Mechanical and ground stress combined loading device based on underground structural member and loading method of mechanical and ground stress combined loading device

Abstract

The invention discloses a mechanical and ground stress combined loading device based on an underground structural member and a loading method thereof, and relates to the technical field of explosion tests. The dynamic response problem of an existing underground structure under the coupling action of soil stress and explosive load is solved. The device comprises an explosive load applying system and a surrounding stress applying system. The explosion load applying system comprises a lifting mechanism, a guide rail, a drop hammer and a test model; the confining stress applying system applies horizontal confining pressure and vertical confining pressure to the test model; the lifting mechanism drives the drop hammer to realize lifting at different heights; the drop hammer applies a vertical uniformly-distributed explosion-like load to the test model; an enclosure structure is arranged at the top of the test model, and sandy soil is arranged in the enclosure structure; a cover plate is arranged at the top of the enclosure structure, a cushion layer is arranged on the cover plate, and a buffer is arranged on the cushion layer; strain gauges are arranged on the surface of the bottom of the test model; and pressure sensors are arranged in the sand dispersion layer and on the inner surface of the test structure model. The method is suitable for underground structure anti-explosion overall effect model test research.

Description

Technical Field

[0001] The invention relates to the technical field of explosion testing, and in particular to a combined loading device and a loading method thereof based on mechanical and ground stress of underground structural components. Background Art

[0002] The ground impact load is the main load considered for underground structures under the action of explosion. The ground impact load generated by chemical explosion generally acts only within a certain range, and its wavefront is non-planar; the action time is short, generally a few milliseconds to tens of milliseconds; the peak pressure decays rapidly with the increase of propagation depth; for unsaturated soil, the ground impact load is a pressure wave with a certain pressure rise time, and the pressure rise time continues to lengthen with the increase of propagation depth, and the waveform gradually slows down and lengthens with the increase of depth.

[0003] At present, the commonly used method to test the overall explosion resistance of underground structures is mainly field explosion tests. For small underground structures, prototype tests can be adopted; for large underground structures, due to funding constraints, scaled tests are generally adopted. Explosion tests have many problems such as high safety risks, long preparation cycles, high test costs, and difficult measurement technologies. They are generally used for verification tests and are difficult to meet for research that requires a large number of tests to explore laws. In actual environments, underground structures will be subject to stress from the soil. Different geological structures will also affect the distribution of geostress in the structure. Vertical geostress is related to the depth of the structure. Therefore, how to effectively use non-explosive methods to apply simulated explosion loads and how to simulate the state of underground structures under geostress are issues that need to be urgently addressed in the current research field of underground protective structures.

[0004] The test technology of applying explosion-like loads by non-explosive means mainly involves drop hammer impact testers and hydraulic servo-driven explosion simulators. Among them, the drop hammer impact tester includes elements such as a bench, a lifting mechanism, a drop hammer, a guide rail, a foundation, and a control and measurement system. Its principle is mainly to use the gravitational potential energy to impact the specimen to generate an impact load. Summary of the invention

[0005] The present invention mainly aims at the dynamic response problem of existing underground structures under the coupling of soil stress and explosion load, and proposes a mechanical loading and ground stress coupling test device according to the working principle of the drop hammer impact test equipment and the liquid pressurization system.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a combined loading device based on mechanical and ground stress of underground structural components, the device comprising an explosion load application system and a confining stress application system;

[0008] The explosion load application system includes a lifting mechanism, a guide rail, a drop hammer and a test model;

[0009] The confining stress application system is used to apply horizontal confining pressure and vertical confining pressure to the test model;

[0010] The lifting mechanism is used to drive the drop hammer to achieve lifting at different heights under the action of the guide rail;

[0011] The bottom surface of the drop hammer is a plane, which is used to apply a vertical uniformly distributed explosion-like load to the test model;

[0012] A retaining structure is arranged on the top of the test model, and sand is arranged in the retaining structure to form a sand dispersion layer;

[0013] The top of the enclosure structure is provided with a cover plate, the upper part of the cover plate is provided with a cushion layer, and the upper part of the cushion layer is provided with a buffer;

[0014] The surface of the bottom of the test model is provided with a strain gauge;

[0015] Pressure sensors are arranged in the sand dispersion layer and on the inner surface of the test structure model.

[0016] Furthermore, in a preferred embodiment, the bottom area of ​​the drop weight is larger than the top area of ​​the test model.

[0017] Furthermore, in a preferred embodiment, the device further comprises a secondary impact protection device;

[0018] The anti-secondary impact device is used to lock the drop weight after the first impact.

[0019] Furthermore, in a preferred embodiment, the device further comprises a broadband strain gauge and a transient recorder;

[0020] The broadband strain gauge is connected to the pressure sensor, and the transient recorder is connected to the strain gauge.

[0021] The present invention also provides a loading method based on the above-mentioned underground structural member mechanical and ground stress combined loading device, the method comprising the following steps:

[0022] Step S1: a protective layer is set above the test model, and whether a secondary impact protection device is provided;

[0023] Step S2: If available, the pressure sensor is arranged on the outer side wall of the top plate of the test model, and the side wall and the top of the pressure sensor are in contact with the sand;

[0024] Step S3: If not available, a buffer is added between the cover plate and the sand layer after the pressure sensor is installed;

[0025] Step S4: Calculate the lifting height of the drop weight after setting the parameters;

[0026] Step S5: raising the drop hammer to a preset position according to the lifting height, connecting the pressure sensor and the strain gauge to the broadband strain gauge and the transient recorder, performing drop hammer impact, and obtaining a pressure waveform diagram and a strain waveform diagram of the test model;

[0027] Step S6: Compare the pressure waveform with the preset waveform to determine the relationship between the pressure waveform and the preset waveform. If they match, the pressure waveform debugging is completed and the underground structure model test is started. Otherwise, the drop weight lifting height and the cushion layer height are changed and the process returns to step S5.

[0028] Step S7: applying confining stress to the test model, and controlling the magnitude of the load to be applied through a pressure sensor.

[0029] Furthermore, there is a preferred embodiment, the above-mentioned method for calculating the height of the drop hammer is:

[0030] Step S1: Calculate the stress generated on the contact surface between the falling weight and the cushion layer:

[0031] Step S2: One-dimensional elastic waves are transmitted from the cushion layer to the cover plate. Based on the stress generated on the contact surface between the drop weight and the cushion layer, the stress σ transmitted to the cover plate is calculated. T1 ;

[0032] Step S3: The one-dimensional elastic wave is transmitted from the cover plate to the sand layer. Based on the stress transmitted to the cover plate, the stress σ transmitted to the sand layer is calculated. T2 ;

[0033] Step S4: The lifting height h of the drop hammer is:

[0034]

[0035] Among them, ρ1 is the density of the drop hammer material, c1 is the wave velocity of the drop hammer material, ρ2 is the density of the cushion material, c2 is the wave velocity of the cushion material, ρ3 is the density of the cover material, c3 is the wave velocity of the cover material, ρ4 is the density of the sand material, and c4 is the wave velocity of the sand material.

[0036] Furthermore, there is a preferred embodiment, if there is no cushion layer, the lifting height h of the above-mentioned drop hammer is:

[0037]

[0038] The method for calculating the height of the drop weight lifting of the present invention can be implemented entirely by computer software. Therefore, correspondingly, the present invention also provides a system for calculating the height of the drop weight lifting, the system comprising a storage device for executing the following steps:

[0039] Step 1: Calculate the stress generated on the contact surface between the drop weight and the cushion:

[0040] Step 2: One-dimensional elastic waves are transmitted from the cushion to the cover plate. Based on the stress generated on the contact surface between the drop weight and the cushion, the stress σ transmitted to the cover plate is calculated. T1 ;

[0041] Step 3: One-dimensional elastic waves are transmitted from the cover plate to the sand layer. Based on the stress transmitted to the cover plate, the stress σ transmitted to the sand layer is calculated. T2 ;

[0042] Step 4: The lifting height h of the drop hammer is:

[0043]

[0044] Among them, ρ1 is the density of the drop hammer material, c1 is the wave velocity of the drop hammer material, ρ2 is the density of the cushion material, c2 is the wave velocity of the cushion material, ρ3 is the density of the cover material, c3 is the wave velocity of the cover material, ρ4 is the density of the sand material, and c4 is the wave velocity of the sand material.

[0045] The present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the above-mentioned method for calculating the height of the falling hammer is executed.

[0046] The present invention also provides a computer device, which includes a memory and a processor, wherein the memory stores a computer program, and when the processor runs the computer program stored in the memory, the processor executes the above-mentioned method for calculating the lifting height of the falling hammer.

[0047] The beneficial effects of the present invention are:

[0048] 1. The present invention proposes a combined loading device based on mechanical and ground stress of underground structural components. By arranging a hydraulic buffer on the device, the residual energy after the drop hammer impacts the sample can be better absorbed to prevent secondary impact.

[0049] Furthermore, the experimental device can better meet the needs of model test research on the overall explosion resistance of underground structures. It has the advantages of easy operation, low cost, and repeatability, and provides a practical means for related principle test research.

[0050] 2. The present invention proposes a combined loading method based on mechanical and geostress of underground structural components, which can create a real geostress environment and meet the research on the failure process of underground structures under static confining pressure and explosion loads. This method can produce vertically uniformly distributed explosion loads and geostresses, and has the advantages of easy operation, low cost, and repeatability, and can provide a practical means for related principle experimental research.

[0051] Furthermore, the present invention can generate numerically uniformly distributed explosion loads to meet the needs of model test research on the overall anti-explosion effect of underground structures.

[0052] Furthermore, the present invention can create a static confining pressure environment to realize the study of failure modes of structures under the action of confining stress and explosion load.

[0053] Furthermore, the present invention has the advantages of low operating difficulty, low cost, and reusability.

[0054] The invention is suitable for the model test research of the overall anti-explosion effect of underground structures, helps to explore the law of dynamic load and structural response, and provides a practical means for the principle research of relevant underground protection engineering structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0056] Figure 1 It is a structural diagram of a combined loading device based on mechanical and ground stress of underground structural components according to the present invention;

[0057] Figure 2 It is a structural schematic diagram of the test model of the present invention;

[0058] Figure 3 It is a structural schematic diagram of the confining stress loading device of the present invention;

[0059] Figure 4 is a parameter setting diagram of the loading device of the present invention;

[0060] Figure 5 It is a flow chart of a method for combined loading of underground structural components based on mechanical and geostress according to the present invention. DETAILED DESCRIPTION

[0061] The specific implementation mode of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

[0062] Implementation method 1, see Figures 1 to 4To explain this embodiment, the present invention mainly aims at the dynamic response problem of existing underground structures under the coupling of soil stress and explosion load, and proposes a mechanical loading and ground stress coupling test device based on the working principle of the drop hammer impact test equipment and the liquid pressurization system. The device includes an explosion load application system and a confining stress application system;

[0063] The explosion load application system includes a lifting mechanism, a guide rail, a drop weight and a test model;

[0064] The confining stress application system is used to apply horizontal and vertical confining pressure to the test model;

[0065] The lifting mechanism is used to drive the drop hammer to achieve lifting at different heights under the action of the guide rail;

[0066] The bottom surface of the drop hammer is a flat surface, which is used to apply a vertical uniformly distributed explosion-like load to the test model;

[0067] A retaining structure is set on the top of the test model, and sand is set inside the retaining structure to form a sand dispersion layer;

[0068] A cover plate is provided on the top of the enclosure structure, a cushion layer is provided on the upper part of the cover plate, and a buffer is provided on the upper part of the cushion layer;

[0069] The surface at the bottom of the test model is provided with strain gauges;

[0070] Pressure sensors are installed in the sand dispersion layer and on the inner surface of the test structure model.

[0071] In practical application, the present embodiment is based on the structure of the underground structural member mechanical and ground stress combined loading device. Figure 1 As shown, it is mainly composed of an explosion load application system and a confining stress application system.

[0072] Among them, the explosive load application system mainly includes a drop hammer, a guide rail, a lifting mechanism, etc. The bottom surface of the drop hammer is a plane, and the length and width dimensions must be larger than the top dimensions of the test structure model, so as to accommodate the test structure model and the quasi-explosion load can be fully covered. In order to facilitate the vertical descent of the drop hammer to apply a vertical uniform load, the guide rail should be arranged vertically. In order to achieve adjustable impact energy, the lifting mechanism can lift the drop hammer to different heights, and the mass of the drop hammer can be adjusted within a certain range according to different test structures.

[0073] The buffer is a hydraulic buffer device. Since there is residual energy after the drop hammer impacts the specimen, and the residual energy is very large, in order to reduce the impact of the residual energy on the test results, a hydraulic buffer is installed above the cushion layer. The buffer stroke is 100mm, and each buffer device can absorb 15000J of energy.

[0074] The overall structure of the test model is as follows Figure 2As shown, wherein: a retaining structure is arranged on the top of the test structure model, and sand is arranged in the retaining structure to form a sand dispersion layer; a cover plate is arranged on the top of the retaining structure, and a cushion layer is arranged on the upper part of the cover plate to change the peak value and pulse width of the impact, and a buffer layer is arranged on the lower part of the cover plate according to the situation, which can absorb the secondary impact energy of the drop hammer and reduce the impact on the test structure; a strain gauge is arranged on the inner wall of the top of the test structure, and the structural response of the test structure is collected through the strain gauge, and the strain of the structure under the impact force is analyzed to measure the deformation resistance of the test structure; a pressure sensor is arranged on the outer surface of the top of the test structure, and the vertical uniformly distributed impact load is detected by the pressure sensor. The pressure sensor and the strain gauge are connected to a broadband strain gauge and a transient recorder to record their waveforms, and the obtained waveform is compared with the preset waveform until the waveform obtained by the test is consistent with the preset.

[0075] Confining stress application system Figure 3 As shown, it is mainly composed of a hydraulic cylinder, a hydraulic jack, a base and a sensor.

[0076] The hydraulic cylinder is set on the inner wall of the main frame and connected to the hydraulic system device. Its main function is to provide power and apply horizontal and vertical confining pressure to the structure. The pressure sensor is connected to the experimental system. When the drop hammer system applies load, real-time pressure information can be measured on the surface of the structure.

[0077] The main parameters of the test device are:

[0078] The mechanical device used is mainly composed of a drop hammer, a limiter, a round tube guide rail, an electric hoist, a buffer, etc. Figure 4 As shown. The overall frame of the test device has a length, width and height of 2500mm×2500mm×4500mm, and the length and width of the rectangular bottom plane of the drop hammer are 640mm×440mm. Among them: the overall frame is mainly welded by 4 rectangular steel pipes and 16 I-beams, all of which are made of Q235; the drop hammer is composed of multiple weights, made of Q235 steel, and its impact height and mass can be freely adjusted; the guide rail is composed of 2 circular steel pipes with a diameter of 57mm, made of Q235 steel; the electric hoist is a DHS type chain electric hoist with a maximum lifting mass of 2t and a maximum lifting height of 8m; the limiter is a steel strand to ensure that the test personnel can work safely under the drop hammer; the hydraulic buffer device has a stroke of 100mm.

[0079] In summary, the combined loading device based on mechanical and geostress of underground structural components proposed in this embodiment can better absorb the residual energy after the drop hammer impacts the specimen by arranging a hydraulic buffer on the device to prevent secondary impact.

[0080] Furthermore, the experimental device can better meet the needs of model test research on the overall explosion resistance of underground structures. It has the advantages of easy operation, low cost, and repeatability, and provides a practical means for related principle test research.

[0081] Implementation Method 2: See Figure 5 This embodiment is described. This embodiment provides a loading method based on the underground structural member mechanical and ground stress combined loading device described in the first embodiment. The method includes the following steps:

[0082] Step S1: a protective layer is set above the test model, and whether a secondary impact protection device is provided;

[0083] Step S2: If available, the pressure sensor is arranged on the outer side wall of the top plate of the test model, and the side wall and the top of the pressure sensor are in contact with the sand;

[0084] Step S3: If not available, a buffer is added between the cover plate and the sand layer after the pressure sensor is installed;

[0085] Step S4: Calculate the lifting height of the drop weight after setting the parameters;

[0086] Step S5: raising the drop hammer to a preset position according to the lifting height, connecting the pressure sensor and the strain gauge to the broadband strain gauge and the transient recorder, and using the drop hammer to impact the test model to obtain a pressure waveform diagram and a strain waveform diagram of the test model;

[0087] Step S6: Compare the waveform obtained by the pressure sensor with the preset waveform to determine the relationship between the pressure waveform and the preset waveform. If the pressure waveform matches the preset waveform, the pressure waveform debugging is completed and the underground structure model test is started. Otherwise, the drop weight lifting height and the cushion layer height are changed and the process returns to step S5.

[0088] Step S7: applying confining stress to the test model, and controlling the magnitude of the load to be applied through a pressure sensor.

[0089] In practical application, the specific method of this embodiment is as follows: Figure 5 As shown:

[0090] (1) Determination of the test device and model. After the structural model is determined, various protective layers are set above the structural model, and it is determined whether the lifting mechanism used for the test has a secondary impact protection device. The protective layer includes a sand layer, a cover plate, and a cushion layer with adjustable thickness; the secondary impact protection device is mainly used to lock the drop hammer after the first impact to eliminate the waveform interference caused by the secondary impact of the drop hammer.

[0091] (2) Sensor arrangement. If the test lifting mechanism has been equipped with a secondary impact protection device, the pressure sensor is installed on the outer wall of the top plate of the structural model, and the side wall and top of the pressure sensor are in contact with the sand. Otherwise, a buffer layer should be added between the cover plate and the sand layer after the pressure sensor is installed. At the same time, multiple strain gauges are installed on the inner surface of the top plate of the structural model.

[0092] (3) Parameter setting. Determine the mass of the falling hammer m, the peak value of the stress wave in the soil σ T2max And parameters such as the wave impedance of each material, and calculate the lifting height h.

[0093] (4) Drop hammer impact. The drop hammer is raised to the preset position according to the lifting height h, and the pressure sensor and strain gauge are connected to the broadband strain gauge and transient recorder. After the structural model is impacted by the drop hammer, the pressure waveform and strain waveform of the structural model are obtained.

[0094] (5) Comparative analysis of the collected results. Compare the waveform obtained by the pressure sensor with the preset waveform to determine the relationship between the pressure waveform and the preset waveform, and ensure that the dynamic response of the structural model is within the allowable range through the strain gauge waveform to prevent structural damage. If the pressure waveform matches the preset waveform, the pressure waveform debugging is completed and the underground structure model test is started. Otherwise, change the drop hammer lifting height h and the cushion height H, and return to step (4). Among them, when the measured pressure waveform peak is less than the preset waveform peak, increase the drop hammer height h, and when the measured pressure waveform pulse width is less than the preset waveform pulse width, increase the cushion height H.

[0095] (6) Application of confining stress: By starting the hydraulic transmission device, the connected experimental device and then driving the hydraulic cylinder, confining stress is applied to the structure, wherein the load size to be applied can be controlled by a pressure sensor.

[0096] Furthermore, in actual applications, a control algorithm can be added to ensure that the drop hammer hits the structural model at a predetermined speed and position, achieve a specific impact waveform, and simulate the actual explosion load. At the same time, the drop hammer can be automatically stopped in abnormal situations to ensure safe operation.

[0097] The specific control algorithm is:

[0098] Step 1: Real-time data collection, using sensors to collect the position, velocity, acceleration and force of the falling weight;

[0099] Step 2: Data preprocessing, filtering and noise reduction of sensor data;

[0100] Step 3: Control strategy execution, using PID control, adaptive control or fuzzy logic control to accurately control the drop weight;

[0101] Step 4: waveform generation, adjusting the motion of the drop hammer according to the preset waveform to reproduce a specific impact waveform;

[0102] Step 5: Safety monitoring, real-time monitoring of force and speed, triggering the emergency stop mechanism when the safety threshold is exceeded;

[0103] Step 6: Feedback and adjustment, establish a feedback loop and adjust the control signal based on the sensor data.

[0104] In summary, the combined loading method based on mechanical and geostress of underground structural components proposed in this embodiment can create a real geostress environment, which meets the research on the failure process of underground structures under static confining pressure and explosion loads. This method can produce vertical uniformly distributed explosion loads and geostresses, and has the advantages of easy operation, low cost, and repeatability, which can provide practical means for related principle experimental research. Furthermore, it can also generate numerical uniformly distributed explosion loads to meet the needs of model test research on the overall effect of underground structure explosion resistance. Furthermore, it can also create a static confining pressure environment to realize the study of the failure mode of the structure under the action of confining stress and explosion load. It also has the advantages of low difficulty in operation, low cost, and reusability.

[0105] Implementation method 3: This implementation method specifically describes the method for calculating the height of the drop weight lifting described in the above implementation method 2.

[0106] Step S1: Calculate the stress generated on the contact surface between the falling weight and the cushion layer:

[0107] Step S2: One-dimensional elastic waves are transmitted from the cushion layer to the cover plate. Based on the stress generated on the contact surface between the drop weight and the cushion layer, the stress σ transmitted to the cover plate is calculated. T1 ;

[0108] Step S3: The one-dimensional elastic wave is transmitted from the cover plate to the sand layer. Based on the stress transmitted to the cover plate, the stress σ transmitted to the sand layer is calculated. T2 ;

[0109] Step S4: The lifting height h of the drop hammer is:

[0110]

[0111] Among them, ρ1 is the density of the drop hammer material, c1 is the wave velocity of the drop hammer material, ρ2 is the density of the cushion material, c2 is the wave velocity of the cushion material, ρ3 is the density of the cover material, c3 is the wave velocity of the cover material, ρ4 is the density of the sand material, and c4 is the wave velocity of the sand material.

[0112] In practical application, in order to form a specific vertical uniformly distributed explosion load, the height of the drop weight should be estimated. ijIt can be expressed as:

[0113] σ j1 =ρ1c1(V1-V) (1)

[0114] σ j1 =-ρ2c2V1 (2)

[0115] Where: ρ1 is the density of the falling hammer material; c1 is the wave velocity of the falling hammer material; ρ2 is the density of the cushion material; c2 is the wave velocity of the cushion material; ρ1c1 is the wave impedance of the falling hammer material; ρ2c2 is the wave impedance of the cushion material; V is the speed of the falling hammer hitting the cushion; V1 is the common movement speed of the medium on the contact surface, σ j1 In =-ρ2c2V1, “-” represents the downward wave.

[0116] Combining equations (1) and (2), σ ij It can be expressed as:

[0117]

[0118] One-dimensional elastic waves are transmitted from the cushion to the cover plate, with the propagation direction perpendicular to the interface, and the two media always keep in contact at the interface. According to the continuity condition and Newton's third law, the particle velocity and stress on both sides of the interface after the stress wave transmission and reflection should be equal. Therefore, there exists:

[0119] V I1 +V R1 =V T1 (4)

[0120] σ I1 +σ R1 =σ T1 (5)

[0121] Where: V I1 is the particle velocity of the incident wave; V R1 is the particle velocity of the reflected wave; V T1 is the particle velocity of the transmitted wave; σ I1 is the particle stress of the incident wave; σ R1 is the particle stress of the reflected wave; σ T1 is the particle stress of the transmitted wave.

[0122] According to the stress σ generated on the contact surface of the cushion j1 , ignoring the attenuation of stress in the cushion layer, let σ j1 =σ I1 , the stress σ transmitted to the cover can be calculated T1 for:

[0123]

[0124] In the formula: ρ3 is the density of the cover material; c3 is the wave velocity of the cover material; ρ3c3 is the wave impedance of the cover material.

[0125] A one-dimensional elastic wave is transmitted from the cover plate to the sand layer, and the propagation direction is perpendicular to the interface. The two media always keep in contact at the interface. According to the continuity condition and Newton's third law, the particle velocity and stress on both sides of the interface after the stress wave transmission and reflection should be equal. There exists:

[0126] V I2 +V R2 =V T2 (8)

[0127] σ I2 +σ R2 =σ T2 (9)

[0128] According to the stress σ transmitted to the cover T1 , without considering the attenuation of stress in the cover plate, let σ T1 =σ I2 , the stress σ transmitted to the sand layer can be calculated T2 for:

[0129]

[0130] Assume that a weight with mass m falls from a height h and hits the cover at a speed of V. According to the law of conservation of energy, The lifting height h of the drop hammer can be calculated as:

[0131]

[0132] Where: T2 The peak value σ T2max is the peak value of stress wave in sand; g is the acceleration due to gravity.

[0133] If there is no cushion layer, that is, ρ2c2=ρ3c3, the above formula degenerates into:

[0134]

[0135] Embodiment 4: The method for calculating the height of the drop weight lifting described in the above embodiment 3 can be implemented entirely by computer software. Therefore, this embodiment provides a system for calculating the height of the drop weight lifting, the system comprising a storage device, and the storage device performs the following steps:

[0136] Step 1: Calculate the stress generated on the contact surface between the drop weight and the cushion:

[0137] Step 2: One-dimensional elastic waves are transmitted from the cushion to the cover plate. Based on the stress generated on the contact surface between the drop weight and the cushion, the stress σ transmitted to the cover plate is calculated. T1 ;

[0138] Step 3: One-dimensional elastic waves are transmitted from the cover plate to the sand layer. Based on the stress transmitted to the cover plate, the stress σ transmitted to the sand layer is calculated. T2 ;

[0139] Step 4: The lifting height h of the drop hammer is:

[0140]

[0141] Among them, ρ1 is the density of the drop hammer material, c1 is the wave velocity of the drop hammer material, ρ2 is the density of the cushion material, c2 is the wave velocity of the cushion material, ρ3 is the density of the cover material, c3 is the wave velocity of the cover material, ρ4 is the density of the sand material, and c4 is the wave velocity of the sand material.

[0142] Embodiment 5: This embodiment provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the method for calculating the height of a drop weight as described in the above embodiment is executed.

[0143] Embodiment 6: This embodiment provides a computer device, which includes a memory and a processor, wherein the memory stores a computer program. When the processor runs the computer program stored in the memory, the processor executes the method for calculating the lifting height of the falling hammer described in the above embodiment.

[0144] A computer device is provided in this embodiment. The hardware device of this part is a general model and is not shown in the form of a diagram. The system includes a processor and a memory, wherein the processor and the memory can be connected via a bus or other means. The memory is a non-transitory computer-readable storage medium that can be used to store non-transitory software programs, non-transitory computer executable programs and modules, and corresponding program instructions / modules. The processor executes various functional applications and data processing of the processor by running the non-transitory software programs, instructions and modules stored in the memory, so as to realize the method and steps for calculating the drop weight lifting height in the above method embodiment.

[0145] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0146] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may be subject to various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the claims of the present invention.

Claims

1. A combined loading device based on mechanical and ground stress of underground structural components, characterized in that: Including explosion load application system and confining stress application system; The explosion load application system includes a lifting mechanism, a guide rail, a drop weight and a test model; The confining stress application system is used to apply horizontal and vertical confining pressure to the test model; The lifting mechanism is used to drive the drop hammer to achieve lifting at different heights under the action of the guide rail; The bottom surface of the drop hammer is a flat surface, which is used to apply a vertical uniformly distributed explosion-like load to the test model; A retaining structure is set on the top of the test model, and sand is set inside the retaining structure to form a sand dispersion layer; A cover plate is provided on the top of the enclosure structure, a cushion layer is provided on the upper part of the cover plate, and a buffer is provided on the upper part of the cushion layer; The surface at the bottom of the test model is provided with strain gauges; Pressure sensors are installed in the sand dispersion layer and on the inner surface of the test structure model.

2. The device for combined loading of underground structural components based on mechanical and ground stress according to claim 1 is characterized in that: The bottom area of ​​the drop weight is larger than the top area of ​​the test model.

3. The device for combined loading of underground structural components based on mechanical and ground stress according to claim 1 is characterized in that: The device also includes a secondary impact protection device; The anti-secondary impact device is used to lock the drop weight after the first impact.

4. The device for combined loading of underground structural components based on mechanical and ground stress according to claim 1 is characterized in that: The device also includes a broadband strain gauge and a transient recorder; The broadband strain gauge is connected to the pressure sensor, and the transient recorder is connected to the strain gauge.

5. The loading method based on the combined mechanical and geostress loading device for underground structural components according to any one of claims 1 to 4, characterized in that: The method is: S1: A protective layer is set above the test model, and it is determined whether there is a secondary impact protection device; S2: If available, the pressure sensor is installed on the outer side wall of the top plate of the test model, and the side wall and top of the pressure sensor are in contact with the sand; S3: If not available, install a buffer between the cover plate and the sand layer after setting up the pressure sensor; S4: Calculate the lifting height of the drop weight after setting the parameters; S5: Raise the drop hammer to the preset position according to the lifting height, connect the pressure sensor and strain gauge to the broadband strain gauge and transient recorder, perform drop hammer impact, and obtain the pressure waveform and strain waveform of the test model; S6: Compare the pressure waveform with the preset waveform to determine the relationship between the pressure waveform and the preset waveform. If they match, the pressure waveform debugging is completed and the underground structure model test is started. Otherwise, the drop weight lifting height and the cushion layer height are changed and the process returns to S5. S7: Apply confining stress to the test model and control the load size to be applied through the pressure sensor.

6. The method for combined loading of underground structural components based on mechanical and geostress according to claim 5 is characterized in that: The calculation method of the drop weight lifting height is: S1: Calculate the stress generated on the contact surface between the falling weight and the cushion: S2: One-dimensional elastic wave is transmitted from the cushion to the cover plate. Based on the stress generated on the contact surface between the drop weight and the cushion, the stress σ transmitted to the cover plate is calculated. T1 ; S3: One-dimensional elastic wave is transmitted from the cover plate to the sand layer. Based on the stress transmitted to the cover plate, the stress σ transmitted to the sand layer is calculated. T2 ; S4: The lifting height h of the drop hammer is: Among them, ρ1 is the density of the drop hammer material, c1 is the wave velocity of the drop hammer material, ρ2 is the density of the cushion material, c2 is the wave velocity of the cushion material, ρ3 is the density of the cover material, c3 is the wave velocity of the cover material, ρ4 is the density of the sand material, and c4 is the wave velocity of the sand material.

7. The method for combined loading of underground structural components based on mechanical and geostress according to claim 6 is characterized in that: If there is no cushion layer, the lifting height h of the drop weight is:

8. The falling weight lifting height calculation system is characterized by: The system comprises a storage device for executing the steps of claim 6.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by the processor, the method for calculating the height of the drop weight as claimed in claim 6 is executed.

10. A computer device, characterized in that: The device includes a memory and a processor, wherein a computer program is stored in the memory. When the processor runs the computer program stored in the memory, the processor executes the method for calculating the lifting height of the falling hammer as described in claim 6.

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