Visual detection method for simulating interaction between separation layer of composite layered rock mass and anchor rod

Abstract

The invention discloses a visual detection method for simulating interaction between a separation layer of a composite layered rock mass and an anchor rod, and belongs to the field of coal mine composite roof roadway support engineering. The visual detection method comprises the following steps: manufacturing a composite layered transparent rock mass with a separation layer structure, arranging the anchor rod in the composite layered transparent rock mass and then carrying out visual loading detection; loading the composite layered transparent rock mass so as to simulate the deformation condition of a composite layered roadway roof which is internally provided with different anchor rods for anchoring under the action of different stresses, and acquiring position change images of a speckle surface a and a speckle surface b in the composite layered transparent rock mass in the loading process by utilizing a video acquisition system; by analyzing the relative position change of speckles formed by the speckle surface a and the speckle surface b at different moments in the loading test process, the change information of the deformation separation layer of the composite layered transparent rock mass along with the axial force of the anchor rod is obtained, the axial force information of the anchor rod is calculated, and the research on the interaction between the separation layer of the composite layered rock mass and the anchor rod is realized. The method is simple in step and good in use effect.

Description

Technical Field

[0001] The invention belongs to the field of coal mine composite roof roadway support engineering, and in particular is a visual detection method for simulating the interaction between composite layered rock delamination and anchor rods. Background Art

[0002] For composite roof tunnels, high-strength prestressed anchor rods (cables) are currently widely used for support. However, the surrounding rock around the anchor rod trays in deep composite strata tunnels is weak and brittle. Under the action of high horizontal stress, the composite roof rock layer is very likely to gradually delaminate and break as the roof bends and sinks. The bearing capacity of the anchor layer decreases until it fails, resulting in roof collapse accidents. However, since neither on-site nor existing physical simulation test equipment can achieve "visualization", and existing physical simulation test methods cannot more realistically simulate the surrounding rock stress state of the roof after tunnel excavation, the basic issues such as the time and conditions for composite roof delamination, the changes in the anchoring force (or supporting force) of the anchor rods that control the delamination and sinking of the roof, and especially the mutual influence and constraint relationship between them are difficult to solve.

[0003] The prior art, publication number CN117782811A, discloses an indoor testing method for the stress distribution law of full-length bonded anchor rods in fractured rock masses, relating to the technical field of anchor rod stress testing in geotechnical engineering. This method first uses a similar material model test method to produce rock masses with joints and fractures of varying numbers, positions, lengths, widths, and orientations; then, anchor rods are anchored in the jointed and fractured rock masses to form anchored rock masses; then, uniaxial / biaxial compression tests are performed on the anchored rock masses to simulate the deformation and stress characteristics of the rock masses and anchor rods in situ. As loading continues, the axial stress / strain data of the anchor rods are continuously collected to obtain the stress distribution law of the full-length bonded anchor rods in the fractured rock masses. This method can only obtain stress data through sensors and cannot intuitively observe the internal deformation of the specimen during loading. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, a visualization detection method for simulating the interaction between delamination of composite layered rock and anchor rods is provided. The composite layered rock mass is made of transparent materials, and the entire test process can be visualized in combination with a visualization test device. By arranging a colored speckle surface in the composite layered rock mass as a reference, the internal deformation information of the composite layered transparent rock mass model can be more intuitively observed, and the settlement, bending and delamination changes of the model layered surrounding rock, crack expansion and surrounding rock collapse processes under the action of ground stress can be observed. Strain gauges are pasted on materials similar to anchor rods, and the axial force change information of the anchor rod can be obtained through a strain acquisition instrument.

[0005] The present invention discloses a visual detection method for simulating the interaction between composite layered rock delamination and anchor rods, and the steps are as follows: A transparent thin soft rock layer simulating a soft rock layer and a transparent thick hard rock layer simulating a hard rock layer are respectively produced, wherein the middle of the thin soft rock layer and the transparent thick hard rock layer are both provided with a speckle surface a; A thin soft rock layer is placed below a thick hard rock layer, and the original speckle surface a in the two layers is spliced ​​together. Another speckle surface b is set between the contact surface of the thin soft rock layer and the thick hard rock layer to form a composite layered transparent rock mass with a hard upper layer and a soft lower layer and a weak structural surface. The speckle surface a and the speckle surface b in the composite layered transparent rock mass are perpendicular to each other. An anchor hole required for the test is drilled vertically in the thickness direction of the thin soft rock layer of the composite layered transparent rock mass. A simulated anchor made of a fusible wire is installed in the anchor hole. A strain gauge is provided on the simulated anchor. The strain gauge on the simulated anchor is connected to a computer via a static resistance strain acquisition instrument to obtain the simulated anchor strain data, thereby obtaining the anchor axial force. Assemble a visual loading device on the outside of the composite layered transparent rock mass and then install it on the loading platform. Use the composite layered transparent rock mass to simulate the composite layered roadway roof. Set up a video acquisition system on the side of the visual loading device. A loading platform was used to load the composite layered transparent rock mass to simulate the deformation of the composite layered tunnel roof with different anchors inside under different stresses. A video acquisition system was used to capture the position change images of speckle plane a and speckle plane b in the composite layered transparent rock mass during the loading process. By analyzing the relative position changes of the speckles formed by speckle plane a and speckle plane b at different times during the loading test, information on the change of the deformation and delamination of the composite layered transparent rock mass with the axial force of the anchor was obtained. The strain data of the simulated anchor was obtained by strain gauges, and the axial force information of the anchor was obtained by synchronous calculation, realizing the study of the interaction between the delamination of the composite layered rock mass and the anchor.

[0006] Furthermore, the rock-similar material solution includes silica gel powder with a particle size of 200-300 mesh and clear pore liquid, and the mass ratio of silica gel powder to transparent pore liquid is 0.60:1; among them, the clear pore liquid is a transparent mixed solution composed of No. 15 white oil and n-dodecane, the refractive index of the transparent mixed solution is similar to that of the aggregate, and the mass ratio of No. 15 white oil to n-dodecane is 1.9:1.

[0007] Furthermore, the simulated anchor rod includes a fusible wire as the rod body. The fusible wire is selected based on the theory of similar materials. A locking structure is provided in the tail end of the fusible wire. The locking structure includes a tray and a positioning patch sleeved on the tail of the fusible wire. A compression spring sleeved on the fusible wire is provided between the tray and the positioning patch. A locking buckle for fastening is provided behind the positioning patch. The tray and the positioning patch are square iron sheets with a hole. The hole diameter is consistent with the diameter of the fusible wire. The diameter of the fusible wire is 2 mm. The compression spring has a wire diameter of 0.3 mm, a diameter of 2 mm, and a length of 30 mm. The strain gauge is pasted 6 cm away from the end of the anchor rod to monitor the axial force change information of the anchor rod at the delamination point of the composite layered rock structure surface.

[0008] Furthermore, a light source for an auxiliary video acquisition system is provided on the loading platform side. The video acquisition system collects images so that the mutually perpendicular speckle planes a and b in the composite layered transparent rock mass can be clearly observed and recorded. During the loading process, the video acquisition system can intuitively and clearly monitor the position change information of the speckle planes a and b inside the composite layered rock mass, the deformation and rupture of the composite layered rock mass, and the development of cracks through the visual loading device and the surface of the composite layered rock mass.

[0009] Furthermore, during the loading process: the loading platform is used to load the composite layered rock mass with horizontal and vertical forces, and the stepper motors used to control the horizontal and vertical loading are used to apply loads to the composite layered transparent rock mass at 22.5N / S and 22.5N / S respectively. The loading is stopped when the horizontal load and the vertical load are applied to 0.407MPa. At this time, the ratio of the horizontal load to the vertical load is 1.0; the real-time load changes loaded by the testing machine are collected to obtain the simulated ground stress state information of the composite layered rock mass with the simulated anchor rods.

[0010] Furthermore, speckle surface a is a red speckle surface, and speckle surface b is a purple speckle surface.

[0011] Furthermore, the process of making a transparent thin soft rock layer simulating a weak rock layer and a transparent thick hard rock layer simulating a hard rock layer is as follows: A mixed solution of aggregate and pore liquid with a particle size of 200-300mm is poured into the thin layer mold. After vacuum exhaust, a layer of red aggregate with the same particle size is laid on the first layer of solid-liquid mixture to form a red speckle surface for monitoring the internal deformation of the rock mass. Then, the solid-liquid mixture of the designed height is poured in, and vacuum exhaust is performed again to form a transparent solid-liquid mixture; a high-pressure consolidation instrument is used to apply a consolidation pressure of 10MPa to the solid-liquid mixture in the thin layer mold, and the consolidation is carried out for 24 hours to obtain a transparent thin soft rock layer with a red speckle surface in the middle; the production process of the transparent thick hard rock layer is repeated using a thick layer transparent mold, and the high-pressure consolidation instrument is adjusted to use a consolidation pressure of 20MPa for consolidation for 60 hours to prepare a transparent thick hard rock layer with a red speckle surface in the middle.

[0012] Furthermore, the method for producing a composite layered transparent rock mass with a hard upper and soft lower structure using a transparent thin soft rock layer and a transparent thick hard rock layer is as follows: The prepared transparent thick hard rock layer and transparent thin soft rock layer were demolded and rotated 90° in the direction perpendicular to the positive surface of the rock mass. The transparent thick hard rock layer was vertically superimposed on the transparent thin soft rock layer and the red speckle surfaces of the two were aligned. A layer of purple aggregate was added between the superimposed surfaces and then placed into a structural surface consolidation mold. After consolidation using a consolidation instrument, a composite layered rock mass with a purple speckle surface for monitoring the internal bending, deformation and delamination of the composite layered rock mass was formed. The consolidation instrument was continued to apply a consolidation pressure of 2 MPa to the composite layered rock mass placed in the structural surface consolidation mold. After consolidation for 12 hours, the mold was removed to obtain a composite layered transparent rock mass containing a weak structural surface.

[0013] Furthermore, an image of the composite layered rock mass obtained by the video acquisition system before loading was started was used as a reference image. Two red speckle points were selected from the red speckle surface on the upper and lower sides of the straight line bounded by the purple speckle surface in the reference image as discrete points for monitoring the opening of delamination inside the rock mass. If delamination occurs, the composite rock mass will open on the purple speckle interface, and the two selected red speckles will produce obvious relative displacement. By comparing the relative position changes of the two red speckles at different times during the loading process, as the composite layered transparent rock mass is loaded, the two red speckles undergo obvious relative vertical displacement, indicating that delamination has occurred inside the composite layered rock mass. Analysis of the relative vertical displacement between the two red speckles is the change in delamination inside the composite layered rock mass. Taking the image of the composite layered rock mass before loading is started as the reference image, the bending deformation information inside the thin soft rock layer is obtained by comparing and analyzing the relative position changes of the red speckles in the thin soft rock layer below the purple speckle interface in the composite layered rock mass at different times during the loading process. The bending deformation information inside the thick hard rock layer is obtained by recording and analyzing the position changes of the red speckles in the thick hard rock layer above the purple speckle interface in the composite layered rock mass at different times during the test.

[0014] Furthermore, the video acquisition system has a shooting interval of 1s to ensure that a complete and continuous image of the speckle changes inside the rock mass is obtained through the surface of the composite layered rock mass. In addition, it can intuitively obtain information on the changes in deformation, fracture, and crack development of the composite layered rock mass during the test; the static strain meter continuously monitors and collects the simulated anchor axial strain data, and through stress-strain calculation, the collected anchor axial strain is converted into anchor axial force data, which can obtain information on the changes in anchor axial force with the deformation and delamination of the composite layered rock mass during the experiment.

[0015] Beneficial effects: This method uses a combination of different rock types and different layer thicknesses to form a composite layered transparent rock mass. Compared with traditional homogeneous materials, it can accurately restore the heterogeneity and weak structural surface characteristics of natural composite geological rock masses; the layer thickness, strength and installed simulated anchor arrangement parameters of the composite layered transparent rock mass are adjustable, and different engineering conditions can be simulated; it can realize visualization and accurate acquisition of the entire process of internal deformation and delamination of the composite layered rock mass under the action of ground stress; it can intuitively observe the deformation and rupture of the composite layered rock mass and the entire process of crack development under the action of ground stress; it can accurately obtain the deformation information of the composite layered rock mass and the change information of the anchor axial force. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The figures are photos of the anchor bolt production process for the composite layered transparent rock mass in the embodiment of the present invention; (a) is a photo of the configuration of colored aggregate, (b) is a photo of the sealed mold, (c) is a photo of the layout of the speckle surface in the layered transparent rock mass, (d) is a photo after the second vacuum pumping, (e) is a photo of the installation of the reinforcement rod, (f) is a photo of the pressurized consolidation, (h) is a photo of the bedding surface of the layered transparent rock mass, (i) is a photo of drilling holes and injecting anchoring agent into the layered transparent rock mass, and (j) is a photo of the installation of anchor bolts in the layered transparent rock mass.

[0017] Figure 2 Schematic diagram of the composite layered transparent rock structure in an embodiment of the present invention.

[0018] Figure 3 Schematic diagram of the structure of the simulated anchor rod in an embodiment of the present invention.

[0019] Figure 4 Schematic diagram of the overall structure of a visual loading device with a fixed frame installed in an embodiment of the present invention; Figure 5 Schematic diagram of the decomposed structure of the fixed frame in the embodiment of the present invention, (a) is a schematic diagram of the front reinforcement frame, (b) is a schematic diagram of the rear reinforcement frame, and (c) is a schematic diagram of the bottom reinforcement frame. The deep groove in the middle of the bottom reinforcement frame is a hollow structure.

[0020] Figure 6 This is a schematic diagram of the structure of a visual test device for simulating the interaction between delamination of composite layered rock and anchor rods used in an embodiment of the present invention.

[0021] Figure 7 The graph is a graph showing the evolution of deformation and delamination of a composite layered rock mass and the change rules of the vertical displacement field under load in an embodiment of the present invention.

[0022] Figure 8 Schematic diagram of the deformation evolution process of the composite rock mass and the change law of the vertical displacement field in the embodiment of the present invention; (a) is a photo of the layered transparent rock mass producing a small deformation, (b) is Figure 7The vertical displacement cloud map and displacement vector map of the surrounding rock at point O in the middle, (c) is a photo of the layered transparent rock mass producing delamination and cracks in the bottom rock layer, (d) is Figure 7 The vertical displacement cloud map and displacement vector map of the surrounding rock at point A in the middle, (e) is a photo of the rapid enlargement of the separation layer and the rapid increase in the number of cracks in the layered transparent rock mass, (f) is Figure 7 The vertical displacement cloud map and displacement vector map of the surrounding rock at point C in the middle, (g) is a photo of the overall deformation of the composite rock mass where the cracks in the layered transparent rock mass penetrate into the delamination layer, and (h) is Figure 7 The vertical displacement cloud map and displacement vector map of the surrounding rock at point E in the middle. (i) is a photo of the bottom of the layered transparent rock mass with complete development of rock cracks and broken rock layers. (j) is Figure 7 Vertical displacement cloud map and displacement vector map of surrounding rock at point F.

[0023] In the figure, 1-thick hard rock layer; 2-thin soft rock layer; 3-red speckle surface; 4-purple speckle surface; 5-strain gauge; 6-anchor rod; 7-tray; 8-compression spring; 9-positioning patch; 10-lock; 11-acrylic panel of the box; 12-top pressure plate; 13-front reinforcement frame; 14-rear reinforcement frame; 15-bottom reinforcement frame; 16-left horizontal loading plate; 17-right horizontal loading plate; 18-vertical loading plate; 19-pad; 20-light; 21-digital camera; 22-laptop; 23-strain collector; 24-computer. DETAILED DESCRIPTION

[0024] The present invention will be further described below with reference to the accompanying drawings. The present invention discloses a visualization detection method for simulating the interaction between delamination of a composite layered rock mass and an anchor rod. The method comprises preparing a plurality of layered transparent rock masses with different lithologies and layer thicknesses and containing a horizontal red speckle surface 3 in the middle of the rock mass. A support-similar material is used for anchoring, and a purple auxiliary material is laid on the bedding interface to form a purple speckle surface 4. The composite layered transparent rock mass has a weak joint surface and speckles for monitoring bending, deformation and delamination inside the composite layered rock mass. After the composite layered transparent rock mass is placed in a visualization detection device, it is loaded into a test loading device. A pressure testing machine is used to apply vertical and horizontal loads to the composite layered transparent rock mass, thereby simulating the stress state of the roof after excavation of a deep composite rock stratum tunnel. Compared with traditional similar material models and test devices, the combination of the composite layered transparent rock mass and the visualization detection device can realize visualization of the entire test process of the interaction between delamination of the composite layered rock mass and the anchor rod 6, and can enable the monitoring system to intuitively and clearly monitor the position change information of the speckle surface inside the composite layered rock mass through the loading device and the surface of the composite layered rock mass. By deploying a video acquisition system, a digital camera can be used to visually and clearly monitor the position changes of the internal speckle of the composite layered transparent rock mass under the action of load through the loading device and transparent rock-like materials. The digital photography non-contact measurement system is used to analyze the position changes of the internal speckle of the composite layered transparent rock mass through graphic data and convert them into delamination and deformation data of the composite layered transparent rock mass. Strain gauges are attached to similar materials of anchor rods, and the strain data collected by the strain acquisition instrument can obtain the strain information of the anchor rod. The axial force change information of the anchor rod can be obtained by calculation through the stress-strain formula, thereby achieving the research purpose of simulating the interaction between the delamination deformation of the composite layered rock mass and the anchor rod.

[0025] The specific steps include: firstly, mixing the colored aggregate for making the interface layer, such as Figure 1 As shown in (a), a transparent mixture of aggregate and pore liquid with consistent refractive index is then placed in a high-strength transparent rectangular sealed mold with different thicknesses (or widths) equipped with a base; the mold is placed in a vacuum box, and the air in the transparent mixture in the mold is removed by vacuum negative pressure, as shown in FIG. Figure 1 As shown in (b), colored aggregate is laid on the first layer of solid-liquid mixture to form a red speckled surface 3, as shown in Figure 1 As shown in (c), a layer of transparent mixed solution is then poured in according to the designed height to exhaust the internal air. Figure 1 As shown in (d), the two halves of the container mold and the bolt reinforcement frame are assembled, and the pressure head is placed. After the assembly is completed, they are placed in the high-pressure consolidation instrument. Figure 1 (e) and Figure 1 As shown in (f), by applying different consolidation pressures and consolidation times, layered transparent rock-like materials with different thicknesses (or widths) can be obtained, including a thick hard rock layer 1 and a thin soft rock layer 2.

[0026] According to the actual situation of composite layered rock mass engineering, the consolidated layered transparent rock-like material is rotated 90 degrees in the direction perpendicular to the positive surface of the rock mass and placed. The transparent thick hard rock layer 1 is vertically superimposed on the thin soft rock layer 2 in the order (thick hard rock layer 1 on top and thin soft rock layer 2 on the bottom) to form a composite layered rock mass. The vertical planes of the two vertically superimposed transparent rock-like materials are both a red speckle surface 3, which constitutes a speckle surface for monitoring the internal deformation of the composite layered rock mass. A layer of extremely thin purple aggregate with a particle size of 60-80mm is added between the superimposed surfaces to form a purple speckle surface 4. The superimposed composite layered transparent rock mass is placed in a consolidation mold, as shown in FIG. Figure 1 (h) is shown, and then placed on the consolidation instrument, a small pressure is applied, and after the designed consolidation time is reached, a composite layered rock mass with weak joint surfaces can be obtained, and the speckles of bending, deformation and delamination inside the composite layered rock mass can be observed intuitively and clearly through the rock surface.

[0027] The consolidation mold for layered transparent rock-like materials includes a cubic structure mold formed by bonding four 5mm thick transparent box acrylic panels 4. The mold can be disassembled and has a smooth surface, which is convenient for demoulding. The mold cavity size can be set to a variety of sizes according to actual simulation needs, which are used to consolidate thin layers of soft transparent rock-like materials and thick layers of hard transparent rock-like materials respectively. The mold is provided with a base made of high-strength hot-rolled steel, and the base is provided with a 2mm deep card groove for fixing the four box acrylic panels 4. The top of the mold is provided with a pressure head made of hot-rolled steel. The outside of the mold is provided with a detachable two-piece mold made of hot-rolled steel, an external reinforcement rod and fixing bolts, such as Figure 1 (e) shown.

[0028] The consolidation instrument adopts a hydraulic universal testing machine, such as Figure 1 As shown in (f), pressure is provided by hydraulic transmission. When consolidating the lower soft transparent rock mass, a consolidation pressure of 10 MPa can be applied, and the consolidation time is 24 h; when consolidating the upper hard transparent rock mass, a consolidation pressure of 20 MPa can be applied, and the consolidation time is 60 h; when consolidating the structural surface, a consolidation pressure of 2 MPa can be applied, and the consolidation time is 12 h.

[0029] The structural surface consolidation mold includes a box body composed of two high-strength transparent acrylic plates with a size of 190mm×150mm×20mm as the front and rear panels and two high-strength transparent acrylic plates with a size of 150mm×150mm×20mm as the left and right side panels. Three rows of threaded holes with a diameter of 6mm are arranged 45mm apart between adjacent panels with the horizontal center as the starting point, and bolts are connected through the threaded holes. Figure 1 (h) Figure 1 (h) The left, middle and right diagrams are schematic diagrams of composite layered transparent rock at different angles.

[0030] On the bottom surface of the thin soft rock layer 2 of the consolidated composite layered transparent rock mass, anchor holes are drilled in parallel along the thickness direction according to the actual working conditions and anchoring agents are injected, such as Figure 1 (i) As shown; a simulated anchor rod 6 consisting of a fuse is installed in each anchor rod hole, and a strain gauge 5 is provided on the simulated anchor rod 6, as shown Figure 1 (j) as shown; like Figure 6 As shown, a visual detection device for simulating the interaction between composite layered rock delamination and anchor rods includes a visual loading device, a pressure testing machine, a loading pad, and a deformation monitoring and recording device.

[0031] like Figure 4 As shown, the visual loading device contains four transparent acrylic panels 11, including two rectangular high-strength transparent panels as front and back panels, two square high-strength transparent panels as left and right side panels, and a square high-strength transparent panel as the top pressure plate 12. A fixed frame is provided on the outside of the visual loading device. like Figure 4 and Figure 5 As shown, the external fixed frame of the box includes removable front and rear reinforcement frames 13, 14, and a bottom reinforcement frame 15. The front and rear reinforcement frames 13, 14 have deep grooves extending upward from the bottom, allowing parallel light 20 to illuminate the composite layered transparent rock mass from behind the visualization detection device, allowing the speckle pattern within the composite layered transparent rock mass to be clearly observed through the transparent panel in front of the device. The deep groove at the center of the bottom reinforcement frame 15 creates an open surface for the bottom of the composite layered transparent rock mass. Shallow grooves extending from the center of the deep groove form a slot for fixing the panel.

[0032] The front reinforcement frame 13 and the rear reinforcement frame 14 of the visual loading device are fixed, the acrylic plates 11 on the left and right sides can be pushed in the horizontal direction, and the top pressure plate 12 can be pushed in the vertical direction; after the visual loading device is placed on the loading platform of the pressure testing machine, a horizontal load is applied to the visual loading device through the left horizontal loading plate 16 and the right horizontal loading plate 17, and a vertical load is applied through the top loading plate 18, so that the ratio of vertical stress and lateral stress (i.e., the pressure coefficient) exerted on the composite rock mass in the loading device remains unchanged, thereby more realistically and effectively simulating the ground stress state of the composite rock mass.

[0033] Visual detection device includes Figure 6The loading platform of the loading test machine is equipped with a left horizontal loading plate 16, a right horizontal loading plate 17, and a vertical loading plate 18. A servo motor controls the vertical loading of the loading test machine. The vertical loading system relies on the vertical loading plate 18 to apply the vertical load, while the horizontal loading system relies on the left and right horizontal passive loading plates 16 and horizontal active loading plates 17 to apply the horizontal load. The vertical and horizontal loading methods and parameters for the composite layered transparent rock mass are set using a computer 24, and the loading software system installed in the computer records the load changes in real time during the test.

[0034] The composite layered transparent rock mass is placed in the deep groove of the bottom reinforcement frame 15 of the visual loading device. The bottom surface of the composite layered transparent rock mass forms an air-facing surface. At the same time, two pads 19 of the same size are placed on the loading platform of the testing machine. The left and right ends of the bottom reinforcement frame 15 of the transparent anchoring visual loading device are placed on the pads 19. The pads on both sides simulate the layered roof supported by the two sides of the tunnel, thereby simulating tunnel excavation. The strain gauge attached to the anchor rod is connected to the strain acquisition instrument 23 via a data cable to collect the strain data obtained by the strain gauge during the composite layered transparent rock test; the basic mechanical parameters of similar materials of the anchor rod are input through the computer 24, and the anchor rod axial force data can be obtained in real time by converting between strain and stress.

[0035] A parallel light 20 was placed behind the loading device and its brightness was adjusted. A digital camera 21 was placed in front of the test device and connected to a laptop computer 22 via a data cable. The camera focus was manually adjusted to visually and clearly monitor the displacement changes of red speckles 3 on the median vertical surface within the composite layered rock mass and purple speckles 4 on the joint surfaces through the transparent loading device and similar materials of the composite layered rock mass. Images of the position changes of the red speckles 3 within the composite layered transparent rock mass and the purple speckles 4 at the bedding surfaces of the composite layered rock mass during the test loading were obtained. Using a digital photography non-contact measurement system and using the initial image as a reference image, two red speckles 3 were selected from the initial speckle photographs of the composite layered rock mass, along a straight line above and below the purple bedding interface 4 in the middle of the composite layered rock mass, as discrete points of internal delamination opening. The positions of these two speckles were used as the initial positions. The relative position changes of these two red speckles 3 at different times during the subsequent test were analyzed. The relative vertical displacement between these two speckles represented the change in delamination within the composite layered rock mass.

[0036] Using the initial image taken at the start of the test as the reference image and the positions of each speckle in the image as the initial positions, the bending deformation information within the thin soft rock layer was obtained by recording and analyzing the relative position changes of the red speckle 3 in the thin soft rock layer below the purple speckle interface 4 at different times during the test. The bending deformation information within the thick hard rock layer was obtained by recording and analyzing the position changes of the red speckle 3 in the thick hard rock layer above the purple speckle interface 4 at different times during the test. By monitoring and recording the relative position changes of the speckles within the composite layered rock mass during the test, delamination and deformation data of the composite layered transparent rock mass were obtained.

[0037] Specifically, a visual detection method and device for simulating the interaction between delamination of composite layered rock and anchor rods includes a layered transparent rock-similar material consolidation mold, a structural surface consolidation mold, an anchor rod-similar material, a consolidation instrument, a test loading mold, a pressure testing machine, a loading pad, and a deformation monitoring and recording device.

[0038] The aggregate of the transparent rock-like material is 200-300 mesh silica gel powder, and the pore liquid is a transparent mixed solution of No. 15 white oil and n-dodecane, wherein the mass ratio of No. 15 white oil to n-dodecane is 1.9:1, and the mass ratio of silica gel powder to transparent pore liquid is 0.60:1, and its refractive index is similar to that of the aggregate.

[0039] As attached Figure 3 As shown, the anchor rod similar material 6 is a fuse, and a fuse with a diameter of 2 mm is used according to the requirements. The tray 7 and the positioning patch 9 are square open iron sheets, and the opening diameter is consistent with the diameter of the fuse. The compression spring 8 is a stainless steel spring with a wire diameter of 0.3 mm, a diameter of 2 mm, and a length of 30 mm.

[0040] As attached Figure 4 As shown, the test loading mold consists of removable front and rear reinforcement frames 13 and 14 and a bottom reinforcement frame 15 made of hot-rolled steel. The bottom reinforcement frame 15 is connected to the front and rear reinforcement frames 13 and 14 using M10×40mm bolts. A 16mm diameter hole is opened at the top connection between the front reinforcement frame 13 and the rear reinforcement frame 14, and a 16mm diameter threaded hole is opened in the rear reinforcement frame 14. The two are connected and fixed using an M16 threaded rod. The threaded rod can be directly threaded through the front reinforcement frame 13 and the rear reinforcement frame 14, and then an M16 nut is installed on the front reinforcement frame 13 to secure it.

[0041] The front and rear reinforcement frames 13 and 14 have deep grooves of 150mm×150mm×20mm with the middle of the bottom as the endpoint, which can allow parallel light to illuminate the composite layered transparent rock mass from the rear of the device. The deformation information of the composite layered rock mass can be clearly and intuitively observed through the transparent panel in front of the device, and shallow grooves with a depth of 10mm and a width of 20mm are opened upward and on the left and right sides from the center of the groove to form a slot to fix the panel.

[0042] The bottom reinforcement frame 15 has a deep groove of 150mm×150mm×20mm in the center to form an air-facing surface at the bottom of the composite layered transparent rock-like material, and a shallow groove with a depth of 10mm and a width of 20mm is opened around the center of the groove to form a slot to fix the panel.

[0043] The pressure testing machine uses a servo motor for loading. The force loading mode is set through the loading software system installed in the computer. The horizontal and vertical stepper motors are controlled to apply loads to the composite layered transparent rock mass at 22.5N / S and 22.5N / S respectively. The loading is stopped when the horizontal load and vertical load are applied to 0.407MPa. The synchronous servo loading in the horizontal and vertical directions can realistically simulate the ground stress state of the composite layered rock mass under a certain lateral pressure ratio, and the load changes are recorded in real time by the computer.

[0044] The bottom pad 19 of the loading device is made of steel and has a size of 15 cm × 15 cm × 10 cm; The deformation monitoring and recording device includes a digital camera 21, a strain collector 23, a laptop computer 22, and a computer 24. The digital camera 21 is connected to the laptop computer 22 via a data cable. The computer control interface is set to capture an image every 2 seconds. The camera focus is manually adjusted so that the speckle inside the composite layered rock mass can be clearly displayed on the computer screen through the transparent loading device and similar materials of the composite layered rock mass. The camera records the position change process of the speckle inside the composite layered transparent rock mass in the loading device. Taking the initial image as the reference image, in the collected speckle photographs of the initial composite layered rock mass, two red speckles 3 were selected along a straight line above and below the purple bedding interface in the middle of the composite layered rock mass as discrete points of internal delamination. The positions of these two speckles were used as the initial positions, and the relative position changes of these two red speckles 3 at different times during the subsequent test were analyzed. The relative vertical displacement between the two speckles is the change in the internal delamination of the composite layered rock mass.

[0045] Using the initial image captured at the start of the test as the reference image and the initial positions of each speckle in the image as the initial positions, bending deformation information within the thin soft rock layer was obtained by recording and analyzing the relative positional changes of the red speckle 3 in the thin soft rock layer below the purple speckle interface 4 at different times during the test. Bending deformation information within the thick hard rock layer was obtained by recording and analyzing the relative positional changes of the red speckle 3 in the thick hard rock layer above the purple speckle interface 4 at different times during the test. Delamination and deformation data of the composite layered transparent rock mass were obtained by monitoring and recording the relative positional changes of the speckle within the composite layered rock mass during the test. A micro strain gauge with a resistance of 120 ohms and a wire grid size of 1.0 mm × 1.0 mm was attached to the anchor bolt. The strain gauge was connected to an XL2118A16(U) static resistance strain gauge 23 via a data cable using a quarter-bridge connection. Continuous monitoring was configured on a computer 24 control interface to obtain real-time information on anchor bolt axial force changes.

[0046] Specifically, the steps of a visual detection method for simulating the interaction between delamination of composite layered rock mass and anchor bolts are as follows: Step 1: Place a 15cm×5cm×1cm permeable stone on the base of a smaller consolidation mold. Use glass glue to bond four high-strength transparent acrylic plates together and fix them on the base. Pour the solid-liquid mixed solution of the prepared silica gel powder, No. 15 white oil and n-dodecane into the mold. When the height of the mixed solution in the mold reaches 10cm, place the mold in a vacuum box and keep it under vacuum negative pressure for 1 hour to exhaust the air in the solution ( Figure 1 (b)), and then a layer of red speckle surface 3 is evenly laid horizontally on the vacuumed mixed solution ( Figure 1 (c) Pour the mixed solution into the mold again, and after reaching the required design height, vacuum it for the second time to form a transparent solid-liquid mixture ( Figure 1 (d)).

[0047] Step 2: Install the two halves of the mold on the outside of the mold and install the reinforcement rods on the outside ( Figure 1 (e)). Place the assembled mold on the high-pressure oedometer, put the pressure head on the top of the mold, and turn on the oedometer switch ( Figure 1 (f) A consolidation pressure of 10 MPa was applied for 24 h. After the consolidation time was reached, the formwork was removed, revealing a thin, transparent, soft rock layer with a red speckled surface 3 in the middle of the lower layer of the composite layered rock mass along the vertical direction.

[0048] Step 3: Using a thicker (or wider) consolidation mold, repeat steps 1 and 2 (applying a consolidation pressure of 20 MPa and consolidating for 60 hours) to prepare a transparent thick hard rock layer containing a red speckle surface 3 in the middle of the upper layer of the composite layered rock mass along the vertical height direction.

[0049] Step 4: According to the actual situation of composite layered rock mass engineering, the consolidated layered transparent rock mass similar material is rotated 90 degrees in the direction perpendicular to the positive surface of the rock mass and placed. The transparent thick hard rock layer is vertically superimposed on the transparent thin soft rock layer in order (different combinations such as hard on top and soft on bottom, thick on top and thin on bottom) to form a composite layered rock mass. The vertical planes of the two vertically superimposed transparent rock mass similar materials are both a red speckle surface 3, as shown in Figure 3. Figure 1 As shown in (h), a speckle surface is formed for monitoring the internal deformation of the composite layered rock mass, and a layer of purple, very thin aggregate with a particle size of 60-80 mm is added between the overlapping surfaces. The aggregate is placed in the structural surface consolidation mold, and the mold is placed on the consolidation instrument. A consolidation pressure of 2 MPa is applied and the consolidation is carried out for 12 hours. After the consolidation time is reached, the mold is removed. Figure 1 As shown in (h); along the thickness direction of the bottom surface of the thin soft rock layer 2 of the consolidated composite layered transparent rock mass, holes with a depth of 10 cm are drilled according to the anchor spacing of 50 mm, and the anchoring agent is injected; the anchoring agent is injected to a depth of 4 cm; a 13 cm long anchor rod 6 is cut, and a strain gauge 5 is attached to the 6 cm length of the fuse and fixed with insulating glue. The anchor rod 6 is inserted, and after the anchoring agent solidifies, the tray 7 and spring 8 are installed; after the spring 8 is installed, the positioning iron sheet 9 is placed to compress the spring; then the lock buckle 10 is rotated and retracted to apply pre-tightening force to the anchor rod, as shown in FIG. Figure 1 (j) shown.

[0050] Step 5: Place equal-height pads 19 on the test loading platform with a depth of 6.5 cm on both sides with the platform centerline as the center; place the bottom reinforcement frame 15 along the centerline so that the lengths of its left and right ends resting on the pads 19 on both sides are the same; then place the composite layered transparent rock model into the deep groove in the bottom reinforcement frame 15.

[0051] Step 6: Bolt the rear reinforcement frame 14 to the bottom reinforcement frame 15, and place the rear acrylic panel in the shallow groove opened by the bottom reinforcement frame 15 and the rear reinforcement frame 14. The panel size is consistent with the front groove size, and there is no gap between the two to prevent the panel from moving; place the left and right acrylic panels in the shallow groove opened by the bottom reinforcement frame 15; place the front acrylic panel in the shallow groove of the bottom reinforcement frame 15, and the surrounding panels are tightly fitted with the internal transparent rock-like material.

[0052] Step 7: After the acrylic panel is installed, bolt the front reinforcement frame 13 to the bottom reinforcement frame 15, and the front acrylic panel is placed in the shallow groove of the front reinforcement frame 13; pass the two threaded rods through the holes of the front reinforcement frame 13 and thread them with the rear reinforcement frame 14, then screw nuts on the side of the threaded rods on the front reinforcement frame 13 to lock them.

[0053] Step 8: Connect the strain gauge on the anchor bolt to a static resistance strain gauge 23 via a data cable. The static resistance strain gauge is also connected to a computer 24 via a data cable. Input the mechanical parameters of the fuse material into the computer 24, set up continuous monitoring, and obtain real-time anchor bolt axial force monitoring data through stress-strain conversion. Place a parallel light 20 behind the loading device and adjust its brightness. Place a digital camera 21 in front of the test device and connect it to a laptop computer 22 via a data cable. Manually adjust the camera's focus so that the speckle pattern within the composite layered rock mass can be clearly displayed on the computer screen through the transparent loading device and similar materials. Use the camera to record the positional changes of the speckle pattern within the composite layered transparent rock mass within the loading device.

[0054] Using a digital photography non-contact measurement system, with the initial image as the reference image, two red speckles 3 were selected along a straight line above and below the purple bedding interface in the middle of the composite layered rock mass in the initial test speckle photographs collected. The positions of the two speckles were used as the initial positions, and the relative position changes of the two red speckles 3 at different times during the subsequent test were analyzed. The relative vertical displacement between the two speckles is the change in the internal delamination of the composite layered rock mass.

[0055] Using the initial image taken at the start of the test as the reference image and the positions of each speckle in the image as the initial positions, the bending deformation information within the thin soft rock layer was obtained by recording and analyzing the relative position changes of the red speckle 3 in the thin soft rock layer below the purple speckle interface 4 at different times during the test. The bending deformation information within the thick hard rock layer was obtained by recording and analyzing the position changes of the red speckle 3 in the thick hard rock layer above the purple speckle interface 4 at different times during the test. By monitoring and recording the relative position changes of the speckles within the composite layered rock mass during the test, delamination and deformation data of the composite layered transparent rock mass were obtained.

[0056] Step 9: Place the top pressure plate 12 on top of the composite layered transparent rock mass, and move the horizontal passive loading plate 16 of the pressure testing machine to close contact with the acrylic plate on the left side of the test device. The horizontal and vertical directions adopt a stepper motor-controlled pressure loading method. Through the servo control of the computer 24 of the loading testing machine, pre-load is first performed to make the box acrylic plate 11 close contact with the loading plates in the horizontal and vertical directions. Then, set the pressure loading method to force loading, control the horizontal and vertical stepper motors to simultaneously apply loads to the composite layered transparent rock mass at 22.5N / S and 22.5N / S respectively. Stop loading when the horizontal load and vertical load are applied to 0.407MPa, and record the load and displacement changes in real time on the computer. Example

[0057] The collected photos were analyzed by PhotoInfor, and the evolution of deformation and delamination of composite layered rock mass and the variation law of vertical displacement field under load were obtained. Figure 7 As shown in the figure, the variation curve of the separation layer of the composite layered rock mass and the variation curve of the anchor axial force are shown in the figure. Figure 7 As shown in the figure, the delamination deformation curve of the composite layered rock mass shows a trend of slow growth followed by rapid expansion before ultimately stabilizing. The anchor axial force curve shows a rapid increase and fluctuation in the OD stage, a rapid increase in the DE stage, and ultimately stabilization. Based on the deformation patterns of the composite rock mass and the axial force variation of the anchor, the composite rock mass deformation process can be divided into three stages: stable stage, rapid deformation development stage, and stabilization stage.

[0058] In the stable stage (OB stage), at the initial stage of vertical and horizontal load loading (point O), the load is about 0.01MPa, the surrounding rock is stable, no cracks are generated, and the deformation is extremely small. Figure 8 (a) and Figure 8 As shown in (b), the weak rock layer at the bottom of the composite rock mass first undergoes bending deformation. However, due to the anchoring action of the anchor bolts, the initial deformation is minimal, approximately 0.61 mm. Based on similarity theory, the initial bending settlement of the composite rock mass in actual engineering practice is approximately 12.2 mm, which is consistent with the actual deformation. The displacement vectors of the various rock layers in the composite rock mass are consistent in direction and extremely small in length, indicating that no significant delamination has occurred between the rock layers and that the axial force of the anchor bolts has changed little.

[0059] As the load increases to 0.056MPa, the surrounding rock deforms significantly and cracks gradually appear. Due to the low elastic modulus of the weak rock layer at the bottom, the deformation of the weak rock layer at the bottom accelerates, and the bending sinking increases to 1.38mm. Figure 8 As shown in (d), according to the similarity theory, the bending delamination of the composite layered rock mass in the actual project is about 27.6mm, which is consistent with the actual deformation of the project. The displacement vector direction of the bottom weak rock layer is almost the same as that of the upper rock layer, but the displacement vector length of the bottom weak rock layer is significantly greater than that of the upper rock layer. At the same time, the displacement vectors on both sides of the rock mass point to the middle, indicating that shear slip occurs between the rock layers and delamination begins to occur. Figure 8 (c) As shown in the displacement cloud diagram, the displacement of the displacement vector endpoint in the middle of the upper rock layer of the delamination interface is about 1.12mm, and the displacement of the displacement vector endpoint in the middle of the lower rock layer is about 1.27mm. At this time, the delamination amount is about 0.15mm. According to the similarity theory, the bending delamination amount of the composite layered rock mass in actual engineering is about 3mm, which is consistent with the actual deformation of the engineering. As the delamination between the rock layers increases, the test anchor is subjected to tension, and the axial force increases rapidly to the first extreme point, specifically Figure 7At point A in the figure, the axial force of the anchor rod is about 16.1N. According to the similarity theory, the axial force of the corresponding prototype anchor rod is 28.18kN. And under the action of tensile stress, the weak rock layer at the bottom begins to crack, such as Figure 8 As shown in (c), a small amount of damage occurs at the tray, resulting in a short rebound of the anchor rod, loss of anchoring force, and reduction of the axial force to the extreme point. Figure 7 At point B, the axial force of the anchor rod is 13.9N. According to the similarity theory, the axial force of the corresponding prototype anchor rod is 24.33kN.

[0060] During the rapid deformation development stage (BE stage), the cracks in the composite rock mass expand rapidly and the deformation of the surrounding rock increases. Figure 8 (e) and Figure 8 As shown in (f), the rock formation deforms violently, and the weak rock formation at the bottom bends and sinks violently, with its bending deformation rapidly increasing to 3.05mm. The displacement vector length of the weak rock formation at the bottom increases sharply, while the displacement vector length of the upper rock formation increases less, resulting in a large gap between the displacement vector lengths of the upper rock formation, and the amount of separation between the rock formations increases sharply. Combined with the displacement cloud map, it can be seen that the displacement of the middle displacement vector endpoint of the upper rock formation at the separation interface is about 2.36mm, and the displacement of the middle displacement vector endpoint of the lower rock formation is about 2.70mm. At this time, the separation amount is about 0.34mm. The number of cracks increases rapidly, and inclined cracks are generated at the shoulder angle of the weak rock formation at the bottom, and continue to develop rapidly upward. The separation amount between the rock formations increases sharply, the anchor rod is stretched, and the axial force increases to the extreme point, specifically Figure 7 At point C, the anchor bolt's axial force is 21 N. Based on similarity theory, the corresponding axial force in the prototype anchor bolt is 36.75 kN. The tensile stress on the anchor bolt rapidly increases, and the surrounding rock at the anchor bolt's anchoring interface breaks, causing shear slippage in the anchor bolt, resulting in a temporary decrease in the anchor bolt's axial force to 17.7 N. This change in anchor bolt axial force is consistent with fluctuations in anchor bolt axial force in actual engineering practice.

[0061] like Figure 8 (g) and Figure 8As shown in (h), numerous new cracks have developed in the weak bottom rock strata, and the rate of development is extremely rapid. Inclined cracks in the weak bottom rock strata develop upward through the delamination. The upper hard rock strata have not yet been damaged and are compressively deformed under the load. This increases the shear stress between the anchor and the surrounding rock at the anchoring interface, enabling the anchor to provide better anchoring force. However, the weak bottom rock strata are severely fractured, significantly reducing their bearing capacity and causing severe bending deformation, with deformation increasing to 8.8 mm. Based on similarity theory, the actual bending settlement of the composite layered rock mass at this point in the project is approximately 176 mm, which is consistent with the actual deformation in the project. The displacement cloud shows that the displacement of the endpoint of the displacement vector in the middle of the upper rock layer of the delamination interface is approximately 5.94 mm, while the displacement of the endpoint of the displacement vector in the middle of the lower rock layer is approximately 8.08 mm. The delamination between the rock layers rapidly increases to 2.14 mm. Based on similarity theory, the bending delamination of the composite layered rock mass in actual engineering practice is approximately 42.8 mm at this point, which is consistent with the actual deformation in the project. The axial force of the anchor bolt rapidly increases to 28.3 N. Based on similarity theory, the axial force of the corresponding prototype anchor bolt is 49.53 kN. This causes the anchor bolt to be stretched, and the axial force increases rapidly with the rapid increase in delamination.

[0062] Stable stage, specifically Figure 7 At the stage after point E, the load is 0.229MPa, the soft and thin rock layer has been completely destroyed, and the thick and hard rock layer has not been completely destroyed. Figure 8 (i) and Figure 8 (j) As shown, Figure 7 At point F, the crack line in the weak rock layer at the bottom of the transparent specimen extends deep into the upper hard rock layer. However, the upper hard rock layer is relatively intact and provides greater bearing capacity. Therefore, under the strong anchoring force of the anchor bolt, the weak rock layer at the bottom is suspended in the upper hard rock layer, slowing the deformation of the surrounding rock. The displacement vector length of each rock layer continues to increase slowly, the deformation of the weak rock layer at the bottom slowly increases to 10.10 mm, and the delamination between rock layers slowly increases to 3.09 mm. According to similarity theory, the bending settlement of the composite layered rock mass at this point in the actual project is approximately 202 mm, and the delamination is approximately 61.8 mm, which is consistent with the actual deformation in the project. The axial force of the anchor bolt then slowly increases to 32.0 N. According to similarity theory, the corresponding axial force of the prototype anchor bolt is 56.00 kN. The changes in the deformation and delamination of the composite layered rock mass in the model test are consistent with the changes in the deformation of the composite rock mass in the actual project. The anchor bolt axial force value also conforms to the axial force variation pattern of the prototype anchor bolt.

[0063] The model test results of rock mass with and without anchor bolts were analyzed. From the deformation curve of surrounding rock delamination, it can be seen that the development of composite rock delamination was effectively suppressed after adding preload anchor bolts. The peak delamination volume of composite layered rock mass without anchor bolts was larger, while the peak delamination volume of composite layered rock mass with preload anchor bolts was relatively small, at 3.09 mm, which was reduced by 26.43% compared with the model test without anchor bolts.

[0064] From the perspective of the deformation and failure process, the application of increased preload anchors significantly improved the structural integrity of the rock mass. The degree of crack development in the composite layered rock mass was significantly reduced, and the amount of surrounding rock crushing was reduced. In particular, only a small number of cracks appeared in the upper hard rock layer, which was able to maintain good integrity and effectively anchor the weak rock layer in the upper hard rock layer, greatly avoiding the risk of instability and collapse after the weak rock layer was destroyed.

Claims

1. A visual detection method for simulating the interaction between composite layered rock delamination and anchor bolts, characterized in that: Here are the steps: A transparent thin soft rock layer simulating a soft rock layer and a transparent thick hard rock layer simulating a hard rock layer are respectively produced, wherein the middle of the thin soft rock layer and the transparent thick hard rock layer are both provided with a speckle surface a; A thin soft rock layer is placed below a thick hard rock layer, and the original speckle surface a in the two layers is spliced ​​together. Another speckle surface b is set between the contact surface of the thin soft rock layer and the thick hard rock layer to form a bedding interface, thereby forming a composite layered transparent rock mass with a hard upper layer and a soft lower layer and a weak structural surface. The speckle surface a and the speckle surface b in the composite layered transparent rock mass are perpendicular to each other. An anchor hole required for the test is drilled vertically in the thickness direction of the thin soft rock layer of the composite layered transparent rock mass. A simulated anchor made of a fusible wire is installed in the anchor hole. A strain gauge is provided on the simulated anchor. The strain gauge on the simulated anchor is connected to a computer via a static resistance strain acquisition instrument to obtain the simulated anchor strain data, thereby obtaining the anchor axial force. Assemble a visual loading device on the outside of the composite layered transparent rock mass and then install it on the loading platform. Use the composite layered transparent rock mass to simulate the composite layered roadway roof. Set up a video acquisition system on the side of the visual loading device. A loading platform was used to load the composite layered transparent rock mass to simulate the deformation of the composite layered tunnel roof with different anchors inside under different stresses. A video acquisition system was used to capture the position change images of speckle plane a and speckle plane b in the composite layered transparent rock mass during the loading process. By analyzing the relative position changes of the speckles formed by speckle plane a and speckle plane b at different times during the loading test, information on the change of the deformation and delamination of the composite layered transparent rock mass with the axial force of the anchor was obtained. The strain data of the simulated anchor was obtained by strain gauges, and the axial force information of the anchor was obtained by synchronous calculation, realizing the study of the interaction between the delamination of the composite layered rock mass and the anchor.

2. The visual detection method for simulating the interaction between delamination of composite layered rock mass and anchor bolts according to claim 1, characterized in that: The rock-similar material solution includes silica gel powder with a particle size of 200-300 mesh and clear pore liquid, and the mass ratio of silica gel powder to clear pore liquid is 0.60:1; the clear pore liquid is a transparent mixed solution composed of No. 15 white oil and n-dodecane, and the refractive index of the transparent mixed solution is similar to that of the aggregate, and the mass ratio of No. 15 white oil to n-dodecane is 1.9:

1.

3. The visual detection method for simulating the interaction between delamination of composite layered rock mass and anchor bolts according to claim 1, characterized in that: The simulated anchor rod includes a fusible wire as the rod body. The fusible wire is selected based on the theory of similar materials. A locking structure is provided inside the tail end of the fusible wire. The locking structure includes a tray and a positioning patch sleeved on the tail of the fusible wire. A compression spring sleeved on the fusible wire is provided between the tray and the positioning patch. A locking buckle for fastening is provided behind the positioning patch. Among them, the tray and the positioning patch are square iron sheets with a hole diameter consistent with the diameter of the fusible wire. The diameter of the fusible wire is 2 mm. The compression spring has a wire diameter of 0.3 mm, a diameter of 2 mm, and a length of 30 mm. The strain gauge is pasted 6 cm away from the end of the anchor rod to monitor the change information of the anchor rod axial force at the delamination of the composite layered rock structure surface.

4. The visual detection method for simulating the interaction between delamination of composite layered rock mass and anchor bolts according to claim 1, characterized in that: A light source for an auxiliary video acquisition system is set on the side of the loading platform. The video acquisition system collects images so that the mutually perpendicular speckle planes a and b in the composite layered transparent rock mass can be clearly observed and recorded. During the loading process, the video acquisition system can intuitively and clearly monitor the position changes of the speckle planes a and b inside the composite layered rock mass, the deformation and rupture of the composite layered rock mass, and the development of cracks in the composite layered rock mass through the visual loading device and the surface of the composite layered rock mass.

5. The visual detection method for simulating the interaction between delamination of composite layered rock mass and anchor bolts according to claim 1, characterized in that: During the loading process, the loading platform was used to apply horizontal and vertical forces to the composite layered rock mass. The stepper motors used to control the horizontal and vertical loading were used to simultaneously apply loads to the composite layered transparent rock mass at 22.5 N / S and 22.5 N / S, respectively. Loading was stopped when the horizontal and vertical loads reached 0.407 MPa. At this time, the ratio of horizontal load to vertical load was 1.

0. The real-time load changes loaded by the testing machine were collected to obtain the simulated ground stress state information of the composite layered rock mass with the simulated anchor bolts.

6. The visual detection method for simulating the interaction between delamination of composite layered rock mass and anchor bolts according to claim 1, characterized in that: Speckle surface a is a red speckle surface, and speckle surface b is a purple speckle surface.

7. The visual detection method for simulating the interaction between delamination of composite layered rock mass and anchor bolts according to claim 6, characterized in that: The process of making a transparent thin soft rock layer simulating a weak rock layer and a transparent thick hard rock layer simulating a hard rock layer is as follows: A mixed solution of aggregate and pore liquid with a particle size of 200-300mm is poured into the thin layer mold. After vacuum exhaust, a layer of red aggregate with the same particle size is laid on the first layer of solid-liquid mixture to form a red speckle surface for monitoring the internal deformation of the rock mass. Then, the solid-liquid mixture of the designed height is poured in, and vacuum exhaust is performed again to form a transparent solid-liquid mixture; a high-pressure consolidation instrument is used to apply a consolidation pressure of 10MPa to the solid-liquid mixture in the thin layer mold, and the consolidation is carried out for 24 hours to obtain a transparent thin soft rock layer with a red speckle surface in the middle; the production process of the transparent thick hard rock layer is repeated using a thick layer transparent mold, and the high-pressure consolidation instrument is adjusted to a consolidation pressure of 20MPa for consolidation for 60 hours to prepare a transparent thick hard rock layer with a red speckle surface in the middle.

8. The visual detection method for simulating the interaction between delamination of composite layered rock mass and anchor bolts according to claim 7, characterized in that: The method for producing a composite layered transparent rock mass with a hard upper and soft lower structure by using a transparent thin soft rock layer and a transparent thick hard rock layer is as follows: The prepared transparent thick hard rock layer and transparent thin soft rock layer were demolded and rotated 90° in the direction perpendicular to the positive surface of the rock mass. The transparent thick hard rock layer was vertically superimposed on the transparent thin soft rock layer and the red speckle surfaces of the two were aligned. A layer of purple aggregate was added between the superimposed surfaces and then placed into a structural surface consolidation mold. After consolidation using a consolidation instrument, a composite layered rock mass with a purple speckle surface for monitoring the internal bending, deformation and delamination of the composite layered rock mass was formed. The consolidation instrument was continued to apply a consolidation pressure of 2 MPa to the composite layered rock mass placed in the structural surface consolidation mold. After consolidation for 12 hours, the mold was removed to obtain a composite layered transparent rock mass containing a weak structural surface.

9. The visual detection method for simulating the interaction between delamination of composite layered rock mass and anchor bolts according to claim 8, characterized in that: The image of the composite layered rock mass before loading was obtained by the video acquisition system was used as the reference image. Two red speckle points were selected from the red speckle surface on the upper and lower sides of the purple speckle surface along the straight line in the reference image as the discrete points of the delamination opening inside the rock mass. The relative position changes of these two red speckle points at different times during the loading process were compared. As the composite layered transparent rock mass was loaded, the two red speckle points underwent obvious relative vertical displacement, indicating that delamination occurred inside the composite layered rock mass at this time. Analysis of the relative vertical displacement between the two red speckle points is the change in the delamination inside the composite layered rock mass. Taking the image of the composite layered rock mass before loading is started as the reference image, the bending deformation information inside the thin soft rock layer is obtained by comparing and analyzing the relative position changes of the red speckles in the thin soft rock layer below the purple speckle interface in the composite layered rock mass at different times during the loading process. The bending deformation information inside the thick hard rock layer is obtained by recording and analyzing the position changes of the red speckles in the thick hard rock layer above the purple speckle interface in the composite layered rock mass at different times during the test.

10. The visual detection method for simulating the interaction between delamination of composite layered rock mass and anchor bolts according to claim 9, characterized in that: The video acquisition system has a shooting interval of 1 second to ensure that a complete and continuous image of the speckle changes inside the rock mass is obtained through the surface of the composite layered rock mass. In addition, it can intuitively obtain information on the changes in deformation, fracture, and crack development of the composite layered rock mass during the test. The static strain meter continuously monitors and collects the simulated anchor axial strain data, and through stress-strain calculation, the collected anchor axial strain is converted into anchor axial force data, which can obtain information on the changes in anchor axial force with the deformation and delamination of the composite layered rock mass during the experiment.

Images