A soil arch effect attenuation test device and method under rainfall and water level changes

Abstract

The present invention discloses a soil arch effect attenuation test device and method under rainfall and water level changes, comprising a closely connected test trough box, a first water tank and a second water tank, wherein the contacting side walls of the three are provided with circular holes and covered with a permeable geotextile for allowing water to pass through; wherein the test trough box is divided into a water area and a soil area by a partition plate; the soil area of ​​the test trough box is filled with foundation soil and square piles are arranged, and embankment fill is laid on the top of the foundation soil; the second water tank is provided with a drainage pipe, and a drainage valve is arranged on the drainage pipe. The third water tank supplies water to the first water tank through a pressure pump to provide horizontal seepage; the third water tank is connected to a rainfall nozzle in another way to provide vertical seepage for the test trough box. The present invention simulates the working conditions of a pile-supported embankment under groundwater level changes and rainfall to explore the performance of the soil arch effect under different horizontal seepage velocities and vertical seepage under heavy rainfall and water level changes.

Description

Technical Field

[0001] The invention relates to the technical field of highway foundation, in particular to a soil arch effect attenuation test device and method under rainfall and water level changes. Background Art

[0002] In the south, especially during the rainy season, the rainfall lasts for a long time and is very intense. Pile-supported embankments are often used in highway construction because of their low cost and fast construction speed. The safety of pile-supported embankments is mainly due to the formation of soil arches in the embankment, which transfers most of the weight of the embankment to the pile body. The bearing capacity is small on soft soil with low bearing capacity, ensuring the safety of the highway. However, under heavy rainfall and water level changes, the soil arch effect is affected by rainfall and water level changes, and the soil arch rate is reduced, affecting safety. In particular, there is a lack of systematic theoretical analysis and research in its theory.

[0003] Terzaghi confirmed the existence of soil arching effect through the sliding door test. The reason for the formation of soil arching is that the stiffness of the piles and the soil between the piles in the embankment is very different, and the soil arching is formed due to the uneven settlement of the embankment fill. Under the adverse effects of heavy rainfall and water level changes, the theoretical significance of studying the attenuation of soil arching effect is great.

[0004] In the field test, due to the lack of corresponding test conditions and the inability to control the required different extreme test conditions, the purpose of the test research cannot be achieved. Therefore, it is urgent to invent an attenuation test device that simulates the soil arch effect of a pile-supported embankment under the coupling of heavy rainfall and water level changes. Summary of the invention

[0005] The technical problem to be solved by the present invention is to address the deficiencies of the above-mentioned prior art and to provide a test device and method for the attenuation of soil arch effect under rainfall and water level changes. The present invention simulates the test conditions of a pile-supported embankment under groundwater level changes and rainfall to explore the performance of the soil arch effect at different horizontal seepage velocities under heavy rainfall and water level changes, as well as the influence of the soil arch effect under the coupling of rainfall and water level changes.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A soil arch effect attenuation test device under rainfall and water level changes comprises a test tank body, a first water tank, a second water tank and a third water tank.

[0008] The test tank box is a rectangle with an open top, and circular holes are respectively opened on a pair of opposite test tank box side walls; a partition plate is arranged in the test tank box, and the partition plate is parallel to the test tank box side wall with the circular holes; the partition plate divides the test tank box into a water area and a soil area.

[0009] Square piles are arranged in the soil area of ​​the test trough box. The square piles are set vertically and their height is lower than the partition plate. The soil area of ​​the test trough box is filled with foundation soil, which covers and wraps the square piles. Embankment fill is laid on the top of the foundation soil.

[0010] The first water tank and the second water tank are respectively arranged on both sides of the test tank box, and the first water tank is connected to the water area of ​​the test tank box through a side wall of the test tank box with a circular hole, and the second water tank is connected to the soil area of ​​the test tank box through another side wall of the test tank box with a circular hole.

[0011] The second water tank is provided with a drain pipe, and a drain valve is arranged on the drain pipe.

[0012] The third water tank is provided with two outlets, one outlet is connected to the first water tank through a pipeline, and the other outlet is connected to a rainfall sprinkler arranged on the top of the test tank box frame through a pipeline.

[0013] A pressure pump is arranged on the pipeline between the third water tank and the first water tank; a pressure pump is also arranged on the pipeline between the third water tank and the rainfall sprinkler.

[0014] Further preferably, the test tank body is made of tempered glass to facilitate observation of water level changes and soil changes.

[0015] Further preferably, a flow meter is arranged on the pipeline between the third water tank and the first water tank; a flow meter is also arranged on the pipeline between the third water tank and the rainfall sprinkler.

[0016] Further preferably, permeable geotextiles are laid on the two side walls and the partition plate of the test tank box with the circular hole to prevent the foundation soil from seeping out through the circular hole.

[0017] Further preferably, the height of the foundation soil filled in the soil area of ​​the test tank box is lower than the height of the partition plate.

[0018] Further preferably, soil pressure boxes, water content sensors and pore water pressure gauges are arranged in the embankment fill.

[0019] Further preferably, it also includes a test tank box frame, which is used to accommodate the test tank box and provide stable reinforcement support for the test tank box.

[0020] A soil arching effect attenuation test method under rainfall and water level changes specifically comprises the following steps:

[0021] S1, changing the water pressure entering the first water tank by a pressure pump on the pipeline between the third water tank and the first water tank, thereby controlling the water inlet flow rate of the first water tank, and observing the water inlet flow rate by a flow meter;

[0022] S2. Observe through the test tank body and wait for water to penetrate from the first water tank into the water area of ​​the test tank body and the soil area of ​​the test tank body in sequence until it enters the second water tank, then close the drainage valve;

[0023] S3, the water level in the second water tank continues to rise, the drainage valve is opened, and the horizontal seepage speed of water in the foundation soil is controlled by controlling the water head difference between the first water tank and the second water tank;

[0024] S4, turn on the booster pump on the pipeline between the third water tank and the rainfall sprinkler, adjust the booster pump to adjust the water pressure entering the rainfall sprinkler; observe the rainfall flow through the flow meter on this pipeline; the water level sprayed by the rainfall sprinkler flows vertically, penetrates into the foundation soil through the embankment fill;

[0025] S5. There is horizontal seepage and vertical seepage in the foundation soil. Under the coupling effect of rainfall and water level changes, the water level rise in the second water tank is observed, thereby reflecting the change in the seepage velocity of the foundation soil under rainfall and water level changes.

[0026] The present invention has the following beneficial effects:

[0027] 1. The present invention simulates the process of soil arch effect attenuation under the coupling effect of rainfall and water level change. The water absorption in the first water tank is controlled by adjusting the pressure pump, and the water inflow is determined by the flow meter. Because the permeability of the foundation soil is low, the water level in the first water tank rises faster, and the water level in the second water tank changes slowly. With the increase of the water level height and the water inflow in the first water tank, the seepage rate through the foundation soil is gradually accelerated, and the water level in the second water tank gradually rises. By controlling the head difference between the two water tanks, the seepage rate in the foundation soil can be adjusted to simulate the influence of different horizontal seepage rates on the soil arch effect of the foundation soil and embankment fill, thereby exploring the influence of water level changes on the soil arch effect.

[0028] 2. The present invention controls the rainfall nozzle through a pressure pump to achieve the change of rainfall intensity, and realizes the water level rise in the water tank by controlling the water injection amount in the first water tank. There is vertical seepage in the embankment fill due to rainfall, which seeps into the foundation soil through the embankment fill; in the foundation soil, there is seepage under the coupling effect of rainfall and water level change. The water level rise in the water tank can be observed in the second water tank, and the change of the seepage speed of the foundation soil under rainfall and water level change can be reflected. The water level change of the second water tank can be controlled through the drain outlet, so as to explore the influence of the coupling effect of rainfall and water level change on the soil arch effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a schematic structural diagram of a soil arch effect attenuation test device under rainfall and water level changes.

[0030] Figure 2The invention discloses a schematic diagram of a test tank box side wall with a circular hole in a soil arch effect attenuation test device under rainfall and water level changes.

[0031] The components include: 1. Test tank box frame; 2. Test tank box; 3. First water tank; 4. Second water tank; 5. Third water tank; 6. Partition plate; 7. Square piles; 8. Drain pipe; 9. Drain valve; 10. Rainfall sprinkler; 11. Pressure pump; 12. Flow meter; 13. Permeable geotextile; 14. Soil pressure box; 15. Water content sensor; 16. Pore water pressure gauge. DETAILED DESCRIPTION

[0032] In the description of the present invention, it should be understood that the terms "left side", "right side", "upper part", "lower part" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. "First", "second" and the like do not indicate the importance of the components, and therefore cannot be understood as limiting the present invention. The specific dimensions used in this embodiment are only for illustrating the technical solution, and do not limit the scope of protection of the present invention.

[0033] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific preferred embodiments.

[0034] like Figure 1 As shown, a soil arch effect attenuation test device under rainfall and water level changes includes a test tank box 2, a first water tank 3, a second water tank 4, and a third water tank 5.

[0035] The test tank box frame 1 is used to accommodate the test tank box 2 and play a supporting and stabilizing role. The test tank box frame 1 uses an angle steel with a length of 3m, a size of 50mm, and a thickness of 6mm.

[0036] The test tank box 2 is a rectangular box with an open top. Figure 2 As shown, circular holes are respectively opened on the side walls of a pair of opposite test trough boxes. The size of the circular holes is designed according to the actual working conditions. Due to the presence of the permeable geotextile, large holes will not cause leakage of foundation soil.

[0037] A partition plate 6 is arranged in the test tank box, and the partition plate 6 is parallel to the side wall of the test tank box with the circular hole; the partition plate 6 divides the test tank box into a water area and a soil area.

[0038] Permeable geotextiles 13 are laid on the two side walls of the test tank box 2 and the partition plate 6 to prevent the foundation soil from seeping through the circular hole. The size of the circular hole is d=12 cm.

[0039] The test tank box 2 is made of tempered glass, which is convenient for observing water level changes and soil changes. The side wall glass size is 2m×2m, the thickness is 12mm, and the partition board size is 1.988m long, 12mm thick, and 1.2m high.

[0040] Square piles 7 are evenly arranged in the soil area of ​​the test tank box, and the square piles 7 are arranged vertically. Preferably, 12 square piles are arranged, and each square pile is 0.1m×0.1m×1m. Foundation soil is filled in the soil area of ​​the test tank box, and the foundation soil covers and wraps the square piles 7. The height of the filled foundation soil is lower than the height of the partition plate 6; embankment fill is laid on the top of the foundation soil, and the embankment fill is in the shape of a trapezoid with a slope at the top. Earth pressure box 14, water content sensor 15, and pore water pressure gauge 16 are arranged in the embankment fill.

[0041] The first water tank 3 and the second water tank 4 are respectively arranged on both sides of the test tank box, and the first water tank 3 is connected to the water area of ​​the test tank box through a side wall of the test tank box with a circular hole, and the second water tank 4 is connected to the soil area of ​​the test tank box through another side wall of the test tank box with a circular hole.

[0042] The second water tank 4 is provided with a drain pipe 8 , and a drain valve 9 is provided on the drain pipe 8 .

[0043] Thus, the first water tank 3, the test tank box 2 and the second water tank 4 are connected as a whole, and water can sequentially penetrate the water area of ​​the test tank box 2, the soil area of ​​the test tank box 2, and the second water tank 4 from the first water tank 3, and finally flow out from the drainage pipe of the second water tank 4. The purpose of setting the water area of ​​the test tank box 2 is to provide a buffer zone for water to enter the foundation soil, so as to prevent water from suddenly entering the soil area of ​​the test tank box 2, impacting the foundation soil, and destroying the soil.

[0044] The third water tank 5 is provided with two outlets, one outlet is connected to the first water tank 3 through a pipeline, and the other outlet is connected to the rainfall sprinkler 10 arranged on the top of the test tank box frame through a pipeline.

[0045] A booster pump 11 and a flow meter 12 are arranged on the pipeline between the third water tank 5 and the first water tank 3 ; a booster pump 11 and a flow meter 12 are also arranged on the pipeline between the third water tank 5 and the rainfall sprinkler 10 .

[0046] The test tank box frame 1, test tank box 2, first water tank 3, second water tank 4, and third water tank 5 of the present invention are scaled according to a 1:5 ratio for actual devices, replicating the test conditions of the pile-supported embankment under actual conditions of groundwater level changes and rainfall.

[0047] Based on the above-mentioned test model device, there is a test method for attenuation of soil arch effect under rainfall and water level changes, which simulates the test conditions of pile-supported embankments under groundwater level changes and rainfall, to explore the performance of soil arch effect at different horizontal seepage velocities under heavy rainfall and water level changes, as well as the influence of soil arch effect under the coupling of rainfall and water level changes.

[0048] The specific steps include:

[0049] S1, changing the water pressure entering the first water tank 3 by the booster pump 11 on the pipeline between the third water tank 5 and the first water tank 3, thereby controlling the water flow rate of the first water tank 3, and observing the water flow rate by the flow meter 12;

[0050] S2, observe through the test tank box, wait for the water to penetrate from the first water tank 3 into the water area of ​​the test tank box and the soil area of ​​the test tank box in sequence, until entering the second water tank 4, and then close the drainage valve 9;

[0051] S3, the water level in the second water tank 4 continues to rise, and the drainage valve 9 is opened to control the water head difference between the first water tank 3 and the second water tank 4 to control the horizontal seepage speed of water in the foundation soil;

[0052] S4, turn on the booster pump 11 on the pipeline between the third water tank 5 and the rainfall nozzle, and adjust the water pressure entering the rainfall nozzle through the booster pump 11; observe the rainfall flow through the flow meter 12 on this pipeline; the water level sprayed by the rainfall nozzle 10 seeps vertically, penetrates into the foundation soil through the embankment fill;

[0053] S5. There is horizontal seepage and vertical seepage in the foundation soil. Under the coupling effect of rainfall and water level change, the water level rise of the second water tank 4 is observed, thereby reflecting the change of the foundation soil seepage velocity under rainfall and water level change.

[0054] The present invention simulates the process of soil arch effect attenuation under the coupling effect of rainfall and water level change. The water absorption in the first water tank is controlled by adjusting the pressure pump, and the water inflow is determined by the flow meter. Because the permeability of the foundation soil is low, the water level in the first water tank rises faster, and the water level in the second water tank changes slowly. With the increase of the water level height and the water inflow in the first water tank, the seepage speed through the foundation soil is gradually accelerated, and the water level in the second water tank gradually rises. By controlling the head difference between the two water tanks, the seepage speed in the foundation soil can be adjusted to simulate the influence of different horizontal seepage speeds on the soil arch effect of the foundation soil and embankment fill, thereby exploring the influence of water level changes on the soil arch effect.

[0055] Secondly, the present invention controls the rainfall nozzle through a pressure pump to achieve the change of rainfall intensity, and realizes the water level rise in the water tank by controlling the water injection amount in the first water tank. There is vertical seepage in the embankment fill due to rainfall, which seeps into the foundation soil through the embankment fill; in the foundation soil, there is seepage under the coupling effect of rainfall and water level change. The water level rise in the water tank can be observed in the second water tank, and the change of the seepage speed of the foundation soil under rainfall and water level change can be reflected. The water level change of the second water tank can be controlled through the drain outlet, so as to explore the influence of the coupling effect of rainfall and water level change on the soil arch effect.

[0056] Therefore, the present invention can simulate the influence of different horizontal seepage velocities and vertical seepage velocities on the soil arch effect under heavy rainfall and water level changes through the device.

[0057] The preferred embodiments of the present invention are described in detail above; however, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all belong to the protection scope of the present invention.

Claims

1. A soil arch effect attenuation test device under rainfall and water level changes, characterized in that: It comprises a test tank body (2), a first water tank (3), a second water tank (4), and a third water tank (5); The test tank box (2) is a rectangular box with an open top, wherein a pair of opposite test tank box side walls are respectively provided with circular holes; a partition plate (6) is arranged in the test tank box, and the partition plate (6) is parallel to the test tank box side wall with the circular holes; the partition plate (6) divides the test tank box into a water area and a soil area; Arranging square piles (7) in the soil area of ​​the test tank box, the square piles (7) are arranged vertically and their height is lower than the partition plate (6); filling the soil area of ​​the test tank box with foundation soil, the foundation soil covering and wrapping the square piles (7); laying embankment fill soil on top of the foundation soil; The first water tank (3) and the second water tank (4) are respectively arranged on both sides of the test tank box, and the first water tank (3) is connected to the water area of ​​the test tank box through a side wall of the test tank box with a circular hole, and the second water tank (4) is connected to the soil area of ​​the test tank box through another side wall of the test tank box with a circular hole; The second water tank (4) is provided with a drainage pipe (8), and a drainage valve (9) is provided on the drainage pipe (8); The third water tank (5) is provided with two outlets, one of which is connected to the first water tank (3) through a pipeline, and the other of which is connected to a rainfall sprinkler (10) arranged on the top of the test tank box frame through a pipeline; A pressure pump (11) is provided on the pipeline between the third water tank (5) and the first water tank (3); a pressure pump (11) is also provided on the pipeline between the third water tank (5) and the rainfall sprinkler (10); The height of the foundation soil filled in the soil area of ​​the test tank box is lower than the height of the partition plate (6); An earth pressure box (14), a water content sensor (15) and a pore water pressure gauge (16) are arranged in the embankment fill.

2. The soil arching effect attenuation test device under rainfall and water level changes according to claim 1 is characterized by: The test tank box (2) is made of tempered glass, which is convenient for observing water level changes and soil changes.

3. The soil arching effect attenuation test device under rainfall and water level change according to claim 2 is characterized by: A flow meter (12) is arranged on the pipeline between the third water tank (5) and the first water tank (3); a flow meter (12) is also arranged on the pipeline between the third water tank (5) and the rainfall sprinkler.

4. The soil arching effect attenuation test device under rainfall and water level change according to claim 3 is characterized by: Water-permeable geotextiles (13) are laid on the two side walls of the test tank box (2) with the circular hole and the partition plate (6) to prevent the foundation soil from seeping out through the circular hole.

5. The soil arching effect attenuation test device under rainfall and water level change according to claim 3 is characterized by: It also comprises a test tank box frame (1), which is used to accommodate the test tank box (2) and provide stable reinforcement support for the test tank box (2).

6. A soil arching effect attenuation test method under rainfall and water level changes according to any one of claims 3 to 5, characterized in that: The specific steps include: S1, changing the water pressure entering the first water tank (3) by means of a booster pump (11) on the pipeline between the third water tank (5) and the first water tank (3), thereby controlling the water inlet flow rate of the first water tank (3), and observing the water inlet flow rate by means of a flow meter (12); S2. Observe through the test tank body and wait for water to penetrate from the first water tank (3) into the water area of ​​the test tank body and the soil area of ​​the test tank body in sequence until it enters the second water tank (4), and then close the drainage valve (9); S3, the water level in the second water tank (4) continues to rise, the drainage valve (9) is opened, and the horizontal seepage velocity of water in the foundation soil is controlled by controlling the water head difference between the first water tank (3) and the second water tank (4); S4, turning on the booster pump (11) on the pipeline between the third water tank (5) and the rainfall nozzle, adjusting the water pressure entering the rainfall nozzle by means of the booster pump (11); observing the rainfall flow rate by means of the flow meter (12) on the pipeline; the water level sprayed by the rainfall nozzle (10) seeps vertically, penetrates into the foundation soil through the embankment fill; S5. In the foundation soil, there is horizontal seepage and vertical seepage. Under the coupling effect of rainfall and water level change, the water level rise of the second water tank (4) is observed, thereby reflecting the change of the seepage velocity of the foundation soil under rainfall and water level change.

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