A dewatering test device for geotube bag underwater filling and overburden loading

Abstract

The present invention provides a dehydration test device for geotube bags filled underwater and overburdened, including a model test box and a geotube bag for simulation experiments, and equipped with a data acquisition module. The model test box forms a test area for placing the geotube bag; a grouting device is connected to the inside of the geotube bag, and the geotube bag is located at the bottom of the test area to simulate the bottom geotube bag; the test area simulates the water environment where the geotube bag is located under water-filled conditions. The present invention collects the height change of the geotube bag in real time during the dehydration process, and based on the height data of the geotube bag, qualitatively converts it into the drainage volume and drainage rate data of the geotube bag, and finally summarizes the dehydration and stress characteristics of the geotube bag under the water environment and overburden load conditions, which can provide an intuitive basis for engineering design, thereby obtaining a pre-scale grasp in actual engineering and ensuring the safety of underwater filling of geotube bags.

Description

Technical Field

[0001] The invention relates to the technical field of geotextile material performance testing, in particular to a dehydration test device for a geotube bag filled underwater and covered with a load. Background Art

[0002] Geotube bags are tube bag products made of high-strength textile geotextiles. The bags are filled with mud or silt to form a large tube body. They can be used as components for dam filling, river bank protection, seawall protection, rock collapse protection, flood control and rescue projects. They have the advantages of using local materials, fast construction speed, simple structure, good integrity, significant economic benefits and little impact on the environment. They are widely used.

[0003] Among them, when geotextile tube bags are used for riverside cofferdam filling, due to the characteristics of the tide, such as short intervals of rise and fall and large changes in water level, the bottom geotextile tube bags often need to be constructed underwater, and the upper geotextile tube bags are filled immediately after the filling is completed. The above-mentioned tube bag filling steps are widely used in engineering, but unlike the conventional geotextile tube bag dehydration process, the geotextile tube bags will be affected by water pressure when dehydrated in a water environment, and the drainage of mud in the tube bag becomes more difficult, resulting in low internal soil strength and increased risk of instability under the impact of tides. In addition, after the lower layer of tube bags is filled, the filling of the upper layer of tube bags will form overpressure on the lower layer of tube bags and accelerate drainage. The specific dehydration characteristics of the lower layer of tube bags in this process are still unknown. The existing filling process determines the dehydration degree of the lower layer of tube bags based on the experience of the construction personnel, which has certain risks. However, for the tube bags used as pressure-bearing, their dehydration characteristics during underwater environment construction are particularly important for the safety of the overall cofferdam construction. Summary of the invention

[0004] The purpose of the present invention is to provide a dehydration test device for simulating the dehydration process of a geotube bag in a water environment and a subsequent overlying load, which can provide an intuitive basis for engineering design.

[0005] To this end, the present invention adopts the following technical solutions:

[0006] A dehydration test device for underwater filling and overlying load of geotube bags comprises a model test box and a geotube bag for simulation experiment, and is equipped with a data acquisition module, wherein a test area for placing the geotube bag is formed inside the model test box; a grouting device is connected to the geotube bag, and the geotube bag is located at the bottom of the test area to simulate the bottom geotube bag; the test area simulates the water environment where the geotube bag is located under the water-filled condition, so as to monitor the dehydration characteristics of the geotube bag under the underwater filling condition through the data acquisition module; a servo loading system is detachably connected above the test area, and a loading plate is telescopically connected below the servo loading system, the servo loading system and the loading plate simulate the load of the geotube bag above the geotube bag, and the servo loading system applies pressure to simulate the load change of the geotube bag on the geotube bag during the internal filling process, and the dehydration characteristics of the geotube bag under the overlying load condition are monitored through the data acquisition module.

[0007] Furthermore: a first drain valve is arranged on the side wall of the model test box.

[0008] Furthermore: the servo loading system includes an electro-hydraulic servo actuator to simulate the filling process of the geotube bag above the geotube bag; connecting beams are arranged on both sides of the electro-hydraulic servo actuator, and a first fixing hole is arranged between the end of the connecting beam and the inner wall of the model test box.

[0009] Furthermore, an area is formed below the test area for the geotube bag to be filled and fully expanded.

[0010] Furthermore: the data acquisition module includes a pressure sensor and a displacement sensor which are arranged in the servo loading system and can monitor the height change of the geotube bag.

[0011] Furthermore: the model test box can also perform dehydration detection on the geotube bag in a waterless environment; the bottom of the model test box is provided with legs to form a placement area; and a second drain valve is provided at the bottom of the model test box, and a water collection detection device connected to the outlet of the second drain valve is placed in the placement area.

[0012] Furthermore: the water collection detection device includes an electronic scale and a water collection box placed on the electronic scale.

[0013] Furthermore: the model test box is detachably divided into an upper and lower part and comprises an upper model box and a lower model box, and a second fixing hole which can be connected and matched with the servo loading system is arranged in the lower model box.

[0014] Furthermore: a gasket is provided at the connection between the upper mold box and the lower mold box.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] During the test process of underwater filling of geotube bags, the present invention can collect the height changes of geotube bags in real time during dehydration through the changes of the data acquisition module and the electro-hydraulic servo loading system, and qualitatively convert the geotube bag height data into the drainage volume and drainage rate data based on the geotube bag height data. Finally, the dehydration and stress characteristics of the geotube bags under water environment and overlying load conditions are summarized, which can provide an intuitive basis for engineering design, thereby obtaining a preliminary scale grasp in actual engineering and ensuring the safety of underwater filling of geotube bags. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall structure of the overlying load working condition system of the present invention;

[0018] Figure 2 It is a schematic diagram of the overall structure of the self-weight dehydration working condition system of the present invention;

[0019] Figure 3 It is a schematic diagram of the explosion structure of the combined model test box of the present invention;

[0020] Figure 4 It is a schematic diagram of the change of pore water pressure in the water environment of the present invention;

[0021] Figure 5 Schematic diagram of the change in height of the geotube bag in a water environment of the present invention.

[0022] The markings in the accompanying drawings are: 1-upper model box, 11-screws, 12-nuts, 2-lifting hooks, 3-gaskets, 4-lower model box, 41-wire ports, 5-electro-hydraulic servo loading system, 6-loading plates, 71-connecting beams, 72-fixing holes, 8-first drainage valves, 9-second drainage valves, 10-geotube bags, 11-pore water pressure gauges, 12-strain gauges, 13-water collecting tanks, 14-electronic scales, 15-model test boxes. DETAILED DESCRIPTION

[0023] The present invention is further described below in conjunction with the accompanying drawings and embodiments, but they are not intended to limit the present invention.

[0024] like Figure 1-Figure 5 As shown, this embodiment provides a dehydration test device for a geotube bag simulating underwater filling and overlying load conditions, and the dehydration test device can determine the drainage volume and drainage rate of the geotube bag under corresponding conditions.

[0025] The dehydration test device includes a model test box 15, and a geotube bag 10 for conducting a simulation experiment, and is equipped with a data acquisition module. A test area 16 for placing the geotube bag 10 is formed inside the model test box 15; a grouting device is connected to the inside of the geotube bag 10, and the geotube bag 10 is located at the bottom of the test area 16 to simulate the bottom geotube bag; the test area 16 simulates the water environment where the geotube bag 10 is located under the water-filled condition, so that the dehydration characteristics of the geotube bag 10 under the underwater filling condition are monitored through the data acquisition module; a servo loading system 5 is detachably connected above the test area 16, and a loading plate 6 is telescopically connected below the servo loading system 5. The servo loading system 5 and the loading plate 6 simulate the load of the geotube bag above the geotube bag 10, and the servo loading system 5 applies pressure to simulate the load change of the geotube bag 10 on the geotube bag 10 during the internal filling process, and the dehydration characteristics of the geotube bag 10 under the overlying load condition are monitored through the data acquisition module.

[0026] In this embodiment, the monitoring of the dehydration characteristics includes monitoring the drainage volume and drainage rate of the geotube 10 , wherein the drainage volume is indirectly reflected by the height of the geotube 10 , and the drainage rate of the geotube 10 can be indirectly obtained.

[0027] Specifically, the servo loading system 5 includes an electro-hydraulic servo actuator to simulate the filling process of the geotube bag above the geotube bag 10, rather than applying a large load instantly; connecting beams 71 are provided on both sides of the electro-hydraulic servo actuator, and a first fixing hole 72 is provided between the end of the connecting beam 71 and the inner wall of the model test box 15. In this embodiment, the first fixing hole 72 and the second fixing hole 73 are both threaded holes, and a disk is provided at the end of the connecting beam 71 and a through hole matching the threaded hole is provided thereon, so that the servo loading system 5 is connected and fixed to the model test box 15 by bolts.

[0028] Among them, the data acquisition module includes a pull rope displacement sensor for monitoring the height change of the geotube bag 10 in the absence of overlying load and water; the data acquisition module also includes a pressure sensor and a displacement sensor equipped in the servo loading system 5 that can monitor the height change of the geotube bag 10 under the condition of overlying load.

[0029] The pull rope displacement sensor is fixed at one end to the bottom of the loading plate 6, and one end of the pull rope is connected and fixed to the upper surface of the geotube 10. At this time, the loading plate 6 remains in its original position, so that the pull rope condition after the geotube 10 is dehydrated and its surface height drops can be obtained to obtain the corresponding height change of the geotube 10 when it is dehydrated without an overlying load. The pressure sensor is set in the loading plate 6. When the loading plate 6 is subjected to an external force, the pressure sensor in the loading plate 6 will be squeezed to obtain pressure data, and the displacement sensor is set at the telescopic link part of the electro-hydraulic servo actuator to adjust the telescopic movement. When the telescopic link is extended or shortened each time, the length of the telescopic link will be confirmed and output, so as to obtain real-time length change data of the telescopic link. When the surface of the geotube 10 contacts the loading plate 6, the two will form a synchronous displacement change, so the change in the height of the geotube 10 after the overlying load is applied can be monitored in real time through the displacement change of the telescopic link.

[0030] The process of monitoring the height of the geotube bag 10 by the telescopic connecting rod is as follows: the pressure of the pressure sensor remains basically stable when entering the water environment, and the pressure value obtained at the moment of contact with the geotube bag 10 increases sharply, thereby forming an initial value of displacement through the displacement sensor. Thereafter, the loading plate 6 will provide an overlying pressure of a stable set value to the geotube bag 10. During this process, the height of the geotube bag 10 will continue to change until the end of the experiment, and the final value of the displacement will be recorded, thereby indirectly obtaining the height change of the geotube bag 10.

[0031] The area below the test area 16 is used to fill the geotube bag 10 and allow it to fully expand.

[0032] Wherein, a first drain valve 8 is arranged on the side wall of the model test box 15 .

[0033] like Figure 1-5 As shown, this embodiment also provides a monitoring structure for multi-faceted detection of geotube bags. The monitoring structure monitors the corresponding pore water pressure, the tension of the geotube bag 10 and the drainage volume through a data acquisition module.

[0034] Specifically, the data acquisition module includes a pore water pressure gauge 11 and a strain gauge 12; the pore water pressure gauge 11 is arranged inside the geotube bag 10, the strain gauge 12 is arranged on the surface of the geotube bag 10, and a wire opening 41 is provided on the side wall of the model test box 15 for only the wires of the pore water pressure gauge 11 and the strain gauge 12 to pass through. The wire opening 41 is then blocked after the wire passes through to prevent the water in the model test box 15 from flowing out, and at the same time, it can also avoid the need to thread the wire from the top of the model test box 15 in a water environment, which may cause the wire of the sensor to be squeezed easily when pressurized, thereby affecting the accuracy of the data.

[0035] Among them, since it is necessary to obtain the changes in pore water pressure at different heights in the geotube bag 10, a three-layer iron frame is customized, and pore water pressure gauges 11 are arranged on different layers, which can be connected by binding. The strain gauge 12 is located on the longitudinal axis and the transverse axis of the surface of the geotube bag 10, and is arranged by gluing with flexible glue.

[0036] like Figure 5 As shown, since the pore water pressure gauge 11 is fixed at different heights, the hydrostatic pressure of the pore water pressure gauge 11 at different positions is also different. Taking the middle bottom layer as an example, the water pressure of the pore water pressure gauge 11 at a depth of 1 meter reaches a maximum of 9.5 kPa. The filling starts at about 500 seconds and finally reaches about 12 kPa. After the filling is completed, the soil in the geotube bag 10 begins to drain, so the pore water pressure begins to dissipate. After about 1000 seconds, the pore pressure dissipates to 10.2 kPa. Similarly, Figure 4 As shown in the figure, the height of the geotube bag 10 reaches 200mm after filling, and then shows a downward trend that is first fast and then slow. After about 2000s, it stabilizes at 100mm. From the above analysis, it is not difficult to see that the change in the height of the geotube bag 10 during the filling process is basically consistent with the change in the pore pressure. In the drainage process, the drop time of the geotube bag 10 is slightly longer than the drop time of the pore pressure. This is because the change in the height of the geotube bag 10 is not only caused by the drainage of the soil. When the soil has basically ended the drainage stage, it can still move laterally (all around), thereby further reducing the height of the geotube bag 10.

[0037] Among them, regarding the expansion of the geotube 10, the height change caused by the expansion of the geotube 10 (tensioning causes the material strain of the geotube 10 to reach only within 5%) is negligible compared to the height change of the geotube 10 caused by drainage (10 cm for indoor tests).

[0038] like Figure 2As shown, the present embodiment also provides a dehydration test device for detecting dehydration of geotube bags in a waterless environment. Compared with the traditional integrated test box, the dehydration test device, on the one hand, in order to realize the dehydration test of the geotube bag 10 in a water environment, needs to design the height of the model test box 15 to be at least 1.5m (simulating the water pressure of more than 10kPa in actual engineering), on the other hand, when performing dehydration in a waterless environment, the excessively high height of the model test box 15 will bring inconvenience to the preparation of the test and the installation of the sensor (for example: 1. The mud pump with a voltage of 220V is usually only The mud can be delivered to a height of 0.6m-0.8m. 2. After the geotube 10 is placed in the model test box 15, the wires of the pore water pressure gauge 11 and the strain gauge 12 can pass through the wire port 41. If the geotube 10 to be tested is in a waterless state or in a water state with a low water level in the model test box 15, only the lower model box 4 can be used for the experiment, and the operator can bend down to perform the corresponding operation; while the integrated model test box 15 requires the use of tools such as ladders to climb over and enter the model test box 15 to perform the same operation, which is time-consuming and laborious).

[0039] The dehydration test device includes a support leg arranged at the bottom of the model test box 15 to form a placement area; a second drain valve 9 is arranged at the bottom of the model test box 15, and a water collection detection device connected to the outlet of the second drain valve 9 is placed in the placement area.

[0040] Specifically, the model test box 15 is detachably divided into an upper model box 1 and a lower model box 4 , and a second fixing hole 73 which can be connected and matched with the connecting beam 71 of the servo loading system 5 is arranged in the lower model box 4 .

[0041] Among them, the upper model box 1 is an iron cuboid with openings on both the upper and lower parts, and the lower model box 4 is an iron cuboid with an opening on the upper part. The upper model box 1 has an upper connecting plate extending outwards by 2 cm at the bottom, and the lower model box 4 has a lower connecting plate extending outwards by 2 cm at its opening, and screw holes are arranged at intervals on the upper connecting plate and the lower connecting plate, and the screw holes in the upper connecting plate and the lower connecting plate are interconnected, and the upper model box 1 is connected to the lower model box 4 by combining screws 11 and nuts 12 that can be matched with the screw holes. A lifting hook 2 is arranged on the top of the upper model box 1 to separate and transport the upper model box 1 and the lower model box 4.

[0042] In this way, the above-mentioned problem can be solved by conveniently disassembling and assembling the upper model box 1, the lower model box 4 and the servo loading system 5. When performing a waterless environment test, only the lower model box 4 is used, and the servo loading system 5 and the connecting beam 71 are installed on the second fixing hole 73, and an overburden load of any size can be applied to the geotube bag 10.

[0043] Among them, a gasket 3 is arranged between the upper connecting plate and the lower connecting plate. The gasket 3 can be made of rubber material.

[0044] Specifically, the water collection detection device includes an electronic scale 14 and a water collection box 13 placed on the electronic scale 14, so as to detect the dehydration amount in the absence of water.

[0045] This embodiment provides a formula for the overburden load range that can be achieved by the dehydration test device, and the specific formula is as follows:

[0046] P max =F / A

[0047] Wherein, F is the maximum load of the loading system, and A is the loading contact area, that is, the area of ​​the loading plate 6.

[0048] In this embodiment, the maximum load of the servo loading system is 30 kN, and the size of the loading plate 6 is 0.6 m × 0.8 m (length × width), then the maximum pressure P max Achievable:

[0049] P max =F / A=30000 / 0.6 / 0.8=62.5kPa

[0050] From the above formula, it can be seen that the maximum simulated overburden pressure is 62.5 kPa. Since the soil in the geotube 10 has a high water content, the specific gravity γ is about 1300 kg / m3. Therefore, the servo loading system 5 can simulate a maximum overpressure of 4.8 m above the geotube.

[0051] See also Figure 1-5 When conducting the dehydration characteristic experiment of the geotube bag 10, the specific operation method is as follows:

[0052] S1: Comprehensively consider the size of the geotube bag 10 model, the upper model box 1, and the lower model box 4, so as to determine the size of the gasket 3 and the maximum overpressure level that can be simulated;

[0053] S2: Place the geotube bag 10 in the lower model box 4 and connect the relevant pore water pressure gauge 11 and strain gauge 12, open the first drainage valve 8 and pass the sensor wire in the geotube bag 10 through the wire port 41 to electrically connect the wire to the computer.

[0054] S3: If a conventional geotube 10 dehydration test is conducted without overburden in a water-free environment, the electro-hydraulic servo loading system is hoisted in the lower model box and installed and connected, and then the geotube 10 is filled with mud through a mud pump, and then the geotube 10 starts to drain, and the filtered liquid is collected in a placed water collection tank 13 through the opened second drainage valve 9 and weighed in real time by an electronic scale 14;

[0055] When the drainage of the geotube bag 10 reaches the designed time, the position of the loading plate 6 of the electro-hydraulic servo loading system is adjusted, and the overlying load can be applied after the load size is set.

[0056] S4: If the dehydration test of the geotube bag 10 is conducted considering the water environment and the overlying load, the lower model box 4 and the upper model box 1 are assembled and connected by a crane, and then the electro-hydraulic servo loading system 5 is hoisted and installed in the upper model box 1;

[0057] Close the first drain valve 8 and the second drain valve 9, and fill the model test box 15 with water through the water pipe to a suitable height;

[0058] Monitoring of drainage rate without overburden load: Use a mud pump to fill mud into the geotube 10, so that the geotube 10 can drain water. The height change of the geotube 10 can be observed by the pull rope displacement sensor, and the drainage rate of the geotube 10 can be indirectly observed.

[0059] Monitoring of drainage rate under overlying load: When the drainage of the geotube 10 reaches the designed time, adjust the position of the loading plate 6 of the electro-hydraulic servo loading system 5. After setting the load size, the overlying load can be applied to accelerate the drainage of the geotube 10. The height change of the geotube 10 can be obtained by observing the displacement change of the loading plate 6 in the electro-hydraulic servo loading system 5 based on the displacement sensor. The drainage rate of the geotube 10 can be indirectly observed by calculating the drainage volume / time of the drainage data.

[0060] The above embodiment is only a preferred technical solution of the present invention. Those skilled in the art should understand that the technical solutions or parameters in the embodiments can be modified or replaced without departing from the principle and essence of the present invention, and all should be covered within the protection scope of the present invention.

Claims

1. A dewatering test device for geotube bag underwater filling and overlying load, characterized by: It comprises a model test box (15) and a geotextile tube bag (10) for conducting a simulation experiment, and is equipped with a data acquisition module, wherein a test area (16) for placing the geotextile tube bag (10) is formed inside the model test box (15); The geotube bag (10) is connected to a grouting device, and the geotube bag (10) is located at the bottom of the test area (16) to simulate the bottom geotube bag; The test area (16) simulates the water environment of the geotube (10) under water-filled conditions, thereby monitoring the dehydration characteristics of the geotube (10) under underwater filling conditions through the data acquisition module; A servo loading system (5) is detachably connected above the test area (16), and a loading plate (6) is telescopically connected below the servo loading system (5). The servo loading system (5) includes an electro-hydraulic servo actuator. The servo loading system (5) and the loading plate (6) simulate the load of the geotube bag above the geotube bag (10), and the servo loading system (5) applies pressure to simulate the load change of the geotube bag (10) during the filling process of the geotube bag above the geotube bag (10). The dehydration characteristics of the geotube bag (10) under the overlying load condition are monitored through the data acquisition module. The data acquisition module includes a pressure sensor and a displacement sensor equipped in the servo loading system (5) that can monitor the height change of the geotube bag (10).

2. A dehydration test device for geotube bag underwater filling and overlying load according to claim 1, characterized in that: A first drainage valve (8) is provided on the side wall of the model test box (15).

3. The dehydration test device for geotube bag underwater filling and overlying load according to claim 1, characterized in that: Connecting beams (71) are arranged on both sides of the electro-hydraulic servo actuator, and first fixing holes (72) are arranged between the ends of the connecting beams (71) and the inner wall of the model test box (15).

4. The dehydration test device for geotube bag underwater filling and overlying load according to claim 1, characterized in that: An area is formed below the test area (16) for the geotube bag (10) to be filled and fully expanded.

5. The dehydration test device for geotube bag underwater filling and overlying load according to claim 1, characterized in that: The model test box (15) can also perform dehydration testing on the geotube bag (10) in a waterless environment; the bottom of the model test box (15) is provided with supporting feet to form a placement area; A second drainage valve (9) is arranged at the bottom of the model test box (15), and a water collection detection device connected to the outlet of the second drainage valve (9) is placed in the placement area.

6. A dewatering test device for geotube bag underwater filling and overlying load according to claim 5, characterized in that: The water collection detection device comprises an electronic scale (14) and a water collection box (13) placed on the electronic scale (14).

7. A dehydration test device for geotube bag underwater filling and overlying load according to claim 5, characterized in that: The model test box (15) is detachably divided into an upper and lower part and comprises an upper model box (1) and a lower model box (4). The lower model box (4) is provided with a second fixing hole (73) which can be connected and matched with the servo loading system (5).

8. A dewatering test device for geotube bag underwater filling and overlying load according to claim 7, characterized in that: A gasket (3) is provided at the connection between the upper mold box (1) and the lower mold box (4).

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