CN109881720B - Pile-soil model testing machine for simulating soil body in-situ state and working method - Google Patents

Pile-soil model testing machine for simulating soil body in-situ state and working method Download PDF

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Publication number
CN109881720B
CN109881720B CN201910223331.4A CN201910223331A CN109881720B CN 109881720 B CN109881720 B CN 109881720B CN 201910223331 A CN201910223331 A CN 201910223331A CN 109881720 B CN109881720 B CN 109881720B
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pile
soil
vertical plate
plate
model
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CN109881720A (en
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吴则祥
余闯
涂冬媚
杨昱
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Wenzhou University
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Wenzhou University
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Abstract

The invention relates to a pile-soil model testing machine for simulating a soil body in an in-situ state and a working method thereof, wherein the pile-soil model testing machine comprises the following steps: the bottom plate includes: the bottom plate comprises a bottom plate main body, a first blocking platform and a second blocking platform, wherein the first blocking platform and the second blocking platform are cylindrical and are arranged on the upper side of the bottom plate main body; the first vertical plate is clamped between the first blocking platform and the second blocking platform; the second baffle is clamped between the gaps of the first vertical plate and the second vertical plate; the bottom plate is fixedly connected with the first vertical plate and the second vertical plate; the top ends of the first vertical plate and the second vertical plate are also provided with circular ring connecting plates; the inner side of the second vertical plate is provided with a plurality of grooves, the outer side of the top pressing plate is provided with a plurality of bulges, and the central part of the top pressing plate is provided with a hole. By adopting the pile-soil model testing machine for simulating the soil body in the in-situ state and the working method thereof, the situation of the soil body under different temperature change paths can be simulated, and the mechanical behavior of the pile soil under the situation can be researched.

Description

Pile-soil model testing machine for simulating soil body in-situ state and working method
Technical Field
The invention relates to the technical field of rock and soil tests, in particular to a model pile tester capable of controlling soil body temperature and a test method thereof.
Background
The applicant filed the same day with the 'model pile tester capable of controlling soil body temperature and test method thereof' is a basic patent of the application, and the purpose is mainly as follows: simulating the influence of soil layers with different heights on a pile foundation under different temperature stress paths; the indoor simulation test is carried out substantially; i.e. the pile length-soil layer distribution is simulated according to a certain proportion.
However, due to the size of the tester, there is a certain difference between the results of the above test and the actual in-situ test.
Therefore, whether a pile-soil testing machine capable of simulating the actual soil state can be developed or not can be determined, so that the soil is in the actual state, and the measured pile-soil action result is close to the actual result.
Disclosure of Invention
The invention aims to provide a pile-soil model testing machine for simulating a soil body in an in-situ state and a testing method thereof, so as to accurately simulate the acting force of each soil body and pile at different depths.
A pile-soil model testing machine for simulating soil body in-situ state comprises: the pile model comprises a bottom plate, a first vertical plate, a second vertical plate, a top pressing plate and a pile model;
the first vertical plate and the second vertical plate are cylindrical, the cross sections of the first vertical plate and the second vertical plate are both circular, the first vertical plate is arranged on the outer side of the second vertical plate, and a hole is formed between the first vertical plate and the second vertical plate;
the bottom plate includes: the bottom plate comprises a bottom plate main body, a first blocking platform and a second blocking platform, wherein the first blocking platform and the second blocking platform are cylindrical and are arranged on the upper side of the bottom plate main body; the first vertical plate is clamped between the first blocking platform and the second blocking platform; the second baffle is clamped between the gaps of the first vertical plate and the second vertical plate; the bottom plate is fixedly connected with the first vertical plate and the second vertical plate; the top ends of the first vertical plate and the second vertical plate are also provided with circular ring connecting plates;
the cross section of the top pressing plate is circular, and the size of the top pressing plate is matched with the opening of the second vertical plate;
a plurality of grooves are formed in the inner side of the second vertical plate (the grooves are vertical, the height of the grooves does not need to be arranged along the entire length of the second vertical plate, and only needs to be arranged in the top area of the second vertical plate, such as 30-50 cm), and a plurality of protrusions protruding out of the top pressing plate are arranged on the outer side of the top pressing plate, are inserted into the grooves of the second vertical plate and can slide up and down; a hole is formed in the central part of the top pressing plate;
further comprising: the first loading system is connected with the top pressing plate, a push rod of the first loading system is connected with the top of the top pressing plate, and a pressure sensor is arranged on the contact surface of the first loading system and the top pressing plate;
the central part of the top pressing plate is provided with a hole, the central part of the bottom plate is provided with a hole, and the sizes of the hole of the top pressing plate and the hole of the bottom plate are matched with the size of the pile model.
Further, the pile model is a hollow pile.
Furthermore, a strain gauge is bonded on one side, relative to the first vertical plate, of the second vertical plate, and a gap between the first vertical plate and the second vertical plate is inflated or filled with water so as to keep pressure with the second vertical plate; and adjusting the air pressure or the water pressure according to the size of the strain gauge adhered to one side of the second vertical plate relative to the first vertical plate.
Furthermore, a water filtering layer is laid on the upper surface of the bottom plate, a drain pipe is arranged inside the bottom plate main body so that water in the water filtering layer can flow out of the drain pipe of the bottom plate main body, and a control valve is arranged outside the drain pipe; the drainage condition of the drainage pipe is controlled through the control valve, and therefore the soil body is simulated to be in a drainage state or a non-drainage state.
Further, still include: the bottom membrane and the side membrane are arranged on the upper side of the water filtering layer, and the top membrane is arranged on the lower side of the top pressing plate; the soil body is enclosed among the bottom film, the side films and the top film, wherein the side films are arranged on the inner surface of the second vertical plate in advance.
Further, still include: the pile model supporting device comprises a top supporting frame, a bottom plate and a pile model supporting device, wherein the bottom plate is supported on the top supporting frame; pile model strutting arrangement includes: the clamp is provided with a power mechanism at the lower side of the clamp; the power mechanism is fixed on the ground; and a tension sensor is arranged between the pile model supporting device and the pile model.
A working method of a pile-soil model testing machine for simulating a soil body in an in-situ state comprises the following steps:
firstly, a pile model passes through a hole of a top pressing plate and a hole of a bottom plate in advance, and then the bottom of the pile model is arranged on a pile model supporting device;
secondly, filling soil: then, arranging a water filtering layer on the bottom plate, and then paving a bottom film on the water filtering layer; then laying soil in layers;
after the soil filling is finished, soaking and standing the model foundation for a week;
thirdly, soil consolidation: the first loading system starts to operate, so that the top pressing plate keeps a preset stress on the soil body; consolidation was carried out under these conditions for 1 week; the control valve is always in an open state;
fourth, test: and (4) pulling down the pile model by using the pile model supporting device, and carrying out a static load test to obtain the relation of the pile side frictional resistance f-settlement s of the soil layer.
Further, a second loading mechanism of the pile model is arranged at the upper part; a tensioning film is stuck at the opening of the top pressing plate so as to seal the opening; a rigid layer which is radially separated from the peripheral water filtering layer is arranged at the position of the water filtering layer relative to the hole of the bottom plate; the opening of the bottom plate is provided with an expansion extrusion layer, namely the expansion extrusion layer is plugged into the hole of the bottom plate.
A working method of a pile-soil model testing machine for simulating a soil body in an in-situ state comprises the following steps:
firstly, determining the diameter of a second vertical plate according to the property of a soil body and the size of a pile model;
secondly, a tensioning film is adhered to the hole of the top pressing plate, and an expansion extrusion layer is arranged in the hole of the bottom plate; then arranging the bottom of the pile model on a pile model supporting device;
thirdly, filling soil: then, arranging a water filtering layer on the bottom plate, arranging a rigid layer at the position of the water filtering layer corresponding to the pile foundation, and then paving a bottom film on the water filtering layer; then laying soil in layers; after the soil filling is finished, soaking and standing the model foundation for a week to fully saturate the soil body;
fourthly, soil consolidation: the first loading system starts to operate, so that the top pressing plate keeps a preset stress on the soil body; consolidation was carried out under these conditions for 1 week; the control valve is always in an open state;
fifthly, pressing in the pile model: the second loading system starts to apply force to the pile model and pushes the pile model downwards until the pile model penetrates through the bottom plate;
sixth, test: and (5) carrying out static load test to obtain the relation of the pile side frictional resistance f-settlement s.
Further, according to the properties of the soil body and the size of the pile model, the diameter of the second vertical plate is determined in the following mode:
when the pile model is circular, D represents the diameter of the pile model;
when the pile model is square, D represents the side length of the longer side of the pile model;
the diameter of the second vertical plate is recorded as D1;
the following equation needs to be satisfied:
further, D1 satisfies:
furthermore, a cold and hot circulating pipe is arranged in the pile model and is communicated with an external circulating liquid temperature regulating system.
By adopting the technical scheme, compared with the prior art, the method has the advantages of the following points.
Firstly, the test instrument of the application is researched for a certain layer of soil body, and the model proportion can be 1:1 (when only a certain soil layer is researched, the length of a pile model is only 10cm-50cm longer than the height of the soil layer); two different design structures are provided aiming at different forms of large-diameter piles, small-diameter piles, drilled piles, pressed piles and the like, and the structures correspond to respective working methods.
Secondly, the top pressing plate is the key for realizing the in-situ state of the soil body, and the groove 2-2-1 of the second vertical plate 2-2 and the bulge of the top pressing plate are the key for ensuring the closing between the top pressing plate and the second vertical plate.
Thirdly, when simulating the soil-extruding pile, the size of the second side plate is equivalent to that of the pile model, and the related judgment standard, namely the relation between D1 and D, is given in the application.
Fourthly, the embodiment I is used for simulating a large-diameter pile, and innovatively provides that a loading system of a pile foundation is arranged at the bottom, so that the burying of a soil body can be completed, and the conflict of spatial arrangement with the loading system of a top pressing plate is avoided; the embodiment is used for simulating the soil-extruding pile of the pipe pile, and the design difficulty mainly lies in: how to simulate the insertion of a pile foundation into a soil body; because the bottom plate of the testing machine must be provided with holes, the key point is how to prevent the soil body from flowing out of the holes of the bottom plate when the pile model is inserted into the soil body. The present application solves the above problem by means of a rigid layer 9 and an expanded extruded layer 10.
Fifth, the fourth embodiment proposes: the second side plate has a bending problem when the soil pressure is large; it proposes that: the strain gauge detects, and the above problem is improved by air pressure or water pressure.
Sixth, the invention has a value in engineering application in that the development law of the side frictional resistance of the pile under different pile types (round pile, square pile or pile with other shape) and different pile foundation surface conditions (such as concrete pile, steel pipe concrete pile, pattern arranged on the outer surface of the concrete pile, pattern arranged on the periphery of the steel pipe concrete pile, etc.) can be conveniently studied.
Description of the drawings:
FIG. 1: the cross-sectional schematic view of the pile-soil model testing machine in the simulated soil body in-situ state according to the first embodiment.
FIG. 2: a top view of the base plate of embodiment one.
FIG. 3: a top view of the second vertical plate of embodiment one.
FIG. 4: top platen top view (cylinder) of example one.
FIG. 5: top platen top view of example one (square column).
FIG. 6: the first load of example one places the top platen pressurized in the layout.
FIG. 7: the cross-sectional schematic view of the pile-soil model testing machine in the simulated soil body in-situ state of the second embodiment.
FIG. 8: design of the rigid layer and the expanded extruded layer of example two.
FIG. 9: the calculation results of the formula (1) and the formula (2) in the second example.
FIG. 10: the fourth embodiment is a schematic cross-sectional view of a pile-soil model testing machine for simulating a soil body in an in-situ state.
FIG. 11: the second vertical plate of the fourth embodiment can bend under the lateral pressure of the soil body.
FIG. 12: the second vertical plate and the first vertical plate of the fourth embodiment are kept vertical in an air inflation or water filling mode.
Detailed Description
The first embodiment is as follows: as shown in fig. 1 to 6, a pile-soil model testing machine for simulating a soil body in-situ state includes: the device comprises a bottom plate 1, a first vertical plate 2-1 and a second vertical plate 2-2;
the first vertical plate 2-1 and the second vertical plate 2-2 are cylindrical, the cross sections of the first vertical plate and the second vertical plate are both circular (concentric circles), the first vertical plate 2-1 is arranged on the outer side of the second vertical plate 2-2, and a pore is formed between the first vertical plate and the second vertical plate;
the base plate 1 includes: the bottom plate comprises a bottom plate main body, a first baffle table 1-1 and a second baffle table 1-2, wherein the first baffle table 1-1 and the second baffle table 1-2 are both cylindrical and are arranged on the upper side of the bottom plate main body;
the first vertical plate 2-1 is clamped between the first baffle table 1-1 and the second baffle table 1-2; the second baffle table 1-2 is clamped between the gap between the first vertical plate 2-1 and the second vertical plate 2-2;
the bottom plate 1 is fixedly connected with the first vertical plate 2-1 and the second vertical plate 2-2; the top ends of the first vertical plate 2-1 and the second vertical plate 2-2 are also provided with a circular ring connecting plate 4; the central part of the bottom plate 1 is also provided with a hole 1-3;
further comprising: the cross section of the top pressing plate 3 is circular, and the size of the top pressing plate is matched with the opening of the second vertical plate 2-2;
a plurality of grooves 2-2-1 are arranged on the inner side of the second vertical plate 2-2, a plurality of bulges 3-1 are arranged on the outer side of the top pressing plate 3, and a hole 3-2 is formed in the central part of the top pressing plate 3;
a water filtering layer 5 is laid on the upper surface of the bottom plate 1, a drain pipe is arranged in the bottom plate main body so that water in the water filtering layer can flow out of the drain pipe of the bottom plate main body, and a control valve is arranged on the outer side of the drain pipe; the drainage condition of the drainage pipe is controlled through the control valve, so that the soil body is simulated to be in a drainage state or a non-drainage state;
the size of the hole 3-2 of the top press plate 3 and the size of the hole 1-3 of the bottom plate 1 are matched with the size of the pile model 6.
Further comprising: the pile model supporting device comprises a top supporting frame, a bottom plate 1 is supported on the top supporting frame, and a pile model supporting device 8 and the bottom plate supporting frame are arranged below the bottom plate 1;
the pile model support device 8 comprises: the clamp holder 8-1, a power mechanism 8-2 is arranged at the lower side of the clamp holder 8-1; the power mechanism 8-2 is fixed on the ground;
and a tension sensor is arranged between the pile model supporting device 8 and the pile model.
Further comprising: a bottom membrane (arranged on the upper side of the water filtering layer 5), a side membrane and a top membrane (arranged on the lower side of the top pressing plate 3); the periphery of the soil body is enclosed among the bottom film, the side films and the top film, wherein the side films are arranged on the inner surface of the second vertical plate 2-2 in advance.
Further comprising: the first loading system 9 is connected with the top pressing plate 3, a push rod of the first loading system 9 is connected with the top of the top pressing plate 3, and a pressure sensor is arranged on the contact surface of the first loading system 9 and the top pressing plate 3;
the first loading system 9 comprises a plurality of push rods (preferably 8 push rods) which are distributed around the circle center of the top pressing plate in an annular array, so that the first loading system 9 can keep a certain pressure on the top pressing plate, and the top pressing plate can keep a certain pressure on the soil body;
the stress on the top of the soil (from the top platen) matches the original position of the soil, for example, to simulate a soil 5-7m below the ground, the stress given to the soil by the top platen should be: sigma gamma h; the soil height in the tester is filled by 2 m.
And a strain gauge and a pressure sensor are stuck on the surface of the pile model 6.
The working method of the first embodiment is as follows:
first, pile pattern 6 is pre-threaded through hole 3-2 of top platen 3; holes 1-3 of the bottom plate 1, and then the bottom of the pile model is arranged on the pile model supporting device 8;
secondly, filling soil: then, arranging a water filtering layer 5 on the bottom plate 1, and then paving a bottom film (holes are also formed at the positions of the pile models and penetrate through the upper parts of the pile models) on the water filtering layer 5; then laying soil in layers;
after the soil filling is finished, soaking and standing the model foundation for a week;
thirdly, soil consolidation: the first loading system starts to operate, so that the top pressing plate keeps a preset stress on the soil body; consolidation was carried out under these conditions for 1 week; the control valve is always in an open state;
fourth, test: the pile model is pulled down (equivalent to pile foundation settlement) by using the pile model supporting device 8, and a static load test is carried out to obtain the relation of the pile side frictional resistance f-settlement s of the soil layer; the pile side resistance development law of the soil bodies with different stratum heights can be accurately researched (the in-situ state of the soil bodies with different stratum heights can be realized by changing the pressure of the first loading system 9).
The key points of the above test are also: the self weight of the pile model is smaller than the side frictional resistance of the pile; therefore, the pile model should be made as a hollow pile in order to reduce the self weight.
Embedding the pile model in an instrument in advance, and then filling soil; when the soil body is buried underground, the pile foundation has certain influence on the soil body, and the method is mainly suitable for the situation of drilled piles or large-diameter piles.
However, the method of comparative example 1 has a serious problem in the case of the soil-extruding pile such as a pipe pile. However, if the method of comparative example 1 is not adopted, i.e. the soil is not buried in the apparatus first, the soil body will fall from the bottom plate due to the open pores on the bottom plate;
meanwhile, when the soil body is used for simulating the in-situ stress, a top pressing plate is needed to pressurize the soil body, an opening is formed in the top pressing plate, and when the top pressing plate pressurizes the soil body, the soil body can protrude from the opening;
therefore, in the design of the present application, the difficulty actually comes from: the problem caused by inserting the pile model into the soil body.
Example two:
fig. 7-8 show the structural design of the second embodiment.
A tensioning film is stuck at the opening of the top pressing plate 3 so as to seal the opening; when the pile is pressed in, the tensioning film of the top pressing plate 3 is taken away;
and a rigid layer 9 which is radially separated from the peripheral water filtering layer is arranged at the position of the water filtering layer 5 relative to the hole of the bottom plate 1;
an expansion extrusion layer 10 is arranged at the opening of the bottom plate 1, namely the expansion extrusion layer 10 is plugged into the hole of the bottom plate 1;
in the pile pressing process of the pile model, when the pile model reaches the bottom, the rigid layer and the expansion extrusion layer are extruded out; and meanwhile, lubricating oil is smeared on the surface of the opening of the bottom plate 1 (the frictional resistance of the opening of the bottom plate 1 to the pile model is reduced, and the measurement precision is improved).
When the pile model 6 is circular, D represents its diameter; when the pile model 6 is square, D represents the side length of the longer side;
the diameter of the second vertical panel 2-2 is recorded as D1;
the following conditions need to be satisfied:
further, D1 preferably satisfies:
the expressions on the right sides of the formulas (1) and (2) represent the influence range of the soil body in the pile pressing process, and the calculation results of the formulas (1) and (2) are shown in fig. 9.
The second loading mechanism of the pile model is arranged at the upper part.
The working method comprises the following steps:
firstly, determining the diameter of the second vertical plate 2-2 according to the property of soil mass and the size of a pile foundation;
secondly, a tensioning film is adhered on the hole 3-2 of the top pressing plate 3, and an expansion extrusion layer 10 is arranged in the hole of the bottom plate;
thirdly, filling soil: then, arranging a water filtering layer 5 on the bottom plate 1, arranging a rigid layer 9 at the position of the water filtering layer 5 corresponding to the pile foundation, and then paving a bottom film (holes are also formed at the position of the bottom film on the pile model) on the water filtering layer 5; then laying soil in layers; after the soil filling is finished, soaking and standing the model foundation for a week to fully saturate the soil body;
fourthly, soil consolidation: the first loading system starts to operate, so that the top pressing plate keeps a preset stress on the soil body; consolidation was carried out under these conditions for 1 week; the control valve is always in an open state;
fifthly, pressing in the pile model: the second loading system starts to apply force to the pile model and pushes the pile model downwards until the pile model penetrates through the bottom plate 1;
sixth, test: and (5) carrying out static load test to obtain the relation of the pile side frictional resistance f-settlement s.
The second embodiment is mainly suitable for small-diameter piles and soil-squeezing piles.
In a third embodiment, in order to study the influence of the energy pile, on the basis of the first or second embodiment, a cold and hot circulating pipe is provided inside the pile model, and is communicated with an external circulating liquid temperature regulating system.
When studying the influence of the pile-soil temperature on the side friction resistance of the pile foundation, a temperature sensor and a pile side surface soil pressure gauge are arranged on the surface of the pile and in the soil body.
After the soil body is solidified and the pile model is arranged in the soil body, heating and cooling the temperature of the pile model according to a preset working condition, measuring the temperature of the pile-soil surface and the temperature field in the soil body, and simultaneously measuring the surface stress of the pile side;
after the working conditions are completed, a static load test is carried out, and the development rule of the side friction resistance of the pile model under different temperature cycles is obtained.
In the fourth embodiment, on the basis of the third embodiment, when the depth of the soil layer to be simulated is deep, as shown in fig. 11, the second vertical plate 2-2 may be bent inward (it is not possible to strictly satisfy K)0State) (a strain gauge is provided on the side of the second vertical plate 2-2 facing the first vertical plate to monitor its bending; when the second vertical plate 2-2 is bent as shown in fig. 11, the side of the second vertical plate 2-2 facing the first vertical plate is elongated);
therefore, circulating liquid is filled in a gap between the first vertical plate 2-1 and the second vertical plate 2-2, and a plurality of liquid filling ports are arranged in the circumferential direction of the circular connecting plate 4 and externally connected with a pressure pump;
the lateral confining pressure of the soil body is adjusted by adjusting the pressure of the circulating liquid between the first vertical plate 2-1 and the second vertical plate 2-2, so that the second vertical plate 2-2 is kept vertical.
It should be noted that the gap between the first vertical plate 2-1 and the second vertical plate 2-2 can also be inflated, and the second vertical plate 2-2 is kept in the vertical direction by the air pressure.
While the preferred embodiments of the present invention have been described in detail, it should be understood that various changes and modifications of the invention can be made by those skilled in the art after reading the above teachings of the invention. Such equivalents are intended to fall within the scope of the claims appended hereto.

Claims (9)

1. A pile-soil model testing machine for simulating soil body in-situ state comprises: the pile model comprises a bottom plate, a first vertical plate, a second vertical plate, a top pressing plate and a pile model;
the first vertical plate and the second vertical plate are cylindrical, the cross sections of the first vertical plate and the second vertical plate are both circular, the first vertical plate is arranged on the outer side of the second vertical plate, and a hole is formed between the first vertical plate and the second vertical plate;
it is characterized in that the preparation method is characterized in that,
the bottom plate includes: the bottom plate comprises a bottom plate main body, a first blocking platform and a second blocking platform, wherein the first blocking platform and the second blocking platform are cylindrical and are arranged on the upper side of the bottom plate main body; the first vertical plate is clamped between the first blocking platform and the second blocking platform; the second baffle is clamped between the gaps of the first vertical plate and the second vertical plate; the bottom plate is fixedly connected with the first vertical plate and the second vertical plate; the top ends of the first vertical plate and the second vertical plate are also provided with circular ring connecting plates;
the cross section of the top pressing plate is circular, and the size of the top pressing plate is matched with the opening of the second vertical plate;
a plurality of vertical grooves are formed in the inner side of the second vertical plate, and a plurality of bulges are formed in the outer side of the top pressing plate; the protrusion of the top pressing plate is inserted into the groove of the second vertical plate and can slide up and down;
a hole is formed in the central part of the top pressing plate;
further comprising: the first loading system is connected with the top pressing plate, a push rod of the first loading system is connected with the top of the top pressing plate, and a pressure sensor is arranged on the contact surface of the first loading system and the top pressing plate;
the central part of the top pressing plate is provided with a hole, the central part of the bottom plate is provided with a hole, and the sizes of the hole of the top pressing plate and the hole of the bottom plate are matched with the size of the pile model.
2. The pile-soil model testing machine for simulating in-situ soil mass states as claimed in claim 1, wherein the pile model is a hollow pile.
3. The pile-soil model testing machine for simulating in-situ states of soil mass according to claim 1, wherein a strain gauge is bonded to one side of the second vertical plate opposite to the first vertical plate, and a gap between the first vertical plate and the second vertical plate is inflated or filled with water so as to maintain pressure with the second vertical plate; and adjusting the air pressure or the water pressure according to the size of the strain gauge adhered to one side of the second vertical plate relative to the first vertical plate.
4. The pile-soil model testing machine for simulating in-situ state of soil mass according to claim 1, wherein a water filtering layer is laid on the upper surface of the bottom plate, a drain pipe is arranged inside the bottom plate main body so that water in the water filtering layer flows out from the drain pipe of the bottom plate main body, and a control valve is arranged outside the drain pipe; the drainage condition of the drainage pipe is controlled through the control valve, and therefore the soil body is simulated to be in a drainage state or a non-drainage state.
5. The pile-soil model testing machine for simulating soil in-situ conditions of claim 4, further comprising: the bottom membrane and the side membrane are arranged on the upper side of the water filtering layer, and the top membrane is arranged on the lower side of the top pressing plate; the soil body is enclosed among the bottom film, the side films and the top film, wherein the side films are arranged on the inner surface of the second vertical plate in advance.
6. The pile-soil model testing machine for simulating soil in-situ conditions of claim 5, further comprising: the pile model supporting device comprises a top supporting frame, a bottom plate and a pile model supporting device, wherein the bottom plate is supported on the top supporting frame; pile model strutting arrangement includes: the clamp is provided with a power mechanism at the lower side of the clamp; the power mechanism is fixed on the ground; and a tension sensor is arranged between the pile model supporting device and the pile model.
7. The pile-soil model testing machine for simulating in-situ states of soil mass as claimed in claim 5, wherein the second loading mechanism of the pile model is disposed at the upper part; a tensioning film is stuck at the opening of the top pressing plate so as to seal the opening; a rigid layer which is radially separated from the peripheral water filtering layer is arranged at the position of the water filtering layer relative to the hole of the bottom plate; the opening of the bottom plate is provided with an expansion extrusion layer, namely the expansion extrusion layer is plugged into the hole of the bottom plate.
8. The working method of the pile-soil model testing machine for simulating the in-situ state of the soil mass according to claim 6,
the method comprises the following steps:
firstly, a pile model passes through a hole of a top pressing plate and a hole of a bottom plate in advance, and then the bottom of the pile model is arranged on a pile model supporting device;
secondly, filling soil: then, arranging a water filtering layer on the bottom plate, and then paving a bottom film on the water filtering layer; then laying soil in layers;
after the soil filling is finished, soaking and standing the model foundation for a week;
thirdly, soil consolidation: the first loading system starts to operate, so that the top pressing plate keeps a preset stress on the soil body; consolidation was carried out under these conditions for 1 week; the control valve is always in an open state;
fourth, test: and (4) pulling down the pile model by using the pile model supporting device, and carrying out a static load test to obtain the relation of the pile side frictional resistance f-settlement s of the soil layer.
9. The working method of the pile-soil model testing machine for simulating the in-situ state of the soil body according to claim 7 is characterized by comprising the following steps:
firstly, determining the diameter of a second vertical plate according to the property of a soil body and the size of a pile model;
secondly, a tensioning film is adhered to the hole of the top pressing plate, and an expansion extrusion layer is arranged in the hole of the bottom plate; then arranging the bottom of the pile model on a pile model supporting device;
thirdly, filling soil: then, arranging a water filtering layer on the bottom plate, arranging a rigid layer at the position of the water filtering layer corresponding to the pile foundation, and then paving a bottom film on the water filtering layer; then laying soil in layers; after the soil filling is finished, soaking and standing the model foundation for a week to fully saturate the soil body;
fourthly, soil consolidation: the first loading system starts to operate, so that the top pressing plate keeps a preset stress on the soil body; consolidation was carried out under these conditions for 1 week; the control valve is always in an open state;
fifthly, pressing in the pile model: the second loading system starts to apply force to the pile model and pushes the pile model downwards until the pile model penetrates through the bottom plate;
sixth, test: and (5) carrying out static load test to obtain the relation of the pile side frictional resistance f-settlement s.
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