Physical model test device for testing anti-pulling performance of non-soil-squeezing precast pile foundation

Abstract

The utility model relates to the technical field of pile foundation engineering, and particularly discloses a physical model test device for testing the anti-pulling performance of a non-soil-squeezing precast pile foundation, which comprises a multifunctional cement grouting machine, a slurry storage pool, a vacuum pump, a water storage tank, a vacuum water pumping pipe, a model box bottom plate, a model box side plate and a high-strength toughened glass plate, and the output end of the multifunctional cement grouting machine is communicated with the outer surface of the slurry storage tank. According to the large-diameter non-soil-squeezing uplift pile construction device, an axial load is applied through an axial jack, loads of the upper portion and the lower portion of a model pile are collected through an upper pressure sensor and a lower tension sensor, pile body strain is collected through a pile body strain gauge, and a load displacement curve (Q-S curve) of a static load test of an uplift pile is obtained; the bearing capacity and the side friction resistance of the while-drilling pipe pile are obtained through calculation, the displacement of the uplift pile and the displacement of the soil layer can be obtained through the dial indicator and the laser displacement meter respectively, and therefore the contribution effects of different uplift measures on the uplift force are judged.

Description

Technical Field

[0001] This utility model relates to the field of pile foundation engineering technology, and specifically discloses a physical model test device for testing the pull-out performance of non-displacement precast pile foundations. Background Technology

[0002] As a key component in foundation engineering to resist uplift forces on structures, tension piles are widely used in fields such as anti-buoyancy in large basements, wind and earthquake resistance in tall buildings, wave load resistance in offshore platforms, and bridge anchorage systems. With the acceleration of urbanization and the expansion of engineering structures, large-diameter non-displacement precast piles are increasingly being used in tension foundations under complex geological conditions due to their high bearing capacity, minimal construction disturbance, and excellent environmental performance. However, the accurate testing and evaluation of their tension performance still faces many challenges, directly affecting the reliability and economy of engineering design.

[0003] Currently, most tests on the pull-out performance of pile foundations are conducted on-site prototype tests. For example, the Chinese patent "Synchronous Static Load Test System for Anchor Pile Reaction Force of Compressive and Pull-out Bearing Capacity" (Announcement No.: CN215630219U) tests the pull-out performance of piles by setting up a test device on the pile foundation at the construction site. Although on-site tests can reflect actual working conditions, they are costly, time-consuming, and limited by geological conditions, making it difficult to replicate and verify. Furthermore, research on the influence of different soil layers on pull-out forces in small-scale physical model experiments is still insufficient. Utility Model Content

[0004] This invention proposes a physical model test device for testing the pull-out performance of non-displacement precast pile foundations. This device is low in manufacturing cost, easy to use, simple and convenient to process, simple and safe in structure, easy to transport, and reusable. Another objective of this invention is to provide a method for testing the pull-out performance of large-diameter non-displacement precast piles. This method is highly feasible, with concise and clear design steps, safe and reliable execution, high control precision, and applicability to various application scenarios. This invention can simulate the influence of different grouting processes and parameters, as well as different construction techniques, on the pull-out performance of pull-out piles, including soil layers with different physical properties, groundwater flow velocity, the location, number, and diameter of grout outlets, static pressure grouting, and high-pressure jet grouting.

[0005] This utility model is implemented as follows: a physical model test device for testing the pull-out performance of non-displacement precast pile foundations includes a multi-functional cement grouting machine, a grout storage tank, a vacuum pump, a water storage tank, a vacuum pumping pipe, a model box bottom plate, model box side plates, and a high-strength tempered glass plate. The output end of the multi-functional cement grouting machine is connected to the outer surface of the grout storage tank. The outer surface of the water storage tank is connected to the input end of the vacuum pump through a pipe. The output end of the vacuum pump is connected to the vacuum pumping pipe. The outer surface of the grout storage tank is connected to the grouting pipe body. The outer surface of the grouting pipe body and the outer surface of the vacuum pumping pipe are respectively connected to a pressure regulating valve, a pressure gauge, and a control valve. The outer surface of the grouting pipe body is connected to a control switch. A cross support is provided above the model box bottom plate, and a pile top cover plate is provided below the cross support.

[0006] As a physical model test device for testing the pull-out performance of non-displacement precast pile foundations according to this utility model, a load-bearing steel plate is provided above the cross-shaped support. Multiple short screws are provided inside both the pile top cover plate and the load-bearing steel plate. Each short screw has a nut threaded onto its outer surface. A high-precision jack is connected to the upper surface of the cross-shaped support. A digital dial indicator is provided below the cross-shaped support. An upper pressure sensor is connected to the bottom surface of the load-bearing steel plate. A CMOS laser displacement meter is provided below the cross-shaped support. A medium-grade bedrock layer is provided on the upper surface of the model box bottom plate. An aquifer is provided above the medium-grade bedrock layer. A hard soil layer is set on top, and a soft soil layer is set above the hard soil layer. A semi-circular steel barrel is set on the back of the high-strength tempered glass plate. A small circular steel barrel is set on top of the semi-circular steel barrel. Two sets of soil pressure cells are set inside the semi-circular steel barrel, the aquifer, the hard soil layer and the soft soil layer. Two sets of pore water pressure sensors are set inside the aquifer. Two sets of pebbles are set inside the aquifer, the hard soil layer and the soft soil layer. A PVC sleeve is pre-embedded in the interior of the intermediate bedrock layer and the bottom surface of the model box bottom plate. A metal hook is set inside the PVC sleeve. Model piles are set in the interior of the aquifer, the hard soil layer and the soft soil layer.

[0007] As a physical model test device for testing the pull-out performance of non-displacement precast pile foundations according to this utility model, strain gauges are connected to the outer surface of the model pile, permeable stones are connected to the outer surface of the model pile, and concrete is connected to the bottom of the model pile. The outer surface of the model pile is provided with a bag body. A soil pressure cell is pre-embedded inside the soft soil layer and a pore water pressure sensor is pre-embedded inside the hard soil layer. Each bag body is provided with an inner grouting pipe, and the outer surface of the grouting pipe body is connected to the outer surface of the inner grouting pipe of the bag.

[0008] As a physical model test device for testing the pull-out performance of non-displacement precast pile foundations according to this utility model, the outer surface of the model pile is provided with pile side grouting, the bottom surface of the bottom plate of the model box is provided with a tensile sensor, one side of the side plate of the model box is connected to three water inlets, and one side of the side plate of the model box is connected to three water outlets.

[0009] As a physical model test device for testing the pull-out performance of non-displacement precast pile foundations according to this utility model, the inside of the pile top cover plate and the inside of the concrete bottom seal are both connected to long screws. The outer surface of the grouting pipe is connected to the upper grouting port, the outer surface of the grouting pipe is connected to the lower grouting port, and the outer surface of the grouting pipe is connected to the high-pressure jet grouting pipe.

[0010] As a physical model test device for testing the pull-out performance of non-displacement precast pile foundations according to this utility model, two small round holes are opened inside the concrete bottom and the interior of the intermediate bedrock layer, and a steel cage is installed inside each set of small round holes.

[0011] The beneficial effects of this utility model are:

[0012] 1. Axial load is applied by axial jacks, and the loads on the upper and lower parts of the model pile are collected by upper pressure sensors and lower tension sensors. The strain of the pile body is collected by pile strain gauges to obtain the load-displacement curve (QS curve) of the static load test of the pull-out pile. The bearing capacity and side friction of the drilled pipe pile are obtained by calculation. The displacement of the pull-out pile and the displacement of the soil layer can be obtained by dial gauge and laser displacement meter, respectively, so as to evaluate the contribution effect of different pull-out measures to the pull-out force.

[0013] 2. The device has low manufacturing cost, is easy to use, has simple and convenient processing technology, simple and safe structure, is easy to transport, and can be reused. Another objective of this invention is to provide a method for testing the pull-out performance of large-diameter non-displacement precast piles. This method has high feasibility, the design steps are concise and clear, the execution process is safe and reliable, the control precision is high, and it can be applied to various application scenarios. This invention can simulate the influence of different grouting processes and parameters, as well as different construction processes, on the pull-out performance of pull-out piles, such as soil layers with different physical properties, groundwater flow velocity, the location, number, and diameter of grout outlets, static pressure grouting, high-pressure jet grouting, etc. Attached Figure Description

[0014] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0015] Figure 1 This is a cross-sectional view of the physical model test device for testing the pull-out performance of a non-displacement precast pile foundation according to this utility model.

[0016] Figure 2 This is a cross-sectional view of the bottom plate of the model box in the physical model test device for testing the pull-out performance of a non-displacement precast pile foundation according to this utility model.

[0017] Figure 3 This is a cross-sectional view of the model pile in the physical model test device for testing the pull-out performance of a non-displacement precast pile foundation according to this utility model.

[0018] Figure 4 This is a front view of the semi-circular steel barrel in the physical model test device for testing the pull-out performance of a non-displacement precast pile foundation according to this utility model.

[0019] Figure 5 This is a frontal cross-sectional view of the differentiated bedrock layer in the physical model test device for testing the pull-out performance of a non-displacement precast pile foundation according to this utility model.

[0020] Figure 6 This is a frontal sectional view of the earth pressure cell in the physical model test device for testing the pull-out performance of a non-displacement precast pile foundation according to this utility model.

[0021] Figure 7 This is a frontal sectional view of the steel fiber reinforced concrete in the physical model test device for testing the pull-out performance of a non-displacement precast pile foundation according to this utility model.

[0022] Figure 8 This is a cross-sectional view of the hard soil layer in the physical model test device for testing the pull-out performance of a non-displacement precast pile foundation according to this utility model.

[0023] Figure 9 This is a schematic diagram of the soil structure after the steel bucket is pulled out of the physical model test device for testing the pull-out performance of a non-displacement precast pile foundation according to this utility model.

[0024] Figure 10 This is a schematic diagram of the cross-shaped support structure of the physical model test device for testing the pull-out performance of non-displacement precast pile foundations according to this utility model after installation.

[0025] Figure 11 A schematic diagram of the cover plate installed on the physical model test device for testing the pull-out performance of a non-displacement precast pile foundation according to this utility model.

[0026] Figure 12 This is a schematic diagram of the grouting system and vacuum drainage system of a physical model test device for testing the pull-out performance of a non-displacement precast pile foundation according to this utility model.

[0027] Figure 13This is a schematic diagram of the pile side grouting structure of a physical model test device for testing the pull-out performance of a non-displacement precast pile foundation according to this utility model.

[0028] Figure 14 This is a schematic diagram of the high-strength tempered glass plate structure for pile-side grouting in a physical model test device for testing the pull-out performance of a non-displacement precast pile foundation according to this utility model.

[0029] Figure 15 This is a cross-sectional view of a physical model test device for testing the pull-out performance of a non-displacement precast pile foundation according to this utility model.

[0030] Figure 16 This is a top view of the cover plate in the physical model test device for testing the pull-out performance of a non-displacement precast pile foundation according to this utility model.

[0031] The diagram shows the following components: 1. Multifunctional cement grouting machine; 2. Grout storage tank; 3. Pressure regulating valve; 4. Pressure gauge; 5. Control valve; 6. Vacuum pump; 7. Water storage tank; 8. Vacuum pumping pipe; 9. Grouting pipe body; 10. Control switch; 11. Nut; 12. Short screw; 13. Cross bracket; 14. CMOS laser displacement gauge; 15. Pile top cover plate; 16. Pebbles; 17. Grouting pipe inside the grouting bag; 18. Water inlet; 19. Upper grouting port; 20. Long screw; 21. Pore water pressure sensor; 22. Pile side grouting; 23. Strain gauge; 24. Permeable stone; 25. PVC sleeve; 6. Reinforcing cage; 27. Small round hole; 28. Model box bottom plate; 29. ​​Tension sensor; 30. Metal hook; 31. Model box side plate; 32. Medium-differentiated bedrock layer; 33. Lower grouting port; 34. Concrete bottom seal; 35. Aquifer; 36. High-pressure jet grouting pipe; 37. Hard soil layer; 38. Water outlet; 39. Earth pressure box; 40. Soft soil layer; 41. Bag body; 42. Model pile; 43. Digital dial indicator; 44. High-precision jack; 45. Load-bearing steel plate; 46. High-strength tempered glass plate; 47. Semi-circular steel barrel; 48. Upper pressure sensor; 49. Small round steel barrel. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments to aid in understanding its content. Unless otherwise specified, the methods used in this invention are conventional methods; the raw materials and apparatus used, unless otherwise specified, are conventional commercially available products.

[0033] Please see Figure 1-16A physical model test device for testing the pull-out performance of non-displacement precast pile foundations includes a multi-functional cement grouting machine 1, a grout storage tank 2, a vacuum pump 6, a water storage tank 7, a vacuum pumping pipe 8, a model box bottom plate 28, a model box side plate 31, and a high-strength tempered glass plate 46. The output end of the multi-functional cement grouting machine 1 is connected to the outer surface of the grout storage tank 2. The outer surface of the water storage tank 7 is connected to the input end of the vacuum pump 6 through a pipe. The output end of the vacuum pump 6 is connected to the vacuum pumping pipe 8. The outer surface of the grout storage tank 2 is connected to the grouting pipe body 9. The outer surface of the grouting pipe body 9 and the outer surface of the vacuum pumping pipe 8 are respectively connected to a pressure regulating valve 3, a pressure gauge 4, and a control valve 5. The outer surface of the grouting pipe body 9 is connected to a control switch 10. A cross bracket 13 is provided above the model box bottom plate 28, and a pile top cover plate 15 is provided below the cross bracket 13.

[0034] As a technical optimization of this utility model, a load-bearing steel plate 45 is provided above the cross bracket 13. Multiple short screws 12 are provided inside the pile top cover plate 15 and the load-bearing steel plate 45. Each short screw 12 has a nut 11 threaded onto its outer surface. A high-precision jack 44 is connected to the upper surface of the cross bracket 13. A digital dial indicator 43 is provided below the cross bracket 13. An upper pressure sensor 48 is connected to the bottom surface of the load-bearing steel plate 45. A CMOS laser displacement meter 14 is provided below the cross bracket 13. A medium-grade bedrock layer 32 is provided on the upper surface of the model box bottom plate 28. An aquifer 35 is provided above the medium-grade bedrock layer 32. A hard soil layer 37 is provided above the aquifer 35. A soft soil layer 40 is provided above the hard soil layer 37. A high-strength tempered glass plate 46 is provided on the back. There is a semi-circular steel barrel 47, and a small circular steel barrel 49 is set on top of the semi-circular steel barrel 47. Inside the semi-circular steel barrel 47, there are two sets of soil pressure boxes 39 in the aquifer 35, hard soil layer 37 and soft soil layer 40. Inside the aquifer 35, there are two sets of pore water pressure sensors 21. Inside the aquifer 35, hard soil layer 37 and soft soil layer 40, there are two sets of pebbles 16. The interior of the intermediate bedrock layer 32 and the bottom surface of the model box bottom plate 28 are pre-embedded with PVC sleeves 25. The interior of the PVC sleeves 25 is equipped with metal hooks 30. The interior of the aquifer 35, hard soil layer 37 and soft soil layer 40 are jointly equipped with model piles 42. Every two pore water pressure sensors 21 are located on both sides of the model pile 42 and are symmetrical. Every two soil pressure boxes 39 are located on both sides of the model pile 42 and are symmetrical.

[0035] In this embodiment: The first soil layer simulates a moderately weathered bedrock layer, which is made from barite powder, sand, gypsum, and water in a certain proportion. A sealed circular steel barrel with a diameter of 20cm is placed in a model box, and the prepared mud slurry is poured into the model box until the thickness reaches 20cm. After initial setting, the circular steel barrel is removed and left to stand for more than seven days. Then, a hollow circular steel barrel with a diameter of 20cm is placed in again, and the second soil layer (including water layer 35) is filled in. When the thickness of the second soil layer reaches 10cm, two soil pressure cells 39 and pore water pressure gauges are symmetrically arranged 25cm away from the left and right sides of the model box to facilitate the later measurement of the upper soil pressure. Filling continues until the thickness of the second soil layer reaches 20cm. The third soil layer (hard soil layer 37) and the fourth soil layer (soft soil layer 40) are inserted. The thickness of the third and fourth soil layers is 20 cm. The sensor placement is the same as that in the second soil layer, and the sensors are placed 10 cm away from the previous soil layer. The model box is composed of three 3 cm thick steel plates and one high-strength tempered glass plate 46. Six water outlets 38 and drains with a diameter of 3 cm are symmetrically arranged on each steel plate. A layer of pebbles with a thickness of 3-5 cm and a diameter of 1-2 cm is laid along the steel plates to evenly distribute the water pressure at the inlet and outlet 38. The water pressure at the inlet is adjusted to simulate the water flow velocity in the real strata. The high-strength tempered glass plate 46 is placed on the long side of the model box.

[0036] As a technical optimization of this utility model, strain gauges 23 are connected to the outer surface of the model pile 42, permeable stones 24 are connected to the outer surface of the model pile 42, concrete sealing 34 is connected to the inside of the model pile 42, a bladder body 41 is provided on the outer surface of the model pile 42, a soil pressure cell 39 is pre-embedded inside the soft soil layer 40, a pore water pressure sensor 21 is pre-embedded inside the hard soil layer 37, a grouting pipe 17 is provided inside each bladder body 41, the outer surface of the grouting pipe body 9 is connected to the outer surface of the grouting pipe 17, a pile side grouting 22 is provided on the outer surface of the model pile 42, a tension sensor 29 is provided on the bottom surface of the model box bottom plate 28, three water inlets 18 are connected to one side of the model box side plate 31, and three water outlets 38 are connected to one side of the model box side plate 31.

[0037] In this embodiment: the inlet 18 is connected to an external water source. After the water flow velocity at the outlet 38 reaches a stable level, the next step can be carried out. This model box is a multi-functional model box with multiple outlets 38 and inlets. Different outlets / inlets can be selected according to experimental requirements. This experiment is a semi-model experiment. The experimental process can be recorded by a camera. The recorded images are processed by PIVview2C software. The resulting particle images can clearly track the movement trajectory of granular media such as sand and gravel.

[0038] As a technical optimization of this utility model, the interior of the pile top cover plate 15 and the interior of the concrete bottom seal 34 are both connected to long screws 20, the outer surface of the grouting pipe body 9 is connected to the upper grouting port 19, the outer surface of the grouting pipe body 9 is connected to the lower grouting port 33, and the outer surface of the grouting pipe body 9 is connected to the high-pressure jet grouting pipe 36.

[0039] In this embodiment: the multi-functional cement grouting machine 1 is started, and conventional grouting is carried out through the upper grouting port 19 and the lower grouting port 33 to fill the gap between the pile and the soil. High-pressure grouting is carried out through the high-pressure jet grouting pipe 36 to spray the slurry into the hard soil layer 37. Grouting is carried out through the grouting pipe 17 inside the bag to make the bag expand and bulge into the soil layer. When the grouting is finished, the remaining slurry in the slurry storage tank 2 is used to prepare 70*70*70 concrete test blocks for later use.

[0040] As a technical optimization of this utility model, two small round holes 27 are opened inside the concrete sealing bottom 34 and the interior of the intermediate bedrock layer 32, and a steel cage 26 is provided inside each set of small round holes 27.

[0041] In this embodiment: a metal hook 30 is used to mount a tension gauge.

[0042] The working principle and usage process of this utility model are as follows: The model box has a length, width, and height of 1m, 0.5m, and 1.2m, respectively. The bottom plate 28 of the model box is made of a 3cm thick steel plate. Two 2cm diameter circular holes are drilled in the center of the bottom plate 28. The model box is composed of three 3cm thick side plates 31 around its perimeter. Each side plate 31 has six symmetrically arranged 3cm diameter water inlets 18 / drain outlets. The front of the model box is a 3cm thick high-strength tempered glass plate 46. A layer of 3-5cm thick and 1-2cm diameter pebbles 1 is laid along the side plates 31 around the model box. 6. Set aside the cross bracket 13 on top of the model box for later use. Select a polyvinyl chloride pipe (PVC pipe) with an outer diameter of 18cm, an inner diameter of 16cm, and a length of 0.75m as the model pile 42. Drill 1.5cm diameter holes at 7cm and 50cm from the bottom to simulate the upper grouting port 19 for simultaneous grouting at the bottom and top. At the same time, drill two 1.5cm diameter holes at 56cm from the bottom and place a sluice bag to simulate the grouting pipe 17 inside the sluice bag. Drill a hole 15cm from the bottom and place a permeable stone 24. Place the permeable stone 24 at 10cm from the bottom of the model pile 42. Strain gauges 23 (type 120-1AA) were initially attached every 15 cm and sealed with AB glue. Two metal hooks 30 were symmetrically embedded at the bottom of the model pile 42. The prepared model pile 42 was set aside for later use. Semi-circular steel buckets 47 and small circular steel buckets 49 were inserted. The first soil layer simulated the moderately weathered bedrock layer 32. The moderately weathered bedrock was made by mixing barite powder, sand, gypsum, and water in a certain proportion. The prepared mud was poured into the model box until the thickness reached 20 cm. After initial setting, the semi-circular steel buckets 47 and small circular steel buckets 49 were removed and left to stand for more than seven days. Then, the semi-circular steel bucket 47 is inserted again, and the second layer of soil (including the water layer) 35 is filled in. When the thickness of the second layer of soil reaches 10 cm, two soil pressure boxes 39 and pore water pressure sensors 21 are symmetrically arranged 25 cm away from the side of the model line. Soil filling continues. After the thickness of the second layer of soil reaches 20 cm, the third layer of soil (hard soil layer 37 and soft soil layer 40) is filled in. The thickness of the third and fourth layers of soil is 20 cm. The sensor arrangement is the same as the sensor placement in the second layer of soil, and they are all placed 10 cm away from the previous layer of soil. The model pile 42 is then placed in.Pull out the semi-circular steel bucket 47, which creates a 20cm diameter hole in the soil. The hole's diameter is larger than the 18cm diameter of the model pile 42. Place a small steel cage 26 into the small hole 27, then place the model pile 42 into the hole. The distance between the model pile 42 and the surrounding soil is 1cm. Install the cross bracket 13, and inject cement grout into the bottom of the model pile 42, filling it to 12-15cm from the bottom. Insert five 70cm long screw rods 20 into the cement grout (8cm deep). After the cement grout solidifies, install a pile top cover plate 15 on top of the model pile 42, along with the long screw rods. 20 is connected by nuts 11. The pile top cover plate 15 is sealed with cement grout in the rock-embedded layer at the bottom of the pile to seal the inner cavity of the pipe pile. The pile top cover plate 15 is connected to the load-bearing steel plate 45 above the jack by four short screws 12. The grouting system and vacuum drainage system are connected. The grouting pipes are connected to the grouting machine. Taking the grouting pipe body 9 as an example, the following is an explanation: The grouting pipe body 9 is connected in sequence to the control valve 5, pressure gauge 4, pressure regulating valve 3, grout storage tank 2 and multi-functional cement grouting machine 1. The other three grouting pipes are connected in the same way. The vacuum pumping pipe is connected in sequence to the control valve 5, pressure gauge 4, pressure regulating valve 3 and vacuum pump 6. With vacuum pumping pipe 8, start multi-functional cement grouting machine 1, and perform conventional grouting through upper grouting port 19 and lower grouting port 33 to fill the gap between pile and soil; perform high-pressure grouting through high-pressure jet grouting pipe 36 to inject mud into hard soil layer 37, and perform bag grouting through bag grouting pipe 17 to make the bag expand and squeeze into the soil layer. After grouting, the grout body and the above-mentioned 70*70*70 concrete test block are naturally cured for 28 days. Then, the concrete test block strength test is carried out. After reaching the specified strength, the next test is carried out. Otherwise, the curing continues. Two digital display dial gauges 43 are placed on pile top cover plate 15, and soil is backfilled on both sides of the pile. Four CMOS laser displacement gauges 14 are symmetrically arranged above, and tension sensors 29 are arranged on the metal hooks 30 at the bottom of the pile. A high-precision jack 44 is placed, with an upper pressure sensor 48 arranged above the jack. After the grouting body reaches a certain strength, a static load test of the pull-out pile is carried out. Axial load is applied by the axial high-precision jack 44, and the loads on the upper and lower parts of the model pile 42 are collected by the upper pressure sensor 48 and the lower tension sensor 29. The strain of the pile body is collected by the pile strain gauge 23 to obtain the load-displacement curve (QS curve) of the static load test of the pull-out pile. The bearing capacity and side friction of the drilled casing pile are obtained by calculation.

[0043] In the description of this utility model, it should be understood that the terms "left", "right", "up", "down", "top", "bottom", "front", "back", "inner", "outer", "back", "middle", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0044] However, the above description is only a specific embodiment of this utility model and should not be construed as limiting the scope of implementation of this utility model. Therefore, any substitution of equivalent components or equivalent changes and modifications made in accordance with the scope of protection of this utility model should still fall within the scope of the claims of this utility model.

Claims

1. A physical model test device for testing the pull-out performance of non-displacement precast pile foundations, characterized in that: The system includes a multi-functional cement grouting machine (1), a grout storage tank (2), a vacuum pump (6), a water storage tank (7), a vacuum pumping pipe (8), a model box bottom plate (28), a model box side plate (31), and a high-strength tempered glass plate (46). The output end of the multi-functional cement grouting machine (1) is connected to the outer surface of the grout storage tank (2). The outer surface of the water storage tank (7) is connected to the input end of the vacuum pump (6) through a pipe. The output end of the vacuum pump (6) is connected to the vacuum pumping pipe (8). The outer surface of the grout storage tank (2) is connected to the grouting pipe body (9). The outer surface of the grouting pipe body (9) and the outer surface of the vacuum pumping pipe (8) are respectively connected to a pressure regulating valve (3), a pressure gauge (4), and a control valve (5). The outer surface of the grouting pipe body (9) is connected to a control switch (10). A cross bracket (13) is provided above the model box bottom plate (28), and a pile top cover plate (15) is provided below the cross bracket (13).

2. The physical model test device for testing the pull-out performance of non-displacement precast pile foundations according to claim 1, characterized in that: A load-bearing steel plate (45) is provided above the cross bracket (13). Multiple short screws (12) are provided inside the pile top cover plate (15) and the load-bearing steel plate (45). A nut (11) is threaded onto the outer surface of each short screw (12). A high-precision jack (44) is connected to the upper surface of the cross bracket (13). A digital dial indicator (43) is provided below the cross bracket (13). An upper pressure sensor (48) is connected to the bottom surface of the load-bearing steel plate (45). A CMOS laser displacement meter (14) is provided below the cross bracket (13). A medium-differentiated bedrock layer (32) is provided on the upper surface of the model box bottom plate (28). An aquifer (35) is provided above the medium-differentiated bedrock layer (32). A hard soil layer (37) is provided above the aquifer (35). A soft soil layer is provided above the hard soil layer (37). (40) A semi-circular steel barrel (47) is provided on the back of the high-strength tempered glass plate (46). A small circular steel barrel (49) is provided above the semi-circular steel barrel (47). Two sets of soil pressure boxes (39) are provided inside the semi-circular steel barrel (47), the aquifer (35), the hard soil layer (37) and the soft soil layer (40). Two sets of pore water pressure sensors (21) are provided inside the aquifer (35). Two sets of pebbles (16) are provided inside the aquifer (35), the hard soil layer (37) and the soft soil layer (40). A PVC sleeve (25) is pre-embedded in the interior of the intermediate bedrock layer (32) and the bottom surface of the model box bottom plate (28). A metal hook (30) is provided inside the PVC sleeve (25). A model pile (42) is provided in the interior of the aquifer (35), the hard soil layer (37) and the soft soil layer (40).

3. The physical model test device for testing the pull-out performance of non-displacement precast pile foundations according to claim 2, characterized in that: The outer surface of the model pile (42) is connected to a strain gauge (23), the outer surface of the model pile (42) is connected to a permeable stone (24), the inner surface of the model pile (42) is connected to a concrete bottom seal (34), the outer surface of the model pile (42) is provided with a bag body (41), the soft soil layer (40) is pre-embedded with a soil pressure cell (39), the hard soil layer (37) is pre-embedded with a pore water pressure sensor (21), each bag body (41) is provided with a grouting pipe (17) inside the bag, and the outer surface of the grouting pipe body (9) is connected to the outer surface of the grouting pipe (17) inside the bag.

4. The physical model test device for testing the pull-out performance of non-displacement precast pile foundations according to claim 2, characterized in that: The outer surface of the model pile (42) is provided with pile side grouting (22), the bottom surface of the model box bottom plate (28) is provided with tension sensor (29), one side of the model box side plate (31) is connected to three water inlets (18), and one side of the model box side plate (31) is connected to three water outlets (38).

5. The physical model test device for testing the pull-out performance of non-displacement precast pile foundations according to claim 1, characterized in that: The inside of the pile top cover plate (15) and the inside of the concrete bottom seal (34) are both connected to long screws (20). The outer surface of the grouting pipe body (9) is connected to the upper grouting port (19), the outer surface of the grouting pipe body (9) is connected to the lower grouting port (33), and the outer surface of the grouting pipe body (9) is connected to the high-pressure jet grouting pipe (36).

6. The physical model test device for testing the pull-out performance of non-displacement precast pile foundations according to claim 5, characterized in that: Two small round holes (27) are opened inside the concrete bottom seal (34) and the intermediate bedrock layer (32), and a steel cage (26) is provided inside each set of small round holes (27).

Images