A device for measuring the ultimate frictional strength of the soil nail-soil interface.

Abstract

This utility model discloses a measuring device for the ultimate frictional strength of the soil nail-soil interface, including an experimental chamber, a first support frame, a second support frame, and a computer. The experimental chamber contains a sensor assembly and a pre-embedded steel pipe arranged obliquely and removable. The upper end of the pre-embedded steel pipe is located outside the experimental chamber, and the interior of the pre-embedded steel pipe is used to insert reinforcing bars. The first support frame has a vertical force application mechanism and a water spraying mechanism above the experimental chamber. The vertical force application mechanism is used to compact the soil placed inside the experimental chamber, and the water spraying mechanism is used to spray water into the experimental chamber. The second support frame has a pull-out mechanism and a horizontal force application mechanism. The pull-out mechanism is used to pull the pre-embedded steel pipe out of the experimental chamber, and the horizontal force application mechanism is used to apply tension to the reinforcing bars. The computer is used to analyze the measurement data from the measuring device. Using the above device for experimental simulation can effectively solve the problem that existing technologies cannot realistically simulate actual engineering environments.

Description

Technical Field

[0001] This utility model relates to the technical field of soil nail-soil interface ultimate friction strength testing, and particularly to a measuring device for soil nail-soil interface ultimate friction strength. Background Technology

[0002] Soil nailing technology is convenient, fast, and inexpensive to construct, and has been widely used in various foundation pit and slope reinforcement projects, yielding significant social and economic benefits. In some coastal areas with frequent rainfall, soil-nailed slopes will experience hundreds of wet-dry cycles over their 50-100 year service life. Under the influence of these cycles, the soil interior and the soil nail-soil interface will weaken, leading to a year-on-year increase in the probability of slope instability. Therefore, studying the impact of the number of wet-dry cycles on slope stability is of great significance.

[0003] Existing research mainly focuses on the strength weakening characteristics of soil under wet-dry cycles, while the weakening characteristics of soil nail-soil interface friction strength are rarely addressed. The weakening mechanism of the ultimate friction strength of the soil nail-soil interface with the number of wet-dry cycles is unclear, and there is an urgent need to establish a relevant water weakening model.

[0004] Furthermore, existing indoor tests mainly focus on direct shear tests, which are insufficient to characterize the actual field conditions of the soil nail-soil interface on soil-nailed slopes. In actual engineering projects, the soil nails are installed at a certain angle to the slope soil. However, existing soil nail pull-out model tests for measuring the ultimate friction strength of the soil nail-soil interface are mostly horizontal pull-out tests, neglecting the influence of the soil nail installation angle on the ultimate friction strength of the soil nail-soil interface. Utility Model Content

[0005] The purpose of this invention is to provide a measuring device for the ultimate friction strength of the soil nail-soil interface, so as to solve the problem that the existing technology is difficult to truly simulate the actual engineering environment.

[0006] To address the aforementioned technical problems, this utility model provides a measuring device and testing method for the ultimate frictional strength of the soil nail-soil interface, comprising an experimental chamber, a first support frame, a second support frame, and a computer. The experimental chamber is located within the space enclosed by the first support frame. Inside the experimental chamber are sensor components and a pre-embedded steel pipe arranged obliquely and removable. The upper end of the pre-embedded steel pipe is located outside the experimental chamber, and the interior of the pre-embedded steel pipe is used to insert reinforcing bars. The first support frame above the experimental chamber has a vertical force application mechanism and a water spraying mechanism. The vertical force application mechanism is used to compact the soil placed inside the experimental chamber, and the water spraying mechanism is used to spray water into the experimental chamber. The second support frame has a pull-out mechanism and a horizontal force application mechanism. The pull-out mechanism is used to pull the pre-embedded steel pipe out of the experimental chamber, and the horizontal force application mechanism is used to apply tension to the reinforcing bars. The computer is used to analyze the measurement data from the measuring device.

[0007] In one embodiment, two sets of the sensor groups are respectively arranged on both sides of the pre-embedded steel pipe, and the sensor groups include a soil moisture sensor, a pore pressure sensor and a soil pressure cell.

[0008] In one embodiment, the pulling mechanism includes a manual hoist, a steel cable, a fixed pulley, and a pre-drilled hole; the steel cable is wound around the manual hoist, passes through the pre-drilled hole after passing over the fixed pulley, and the steel cable is fitted around the end of the pre-embedded steel pipe located outside the experimental chamber.

[0009] In one embodiment, the horizontal force application mechanism includes a horizontal electric cylinder and a tension / compression sensor, wherein the force application end of the horizontal electric cylinder is connected to the reinforcing bar through the tension / compression sensor.

[0010] In one embodiment, the second support frame is provided with a height adjustment mechanism, and the height adjustment mechanism is provided with the horizontal force application mechanism. The height adjustment mechanism is used to adjust the installation height of the horizontal force application mechanism.

[0011] In one embodiment, the inclination angle of the pre-embedded steel pipe is 10° to 20°.

[0012] In one embodiment, a reinforcing bar fixing flange is provided at the lower end of the experimental chamber corresponding to the lower end of the pre-embedded steel pipe. The reinforcing bar fixing flange is connected to a reinforcing bar fixing rod, which is located inside the experimental chamber and is used to connect to the reinforcing bar. A reinforcing bar fixing cover is provided at the upper end of the experimental chamber corresponding to the upper end of the pre-embedded steel pipe. The reinforcing bar fixing cover is located outside the experimental chamber and is used for the reinforcing bar to pass through. The reinforcing bar fixing rod and the reinforcing bar fixing cover are used to arrange the reinforcing bar at the same angle as the pre-embedded steel pipe.

[0013] In one embodiment, the vertical force application mechanism includes a vertical electric cylinder and a loading plate, the force application end of the vertical electric cylinder being connected to the loading plate, and the loading plate being aligned with the top opening area of ​​the experimental chamber.

[0014] The beneficial effects of this utility model are as follows:

[0015] 1. In this utility model, the steel bars (i.e., soil nails) are installed at an angle of 10° to 20°, which is consistent with the actual soil nail installation project for slope support and can better simulate the actual project.

[0016] 2. This utility model installs an earth pressure cell within a certain range of the soil around the nail-soil interface to detect the earth pressure and its changes during the experiment in real time. This allows for a better study of the changes in earth pressure around the soil nail-supported slope under wet-dry cycles, providing a clearer understanding of the water weakening mechanism of the soil nail-soil interface.

[0017] 3. The soil nailing method of this utility model is to pour the soil on site. During the wet-dry cycle, the air drying is carried out by natural air drying. The test method ensures the integrity of the sample structure and the accuracy of the test results.

[0018] In summary, this utility model can be applied to the measurement of interfacial frictional resistance between different soil types and soil slope reinforcement materials. It takes into account the influence of the soil nail installation inclination angle on the nail-soil interface frictional resistance, which conforms to the actual working conditions of the nail-soil interface and surrounding soil changing with the number of wet and dry cycles during the soil nail support process of soil nail support slope. It can effectively reduce the influence of soil nail installation process and effectively solve the problem that existing technologies cannot truly simulate the actual engineering environment. Attached Figure Description

[0019] To more clearly illustrate the technical solution of this utility model, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a structural schematic diagram provided by an embodiment of the present utility model;

[0021] Figure 2 yes Figure 1 Schematic diagram of the horizontal force application mechanism;

[0022] Figure 3 yes Figure 1 A schematic diagram of the vertical force application mechanism;

[0023] Figure 4 yes Figure 1 A schematic diagram of the internal structure of the experimental chamber.

[0024] The attached figures are labeled as follows:

[0025] 10. Experimental chamber; 11. Embedded steel pipe; 12. Reinforcing bars; 13. Reinforcing bar fixing flange; 14. Reinforcing bar fixing rod; 15. Reinforcing bar fixing cover;

[0026] 21. First support frame; 22. Second support frame;

[0027] 30. Computer;

[0028] 40. Vertical force application mechanism; 41. Vertical electric cylinder; 42. Loading plate;

[0029] 50. Sprinkler system;

[0030] 60. Pulling mechanism; 61. Manual hoist; 62. Fixed pulley; 63. Pre-drilled hole;

[0031] 70. Horizontal force application mechanism; 71. Horizontal electric cylinder; 72. Tension / compression sensor;

[0032] 80. Height adjustment mechanism. Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention.

[0034] This invention provides a device and test method for measuring the ultimate frictional strength of the soil nail-soil interface, the implementation of which is as follows: Figures 1 to 4 As shown, the system includes an experimental chamber 10, a first support frame 21, a second support frame 22, and a computer 30. The experimental chamber 10 is located within the space enclosed by the first support frame 21. Inside the experimental chamber 10, there are sensor components and a diagonally arranged, retractable pre-embedded steel pipe 11. The upper end of the pre-embedded steel pipe 11 is located outside the experimental chamber 10, and the interior of the pre-embedded steel pipe 11 is used to insert reinforcing bars 12. The first support frame 21 has a vertical force application mechanism 40 and a water spraying mechanism 50 above the experimental chamber 10. The vertical force application mechanism 40 is used to compact the soil placed inside the experimental chamber 10, and the water spraying mechanism 50 is used to spray water into the experimental chamber 10. The second support frame 22 has a pulling mechanism 60 and a horizontal force application mechanism 70. The pulling mechanism 60 is used to pull the pre-embedded steel pipe 11 out of the experimental chamber 10, and the horizontal force application mechanism 70 is used to apply tension to the reinforcing bars 12. The computer 30 is used to analyze the measurement data of the measuring device.

[0035] Preferably, in this embodiment, two sets of sensor groups are arranged on both sides of the pre-embedded steel pipe 11. The sensor groups include a soil moisture sensor, a pore pressure sensor, and a soil pressure cell.

[0036] like Figure 1 and Figure 4 As shown, this embodiment sets the pulling mechanism 60, which includes a manual hoist 61, a steel cable, a fixed pulley 62, and a reserved hole 63. The manual hoist 61 is wound with a steel cable, which passes through the reserved hole 63 after passing around the fixed pulley 62, and the end of the steel cable is tightly fitted with the pre-embedded steel pipe 11 outside the experimental box 10.

[0037] With this setup, once the manual hoist 61 is turned, it can drive the steel cable to generate tension, thereby pulling out the pre-embedded steel pipe 11.

[0038] like Figure 1 , Figure 2 and Figure 4 As shown, this embodiment provides a horizontal force application mechanism 70, which includes a horizontal electric cylinder 71 and a tension / compression sensor 72. The force application end of the horizontal electric cylinder 71 is connected to the reinforcing bar 12 through the tension / compression sensor 72.

[0039] With this setup, the horizontal electric cylinder 71 will generate tension on the tension sensor 72, thereby pulling out the reinforcing bar 12.

[0040] like Figure 1 As shown, in this embodiment, a height adjustment mechanism 80 is provided on the second support frame 22, and a horizontal force application mechanism 70 is provided on the height adjustment mechanism 80. The height adjustment mechanism 80 is used to adjust the installation height of the horizontal force application mechanism 70. In this embodiment, the height adjustment mechanism 80 is a double-spoke handwheel, that is, the corresponding lifting and lowering control operation is realized by rotating the double-spoke handwheel.

[0041] like Figure 4 As shown, in this embodiment, the inclination angle of the pre-embedded steel pipe 11 is set to 10° to 20°, for example, in this embodiment, it is preferably set to 15°.

[0042] like Figure 1 and Figure 4 As shown, in this embodiment, a reinforcing bar fixing flange 13 is provided at the lower end of the experimental box 10 corresponding to the lower end of the pre-embedded steel pipe 11. The reinforcing bar fixing flange 13 is connected to a reinforcing bar fixing rod 14, which is located inside the experimental box 10 and is used to connect with the reinforcing bar 12. A reinforcing bar fixing cover 15 is provided at the upper end of the experimental box 10 corresponding to the upper end of the pre-embedded steel pipe 11. The reinforcing bar fixing cover 15 is located outside the experimental box 10 and is used for the reinforcing bar 12 to pass through. The reinforcing bar fixing rod 14 and the reinforcing bar fixing cover 15 are used to arrange the reinforcing bar 12 at the same tilt angle as the pre-embedded steel pipe 11.

[0043] like Figure 1 and Figure 3As shown, this embodiment provides a vertical force application mechanism 40 including a vertical electric cylinder 41 and a loading plate 42. The force application end of the vertical electric cylinder 41 is connected to the loading plate 42, and the loading plate 42 is aligned with the top opening area of ​​the experimental chamber 10.

[0044] After adopting this setting, the vertical electric cylinder 41 can generate pressure on the loading plate 42, thereby achieving the compaction of the soil sample; wherein, in this embodiment, there are two loading plates 42, one of which is directly connected to the vertical electric cylinder 41 and is equipped with a water spraying mechanism 50 in a detachable manner, while the other loading plate 42 can be used to prevent water from being sprayed on the soil in the experimental chamber 10.

[0045] To better illustrate the use of the aforementioned measuring device, this invention also provides a test method for the ultimate frictional strength of the soil nail-soil interface, which utilizes the aforementioned measuring device and specifically includes the following steps:

[0046] Step 1: Fill the test soil sample into the test chamber 10 in multiple layers. After each layer of test soil sample is filled, compact it before filling the next layer. When the test soil reaches the lowest point of the pre-embedded steel pipe 11, insert the pre-embedded steel pipe 11 into the test chamber 10 to reserve the position for cement grout pouring.

[0047] Specifically, in this embodiment, test soil samples are filled into the experimental chamber 10 in four layers, each layer being 20cm thick, for a total thickness of 0.8m. After each layer of backfilling, the soil is compacted until it reaches the density of its natural state before proceeding to the next layer. During the second layer of backfilling, when the soil height reaches the lowest point of the pre-embedded steel pipe 11, the pre-embedded steel pipe 11 is inserted into the experimental chamber 10 to reserve space for cement grout pouring.

[0048] Step 2: Arrange sensor groups on the left and right sides of the pre-embedded steel pipe 11, and send the data collected by the sensor groups to the computer 30.

[0049] Specifically, in this embodiment, sensors are pre-embedded at certain intervals on the surface of the pre-embedded steel pipe 11. Specifically, three soil moisture sensors and one pore pressure sensor are pre-embedded on each side of the pre-embedded steel pipe 11, for a total of eight sensors. A soil pressure box is pre-embedded at 10cm and 20cm above and below the pre-embedded steel pipe 11 and at 10cm to the left and right, for a total of six soil pressure boxes.

[0050] Step 3: After the soil loading of the experimental box 10 is completed, the steel bar 12 is installed in the pre-embedded steel pipe 11. The installation depth of the steel bar 12 is recorded as l, and the diameter of the steel bar 12 is recorded as D. The vertical force application mechanism 40 is activated to compact the soil in the experimental box 10. The pre-embedded steel pipe 11 is pulled out using the pull-out mechanism 60, and the prepared cement grout is poured into the reserved hole where the steel pipe is pulled out. After the pouring is completed, the prepared pull-out test model is left to stand for a preset time.

[0051] Step 4: Use the sprinkler mechanism 50 to sprinkle water until the soil nail-soil interface reaches saturation; then stop sprinkling water and let the soil in the test chamber 10 air dry naturally. When the saturation returns to the preset initial moisture content, start the sprinkler mechanism 50 again to make the soil in the test chamber 10 saturate again; repeat this process until the preset number of wet-dry cycles is reached.

[0052] Step 5: Use the vertical force application mechanism 40 to apply a slow thrust to the soil inside the test chamber 10 until the applied pressure reaches the preset value. Then, let it stand for a preset time to allow the excess pore pressure caused by the load to gradually dissipate to the value before the load was applied, and then start the soil nail pull-out test.

[0053] Specifically, in this embodiment, a 600mm*600mm*10mm loading plate 42 is placed on top of the soil layer as a cushion layer, and a slow load is applied on top of the steel plate to make the overburden pressure on the structure reach a predetermined value. After standing for a period of time, when the excess pore pressure caused by the load gradually dissipates to the value before the load is applied, the soil nail pull-out test is carried out.

[0054] Step 6: Activate the horizontal force application mechanism 70 and slowly pull out the steel bar 12 at the specified rate, and record the soil nail pull-out force T and soil nail displacement data s;

[0055] Step 7: The computer automatically records the soil nail pull-out force T, soil nail displacement data s, and soil pressure E changes around the soil nail during the experiment. It calculates the soil nail-soil ultimate friction q = T / πDl and plots the soil nail-soil ultimate friction curve with the number of wet-dry cycles and the soil pressure change curve during the experiment.

[0056] Step 8: According to the preset experimental plan, repeat steps 1 to 7 to conduct n sets of parallel experiments to obtain the results.

[0057]

[0058] This result represents the final soil nail-soil ultimate frictional resistance.

[0059] The above description is the preferred embodiment of this utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this utility model, and these improvements and modifications are also considered to be within the protection scope of this utility model.

Claims

1. A device for measuring the ultimate frictional strength of a soil nail-soil interface, characterized in that, Includes the experimental chamber, the first support frame, the second support frame, and the computer; The experimental chamber is located within the space enclosed by the first support frame. Inside the experimental chamber are sensor components and a pre-embedded steel pipe that is arranged at an angle and can be pulled out. The upper end of the pre-embedded steel pipe is located outside the experimental chamber, and the interior of the pre-embedded steel pipe is used to hold reinforcing bars. The first support frame is equipped with a vertical force application mechanism and a water spraying mechanism above the experimental box. The vertical force application mechanism is used to compact the soil placed inside the experimental box, and the water spraying mechanism is used to spray water into the experimental box. The second support frame is equipped with a pulling mechanism and a horizontal force application mechanism. The pulling mechanism is used to pull the pre-embedded steel pipe out of the experimental box, and the horizontal force application mechanism is used to apply tension to the steel bar. The computer is used to analyze the measurement data from the measuring device.

2. The measuring device according to claim 1, characterized in that, The two sets of sensors are respectively arranged on both sides of the pre-embedded steel pipe. The sensor sets include a soil moisture sensor, a pore pressure sensor, and a soil pressure cell.

3. The measuring device according to claim 1, characterized in that, The pulling mechanism includes a manual hoist, a steel cable, a fixed pulley, and a pre-drilled hole; The manual hoist is wound with the steel cable, which passes through the fixed pulley and then through the reserved hole. The end of the steel cable is fitted with the pre-embedded steel pipe outside the experimental box.

4. The measuring device according to claim 1, characterized in that, The horizontal force application mechanism includes a horizontal electric cylinder and a tension / compression sensor, and the force application end of the horizontal electric cylinder is connected to the reinforcing bar through the tension / compression sensor.

5. The measuring device according to claim 1, characterized in that, The second support frame is provided with a height adjustment mechanism, and the height adjustment mechanism is provided with the horizontal force application mechanism. The height adjustment mechanism is used to adjust the installation height of the horizontal force application mechanism.

6. The measuring device according to claim 1, characterized in that, The inclination angle of the pre-embedded steel pipe is 10° to 20°.

7. The measuring device according to claim 1, characterized in that, The experimental chamber is provided with a steel bar fixing flange at the lower end corresponding to the pre-embedded steel pipe. The steel bar fixing flange is connected to a steel bar fixing rod. The steel bar fixing rod is located inside the experimental chamber and is used to connect with the steel bar. The experimental chamber is provided with a steel bar fixing cover at the corresponding position of the upper end of the pre-embedded steel pipe. The steel bar fixing cover is located on the outside of the experimental chamber and is used for the steel bar to pass through. The reinforcing bar fixing rod and the reinforcing bar fixing cap are used to arrange the reinforcing bar at an angle consistent with the inclination angle of the pre-embedded steel pipe.

8. The measuring device according to claim 1, characterized in that, The vertical force application mechanism includes a vertical electric cylinder and a loading plate. The force application end of the vertical electric cylinder is connected to the loading plate, and the loading plate is aligned with the top opening area of ​​the experimental chamber.

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