Lateral non-uniform load pressurization test device and method

Abstract

The invention provides a lateral non-uniform load pressurization test device and method, and belongs to the technical field of lateral non-uniform load pressurization tests. The technical problem to be solved is to provide the lateral non-uniform load pressurization test device and the lateral non-uniform load pressurization test method. According to the technical scheme, all rigid pressing strips are arranged according to the load pressure distribution form of the block test piece, the arranged rigid pressing strips are fixed through rigid pressing strip clamps, and the induction ends of all the rigid pressing strips make contact with the block test piece; the detection ends of the rigid pressing strips make contact with the corresponding cams respectively, the cams are installed on the same transmission shaft through couplings, the couplings can conduct fine adjustment on the installation angles of the cams on the transmission shaft, the transmission shaft and an output shaft of a motor are coaxially arranged, and the control end of the motor is connected with a controller through a wire. The lateral non-uniform load pressurization test device is applied to lateral non-uniform load pressurization tests.

Description

Technical Field

[0001] The invention provides a lateral non-uniformly distributed load pressurization test device and method, belonging to the technical field of lateral non-uniformly distributed load pressurization test. Background Art

[0002] In the process of coal mining, the excavation of working faces and tunnels causes the formation of local goafs underground, the original stress state is destroyed, and the stress in the surrounding rock is redistributed, increasing the risk of tunnel damage and instability. The tunnel surrounding rock is a natural heterogeneous anisotropic material. Its strength is affected by its own components and structure, and is mainly affected by the ground stress environment. In actual engineering, the surrounding rock undergoes a complete mining dynamics process from original rock stress, axial stress increase to the transfer of stress field to the inside, resulting in complex and changeable surrounding rock stress underground. In this process, the stress state and deformation behavior of the surrounding rock have an important impact on the safe production of coal mines. Especially under deep mining conditions, the superposition of high ground stress and mining stress makes the stability problem of the surrounding rock more prominent. The distribution and size of lateral stress have a direct impact on the deformation and damage of the surrounding rock. In some cases, the increase of lateral stress may lead to excessive deformation and rapid convergence of the surrounding rock, especially when the mining depth increases. Therefore, it is particularly important to study the lateral stress non-uniform load test, which can better understand the mechanical response of the surrounding rock under the action of non-uniform load and provide a scientific basis for tunnel support design and surrounding rock control.

[0003] At present, there are few studies on the methods of applying non-uniform loads. The indoor loading equipment used mostly relies on multi-axis hydraulic cylinders, which makes it difficult to achieve non-uniform load application with multiple stress gradient levels, or the test conditions are relatively idealized, difficult to put into practice, and have low operability. Therefore, it is very important to study a non-uniform load pressurization test device with a simple structure, strong operability, and the ability to adjust and apply multiple stress gradient levels. According to the test results, the support structure can be designed more effectively, coal mine accidents can be reduced, and the environment can be protected. Summary of the invention

[0004] In order to overcome the deficiencies in the prior art, the present invention aims to solve the technical problem of providing a lateral non-uniformly distributed load pressurization test device and method.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a lateral non-uniform load pressure test device, comprising a plurality of rigid pressure strips, each rigid pressure strip is arranged according to the load pressure distribution form of the block specimen, the arranged rigid pressure strips are fixed by a rigid pressure strip clamp, and the sensing end of each rigid pressure strip is in contact with the block specimen;

[0006] The detection end of each rigid pressure strip is in contact with the corresponding cam, each cam is installed on the same transmission shaft through a coupling, and the coupling can fine-tune the installation angle of the cam on the transmission shaft. The transmission shaft is coaxially arranged with the output shaft of the motor, and the control end of the motor is connected to the controller through a wire;

[0007] A stress sensor is also provided at the sensing end of each rigid layering strip, and the signal output end of the stress sensor is connected to the controller through a wire to monitor the change of the non-uniform load pressure applied to the surface of the block specimen in real time;

[0008] The block specimen is specifically installed and fixed on an axial loading device.

[0009] A method for conducting a test using a lateral non-uniform load pressure test device comprises the following test steps:

[0010] Step 1: Determine the distribution form of the load pressure to be applied to the block specimen according to the test requirements;

[0011] Step 2: adjusting the distribution sequence of the rigid pressure strips according to the distribution form of the load pressure, and adaptively adjusting the installation position and action angle of the cam to apply the corresponding non-uniform load pressure;

[0012] Step 3: Calculate the input torque of the transmission shaft according to the non-uniform load pressure to be applied;

[0013] Step 4: Fine-tune the angle of the cam through the coupling set between the cam and the transmission shaft, accurately control the positional relationship between the cam and the rigid pressure strip, and accurately input the normal load pressure;

[0014] Step 5: By setting a stress sensor on the surface of the rigid pressure strip, the changes in the non-uniform load pressure applied to the surface of the block specimen are monitored in real time, and the changes in the load pressure are fed back to the controller, which adjusts the input torque of the transmission shaft in real time to achieve trapezoidal load control.

[0015] The specific method for calculating the input torque of the transmission shaft in step 3 is:

[0016] Analysis of the forces acting on a single cam:

[0017] Define the force exerted by the cam on the surface of the rigid strip as F n , F n Decomposed into the component force F perpendicular to the surface of the rigid layering strip y and the component force F parallel to the surface of the rigid strip x , the action angle is α, then the calculation formula of the vertical load pressure on the rigid layering strip is:

[0018] F y =Fn cosα;

[0019] Determine the force F exerted by the cam on the surface of the rigid strip n The relationship between the cam action radius r and the input torque of the transmission shaft is defined as T, and the calculation formula of the cam input force is:

[0020] F n =T / r;

[0021] Analysis of the forces acting on multiple cams:

[0022] Use the same style shape for all cams and define:

[0023] The effective radius of each cam is:

[0024] r1, r2, ..., r k (r1<r2<……<r k );

[0025] The action angles are:

[0026] α1, α2, ..., α k (α1<α2<……<α k );

[0027] The torque of the transmission shaft is T, and the calculation formulas of the component forces of each cam perpendicular to the surface of the rigid pressure strip are:

[0028]

[0029] The specific method for implementing trapezoidal load control in step 5 is:

[0030] Define the cross-sectional length of the rigid layer as a, the width as b, and the cross-sectional area S = a × b. To achieve a trapezoidal load of σ = kx + c, the following calculation formula must be satisfied:

[0031]

[0032] That is, the minimum load level of the rigid layer is c, and the stress gradient variation coefficient is k, which is specifically achieved by changing a single variable of the cam action radius or action angle, or by coupling changes of the two variables;

[0033] Specifically, according to the horizontal stress at different positions, the cam action radius or action angle is adjusted to achieve the target non-uniform load pressure application, thereby constructing the non-uniform load function F(x). The calculation formula for the stress applied at different gradient positions is:

[0034]

[0035] The specific method of applying the corresponding non-uniform load pressure in step 2 includes three adjustment methods:

[0036] Keep the cam action radius unchanged, change the action angle, and achieve non-uniform load pressure application;

[0037] Keep the cam action angle unchanged, change the action radius, and achieve non-uniform load pressure application;

[0038] By changing the cam action angle and radius at the same time, the application of complex non-uniform load pressure can be achieved through the coupling effect of the two factors.

[0039] The beneficial effects of the present invention compared with the prior art are as follows: the present invention proposes a lateral non-uniform load pressurization test method, which drives multiple cams to rotate through a single transmission shaft, and based on the different action radius or action angle of each cam, realizes the accurate application of the lateral non-uniform load on the test piece. The method can change the cam shape or adjust the action radius and action angle with the rigid pressure strip, and the height of each rigid pressure strip to achieve the change of the input load, and has the advantages of simple operation, low cost, and easy promotion, and effectively solves the difficulties of the prior art in applying lateral non-uniform loads at multiple stress gradient levels. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present invention will be further described below in conjunction with the accompanying drawings:

[0041] Figure 1 This is a rendering of the force analysis of a single cam and a rigid pressure strip according to the present invention;

[0042] Figure 2 A front view of stacking a plurality of rigid pressure strips of different lengths according to the present invention;

[0043] Figure 3 A top view of stacking a plurality of rigid pressure strips of different lengths according to the present invention;

[0044] Figure 4 This is a front view of the present invention using the same transmission shaft to fix multiple cams (the cams have different action angles);

[0045] Figure 5 This is a top view of the present invention using the same transmission shaft to fix multiple cams (the cams have different action angles);

[0046] Figure 6 It is a front view of the rigid pressure strip and the cam of the present invention after the action;

[0047] Figure 7 It is a top view of the rigid pressure strip and the cam of the present invention after the action;

[0048] Figure 8This is a diagram showing the installation effect of a block specimen in a non-uniform load pressure test device according to the present invention;

[0049] Fig. 9 The simplified model and discrete schematic diagram of the trapezoidal load distribution of the present invention with the expression σ=kx+c;

[0050] Fig.10 The simplified model and continuous schematic diagram of the present invention for the linear non-uniformly distributed load expressed as σ=kx+c;

[0051] Fig.11 It is a simplified model and discrete schematic diagram of a nonlinear non-uniformly distributed load expressed as F(x) in the present invention;

[0052] Fig.12 It is a simplified model and continuous schematic diagram of a nonlinear non-uniformly distributed load expressed as F(x) in the present invention;

[0053] In the figure: 1 is a rigid pressure strip, 2 is a cam, 3 is a coupling, 4 is a transmission shaft, 5 is a 1# rigid pressure strip, 6 is a 2# rigid pressure strip, 7 is a k# rigid pressure strip, 8 is a 1# cam, 9 is a 2# cam, 10 is a k# cam, 11 is a block specimen, 12 is an axial loading device, 13 is a rigid pressure strip fixture, and 14 is a stress sensor. DETAILED DESCRIPTION

[0054] like Figures 1 to 12 As shown, the present invention realizes the test of applying lateral non-uniform load to the block specimen by setting a single transmission shaft and a multi-cam structure. The provided test device includes a plurality of rigid beading strips 1, each of which is arranged according to the load pressure distribution form of the block specimen 11. The arranged rigid beading strips 1 are fixed by a rigid beading strip fixture 13, and the sensing end of each rigid beading strip 1 is in contact with the block specimen 11;

[0055] The detection end of each rigid pressure strip 1 is in contact with the corresponding cam 2, and each cam 2 is installed on the same transmission shaft 4 through a coupling 3. The coupling 3 can fine-tune the installation angle of the cam 2 on the transmission shaft 4. The transmission shaft 4 is coaxially arranged with the output shaft of the motor, and the control end of the motor is connected to the controller through a wire;

[0056] A stress sensor 14 is also provided at the sensing end of each rigid layering strip 1, and the signal output end of the stress sensor 14 is connected to the controller through a wire, so as to monitor the change of the non-uniform load pressure applied to the surface of the block specimen 11 in real time;

[0057] The block specimen 11 is specifically installed and fixed on the axial loading device 12 .

[0058] The present invention also provides a test method for lateral non-uniform load pressurization based on the test device, and the main steps include:

[0059] Step 1: Determine the distribution form of the load to be applied;

[0060] Step 2: Adjust the distribution sequence of the rigid pressure strips according to the distribution form of the load, and then adjust the installation position and action angle of the cam;

[0061] Step 3: Calculate the input torque of the transmission shaft according to the non-uniform load to be applied;

[0062] Step 4: The cam angle can be fine-tuned through the coupling between the cam and the transmission shaft to accurately control the position relationship between the cam and the rigid pressure strip and realize accurate input of the normal load;

[0063] Step 5: Use the rigid pressure strip surface stress sensor to monitor the non-uniform load applied on the surface of the object in real time, form a feedback system, and adjust the input torque of the transmission shaft in real time to ensure the accuracy of the non-uniform load applied.

[0064] The calculation process involved in the above test steps is as follows:

[0065] (1) Figure 1 As shown, when performing force analysis on a single cam:

[0066] Assume that the force exerted by the cam on the surface of the rigid strip is F n , F n Decomposed into the component force F perpendicular to the surface of the rigid layering strip y and the component force F parallel to the surface of the rigid strip x , the action angle is α, it can be known that the vertical load F on the rigid layering strip y =F n cosα;

[0067] The force F exerted by the cam on the surface of the rigid pressure strip n It is related to the cam action radius r and the input torque of the transmission shaft. If the input torque of the transmission shaft is T, then the cam input force F n =T / r.

[0068] (2) Figure 6 and Figure 7 As shown, when performing force analysis on multiple cams:

[0069] For the convenience of explanation, all cams in the present invention adopt the same style and shape (the actual cam shape can be adjusted and changed according to the requirements of the applied non-uniform load). Assume that the effective radius of each cam is r1, r2, ..., r k (r1<r2<……<r k), the action angles are α1, α2, ..., α k (α1<α2<……<α k ), the transmission shaft torque is T, then the components of the forces of each cam perpendicular to the surface of the rigid pressure strip are:

[0070]

[0071] (3) Fig. 9 and Fig.10 As shown, assuming that the length of the rigid layering section is a, the width is b, and the cross-sectional area is S = a × b, if the trapezoidal load of σ = kx + c is to be achieved, the following formula is established:

[0072]

[0073] That is, the minimum load level of the rigid pressure strip is c, and the stress gradient variation coefficient is k. The above load realization method can be realized by changing the cam action radius or action angle as a single variable, or by coupling the two variables.

[0074] (4) The application of complex non-uniform loads requires adjusting the cam action radius or action angle according to the horizontal stress at different positions to achieve the target non-uniform load application, thereby constructing the non-uniform load function F(x). The stress application at different gradient positions is achieved according to the following formula:

[0075]

[0076] The non-uniform load applied on the surface of the object is monitored in real time by the surface stress sensor of the rigid pressure strip, forming a feedback system, which can fine-tune the cam action radius or action angle in real time to ensure the accuracy of the applied non-uniform load.

[0077] The above-mentioned cam action radius and action angle can be achieved not only by adjusting the height of the rigid pressure strip, but also by changing the cam pattern shape, or by combining the above-mentioned multivariable factors.

[0078] In order to prevent the rigid pressure strip from yielding during the loading process, when the rigid pressure strip is selected in the step 2, the compressive strength of the rigid pressure strip shall not be less than twice the required load, and the rigidity value of the rigid strip shall be consistent; the roughness of the rigid pressure strip and the cam shall not be greater than Ra0.40, and the dimensional error shall not be greater than 1%; the thickness of the cam is slightly smaller than the thickness of the rigid pressure strip; and a stress sensor shall be arranged on the surface of the rigid pressure strip.

[0079] When implementing non-uniform load, step 2 is mainly implemented through three adjustment methods: (1) keeping the cam action radius unchanged and changing the action angle to achieve non-uniform load application; (2) keeping the cam action angle unchanged and changing the action radius to achieve non-uniform load application; (3) changing the cam action angle and radius at the same time, through the coupling effect of the two factors, complex non-uniform load application can be achieved.

[0080] In addition, the method of changing the cam action radius and action angle in the above content is not limited to being achieved through the linkage shaft between the cam and the transmission shaft, but can also be achieved by changing the size and shape of the cam and the height of the rigid pressure strip, thereby enabling multi-variable factor coupling to achieve more complex non-uniform load application.

[0081] The test device provided by the present invention drives multiple cams to rotate by setting a single transmission shaft, and realizes the pressurization of non-uniform loads to the side of the test piece by adjusting the action radius and action angle of the cam and the rigid pressure strip. The same effect can be achieved by changing the shape of the cam. During the test, the action radius and action angle of the cam can be changed by adjusting the height of each rigid pressure strip. In addition, the effect of complex non-uniform load pressurization can be further achieved through the coupling of multiple factors.

[0082] The present invention can achieve non-uniform load pressurization by setting up a single power transmission system, and can achieve multi-gradient horizontal non-uniform load stress application by changing the number of cams and the number of rigid pressure strips. The entire test method is simple and easy to operate, has low dependence on the power transmission system, has low equipment performance requirements, and is easy to promote and use.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A lateral non-uniform load pressure test device, characterized in that: It comprises a plurality of rigid beading strips (1), each rigid beading strip (1) is arranged according to the load pressure distribution form of the block specimen (11), the arranged rigid beading strips (1) are fixed by a rigid beading strip clamp (13), and the sensing end of each rigid beading strip (1) is in contact with the block specimen (11); The detection end of each rigid pressure strip (1) is in contact with the corresponding cam (2), each cam (2) is installed on the same transmission shaft (4) through a coupling (3), and the coupling (3) can fine-tune the installation angle of the cam (2) on the transmission shaft (4). The transmission shaft (4) is coaxially arranged with the output shaft of the motor, and the control end of the motor is connected to the controller through a wire; A stress sensor (14) is also provided at the sensing end of each rigid pressure strip (1), and a signal output end of the stress sensor (14) is connected to a controller via a wire, so as to monitor in real time the change of the non-uniform load pressure applied to the surface of the block specimen (11); The block test piece (11) is specifically installed and fixed on the axial loading device (12).

2. The method for conducting a test using a lateral non-uniform load pressure test device according to claim 1, characterized in that: The test steps include the following: Step 1: Determine the distribution form of the load pressure to be applied to the block specimen (11) according to the test requirements; Step 2: adjusting the distribution sequence of the rigid pressure strip (1) according to the distribution form of the load pressure, and adaptively adjusting the installation position and action angle of the cam (2) to apply the corresponding non-uniform load pressure; Step 3: Calculate the input torque of the transmission shaft (4) according to the non-uniform load pressure to be applied; Step 4: fine-tune the angle of the cam (2) through the coupling (3) provided between the cam (2) and the transmission shaft (4), accurately control the action position relationship between the cam (2) and the rigid pressure strip (1), and accurately input the normal load pressure; Step 5: By setting a stress sensor (14) on the surface of the rigid pressure strip (1), the change of the non-uniform load pressure applied to the surface of the block specimen (11) is monitored in real time, and the change of the load pressure is fed back to the controller, and the controller adjusts the input torque of the transmission shaft (4) in real time to achieve trapezoidal load control.

3. The method for conducting a test using a lateral non-uniform load pressure test device according to claim 2, characterized in that: The specific method for calculating the input torque of the transmission shaft in step 3 is: Analysis of the forces acting on a single cam: Define the force exerted by the cam on the surface of the rigid strip as F n , F n Decomposed into the component force F perpendicular to the surface of the rigid layering strip y and the component force F parallel to the surface of the rigid strip x , the action angle is α, then the calculation formula of the vertical load pressure on the rigid layering strip is: F y =F n cosα; Determine the force F exerted by the cam on the surface of the rigid strip n The relationship between the cam action radius r and the input torque of the transmission shaft is defined as T, and the calculation formula of the cam input force is: F n =T / r; Analysis of the forces acting on multiple cams: Use the same style shape for all cams and define: The effective radius of each cam is: r1、r2、……、r k (r1＜r2＜……＜r k )； The action angles are: α1、α2、……、α k (α1＜α2＜……＜α k )； The torque of the transmission shaft is T, and the calculation formulas of the component forces of each cam perpendicular to the surface of the rigid pressure strip are:

4. The method for conducting a test using a lateral non-uniform load pressure test device according to claim 3, characterized in that: The specific method for implementing trapezoidal load control in step 5 is: Define the cross-sectional length of the rigid layer as a, the width as b, and the cross-sectional area S = a × b. To achieve a trapezoidal load of σ = kx + c, the following calculation formula must be satisfied: That is, the minimum load level of the rigid layer is c, and the stress gradient variation coefficient is k, which is specifically achieved by changing a single variable of the cam action radius or action angle, or by coupling changes of the two variables; Specifically, according to the horizontal stress at different positions, the cam action radius or action angle is adjusted to achieve the target non-uniform load pressure application, thereby constructing the non-uniform load function F(x). The calculation formula for the stress applied at different gradient positions is:

5. The method for conducting a test using a lateral non-uniform load pressure test device according to claim 4, characterized in that: The specific method of applying the corresponding non-uniform load pressure in step 2 includes three adjustment methods: Keep the cam action radius unchanged, change the action angle, and realize the application of non-uniform load pressure; Keep the cam action angle unchanged, change the action radius, and achieve non-uniform load pressure application; By changing the cam action angle and radius at the same time, the application of complex non-uniform load pressure can be achieved through the coupling effect of the two factors.

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