CN107328917A - The simulation system and experimental method of face stability are excavated for regulating and controlling frozen soil tunnel - Google Patents

Abstract

The invention relates to the field of tunnel construction model tests, in particular to a simulation system and an experiment method for regulating and controlling the stability of tunnel excavation surfaces in frozen soil. The simulation system includes a model system, a sensing system and a processing system. The soil model box and the tunnel model. The tunnel model can be inserted into the frozen soil and pushed out, thereby exposing the excavation surface of the simulated frozen soil tunnel that communicates with the outside world. The sensing system includes measuring equipment installed in the frozen soil layer of the model box. The morphological parameters of the excavation surface of frozen soil are connected to the processing system, the data is transmitted to the processing device through the data acquisition device of the processing system, and then the processed data is output after analysis and processing. The present invention simulates the working conditions of tunnel construction in frozen soil, and The morphological parameters of the excavation surface and frozen soil are measured, and after the analysis and processing of the processing system, a conclusion is drawn, revealing the instability mechanism of the excavation surface, providing reference suggestions for engineering construction, and achieving the purpose of avoiding accidents such as tunnel collapse and roof fall .

Description

Simulation system and experimental method for controlling the stability of tunnel excavation face in permafrost

technical field

The invention relates to the field of tunnel construction model tests, in particular to a simulation system and an experimental method for regulating the stability of excavation surfaces of tunnels in frozen soil.

Background technique

Permafrost is widely distributed in my country, and its area accounts for about one-fifth of my country's land area. Building roads and tunnels in these areas is undoubtedly a challenge for engineers. During the 13th Five-Year Plan period, the country will build more expressways, high-speed railways and urban subways in the western region. Summarizing past successful experience and carrying out technological innovation has become an important task for engineers to solve urgently.

Permafrost is extremely sensitive to temperature changes. The instability of the excavation face of permafrost tunnels is mainly due to the fact that the frozen soil in front of the excavation face undergoes dual effects of heat exchange inside and outside the tunnel and construction behavior in the tunnel. There is a temperature difference between the permafrost surrounding rocks in front of the excavation face, and the heat is spontaneously transferred from the depth of the permafrost surrounding rocks in front of the excavation face to generate convective heat transfer, and a melting core is quickly formed in the permafrost surrounding rocks. The melting core is the "root of all evil" that causes the instability of the tunnel excavation surface in permafrost. Therefore, if the dynamic evolution law of the melting core and the instability mechanism of the excavation surface can be grasped, corresponding measures can be taken to avoid the occurrence of disasters such as tunnel collapse and roof fall. To provide reliable technical advice and data support for construction in permafrost areas has become an important goal in solving the construction process in permafrost areas.

In the prior art, when construction is carried out in permafrost regions, most of the projects are adapted to local conditions, and corresponding countermeasures are taken according to the actual situation encountered by the project, but a set of effective methods and countermeasures have not been formed, and some projects have limited adoption. However, this finite element analysis method is too theoretical and cannot replace the actual construction conditions of tunnel excavation faces in permafrost. It often introduces technical parameters artificially, which has little reference significance and application value. Therefore, There is an urgent need for a laboratory system equipment, which can be easily operated and can simulate the evolution process of the melting core in the process of convective heat transfer in actual engineering.

Contents of the invention

The purpose of the present invention is to aim at the inability to obtain the evolution law of the melting core and the instability mechanism of the tunnel excavation surface in advance during the construction process of frozen soil, resulting in the inability to provide reference and effective suggestions for engineering construction to regulate the stability of the excavation surface during the construction process , which leads to the inability to prevent disasters such as tunnel collapse and roof fall in advance. A simulation system and experimental method for regulating the stability of the tunnel excavation surface in permafrost are provided. The simulation system includes a model system, a sensor system and a processing system , through the model system to simulate the instability of the excavation surface of the frozen soil tunnel construction, and then rely on the sensor system to measure the excavation surface and frozen soil, obtain the shape parameters of the excavation surface, and use the processing system to analyze and process, The dynamic evolution law of the melting core and the instability mechanism of the excavation surface are revealed, so as to provide reference and effective suggestions for engineering construction to regulate the stability of the excavation surface, and effectively avoid the occurrence of disasters such as tunnel collapse and roof fall.

In order to realize the above-mentioned purpose of the invention, the present invention provides the following technical solutions:

A simulation system for regulating the stability of the tunnel excavation surface in permafrost, including a model system, a sensor system and a processing system, wherein:

The model system includes a model box and a tunnel model for containing frozen soil, and a larger hole for installing the tunnel model is opened on the model box, so that the tunnel model can be pushed out from the larger hole, and then the frozen soil can be simulated. The excavation surface of the soil communicates with the outside world;

The sensing system includes a temperature measuring instrument and a seepage pressure measuring instrument, the temperature measuring instrument and the seepage pressure measuring instrument are installed in the model box and connected with the processing system for measuring the temperature and seepage pressure of the frozen soil excavation surface;

The processing system includes a data collection device for collecting morphological parameters of the sensing system, the data collection device is connected to a processing device for storing and analyzing morphological parameters, and the processing device outputs processed data.

Permafrost is extremely sensitive to temperature changes. During tunnel excavation, the heat inside and outside the tunnel spontaneously protrudes from the permafrost surrounding rock in front of the excavation face to generate convective heat transfer, thereby forming a melting core in the permafrost surrounding rock. The root cause of the instability of the excavation surface of frozen soil tunnels is the melting core. In this scheme, after the tunnel model is pushed out/slid out from the frozen soil, the simulated frozen soil excavation surface connected to the outside world is exposed. Temperature difference, convective heat exchange, so that the inside of the permafrost begins to melt to form a melting zone, simulating the melting core generated during the construction process in the permafrost area, and measuring the shape of the permafrost through the sensor system installed in the permafrost (including temperature , seepage pressure, etc.), relying on the analysis of the processing system to obtain the dynamic evolution law of the melting core and the instability mechanism of the excavation face, providing reference and effective suggestions for engineering construction to regulate the stability of the excavation face.

This scheme simulates the excavation surface of the frozen soil tunnel through the model system, measures the morphological parameters of the frozen soil by means of the sensing system installed in the model box, and collects and transmits these morphological parameters to the processing system by means of the acquisition device of the processing system. device, so that through the analysis and calculation of the processing device, the instability law and instability mechanism of the excavation surface of the frozen soil tunnel can be obtained, and then the stability of the tunnel excavation surface can be adjusted by relying on the instability law and instability mechanism, so as to avoid the tunnel in the actual construction process. Accidents such as landslides and roof falls occurred.

The model system includes a model box containing frozen soil and a tunnel model installed in the frozen soil. A larger hole is opened so that the tunnel model can be pushed out/slid out along the larger hole, so that the excavation surface (specifically, the tunnel face) and the The external communication enables heat exchange between the inside and outside of the tunnel, simulating the temperature difference between the permafrost in front of the excavation face and the excavation face, resulting in convective heat transfer, and enabling the tunnel model to push out/slide out of the permafrost, simulating the tunnel Under the dual effects of heat exchange and construction in the tunnel, the frozen soil in the model box will cause the excavation surface to become unstable, thus simulating the melting of the frozen soil in front of the excavation face and the impact of excavation construction activities during the tunnel excavation construction process. For the working condition of unstable tunnel excavation face, the frozen soil used in the tunnel model of this scheme can be selected according to the actual situation, and can simulate the tunnel construction conditions in different frozen soil regions. It has strong flexibility and a wide range of applications.

The simulation system is simple in composition and easy to operate, and can simulate the evolution process of the melting core in the process of convective heat transfer in actual engineering, thereby revealing the dynamic evolution law of the melting core and the instability mechanism of the excavation surface.

Preferably, the tunnel model includes a support section installed in the frozen soil and a control section extending to the outside of the larger hole, the outside of the support section is provided with a lining model groove, and the lining model groove is used to solidify and simulate the tunnel lining structure The support model, the lining model groove is provided with an opening for separation from the support model, the lining model groove is provided with a mounting support, and is connected in the model box by means of the mounting support.

The lining model groove is a rectangular parallelepiped structure, and its two ends in the length direction are in contact with the inner wall of the model groove. Among the six faces of the lining model groove, except the upper surface and the front end surface, the other four sides are closed. The inner wall of the model box with the larger hole is attached to one side. According to this, the side with larger holes in the model box is also regarded as the front end.

The lining model groove is a cuboid iron groove.

The support model simulates the lining during tunnel construction, and the support model is formed by cooling and hardening a mixture mixed with a certain amount of iron wire.

Arrange lining model slots for solidification of the support model for simulating tunnel lining. Import the raw materials of the support model into the lining model slots. After the raw materials are cooled and hardened, take out the model slots to form the lining structure. In this way, the real state of the lining in the permafrost environment can be simulated to ensure that the simulation system of this scheme is more suitable for the real environment of construction in permafrost regions, and more accurate morphological parameters of the excavation surface can be obtained, which can be used for the later excavation surface. Make adequate preparations for the analysis of the instability mechanism. An opening is provided on the lining model groove, and after the supporting model is solidified, the lining model groove is separated from the supporting model through the opening, so that the lining model groove is taken out.

A lining model groove is set on the outside of the tunnel model (i.e. the outer wall), and the lining structure closer to the permafrost area is made through the lining model groove to ensure that the results obtained by this simulation system are correct and reliable, thus having a higher reference and Analysis value.

Since the melting core formed in the permafrost surrounding rock is the fundamental source of the instability of the excavation face, by setting up the support model, the supporting effect of the support model on the frozen soil after the melting core is analyzed more thoroughly, and the frozen soil is analyzed The role of lining structure in the environment to prevent tunnel collapse.

Preferably, the model system further includes a rail device for supporting the sliding of the tunnel model.

A guide rail device is provided to support the tunnel model, so that the tunnel model slides along the guide rail device, so as to ensure that the tunnel model moves in a fixed direction, and avoid the movement of broken lines caused by deviation.

Preferably, the guide rail device includes screw rods arranged on both sides of the tunnel model, the screw rods pass through the model box and extend outward from the frozen soil, and the extension direction is parallel to the tunnel model, and the end of the control section of the tunnel model A supporting slide plate is connected, and the screw rod is fixed through the screw rod fixing pile after passing through the supporting slide plate.

The above-mentioned guide rail device enables the tunnel model to slide along the screw rod, and ensures that the sliding direction is fixed, so that the tunnel model does not shift or misdirect during the sliding process.

Preferably, the supporting slide plate is welded integrally with the tunnel model.

One end of the screw rod is located in the frozen soil, and the other end extends to the outside of the model box, and the fixed pile of the screw rod is located at one end outside the model box of the screw rod.

Preferably, the model box is a rectangular box with a back pressure plate installed on the top, the back pressure plate is detachably connected to the model box, so that the model box can be opened and closed through the back pressure plate, and the inner wall of the model box is provided with a heat insulation Floor.

Open and/or close the model box through the back pressure plate, so as to arrange and install the model system during the experiment, and fill the frozen soil with different properties according to the needs, and analyze the stability of the excavation face under various frozen soil environments .

Setting the heat insulation layer in the model box can effectively prevent the permafrost from dissipating heat, so that the permafrost can maintain its original state for a long time, ensuring that the simulation system has enough time for simulation experiments, and ensuring that the data is closer to reality.

The heat insulation layer is a heat insulation coil, and heat insulation coils are arranged along the six inner walls of the rectangular box. The thickness of the heat insulation coil corresponds to the volume of the model box, so as to ensure that the permafrost in the model box is kept in good condition for a long time. test status.

Preferably, a back pressure device is installed on the mold box, and the back pressure device includes a fixing plate installed on the top of the mold box, and locking rods are connected to both ends of the fixing plate.

Install the locking pull rod so that the fixed plate is tightened and fixed by the locking pull rod. The model box is filled with frozen soil. When the frozen soil fills the model box, it is necessary to ensure that the frozen soil is compacted and filled. The back pressure device of this plan is adopted. , capable of compacting frozen soil.

The model box is also provided with a wire hole for the wiring of the sensor system to pass through.

Since the sensing system for measuring the morphological parameters of the frozen soil is arranged in the frozen soil, the sensing system includes a variety of measuring equipment, and the measuring equipment needs to be connected with the processing system. Wiring through.

The wire passing hole is adapted to the wiring, so as to prevent the wire passing hole from being too large and prevent serious heat dissipation.

Preferably, the sensing system also includes a displacement meter, an earth pressure cell and a strain gauge, the earth pressure cell is installed on the outer layer of the lining structure, and an earth pressure cell is also arranged in the frozen soil near the excavation surface, so The displacement gauge is installed in the frozen soil surface layer close to the inner wall of the upper surface of the model box, and a displacement gauge is also arranged in the frozen soil surface layer of the inner wall of the rear end surface of the model box, and the strain gauges are arranged on the outer surface of the lining structure at the excavation surface.

The earth pressure cell is used to measure the pressure of the frozen soil at each measurement time point, so as to obtain the pressure change, and the displacement meter is used to measure the settlement in the frozen soil layer, so as to analyze the stability of the excavation surface according to the settlement.

The strain gauges are arranged, and the strains at each point of the lining structure are measured through the strain gauges, so as to provide basic data for the analysis of the dynamic evolution law of the melting core and the instability mechanism of the excavation face.

The strain gauge is a low-temperature uniaxial strain gauge, and the strain gauge is installed on the outer surface of the lining structure at the excavation surface by pasting.

Preferably, the displacement meter is a linear displacement sensor.

Preferably, the earth pressure cell is a special miniature earth pressure cell for model testing.

Preferably, the rear end surface of the model box is provided with small holes for installing support ribs, and the support ribs are connected with a fixing plate, and the support ribs and fixing plate are used for installing earth pressure cells and displacement gauges.

The supporting rib is a steel bar, the fixing plate is a square steel plate, and the steel bar and the square steel plate are welded and connected.

The end face with a larger hole on the model box is the front end face, and the opposite side is the rear end face. The support ribs are arranged on the rear end face, and the support ribs are fixed by the fixing plate. This structure is convenient for the installation of earth pressure cells and displacement gauges. , so that the earth pressure cell and displacement gauge are fixed.

The processing system includes a data collection device for collecting morphological parameters of the sensing system, the data collection device is connected to a processing device for storing and analyzing morphological parameters, and the processing device outputs processed data.

Preferably, the data acquisition device includes a data acquisition instrument and a strain gauge, and the data acquisition instrument is used to obtain the settlement measured by the displacement meter, the temperature of the measuring point measured by the temperature measuring instrument, and the strain of the lining structure measured by the strain gauge. The strain gauge is used to collect the seepage pressure measured by the seepage pressure measuring instrument and the earth pressure measured by the earth pressure box. The data acquisition instrument and the strain gauge are connected to a processing device. The processing device is a computer system, and the computer system can also store the transmitted data. The data monitored by the sensing system and built-in analysis module for data analysis.

Correspondingly, the present invention also provides an experimental method for adjusting and controlling the temperature field of the surrounding rock in front of the tunnel excavation face in permafrost, using the simulation system described above to regulate the temperature field, including the following steps:

a. Assemble the model system, determine the size of the tunnel model in advance, and open larger holes corresponding to the tunnel model on the model box, and open smaller holes and wire holes at the same time, fix the model box after preparing it, and place it in the Install the heat insulation layer on the inner wall of the model box;

b. Move the tunnel model to the inside of the model box, install the lining model groove, and make a support model through the lining model groove;

c. Remove the lining model tank, lay the frozen soil to be analyzed in the model box, and arrange the sensor system at the same time;

d. Push out the tunnel model to expose the tunnel surface and lining structure, and let in hot air of different temperatures;

e. Obtain the instability mechanism of the tunnel excavation face in frozen soil through the processing system.

When the frozen soil is contained in the model box, the type of frozen soil is similar to the frozen soil in the actual construction process. When analyzing the stability of the excavation surface during tunnel excavation in different frozen soil areas, the corresponding frozen soil type should be adopted , so as to obtain the tunnel stability mechanism in the permafrost region, and provide the corresponding scheme. The simulation system and experimental method of the invention can be used for simulation analysis of various frozen soil types, and provide suggestions and reference opinions for actual engineering construction.

After the tunnel model is launched, hot air of different temperatures is introduced into the tunnel face and the lining structure, which can simulate different external environmental conditions and obtain the same type of permafrost heat exchange under different environmental conditions. The stability situation, so as to conduct multi-faceted analysis, and obtain more comprehensive and broad data reference.

The experimental method of this scheme is tested through the aforementioned simulation system. After obtaining the instability mechanism of the tunnel excavation surface, corresponding countermeasures can be taken in the actual construction process to adjust the stability of the tunnel excavation surface in permafrost, so as to effectively avoid The occurrence of disasters such as tunnel collapse and roof fall.

Preferably, the temperature measuring instrument adopts a temperature sensor, and the seepage pressure measuring instrument adopts a piezometer, and the temperature sensor and the piezometer are arranged on multiple sections of the tunnel model, including the section near the excavation surface, at each On the section, the center of the tunnel model extends along multiple radial directions, and a plurality of the temperature sensors and a plurality of the piezometers are arranged in each radial direction. The arrangement density of pressure gauges is higher than that of other sections.

The arrangement of temperature sensors and piezometers in the above-mentioned way makes the layout of temperature sensors and piezometers more comprehensive, and can measure the temperature changes and seepage pressure changes of frozen soil in all regions, making data analysis and processing more accurate and closer to The change of frozen soil during the actual construction process makes the analysis of the instability mechanism of the excavation face obtained by the simulation system of this scheme more accurate.

Temperature sensors and piezometers with higher density are arranged in the section near the excavation surface, so as to more accurately measure the changes in frozen soil caused by the construction of the excavation surface.

The temperature sensor and the piezometer are arranged in sequence.

Preferably, the temperature sensor is a platinum resistance probe.

Preferably, the piezometer is a miniature piezometer dedicated to model testing.

Preferably, in the step a, the size of the tunnel model is determined according to the actual project, and the size of the tunnel model should satisfy the similarity of the heat transfer process between the actual construction tunnel prototype and the tunnel model, so that the convective heat transfer coefficient similarity ratio and geometric The product of similarity ratio is equal to the similarity ratio of thermal conductivity of frozen soil.

Preferably, in the step b, when making the support model, the support model is made of a certain mass ratio of water, gypsum, diatom mixture and iron wire, the support model raw materials are prepared in advance, and the lining model tank is installed Finally, pour the configured raw materials into the lining model tank, wait for it to cool and harden, and finally take out the lining model tank to form the lining structure of the model system.

Preferably, when the model system is equipped with a back pressure device, step c' is added after step c: when the frozen soil is laid on the top of the model box, a heat insulation layer is laid, and the back pressure plate is covered, and then the back pressure device is used to The frozen soil in the model box is compacted and the back pressure device is fixed.

In the process of the simulation system and the experimental method of the present invention, the frozen soil used is made by laboratory refrigeration equipment, and in order to ensure the freezing effect, the temperature of the surface layer of the frozen soil is consistent with that of the interior. Preferably, the frozen soil is realized in blocks. The size of each piece is made as 30cm×30cm×30cm.

Compared with prior art, the beneficial effect of the present invention:

1. The excavation surface of the frozen soil tunnel is simulated by the model system, the morphological parameters of the frozen soil are measured by the sensor system installed in the model box, and these morphological parameters are collected and transmitted to the processing system by the acquisition device of the processing system device, so that through the analysis and calculation of the processing device, the instability law and instability mechanism of the excavation surface of the frozen soil tunnel can be obtained, and then the stability of the tunnel excavation surface can be adjusted by relying on the instability law and instability mechanism, so as to avoid the tunnel in the actual construction process. disasters such as landslides and roof falls;

2. Arrange lining model grooves for solidification of the support model for simulating tunnel lining. Import the raw materials of the support model into the lining model grooves. After the raw materials are cooled and hardened, take out the model grooves to form the lining structure. In this way, the real state of the lining in the permafrost environment can be simulated to ensure that the simulation system of this scheme is more suitable for the real environment of construction in permafrost regions, and more accurate morphological parameters of the excavation surface can be obtained, which can be used for the later excavation surface. Make adequate preparations for the analysis of the instability mechanism;

3. Arranging temperature sensors and piezometers on multiple sections of the tunnel model, including sections near the excavation surface, on each of the sections, extending in multiple radial directions from the center of the tunnel model, each radial A plurality of said temperature sensors and a plurality of said piezometers are arranged in each direction, and the arrangement density of temperature sensors and piezometers on the section near the excavation face is higher than that of other sections. It is more comprehensive and can measure the temperature changes and seepage pressure changes of frozen soil in all regions, making data analysis and processing more accurate and closer to the changes of frozen soil in the actual construction process, so that the simulation system of this scheme can draw The analysis of the instability mechanism of the excavation face is more accurate;

4. Installing a thermal insulation layer in the model box can effectively prevent the permafrost from dissipating heat, so that the permafrost remains in its original state for a long time, ensuring that the simulation system has enough time for simulation experiments and ensuring that the data is closer to reality;

5. When the frozen soil is contained in the model box, the type of frozen soil is similar to the frozen soil in the actual construction process. When analyzing the stability of the excavation surface during tunnel excavation in different frozen soil areas, the corresponding frozen soil should be adopted accordingly. Soil types, so as to obtain the tunnel stability mechanism in the permafrost region, and provide corresponding solutions. The simulation system and experimental method of the present invention can be used for simulation analysis of various frozen soil types, and provide suggestions and reference opinions for the construction of actual projects;

6. After the tunnel model is launched, hot air of different temperatures is introduced into the tunnel face and lining structure, which can simulate different external environmental conditions, and excavate when the same type of frozen soil is exchanged under different environmental conditions. The stability of the surface can be analyzed in various aspects to obtain a more comprehensive and extensive data reference.

Description of drawings:

Fig. 1 is a schematic diagram of the model system structure of the simulation system of the present invention.

Fig. 2 is a schematic layout diagram of the sensing system (temperature sensor and piezometer) of the simulation system of the present invention.

FIG. 3 is a schematic layout diagram of another viewing angle of FIG. 2 .

Fig. 4 is a schematic layout diagram of the sensing system (temperature sensor, piezometer and strain gauge) of the simulation system of the present invention.

Fig. 5 is a schematic layout diagram of the sensing system (displacement gauge and earth pressure cell) of the simulation system of the present invention.

FIG. 6 is a schematic layout diagram of another viewing angle of FIG. 5 .

Fig. 7 is a flow chart of the steps of the experimental method for controlling the temperature field of the surrounding rock in front of the excavation face of the frozen soil tunnel using the simulation system of the present invention.

Marks in the figure: 1-model box, 2-tunnel model, 21-control section, 3-excavation surface, 4-lining model groove, 5-support model, 6-rail device, 61-screw, 62-wire Rod fixing pile, 7-support slide, 8-back pressure plate, 9-insulation layer, 10-back pressure device, 101-fixed plate, 102-locking rod, 11-temperature measuring instrument, 12-seepage pressure measuring instrument, 13-strain gauge, 14-displacement gauge, 15-earth pressure cell, 16-support rib, 17-fixed plate.

detailed description

The present invention will be further described in detail below in conjunction with test examples and specific embodiments. However, it should not be understood that the scope of the above subject matter of the present invention is limited to the following embodiments, and all technologies realized based on the content of the present invention belong to the scope of the present invention.

Example 1

As shown in Figure 1 to Figure 6:

A simulation system for regulating the stability of the tunnel excavation surface in frozen soil, including a model system, a sensing system and a processing system, wherein the model system includes a model box 1 and a tunnel model 2 for containing frozen soil, and the model A larger hole for installing the tunnel model 2 is opened on the box 1, so that the tunnel model 2 can be pushed out from the larger hole, and then the excavation surface 3 of the simulated frozen soil is communicated with the outside world;

The sensing system includes a temperature measuring instrument 11 and a seepage pressure measuring instrument 12. The temperature measuring instrument 11 and the seepage pressure measuring instrument 12 are installed in the model box 1 and connected with the processing system for measuring the temperature of the frozen soil excavation surface. temperature and seepage pressure;

The processing system includes a data collection device for collecting morphological parameters of the sensing system, the data collection device is connected to a processing device for storing and analyzing morphological parameters, and the processing device outputs processed data.

Permafrost is extremely sensitive to temperature changes. During tunnel excavation, the heat inside and outside the tunnel spontaneously protrudes from the permafrost surrounding rock in front of the excavation face to generate convective heat transfer, thereby forming a melting core in the permafrost surrounding rock. The root cause of the instability of the excavation surface of frozen soil tunnels is the melting core. In this scheme, after the tunnel model is pushed out/slid out from the frozen soil, the simulated frozen soil excavation surface connected to the outside world is exposed. Temperature difference, convective heat exchange, so that the inside of the permafrost begins to melt to form a melting zone, simulating the melting core generated during the construction process in the permafrost area, and measuring the shape of the permafrost through the sensor system installed in the permafrost (including temperature , seepage pressure, etc.), relying on the analysis of the processing system to obtain the dynamic evolution law of the melting core and the instability mechanism of the excavation face, providing reference and effective suggestions for engineering construction to regulate the stability of the excavation face.

This scheme simulates the excavation surface of the frozen soil tunnel through the model system, measures the morphological parameters of the frozen soil by means of the sensing system installed in the model box, and collects and transmits these morphological parameters to the processing system by means of the acquisition device of the processing system. device, so that through the analysis and calculation of the processing device, the instability law and instability mechanism of the excavation surface of the frozen soil tunnel can be obtained, and then the stability of the tunnel excavation surface can be adjusted by relying on the instability law and instability mechanism, so as to avoid the tunnel in the actual construction process. Accidents such as landslides and roof falls occurred.

The model system includes a model box containing frozen soil and a tunnel model installed in the frozen soil. A larger hole is opened so that the tunnel model can be pushed out/slid out along the larger hole, so that the excavation surface (specifically, the tunnel face) and the The external communication enables heat exchange between the inside and outside of the tunnel, simulating the temperature difference between the permafrost in front of the excavation face and the excavation face, resulting in convective heat transfer, and enabling the tunnel model to push out/slide out of the permafrost, simulating the tunnel Under the dual effects of heat exchange and construction in the tunnel, the frozen soil in the model box will cause the excavation surface to become unstable, thus simulating the melting of the frozen soil in front of the excavation face and the impact of excavation construction activities during the tunnel excavation construction process. For the working condition of unstable tunnel excavation face, the frozen soil used in the tunnel model of this scheme can be selected according to the actual situation, and can simulate the tunnel construction conditions in different frozen soil regions. It has strong flexibility and a wide range of applications.

The simulation system is simple in composition and easy to operate, and can simulate the evolution process of the melting core in the process of convective heat transfer in actual engineering, thereby revealing the dynamic evolution law of the melting core and the instability mechanism of the excavation surface.

The tunnel model 2 includes a support section installed in frozen soil and a control section 21 extending to the outside of the larger hole. The outside of the support section is provided with a lining model groove 4. In Fig. 1, since the support section extends into the lining model groove 4, Therefore, the support section is not visible in the figure, and the lining model groove 4 is used to solidify the supporting model 5 of the simulated tunnel lining structure, and the lining model groove 4 is provided with an opening for separating from the supporting model 5. The groove 4 is provided with a mounting support, and is connected in the mold box 4 by means of the mounting support.

As one of the preferred embodiments, the lining model tank 4 is a rectangular parallelepiped structure, and its two ends in the longitudinal direction are in contact with the inner wall of the model tank 1. Among the six sides of the lining model tank 4, except the upper surface and the front end surface, the other four sides Closed, the front end surface is a side that is attached to the inner wall of the mold box with a larger hole. According to this, the side with larger holes in the model box is also regarded as the front end.

Further, the lining model tank 4 is a cuboid iron tank, and the tunnel model 2 is a thin-walled aluminum barrel.

The support model 5 simulates the lining structure during tunnel construction, and the support model 5 is formed by cooling and hardening a mixture mixed with a certain amount of iron wire.

The lining model groove 4 is arranged to solidify the support model 5 for simulating the tunnel lining structure. The raw materials of the support model 5 are introduced into the lining model groove 4. After the raw material is cooled and hardened, the lining model groove 4 is taken out to form the lining structure. In this way, the real state of the lining in the permafrost environment can be simulated, ensuring that the simulation system of this scheme is more suitable for the real environment of construction in permafrost regions, and obtaining more accurate shape parameters of the excavation surface. Make adequate preparations for the analysis of the stabilization mechanism. An opening is provided on the lining model groove, and after the supporting model is solidified, the lining model groove is separated from the supporting model through the opening, so that the lining model groove is taken out.

A lining model groove 4 is set on the outside (i.e., the outer wall) of the tunnel model 2, and the support model 5 is made through the lining model groove 4, so that the structure of the model system is closer to the actual working conditions in the permafrost region, ensuring that the simulation system can obtain The results are correct and reliable, thus having higher reference and analysis value.

Since the melting core formed in the permafrost surrounding rock is the fundamental source of the instability of the excavation face, by setting up the support model, the supporting effect of the support model on the frozen soil after the melting core is analyzed more thoroughly, and the frozen soil is analyzed The role of lining structure in the environment to prevent tunnel collapse.

In order to ensure the movement of the tunnel model 2 in a fixed direction and avoid the movement of the broken line due to deviation, a guide rail device 6 for supporting the sliding of the tunnel model 2 is also provided at the control section 21 of the tunnel model 2 .

A guide rail device 6 is provided for supporting the tunnel model 2 so that the tunnel model 2 can slide along the guide rail device 6 .

As one of the preferred implementations, the guide rail device 6 includes screw rods 61 arranged on both sides of the tunnel model 2, and the screw rods 61 pass through the model box 1 and extend outward from the frozen soil, and their extension direction is the same as that of the tunnel model. 2 parallel, the end of the control section 21 of the tunnel model 2 is connected with a support slide 7, the screw 61 passes through the support slide 7 and is fixed by a screw fixing pile 62, and the guide rail device 6 enables the tunnel model 2 to move along the screw. 61 to slide, to ensure that the sliding direction is fixed, so that the tunnel model does not shift or misdirect during the sliding process.

Further, the supporting slide 7 is welded together with the tunnel model 2, and the supporting slide 7 and the screw are made of stainless steel, which can greatly increase the service life of the model system.

One end of the screw rod 61 is located in the frozen soil, and the other end extends to the outside of the model box 1 , and the screw fixing pile 62 is located at one end of the screw rod 62 outside the model box.

As one of the preferred embodiments, the model box 1 is a rectangular box with a back pressure plate 8 installed on the top, and the back pressure plate 8 is detachably connected with the model box 1, so that the model box 1 can be opened and closed through the back pressure plate 8, The inner wall of the model box 1 is provided with a heat insulating layer 9, and the model box 1 is opened and/or closed through the back pressure plate 8, so that the model system is arranged and installed during the experiment process, and frozen materials with different properties are filled as required. Soil, the stability analysis of the excavation face under various permafrost environments is carried out.

Setting the heat insulation layer in the model box can effectively prevent the permafrost from dissipating heat, so that the permafrost can maintain its original state for a long time, ensuring that the simulation system has enough time for simulation experiments, and ensuring that the data is closer to reality.

Further, the material of the back pressure plate 8 is iron, the heat insulation layer 9 is a heat insulation coil, and heat insulation coils are arranged along the six inner walls of the rectangular box. The thickness of the heat insulation coil is the same as that of the model box. corresponding to the corresponding volume, to ensure that the permafrost in the model box is in the required test state for a long time.

As one of the preferred implementations, the model box 1 is equipped with a back pressure device 10, the back pressure device 10 includes a fixed plate 101 installed on the top of the model box 1, the two ends of the fixed plate 101 are connected with locks Tighten the tie rod 102.

Install the locking pull rod 102, so that the fixed plate 101 is tightened and fixed by the locking pull rod 102, and the frozen soil is filled in the model box 1. When the frozen soil fills the model box 1, it is necessary to ensure that the frozen soil is compacted and filled. The back pressure device 10 of the scheme can carry out compaction treatment to frozen soil.

The model box 1 is also provided with a wire hole for the wiring of the sensing system to pass through. Since a sensing system for measuring the morphological parameters of the frozen soil is arranged in the frozen soil, the sensing system includes a variety of measuring equipment, measuring equipment It needs to be connected with the processing system, and the wiring hole is used for measuring equipment to pass through by opening a wire hole on the model box.

As one of the implementations, as shown in Figure 4, Figure 5 and Figure 6, the sensor system also includes a displacement meter 14, an earth pressure cell 15 and a strain gauge 13, and the earth pressure cell 15 is installed on the support model 5 (equivalent to the lining structure) the outer layer is also arranged with an earth pressure cell near the excavation surface 3 in the frozen soil, and the displacement gauge 14 is installed in the frozen soil surface layer near the inner wall of the upper surface of the model box 1, and the model box Displacement gauges 14 are also arranged in the permafrost surface layer on the inner wall of the rear end surface of 1, and the strain gauges 13 are arranged on the outer surface of the supporting model 5 at the excavation surface 3 .

The earth pressure cell is used to measure the pressure of the frozen soil at each measurement time point, so as to obtain the pressure change, and the displacement meter is used to measure the settlement in the frozen soil layer, so as to analyze the stability of the excavation surface according to the settlement.

The strain gauges are arranged, and the strains at each point of the lining structure are measured through the strain gauges, so as to provide basic data for the analysis of the dynamic evolution law of the melting core and the instability mechanism of the excavation face.

Further, the strain gauge 13 is a low-temperature uniaxial strain gauge, and the strain gauge 13 is installed on the outer surface of the support model 5 (lining structure) at the excavation surface 3 by pasting.

Further, the displacement meter 14 is a linear displacement sensor.

Further, the earth pressure cell 15 is a special miniature earth pressure cell for model testing.

As one of the implementations, the rear end surface of the model box 1 is provided with a small hole for installing the support rib 16, and the support rib 16 is connected with a fixing plate 17, and the support rib 16 and the fixing plate 17 are used for installing Earth pressure cell 15 and displacement gauge 14.

The supporting rib 16 is a steel bar, the fixing plate 17 is a square steel plate, and the steel bar and the square steel plate are welded and connected.

The end face with a larger hole on the model box is the front end face, and the opposite side is the rear end face. The support ribs are arranged on the rear end face, and the support ribs are fixed by the fixing plate. This structure is convenient for the installation of earth pressure cells and displacement gauges. , so that the earth pressure cell and displacement gauge are fixed.

The processing system includes a data collection device for collecting morphological parameters of the sensing system, the data collection device is connected to a processing device for storing and analyzing morphological parameters, and the processing device outputs processed data.

As one of the implementations, the data acquisition device includes a data acquisition instrument and a strain gauge, and the data acquisition instrument is used to obtain the settlement measured by the displacement meter, the temperature of the measuring point measured by the temperature measuring instrument, and the lining measured by the strain gauge. Structural strain, the strain gauge is used to collect the seepage pressure measured by the seepage pressure measuring instrument and the earth pressure measured by the earth pressure cell, the data acquisition instrument and the strain gauge are connected to a processing device, and the processing device is a computer system.

Example 2

As shown in Fig. 1 and Fig. 7, the experimental method for controlling the temperature field of the surrounding rock in front of the tunnel excavation face in permafrost uses the simulation system in Example 1 to regulate the temperature field, including the following steps:

a. Assemble the model system, pre-determine the size of the tunnel model 2, and open a larger hole corresponding to the tunnel model 2 on the model box 1, and open smaller holes and wire holes at the same time, and fix the model box 1 after preparing it , and install a thermal insulation layer 9 on the inner wall of the model box 1;

b. Move the tunnel model 2 to the inside of the model box 1, install the lining model groove 4, and make the support model 5 through the lining model groove 4, and the front end of the lining model groove 4 is close to the inner wall of the model box 1 to ensure no slurry leakage;

c. Remove the lining model tank 4, lay the frozen soil to be analyzed in the model box 1, and arrange the sensor system at the same time;

d. Push out the tunnel model 2 to expose the tunnel face and support model 5 (lining structure), and let hot air of different temperatures flow in;

e. Obtain the instability mechanism of tunnel excavation face 3 in permafrost through the processing system.

When the frozen soil is contained in the model box, the type of frozen soil is similar to the frozen soil in the actual construction process. When analyzing the stability of the excavation surface during tunnel excavation in different frozen soil areas, the corresponding frozen soil type should be adopted , so as to obtain the tunnel stability mechanism in the permafrost region, and provide the corresponding scheme. The simulation system and experimental method of the invention can be used for simulation analysis of various frozen soil types, and provide suggestions and reference opinions for actual engineering construction.

After the tunnel model is launched, hot air of different temperatures is introduced into the tunnel face and the lining structure, which can simulate different external environmental conditions and obtain the same type of permafrost heat exchange under different environmental conditions. The stability situation, so as to conduct multi-faceted analysis, and obtain more comprehensive and broad data reference.

The experimental method of this embodiment is tested by the aforementioned simulation system. After obtaining the instability mechanism of the tunnel excavation surface, corresponding countermeasures can be taken in the actual construction process to adjust the stability of the tunnel excavation surface in permafrost, thereby effectively Avoid disasters such as tunnel collapse and roof fall.

As one of the preferred implementations, as shown in Figure 2 and Figure 3, the temperature measuring instrument 11 adopts a temperature sensor, and the seepage pressure measuring instrument 12 adopts a piezometer, and the temperature sensor and the piezometer are arranged in the tunnel model On multiple sections, including the section near the excavation surface, on each of the sections, the center of the tunnel model extends along multiple radial directions, and each radial direction is arranged with multiple temperature sensors and multiple For the piezometer, the arrangement density of the temperature sensor and the piezometer on the section near the excavation face is higher than that of other sections.

The arrangement of temperature sensors and piezometers in the above-mentioned way makes the layout of temperature sensors and piezometers more comprehensive, and can measure the temperature changes and seepage pressure changes of frozen soil in all regions, making data analysis and processing more accurate and closer to The change of frozen soil during the actual construction process makes the analysis of the instability mechanism of the excavation face obtained by the simulation system of this scheme more accurate.

Temperature sensors and piezometers with higher density are arranged in the section near the excavation surface, so as to more accurately measure the changes in frozen soil caused by the construction of the excavation surface.

Further, the temperature sensor and piezometer are arranged in sequence, the temperature sensor is a platinum resistance probe, and the piezometer is a miniature piezometer specially used for model testing.

In the step a, the size of the tunnel model is determined according to the actual project, and the size of the tunnel model should satisfy the similarity of the heat transfer process between the actual construction of the tunnel prototype and the tunnel model, so that the similarity ratio of the convective heat transfer coefficient and the geometric similarity ratio in the model The product is equal to the thermal conductivity similarity ratio of frozen soil.

In the step b, when making the support model, the support model is made of water, gypsum, diatom mixture and iron wire with a certain mass ratio, the support model raw materials are prepared in advance, and after the lining model groove is installed, the The configured raw materials are poured into the lining model tank, wait for it to cool and harden, and finally take out the lining model tank to form the lining structure of the simulation system.

Claims (10)

1. A simulation system for regulating the stability of the tunnel excavation surface in permafrost, including a model system, a sensor system and a processing system, wherein: The model system includes a model box and a tunnel model for containing frozen soil, and a larger hole for installing the tunnel model is opened on the model box, so that the tunnel model can be pushed out from the larger hole, and then the frozen soil can be simulated. The excavation surface of the soil communicates with the outside world; The sensing system includes a temperature measuring instrument and a seepage pressure measuring instrument, the temperature measuring instrument and the seepage pressure measuring instrument are installed in the model box and connected with the processing system for measuring the morphological parameters of the excavation surface of frozen soil; The processing system includes a data collection device for collecting morphological parameters of the sensing system, the data collection device is connected to a processing device for storing and analyzing morphological parameters, and the processing device outputs processed data. 2. The simulation system for adjusting and controlling the stability of the tunnel excavation face in frozen soil according to claim 1, wherein the tunnel model includes a support section installed in the frozen soil and a control panel extending to the outside of the larger hole. Section, the outer side of the support section is provided with a lining model groove, the lining model groove is used to solidify the support model for simulating the tunnel lining structure, the lining model groove is provided with an opening for separation from the support model, the lining model The slot is provided with a mounting bracket. 3. The simulation system for controlling the stability of the tunnel excavation surface in permafrost according to claim 2, wherein the model system further comprises a guide rail device for supporting the sliding of the tunnel model. 4. The simulation system for regulating and controlling the stability of the tunnel excavation surface in permafrost according to any one of claims 1-3, characterized in that, the rectangular box body of the model box, the top plate of the rectangular box body is openable The back pressure plate enables the model box to be opened and closed through the back pressure plate, and the inner wall of the model box is provided with a heat insulation layer. 5. The simulation system for adjusting and controlling the stability of the tunnel excavation surface in permafrost according to any one of claims 1-3, wherein a back pressure device is installed on the model box, and the back pressure device includes a The fixed plate on the top of the model box, the two ends of the fixed plate are connected with locking pull rods. 6. according to one of claim 1-3, is used for regulating and controlling the simulation system of the excavation face stability of permafrost tunnel, it is characterized in that, described sensing system also comprises displacement meter, earth pressure cell and strain gauge, so The earth pressure cell is installed on the outer layer of the lining structure, and an earth pressure cell is also arranged in the frozen soil near the excavation surface. The displacement meter is installed in the frozen soil surface layer near the upper surface inner wall of the model box, and the model box Displacement gauges are also arranged in the frozen soil surface layer of the inner wall of the rear end face, and the strain gauges are arranged on the outer surface of the lining structure at the excavation face. 7. The simulation system for adjusting and controlling the stability of the tunnel excavation face of frozen soil according to claim 6, wherein the rear end face of the model box is provided with a smaller hole for installing support ribs, and the support The ribs are connected with a fixing plate, and the supporting ribs and the fixing plate are used for installing earth pressure cells and displacement gauges. 8. The simulation system for controlling the stability of the tunnel excavation face in frozen soil according to claim 7, wherein the data acquisition device comprises a data acquisition instrument and a strain gauge, and the data acquisition instrument is used to obtain displacement The settlement measured by the meter, the temperature of the measuring point measured by the temperature sensor and the strain of the lining structure measured by the strain gauge, the strain gauge is used to collect the seepage pressure measured by the seepage pressure measuring instrument and the earth pressure measured by the earth pressure box, the data The acquisition instrument and the strain gauge are connected to a processing device, which is a computer system. 9. An experimental method for regulating the surrounding rock temperature field in front of the tunnel excavation face in permafrost, is characterized in that, adopts the simulation system as described in one of claims 1-8 to regulate the temperature field, comprising the following steps: a. Assemble the model system, determine the size of the tunnel model in advance, and open larger holes corresponding to the tunnel model on the model box, and open smaller holes and wire holes at the same time, fix the model box after preparing it, and place it in the Install the heat insulation layer on the inner wall of the model box; b. Move the tunnel model to the inside of the model box, install the lining model groove, and make a support model through the lining model groove; c. Remove the lining model tank, lay the frozen soil to be analyzed in the model box, and arrange the sensor system at the same time; d. Push out the tunnel model to expose the tunnel surface and lining structure, and let in hot air of different temperatures; e. Obtain the instability mechanism of the tunnel excavation face in frozen soil through the processing system. 10. according to claim 9, be used for regulating and controlling the experimental method of surrounding rock temperature field in front of excavation face of permafrost tunnel, it is characterized in that, described temperature measuring instrument adopts temperature sensor, and described seepage pressure measuring instrument adopts piezometer , temperature sensors and piezometers are arranged on multiple sections of the tunnel model, including sections near the excavation face, on each of said sections, extending along multiple radial directions with the center of the tunnel model, each radial direction A plurality of the temperature sensors and a plurality of the piezometers are arranged, and the density of the temperature sensors and the piezometers on the section near the excavation surface is higher than that of other sections.