CN115030237A - Double-casing pile negative friction testing device and testing method under silt geology - Google Patents
Double-casing pile negative friction testing device and testing method under silt geology Download PDFInfo
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- CN115030237A CN115030237A CN202210655635.XA CN202210655635A CN115030237A CN 115030237 A CN115030237 A CN 115030237A CN 202210655635 A CN202210655635 A CN 202210655635A CN 115030237 A CN115030237 A CN 115030237A
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- 238000012360 testing method Methods 0.000 title claims abstract description 31
- 239000002689 soil Substances 0.000 claims abstract description 36
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 30
- 239000011148 porous material Substances 0.000 claims abstract description 29
- 238000006243 chemical reaction Methods 0.000 claims abstract description 19
- 238000007789 sealing Methods 0.000 claims abstract description 6
- 230000001681 protective effect Effects 0.000 claims description 9
- 238000000034 method Methods 0.000 claims description 8
- 239000000945 filler Substances 0.000 claims description 3
- 239000010802 sludge Substances 0.000 claims 3
- 239000004576 sand Substances 0.000 abstract description 8
- 230000000694 effects Effects 0.000 abstract description 3
- 230000009467 reduction Effects 0.000 abstract description 3
- 238000012544 monitoring process Methods 0.000 description 8
- 239000010410 layer Substances 0.000 description 4
- 238000011160 research Methods 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 3
- 238000006073 displacement reaction Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 235000017166 Bambusa arundinacea Nutrition 0.000 description 1
- 235000017491 Bambusa tulda Nutrition 0.000 description 1
- 241001330002 Bambuseae Species 0.000 description 1
- 235000015334 Phyllostachys viridis Nutrition 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000011425 bamboo Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000004062 sedimentation Methods 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D33/00—Testing foundations or foundation structures
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- Investigation Of Foundation Soil And Reinforcement Of Foundation Soil By Compacting Or Drainage (AREA)
- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
Abstract
The invention discloses a double-casing pile negative friction resistance testing device and a testing method under silt geology, which comprises a reaction frame, a first jack, a supporting frame, a dial indicator, a model box, a pore water pressure gauge, a model pile, an outer casing, a strain gauge, fine sand, a pressure box, a cavity, a second jack, a strain acquisition instrument, a pore water pressure acquisition instrument, a loading plate, a soil body, an extension column, a bearing plate, a pile hole, a lead hole, a retaining ring, a sealing ring, an air pump and an air pipe, wherein the reaction frame is arranged on the reaction frame; soil is filled in the model box, the model pile and the model pile casing are embedded in the soil of the model box, and strain gauges are attached to the inner walls of the model pile and the model pile casing and connected with a strain acquisition instrument; and filling fine sand in a cavity between the model pile and the model pile casing, and pressurizing and compacting by adopting an air pump. The test measuring device simulates the reduction of the negative frictional resistance of the pile side, and obtains the reduction effect of the pile side negative frictional resistance by the pile foundation axial force, the negative frictional resistance and the soil body pore water pressure and settlement.
Description
Technical Field
The invention relates to the field of geological testing, in particular to a negative friction testing device and a testing method for a double pile casing under silt geology.
Background
At present, pile foundations are mainly adopted for coastal engineering foundations at home and abroad, but in some areas, deep silt and mucky soil layers are distributed on the surface layer, so that pile foundation engineering construction is carried out on the silt foundation, the negative frictional resistance of the pile side needs to be reduced, and the safety of an upper structure is ensured. In the current model test research, the measurement of the negative friction resistance at the pile side and the calculation of the control point of the pile body are mainly aimed at, and the model test research for reducing the negative friction resistance at the pile side is less. Therefore, the double-pile-casing pile negative friction resistance testing device and the testing method under the silt geology are designed, and the reduction effect of the pile-casing structure on the pile-side negative friction resistance is obtained by measuring the pile foundation axial force, the pile-side negative friction resistance and the pore water pressure and displacement settlement of soil bodies around the pile at different depths.
Disclosure of Invention
The invention aims to solve the problems and designs a double-casing pile negative friction resistance testing device and a testing method under silt geology.
The technical scheme of the invention is that the device comprises a model box 5, soil 18 is filled in the model box, a load bearing plate 17 is arranged on the upper surface of the soil, a support frame 3 is arranged on the load bearing plate 17, a model pile 7 and a model outer protective cylinder 8 penetrate through the load bearing plate and enter the soil in the model box, sandy soil filling is carried out on a hole between the model pile 7 and the model outer protective cylinder 8, the pile top of the model pile 7 is exposed out of the soil 18, a dial indicator 4 is arranged on the pile top of the model pile 7, a plurality of strain gauges are attached and coated on the inner wall of a part of a pile body of the model pile 7 embedded in the soil, a plurality of strain gauges 9 are attached and coated on the inner wall of the model protective cylinder, the strain gauges 9 are connected with a strain acquisition instrument 15 outside the model box through leads, the model pile 7 is annularly provided with a settlement mark 27 and a pore water pressure gauge 6, the settlement mark 27 is connected with the dial indicator 4, and the pore water pressure gauge 6 is connected with a pore water pressure acquisition instrument 16 outside the model box through a lead.
The loading system comprises a first jack 2, a second jack 14, a reaction frame 1 and a support frame 3, wherein the reaction frame 1 is located on the outer side of the model box 5, a pile hole 21 and a lead hole 22 are formed in the middle of the support frame 3, the first jack 2 is located on the support frame 3, the second jack 14 is located on a pile bearing plate 20 of the model pile 7, and the second jack 14 and the reaction frame 1 are subjected to load transmission through an extension column 19.
The geometric center of the load bearing plate 17 is provided with a pile hole 21, the model pile 7 is inserted into the soil body 18 through the pile hole, a plurality of lead holes 22 are uniformly distributed around the pile hole 21, and the surface of the load bearing plate 17 is provided with a plurality of ring buckles 23. The settlement marks 27 and the pore water pressure gauge 6 are uniformly arranged around the model pile 7 in an annular mode and are embedded into the soil body 18 in the model box 5 at different depths.
Compared with the existing laboratory, the double-casing pile negative friction resistance testing device and the testing method manufactured by the technical scheme of the invention have the following beneficial effects:
1. compared with the existing model and method, the device for testing the negative friction resistance of the double-casing pile under the silt geology can effectively research the negative friction resistance characteristic of the double-casing pile foundation in the silt soil in the coastal region, and research the effectiveness of the outer casing structure on pile foundation protection.
2. In the soil body in the model case, different soil layer depths lay monitoring instruments such as subside mark and pore water pressure gauge, and the pressure cell is laid to model stake tip for obtain a large amount of monitoring data can judge the model and protect the atress characteristic of a section of thick bamboo and subduct the effect of burden frictional resistance.
3. And filling fine sand between the model pile and the model pile casing, tamping the fine sand by adopting an air pressure method, and monitoring the mechanical characteristics generated by the relative friction between the model pile and the model pile casing under the action of the soil body through the internal strain gauge.
4. Respectively arranging a dial indicator and a pressure box on the pile top and the pile end of the model pile, and monitoring the settlement displacement of the pile top and the pressure change of the pile end;
5. a through hole is arranged in the geometric center of the support frame, a second jack penetrates through the through hole, the second jack is connected with the counterforce device through an extension column, and a jack is arranged at the top of the model pile to apply vertical load.
6. And fine sand in a cavity between the model pile and the model casing is compacted through air pressure by an air pump, so that the test process is close to the actual engineering application process.
Drawings
FIG. 1 is a front cross-sectional view of the device of the present invention.
Figure 2 is a side cross-sectional view of the inventive device.
Figure 3 is a plan view of a load plate in the apparatus of the present invention.
FIG. 4 is a schematic view of the structure of the supporting frame of the device of the present invention.
In the figure, 1, a reaction frame; 2. a first jack; 3. a support frame; 4. a dial indicator; 5. a model box; 6. a pore water pressure gauge; 7. a model pile; 8. an outer protective cylinder; 9. a strain gauge; 10. a force acquisition instrument; 11. a filler material; 12. a pressure cell; 13. a cavity; 14. a second jack; 15. A strain acquisition instrument; 16. a pore water pressure acquisition instrument; 17. a loading plate; 18. a soil body; 19. Extending the column; 20. a bearing plate; 21. pile holes; 22. a wire hole; 23. a retaining ring; 24. a seal ring; 25. an air pump; 26. an air tube; 27. and (5) settling.
Detailed Description
The invention is described in detail below with reference to the accompanying drawings, and as shown in fig. 1-4, provides a negative friction resistance testing device and a testing method for a double casing pile under a silt geology.
As shown in the figure, the device provided by the invention is a double-pile casing negative friction resistance testing device and a testing method under silt geology, and comprises a reaction frame 1, a first jack 2, a support frame 3, a dial indicator 4, a model box 5, a pore water pressure gauge 6, a model pile 7, an outer casing 8, a strain gauge 9, a pressure acquisition instrument 10, a filling material 11, a pressure box 12, a cavity 13, a second jack 14, a strain acquisition instrument 15, a pore water pressure acquisition instrument 16, a loading plate 17, a soil body 18, an extension column 19, a bearing plate 20, a pile hole 21, a lead hole 22, a retaining ring 23, a sealing ring 24, an air pump 25, an air pipe 26 and a settlement mark 27. The reaction frame 1, the pressure acquisition instrument 10, the strain acquisition instrument 15 and the pore water pressure acquisition instrument 16 are positioned on the outer side of the box body. The mucky soil body 18 with high water content is contained in the model box 5. A bearing plate 20 is arranged between the model pile 7 and the second jack 14, and the second jack 14 and the reaction frame 7 are connected through an extension column 19. And (4) arranging a dial indicator 4 on the pile top of the model pile 7, and monitoring the sinking displacement of the pile top. Filling 11 with filler 11 in a cavity 13 between the model pile 7 and the model outer casing 8, attaching a plurality of strain gauges 9 on the inner sides of the model pile 7 and the model outer casing 8, wherein the strain gauges 9 attached between the model pile 7 and the model outer casing 8 correspond to each other, and a pressure box 12 is arranged at the pile end of the model pile 7. The strain gauge 9 and the pressure box 10 are connected with the strain acquisition instrument 10 through a lead, the strain gauge 9 is used for monitoring the stress-strain condition of the pile body, and the pressure box 12 is used for monitoring the pressure of the pile end.
A plurality of pore water pressure gauges 6 and a plurality of settlement marks 27 are annularly arranged in the soil body 18 around the model piles 7. The pore water pressure gauge 6 is connected with a pore water pressure gauge acquisition instrument 16 outside the model box, and reads pore water pressure data of different soil layers through computer software. And the pore water pressure gauges 6 are arranged according to different depths and are used for monitoring the pore water pressure distribution conditions of different depths around the pile. The settlement mark 27 is connected with the dial indicator 4 outside the model box 5 and is monitored by computer software. The settlement marks 27 are arranged in soil layers with different depths around the model pile, are connected with the settlement marks 27 through the dial indicator 4, and read the data of soil settlement through computer software.
And a loading system is arranged on the load bearing plate 17 and is used for applying load to the soil body 18 and the pile top in the mould box 5. The reaction frame 1 is displaced outside the model box 5, the first jack 2 and the load bearing plate 17 are subjected to load transmission through the support frame 3, the second jack 14 is positioned on a bearing platform plate 20 at the upper part of the pile top of the model pile 7, and the second jack 14 is connected with the reaction frame 1 through the extension column 19. The loading system can control the load application to the soil around the pile and the pile top, and the reaction frame 1 preferentially uses a double-beam structure to avoid the deformation of the structure caused by the reaction force.
The model pile 7 and the model outer protective cylinder 8 both adopt hollow pipes, and the strain gauges 9 are attached to the inner sides of the model pile 7 and the model outer protective cylinder 8. And a cavity 13 between the model pile 7 and the model outer casing 8 is filled with fine sand 11, and the coincidence of the geometric centers of the model pile 7 and the model outer casing 8 is ensured when the fine sand is buried, so that the data acquired by the strain gauge 9 is more accurate.
The load plate 17 is positioned on the upper surface of the soil body 18, a pile hole 21 is arranged at the geometric center of the load plate 17, and a plurality of lead holes 22 are arranged by taking the pile hole 21 as the center, so that a plurality of pore water pressure meters 6 and a plurality of sedimentation marks 27 lead wires pass through the through holes to be connected with a pore water pressure acquisition instrument 16 and a strain edge acquisition instrument 15 outside the model box 5. The two sides of the load bearing plate 17 are provided with retaining rings 23, so that the load bearing plate can move and lift conveniently.
The support frame 3 is positioned on the upper part of the load bearing plate 17, and in order to ensure that the soil around the pile, the model pile 7 and the model outer protective barrel 8 are stressed uniformly, the geometric center of the support frame 3 is superposed with the geometric center of the load bearing plate 17, and the soil body is prevented from being stressed unevenly. The geometric center of the upper part of the support frame 3 is provided with a hole, so that the second jack 14 passes through the support frame 3 and is in load transmission with the reaction frame 1 through the extension column 19.
The air pump 25 is located on the outer side of the model box 5, the air pipe 26 penetrates through the sealing ring 24 and the cavity 13 between the model pile 7 and the model outer casing 8 to be communicated, fine sand 11 filled in the cavity 13 is filled for multiple times, damage to the strain gauge after pressurization and compaction after excessive filling is avoided, and the sealing ring 24 is removed after filling.
The technical solutions described above only represent the preferred technical solutions of the present invention, and some possible modifications to some parts of the technical solutions by those skilled in the art all represent the principles of the present invention, and fall within the protection scope of the present invention.
Claims (6)
1. A double-pile casing negative friction testing device under silt geology is characterized in that the testing device comprises a reaction frame 1, a first jack 2, a lower load plate 17, a model box 5 filled with soil 18, a second jack 14, a model pile 7, a bearing plate 20, a dial indicator 4, a settlement mark 27, a strain gauge 9, a strain acquisition instrument 15, a pore water pressure acquisition instrument 16, a sealing ring 24, an air pump 25, an air pipe 26 and a pressure acquisition instrument 10;
the reaction frame 1, the strain acquisition instrument 15, the pore water pressure acquisition instrument 16 and the air pump 25 are positioned outside the model box 5; the loading plate 17 is positioned on the upper surface of the soil body 18 in the model box 5, the loading plate 17 is provided with a model pile hole 21 and a lead hole 22, the model pile 7 and the model outer protective cylinder 8 are inserted into the soil body 18 in the model box through the pile hole 21, and the pile top of the model pile 7 is exposed above the loading plate 17; the model pile 7 and the part of the model outer protective cylinder 8 which is arranged in the soil body are adhered with a plurality of strain gauges 9, the strain gauges 9 are connected with a strain acquisition instrument 15 through leads, the bottom of the pile end is provided with a pressure box 12, and the pile top is provided with a dial indicator 4; a plurality of settlement marks 27 and a plurality of pore water pressure gauges 6 are arranged in the soil body 18, the settlement marks 27 are connected with the dial indicator 4, and the pore water pressure gauges 6 are connected with the pore water pressure acquisition instrument 16.
2. The device and the method for testing the negative friction resistance of the double casing pile under the silt geology according to claim 1 are characterized in that: the loading device comprises a reaction frame 1, a first jack 2, a second jack 14, a support frame 3 and an extension column 19, wherein the reaction frame 1 is positioned on the outer side of the model box 5, the first jack 2 is positioned on the support frame 3, the support frame 3 is positioned on the load bearing plate 17, the second jack 14 is positioned on the bearing plate 20, and the extension column 19 is positioned on the second jack 14.
3. The device and the method for testing negative friction resistance of the double casing piles under the sludge geology according to claim 1 are characterized in that: the model pile comprises a model pile 7 and a hollow pipe of a model outer casing 8, a strain gauge 9 is attached to the inner wall surfaces of the model pile 7 and the model outer casing 8, and a cavity 13 between the model outer casing 8 and the model pile 7 is filled with filler.
4. The device and the method for testing the negative friction resistance of the double pile casing under the sludge geology according to claim 2 are characterized in that a pile hole 21 is formed in the geometric center of the load bearing plate 17, and a plurality of lead holes 22 are arranged on the load bearing plate 17 by taking the pile hole 21 as the center.
5. The device and the method for testing negative friction resistance of the double casing piles under the sludge geology according to claim 1 are characterized in that: the settlement marks 27 and the pore water pressure meters 16 are arranged in the soil body 18 in the model box 5 at different depths, and the settlement marks 27 and the pore water pressure meters 16 are arranged in a ring shape by taking the model pile 7 as the center.
6. The negative friction resistance testing device for the double casing piles under the silt geology according to any one of claims 1 to 5, which is characterized in that: the air pipe 26 passes through the sealing ring 24 to be in contact with the cavity 13 between the model pile 7 and the model outer casing 8, and the air pump 25 is connected with the air pipe 26.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210655635.XA CN115030237A (en) | 2022-06-10 | 2022-06-10 | Double-casing pile negative friction testing device and testing method under silt geology |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202210655635.XA CN115030237A (en) | 2022-06-10 | 2022-06-10 | Double-casing pile negative friction testing device and testing method under silt geology |
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| CN115030237A true CN115030237A (en) | 2022-09-09 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115977173A (en) * | 2022-12-28 | 2023-04-18 | 青岛理工大学 | Repeatable testing device and testing method for static pile pressing in homogeneous soil |
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2022
- 2022-06-10 CN CN202210655635.XA patent/CN115030237A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115977173A (en) * | 2022-12-28 | 2023-04-18 | 青岛理工大学 | Repeatable testing device and testing method for static pile pressing in homogeneous soil |
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