阅读说明：本技术 一种高速公路下伏燃烧煤层的模型试验装置及试验方法 (Model test device and test method for burning coal bed under highway ) 是由 包卫星 王海波 来弘鹏 赵子峰 马志伟 于 2020-12-23 设计创作，主要内容包括：本发明公开了一种高速公路下伏燃烧煤层的模型试验装置及试验方法,该装置通过在模型箱内放置承载有岩土体和路基的模型,岩土体内装载有型煤模型,型煤模型内填充有加热管和热电偶,进行下伏燃烧煤层在受热情况下的沉降模拟。本发明的试验装置通过相似材料的选取,合理模拟出与路基、煤层及其影响岩层最大程度的相似,对路基填筑的施工过程,煤层燃烧的发展过程进行模拟试验,并在试验过程中布设位移监测仪器对煤层燃烧发展过程中的路基的位移进行监测,进而对实际工程中的路基稳定性进行评价分析,以采取合理的应对措施。(The invention discloses a model test device and a test method for an underlying burning coal bed of a highway. The test device reasonably simulates the similarity with the roadbed, the coal bed and the rock stratum which influence the rock stratum to the maximum extent through the selection of similar materials, carries out simulation test on the construction process of roadbed filling and the development process of coal bed combustion, and arranges a displacement monitoring instrument to monitor the displacement of the roadbed in the coal bed combustion development process in the test process, thereby carrying out evaluation and analysis on the roadbed stability in the actual engineering so as to take reasonable countermeasures.)

1. A model test device for a burning coal bed under a highway is characterized by comprising a model box (14), wherein the model box (14) is of a frame structure, and front and rear panels of the model box (14) are transparent plates;

the rock-soil mass (5) is loaded in the model box (14), the upper part of the rock-soil mass (5) is covered with a roadbed (11), and the transverse section of the roadbed (11) is trapezoidal; the inside of the rock-soil body (5), the inside of the roadbed (11) and the contact surface of the rock-soil body (5) and the roadbed (11) are provided with colored sand layers (7); the colored sand layer (7) is parallel to the ground; a briquette model (6) is arranged inside the rock-soil body (5); a cavity (3) is arranged on the front panel or the rear panel of the model box (14) at the position of the molded coal model (6);

a plurality of dial indicators (8) are inserted into the upper portion of the roadbed (11), a miniature electric heating pipe (9) and a thermocouple temperature measuring instrument (10) are inserted into the molded coal model (6), and the miniature electric heating pipe (9) and the thermocouple temperature measuring instrument (10) penetrate through the cavity (3).

2. The model test device of the expressway underburden combustion coal seam according to claim 1, wherein the colored sand layer (7) inside the rock-soil body (5) is above the molded coal model (6).

3. The model test device for the combustion coal bed under the highway according to claim 1, wherein the frame of the model box (14) is made of section steel, clamping grooves (15) are formed in two side edges of the model box (14), and the movable plate (1) is placed in the clamping grooves (15).

4. A model test device for a burning coal seam under a highway according to claim 1, characterized in that the dial indicators (8) are arranged in groups along the length direction of the roadbed (11), the dial indicators (8) are symmetrical with respect to a first central plane of the model box (14), the first central plane is perpendicular to the length direction of the model box (14), the first central plane is in the middle of the length, and the first central plane is provided with a group of the dial indicators (8);

each group of dial indicators (8) comprises 5 dial indicators (8), one dial indicator is arranged on the center line of the length of the roadbed (11), two kerbs (11-1) of the roadbed (11) are respectively provided with one dial indicator, and two slopes (11-2) of the roadbed (11) are respectively provided with one dial indicator.

5. A model test device for an underlying burning coal seam of a highway according to claim 4, characterized in that the dial indicators (8) on the two slopes (11-2) are located on a plane on which the colored sand layer (7) is arranged.

6. The model test device for the burning coal seam under the expressway according to claim 1, wherein the micro electric heating pipe (9) is arranged at the center of the briquette model (6), and the micro electric heating pipe (9) is vertical to the front panel of the model box (14).

7. The model test device for the burning coal bed under the expressway according to claim 1, wherein a plurality of thermocouple thermometers (10) are inserted into the briquette model (6), and the thermocouple thermometers (10) are equally distributed along the length direction and the width direction of the briquette model (6).

8. A model test method of a highway underlying burning coal bed based on the device of any one of claims 1-7, characterized by comprising the following steps:

step 1, determining a similarity ratio according to the elastic modulus, cohesion and friction of roadbed, stratum and coal in a research area and the size of a model box (14);

step 2, determining the composition and the proportion of the materials of the roadbed (11) and the rock-soil body (5) in the model box (14) according to the roadbed and the stratum materials and the similarity ratio of the research area, and preparing the materials of the roadbed (11) and the rock-soil body (5); pressing the briquette model (6) in a die of the pressing briquette model (6);

step 3, filling soil from the bottom of the model box (14) to a calibrated height, laying a colored sand layer (7) while filling the soil, and packaging two side edges of the model box (14) at the same time; placing a molded coal model (6) at a set position, inserting a micro electric heating pipe (9) and a thermocouple thermodetector (10) into the molded coal model (6) through the cavity (3), completing the preparation of a rock-soil body (5) after filling, and paving a colored sand layer (7); after the rock-soil body (5) is solidified and settled, filling a roadbed (11) to a calibrated height, paving a colored sand layer (7) in the middle process, after the roadbed (11) is solidified and settled, installing a dial indicator (8) on the upper part of a model box (14), inserting the dial indicator (8) into the roadbed (11), and completing the preparation of the whole test model;

step 4, heating the briquette model (6) through a micro electric heating pipe (9), recording the positions of the various colored sand layers (7) through a dial indicator (8), and observing the positions of the colored sand layers (7) through a photographic system; the corresponding relation between the settlement displacement of the surface of the roadbed (11) and the length direction of the model box (14) and the relation between the settlement displacement of the surface of the roadbed (11) and the heating temperature are obtained.

9. The apparatus for testing a model of a burning coal seam under a highway according to claim 1, wherein in step 2, the size of the mold of the pressed coal model (6) is determined according to the geometric dimension, inclination angle, thickness and similar ratio of the actual coal seam strike obtained from geological survey.

10. The model test device for the burning coal bed under the expressway of claim 1, wherein in the step 3, the roadbed (11) is settled and consolidated after the roadbed (11) is filled and left for 10 days.

[ technical field ] A method for producing a semiconductor device

The invention belongs to the technical field of road engineering, and particularly relates to a model test device and a test method for a burning coal bed under a highway.

[ background of the invention ]

Coal field fire is a disaster phenomenon widely occurring in coal mining production areas worldwide, and although the coal field fire can occur naturally under natural conditions, the occurrence of the coal field fire is more extensive and frequent in recent times along with the increase of human coal mining activities. Because of the limit of coal mining technology, part of the coal models can not be mined and are left underground in the coal mining process, and the cracks generated in the stratum when the mine tunnel or the ore body excavated in the mining process enable oxygen to permeate into the underground and contact with the unexplored float coal, so that the possibility of spontaneous combustion of the coal bed in the goaf and the abandoned coal mine is greatly improved compared with the common unexplored coal bed.

Cavities can be formed after underground coal is burnt, and the physical and mechanical properties of surrounding rock strata can be degraded by a large amount of heat released in the burning process, so that the ground is sunk, and the safe use of ground infrastructure is damaged. When the highway route has to cross the mined-out area due to difficult avoidance (too high cost for route change or difficult line type meeting requirements and the like), the highway route can pass through a roadbed or a bridge. Because the collapse pit always forms on the ground after coal mining, the mining pit also forms on the ground during open-pit mining, and the road bed is compared with the bridge, can play the effect of covering ground isolated air to ground, reduces the possibility of later stage coal seam spontaneous combustion, therefore still often need adopt the road bed form of high fill road bed to pass through when strideing across the collecting space area.

The filling amount of the high fill subgrade is large, the self weight of the high fill subgrade is easy to cause the lower foundation to generate settlement deformation, and the road surface still has traffic load after traffic is passed, so the bearing capacity and the stability of the subgrade and the lower foundation are very important problems in the high fill subgrade. The structural stability of the coal field fire zone is influenced by the stress field and the temperature field. The softening temperature of the coal is 300-550 ℃, the characteristic enables the coal to generate toughness deformation in a lower stress field and temperature field, and the coal is easier to deform and has larger deformation amount compared with silicate foundation coal under the same temperature and stress conditions. Therefore, when a high-fill roadbed is constructed in a coal mine area with a risk of spontaneous combustion, the stability of the roadbed is very easily influenced by the combustion condition of a lower coal seam.

Research methods related to evaluation and analysis of stability of roadbeds of urgent highways across special geological terrain areas can be basically divided into three categories: firstly, an actual measurement method is carried out on the earth surface of an engineering site or the interior of a rock mass below the earth surface by using various instruments and equipment; a computer numerical simulation research method is carried out indoors; and thirdly, a physical model test research method carried out indoors. For the first kind of actual measurement method, large-scale on-site actual measurement requires a lot of manpower and material resources and a long time, and various adverse conditions on-site also bring many difficulties to on-site actual measurement. For the second type of simulation method, the basic parameters such as the material constitutive and the model boundary are too ideal, the difference from the actual situation is too large, and the reliability of the obtained calculation result is not high. Physical model tests conducted indoors are therefore a major research trend.

[ summary of the invention ]

The invention aims to overcome the defects of the prior art and provides a model test device and a test method for a burning coal bed under a highway so as to solve the technical problems of the defects of an actual measurement method and a numerical simulation method in the prior art.

In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:

a model test device for a burning coal bed under a highway comprises a model box, wherein the model box is of a frame structure, and front and rear panels of the model box are made of transparent plates;

the model box is internally loaded with rock-soil bodies, the upper parts of the rock-soil bodies are covered with a roadbed, and the transverse cross section of the roadbed is trapezoidal; colored sand layers are arranged in the rock-soil body and the roadbed and on the contact surface of the rock-soil body and the roadbed; the color sand layer is parallel to the ground; a briquette model is arranged inside the rock-soil body; a cavity is arranged on the front panel or the rear panel of the model box at the position of the molded coal model;

and a plurality of dial indicators are inserted at the upper part of the roadbed, a miniature electric heating pipe and a thermocouple temperature measuring instrument are inserted in the molded coal model, and the miniature electric heating pipe and the thermocouple temperature measuring instrument penetrate through the cavity.

The invention is further improved in that:

preferably, the color sand layer in the rock-soil body is arranged above the molded coal model.

Preferably, the frame of the model box is made of profile steel, clamping grooves are formed in two side edges of the model box, and movable plates are placed in the clamping grooves.

Preferably, the dial indicators are arranged in groups along the length direction of the roadbed, the dial indicators are symmetrical relative to a first central plane of the model box, the first central plane is perpendicular to the length direction of the model box, the first central plane is in the middle of the length, and the first central plane is provided with a group of dial indicators;

each group of dial indicators comprises 5 dial indicators, one is arranged on the center line of the length of the roadbed, one is arranged on each of two curb edges of the roadbed, and one is arranged on each of two slopes of the roadbed.

Preferably, the dial indicators on the two slopes are located on a plane, and the plane is provided with a colored sand layer.

Preferably, the micro electric heating pipe is arranged at the center of the molded coal model, and the micro electric heating pipe is vertical to the front panel of the model box.

Preferably, a plurality of thermocouple thermometers are inserted into the briquette model and are distributed equally along the length direction and the width direction of the briquette model.

A model test method of a highway underlying burning coal bed based on the device comprises the following steps:

step 1, determining a similarity ratio according to the elastic modulus, cohesion and friction of roadbed, stratum and coal in a research area and the size of a model box;

step 2, determining the composition and the proportion of the materials of the roadbed and the rock-soil body in the model box according to the roadbed and the stratum materials and the similarity ratio of the research area, and preparing the materials of the roadbed and the rock-soil body; pressing the briquette model in a mould for pressing the briquette model;

step 3, filling soil from the bottom part layer of the model box to a calibrated height, laying a colored sand layer while filling the soil, and packaging two side edges of the model box; placing the molded coal model at a set position, inserting a micro electric heating pipe and a thermocouple thermodetector into the molded coal model through a cavity, completing the preparation of a rock-soil body after filling, and paving a colored sand layer; after the rock-soil mass is solidified and settled, filling the roadbed to a calibrated height, paving a colored sand layer in the middle process, after the roadbed is solidified and settled, mounting a dial indicator on the upper part of the model box, inserting the dial indicator into the roadbed, and completing the preparation of the whole test model;

step 4, heating the briquette model through a micro electric heating pipe, recording the positions of the various colored sand layers through a dial indicator, and observing the positions of the colored sand layers through a photographic system; and obtaining the corresponding relation between the settlement displacement of the roadbed surface and the length direction of the model box and the relation between the settlement displacement of the roadbed surface and the heating temperature.

Preferably, in step 2, the size of the mould of the pressed briquette model is determined according to the geometric dimension, the inclination angle, the thickness and the similar ratio of the actual coal seam trend obtained by geological survey.

Preferably, in step 3, the subgrade is left for 10 days after the subgrade is filled, so that the subgrade is settled and consolidated.

Compared with the prior art, the invention has the following beneficial effects:

the invention discloses a model test device for an underlying burning coal bed of a highway, which carries out settlement simulation of the underlying burning coal bed under the heating condition by placing a model carrying a rock-soil body and a roadbed in a model box, wherein a molded coal model is loaded in the rock-soil body, and a heating pipe and a thermocouple are filled in the molded coal model. The test device reasonably simulates the similarity with the roadbed, the coal bed and the rock stratum which influence the rock stratum to the maximum extent through the selection of similar materials, carries out simulation test on the construction process of roadbed filling and the development process of coal bed combustion, and arranges a displacement monitoring instrument to monitor the displacement of the roadbed in the coal bed combustion development process in the test process, thereby carrying out evaluation and analysis on the roadbed stability in the actual engineering so as to take reasonable countermeasures. The device simulates and predicts the deformation and displacement conditions of the road surface, the roadbed structure and the lower stratum when the highway crosses the coal field fire zone through an indoor model test, and has very important social and economic significance for subsequent safety condition assessment work, roadbed structure design, determination of fire prevention and extinguishing schemes of the coal field fire zone, reduction of construction engineering cost, improvement of the construction quality of the coal field fire zone highway, guarantee of safe operation of the highway and the like.

Furthermore, the overall sedimentation condition can be observed through the colored sand layer above the molded coal model; the model frame is made of high-strength section steel, and the front side and the rear side of the model box are sealed by toughened glass, so that the model box can bear larger pressure and can carry out a large-scale model test; the clamping grooves are formed in the opening parts on the left side and the right side of the model box, the movable plate with the length slightly smaller than the width of the model box is adopted, the wood plates are added at any time along with the increase of the filling height to plug the openings on the two sides in time, and similar materials can be filled upwards very conveniently.

Furthermore, the dial indicators which are uniformly distributed can accurately measure the settlement condition of the surface of the roadbed.

Furthermore, the electric heating pipe is arranged at the center of the briquette model and can uniformly heat the whole briquette model, and the uniformly distributed thermocouple thermometers can accurately measure the temperature change in the briquette model. In order to save the test cost and achieve the test purpose, the model of the electric heating pipe is selected according to the temperature grade to be simulated, so that the maximum heating temperature of the electric heating pipe is slightly higher than the target temperature.

The invention also discloses a model test method of the burning coal bed under the highway, which comprises a design step, a manufacturing step, a filling step and a measuring step, wherein the design step is used for designing rock mass and roadbed components in the whole model according to the actual condition of a research area, and the manufacturing process is used for manufacturing each material and filling for measurement; in the process, the miniature electric heating pipe is used for heating the molded coal model through the electric heating pipe, so that the temperature rise speed and the temperature are conveniently controlled, open fire is avoided, and the test process is safer; in the whole process, the displacement deformation of the roadbed and the lower stratum of the burning coal bed under the highway is monitored by observing the position of the colored sand layer, and the deformation condition of the stratum can be very visually observed through the transparent toughened glass.

The area is very little compared with the region that only receives high temperature influence part in the part that actual coal seam actually takes place to burn, and the deformation in stratum mainly is that coal seam and rock mass receive high temperature to influence and produce, and the model test is through similar than the coal body scope of reducing the back actual burning littleer, and most still only receives high temperature to influence, does not take place to burn. The location where the heating rod is placed is similar to the location where combustion occurs in reality, and most surrounding rocks around the heating rod are affected only by high temperature. Therefore, the coal body is heated by the power supply, so that the actual combustion phenomenon of the underground coal bed can be well simulated, and the influence of the combustion of the underground coal bed on the surrounding stratum and the ground structure is researched by the method.

The similar materials of the coal seam are manufactured by crushing and re-compacting raw coal, so that the test error caused by the change of coal components is avoided.

[ description of the drawings ]

FIG. 1 is a schematic three-dimensional structure of a mold box frame;

FIG. 2 is an overall front view of the test model;

FIG. 3 is a cross-sectional side view of the entire center of the test model;

FIG. 4 is a diagram of a rock-soil mass and coal seam simulation system;

FIG. 5 is an overall experimental flow chart;

FIG. 6 is a displacement of the road surface longitudinally along the route;

FIG. 7 is the displacement of a road surface measuring point along with the temperature change;

wherein: 1-a movable plate; 2-bottom steel plate; 3-cavities; 4-a steel beam; 5-a rock-soil mass; 6-forming a coal model; 7-color sand layer; 8-dial indicator; 9-a miniature electric heating tube; 10-thermocouple thermodetector; 11-a roadbed; 12-a first formation; 13-a second formation; 14-a mold box; 15-a card slot; 11-1-curb; 11-2-slope.

[ detailed description ] embodiments

The invention is described in further detail below with reference to the accompanying drawings:

in the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention; the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance; furthermore, unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly and encompass, for example, both fixed and removable connections; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Referring to fig. 1, the invention discloses a model test device for a burning coal bed under a highway, the main body of the device is that a model box 14 is in a cuboid shape, the geometric dimension of the model box 14 can be determined according to the stratum condition to be simulated and the selected similarity ratio, the frame of the model box 14 is formed by connecting profile steels according to the actual conditions in a welding or bolt hinging mode, the strength is very high, and the model box can bear larger stress, the steel beam 4 on the frame not only ensures the integral stability of the model box, but also can be used for installing and fixing a magnetic gauge stand of a dial indicator 8, and the bottom of the model box 14 is provided with a bottom steel plate 2. The front side surface and the rear side surface of the model box 14 are sealed by adopting transparent organic toughened glass, the thickness of the organic toughened glass is preferably 12mm, and the transparent organic toughened glass is used for sealing so as to assist in monitoring the displacement of the stratum and the roadbed and facilitate the visual observation of the displacement deformation condition of the stratum in the model box 14; clamping grooves are formed in the opening portions on the left side and the right side of the model box 14, the movable plate 1 with the length slightly smaller than the width of the model box is adopted, and wood plates are added at any time along with the increase of the filling height to timely plug the opening portions on the two sides so as to fill similar materials upwards. Clamping grooves 15 are formed in the opening positions of the left side and the right side of the model box in an aligned mode along the length direction of the model box, the clamping grooves 15 are used for loading the movable plate 1, the length of the movable plate 1 is slightly smaller than the width of the model box 14, and the movable plate 1 is increased at any time along with the increase of the filling height in the model box 14 so as to plug the openings of the two sides in time and fill similar materials upwards; a semicircular cavity 3 is cut in toughened glass in front of or behind the molded coal model 6, so that a miniature electric heating pipe 9 and a thermocouple temperature measuring instrument 10 can be inserted into the molded coal in a pre-embedded mode conveniently, a connecting line of the thermocouple temperature measuring instrument 10 can enter and exit conveniently, the bottom of the model box 14 is sealed by a steel plate, and the upper portion of the model box is not sealed.

The whole simulation system is arranged in the model box 14 and comprises a rock-soil body and coal bed simulation system, wherein the rock-soil body 5, the briquette model 6 and the roadbed 11; a coal bed heating and temperature control monitoring system comprises a micro electric heating pipe 9 and a thermocouple temperature measuring instrument 10; and the roadbed displacement monitoring system comprises a colored sand layer 7 and a dial indicator 8. The arrangement relationship of the systems is shown in fig. 2, wherein: hs is the roadbed thickness, and in order to simulate the situation of an actual stratum, a first stratum 12 and a second stratum 13 are provided, wherein h1 is the thickness of the first stratum 12, h2 is the thickness of the second stratum 13, and hc is the coal seam height. This system includes rock and soil body 5, first stratum 12, second stratum 13 and roadbed soil 11 that from the bottom up stacked gradually, wherein between first stratum 12 and second stratum 13, between second stratum and the roadbed 11, the inside of roadbed 11 all is provided with various sand layer 7, various sand layer 7 is on a parallel with ground. The upper part of the inside of the rock-soil body 5 is provided with a roadbed 11, the upper surface of the roadbed 11 is in contact with the lower surface of the first ground layer 12, the roadbed 11 is a parallelepiped, and the cross-sectional area of the roadbed 11 in the vertical direction is trapezoidal, so that the roadbed 11 has a structure that the horizontal area gradually decreases from bottom to top.

The positions and the number of the dial indicators 8 and the color sand layers 7 can be changed and increased or decreased according to actual needs.

Rock-soil mass and coal bed simulation system

This test device comes the simulation underground coal seam through the moulded coal model 6 of burying broken repression in ground body 5, later heats it through pre-buried miniature electric heating pipe 9 in moulded coal model 6 inside again, and then simulates the process that the coal seam is heated and softens. The shape of the coal bed model is adjusted to conveniently adjust the occurrence parameters of the coal bed, such as strike, dip angle, thickness and the like, and the intensity of the coal bed can be adjusted by adjusting the pressing time and the additional load during the re-pressing so as to achieve the aim of similarity of coal bed materials. The rock-soil body 5 and the roadbed 11 similar materials are prepared by using fine sand and clay as basic raw materials, and the rock-soil body similar materials with different strengths and meeting the requirements of similar ratio can be prepared by changing the proportion of the fine sand and the clay, the amount of water used in mixing and the like.

Coal bed heating and temperature control monitoring system

The heating of the briquette model 6 is mainly realized by a micro electric heating pipe 9 embedded in the briquette model, and the temperature in the heating process is monitored by a thermocouple temperature measuring instrument 10 also embedded in the briquette model 6. According to the temperature measured by the thermocouple thermometer 10, the heating rate and the heating temperature can be accurately and quickly controlled by adjusting the heating power of the micro electric heating pipe 9. The built-in micro electric heating pipe 9 is adopted to heat the molded coal model 6, so that the generation of open fire can be avoided, and the test process is carried out safely. The volumes of the micro electric heating pipe 9 and the thermocouple temperature measuring instrument 10 are small relative to the overall size of the briquette, so that the mechanical properties of the coal bed are not greatly influenced.

Roadbed displacement monitoring system

The dial indicator 8 is a displacement measuring instrument with high measuring precision, convenient installation and reading, economy and practicability, so the test mainly measures the surface displacement of the road surface and the roadbed through the dial indicator 8, and simultaneously carries out auxiliary observation on the overall displacement of the roadbed 11 and the rock-soil body 5 by utilizing the color sand layer 7 embedded in the roadbed 11 and the rock-soil body 5, and the displacement of the color sand layer 7 is recorded by adopting a digital photographic system.

Similar model test process of the burning coal bed under the highway:

the general process of the similar model test of the highway underlying burning coal bed is shown in figure 5, and the specific test process comprises the following steps:

1. the influence of the coal seam crossed by the highway route on the roadbed stability is preliminarily analyzed through on-site geological survey so as to determine the longitudinal L of the road section to be researched₀Transverse direction W₀Depth H of lower stratum of roadbed₀The scope of investigation of (1).

2. After the research range is defined, the rock and coal bed of roadbed and roadbed lower portion stratum are drilled and sampled on site, and then the elastic modulus E of roadbed, stratum and coal can be obtained by means of related field test or indoor test₀C cohesion₀Angle of friction phi₀Coefficient of thermal conductivity K0, specific heat capacity C₀Coefficient of thermal expansion γ basic material parameters.

3. The similarity ratio of the model test is determined according to the size of the model box 14, the circled research range and the similarity theory, and the similarity ratio is the most basic and most important parameter in the model test.

4. And (3) preparing a sufficient number of similar materials of the roadbed 11 and the rock-soil mass 5 meeting the test requirements according to the on-site rock-soil mass 5 and roadbed 11 material parameters obtained in the step (2) and the similarity ratio determined in the step (3). The similar materials of the roadbed 11 and the rock-soil mass 5 are prepared by taking quartz sand and clay as basic raw materials, and the similar materials with different material parameters are prepared by changing the proportion of the quartz sand and the clay, the mixing amount of water, adding vaseline and the like in the preparation process, wherein the material parameters are determined based on the material parameters and the similarity ratio of the actual stratum.

5. The raw coal is crushed, mixed with water, placed in a mould to be compacted again for forming, and the briquette models 6 with different similar specific strengths can be prepared by adopting different compaction loads and compaction times. The following points should be noted during the pressing process of the briquette:

a) and the size of the die for pressing the briquette model is determined according to the geometric dimension, the inclination angle, the thickness and the similarity ratio of the actual coal seam trend obtained by geological survey. The geometric dimension, the dip angle and the thickness of the actual coal seam trend are all actual dimensions, and the dimension of the die is the ratio of the actual dimension to the similarity ratio.

b) Because the structure of the briquette is easy to damage after the briquette is pressed and formed, holes for installing the micro electric heating pipe 9 and the thermocouple temperature measuring instrument 10 are reserved in the process of pressing the briquette, and the reserved holes can be realized by inserting wood sticks or reinforcing steel bars with the same size as the micro electric heating pipe 9 and the thermocouple temperature measuring instrument 10 at corresponding positions.

c) Because the composition of different types of coal has large difference, the difference of physical and mechanical properties is also large in the heating process. To reduce this difference, the briquette should be made of the same type of coal as the coal in the field, for example, if the coal layer at the lower part of the roadbed in the field is anthracite, the anthracite should be used as the raw coal for making the briquette model 6. Under the condition that the conditions allow, the raw coal collected from the field is used as much as possible to manufacture the molded coal.

6. Mold box 14 is filled. Determining the size of a model box 14 before filling, wherein the size of the model box 14 is L, H and W of the model box determined according to the actually cut cuboid stratum size divided by the similarity ratio, and the filling of the model box 14 mainly comprises the following steps:

a) filling soil from the bottom surface of the model box 14 to the preset coal seam bottom surface elevation in a test layer by layer, and gradually inserting the movable plate 1 into the clamping grooves on the two sides of the model box along with the increase of the soil filling height;

b) after the pressed molded coal is placed at a preset position, a micro electric heating tube 9 and a thermocouple thermodetector 10 are inserted into a pre-reserved molded coal hole, and a molded coal model 6 is determined according to the actual stratum condition; wherein the micro electric heating pipe 9 is arranged at the central part of the whole molded coal model 6, and the thermocouple thermodetector 10 is set according to the requirement, and the basic requirement is that the micro electric heating pipe is equally arranged in the transverse direction and the vertical direction in the molded coal model 6.

c) Continuously filling common rock-soil mass upwards until the ground, tamping and leveling by using a tamping hammer, and standing for 30 days to finish consolidation and settlement of the stratum;

filling the roadbed 11 to the road surface elevation in a layered manner;

d) after the roadbed 11 is filled, standing for 10 days to enable the roadbed 11 to be settled and consolidated;

e) the embedding of the colored sand layer 7 is completed in the process of filling the lower stratum and the roadbed 11, and the thickness of the colored sand layer 7 is 4-5 mm.

7. A square steel pipe is placed at the top of the model box 14 to ensure stability and no movement. Then, firmly adsorbing the magnetic gauge stand on the upper square steel pipe, and erecting and screwing the dial indicator 8 on the magnetic gauge stand according to a preset position; the distribution mode of the preset installation positions of the dial indicator 8 is as follows: the upper surface of the roadbed 11 is used as the center and is expanded and distributed transversely and longitudinally; referring to fig. 3, a row of dial indicators 8 in the transverse direction of the roadbed 11 is set as a group, in each group, a dial indicator 8 is arranged at the center point of the roadbed 11, two curbs 11-1 are respectively provided with one dial indicator 8, slopes 11-2 at two sides are respectively provided with one dial indicator 8, and the five dial indicators 8 are arranged on a transverse section; along the longitudinal direction of the roadbed 11, each group of dial indicators 8 are arranged, the arranged dial indicators 8 are symmetrical relative to the cross section of the center of the model box 14, but the distances between the adjacent dial indicators 8 are not required to be equal, as can be seen from fig. 2 and 4, the distances from the molded coal models 6 are unequal, and the deformation degrees are different, so that the design criterion of the dial indicators 8 is that the farther the distance between the dial indicators 8 and the molded coal models 6 is, the larger the arrangement distance between the adjacent dial indicators 8 is; in the above structure, the number of the dial indicators 8 in each group or the number of the arrays in each group can be adjusted according to actual conditions.

Five displacement measuring lines are arranged at the middle point of the top surface of the roadbed along the longitudinal direction of the route, two side kerbs 11-1 and slopes 11-2, dial indicators 8 are erected above the defined measuring line positions according to the preset positions, and each dial indicator 8 can measure the displacement of one point. After the dial indicator 8 is installed, recording an initial reading, and simultaneously recording the position of the colored sand by adopting a digital photography system;

8. the briquette model is heated by connecting a power supply to simulate the combustion heating process of the briquette model 6, the mechanical property change of coal is greatly influenced due to the temperature rise speed, the temperature rise speed in the briquette model 6 is controlled in the heating process, and the heating process is controlled in real time according to the temperature measured by the thermocouple thermometer 10;

9. after the power supply is switched on and heating is started, recording the reading of the dial indicator 8 and the temperature of the thermocouple thermometer 10 according to a specific time interval, and observing the position of the colored sand by adopting a digital photography system;

10. the test results are analyzed, sorted and analyzed, the relationship between the longitudinal pavement displacement change along the route in fig. 6 and the change of the displacement of a certain point of the pavement along with the temperature of the lower coal seam in fig. 7 can be obtained, and the displacement of the roadbed in the actual engineering can be reversely deduced according to the displacement measured in the test, so that the stability and the settlement deformation of the actual roadbed can be analyzed and predicted.

The design mechanism of the invention is as follows:

after the underground coal seam is burnt, various influences can be generated on the physical and mechanical properties of the upper stratum and the surrounding rocks, and further influences on the stability of a building built on the upper part of the burning coal seam in different degrees. The influence mechanism is very complex, the evaluation and analysis of the influence mechanism are difficult to carry out through simple theoretical analysis, a plurality of research means are required to carry out comprehensive research, and an indoor model test is one of the efficient and accurate research methods. According to the invention, similar materials with specific proportioning parameters are filled in the model box to simulate stratum surrounding rocks and road matrixes, raw coal is crushed and heavily compacted to prepare briquette blocks which are buried in the model box soil to simulate a coal bed, and the briquette model is subjected to a combustion heating process of heating to simulate the coal bed through a miniature electric heating pipe. The displacement of the roadbed is monitored by mounting the dial indicator on the cross beam at the upper part of the model box, and the multilayer colored sand is spread in the rock stratum at the upper part of the coal bed and the roadbed to carry out auxiliary observation on the deformation and the displacement of the stratum and the roadbed, so that the method has very important social and economic significance for subsequent safety condition assessment work, roadbed structure design, fire prevention and extinguishing scheme determination, construction engineering cost reduction, highway construction quality improvement in coal mine areas, highway safety operation guarantee and the like.

Compared with the field actual measurement research method, the model test method can simulate the contrast test under different working conditions, solves the problems of irreversible field actual measurement and unchangeable influence factors, and solves the problem of high cost of field actual measurement. The deformation movement law of the overlying strata and the highway subgrade in the coal field fire area can be deeply researched. And because higher requirements are made on the similar materials of the model and the manufacture of the model, the accuracy of the test data is ensured, single factors can be changed under the condition of simulating other influencing factors without changing, and the influence of each influencing factor on the overlying strata of the underground coal seam fire area and the highway subgrade is reflected.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.