Visual test device and method for complex tunnel physical model under true three-dimensional stress

Abstract

The invention relates to a visual test device and method for a complex tunnel physical model under true three-dimensional stress, the device is formed by combining loading plates in a hanging and buckling mode, the device is adaptive to tunnel models of different shapes and angles, monitoring equipment such as sound, light, electricity and heat can be installed, and the thickness design of the loading plates is carried out according to an established thickness design method; the test method comprises the following steps: placing a tunnel model on a loading bottom plate, installing loading plates and observation cushion blocks in all directions, placing monitoring equipment in observation holes, placing the device on a true triaxial loading test machine, designing boundary static and dynamic loads according to a proposed load similarity theory and material damage conditions, and carrying out real-time test on the boundary static and dynamic loads. And applying three-dimensional static and dynamic disturbance loads to the tunnel model, recording deformation and damage conditions, and performing data analysis. The stress state of tunnel excavation in deep rock engineering can be effectively simulated, real-time observation and recording of tunnel surrounding rock deformation and damage characteristics are achieved, and an effective means is provided for researching the fracture evolution process and mechanism of tunnel surrounding rock under the true three-dimensional stress condition.

Description

Technical Field

[0001] The invention belongs to the technical field of rock mechanics, and in particular relates to a visualization test device and method for a complex tunnel physical model under true three-dimensional stress. Background Art

[0002] During the excavation of a deep buried tunnel with high geostress, the combined effects of three-dimensional high-redistributed stress and excavation dynamic disturbance can easily lead to engineering disasters such as spalling, landslides, and rockbursts, which is a common problem faced by deep rock engineering. In order to explore the fracture evolution process and mechanism of tunnel surrounding rock under three-dimensional stress conditions, physical model testing is an effective means.

[0003] At present, the loading device of tunnel physical model test mainly has the following problems:

[0004] 1. Existing tunnel physical model tests mostly use uniaxial or biaxial loading methods, which are difficult to simulate three-dimensional geostress fields, especially difficult to adapt to true three-dimensional dynamic and static combined loading.

[0005] 2. The current loading device of the tunnel physical model is difficult to adapt to complex tunnel physical models such as different angles and tunnel shapes. In addition, the previous tunnel physical model loading device assembly method is complicated and the experimental efficiency is low. At the same time, there is a loading gap between the loading device and the physical model, which leads to uneven stress and stress concentration, resulting in preferential damage to this part, which interferes with the analysis of the tunnel damage mechanism.

[0006] 3. During the physical model experiment, the model is usually completely wrapped by the fixture, which makes it difficult to visually observe the failure evolution process of the tunnel surrounding rock under three-dimensional stress, and it is difficult to effectively detect the internal fracture. The deformation between the tunnel free surface and the deep surrounding rock and the uncontrolled evolution process of the fracture zone are difficult to obtain.

[0007] 4. The loading device of the tunnel physical model needs to meet the requirements of high-pressure testing. However, when designing the loading device of the tunnel physical model, there is a lack of specific calculation standards for the design of the loading plate thickness. At the same time, in order to ensure that the failure evolution process of the tunnel physical model is consistent with the actual situation on site, there is currently a lack of effective three-dimensional loading stress determination methods.

[0008] The above problems limit the research on the failure evolution mechanism of surrounding rock of complex tunnels under three-dimensional stress, especially the in-depth research on the relationship between true three-dimensional stress and different spatial relationships of tunnels with different shapes. Therefore, it is urgent to invent a visualization test device and method for the physical model of complex tunnels under true three-dimensional stress. Summary of the invention

[0009] In order to overcome the shortcomings of the prior art, the present invention proposes a visualization test device and method for complex tunnel physical models under true three-dimensional stress. It can adapt to the dynamic disturbance loading test of complex tunnel physical models under true triaxial stress field, simplify the assembly of the test device, avoid stress concentration caused by gaps between the device and the physical model, and realize the use of acoustic, optical, electrical, thermal and other monitoring technologies to observe and record the deformation and failure characteristics of the tunnel from the free surface to the deep surrounding rock in real time during the loading process, solving the problems existing in the above-mentioned background technology.

[0010] To achieve the above purpose, the technical solution of the present invention is as follows:

[0011] The visualization test device for complex tunnel physical model under true three-dimensional stress includes a loading top plate with a dynamic disturbance rod and an observation hole, a hook connector that can realize the linear free movement of the device side plate during the loading test, a loading front plate with an acoustic emission probe installation hole and an observation hole adapted to tunnels of different shapes and angles, a loading rear plate with an acoustic emission probe installation hole, an observation loading pad for installing optical and thermal imaging observation instruments, a loading left plate and a loading right plate with an acoustic, optical, and thermal drilling monitor installation observation hole, and a loading bottom plate; the loading top plate is a rectangular parallelepiped as a whole, which is placed at the top of the whole device, and a dynamic disturbance rod and an observation hole are arranged at the center of the loading top plate. The hole of the disturbance application rod is provided with a dynamic disturbance rod, and the loading top plate, the loading right plate and the loading front plate are connected through the linear free-moving ear connector of the loading plate to form a three-way six-sided tunnel loading cavity, and a tunnel physical model is placed in the loading cavity. The tunnel physical model arranges radial full-length observation holes along the section and axis, and a multi-point displacement meter and an acoustic, optical, and thermal drilling monitor are arranged in the observation hole; the acoustic, optical, and thermal drilling monitor has a built-in ultrasonic monitoring device, which can measure the wave velocity of surrounding rock failure on the drilling path, and has a built-in 360° miniature panoramic high-definition camera with thermal imaging function, which can monitor the surrounding rock along the drilling path. The monitor is pulled from the free face of the tunnel to the deep surrounding rock, scans and records the fracture of the borehole surrounding rock, and obtains the thermal imaging map when the surrounding rock is fractured. The built-in piezoelectric sensor obtains the damage position and damage of the surrounding rock through the stress wave attenuation effect on the piezoelectric sensor when the surrounding rock is damaged; the ear connector is installed on the side wall of the loading top plate by screws, and each ear is provided with a guide rod and a guide hole for linear movement of the guide rod, and the guide rod is fixed to the loading right plate and the loading front plate to constrain the horizontal displacement of the side plate during loading and assist in the installation and fixation of each loading plate; the loading front plate is provided with a plurality of holes and angles to adapt to different hole shapes and angles. The hollow rotating cylinder of the degree tunnel runs through the entire loading front plate, and the hollow rotating cylinder is provided with a scale dial for aligning the angle and an angle fixing bolt, and the loading front plate is provided with an acoustic emission probe mounting hole; the loading rear plate has the same shape and size as the loading front plate, and is also provided with an acoustic emission probe mounting hole, which is directly placed on the loading bottom plate and close to the model; the observation loading pad is connected to the loading front plate by bolts, the hollow rotating cylinder runs through the entire observation loading pad, and is provided with a scale dial for aligning the angle, and a 360° miniature panoramic high-definition camera with thermal imaging function is placed on the observation loading pad.

[0012] The loading left plate and the loading right plate have the same shape and size, and are directly placed on the loading bottom plate and closely attached to the model. The loading left plate and the loading right plate are provided with observation holes for installing acoustic, optical, thermal and drilling monitors, so as to drill through the observation holes of the tunnel physical model, and a multi-point deformation meter and an acoustic, optical, thermal and drilling monitor are installed inside the observation holes. A guide hole connected to a guide rod is provided on the right loading plate; the loading bottom plate and the loading top plate have the same shape and size, and are directly overlapped with the lateral loading plate, and are also provided with observation holes for installing acoustic, optical, thermal and drilling monitors;

[0013] The thickness of the loading top plate is determined as follows:

[0014] The loading top plate is simplified into a homogeneous flat plate of the same size as the loading top plate, and the maximum deflection of the loading top plate when subjected to the maximum loading load is calculated. When a dynamic disturbance rod is set in the hole, the calculation method is as follows: p0=σ0a 2 (2)

[0015] Where D is the bending stiffness of the loaded top plate, h is the thickness of the loaded top plate, v is the Poisson's ratio of the loaded top plate, E is the elastic modulus of the loaded top plate, p0 is the maximum load applied on the loaded top plate, σ0 is the stress value on the boundary of the tunnel physical model, and a0 is the edge length of the tunnel physical model;

[0016] The loaded top plate can be split into an equivalent simplified calculation model that is 1 / 4 the size of the prototype. The load acting on the equivalent simplified calculation model The load p acting on the equivalent simplified calculation model 01 Converted into radially distributed linear load q0, the calculation formula is as follows:

[0017] Where x a is a dimensionless variable;

[0018] The calculation formula for the deflection w of the loaded top plate is as follows:

[0019] Where w(x,y) is the deflection of the loaded top plate, α1 is the constraint coefficient of the radial unit of the loaded top plate, G is the shear modulus of the loaded top plate, I0 is the moment of inertia of the radial unit of the loaded top plate, d is the diameter of the loading area on the loaded top plate, k is the material coefficient of the loaded top plate, p1 is the reaction force of the tunnel physical model on the loaded top plate, and a is the side length of the loaded top plate;

[0020] When no dynamic disturbance rod is set in the hole, the calculation formula of the load p2 applied on the loading top plate on the tunnel physical model is as follows:

[0021] Where d0 is the diameter of the hole in the loading top plate;

[0022] The loaded top plate can be split into an equivalent simplified calculation model that is 1 / 4 the size of the prototype. The load acting on the equivalent simplified calculation model The load p acting on the equivalent simplified calculation model 21 Converted into radially distributed linear load q2, the calculation formula is as follows:

[0023] The calculation formula for the deflection w of the loaded top plate is as follows:

[0024] Where p3 is the reaction force of the tunnel physical model on the loaded top plate;

[0025] The thickness h of the loading top plate must ensure that the maximum deflection w of the loading plate satisfies w<0.02mm;

[0026] The method for visualizing a complex tunnel physical model under true three-dimensional stress includes the following steps:

[0027] Step 1: After determining the direction of the tunnel axis, place the tunnel physical model on the loading base plate and align the two sides of the tunnel physical model with the device base plate;

[0028] Step 2: Place the loading top plate on the tunnel physical model, and then align the two sides of the loading top plate without ear connectors with the edges of the tunnel physical model;

[0029] Step 3: Install the front loading plate and the right loading plate together with the top loading plate through the ear connectors in sequence, and install the guide rods on the ear connectors into the corresponding guide holes on the loading plate, so that the front loading plate and the right loading plate are both in close contact with the physical model and can move horizontally;

[0030] Step 4: Place the rear loading plate and the left loading plate on the reserved edge of the bottom loading plate in sequence, and make the rear loading plate and the left loading plate close to the physical model;

[0031] Step 5: Install the observation loading pad to the loading front plate through bolts, rotate the hollow rotating cylinder with the same shape as the tunnel on the observation loading pad to the same angle as the tunnel, fix the hollow rotating cylinder with the angle fixing bolts, and then install the 360° miniature panoramic high-definition and thermal imaging camera in the observation loading pad. Drill preset observation holes at the observation holes of the loading left plate, loading right plate, loading top plate, and loading bottom plate. Install the multi-point deformation meter at a specific position from the surface to the deep layer of the observation hole, and set an acoustic, optical, and thermal drilling monitor in the observation hole. Then correctly place the installed loading device in the loading area of ​​the true triaxial loading tester, and turn on the acoustic emission and optical, thermal imaging and other observation and recording equipment;

[0032] Step 6: Operate the true triaxial loading test machine to simulate the stress path of the three-dimensional ground stress redistribution and blasting disturbance coupling: Load the tunnel physical model in three directions at the same loading rate v σ Apply static load to the preset stress value, when σ 20 and σ 30 After reaching the preset stress value, maintain σ20 and σ 30 Keep constant and continue to improve σ 10 to the preset value and maintain it for a period of time t0 and then start to m , the frequency f is used for a sinusoidal perturbation with a period of T, and after the perturbation ends, the gradient σ t Increase σ 10 , apply dynamic disturbance in the same way as above, and repeat this cycle;

[0033] The preset stress value σ 10 , σ 20 and σ 30 According to the load similarity theory and material failure conditions, the specific calculation method is as follows:

[0034] a. The physical model of the tunnel should maintain similar geometric shapes and dimensions to the prototype, and the corresponding angles should be equal, that is, any corresponding linear length of the prototype and the model should maintain a certain proportional relationship, and the scale of the prototype and the model should be expressed as λ. The geometric similarity scale λ L The calculation formula is as follows:

[0035] Where d P is the equivalent diameter of the prototype tunnel, d M is the equivalent diameter of the tunnel physical model; the equivalent diameter is the diameter of each type of tunnel when it is converted into a circular tunnel of equal area. The equivalent diameter of the prototype tunnel is d P , the equivalent diameter d of the tunnel physical model M The calculation formula is as follows:

[0036] Where S P is the cross-sectional area of ​​the prototype tunnel, S M is the cross-sectional area of ​​the tunnel of the tunnel physical model;

[0037] Severity similarity ratio λ γ The calculation formula is as follows:

[0038] Where γ P is the original rock density, γ M is the weight of the tunnel physical model, λ γ is the original rock density, ρ M is the density of the tunnel physical model;

[0039] Stress scale λ σ The calculation formula is as follows: λ σ =λγ λ h (12)

[0040] Where λ h It is a similar scale for the tunnel depth;

[0041] Preset stress value σ 10 , σ 20 and σ 30 The calculation formula is as follows: σ0=γ P h+q g (13) σ 20 =k1σ 10 (15) σ 30 =k2σ 10 (16)

[0042] Where σ0 is the tunnel ground stress; q g is the tectonic stress; k1 is the lateral pressure coefficient along the tunnel axis; k2 is the lateral pressure coefficient perpendicular to the tunnel axis;

[0043] b. The preset geostress value of the tunnel physical model must also meet the material failure condition: establish a tunnel numerical model and apply the preset geostress value σ at the model boundary 10 , σ 20 and σ 30 , and arrange monitoring points around the tunnel to simulate tunnel excavation, save the stress changes recorded by the monitoring points during the excavation process, and save the stress changes recorded by the monitoring points at the corresponding positions of the excavation site, and convert the on-site stress data into similar stress through similarity theory. The calculation method is as follows:

[0044] Where σ i is the similarity transformation stress of the ith monitoring point, σ iP is the stress recorded at the i-th monitoring point on site;

[0045] By comparing the stress changes recorded by the numerical simulation with the stress changes after similar transformation on site, the preset ground stress value of the tunnel physical model is adjusted until the stress changes recorded by the numerical simulation are consistent with the stress changes after similar transformation on site;

[0046] The maximum concentrated stress σ of the tunnel under biaxial compression conditions of the tunnel physical model fj The calculation formula is as follows: σ fj =3σ 1j -σ 2j (18)

[0047] Where σ 1j and σ 2j are the maximum principal stress and intermediate principal stress of the tunnel numerical model unit;

[0048] In order to realize the destruction simulation of the tunnel physical model, it is necessary to set up dangerous characteristic monitoring points on the tunnel numerical model. The stress value of the dangerous characteristic monitoring point must meet the yield failure condition of the tunnel numerical model. Substitute the stress of the dangerous characteristic monitoring point into the yield function When the yield function f>0, the yield failure condition is met; according to the three-dimensional strength criterion, the yield function of the tunnel physical model is as follows:

[0049] Where p is the mean stress, and are material parameters, c and are cohesion and internal friction angle respectively;

[0050] Step 7: During the loading process, the acoustic, optical, and thermal borehole monitor is dragged simultaneously to obtain the damage evolution from the surface to the deep layer of the surrounding rock during the loading process, and the damage of the tunnel physical model is observed through the 360° miniature panoramic high-definition and thermal imaging camera installed in the observation loading pad. When the tunnel physical model is completely destroyed, it is immediately unloaded and the experiment ends;

[0051] Step 8: Save the test data recorded by the acoustic emission device, as well as the data of observation equipment such as the 360° miniature panoramic high-definition and thermal imaging camera, multi-point deformation meter, acoustic, optical, thermal drilling monitor, etc.;

[0052] Step 9: Analyze the test results and conduct research on the disturbance and failure process of the tunnel under true three-dimensional stress, the evolution process of deformation and fracture from the surface to the deep of the surrounding rock during loading, and the mechanism.

[0053] The beneficial effects of the present invention are mainly manifested in:

[0054] 1. The present invention can adapt to the dynamic disturbance loading test of complex tunnel physical models under true triaxial stress field, can well simulate the stress state during tunnel excavation in deep rock engineering, and provides a good means for exploring the fracture evolution process and mechanism of tunnel surrounding rock under true three-dimensional stress conditions.

[0055] 2. The present invention is provided with a loading observation pad that can adapt to different hole shapes and angles, which provides convenience for the study of true three-dimensional stress and tunnel surrounding rock failure mechanism under different spatial relationships of tunnels with different hole shapes. At the same time, the device is easy to install and will not have loading pores with the physical model. It can effectively avoid stress concentration during the loading test and improve the accuracy of the test results.

[0056] 3. The present invention can install observation and recording equipment such as acoustic emission, light, thermal imaging, and piezoelectric sensors, so that the destruction evolution process of the tunnel surrounding rock can be observed intuitively, and the deformation and fracture uncontrolled evolution process of the tunnel surrounding rock from the free surface to the deep can be recorded, and the internal fracture situation can be effectively detected.

[0057] 4. Based on the principle that the maximum deflection of the loading plate during loading is controlled by the bending stiffness, the present invention proposes a calculation index for the design of the loading plate thickness, thereby ensuring the safety and stability of the tunnel physical model loading device. At the same time, the present invention determines the three-dimensional loading stress based on the similarity theory and the three-dimensional strength criterion, ensuring that the destruction evolution process of the tunnel physical model is consistent with the actual situation on site. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is a structural diagram of a visualization test device for a complex tunnel physical model under true three-dimensional stress according to the present invention (top view);

[0059] Figure 2 It is a structural schematic diagram of a visualization test device for a complex tunnel physical model under true three-dimensional stress of the present invention (looking up);

[0060] Figure 3 This is an axonometric diagram of a visualization test device for a complex tunnel physical model under true three-dimensional stress according to the present invention;

[0061] Figure 4 A cross-sectional view of a visualization test device for a complex tunnel physical model under true three-dimensional stress according to the present invention;

[0062] Figure 5 It is an exploded view of a visualization test device for a complex tunnel physical model under true three-dimensional stress according to the present invention;

[0063] Figure 6 This is a front view of a loading pad observed by a visualization test device for a complex tunnel physical model under true three-dimensional stress according to the present invention;

[0064] Figure 7 This is a back view of a loading pad observed by a visualization test device for a complex tunnel physical model under true three-dimensional stress according to the present invention;

[0065] Figure 8 The front plate diagram of the complex tunnel physical model visualization test device under true three-dimensional stress of the present invention is loaded;

[0066] Fig. 9 This is a loaded plate diagram of the complex tunnel physical model visualization test device under true three-dimensional stress of the present invention;

[0067] Fig.10 The left plate diagram is loaded for the visualization test device of the complex tunnel physical model under true three-dimensional stress of the present invention;

[0068] Fig.11 The right panel diagram is loaded for the visualization test device of the complex tunnel physical model under true three-dimensional stress of the present invention;

[0069] Fig.12 Loading a top plate diagram for the visualization test device of the complex tunnel physical model under true three-dimensional stress of the present invention;

[0070] Fig.13 A bottom plate map is loaded for the visualization test device of the complex tunnel physical model under true three-dimensional stress of the present invention;

[0071] Fig.14 This is a physical model diagram of a complex tunnel under true three-dimensional stress of the present invention (top view);

[0072] Fig.15 This is a physical model diagram of a complex tunnel under true three-dimensional stress according to the present invention (looking up);

[0073] Fig.16 It is the stress path diagram of true triaxial tunnel physical model test;

[0074] Fig.17 It is the stress-time curve of the physical model of the city gate tunnel (90°) during the true triaxial static and dynamic combined stress loading process;

[0075] Fig.18 This is the evolution diagram of acoustic emission activity of the physical model of a city gate tunnel (90°) during true triaxial static and dynamic combined stress loading;

[0076] Fig.19 This is a diagram of the rockburst destruction incubation process of a tunnel in the shape of a city gate (90°);

[0077] Fig. 20 Equivalent homogeneous plate force diagram for loading top plate (dynamic disturbance rod is set);

[0078] Fig.21 This is the equivalent simplified calculation model diagram for loading the top plate (setting the dynamic disturbance rod);

[0079] Fig. 22 The structural force diagram of the loaded top plate (with a dynamic disturbance rod);

[0080] Fig.23 It is the force diagram of the equivalent homogeneous plate of the loaded top plate (without the dynamic disturbance rod);

[0081] Fig.24 This is the equivalent simplified calculation model diagram of the loaded top plate (without the dynamic disturbance rod);

[0082] Fig.25 This is a simplified diagram of the structural force of the loaded top plate (without the dynamic disturbance rod);

[0083] In the figure: 1-loading top plate, 101-dynamic disturbance hole, 102-dynamic disturbance rod, 103-loading top plate observation hole, 2-loading right plate, 201-loading right plate guide hole, 202-loading right plate observation hole, 3-loading front plate, 301-loading front plate acoustic emission probe installation hole, 302-loading front plate tunnel observation hole, 303-loading front plate guide hole, 4-observation loading pad, 401-hollow rotating cylinder, 401-1-gate-shaped hollow rotating cylinder, 401-2-horseshoe-shaped hollow rotating cylinder Column, 401-3-circular hollow rotating cylinder, 402-angle fixing bolt, 5-hanging ear connector, 501-guide rod, 6-loading rear plate, 601-loading rear plate acoustic emission probe mounting hole, 7-loading left plate, 701-loading left plate observation hole, 8-loading bottom plate, 801-loading bottom plate observation hole, 9-tunnel physical model, 901-tunnel physical model observation hole, 10-multi-point deformation meter, 11-acoustic, optical, thermal drilling monitor, 12-360° miniature panoramic high-definition and thermal imaging function camera. DETAILED DESCRIPTION

[0084] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0085] like Figures 1 to 25As shown, a visualization test device for a complex tunnel physical model under true three-dimensional stress comprises a loading top plate with a dynamic disturbance rod 102 and an observation hole 103, a hook connector 5 that can realize linear free movement of the device side plate during the loading test, a loading front plate with an acoustic emission probe mounting hole and an observation hole 302 adapted to tunnels of different shapes and angles, a loading rear plate 6 with an acoustic emission probe mounting hole 601, an observation loading pad 4 for mounting optical and thermal imaging observation instruments, a loading left plate 7 with an acoustic, optical, and thermal drilling monitor mounting observation hole, a loading right plate 2, and a loading bottom plate 8; the loading top plate 1 is a rectangular parallelepiped as a whole, and is placed at the top of the entire device, with a dynamic disturbance rod 102 and an observation hole 103 adapted to the drilling hole 103, a loading rear plate 6 with an acoustic emission probe mounting hole 601, and a loading rear plate 6 with an acoustic emission probe mounting hole 601, and a loading rear plate 6 with an observation hole 601 adapted to the drilling hole 103; the loading top plate 1 is a rectangular parallelepiped as a whole, and is placed at the top of the entire device, and a dynamic disturbance rod 102 is placed at the top of the loading top plate 1 ... A hole 101 of a disturbance applying rod is provided, a dynamic disturbance rod 102 is arranged in the hole 101, a loading top plate 1 is connected with a loading right plate 2 and a loading front plate 3 through the loading plate linear free moving ear connector 5, so as to form a three-way six-sided tunnel loading cavity, a tunnel physical model 9 is placed in the loading cavity, and a radial through-length observation hole 901 is arranged in the tunnel physical model 9 along the cross section and the axis, a multi-point displacement meter 10 and an acoustic, optical, and thermal drilling monitor 11 are arranged in the observation hole 901; the acoustic, optical, and thermal drilling monitor 11 has a built-in ultrasonic monitoring device, which can measure the wave velocity of surrounding rock failure on the drilling path, and has a built-in 360° miniature panoramic high-definition camera with thermal imaging function, along the The monitor is pulled from the free surface of the tunnel to the deep surrounding rock by drilling, and the fracture of the surrounding rock of the borehole is scanned and recorded. At the same time, the thermal imaging spectrum of the surrounding rock fracture is obtained. The built-in piezoelectric sensor can obtain the damage position and damage of the surrounding rock through the stress wave attenuation effect on the piezoelectric sensor when the surrounding rock is damaged; the ear connector 5 is installed on the side wall of the loading top plate 1 by screws, and each ear is provided with a guide rod 501 and a guide rod linear movement guide hole 201 and 303. The guide rod 501 is fixed to the loading right plate 2 and the loading front plate 3 to constrain the horizontal displacement of the side plate during loading and assist in the installation and fixation of each loading plate; the loading front plate 3 is provided with a A hollow rotating cylinder 401 runs through the entire loading front plate 3, the hollow rotating cylinder 401 is provided with a scale dial for aligning the angle and an angle fixing bolt 402, and an acoustic emission probe mounting hole 301 is attached to the loading front plate 3; the loading rear plate 6 has the same shape and size as the loading front plate 3, and is also provided with an acoustic emission probe mounting hole 601, which is directly placed on the loading bottom plate 8 and is tightly attached to the model; the observation loading pad 4 is connected to the loading front plate 3 by bolts, the hollow rotating cylinder 401 runs through the entire observation loading pad 4, and is provided with a scale dial for aligning the angle, and a 360° miniature panoramic high-definition and thermal imaging function camera 12 is placed on the observation loading pad.

[0086] The loading left plate 7 has the same shape and size as the loading right plate 2, and is directly placed on the loading bottom plate 8 and closely attached to the model. The loading left plate 7 and the loading right plate 2 are provided with observation holes 701 and 202 for installing an acoustic, optical, and thermal drilling monitor, so as to drill through an observation hole 901 on the tunnel physical model 9, and a multi-point deformation meter 10 and an acoustic, optical, and thermal drilling monitor 11 are installed inside the observation hole. A guide hole 201 connected to a guide rod 501 is provided on the right loading plate 2; the loading bottom plate 8 has the same shape and size as the loading top plate 1, and is directly overlapped with the lateral loading plate, and is also provided with an observation hole 801 for installing an acoustic, optical, and thermal drilling monitor;

[0087] The thickness of the loading top plate 1 is determined as follows:

[0088] Simplify the loading top plate 1 into a homogeneous flat plate of the same size as the loading top plate 1 (see Fig. 20 , Fig.23 As shown), the material coefficient of the loading top plate 1 is k=0.12, the side length of the loading top plate 1 is a=270 mm, the preset thickness of the loading top plate 1 is h=20 mm, the Poisson's ratio of the loading top plate 1 is v=0.30, the elastic modulus of the loading top plate 1 is E=210 GPa, the shear modulus of the loading top plate 1 is G=80.77 GPa, the diameter of the loading area on the loading top plate 1 is d=150 mm, the stress value σ0=80 MPa on the boundary of the tunnel physical model 9, the edge length a0=250 mm of the tunnel physical model 9, the diameter d0=50 mm of the hole 101, and the bending stiffness D of the loading top plate 1 is calculated as follows:

[0089] When the dynamic disturbance rod 102 is arranged in the hole 101 (see Fig. 20 As shown in Figure 1), the calculation formula of the load p0 applied to the loading top plate 1 on the tunnel physical model 9 is as follows: p0=σ0a0 2 =80×250 2 =5000000N=5000kN(2)

[0090] The loading top plate 1 can be split into an equivalent simplified calculation model with a size 1 / 4 of the prototype (see Fig.21 The load acting on the equivalent simplified calculation model The load p acting on the equivalent simplified calculation model 01 Transformed into radially distributed linear load q0 (see Fig. 22 The calculation formula is as follows:

[0091] Where x a is a dimensionless variable;

[0092] The radially distributed line load q0 acts on the radial unit of the top plate 1. The moment of inertia of the radial unit of the top plate 1 is I0 = 8.73 × 10 -10 m 4 ; The reaction force of the tunnel physical model 9 on the loading top plate 1 is p1=p0=5000kN;

[0093] The calculation formula for the deflection w of the loaded top plate 1 is as follows:

[0094] Where α1 is the constraint coefficient of the radial unit of the top plate 1, α1 = 1.92 × 10 -15 ; Iterative calculation shows that the position with the maximum deflection of the loaded top plate 1 is the corner point M(0,0) of the loaded top plate 1, and the maximum deflection of the loaded top plate 1 is w=1.48×10 -5 m = 0.0148 mm;

[0095] When the dynamic disturbance rod 102 is not provided in the hole 101 (see Fig.23 As shown in Figure 1, the calculation formula of the load p2 applied to the loading top plate 1 on the tunnel physical model 9 is as follows:

[0096] The loading top plate 1 can be split into an equivalent simplified calculation model with a size 1 / 4 of the prototype (see Fig.24 The load acting on the equivalent simplified calculation model The load p acting on the equivalent simplified calculation model 21 Transformed into radially distributed linear load q2 (see Fig.25 The calculation formula is as follows:

[0097] The reaction force of the tunnel physical model 9 on the loaded top plate 1 is p3=p2=4842.92 kN;

[0098] The calculation formula for the deflection w of the loaded top plate 1 is as follows:

[0099] Iterative calculation shows that the position with the maximum deflection of the loaded top plate 1 is the corner point M(0,0) of the loaded top plate 1, and the maximum deflection of the loaded top plate 1 is w=1.88×10 -5 m = 0.0188 mm;

[0100] In summary, the maximum deflection of the loaded top plate 1 w<0.02mm, indicating that the thickness of the loaded top plate 1 h=20mm meets the requirements;

[0101] In this embodiment:

[0102] Take the visualization test method of complex tunnel physical model under true three-dimensional stress of a physical model with a size of 250mm×250mm×250mm, a tunnel profile of a city gate, and a bottom plate at a 90° angle to the tunnel horizontal line as an example;

[0103] A visualization test method for a complex tunnel physical model under true three-dimensional stress, comprising the following steps:

[0104] Step 1: After determining the direction of the tunnel axis, place the tunnel physical model 9 on the loading base plate 8, and align the two sides of the tunnel physical model 9 with the device base plate 8;

[0105] Step 2: Place the loading top plate 1 above the tunnel physical model 9, and then align the two sides of the loading top plate 1 without the ear connector 5 with the edges of the tunnel physical model 9;

[0106] Step 3: Install the loading front plate 3 and the loading right plate 2 together with the loading top plate 1 through the hanging ear connector 5 in sequence, and install the guide rod 501 on the hanging ear connector 5 into the corresponding guide holes 201 and 303 on the loading plate, so that the loading front plate 3 and the loading right plate 2 are both in close contact with the physical model 9 and can move horizontally;

[0107] Step 4: Place the loading rear plate 6 and the loading left plate 7 on the reserved edge of the loading bottom plate 8 in sequence, and make the loading rear plate 6 and the loading left plate 7 close to the physical model 9;

[0108] Step 5: Install the observation loading pad 4 to the loading front plate 3 by bolts, rotate the hollow rotating cylinder 401 on the observation loading pad 4 that is the same shape as the tunnel to the same angle as the tunnel, fix the hollow rotating cylinder by the angle fixing bolt 402, and then install the 360° miniature panoramic high-definition and thermal imaging function camera 12 in the observation loading pad 4, drill preset observation holes 901 at the observation holes of the loading left plate 7, the loading right plate 2, the loading top plate 1, and the loading bottom plate 8, install the multi-point deformation meter 10 at a specific position along the surface to the deep layer of the observation hole 901, and set the acoustic, optical, and thermal drilling monitor 11 in the observation hole 901, and then correctly place the installed loading device in the loading area of ​​the true triaxial loading tester, and turn on the acoustic emission and optical, thermal imaging and other observation and recording equipment;

[0109] Step 6: Operate the true triaxial loading test machine to simulate the ground stress redistribution and dynamic disturbance stress path: Load the tunnel physical model 9 in three directions at a rate of 0.2 MPa / s to the preset stress value, where the preset stress value is set as the maximum principal stress σ 10 =30MPa, intermediate principal stress σ 20 =15MPa, parallel to the tunnel axis; minimum horizontal principal stress σ 30=10MPa, perpendicular to the tunnel axis, when σ 20 and σ 30 After reaching the preset stress value, maintain σ 20 and σ 30 Constant, when σ 10 After loading to 30 MPa, the model was kept for 1 minute to simulate the recovery and redistribution of the internal stress of the tunnel physical model 9. Then, a sine wave disturbance with an amplitude of 0.75 MPa and a frequency of 0.5 Hz was performed for 100 cycles. After the disturbance, the σ was increased by 3 MPa. 10 Perturb in the same way, repeat the cycle;

[0110] The preset stress value σ 10 , σ 20 and σ 30 According to the load similarity theory and material failure conditions, the specific calculation method is as follows:

[0111] a. According to the engineering tunnel design data, the cross-sectional area S of the prototype tunnel P =19.635m 2 The cross-sectional area S of the tunnel physical model 9 of this embodiment is M =1.9635×10 -3 m 2 , calculate the equivalent diameter d of the prototype tunnel P , the equivalent diameter d of the tunnel physical model M , the calculation formula is as follows:

[0112] The physical model of the tunnel 9 and the prototype should maintain similar geometric shapes and dimensions, and the corresponding angles should be equal, that is, any corresponding linear length of the prototype and the model should maintain a certain proportional relationship, and the scale of the prototype and the model should be expressed by λ. The geometric similarity scale λ L The calculation formula is as follows:

[0113] Similarity scale of original rock density γ The calculation formula is as follows:

[0114] Density similarity scale λ ρ = 2.5, when calculating the tunnel in-situ stress, the buried depth of the tunnel physical model 9 is the same as that of the prototype tunnel, then the tunnel buried depth similarity scale λ h =1, stress ratio λ σ The calculation formula is as follows: λ σ =λ γλ h =2.5×1=2.5(12)

[0115] Preset stress value σ 10 , σ 20 and σ 30 The calculation formula is as follows: σ0=γ P h+q g =27500×2650×10 -6 +2.1=75MPa(13)

[0116] Where σ0 is the tunnel ground stress; tectonic stress q g =2.12MPa; lateral pressure coefficient along the tunnel axis Lateral pressure coefficient in the direction perpendicular to the tunnel axis

[0117] b. The preset geostress value of the tunnel physical model 9 must also meet the requirements of stress concentration: establish a tunnel numerical model and apply a preset geostress value σ at the model boundary 10 , σ 20 and σ 30 , and arrange monitoring points around the tunnel to simulate tunnel excavation, save the stress changes recorded by the monitoring points during the excavation process, and save the stress changes recorded by the monitoring points at the corresponding positions of the excavation site, and convert the on-site stress data into similar stress through similarity theory. The calculation method is as follows:

[0118] Where σ i is the similarity transformation stress of the ith monitoring point, σ iP is the stress recorded at the i-th monitoring point on site;

[0119] By comparing the stress changes recorded by the numerical simulation with the stress changes after similar transformation on site, the preset ground stress value of the tunnel physical model is adjusted until the stress changes recorded by the numerical simulation are consistent with the stress changes after similar transformation on site;

[0120] Tunnel physical model 9 Under biaxial compression conditions, the maximum concentrated stress σ fj The calculation formula is as follows: σ fj =3σ 1j -σ 2j (18)

[0121] Where σ1j and σ 2j are the maximum principal stress and intermediate principal stress of the tunnel numerical model unit;

[0122] In order to realize the destruction simulation of the tunnel physical model 9, it is necessary to set up dangerous characteristic monitoring points on the tunnel numerical model. The stress value of the dangerous characteristic monitoring point must meet the yield failure condition of the tunnel numerical model. Substitute the stress of the dangerous characteristic monitoring point into the yield function When the yield function f>0, the yield failure condition is met; according to the three-dimensional strength criterion, the yield function of the tunnel physical model 9 is as follows:

[0123] Where p is the mean stress, and are material parameters, c and are cohesion and internal friction angle respectively;

[0124] Analyzing the numerical simulation results, the dangerous characteristic monitoring points all meet the yield failure conditions, and the preset stress value σ 10 , σ 20 and σ 30 The value is σ 10 =30MPa,σ 20 =15MPa,σ 30 =10MPa;

[0125] Step 7: Observe the damage of the tunnel physical model 9 by using the 360° miniature panoramic high-definition and thermal imaging camera 12 installed in the observation loading pad 4. When the tunnel physical model 9 is completely damaged, unload it immediately and the experiment ends.

[0126] Step 8: Save the test data recorded by the acoustic emission device, as well as the data of observation equipment such as the 360° miniature panoramic high-definition and thermal imaging camera 12, the multi-point deformation meter 10, the acoustic, optical, thermal drilling monitor 11, etc.;

[0127] Step 9: Analyze the test results and conduct research on the disturbance and failure process of the tunnel under true three-dimensional stress, the evolution process of deformation and fracture from the surface to the deep of the surrounding rock during loading, and the mechanism.

[0128] Matters not covered by the present invention are known technologies.

[0129] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A visualization test device for complex tunnel physical models under true three-dimensional stress, characterized by It includes a loading top plate with a power disturbance rod and an observation hole, a loading front plate with an acoustic emission probe mounting hole and a loading observation hole adapted to tunnels of different hole shapes and angles, a loading rear plate with an acoustic emission probe mounting hole, an observation loading pad capable of installing optical and thermal imaging observation instruments, a loading left plate and a loading right plate with observation holes capable of installing acoustic, photoelectric and thermal borehole monitors, a loading bottom plate with observation holes, and a loading plate linear free-moving hanging ear connector; the linear free-moving hanging ear connector is installed on the side wall of the loading top plate through a screw, each hanging ear is provided with a guide rod and a guide rod linear movement guide hole, and the guide rod is fixed to the loading right plate and the loading front plate; the loading rear plate and the loading left plate are placed on the loading bottom plate, the loading top plate, the loading right plate and the loading front plate are connected through the loading plate linear free-moving hanging ear connector to form a three-way six-sided tunnel loading cavity, a tunnel physical model is placed in the loading cavity, the tunnel physical model is arranged with radial through-length observation holes along the cross section and the axis, and a multi-point displacement meter and an acoustic, photoelectric and thermal borehole monitor are arranged in the observation hole; The loading front plate is provided with a hollow rotating cylinder adapted to tunnels of different shapes and angles. The hollow rotating cylinder runs through the entire loading front plate. The hollow rotating cylinder is provided with angle alignment scale lines and angle fixing bolts. An observation loading pad is provided at the front of the loading front plate, and a 360° miniature panoramic high-definition camera with thermal imaging function is placed on the observation loading pad.

2. A visualization test device for complex tunnel physical model under true three-dimensional stress according to claim 1, characterized in that: The loading top plate is a rectangular parallelepiped, which is placed at the top of the whole device. A hole is arranged at the center of the loading top plate to accommodate the power disturbance application rod. The power disturbance application rod is arranged in the hole. Two linear free-moving hanging ear connectors connected to the right loading plate and the front loading plate are arranged on the two adjacent side surfaces. The loading bottom plate is placed at the bottom of the whole device, and is also provided with an observation hole for installing an acoustic, optical, thermal drilling monitor. The thickness of the loading top plate is determined as follows: The loading top plate is simplified into a homogeneous flat plate of the same size as the loading top plate, and the maximum deflection of the loading top plate when subjected to the maximum loading load is calculated. When a dynamic disturbance rod is set in the hole, the calculation method is as follows: p0=σ0a 2 (2) Where D is the bending stiffness of the loaded top plate, h is the thickness of the loaded top plate, v is the Poisson's ratio of the loaded top plate, E is the elastic modulus of the loaded top plate, p0 is the maximum load applied on the loaded top plate, σ0 is the stress value on the boundary of the tunnel physical model, and a0 is the edge length of the tunnel physical model; The loaded top plate can be split into an equivalent simplified calculation model that is 1 / 4 the size of the prototype. The load acting on the equivalent simplified calculation model The load p acting on the equivalent simplified calculation model 01 Converted into radially distributed linear load q0, the calculation formula is as follows: Where x a is a dimensionless variable; The calculation formula for the deflection w of the loaded top plate is as follows: Where w(x,y) is the deflection of the loaded top plate, α1 is the constraint coefficient of the radial unit of the loaded top plate, G is the shear modulus of the loaded top plate, I0 is the moment of inertia of the radial unit of the loaded top plate, d is the diameter of the loading area on the loaded top plate, k is the material coefficient of the loaded top plate, p1 is the reaction force of the tunnel physical model on the loaded top plate, and a is the side length of the loaded top plate; When no dynamic disturbance rod is set in the hole, the calculation formula of the load p2 applied on the loading top plate on the tunnel physical model is as follows: Where d0 is the diameter of the hole in the loading top plate; The loaded top plate can be split into an equivalent simplified calculation model that is 1 / 4 the size of the prototype. The load acting on the equivalent simplified calculation model The load p acting on the equivalent simplified calculation model 21 Converted into radially distributed linear load q2, the calculation formula is as follows: The calculation formula for the deflection w of the loaded top plate is as follows: Where p3 is the reaction force of the tunnel physical model on the loaded top plate; The thickness h of the loading top plate needs to ensure that the maximum deflection w of the loading top plate satisfies w<0.02mm.

3. A visualization test device for complex tunnel physical model under true three-dimensional stress according to claim 1, characterized in that: The acoustic, optical, thermal drilling monitor has a built-in ultrasonic monitoring device, a 360° miniature panoramic high-definition camera with thermal imaging function, and a piezoelectric sensor.

4. A visualization test device for complex tunnel physical model under true three-dimensional stress according to claim 1, characterized in that: The rear loading plate has the same shape and size as the front loading plate and is also provided with an acoustic emission probe mounting hole. The rear loading plate is directly placed on the loading bottom plate and is in close contact with the model.

5. A visualization test device for complex tunnel physical model under true three-dimensional stress according to claim 1, characterized in that: The left loading plate and the right loading plate have the same shape and size, are placed on the loading bottom plate and are close to the physical model, and are provided with observation holes corresponding to the radial through-length observation holes of the tunnel physical model.

6. The test method of a visualization test device for complex tunnel physical model under true three-dimensional stress according to claim 1 is characterized in that: The following steps are involved: Step 1: After determining the direction of the tunnel axis, place the tunnel physical model on the loading base plate and align the two sides of the tunnel physical model with the device base plate; Step 2: Place the loading top plate on the tunnel physical model, and then align the two sides of the loading top plate without ear connectors with the edges of the tunnel physical model; Step 3: Install the front loading plate and the right loading plate together with the top loading plate through the ear connectors in sequence, and install the guide rods on the ear connectors into the corresponding guide holes on the loading plate, so that the front loading plate and the right loading plate are both in close contact with the physical model and can move horizontally; Step 4: Place the rear loading plate and the left loading plate on the reserved edge of the bottom loading plate in sequence, and make the rear loading plate and the left loading plate close to the physical model; Step 5: Install the observation loading pad to the loading front plate through bolts, rotate the hollow rotating cylinder with the same shape as the tunnel on the observation loading pad to the same angle as the tunnel, fix the hollow rotating cylinder with the angle fixing bolts, and then install the 360° miniature panoramic high-definition and thermal imaging camera in the observation loading pad. Drill preset observation holes at the observation holes of the loading left plate, loading right plate, loading top plate, and loading bottom plate. Install the multi-point deformation meter at a specific position from the surface to the deep layer of the observation hole, and set an acoustic, optical, and thermal drilling monitor in the observation hole. Then correctly place the installed loading device in the loading area of ​​the true triaxial loading tester, and turn on the acoustic emission and optical, thermal imaging and other observation and recording equipment; Step 6: Operate the true triaxial loading test machine to simulate the stress path of the three-dimensional ground stress redistribution and blasting disturbance coupling: Load the tunnel physical model in three directions at the same loading rate v σ Apply static load to the preset stress value, when σ 20 and σ 30 After reaching the preset stress value, maintain σ 20 and σ 30 Keep constant and continue to improve σ 10 to the preset value and maintain it for a period of time t0 and then start to m , the frequency f is used for a sinusoidal perturbation with a period of T, and after the perturbation ends, the gradient σ t Increase σ 10 , apply dynamic disturbance in the same way as above, and repeat this cycle; the preset stress value σ 10 , σ 20 and σ 30 According to the load similarity theory and material failure conditions, the specific calculation method is as follows: a. The physical model of the tunnel should maintain similar geometric shapes and dimensions to the prototype, and the corresponding angles should be equal, that is, any corresponding linear length of the prototype and the model should maintain a certain proportional relationship, and the scale of the prototype and the model should be expressed as λ. The geometric similarity scale λ L The calculation formula is as follows: Where d P is the equivalent diameter of the prototype tunnel, d M is the equivalent diameter of the tunnel physical model; the equivalent diameter is the diameter of each type of tunnel when it is converted into a circular tunnel of equal area. The equivalent diameter of the prototype tunnel is d P , the equivalent diameter d of the tunnel physical model M The calculation formula is as follows: Where S P is the cross-sectional area of ​​the prototype tunnel, S M is the cross-sectional area of ​​the tunnel of the tunnel physical model; Severity similarity ratio λ γ The calculation formula is as follows: Where γ P is the original rock density, γ M is the weight of the tunnel physical model, λ γ is the original rock density, ρ M is the density of the tunnel physical model; Stress scale λ σ The calculation formula is as follows: l σ =λ γ l h (12) Where λ h It is a similar scale for the tunnel depth; Preset stress value σ 10 , σ 20 and σ 30 The calculation formula is as follows: σ0=γ P h+q g (13) s 20 =k1σ 10 (15) s 30 =k2σ 10 (16) Where σ0 is the tunnel ground stress; q g is the tectonic stress; k1 is the lateral pressure coefficient along the tunnel axis; k2 is the lateral pressure coefficient perpendicular to the tunnel axis; b. The preset geostress value of the tunnel physical model must also meet the material failure condition: establish a tunnel numerical model and apply the preset geostress value σ at the model boundary 10 , σ 20 and σ 30 , and arrange monitoring points around the tunnel to simulate tunnel excavation, save the stress changes recorded by the monitoring points during the excavation process, and save the stress changes recorded by the monitoring points at the corresponding positions of the excavation site, and convert the on-site stress data into similar stress through similarity theory. The calculation method is as follows: Where σ i is the similarity transformation stress of the ith monitoring point, σ iP is the stress recorded at the i-th monitoring point on site; By comparing the stress changes recorded by the numerical simulation with the stress changes after similar transformation on site, the preset ground stress value of the tunnel physical model is adjusted until the stress changes recorded by the numerical simulation are consistent with the stress changes after similar transformation on site; The maximum concentrated stress σ of the tunnel under biaxial compression conditions of the tunnel physical model fj The calculation formula is as follows: s fj =3σ 1j -s 2j (18) Where σ 1j and σ 2j are the maximum principal stress and intermediate principal stress of the tunnel numerical model unit; Dangerous feature monitoring points are set on the tunnel numerical model. The stress value of the dangerous feature monitoring point must meet the yield failure condition of the tunnel numerical model. The stress of the dangerous feature monitoring point is substituted into the yield function. When the yield function f>0, the yield failure condition is met; according to the three-dimensional strength criterion, the yield function of the tunnel physical model is as follows: Where p is the mean stress, and are material parameters, c and are cohesion and internal friction angle respectively; Step 7: During the loading process, the acoustic, optical, and thermal borehole monitor is dragged simultaneously to obtain the damage evolution from the surface to the deep layer of the surrounding rock during the loading process, and the damage of the tunnel physical model is observed through the 360° miniature panoramic high-definition and thermal imaging camera installed in the observation loading pad. When the tunnel physical model is completely destroyed, it is immediately unloaded and the experiment ends; Step 8: Save the test data recorded by the acoustic emission device, as well as the data of observation equipment such as the 360° miniature panoramic high-definition and thermal imaging camera, multi-point deformation meter, acoustic, optical, thermal drilling monitor, etc.; Step 9: Analyze the test results and conduct research on the disturbance and failure process of the tunnel under true three-dimensional stress, the evolution process of deformation and fracture from the surface to the deep of the surrounding rock during loading, and the mechanism.

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