Test device and test method for simulating hydraulic fracture of crack of gravity dam under impact load

Abstract

The invention discloses a test device and a test method for simulating hydraulic fracture of a crack of a gravity dam under an impact load. The test device comprises a test main body, a sealing device, a water pressure applying device, a load applying device, crack monitoring equipment and high-speed photographic equipment. The test device and the test method have the following technical advantages: 1, the test device can simulate a concrete gravity dam with water pressure-gravity balance, is more consistent with actual engineering, and overcomes the defect that a crack hydraulic fracture test is performed by only providing mechanical force; 2, the test precision is high, the step-by-step increment impact load is adopted until the crack is expanded, crack expansion is monitored, and the hydraulic fracture characteristics of the crack are recorded, so that the hydraulic fracture expansion process of the concrete gravity dam crack under the action of the impact load is obtained; and 3, the experimental device is simple to operate, accessories are simple and easy to replace, and the experimental device has popularization value in the technical field of hydraulic fracture tests of the concrete gravity dam cracks.

Description

Technical Field

[0001] The invention relates to the technical field of test devices for water conservancy projects, and in particular to a test device and a test method for simulating hydraulic fracturing of cracks in a gravity dam under impact load. Background Art

[0002] Gravity dams are a common type of dam in water conservancy projects, and their safety is crucial to preventing flood disasters. Under the action of earthquakes, explosions or other impact loads, gravity dams may experience hydraulic splitting of cracks, resulting in damage to the dam body. In severe cases, the dam may even be damaged and cause a dam breach, posing a serious threat to major engineering construction operations and downstream lifeline cities. However, the test models used in existing crack hydraulic splitting research methods simplify the test conditions, making the test results conservative and quite different from the actual crack hydraulic splitting. In view of this, the existing problems are studied and improved. The present invention aims to provide a test device and test method for simulating the hydraulic splitting of cracks in a gravity dam under impact loads, so as to accurately simulate the actual working conditions, and the operation is simple, and the test cost is effectively reduced, which is of great significance for studying the crack extension mechanism of gravity dams under impact loads. Summary of the invention

[0003] In order to overcome the technical problems described in the prior art, the purpose of the present invention is to provide a test device and a test method for simulating hydraulic fracturing of cracks in a gravity dam under impact load.

[0004] In a first aspect, the present invention provides a test device for simulating hydraulic fracturing of cracks in a gravity dam under an impact load, comprising:

[0005] The test body comprises a base, a gravity dam model is fixedly connected to the top of the base, and the gravity dam model is provided with prefabricated cracks running through the length direction of the dam body;

[0006] A sealing device, used for sealing two opposite opening ends of the prefabricated crack;

[0007] A water pressure applying device, which is used to make the prefabricated cracks filled with water pressure and open;

[0008] a load applying device comprising a gravity hammer capable of striking the gravity dam model; and,

[0009] Fracture monitoring equipment for monitoring fracture propagation, and high-speed photography equipment for recording hydraulic fracturing characteristics of fractures.

[0010] As a preferred technical solution, the gravity dam model is connected to the top of the base by bolts.

[0011] As a preferred technical solution, the sealing device includes two groups of tempered glass, and the two groups of tempered glass are connected by tension bolts to clamp the two sides of the gravity dam model.

[0012] As a preferred technical solution, the water pressure applying device includes two groups of water guiding bends, which are respectively arranged above and below the prefabricated cracks and are connected to the prefabricated cracks to apply water pressure to the prefabricated cracks.

[0013] As a preferred technical solution, the load applying device also includes a hoisting mechanism for hoisting the gravity hammer, and the hoisting mechanism can adjust the vertical height of the gravity hammer, wherein the gravity hammer is provided with a hollow cavity for placing a counterweight, and the gravity hammer is provided with an arc-shaped hammer head on the side close to the gravity dam model.

[0014] As a preferred technical solution, the crack monitoring device includes a plurality of strain gauges attached to the side walls of the gravity dam model and a measurement and acquisition instrument connected to the strain gauge signals to test the vertical crack direction strain of the gravity dam model.

[0015] As a preferred technical solution, the test device includes two groups of high-speed photography equipment respectively facing the two opposite opening ends of the prefabricated cracks to record the hydraulic splitting characteristics of the cracks.

[0016] In a second aspect, based on the above test device for simulating hydraulic fracturing of cracks in a gravity dam under impact load, the present invention further provides a test method, comprising the following steps:

[0017] Step 1: Forming and casting to obtain a gravity dam model with prefabricated cracks, and assembling a test device;

[0018] Step 2: Start the water pressure applying device to simulate the water pressure effect under actual working conditions;

[0019] Step 3: Start the load application device and use the gravity hammer to generate impact load on the gravity dam model;

[0020] Step 4: The crack monitoring device monitors the expansion process of the prefabricated cracks, and the high-speed photography device records the hydraulic splitting characteristics of the prefabricated cracks;

[0021] Step 5: Adjust the impact load provided by the load application device to conduct several tests, so as to facilitate the analysis of the hydraulic fracturing mechanism of the gravity dam cracks.

[0022] As a preferred technical solution, in step 3, the vertical height of the gravity hammer is adjusted by the hoisting mechanism to adjust the monitoring area of ​​the crack monitoring device.

[0023] As a preferred technical solution, in step 5, the adjustment of the load applying device is specifically as follows: counterweights are placed step by step in the hollow cavity of the gravity hammer until the prefabricated crack expands.

[0024] In summary, the present invention has the following technical effects:

[0025] The test device and test method for simulating hydraulic splitting of cracks in a gravity dam under impact load of the present invention include a test body, a sealing device, a water pressure applying device, a load applying device, a crack monitoring device and a high-speed photography device. The test device and test method of the present invention have the following technical advantages: 1. The test device of the present invention can simulate a concrete gravity dam with water pressure-gravity balance, which is more consistent with the actual project and overcomes the defect of hydraulic splitting test of cracks by providing mechanical force alone; 2. The test accuracy of the present invention is high. It uses a step-by-step incremental impact load until the crack expands, monitors the crack expansion and records the hydraulic splitting characteristics of the crack to obtain the hydraulic splitting expansion process of the concrete gravity dam crack under the impact load; 3. The experimental device of the present invention is simple to operate, and its accessories are simple and easy to replace, which has promotion value in the field of hydraulic splitting test technology of concrete gravity dam cracks. Therefore, compared with the existing crack hydraulic splitting research method, the test device and test method for simulating hydraulic splitting of cracks in a gravity dam under impact load provided by the present invention have obvious technical advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 It is a schematic front view of a test device for simulating hydraulic fracturing of cracks in a gravity dam under an impact load according to an embodiment of the present invention;

[0028] Figure 2 is a side view schematic diagram of a test device for simulating hydraulic fracturing of cracks in a gravity dam under impact load according to an embodiment of the present invention;

[0029] The meanings of the reference numerals are as follows:

[0030] 1- base;

[0031] 2- Gravity dam model, 21- Prefabricated cracks;

[0032] 3-tempered glass, 31-tension bolts;

[0033] 4-water bend;

[0034] 5- gravity hammer, 51- arc-shaped hammer head;

[0035] 6- High-speed photography equipment. DETAILED DESCRIPTION

[0036] The following will be combined with the accompanying drawings in this embodiment to clearly and completely describe the technical solution in this embodiment. The present embodiment described herein is only for illustrative purposes and is not intended to limit the scope of protection of the present invention. Therefore, it should be understood that various modifications and changes can be made to this embodiment without departing from the scope of protection of the present invention.

[0037] In the description of the present invention, unless otherwise clearly specified and limited, the term "and / or" includes any and all combinations of one or more associated listed items. Unless otherwise specified or explained, the terms "connection", "fixed", etc. should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, an integral connection, an electrical connection, or a signal connection; "connection" can be a direct connection or an indirect connection through an intermediate medium. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] Further, in the description of the present invention, it should be understood that the directional words described in the present embodiment are described at the angles shown in the accompanying drawings and should not be understood as limiting the present embodiment. It should also be understood that in the context, when it is mentioned that an element or feature is connected to another element (one or more), it can not only be directly connected to the other (one or more) elements, but also indirectly connected to the other (one or more) elements through an intermediate element.

[0039] Before introducing the technical solution of the present invention, it is necessary to explain the background of the invention: gravity dam is a common dam type in water conservancy projects, and its safety is crucial to preventing flood disasters. Under the action of earthquakes, explosions or other impact loads, gravity dams may experience crack hydraulic splitting, resulting in damage to the dam body, and even damage to the dam in severe cases, causing dam failure accidents, posing a serious threat to major engineering construction and operation and downstream lifeline cities. However, the test models used in the existing crack hydraulic splitting research methods simplify the test conditions, making the test results conservative and quite different from the actual crack hydraulic splitting.

[0040] First, see Figure 1 and Figure 2 An exemplary embodiment of the present invention first provides a test device for simulating hydraulic fracturing of cracks in a gravity dam under impact loads, the test device comprising a test body, a sealing device, a water pressure applying device, a load applying device, a crack monitoring device and a high-speed photography device 6.

[0041] The components of the above experimental device are described below:

[0042] Test subject:

[0043] In some embodiments, see Figure 1 and Figure 2 The test body includes a base 1, a gravity dam model 2 is fixedly connected to the top of the base 1, and the gravity dam model 2 is provided with a prefabricated crack 21 that runs through the length direction of the dam body. It should be understood that the prefabricated crack 21 runs through the length direction of the dam body to facilitate the experimenter to observe the expansion of the crack from the two opposite open ends of the prefabricated crack 21. A sealing device will be used to seal the two opposite open ends of the prefabricated crack 21 to simulate the existence of cracks in actual working conditions. And the gravity dam model 2 of the present invention is made of concrete pouring. Preferably, the gravity dam model 2 and the base 1 are connected by bolts to obtain the test body. While achieving a tight connection between the two, it is also convenient for the subsequent disassembly and replacement of the deformed and damaged gravity dam model 2; wherein the base 1 is preferably a gravity steel base 1. It should be noted that under the action of earthquakes, explosions or other impact loads, the dam heel is a weak area of ​​the dam body, and the problem of hydraulic splitting of cracks at this position is more prominent, such as Figure 1 As shown, the location of the prefabricated cracks 21 is preferably the heel portion of the gravity dam model 2 .

[0044] Sealing device:

[0045] In some embodiments, see Figure 1 and Figure 2 The sealing device is used to seal the two opposite opening ends of the prefabricated crack 21. Specifically, the sealing device includes two sets of tempered glass 3, which are connected by tension bolts 31 to clamp the two sides of the gravity dam model 2. While sealing the two sides of the gravity dam, it will not interfere with the observation of the two opposite opening ends of the prefabricated crack 21, ensuring that the test personnel can effectively observe the dynamic expansion process of the crack. Preferably, the gap between the tempered glass 3 and the two sides of the gravity dam is filled with water-stopping rubber to further enhance the sealing of the two sides of the gravity dam.

[0046] Water pressure applying device:

[0047] In some embodiments, see Figure 1 and Figure 2 The water pressure applying device is used to make the prefabricated crack 21 filled with water pressure and opened. Specifically, the water pressure applying device includes two groups of water bends 4, which are respectively arranged above and below the prefabricated crack 21 and connected to the prefabricated crack 21, and one end of the two groups of water bends 4 is connected to a water supply system (not shown in the figure) so as to be able to inject water into the prefabricated crack 21, that is, to apply water pressure to the prefabricated crack 21, so as to simulate the concrete gravity dam with water pressure-gravity balance in actual working conditions.

[0048] Load application device:

[0049] In some embodiments, see Figure 1 and Figure 2 The load applying device includes a gravity hammer 5 that can hit the gravity dam model 2, that is, the hammering effect of the gravity hammer 5 is used as the impact load, wherein the load applying device also includes a hoisting mechanism for hoisting the gravity hammer 5, and the hoisting mechanism can adjust the vertical height of the gravity hammer 5. It should be understood that this type of test is usually carried out in a transparent test box, so the top of the hoisting mechanism can be fixed at the top of the test box. As a preferred technical solution, the gravity hammer 5 is provided with a hollow cavity to place a counterweight. With such a design, the counterweight can be added or reduced step by step into the hollow cavity to achieve step-by-step adjustment of the impact load size of the gravity hammer 5 and increase the test accuracy; the gravity hammer 5 is provided with an arc-shaped hammer head 51 on one side close to the gravity dam model 2. With such a design, the impact load provided by the gravity hammer 5 can be concentrated on the convex point of the arc-shaped hammer head 51, so as to avoid the load acting on the crack being too different from the preset value due to the excessive dispersion of the impact load action point, which causes errors in the hydraulic fracturing analysis of the crack.

[0050] The test device for simulating hydraulic fracturing of cracks in a gravity dam under impact load of the present invention also includes a crack monitoring device for monitoring crack expansion and a high-speed photography device 6 for recording crack hydraulic fracturing characteristics. As a preferred technical solution, the crack monitoring device includes a plurality of strain gauges attached to the side walls of the gravity dam model 2 and a measurement and acquisition instrument connected to the strain gauge signals to test the vertical crack direction strain of the gravity dam model 2. To improve the accuracy and reliability of the test, please refer to Figure 1 and Figure 2 The test device includes two sets of high-speed photographic equipment 6 facing the two opposite opening ends of the prefabricated crack 21, respectively, to record the hydraulic splitting characteristics of the crack from both sides, effectively reducing the test error. The high-speed photographic equipment 6 includes a high-speed camera and a computer imager electrically connected to the high-speed camera, so as to visually observe the image of the hydraulic splitting characteristics of the crack taken by the high-speed camera.

[0051] In a second aspect, based on the above test device for simulating hydraulic fracturing of cracks in a gravity dam under impact load, the present invention further provides a test method, comprising the following steps:

[0052] Step 1: Formwork casting is performed to obtain a gravity dam model 2 with prefabricated cracks 21, and a test device is assembled;

[0053] Among them, during the assembly process of the sealing device, attention should be paid to the sealing of high-pressure water. Water-stop rubber can be filled in the gap between the tempered glass 3 and the two sides of the gravity dam to further strengthen the sealing of the two sides of the gravity dam.

[0054] Step 2: Start the water pressure applying device to simulate the water pressure effect under actual working conditions;

[0055] Step 3, start the load applying device and use the gravity hammer 5 to generate an impact load on the gravity dam model 2; wherein, as a preferred technical solution, in step 3, the vertical height of the gravity hammer 5 is adjusted by the hoisting mechanism to adjust the monitoring area of ​​the crack monitoring device.

[0056] Step 4: The crack monitoring device monitors the expansion process of the prefabricated crack 21, and the high-speed photography device 6 records the hydraulic splitting characteristics of the prefabricated crack 21;

[0057] Step 5: Adjust the impact load provided by the load application device to conduct several tests, so as to facilitate the analysis of the hydraulic fracturing mechanism of the gravity dam cracks.

[0058] Among them, as a preferred technical solution, in step 5, the adjustment of the load applying device is specifically: counterweights are placed step by step in the hollow cavity of the gravity hammer 5 until the prefabricated crack 21 expands.

[0059] The present invention realizes the real simulation of hydraulic splitting of cracks in the weak area of ​​the gravity dam heel, and overcomes the defects of the test model used in the traditional splitting test, which simplifies the test conditions, makes the test results conservative, has a large difference from the actual hydraulic splitting of cracks, and has a simple simulated stress state.

[0060] In summary, the construction method using this internal propping device has the following technical advantages:

[0061] 1. The test device of the present invention can simulate a concrete gravity dam with water pressure-gravity balance, which is more consistent with actual engineering and overcomes the defect of conducting hydraulic splitting test of cracks only by providing mechanical force; 2. The test of the present invention has high accuracy. It adopts step-by-step incremental impact load until the cracks expand, monitors the crack expansion and records the hydraulic splitting characteristics of the cracks to obtain the hydraulic splitting expansion process of the concrete gravity dam cracks under the impact load; 3. The experimental device of the present invention is simple to operate, and its accessories are simple and easy to replace, which has promotion value in the field of hydraulic splitting test technology of concrete gravity dam cracks.

[0062] 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 make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A test device for simulating hydraulic fracturing of cracks in a gravity dam under impact load, characterized in that: include: The test body comprises a base, a gravity dam model is fixedly connected to the top of the base, and the gravity dam model is provided with prefabricated cracks running through the length direction of the dam body; A sealing device, used for sealing two opposite opening ends of the prefabricated crack; A water pressure applying device, which is used to make the prefabricated cracks filled with water pressure and open; a load applying device comprising a gravity hammer capable of striking the gravity dam model; as well as, Fracture monitoring equipment for monitoring fracture propagation, and high-speed photography equipment for recording hydraulic fracturing characteristics of fractures.

2. The test device for simulating hydraulic fracturing of cracks in a gravity dam under impact load according to claim 1, characterized in that: The gravity dam model is connected to the top of the base by bolts.

3. The test device for simulating hydraulic fracturing of cracks in a gravity dam under impact load according to claim 2, characterized in that: The sealing device comprises two groups of tempered glass, and the two groups of tempered glass are connected by tension bolts to clamp the two sides of the gravity dam model.

4. The test device for simulating hydraulic fracturing of cracks in a gravity dam under impact load according to claim 3, characterized in that: The water pressure applying device comprises two groups of water guiding bends, which are respectively arranged above and below the prefabricated cracks and are connected to the prefabricated cracks to apply water pressure to the prefabricated cracks.

5. The test device for simulating hydraulic fracturing of cracks in a gravity dam under impact load according to claim 4, characterized in that: The load applying device also includes a hoisting mechanism for hoisting the gravity hammer, and the hoisting mechanism can adjust the vertical height of the gravity hammer, wherein the gravity hammer is provided with a hollow cavity for placing a counterweight, and a curved hammer head is provided on a side of the gravity hammer close to the gravity dam model.

6. The test device for simulating hydraulic fracturing of cracks in a gravity dam under impact load according to claim 5, characterized in that: The crack monitoring device includes a plurality of strain gauges attached to the side walls of the gravity dam model and a measurement and acquisition instrument connected to the strain gauge signals to test the vertical crack direction strain of the gravity dam model.

7. The test device for simulating hydraulic fracturing of cracks in a gravity dam under impact load according to claim 6, characterized in that: The test device includes two groups of high-speed photography equipment respectively facing two opposite opening ends of the prefabricated cracks to record the hydraulic splitting characteristics of the cracks.

8. A test method based on the test device according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1: Forming and casting to obtain a gravity dam model with prefabricated cracks, and assembling a test device; Step 2: Start the water pressure applying device to simulate the water pressure effect under actual working conditions; Step 3: Start the load application device and use the gravity hammer to generate impact load on the gravity dam model; Step 4: The crack monitoring device monitors the expansion process of the prefabricated cracks, and the high-speed photography device records the hydraulic splitting characteristics of the prefabricated cracks; Step 5: Adjust the impact load provided by the load application device to conduct several tests, so as to facilitate the analysis of the hydraulic fracturing mechanism of the gravity dam cracks.

9. The test method according to claim 8, characterized in that In step 3, the vertical height of the gravity hammer is adjusted by the hoisting mechanism to adjust the monitoring area of ​​the crack monitoring device.

10. The test method according to claim 9, characterized in that: In step 5, the load applying device is adjusted specifically by placing counterweights step by step in the hollow cavity of the gravity hammer until the prefabricated crack expands.

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