CN110878566B - Model test device for plastic drainage board foundation under vacuum-stacking combined pre-pressing - Google Patents
Model test device for plastic drainage board foundation under vacuum-stacking combined pre-pressing Download PDFInfo
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- CN110878566B CN110878566B CN201911253588.0A CN201911253588A CN110878566B CN 110878566 B CN110878566 B CN 110878566B CN 201911253588 A CN201911253588 A CN 201911253588A CN 110878566 B CN110878566 B CN 110878566B
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- 238000012360 testing method Methods 0.000 title claims abstract description 56
- 239000004033 plastic Substances 0.000 title claims description 16
- 238000003825 pressing Methods 0.000 title description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 51
- 239000002689 soil Substances 0.000 claims abstract description 45
- 239000011148 porous material Substances 0.000 claims abstract description 37
- 239000011521 glass Substances 0.000 claims abstract description 28
- 238000011068 loading method Methods 0.000 claims abstract description 28
- 238000004062 sedimentation Methods 0.000 claims abstract description 25
- 238000006073 displacement reaction Methods 0.000 claims abstract description 21
- 239000002390 adhesive tape Substances 0.000 claims abstract description 19
- 238000005259 measurement Methods 0.000 claims abstract description 15
- 229910000831 Steel Inorganic materials 0.000 claims description 43
- 239000010959 steel Substances 0.000 claims description 43
- 230000008859 change Effects 0.000 claims description 12
- 239000004746 geotextile Substances 0.000 claims description 8
- 238000007789 sealing Methods 0.000 claims description 8
- 239000000565 sealant Substances 0.000 claims description 4
- 239000002002 slurry Substances 0.000 claims description 3
- 238000000034 method Methods 0.000 abstract description 18
- 230000006835 compression Effects 0.000 abstract description 5
- 238000007906 compression Methods 0.000 abstract description 5
- 238000005056 compaction Methods 0.000 abstract description 4
- 238000004519 manufacturing process Methods 0.000 abstract description 2
- 238000010276 construction Methods 0.000 description 6
- 239000000314 lubricant Substances 0.000 description 5
- 229940099259 vaseline Drugs 0.000 description 5
- 238000011049 filling Methods 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 238000005303 weighing Methods 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 238000009530 blood pressure measurement Methods 0.000 description 2
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- 239000007769 metal material Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000036316 preload Effects 0.000 description 2
- 238000000967 suction filtration Methods 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000004927 clay Substances 0.000 description 1
- 238000007596 consolidation process Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
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- 239000004744 fabric Substances 0.000 description 1
- 239000010881 fly ash Substances 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
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Classifications
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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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- Engineering & Computer Science (AREA)
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- Mining & Mineral Resources (AREA)
- Paleontology (AREA)
- Civil Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Structural Engineering (AREA)
- 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 model test device for a vacuum-preloading combined pre-compaction soft soil foundation, which comprises a model box, a surface loading system, a vacuum loading system, a displacement measuring system and a pore water pressure measuring system, wherein the model box is provided with a vacuum loading system; the displacement measurement system comprises a sedimentation measurement device and a lateral deformation measurement device, wherein the sedimentation measurement device comprises a vertical displacement sensor, a test wire, a magnetic gauge stand and a sedimentation mark, the vertical displacement sensor is fixed on a model box main body through the magnetic gauge stand, the lateral deformation measurement device is a flexible rubber strip, and the flexible rubber strip is adhered to a transparent organic glass wall through a transparent adhesive tape; the pore water pressure measuring system comprises a miniature pore water pressure gauge and a test wire. The model test device is simple to manufacture, convenient to operate and convenient to move, can enter a vacuum-surcharge combined pre-compression model test, comprehensively measure the sedimentation, lateral deformation and pore water pressure of the model foundation, and provides a basis for systematically researching the deformation rule of the drain board foundation and establishing and perfecting a prediction method.
Description
Technical Field
The invention belongs to the field of soft clay foundation treatment, relates to a model test device, and particularly relates to a model test device for a plastic drainage plate foundation under vacuum-stacking combined pre-pressing.
Background
Soft soil foundations are widely distributed in densely populated coastal areas, estuary areas and lake areas. In addition, with the rapid development of national economy in China, various dredging sludge hydraulic filling land-making projects in coastal areas form a large amount of soft soil foundations in recent years, so that the infrastructures (such as railways, highways, airports, factory building wharfs and ports) built in the soft soil areas are continuously increased and tend to be dense. Due to poor engineering properties of high water content, strong compressibility, low shear strength and the like of a soft soil foundation, excessive settlement and lateral deformation are easy to generate under the load action of newly-repaired buildings (such as roads and railway embankments), the deformation duration time of the foundation is long, and the deformation occupancy ratio after construction is large.
Excessive settlement and settlement difference easily cause inclination, cracking or change of the linearity of the upper structure, cause problems or diseases such as transition section jump, and seriously influence the normal use or operation of the structure and the circuit; excessive lateral deformation can cause extrusion and adverse effects on adjacent existing foundation foundations, cause excessive bending moment to be generated on adjacent piles, cause lateral movement of piers or bridge abutments, even cause damage to pile structures or underground pipelines, endanger stability and safety of existing building structures, and become a non-negligible problem in engineering design.
Therefore, how to quickly, effectively and economically treat soft soil foundations becomes a key problem to be considered in the field of foundation engineering. At present, the common soft soil foundation treatment method comprises the following steps: cement-soil mixing pile method, jet grouting pile method, cement fly ash gravel pile (CFG pile) method, plastic drainage Plate (PVD) method, etc. Wherein, the plastic drain board is widely used by combining the pre-pressing treatment method with the advantages of short construction period, no need of large-scale construction machinery, low cost, small environmental pollution and the like.
The prepressing mode of the plastic drain board method comprises preloading, vacuum prepressing and vacuum-preloading combined prepressing. Concerning the scheme of preloading, the inventors and other researchers have made some studies; as in paper "Experimental investigation of lateral displacement of PVD-improved deposit"(Geomechanics and Engineering,Vol.9,No.5(2015)585-599). but as found by later studies: preloading tends to create greater shear stresses in the foundation, causing lateral deformation of the foundation outward (away from the region of preloading) and squeezing adjacent foundation foundations or underground pipelines. Vacuum pressure is an isotropic "pumping" load that tends to cause lateral deformation of the foundation inward (toward the pre-load zone) and tends to cause cracking of the pre-load zone edges that affects the integrity and stability of the foundation.
The vacuum-preloading combined preloading method combines the advantages of the vacuum preloading method and the preloading method, so that post-construction settlement of the foundation can be further reduced, the construction period of an upper engineering structure is shortened, and a good reinforcement effect can be achieved on the foundation. The research on the construction method and mechanism of the vacuum-surcharge combined pre-compression technology through a model test is a precondition for promoting the technology to further mature and popularize and apply in a large area. Before the invention, the model test device is mainly aimed at a preloading method or a vacuum preloading method, and the measurement system is mainly focused on the model foundation settlement or the change rule of the super pore water pressure in the model foundation, so that the measurement of the lateral deformation of the model foundation is often ignored. The test device disclosed by the invention can be used for carrying out a model test of the vacuum-surcharge combined pre-pressing drainage plate foundation, comprehensively measuring the sedimentation, the super pore water pressure and the lateral deformation of the model foundation, and providing a test foundation and a basis for systematically researching the deformation rule of the drainage plate foundation and establishing and perfecting a prediction method.
Disclosure of Invention
The invention aims to solve the technical problem of providing a model test device for a plastic drainage plate foundation under vacuum-stacking combined pre-pressing, which can comprehensively measure sedimentation, super pore water pressure and lateral deformation at different positions of the model foundation, is convenient for acquiring more accurate and wide data, and provides a test basis for systematically researching the deformation rule of the drainage plate foundation and establishing and perfecting a prediction method.
In order to solve the technical problems, the invention adopts the following technical scheme:
the invention relates to a model test device for a vacuum-preloading combined soft soil foundation, which comprises a model box, a surface loading system, a vacuum loading system, a displacement measuring system and a pore water pressure measuring system, wherein the model box is provided with a vacuum loading system;
The model box comprises channel steel (18), a steel plate, a transparent organic glass plate (1) and rollers (16);
The surface loading system comprises a counter-force beam (19), a pressurizing cylinder (6), an air compressor (13), a barometer (20), a connecting pipe and a pressurizing steel plate (4);
The vacuum loading system comprises a vacuum pump (11), a suction bottle (9), a vacuum meter (12), a vacuum tube and a drain board (3);
the displacement measuring system comprises a sedimentation measuring device and a lateral deformation measuring device;
The settlement measurement device comprises a vertical displacement sensor (7), a test wire, a magnetic gauge stand and a settlement mark (8), wherein the vertical displacement sensor (7) is fixed on the model box main body through the magnetic gauge stand and is used for measuring the surface settlement of the model foundation, and the settlement mark (8) is used for measuring the settlement amounts at different positions in the model foundation; the lateral deformation measuring device is a flexible rubber strip (5), the flexible rubber strip (5) is stuck to the transparent organic glass wall (1) through a transparent adhesive tape in advance, when the model foundation is filled to the position of the transparent adhesive tape, the transparent adhesive tape is removed, the flexible rubber strip (5) is adsorbed to the transparent organic glass wall (1), and the position of the flexible rubber strip can be changed along with the deformation of the model foundation. Preferably, the number of the sedimentation targets is N; the number of the micro pore water pressure gauges (2) is N-1. As a further preferable scheme, pore water pressure gauges and sedimentation marks are alternately distributed, any one pore water pressure gauge is arranged at 1/2 of the distance between adjacent sedimentation marks, so that the pore water pressure change condition of soil layers between adjacent sedimentation marks can be reflected, the compression deformation of the soil layers between adjacent sedimentation marks can be calculated conveniently through pore water pressure measurement values, and the compression deformation is checked with the test results of the sedimentation marks, so that the test precision and reliability are improved.
The invention relates to a model test device for a vacuum-preloading soft soil foundation, which is characterized in that channel steel (18) is connected through bolts to form a model box frame, a steel plate forms a model bottom plate, transparent organic glass plates (1) form walls around the model box, and rollers (16) are arranged at four corners of the model box frame.
In the invention, the main body of the model box is made of metal material, channel steel is connected through bolts to form a model box frame, a steel plate forms a model bottom plate, transparent organic glass plates form walls around the model box, and rollers are arranged at four corners of the model box frame; the bottom plate of the model box and the transparent organic glass walls around are connected with the frame of the model box through bolts, and each connecting seam is sealed by sealant; uniformly coating a layer of lubricant (such as vaseline) for reducing friction between model foundation soil and the model box on the surfaces of the wall bodies around the model box; and 2 water draining holes are formed in the center line of the bottom plate of the model box, each water draining hole is connected with a water draining pipe connected with a valve, and the water outlet height of the water draining pipe is flush with the surface of the model foundation. Preferably, the model box bottom plate and the surface of the model foundation are paved with drainage geotextile, and the model test of double-sided drainage or single-sided drainage can be carried out by opening and closing the drainage valve of the model box bottom plate.
The invention relates to a model test device for a vacuum-preloading combined soft soil foundation, wherein a counterforce beam (19) of a surface loading system is I-steel, the counterforce beam is connected with a model box main body through bolts and channel steel (18), 3 pressurizing cylinders (6) are arranged at the midspan position of the counterforce beam (19) through bolts and are communicated with a barometer (20) and an air compressor (13) through connecting pipes, and 3 pressurizing steel plates (4) are connected with the pressurizing cylinders (6) through steel sleeves.
The invention relates to a model test device for a vacuum-preloading combined soft soil foundation, wherein a certain distance H is reserved between a drain board (3) of a vacuum loading system and the bottom of a model box, the top of the drain board (3) is connected with a plastic sealing cap (17) connected with vacuum pipes, each vacuum pipe is connected with a main vacuum pipe through a three-way joint, the main vacuum pipe is connected with a transparent suction filter bottle (9) provided with a vacuum gauge (12), and the suction filter bottle (9) is placed on an electronic scale (10) for weighing and is connected with a vacuum pump (11) through a vacuum pipe; the value of H is 8-12cm, preferably 10 cm.
The invention relates to a model test device for a vacuum-preloading combined soft soil foundation, wherein a pore water pressure measuring system comprises N-1 miniature pore water pressure meters (2) and a test wire, and the N-1 pore water pressure meters (2) are respectively buried at different depths of the center of the model foundation. And N is the number of sedimentation marks, and N is more than or equal to 3.
The invention relates to a model test device for a vacuum-preloading combined soft soil foundation, wherein a model box bottom plate and four-side transparent organic glass walls (1) are connected with a model box frame through bolts, and each connecting seam is sealed by sealant.
The invention relates to a model test device for a vacuum-preloading soft soil foundation, wherein 2 drain holes are formed in the center line of a bottom plate of a model box, each drain hole is respectively connected with a drain pipe (15) connected with a drain valve (14), and the height of a water outlet of the drain pipe (15) is flush with the surface of the model foundation.
According to the model test device for the vacuum-preloading soft soil foundation, disclosed by the invention, drainage geotextiles are paved on the surfaces of the bottom plate of the model box and the model foundation, and a model test of double-sided drainage or single-sided drainage can be carried out by opening and closing the drainage valve (14) of the bottom plate of the model box.
The invention relates to a model test device for a vacuum-preloading combined soft soil foundation, wherein a plastic sealing cap (17) at the top of a drain board is inserted 8-12 cm below the surface of the model foundation, preferably 10 cm, and foundation soil and slurry are densely filled above the plastic sealing cap (17) at the top of the drain board to the surface of the model foundation.
The invention relates to a model test device for a vacuum-preloading combined soft soil foundation, which comprises 3 pressurized steel plates (4), wherein the applied load of the middle steel plate is 2 times of that of the steel plates at two sides.
The invention relates to a model test device for a vacuum-surcharge combined prepressing soft soil foundation, wherein a settlement mark (8) is stuck to a transparent organic glass wall (1) in advance through a transparent adhesive tape, when the model foundation is filled to the position of the transparent adhesive tape, the transparent adhesive tape is removed, the settlement mark (8) is adsorbed to the transparent organic glass wall (1), the position of the settlement mark can be changed along with the deformation of the model foundation, and the vertical position change of the settlement mark (8) before and after loading is the settlement of the initial position of the settlement mark (8) in the model foundation.
The invention relates to a model test device for a vacuum-preloading combined pre-compaction soft soil foundation, wherein the horizontal position change of a flexible rubber strip (5) before and after loading is the lateral deformation of the initial position of the flexible rubber strip (5) in the model foundation.
The invention relates to a model test device for a vacuum-preloading soft soil foundation, which is characterized in that a layer of lubricant (such as vaseline) for reducing friction between model foundation soil and a model box is uniformly smeared on the surfaces of wall bodies around the model box before the model foundation is filled.
The beneficial effects of the invention are as follows:
1. By combining the sedimentation measurement system, the lateral displacement measurement system and the pore water pressure measurement system, the sedimentation, the lateral deformation and the super pore water pressure at different positions of the model foundation are comprehensively measured, so that more accurate and wide data can be conveniently obtained;
2. the stacking distribution in the actual engineering is simulated more truly through the combination of 3 pressurizing cylinders and 3 side pressing plates;
3. The model box wall adopts transparent organic glass, so that layered settlement and lateral deformation of the model foundation can be intuitively measured;
4. A layer of lubricant (such as vaseline) is uniformly smeared on the surfaces of the walls around the model box, so that friction between the walls and model foundation soil is reduced, and accurate data can be obtained through measurement;
5. The bottom of the model box is provided with rollers, so that the movement is convenient;
6. The water outlet of the drain pipe connected with the drain hole of the bottom plate of the model box is flush with the model foundation, so that the influence of suction on a test result is eliminated, and accurate data can be conveniently obtained through measurement;
7. The pore water pressure gauges and the sedimentation marks are alternately distributed, the pore water pressure gauges are arranged at 1/2 of the distance between the adjacent sedimentation marks, so that the pore water pressure change condition of the soil layer between the adjacent sedimentation marks can be reflected, the compression deformation of the soil layer between the adjacent sedimentation marks can be calculated through the pore water pressure conveniently, the test results of the pore water pressure gauges and the sedimentation marks are mutually checked, and the test precision and reliability are improved; in a word, this device form is simple nimble, simple manufacture, convenient operation, with low costs, be convenient for remove, the suitability is strong, has filled the blank that current model test device is mainly singly aimed at surcharge pre-compaction method or vacuum pre-compaction method, and is convenient for obtain more accurate and extensive data, reflects the subsidence of model foundation, side direction warp and the change law of inside super pore water pressure comprehensively.
Drawings
Fig. 1 is a top view of a mold box.
Fig. 2 is an elevation schematic view of the present invention.
Fig. 3 is a right side view of the mold box.
FIG. 4 is a schematic illustration of PVD contemplated.
In the figure: 1. transparent organic glass wall; 2. a pore pressure gauge; 3. a drain plate; 4. a pressurized steel plate; 5. a flexible rubber strip; 6. a pressurizing cylinder; 7. a vertical displacement sensor; 8. sedimentation marks; 9. a suction filtration bottle; 10. an electronic scale; 11. a vacuum pump; 12. a vacuum gauge; 13. an air compressor; 14. a valve; 15. a drain pipe; 16. a roller; 17. a plastic sealing cap; 18. channel steel; 19. a reaction beam; 20. barometer.
Detailed Description
The following describes specific embodiments of the present invention in detail with reference to the drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.
As shown in fig. 1 and2, the model test device for the plastic drainage plate foundation under the vacuum-stacking combined pre-pressing comprises a model box, a surface loading system, a vacuum loading system, a displacement measuring system and a pore water pressure measuring system. The model box comprises channel steel 18, steel plates, transparent organic glass plates 1, bolts and rollers 16; the surface loading system comprises a counter-force beam 19, a pressurizing cylinder 6, an air compressor 13, a barometer 20, a connecting pipe and a pressurizing steel plate 4; the vacuum loading system comprises a vacuum pump 11, a suction bottle 9, a vacuum tube and a drain plate 3; the displacement measuring system comprises a sedimentation measuring device and a lateral deformation measuring device; the pore water pressure measuring system comprises a miniature pore water pressure gauge 2 and a test wire; the drainage geotextile is paved on the bottom surface and the surface of the model foundation, and the model test of double-sided drainage or single-sided drainage can be carried out by opening and closing the model box bottom plate drainage valve 14. The model box body is made of metal materials, the peripheral frames are formed by connecting channel steel 18 through bolts, the top counter-force beam 19 is made of I-steel, the bottom of the counter-force beam is supported by steel plates, 2 drain holes are formed in the center line of the bottom plate, each drain hole is connected with a drain pipe 15 connected with a drain valve 14, and the water outlet height of the drain pipe 15 is flush with the surface of the model foundation; the transparent organic glass plates 1 form wall bodies around the model box, the bottom plate of the model box and the transparent organic glass walls 1 around are connected with the frame of the model box through bolts, and all connecting joints are sealed by sealant; uniformly coating a layer of lubricant (such as vaseline) for reducing friction between model foundation soil and the model box on the surfaces of the wall bodies around the model box; the rollers 16 are mounted at four corners of the mold box frame for movement.
The surface loading system pressurizing cylinders 6 are 3, are mounted at the mid-span position of the counter-force beam 19 through bolts, are communicated with the barometer 20 and the air compressor 13 through connecting pipes, the number of the pressurizing steel plates 4 is 3, and are connected with the pressurizing cylinders 6 through steel sleeves, so that the pressurizing steel plates are in a simulated stacking distribution mode, and the applied load of the middle steel plates is 2 times that of the steel plates at two sides.
The drain plates of the vacuum loading system are made of geotextile, and each drain plate 3 is inserted into the model foundation by means of steel bars. The top of the drain plate 3 is connected with a plastic sealing cap 17 connected with a vacuum tube, the top of the drain plate top cap 17 is inserted 10 cm below the surface of the model foundation, foundation soil and slurry are densely filled above the drain plate top cap 17 to the surface of the model foundation, each vacuum tube connected with the drain plate 3 is connected with a main vacuum tube through a three-way joint, the main vacuum tube is connected with a transparent suction bottle 9 provided with a vacuum gauge 12, the vacuum gauge 12 is arranged on a sealed bottle mouth of the suction bottle 9, the suction bottle 9 is placed on an electronic scale 10 for weighing, and the vacuum bottle is connected with a vacuum pump 11 through the vacuum tube.
The settlement measurement device of the displacement measurement system comprises a vertical displacement sensor 7, a test wire, a magnetic gauge stand and a settlement mark 8, wherein the vertical displacement sensor 7 is fixed on a model box main body through the magnetic gauge stand and is used for measuring surface settlement of a model foundation, the settlement mark 8 is pasted on the transparent organic glass wall 1 through a transparent adhesive tape in advance, when the model foundation is filled to the position of the transparent adhesive tape, the transparent adhesive tape is removed, the settlement mark 8 is adsorbed on the transparent organic glass wall 1, the position of the settlement mark can change along with deformation of the model foundation, and the vertical position change of the settlement mark 8 before and after loading is the settlement of the initial position of the settlement mark 8 in the model foundation; the lateral deformation measuring device is a flexible rubber strip 5, the flexible rubber strip 5 is stuck to the transparent organic glass wall 1 through a transparent adhesive tape in advance, when the model foundation is filled to the position of the transparent adhesive tape, the transparent adhesive tape is removed, the flexible rubber strip 5 is adsorbed to the transparent organic glass wall 1, the position of the flexible rubber strip 5 can be changed along with the deformation of the model foundation, and the change of the horizontal position of the flexible rubber strip 5 before and after loading is the lateral deformation of the initial position of the rubber strip 5 in the model foundation.
The pore water pressure measuring system comprises a miniature pore water pressure gauge 2 and a test wire, wherein the pore water pressure gauge 2 is buried in the center of the model foundation at different depths so as to measure pore water pressure at different height positions.
The specific use process of the device is as follows:
Firstly, paving drainage geotechnical cloth on the bottom surface of a model box to serve as a bottom surface drainage layer; uniformly coating a layer of lubricant (such as vaseline) for reducing friction between model foundation soil and the model box on the surfaces of the wall bodies around the model box; the transparent organic glass walls 1 on the front and the back of the model box are provided with sedimentation marks 8, and the number and the interval are determined according to experimental requirements; the intersection point of the edge line of the transparent organic glass wall 1 and the edge line of the pressurizing steel plate 4 is vertically provided with flexible rubber strips 5, and a plurality of flexible rubber strips 5 can be arranged in a certain range from the edge line of the pressurizing steel plate 4, wherein the quantity and the interval are determined according to experimental requirements and are used for observing the lateral deformation of a model foundation; filling a model box with a homogeneous soil sample, embedding pore water pressure gauges 2 along the center line of the model foundation during filling, wherein the number and the interval are determined according to experimental requirements, and the interval is ensured to be uniform as much as possible during setting; after filling soil reaches a designed elevation, paving drainage geotextile on the surface of model foundation soil as a surface drainage layer, and pre-compacting and solidifying for a period of time by using iron blocks or concrete blocks; removing the pre-pressing load after pre-pressing consolidation, lifting the surface drainage geotextile, inserting the drain plate 3 into the pre-pressed model foundation by means of steel bars, keeping a certain distance between the drain plate 3 and the bottom of the model box, and re-covering the surface drainage geotextile after the drain plate is inserted; each vacuum tube connected with the drain plate 3 is connected with a main vacuum tube through a three-way joint, and the main vacuum tube is connected with a transparent suction filtration bottle 9 provided with a vacuum gauge 12; the vacuum gauge 12 is arranged on a sealed bottle opening of the suction filter bottle 9, and the suction filter bottle 9 is placed on the electronic scale 10 for weighing and is connected with the vacuum pump 11 through a vacuum tube; the pressurizing cylinder 6 is communicated with the barometer 20 and the air compressor 13 through connecting pipes; the three pressurizing steel plates 4 are connected with the pressurizing cylinder 6 through steel sleeves, and each pressurizing steel plate 4 is provided with a vertical displacement sensor 7 for measuring the earth surface subsidence; finally, vacuum-surcharge combined pre-pressing experiment is carried out.
The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the specific details of the above embodiments, and various simple modifications can be made to the technical solution of the present invention within the scope of the technical concept of the present invention, and all the simple modifications belong to the protection scope of the present invention.
Claims (9)
1. A model test device of vacuum-surcharge combined prepressing soft soil foundation is characterized in that: the device comprises a model box, a surface loading system, a vacuum loading system, a displacement measuring system and a pore water pressure measuring system;
the model box comprises channel steel (18), a steel plate, a transparent organic glass plate (1) and rollers (16);
the surface loading system comprises a counter-force beam (19), a pressurizing cylinder (6), an air compressor (13), a barometer (20), a connecting pipe and a pressurizing steel plate (4);
the vacuum loading system comprises a vacuum pump (11), a suction bottle (9), a vacuum meter (12), a vacuum tube and a drain board (3);
the displacement measuring system comprises a sedimentation measuring device and a lateral deformation measuring device;
The settlement measurement device comprises a vertical displacement sensor (7), a test wire, a magnetic gauge stand and a settlement mark (8), wherein the vertical displacement sensor (7) is fixed on the model box main body through the magnetic gauge stand and is used for measuring the surface settlement of the model foundation, and the settlement mark (8) is used for measuring the layered settlement of the model foundation; the lateral deformation measuring device is a flexible rubber strip (5), the flexible rubber strip (5) is stuck to the transparent organic glass plate (1) through a transparent adhesive tape in advance, when the model foundation is filled to the position of the transparent adhesive tape, the transparent adhesive tape is removed, the flexible rubber strip (5) is adsorbed to the transparent organic glass plate (1), and the position of the flexible rubber strip can be changed along with the deformation of the model foundation;
the surface loading system counter-force beam (19) is I-steel, the counter-force beam is connected with the model box body through bolts and channel steel (18), the number of the pressurizing cylinders (6) is 3, the pressurizing cylinders are arranged at the middle-span position of the counter-force beam (19) through bolts, the pressurizing cylinders are communicated with the barometer (20) and the air compressor (13) through connecting pipes, and the pressurizing steel plates (4) are 3 and are connected with the pressurizing cylinders (6) through steel sleeves;
the drainage plate (3) of the vacuum loading system keeps a certain distance H with the bottom of the model box, the top of the drainage plate (3) is connected with a plastic sealing cap (17) connected with a vacuum tube, each vacuum tube is connected with a main vacuum tube through a three-way joint, the main vacuum tube is connected with a transparent suction bottle (9) provided with a vacuum meter (12), and the suction bottle (9) is placed on an electronic scale (10) to be weighed and connected with a vacuum pump (11) through the vacuum tube; the value of H is 8-12 cm.
2. The model test device for the vacuum-preloading soft soil foundation according to claim 1, wherein: the channel steel (18) is connected through bolts to form a model box frame, the steel plate forms a model bottom plate, the transparent organic glass plate (1) forms walls around the model box, and the rollers (16) are arranged at four corners of the model box frame.
3. The model test device for the vacuum-preloading soft soil foundation according to claim 1, wherein: the value of H is 10 cm.
4. The model test device for the vacuum-preloading soft soil foundation according to claim 1, wherein: the pore water pressure measuring system comprises N miniature pore water pressure meters (2) and a test wire, wherein the N pore water pressure meters (2) are respectively buried in different depths of the center of the model foundation.
5. The model test device for the vacuum-preloading soft soil foundation according to claim 1, wherein: the model box bottom plate and the surrounding transparent organic glass plates (1) are connected with the model box frame through bolts, and all connecting joints are sealed by sealant.
6. A model test apparatus for a vacuum-preloading soft soil foundation according to any one of claims 1-5, wherein: 2 water draining holes are formed in the center line of the bottom plate of the model box, each water draining hole is connected with a water draining pipe (15) connected with a water draining valve (14), and the water outlet height of the water draining pipe (15) is flush with the surface of the model foundation.
7. The model test device for the vacuum-preloading soft soil foundation according to claim 4, wherein: and the model box bottom plate and the surface of the model foundation are paved with drainage geotextile, and a model test of double-sided drainage or single-sided drainage can be carried out by opening and closing a model box bottom plate drainage valve (14).
8. The model test device for the vacuum-preloading soft soil foundation according to claim 4, wherein: the plastic sealing cap (17) at the top of the drain board is inserted 8-12 cm below the surface of the model foundation, and foundation soil and slurry are densely filled above the plastic sealing cap (17) at the top of the drain board to the surface of the model foundation.
9. A model test apparatus for a vacuum-preloading soft soil foundation according to any one of claims 1 or 4, wherein:
The settlement marks (8) are stuck to the transparent organic glass plate (1) through transparent adhesive tapes in advance, when the model foundation is filled to the position of the transparent adhesive tapes, the transparent adhesive tapes are removed, the settlement marks (8) are adsorbed to the transparent organic glass plate (1), the positions of the settlement marks can be changed along with the deformation of the model foundation, and the vertical position change of the settlement marks (8) before and after loading is the settlement of the initial position of the settlement marks (8) in the model foundation;
The horizontal position change of the flexible rubber strip (5) before and after loading is the lateral deformation of the initial position of the flexible rubber strip (5) in the model foundation.
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| DE10064187C1 (en) * | 2000-12-22 | 2002-05-08 | Keller Grundbau Gmbh | Diameter measuring device for ground foundation or wall element has measuring element provided by rod-shaped profile with 2 concave strips pressed together for switching from flexible state to rigid state |
| CN104264719A (en) * | 2014-09-03 | 2015-01-07 | 上海大学 | Vacuum preloading indoor model testing apparatus |
| CN104790442A (en) * | 2015-05-05 | 2015-07-22 | 温州大学 | Large-sized testing device of model test for treating soft soil foundation by vacuum preloading method and testing method thereof |
| CN106840086A (en) * | 2017-02-22 | 2017-06-13 | 天津城建大学 | The rapidly solidified weak soil experimental rig of low Low Level vacuum method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE10064187C1 (en) * | 2000-12-22 | 2002-05-08 | Keller Grundbau Gmbh | Diameter measuring device for ground foundation or wall element has measuring element provided by rod-shaped profile with 2 concave strips pressed together for switching from flexible state to rigid state |
| CN104264719A (en) * | 2014-09-03 | 2015-01-07 | 上海大学 | Vacuum preloading indoor model testing apparatus |
| CN104790442A (en) * | 2015-05-05 | 2015-07-22 | 温州大学 | Large-sized testing device of model test for treating soft soil foundation by vacuum preloading method and testing method thereof |
| CN106840086A (en) * | 2017-02-22 | 2017-06-13 | 天津城建大学 | The rapidly solidified weak soil experimental rig of low Low Level vacuum method |
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