the foam plastic should be comparable to those of other simulation materials of the excavation layer;

[0049] S03: Continue to fill the area around the mining area with similar materials required for the test model. After filling, dry it;

[0050] S04: When the similar material model is dried to the designed strength, a set pressure is applied through the Z-direction pressure applying component 4;

[0051] S05: Melt the foam plastic to simulate the excavation process, and control the heating vehicle to move along the set excavation direction to collect data;

[0052] S06: Data processing and analysis.

[0053] This specific implementation manner sets up foam plastic and a heating vehicle in the mining area, thereby realizing excavation of the mining area by heating to remove the simulation material without removing the baffle, realizing Y-axis constraint on the model, and the foam plastic is discharged from the model after gasification without affecting the excavation simulation, thereby improving the accuracy of the excavation simulation of multiple coal seams and multiple faults; in this specific implementation manner, the uniaxial compressive strength and elastic modulus of the foam plastic should be equivalent to those of other simulation materials of the excavation layer, and foam plastic with corresponding parameters can be customized from the foam plastic supplier according to the designed model. The foam plastic is gasified after heating. Compared with the prior art, which uses paraffin as the corresponding simulation material, on the one hand, it saves the trouble of collecting the metamorphosed materials and simplifies the structure; on the other hand, the gasified foam plastic penetrates into the simulation material in the upper layer, and has little effect on the simulation materials of the upper and lower layers. Compared with the use of paraffin, since the paraffin is liquid after melting, the downward Flow, if it needs to be collected, the corresponding structure needs to be set up, which will affect the simulation material of the lower layer, and then affect the accuracy of the test results. This also limits the paraffin to be set only at the bottom layer and cannot be used to simulate the upper structure. The present specific implementation method is flexible to use, and the structures located in the upper and lower layers can be simulated by foam plastics; thirdly, due to the limited hardness and strength of paraffin, the only layer structure that can be simulated is the coal seam, while foam plastics can simulate coal seams, metal ore layers and rock layers by adjusting the composition and ratio, and have a wider range of applications; fourthly, due to the prior art of simulating the mining process by melting the paraffin layer through a heating plate or an electrode, only one mining direction can be simulated, and the present specific implementation method can simulate two mining directions by setting a vehicle body, and when simulating the mining of the set mining area by melting the paraffin, the paraffin layer cannot accurately melt the corresponding volume, resulting in inaccurate boundaries of the mining area, affecting the accuracy of the simulation process.

[0054] In S02, the heating vehicle is arranged at one side of the mining area. By arranging the heating vehicle at one side, it can be ensured that the mining mode is carried out according to the set mining direction.

[0055] In S01, model design includes determining the geological mining prototype, establishing the geological mining model, determining the model scale, determining the overall size of the similar model, determining the number of layers, thickness of each layer and the inclination angle, setting the mining plan, determining the mining area, determining the type and number of sensors and their placement locations, determining the observation points and observation plans, and determining the ratio of similar materials.

[0056] In S02, sensors include stress sensors, strain sensors and acoustic emission sensors, which are used to monitor the stress, strain and state changes of the corresponding overburden layers during the simulated excavation process. In S06, industrial cameras are used to collect data through close-range photogrammetry technology for monitoring model displacement changes.

[0057] In S02 and S03, the front baffle 3 and the rear baffle 9 are gradually raised as the model is laid. After each layer of the corresponding simulation material is laid, it is leveled and rolled. Each layer of simulation material is beveled to simulate the nodes. Mica powder is laid between two connected layers of simulation material to simulate the layer.

[0058] In S03, the drying component 10 is used to heat the model to accelerate the curing process of the model.

[0059] In S04, whether the strength of the model meets the requirement is determined by a rebound tester.

[0060] In S05, the heating element 1 6 and the heating element 2 8 are heated simultaneously, and the extension of the telescopic arm 7 and the movement of the vehicle body 5 are controlled according to the space generated after the foam plastic is melted.

[0061] From the above specific implementations, it can be seen that the present invention has the following beneficial effects:

[0062] 1. By setting the front baffle 3 and the rear baffle 9 to be transparent and simulating the mining of the mining area by heating, the Y-direction constraint of the model can be increased without removing the baffle, avoiding the collapse caused by the instability of the overlying simulated material, and improving the accuracy of mining simulation in multi-coal seam coal mines and multi-interruption metal mines;

[0063] 2. Through the cooperation of the heating element 1 6, the heating element 2 8 and the telescopic arm 7, it is possible to achieve a more comprehensive heating of the mining area, more accurately simulate the excavation process, and improve the simulation accuracy;

[0064] 3. The drying component 10 can be provided to speed up the drying of the model and improve the test efficiency;

[0065] 4. By setting up foam plastics and heating vehicles in the mining area, the excavation of the mining area can be achieved by heating and removing the simulation materials without removing the baffles, realizing the Y-direction constraint of the model, and the foam plastics are discharged from the model after gasification without affecting the excavation simulation, thus improving the accuracy of the excavation simulation of multiple coal seams and multiple faults;

[0066] 5. By placing the heating vehicle on one side, it is possible to ensure that the mining simulation is carried out in accordance with the set mining direction.

[0067] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A two-dimensional similar material simulation test device, comprising a base (1), characterized in that: Support beams (2) are arranged on both sides of the base (1), a cross beam is arranged between the two support beams (2), a Z-direction pressure assembly (4) is arranged on the cross beam, a front baffle (3) and a rear baffle (9) are arranged between the two support beams (2), a cavity for filling similar materials is arranged between the front baffle (3) and the rear baffle (9), the front baffle (3) and the rear baffle (9) are both made of transparent materials, and a heating vehicle is also included, the heating vehicle is provided with a heating assembly, and the heating assembly can gasify similar materials in the mining area in the model; the heating vehicle includes a vehicle body (5), the heating assembly includes a heating element 1 (6), a telescopic arm (7) and a heating element 2 (8), the heating element 1 (6) is arranged on the top of the vehicle body (5), the telescopic arm (7) is rotatably arranged on both sides of the vehicle body (5), and the heating element 2 (8) is arranged at the end of the telescopic arm (7).

2. The two-dimensional similar material simulation test device according to claim 1, characterized in that: The front baffle (3) and the rear baffle (9) are both segmented structures, and the front baffle (3) and the rear baffle (9) are both detachably connected to the support beam (2).

3. The two-dimensional similar material simulation test device according to claim 2, characterized in that: It also comprises a drying component (10), the drying component (10) being in a U-shaped structure, and the drying component (10) being laid along the two support beams (2) and the base (1).

4. A two-dimensional similar material simulation test method, characterized in that: The two-dimensional similar material simulation test device as claimed in claim 3 comprises the following steps: S01: Experimental model design to determine the mining area of ​​the excavation layer; S02: Fill the cavity with similar materials required for the test model, bury sensors at set positions simultaneously, place a heating car in the set mining area in the cavity and fill the outside of the heating car with foam plastic to support the mining area. The uniaxial compressive strength and elastic modulus of the foam plastic should be comparable to those of other similar materials in the excavation layer; S03: Continue to fill the area around the mining area with similar materials required for the test model. After filling, dry it; S04: When the similar material model is dried to the designed strength, a set pressure is applied through the Z-direction pressure component; S05: Melt the foam plastic to simulate the excavation process, control the heating vehicle to move along the set excavation direction, and collect data at the same time; S06: Data processing and analysis.

5. The two-dimensional similar material simulation test method according to claim 4, characterized in that: In S02, the heating vehicle is arranged on one side of the mining area.

6. The two-dimensional similar material simulation test method according to claim 5, characterized in that: In S05, the first heating element and the second heating element are heated simultaneously, and the extension of the telescopic arm and the movement of the vehicle body are controlled according to the space generated after the foam plastic is melted.

7. The two-dimensional similar material simulation test method according to claim 6, characterized in that: In S02 and S03, the front baffle and the rear baffle are gradually increased as the model is laid.

8. The two-dimensional similar material simulation test method according to claim 7, characterized in that: In S02 and S03, after each layer of the corresponding similar material is laid, it is leveled and rolled, and each layer of similar material is beveled to simulate the nodes. Mica powder is laid between two adjacent layers of similar materials to simulate the layer.

9. The two-dimensional similar material simulation test method according to claim 8, characterized in that: In S02, sensors include stress sensors, strain sensors and acoustic emission sensors, which are used to monitor the stress, strain and state changes of the corresponding overburden layers during the simulated excavation process. In S05, industrial cameras are used to collect data through close-range photogrammetry technology for monitoring model displacement changes.

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