Simulation experiment device and method for studying influence of filling consolidation on pile foundation

Abstract

The invention relates to the technical field of foundation engineering, in particular to a simulation experiment device and method for studying the influence of filling consolidation on a pile foundation. The simulation experiment device comprises a simulation cylinder, a loading chamber and a vacuum adsorption mechanism, the loading chamber is mounted at the upper part of the simulation cylinder, a first backfilling cavity is formed at the lower part of the simulation cylinder, and the first backfilling cavity is used for filling undisturbed soil; the loading chamber comprises a bottom partition plate, a sealing sleeve and a top cover plate, the bottom partition plate, the sealing sleeve and the top cover plate form a second backfill cavity, and the second backfill cavity is used for being filled with backfill soil; and the vacuum adsorption mechanism communicates with the second backfilling cavity and is used for vacuum consolidation of backfilled soil through negative pressure adsorption. By means of the simulation experiment device, the test result is closer to the actual situation, and the influence of filling consolidation on the pile foundation bearing capacity can be accurately evaluated.

Description

Technical Field

[0001] The invention relates to the technical field of foundation engineering, and in particular to a simulation experimental device and an experimental method for studying the influence of fill consolidation on pile foundations. Background Art

[0002] With the rapid development of infrastructure construction, a large amount of artificial backfill land is used for infrastructure construction. The mechanical properties of these backfill strata are poor, and they will produce consolidation effects over time, leading to pile foundation settlement and negative friction, affecting its bearing capacity. Therefore, it is of great significance to study the effect of fill consolidation on the bearing capacity of pile foundations.

[0003] At present, most experimental devices that simulate the impact of soil consolidation on pile foundations use jacks to apply pressure, so that the simulated soil produces a consolidation effect, thereby simulating the impact of soil consolidation on the pile foundation. However, this method is prone to produce a soil squeezing effect, and jack loading may cause uneven force on the soil. More importantly, this consolidation method ignores the fact that under real engineering conditions, soil consolidation only occurs in the upper backfill layer, while the lower original soil layer has a high density and the consolidation effect is not obvious, which can often be ignored. Therefore, the original test device cannot truly simulate the real impact of soil consolidation on the pile foundation. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the embodiments of the present invention is to provide a simulation experimental device and experimental method for studying the influence of fill consolidation on pile foundations. The device avoids the soil squeezing effect and can simulate the situation where only the upper backfill layer is consolidated while the lower original soil layer is not consolidated. The test results are closer to the actual situation, which helps to accurately evaluate the influence of fill consolidation on the bearing capacity of pile foundations.

[0005] In order to achieve the above object, the embodiment of the present invention provides the following technical solutions:

[0006] A simulation experimental device for studying the influence of fill consolidation on pile foundations, comprising: a simulation cylinder, a loading chamber and a vacuum adsorption mechanism; the loading chamber is installed on the upper part of the simulation cylinder, and a first backfill cavity is formed at the lower part of the simulation cylinder, and the first backfill cavity is used to fill the original soil; the loading chamber comprises a bottom partition, a sealing sleeve and a top cover plate, and the bottom partition, the sealing sleeve and the top cover plate form a second backfill cavity, and the second backfill cavity is used to fill the backfill soil; the vacuum adsorption mechanism is connected to the second backfill cavity, and is used for negative pressure adsorption to vacuum consolidate the backfill soil.

[0007] The embodiment of the present invention also provides an experimental method for the simulation experimental device for studying the influence of fill consolidation on pile foundation as described above, comprising: filling the simulated original soil in the first backfill cavity, and after the simulated original soil is filled, passing the pile foundation through the bottom partition, and when the passing length reaches the depth that the pile body should be inserted into the simulated original soil, the pile foundation together with the bottom partition and the sealing sleeve are placed into the simulated cylinder, and after the pile foundation is fixed, the bottom partition is placed flatly on the upper end of the simulated original soil; filling the simulated backfill soil into the second backfill cavity, filling the simulated backfill soil evenly and keeping the soil loose, and after the simulated backfill soil is filled, the top cover plate is put on the pile foundation and sealed with the sealing sleeve; vacuum adsorption of the loading chamber by the vacuum adsorption mechanism makes the upper backfill soil consolidated separately, and then a reaction force is applied to the pile foundation for testing.

[0008] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0009] This simulation experimental device uses vacuum adsorption to evacuate the soil in the sealing sleeve, and uses the atmospheric pressure to achieve soil consolidation. The soil is evenly stressed during consolidation, and the consolidation effect is good, which can more realistically reflect the impact of soil consolidation on the pile foundation. The backfill soil is loaded into an independent second backfill cavity and consolidated by vacuum adsorption. Therefore, it can be achieved that only the simulated backfill soil is consolidated, while the simulated original soil is not consolidated. The test results are more in line with actual engineering and help to accurately evaluate the impact of fill consolidation on the bearing capacity of the pile foundation.

[0010] Advantages of additional aspects of the present invention will be given in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In addition, the spacing or size between each other is exaggerated to show the position of each part, and the schematic diagram is only used for illustration.

[0012] Figure 1 is a schematic diagram of an experimental device provided by an embodiment of the present invention;

[0013] Figure 2 is a cross-sectional view of an experimental device provided by an embodiment of the present invention;

[0014] Figure 3 is a schematic diagram of a loading chamber provided by an embodiment of the present invention;

[0015] Figure 4 is a schematic diagram of a pressure plate provided by an embodiment of the present invention;

[0016] Figure 5 is a top view of a pressure bearing plate provided by an embodiment of the present invention;

[0017] Figure 6 is a schematic diagram of a sealing ring provided in an embodiment of the present invention;

[0018] Figure 7 is a schematic diagram of a loading mechanism provided by an embodiment of the present invention;

[0019] In the figure: 1, base; 2, simulated cylinder; 3, original soil; 4, sealing sleeve; 5, bottom partition; 6, pile foundation; 7, backfill soil; 8, top cover plate; 9, air extraction hole; 10, vacuum hose; 11, loading frame; 12, reaction jack; 13, top pressure plate; 14, bottom pressure plate; 15, sealing ring; DETAILED DESCRIPTION

[0020] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, it should also be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0021] As introduced in the background technology, the existing technology of jack loading simulation consolidation has the following problems: 1. Soil squeezing effect: jack loading may cause uneven force on the soil, which is inconsistent with the actual consolidation process. 2. Unable to simulate the situation of the upper backfill soil layer being consolidated alone: ​​The existing technology is difficult to simulate the effect of the upper backfill soil layer being consolidated alone on the pile foundation in actual engineering.

[0022] Overall design concept: The upper soil layer of the backfill stratum is backfill soil, which is loose and messy, with poor mechanical properties, while the lower soil layer is usually denser soil or rock with stable mechanical properties. During engineering construction, the foundation piles should use the soil layer with good mechanical properties as the bearing layer. Therefore, the foundation piles are interspersed with backfill soil and original soil under the backfill stratum. In the backfill stratum, the consolidation effect of the soil often occurs in the backfill soil stratum. Because the density of the original stratum soil is high, the consolidation effect is not obvious and can often be ignored. Therefore, a simulation experimental device is designed to simulate the consolidation of the upper backfill soil and the non-consolidation of the lower original soil. In addition, it is also necessary to consider the vertical force transmitted by the upper load on the foundation pile.

[0023] In order to simulate the soil consolidation process more realistically, this embodiment proposes a simulation experimental device for studying the influence of fill consolidation on pile foundation. The device mainly consists of a support base, a simulation cylinder, a top cover plate, a bottom partition plate, a sealing sleeve, a vacuum pump, and a loading reaction jack. The soil consolidation process is simulated by filling the simulated backfill soil in a rubber sleeve and using a vacuum pump for vacuum consolidation.

[0024] like Figure 1 , Figure 2 As shown, the simulation experimental device includes a simulation cylinder 2, a loading chamber and a vacuum adsorption mechanism; the loading chamber is installed at the upper part of the simulation cylinder 2, and a first backfilling cavity is formed at the lower part of the simulation cylinder 2, and the first backfilling cavity is used to fill the original soil 3; the loading chamber includes a bottom partition 5, a sealing sleeve 4 and a top cover plate 8, and the bottom partition 5, the sealing sleeve 4 and the top cover plate 8 form a second backfilling cavity, and the second backfilling cavity is used to fill the backfill soil 7; the vacuum adsorption mechanism is connected to the second backfilling cavity, and is used for negative pressure adsorption to vacuum consolidate the backfill soil 7.

[0025] In the simulation experiment device of this embodiment, the simulation cylinder 2 is the main structure of the device, which is used to accommodate and support the entire experimental process. The loading chamber is located at the upper part of the simulation cylinder 2, and its design allows the formation of a first backfill cavity at the lower part of the simulation cylinder 2, which is specifically used to fill the original soil 3, simulating the original soil 3 layers in the actual project. The loading chamber is composed of a bottom partition 5, a sealing sleeve 4 and a top cover plate 8. These components together form a second backfill cavity, which is used to fill the backfill soil 7, simulating the backfill soil 7 layers in the actual project. The vacuum adsorption mechanism is connected to the second backfill cavity, and the backfill soil 7 is vacuum consolidated by negative pressure adsorption to simulate the soil consolidation process.

[0026] This simulation experimental device uses vacuum adsorption to evacuate the soil in the sealing sleeve 4, and uses the atmospheric pressure to achieve soil consolidation. The soil is evenly stressed during consolidation, and the consolidation effect is good, which can more realistically reflect the impact of soil consolidation on the pile foundation 6. The backfill soil 7 is loaded into the independent second backfill cavity and consolidated by vacuum adsorption. Therefore, it can be achieved that only the simulated backfill soil 7 is consolidated, while the simulated original soil 3 is not consolidated. The test results are more in line with actual engineering and help to accurately evaluate the impact of backfill consolidation on the bearing capacity of the pile foundation 6.

[0027] A base 1 is provided at the bottom of the simulated cylinder 2, and the upper end of the base 1, the inner wall of the simulated cylinder 2 and the lower end of the bottom partition 5 form a first backfill cavity filled with the original soil 3. The base 1 provides a stable support to ensure the stability of the simulated cylinder 2 during the experiment. The upper end of the base 1, the inner wall of the simulated cylinder 2 and the lower end of the bottom partition 5 together form a first backfill cavity filled with the original soil 3, ensuring that the simulation of the original soil 3 layer is closer to the actual engineering situation.

[0028] The sealing sleeve 4 of the loading chamber is made of rubber material with good elasticity and sealing performance. The lower end of the rubber sleeve is sealed with the bottom partition 5, and the upper end is sealed with the top cover 8, ensuring the sealing of the backfill soil 7 in the second backfill cavity during the vacuum adsorption process.

[0029] The bottom partition plate 5 and the top cover plate 8 are both disc-shaped structures, and the outer circumference of the disc-shaped structure is concave in the radial direction to form an annular groove, and the upper and lower ends of the sealing sleeve 4 are wrapped around the groove and tied tightly. The rubber sleeve is sealed by tightly tying the bottom and the top of the rubber sleeve to the concave parts around the disc body of the bottom partition plate 5 and the top cover plate 8, respectively, to enhance the sealing and stability of the device.

[0030] The vacuum adsorption mechanism includes a vacuum pump and a vacuum hose 10. The top cover plate 8 is provided with an air extraction hole 9. One end of the vacuum hose 10 is connected to the vacuum pump, and the other end of the vacuum hose 10 is connected to the second backfill cavity through the air extraction hole 9. This design enables the vacuum pump to efficiently perform negative pressure adsorption on the backfill soil 7 in the second backfill cavity to achieve vacuum consolidation.

[0031] The bottom partition plate 5 and the top cover plate 8 are respectively composed of a pressure plate and a sealing ring 15. Figure 3 , Figure 4 As shown, the top cover plate 8 includes a top pressure plate 13 and a sealing ring 15, the top pressure plate 13 has a center hole, and the sealing ring 15 is embedded in the center hole of the top pressure plate 13, the bottom partition plate 5 includes a bottom pressure plate 14 and a sealing ring 15, the bottom pressure plate 14 has a center hole, and the sealing ring 15 is embedded in the center hole of the bottom pressure plate 14, and the pile foundation 6 passes through the top cover plate 8 and the sealing ring 15 of the bottom partition plate 5, passes through the backfill soil 7 and is inserted into the original soil 3. In the simulation experiment, the pile foundation 6 in the actual project is simulated, and the sealing and structural integrity of the device are ensured at the same time.

[0032] The pressure plate of the top cover plate 8 has a suction hole 9, while the pressure plate of the bottom partition plate 5 has no suction hole 9. Figure 5 As shown, the sealing ring 15 is a hollow ring with a pile hole reserved in the middle. By prefabricating sealing rings 15 with different hole diameters, when conducting a consolidation test, suitable sealing rings 15 are selected for adaptation according to different pile diameters, so that the device can conduct consolidation tests under different pile diameters, thereby improving the utilization rate of the device.

[0033] The center holes of the top pressure plate 13 and the bottom pressure plate 14 are both tapered holes, wherein the diameter of the tapered hole of the top pressure plate 13 is larger at the top and smaller at the bottom, and the diameter of the tapered hole of the bottom pressure plate 14 is smaller at the top and larger at the bottom. This tapered design helps to position and fix the pile foundation 6, and provides a better sealing effect.

[0034] like Figure 6As shown, a sleeve pile cylinder is provided in the sealing ring 15 of the top cover plate 8. A rubber pad is provided inside the sleeve pile cylinder. The inner ring of the rubber pad bends upward and fits on the pile foundation 6. A sleeve pile cylinder is also provided in the sealing ring 15 of the bottom partition plate 5. A rubber pad is provided inside the sleeve pile cylinder. The inner ring of the rubber pad bends downward and fits on the pile foundation 6.

[0035] For the three-layer bent rubber pad inside the sleeve pile cylinder, during use, apply sealing grease to the rubber pad inside the sleeve pile cylinder. Due to the bending of the rubber pad, when the pile foundation 6 is inserted into the sleeve pile cylinder, the rubber pad will closely fit on the pile foundation 6, ensuring the airtightness of the device. This design utilizes the bent structure of the rubber pad to improve the airtightness of the device and ensure the sealing effect during the vacuum adsorption process.

[0036] Since under actual working conditions, the pile foundation 6 will also be subjected to the vertical load transmitted by the upper building, the influence of the vertical pressure on the pile foundation 6 cannot be ignored. Therefore, it is necessary to apply appropriate loading to the pile foundation 6 to simulate the most realistic engineering situation.

[0037] Based on this, this simulation experimental device also includes a loading mechanism, as Figure 7 shown. The loading mechanism includes a loading frame 11 and a reaction jack 12. The loading frame 11 is in a U shape. The reaction jack 12 is installed in the middle of the loading frame 11 to apply a reaction force to the pile foundation 6. The loading frame 11 is welded by three steel beams and a square base 1, providing a stable support structure. The reaction jack 12 is installed in the middle of the cross beam, and the lower part is aligned with the end of the pile foundation 6 to achieve the effect of applying pressure and simulate the upper load on the pile foundation 6 in actual engineering.

[0038] The experimental method of the above simulation experimental device for studying the influence of soil consolidation on the pile foundation 6 includes:

[0039] When conducting the vacuum preloading soil consolidation test, first place the simulation cylinder 2 on a flat and open site and carry out the filling of the simulated soil. During filling, the thickness of the soil layer is proportionally distributed according to the actual engineering situation. After determining the thickness of the simulated undisturbed soil 3 to be filled, fill the simulated undisturbed soil 3. The simulated undisturbed soil 3 should be filled densely to simulate the real engineering situation.

[0040] After the simulated original soil 3 is filled, select the sealing ring 15 that matches the pile foundation 6 of the simulation test, and put the sealing ring 15 into the pressure plate without the exhaust hole 9 (smear the sealing grease on the contact between the sealing ring 15 and the pressure plate in advance), assemble it into the bottom partition 5, and then tie one end of the rubber sleeve tightly to the inner concave part of the outer periphery of the bottom partition 5 with wire. After the lower end of the rubber sleeve is fixed, the pile foundation 6 is passed through the pile sleeve on the bottom partition 5 (the rubber pad in the pile sleeve is sealed with grease). When the passing length reaches the depth that the pile body should be inserted into the simulated original soil 3, the pile foundation 6 together with the bottom partition 5 and the rubber sleeve are placed in the simulated cylinder 2 (the pile foundation 6 is fixed at the center of the simulated cylinder 2). After the pile foundation 6 is fixed, the bottom partition 5 is placed flatly on the upper end of the simulated original soil 3.

[0041] After the pile foundation 6, rubber sleeve and bottom partition 5 are fixed, simulated backfill soil 7 is loaded into the rubber sleeve, the thickness of simulated backfill soil 7 is determined, and the simulated backfill soil 7 is loaded evenly to keep the soil loose. After the simulated backfill soil 7 is loaded, the sealing ring 15 is inserted into the pressure plate with the air extraction hole 9 (the sealing grease is applied in advance at the contact point between the sealing ring 15 and the pressure plate), and the top cover plate 8 is assembled, and the pile sleeve on the top cover plate 8 is sleeved on the pile foundation 6 (the rubber pad in the pile sleeve is sealed with grease), and after the top cover plate 8 is flatly covered on the top of the simulated backfill soil 7, the upper end of the rubber sleeve is tightly tied to the inner concave part of the outer periphery of the top cover plate 8 with wire, and the upper end of the rubber sleeve is fixed, so that the upper end, lower end and the insertion point of the pile foundation 6 are all in a sealed state, which ensures the sealing of the device during vacuum extraction.

[0042] There are two small holes on the top cover plate 8 as air extraction holes 9. Put the vacuum hose 10 on the air extraction holes 9 and fix it. The hose is connected to the vacuum pump. Put the loading frame 11 on the top of the consolidation device, align the reaction jack 12 with the top of the pile foundation 6, and apply a certain pressure to simulate the upper load of the building. After checking that there are no errors in the above steps, connect the vacuum pump to the power supply and perform the vacuum consolidation test.

[0043] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A simulation experimental device for studying the influence of fill consolidation on pile foundation, characterized in that: Comprising: A simulated cylinder, a loading chamber, and a vacuum adsorption mechanism; The loading chamber is installed at the upper part of the simulated cylinder, and a first backfill cavity is formed at the lower part of the simulated cylinder for filling undisturbed soil; The loading chamber includes a bottom partition board, a sealing sleeve, and a top cover plate. The bottom partition board, the sealing sleeve, and the top cover plate form a second backfill cavity for filling backfill soil; The vacuum adsorption mechanism is communicated with the second backfill cavity and is used for negative pressure adsorption to vacuum consolidate the backfill soil.

2. The simulation experimental device for studying the influence of fill consolidation on pile foundation according to claim 1, characterized in that: A base is arranged at the bottom of the simulated cylinder. The upper end of the base, the inner wall of the simulated cylinder, and the lower end of the bottom partition board enclose the first backfill cavity for filling undisturbed soil.

3. The simulation experimental device for studying the influence of fill consolidation on pile foundation according to claim 1, characterized in that: The sealing sleeve is a rubber sleeve. The lower end of the rubber sleeve is hermetically connected to the bottom partition board, and the upper end of the rubber sleeve is hermetically connected to the top cover plate.

4. The simulation experimental device for studying the influence of fill consolidation on pile foundation according to claim 3, characterized in that: Both the bottom partition board and the top cover plate are disc-shaped structures. The outer peripheral surface of the disc-shaped structure is concave in the radial direction to form an annular groove. The upper end and the lower end of the sealing sleeve are wrapped on the groove and tied tightly.

5. The simulation experimental device for studying the influence of fill consolidation on pile foundation according to claim 1, characterized in that: The vacuum adsorption mechanism includes a vacuum pump and a vacuum hose. An air extraction hole is arranged on the top cover plate. One end of the vacuum hose is communicated with the vacuum pump, and the other end of the vacuum hose is communicated with the second backfill cavity through the air extraction hole.

6. The simulation experimental device for studying the influence of fill consolidation on pile foundation according to claim 1, characterized in that: The top cover plate includes a top bearing plate and a sealing ring. The top bearing plate has a central hole, and the sealing ring is embedded in the central hole of the top bearing plate. The bottom partition board includes a bottom bearing plate and a sealing ring. The bottom bearing plate has a central hole, and the sealing ring is embedded in the central hole of the bottom bearing plate. The pile foundation penetrates through the sealing rings of the top cover plate and the bottom partition board, passes through the backfill soil, and is inserted into the undisturbed soil.

7. The simulation experimental device for studying the influence of fill consolidation on pile foundation according to claim 6, characterized in that: The central holes of the top bearing plate and the bottom bearing plate are both tapered holes. Among them, the diameter of the tapered hole of the top bearing plate is larger at the top and smaller at the bottom, and the diameter of the tapered hole of the bottom bearing plate is smaller at the top and larger at the bottom.

8. The simulation experimental device for studying the influence of fill consolidation on pile foundation according to claim 6, characterized in that: A pile sleeve is arranged in the sealing ring of the top cover plate. A rubber pad is arranged in the pile sleeve. The inner ring of the rubber pad is bent upwards and fits on the pile foundation. A pile sleeve is also arranged in the sealing ring of the bottom partition board. A rubber pad is arranged in the pile sleeve. The inner ring of the rubber pad is bent downwards and fits on the pile foundation.

9. The simulation experimental device for studying the influence of fill consolidation on pile foundation according to claim 1, characterized in that: The simulation experiment device further includes a loading mechanism. The loading mechanism includes a loading frame and a reaction jack. The loading frame is in a U-shaped shape, and the reaction jack is installed in the middle of the loading frame for applying a reaction force to the pile foundation.

10. An experimental method for a simulation experimental device for studying the influence of fill consolidation on pile foundation according to any one of claims 1 to 9, characterized in that: Comprising: Fill the first backfill cavity with simulated undisturbed soil. After the simulated undisturbed soil is filled, pass the pile foundation through the bottom partition board. When the penetration length reaches the depth that the pile body should be inserted into the simulated undisturbed soil, put the pile foundation together with the bottom partition board and the sealing sleeve into the simulated cylinder. After the pile foundation is fixed, the bottom partition board is placed flat on the upper end of the simulated undisturbed soil; Fill the second backfill cavity with simulated backfill soil. When filling the simulated backfill soil, fill it evenly and keep the soil in a loose state. After the simulated backfill soil is filled, then put the top cover plate on the pile foundation and seal it with the sealing sleeve; Through the vacuum adsorption mechanism, vacuum adsorb the loading chamber to separately consolidate the upper backfill soil, and then apply a reaction force to the pile foundation for testing.

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