Method for testing compressive property of safety guarantee cabin based on equivalent scale model

Abstract

The invention relates to a method for testing the compressive property of a safety guarantee cabin based on an equivalent scale model, and belongs to the technical field of tunnel construction safety equipment. According to the method, the scaling proportion is determined through a dimensional analysis method, a support cabin scaling model is constructed, and the tunnel collapse mechanical environment is reproduced by combining two working conditions of surrounding rock pressure simulation and top static load; a graded loading-pressure relief mode is adopted, cabin response is monitored in real time through distributed strain measuring points and deformation measuring points, and structural safety is evaluated through stress distribution and deformation analysis. According to the method, the full-size test cost is remarkably reduced, and an efficient and accurate verification means is provided for development of tunnel emergency rescue equipment.

Description

Technical Field

[0001] The present invention belongs to the technical field of tunnel construction safety equipment, and specifically relates to a compressive performance testing method for a tunnel construction safety cabin based on an equivalent scaled model, which is used for low-cost verification of the structural safety of an emergency rescue cabin under landslide disasters. Background Art

[0002] During tunnel construction, collapses behind the tunnel face can trap personnel. As an emergency evacuation device, the safety cabin must provide a reliable, enclosed living space for survivors. Depending on the actual working conditions, the cabin must withstand the complex mechanical loads of a collapse, including the overall confining static load from the roof and lateral rock collapse, as well as the uniformly distributed static load on the cabin roof area from falling rocks. To ensure the cabin's structural safety, its compressive performance in disaster environments must be verified through testing.

[0003] Currently, the industry's verification methods mostly rely on full-scale chamber testing, which has significant drawbacks such as high testing costs and long testing cycles. Traditional scaled models also lack physical similarity guarantees, and conventional geometric scaling methods fail to adhere to strict similarity theory, resulting in distortions in stress and strain proportions. Therefore, a low-cost testing method based on strict similarity theory and covering multiple hazard conditions is needed to address the limitations of full-scale testing. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for testing the pressure resistance of a safety cabin based on an equivalent scale model, so as to solve the problems of high cost and insufficient simulation accuracy of full-scale tests proposed in the background art.

[0005] To achieve the above object, the present invention provides a method for testing the pressure resistance of a safety cabin based on an equivalent scale model, comprising the following steps:

[0006] Step 1: Determine the scale ratio based on dimensional analysis and construct a scale model of the support cabin;

[0007] Step 2: applying a full confining pressure condition simulating surrounding rock pressure and a top static load condition simulating collapse vertical pressure to the scaled model through a loading device;

[0008] Step 3: Arrange multiple strain measurement points in the key stress-bearing areas of the model frame, and arrange deformation measurement points at multiple locations on the cabin surface;

[0009] Step 4: applying load to the scaled model using a graded loading and unloading mode;

[0010] Step 5: Collect data through the strain measurement device and the displacement measurement device, analyze the stress distribution and structural deformation based on the strain data and deformation data, and evaluate the pressure resistance and safety of the support cabin.

[0011] In a specific embodiment, in step 2, the loading device includes at least one top jack and at least one side jack, and each jack contacts the scaled model through a uniform force plate to apply a uniform load;

[0012] The comprehensive confining pressure working condition is achieved by the synchronous application of force by the top jack and the side jack;

[0013] The top static load condition is achieved only by applying force from the top surface jack.

[0014] In a specific embodiment, in step 3, the strain measuring points are arranged at stress concentration areas of the frame based on finite element stress analysis results, including mid-span positions of transverse stiffeners or frame connection nodes.

[0015] In a specific embodiment, in step 5, the data analysis includes:

[0016] Eliminate systematic errors and singular terms in collected data;

[0017] Determine the linear response range of the structure through stress-strain curve;

[0018] The residual deformation rate is calculated to evaluate the elastic recovery capacity of the structure.

[0019] In a specific embodiment, in step 1, the frame structure of the scaled model is welded with high-strength steel and includes transverse reinforcing ribs and longitudinal support beams.

[0020] In a specific embodiment, in step 5, the safety assessment includes:

[0021] Verify that the stress of the model frame under maximum load is lower than the material yield strength;

[0022] Verify that the local deformation under maximum load is less than a predetermined threshold.

[0023] In a specific embodiment, step 5 further includes generating stress distribution diagrams and compressive performance evaluation reports of measuring points under different working conditions.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention significantly reduces the cost of full-scale testing and provides an efficient and accurate verification method for the development of tunnel emergency rescue equipment.

[0026] The present invention constructs a scaled model through the law of physical similarity, simultaneously loads multiple disaster conditions, and verifies the dual criteria of structural safety. It solves the significant defects of the full-scale cabin test verification currently used in the industry, such as high test cost and long test cycle, as well as the lack of physical similarity guarantee of traditional scaled models and the conventional geometric scaling method that does not follow strict similarity theory, resulting in distortion of stress and strain proportions.

[0027] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention is further described in detail below. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0029] Figure 1 A flowchart of steps of an embodiment of the present invention;

[0030] Figure 2 This is a clamping diagram of a scaled model test cabin according to an embodiment of the present invention;

[0031] Figure 3 This is a reinforcement frame for arranging strain measuring points on a cabin according to an embodiment of the present invention. In the figure, A1, A2, and A3 are three frames for arranging strain measuring points.

[0032] Figure 4 For the present invention Figure 4 The strain measurement points on each reinforcement frame are arranged, where 1 to 12 are the numbers of different strain measurement points. The frames A1, A2, and A3 in the figure correspond to Figure 3 Numbers A1, A2, A3 in the table;

[0033] Figure 5 This is a diagram showing the arrangement of deformation test points according to an embodiment of the present invention, where B1, B2, and B3 are the numbers of the deformation test points.

[0034] Figure 6 These are the stress measurement results of each point on the A1 frame under full confining pressure conditions in one embodiment of the present invention;

[0035] Figure 7 These are the stress measurement results of each point on the A2 frame under full confining pressure conditions in one embodiment of the present invention;

[0036] Figure 8 These are the stress measurement results of each point on the A3 frame under full confining pressure conditions in one embodiment of the present invention;

[0037] Figure 9The deformation results of different measuring points under full confining pressure conditions of an embodiment of the present invention are shown;

[0038] Figure 10 These are the stress measurement results of each point on frame A1 under the top static load condition of an embodiment of the present invention;

[0039] Figure 11 These are the stress measurement results of each point on the A2 frame under the top static load condition of an embodiment of the present invention;

[0040] Figure 12 These are the stress measurement results of each point on the A3 frame under the top static load condition of an embodiment of the present invention;

[0041] Figure 13 These are the deformation results of different measuring points under the top static load condition of an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The embodiments of the present invention are described in detail below. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0043] A method for testing the compressive performance of a safety cabin based on an equivalent scaled model of the present invention comprises the following steps:

[0044] Step 1: Determine the scale ratio based on dimensional analysis and construct a scale model of the support cabin;

[0045] The frame structure of the scaled model is welded with high-strength steel and includes transverse reinforcing ribs and longitudinal support beams.

[0046] Construct a scaled model, determine the scale factor S = 1 / 4 based on dimensional analysis, and scale the parameters according to the following physical similarity law: length, area, and volume are respectively scaled by the scale factors S, S 2 、S 3 Scaling, stress, strain, elastic modulus scaling factor is 1.0 to ensure the consistency of material mechanical behavior; load according to S 2 The static load pressure scale factor is 1.0. The scaled model is made of Q345 steel, which has an elastic modulus of 210 GPa and a Poisson's ratio of 0.3, the same as the prototype.

[0047] Step 2: applying a full confining pressure condition simulating surrounding rock pressure and a top static load condition simulating collapse vertical pressure to the scaled model through a loading device;

[0048] The loading device includes at least one top jack and at least one side jack, each jack being in contact with the scaled model through a uniform force plate to apply a uniform load;

[0049] The comprehensive confining pressure working condition is achieved by the synchronous application of force by the top jack and the side jack;

[0050] The top static load condition is achieved only by applying force from the top surface jack.

[0051] Multi-condition loads are applied using a hydraulic system that drives an array of cylinders. Loads are applied in two different conditions, tailored to the actual disaster environment: The full confining pressure condition uses simultaneous loading from the top and side cylinders to simulate roof and lateral surrounding rock pressure. Top and side loads are applied in stages to maximum load, with force plates installed at the ends of the cylinders to ensure even load distribution. The top static load condition uses only the top cylinder to maximum load, simulating the vertical pressure of a landslide.

[0052] Step 3: Arrange multiple strain measurement points in the key stress-bearing areas of the model frame, and arrange deformation measurement points at multiple locations on the cabin surface;

[0053] The strain measuring points are arranged in the stress concentration areas of the frame based on the finite element stress analysis results, including the mid-span positions of the transverse reinforcements or the frame connection nodes.

[0054] To monitor the structural response, a sensor network is deployed at key locations of the cabin, strain gauges are evenly arranged at the mid-span and nodes of the main transverse stiffener frame of the cabin, and strain data is collected through static strain gauges; large-scale dial indicators are set at different locations on the front side and top surface of the cabin to monitor the deformation.

[0055] Step 4: Apply load to the scaled model using a graded loading and unloading mode.

[0056] Step 5: Collect data through the strain measurement device and the displacement measurement device, analyze the stress distribution and structural deformation based on the strain data and deformation data, and evaluate the pressure resistance and safety of the support cabin.

[0057] The data analysis includes:

[0058] Eliminate systematic errors and singular terms in collected data;

[0059] Determine the linear response range of the structure through stress-strain curve;

[0060] The residual deformation rate is calculated to evaluate the elastic recovery capacity of the structure.

[0061] The safety assessment includes:

[0062] Verify that the stress of the model frame under maximum load is lower than the material yield strength;

[0063] Verify that the local deformation under maximum load is less than a predetermined threshold.

[0064] Safety performance verification is carried out based on the collected data using two criteria: stress and deformation. Strength criterion: strain value is converted into stress value according to Hooke's law, and the maximum stress is required to be less than the yield strength of Q345 steel 345MPa; stiffness criterion: maximum deformation is less than 20mm.

[0065] Step 5 also includes generating stress distribution diagrams and compressive performance evaluation reports of measuring points under different working conditions.

[0066] Example 1

[0067] The present invention provides a method for testing the pressure resistance of a safety cabin based on an equivalent scale model, comprising the following steps:

[0068] Step S10. This embodiment uses a safety cabin with a rated static load of 500kPa as the test object. First, a scaled model is constructed based on the dimensional analysis method. The scale conversion criteria are shown in the dimensional conversion table in Table 1, and the scale factor S is 1 / 4. The outer dimensions of the prototype cabin are 3600mm×1680mm×1882mm. After scaling by the length scale factor S=1 / 4, the size of the scaled model is determined to be 900mm×420mm×470.5mm. The material of the scaled model is Q345 steel, which has an elastic modulus of 210GPa, a Poisson's ratio of 0.3, and a yield strength of 345MPa. It is manufactured through a welding process to ensure that the frame structure is consistent with the prototype: 9 side reinforcement ribs are evenly distributed longitudinally, and 9 transverse top reinforcement ribs are evenly set on the top. The reinforcement ribs are T-shaped steel, the web height is 20mm, the wing width is 20mm, and the thickness remains the prototype value of 2mm.

[0069] Step S20: Select appropriate data acquisition equipment, and test the equipment by Figure 2 The clamping device shown is fixed with a jack for pressurization, the strain data is measured using a DH3816N static strain tester, and the deformation is monitored using three large-scale dial indicators (range 0-30 mm, accuracy 0.01 mm).

[0070] Table 1 Dimension conversion table

[0071]

[0072] Where L and F are basic dimensions, L is length, F is force, and S is the scale factor;

[0073] Step S30: Before the test, the strain gauge measurement points should be arranged. Figure 3 The three transverse reinforcement frames shown in the figure have four strain gauges arranged on each frame, for a total of 12 strain gauges. Figure 4As shown, there are 4 strain gauges arranged in frame A1, numbered 1-4; 4 strain gauges arranged in frame A2, numbered 5-8; and 4 strain gauges arranged in frame A3, numbered 9-12. According to the finite element deformation calculation results of the cabin under different working conditions, key locations are selected to place dial indicators to test the deformation values ​​of the cabin under different loading conditions. Figure 5 The three measuring points shown are used as the main test objects for deformation under full confining pressure conditions, among which measuring point B1 is the front part of the side of the cabin, measuring point B2 is the middle part of the top surface of the cabin, and measuring point B3 is the rear part of the top surface.

[0074] Step S40: Perform the test operation under the full confining pressure condition. Place the scaled model on the clamping test bench, fix the front and rear directions with limit blocks, and use jacks to simultaneously apply uniform static loads in the vertical and horizontal directions of the cabin to simulate the structural stress and deformation of the cabin under the full confining pressure. According to the scaled model dimensional conversion relationship, the top load of the scaled model static load test is 0.5MPa, the side load is 0.25MPa, the maximum load of the top test is 18.9KN, and the maximum load of the side test is 9.4KN. The loading is divided into 5 levels, and the specific loading is shown in Table 2:

[0075] Table 2 Comprehensive confining pressure loading classification

[0076]

[0077] Step S50: Record and analyze the test data after each load level stabilizes, and record the strain value output by the DH3816N static strain gauge. Under the condition of full confining pressure loading, the strain value (με) of the support cabin measuring point under each level of load is shown in Table 3.

[0078] Table 3 Raw data strain table of full confining pressure test results (με)

[0079]

[0080] To visually display the stress values ​​at the measuring points under various loading conditions, the converted stress values ​​(MPa) are given in Table 4 based on Hooke's law. The actual strength of the support cabin steel is Q345 grade, with a yield strength of 345 MPa.

[0081] Table 4. Raw data stress table of full confining pressure test results (MPa)

[0082]

[0083] Figure 6-8 The stress variation curves of the A1, A2, and A3 frame measuring points as a function of load are given. It can be seen from the figure that:

[0084] (1) For strain gauges 1-4 on frame A1, the maximum stress occurs at strain gauge 3, which is compressive stress with a value of 272.8 MPa, which is lower than the yield strength of Q345r steel.

[0085] (2) For strain gauges 5-8 on frame A2, the maximum stress occurs at strain gauge 7, which is compressive stress with a value of 652.7 MPa, which is greater than the yield strength of Q345r steel.

[0086] (3) For strain gauges No. 9-12 on the A3 frame, the maximum stress occurs at strain gauge No. 10, which is compressive stress with a value of 322.6 MPa, which is lower than the yield strength of Q345r steel.

[0087] These results indicate that under full confining pressure, the maximum stress at some measuring points in the support cabin exceeded the allowable stress of the material. This may be due to deformation of the uniform plate structure, which led to load concentration. However, the support cabin structure did not suffer significant damage or instability, and the main frame structure of the scaled model was safe under these conditions.

[0088] Step S60: Record the deformation values ​​under various loads under the full confining pressure condition ( mm) are shown in Table 5.

[0089] Table 5 Deformation table of original data of full confining pressure test results

[0090]

[0091]

[0092] Figure 9 The deformation of measuring points B1, B2, and B3 is shown as a function of load.

[0093] (1) The measuring point B1 is located at the front of the side, and its maximum deformation value is 2.441 mm, which is lower than the maximum deformation of the plate and shell; the residual value is 0.485 mm, which meets the deformation requirements.

[0094] (2) The measuring point B2 is located in the middle of the top surface, where the maximum deformation of the cabin occurs. Its value is 1.426 mm, which is lower than the maximum deformation of the plate and shell; the residual value is 0.298 mm, which meets the deformation requirements.

[0095] (3) The maximum deformation of the measuring point at the rear of the top surface of B3 is 0.845 mm, which is lower than the maximum deformation of the plate and shell, and the residual value is -0.154 mm, which meets the deformation requirements.

[0096] The above results show that under full confining pressure conditions, the maximum deformation of the support cabin is less than the maximum deformation allowed by the material, and the main frame structure of the scaled model is safe under this condition.

[0097] Step S70: Execute the top static load test operation. Use the jack to apply a uniform static load vertically to the cabin to simulate the structural stress and deformation of the cabin under the top static load. According to the scaled model dimensional conversion relationship, the top load of the scaled model static load test is 0.5MPa, the maximum top load is 18.9KN, and the loading is divided into 5 levels. The specific loading levels are shown in Table 6:

[0098] Table 6 Top static load classification

[0099] Loading Level 1 2 3 4 5 6 Top load (KN) 11.3 13.2 15.1 17.0 18.9 0

[0100] Step S80: Record and analyze the test data after each load level stabilizes under the top surface static load condition, and record the strain values ​​(με) of the support cabin measuring points under each load level under the full confining pressure loading condition as shown in Table 7.

[0101] Table 7 Original data strain table of top static load test results

[0102]

[0103]

[0104] To visually display the stress values ​​at the measuring points under various loading conditions, the converted stress values ​​(MPa) are given in Table 8 based on Hooke's law. The actual strength of the support cabin steel is Q345 grade, with a yield strength of 345 MPa.

[0105] Table 8 Original data stress table of top static load test results

[0106]

[0107] Figure 10-12 The stress variation curves of the A1, A2, and A3 frame measuring points as a function of load are given. It can be seen from the figure that:

[0108] (1) For strain gauges 1-4 on frame A1, the maximum stress occurs at strain gauge 3, which is a compressive stress with a value of 458.1 MPa, which is greater than the yield strength of Q345r steel.

[0109] (2) For strain gauges 5-8 on frame A2, the maximum stress occurs at strain gauge 7, which is compressive stress with a value of 810.1 MPa, which is greater than the yield strength of Q345r steel.

[0110] (3) For strain gauges No. 9-12 on the A3 frame, the maximum stress occurs at strain gauge No. 11, which is compressive stress with a value of 227.6 MPa, which is lower than the yield strength of Q345r steel.

[0111] These results indicate that under static load conditions on the support module, the maximum stress at some measuring points exceeded the allowable stress of the material. This may be due to deformation of the uniform plate structure, which resulted in concentrated loads. However, the support module structure did not suffer significant damage or instability, and the scaled model's main frame structure was safe under these conditions.

[0112] Step S90: Record the deformation values ​​(mm) at various levels of load under the top static load condition as shown in Table 9.

[0113] Table 9 Original data deformation table of top static load test results

[0114]

[0115] Figure 13 The deformation of measuring points B1, B2, and B3 is shown as a function of load.

[0116] (1) The measuring point B1 is located at the front of the side, and the maximum deformation value is -0.840 mm, which is lower than the maximum deformation of the plate and shell; the residual value is -0.029 mm, which meets the deformation requirements.

[0117] (2) The measuring point B2 is located in the middle of the top surface, which is the point of maximum deformation of the cabin. Its maximum deformation value is 2.849 mm, which is lower than the maximum deformation of the plate and shell; the residual value is 0.542 mm, which meets the deformation requirements.

[0118] (3) The measuring point B3 is located at the rear of the top surface. The maximum deformation value is 1.564 mm, which is lower than the maximum deformation of the plate and shell. The residual value is 0.180 mm, which meets the deformation requirements.

[0119] The above results show that under the top static load condition, the maximum deformation of the support cabin is less than the maximum deformation allowed by the material, and the main frame structure of the scaled model is safe under this condition.

[0120] Step S100: The test conclusion is that the stress of the scaled model is greater than the yield strength of the material at some measuring points, but no local yielding or instability of the rods occurs during the entire test process; the deformation is less than the maximum deformation of the cabin plate and shell, and no damage occurs. In summary, the overall design of the cabin structure is safe and reliable.

[0121] The above content is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, several simple deductions and substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the scope of protection of the present invention.

Claims

1. A method for testing the compressive performance of a safety cabin based on an equivalent scale model, characterized in that: The following steps are involved: Step 1: Determine the scale ratio based on dimensional analysis and construct a scale model of the support cabin; Step 2: applying a full confining pressure condition simulating surrounding rock pressure and a top static load condition simulating collapse vertical pressure to the scaled model through a loading device; Step 3: Arrange multiple strain measurement points in the key stress-bearing areas of the model frame, and arrange deformation measurement points at multiple locations on the cabin surface; Step 4: applying load to the scaled model using a graded loading and unloading mode; Step 5: Collect data through the strain measurement device and the displacement measurement device, analyze the stress distribution and structural deformation based on the strain data and deformation data, and evaluate the pressure resistance and safety of the support cabin.

2. The method for testing the pressure resistance of a safety cabin according to claim 1, characterized in that: In step 2, the loading device includes at least one top jack and at least one side jack, each jack being in contact with the scaled model through a uniform force plate to apply a uniform load; The comprehensive confining pressure working condition is achieved by the synchronous application of force by the top jack and the side jack; The top static load condition is achieved only by applying force from the top surface jack.

3. The method for testing the pressure resistance of a safety cabin according to claim 1, characterized in that: In step 3, the strain measuring points are arranged at the stress concentration areas of the frame based on the finite element stress analysis results, including the mid-span positions of the transverse stiffeners or the frame connection nodes.

4. The method for testing the pressure resistance of a safety cabin according to claim 1, wherein: In step 5, the data analysis includes: Eliminate systematic errors and singular terms in collected data; Determine the linear response range of the structure through stress-strain curve; The residual deformation rate is calculated to evaluate the elastic recovery capacity of the structure.

5. The method for testing the pressure resistance of a safety cabin according to claim 1, characterized in that: In step 1, the frame structure of the scaled model is welded with high-strength steel and includes transverse reinforcement ribs and longitudinal support beams.

6. The method for testing the pressure resistance of a safety cabin according to claim 1, characterized in that: In step 5, the safety assessment includes: Verify that the stress of the model frame under maximum load is lower than the material yield strength; Verify that the local deformation under maximum load is less than a predetermined threshold.

7. The method for testing the pressure resistance of a safety cabin according to claim 1, characterized in that: Step 5 also includes generating stress distribution diagrams and compressive performance evaluation reports of measuring points under different working conditions.

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