CN216999893U - Uplift pile model test device in any tension direction - Google Patents

Abstract

An uplift pile model test device in any tension direction comprises a model box, a loading mechanism, monitoring components, a foundation pit support and a pile foundation structure. The model box comprises a rigid frame (13), toughened glass (11), a steel plate (12) and a preset bolt; the loading mechanism comprises a supporting steel frame (21), a connecting steel sheet, a welding fixed pulley (23), a non-welding fixed pulley (24), a T-shaped bolt, a nut, a steel wire rope (27) and a bearing barrel (28); the monitoring component comprises a resistance strain gauge, a soil pressure cell and a displacement dial indicator; excavation supporting and pile foundation structure include supporting construction and simulation stake, and supporting construction comprises four PVC boards (31) and draw-in groove, and the simulation stake comprises pile body (33) and pile bolck lid. The device can realize the uplift test of the pile foundation in different tension directions.

Description

Uplift pile model test device in any tension direction

Technical Field

The utility model relates to an uplift pile model test device in any tension direction, and belongs to the technical field of geotechnical engineering.

Background

With the development of social economy, the requirements of the nation on the urban living standard are continuously improved, the longitudinal development of the urban construction field is greatly promoted, the influence of underground engineering construction is realized, and the foundation of the existing building structure is difficult to avoid the effect of uplift. Especially in most areas in south China, rainfall is abundant, the underground water level is high all the year round, the soil quality is poor, and when the buoyancy of underground water cannot be balanced by the load of an upper structure, the whole or part of the structure can be acted by upward force.

In order to prevent the tensile damage of a building (structure), the most widely applied measure is to arrange an uplift pile, and the action mechanism of the uplift pile is to effectively resist the axial tension applied to the structure by depending on the friction force between a pile body and a soil layer. The uplift bearing capacity of the uplift pile generally depends on the resistance of the pile side and surrounding rock soil or the design strength limit value of a pile body material, so that before the uplift pile is designed, the uplift pile is subjected to uplift checking calculation based on the interaction principle of the pile and soil under the action of uplift load, the influence rule of each influence factor on the uplift pile bearing capacity is revealed, and the uplift pile bearing capacity prediction method has important significance for structural design and accurate prediction of uplift performance.

Compared with the related research of the compressive bearing capacity of the pile foundation, the theoretical research in the field of uplift at present is relatively deficient, the numerical simulation lacks data basis, and the uplift performance of the uplift pile is usually detected through two modes, namely an indoor test and a field test. However, the field situation is generally complex, and if the uplift pile performance is analyzed and researched according to the field situation, the difficulty is high, the cost is high, the time consumption is long, and the universality is not achieved. Therefore, compared with a field test, the indoor test becomes a more convenient test means.

Disclosure of Invention

The utility model aims to provide an uplift pile model test device in any tension direction in order to efficiently test the stress displacement conditions of uplift piles and pile side soil under the action of tension forces at different angles in a foundation pit excavation environment, provide experimental data and basic parameters for uplift pile performance research and solve the problems of high cost, high cost and the like.

The technical scheme of the utility model is that the uplift pile model test device in any tension direction comprises a model box, a loading mechanism, monitoring components, a foundation pit support and a pile foundation structure; the foundation pit support and the pile foundation structure are arranged in the model box; the loading mechanism is arranged at the upper part of the model box, and the upper loading mechanism and the lower model box form an assembly structure and are fixed with the preset bolts at four corners of the model box through nuts; the monitoring components are arranged in a foundation pit support and pile foundation structure.

The model box is of a square frame structure and consists of a rigid frame, toughened glass and a steel plate; the rigid frame is a square steel structure frame, toughened glass is arranged on the periphery of the frame, and a steel plate is arranged at the bottom of the frame.

The loading mechanism comprises a supporting steel frame, a connecting steel sheet, a welding fixed pulley, a non-welding fixed pulley, a T-shaped bolt, a nut, a steel wire rope and a bearing barrel; the supporting steel frame consists of four vertical supporting steel frames, six horizontal supporting steel frames and six inclined supporting steel frames; the horizontal support steel frames are welded with the vertical support steel frames, three of the horizontal support steel frames are perpendicular to the stress loading direction, and the other three horizontal support steel frames are horizontal to the stress loading direction; wherein the third vertical horizontal supporting steel frame is positioned above the outer part of the model box, and the center of gravity and the center of the bearing barrel are on the same vertical line; the center of gravity of the second horizontal supporting steel frame and the center of the model box are on the same vertical line; one end of the inclined support steel frame is welded and fixed with the vertical support steel frame, and the other end of the inclined support steel frame is welded and fixed with the horizontal support steel frame; the welding fixed pulley and the non-welding fixed pulley are positioned on the same horizontal line, the welding fixed pulley is positioned at the center of the third vertical horizontal support steel frame, the non-welding fixed pulley freely moves along the second horizontal support steel frame, and the T-shaped bolt and the nut are utilized to realize fixation at the required position; one end of the steel wire rope is connected with the bearing barrel, the other end of the steel wire rope is provided with a hook, and the steel wire rope is connected with a circular ring of the simulated pile top through a welding fixed pulley and a non-welding connection fixed pulley; the bearing barrel is used for placing weights and weights.

A connecting steel sheet is welded on each of two sides of one end of the vertical supporting steel frame, a round hole is formed in each connecting steel sheet and used for being in butt joint with bolts at four top corners of the lower rigid frame, and then the loading mechanism can be fixed on the model box through nuts.

The foundation pit supporting and pile foundation structure comprises a supporting structure and a simulation pile; the supporting structure consists of four PVC plates and clamping grooves, and the four PVC plates are spliced into a foundation pit shape through the clamping grooves so as to simulate a diaphragm wall; the simulation pile consists of a hollow aluminum pipe pile body and a pile top cover. The middle part above the pile top cover is provided with a ring, and a wire guide opening is arranged nearby; the lower part is provided with a threaded cylindrical surface which is embedded with the thread in the top of the pile body.

The monitoring components comprise resistance strain gauges, soil pressure cells and displacement dial indicators; the resistance strain gauge, the soil pressure cell and the displacement dial indicator are respectively connected with the data acquisition unit through data lines; the resistance strain gauges are symmetrically distributed along different scales inside the pile body; the soil pressure box is buried in soil around the simulation pile; and the displacement dial indicators are uniformly arranged on the pile top cover.

Compared with the traditional uplift test device, the device has the advantages that the second non-welded fixed pulley at the position of the horizontal support steel frame can freely move along the steel frame in the horizontal direction, and can be fixed at any position through the T-shaped bolt and the nut, so that the uplift test of the pile foundation in different tension directions is realized; the supporting frame arranged on the upper part of the model box is used as a bearing body for applying the pulling force, and the supporting frame is fixed on the top of the model box by the nut and the preset bolt, so that the device can be freely disassembled, and the model box can be reused for other indoor model tests.

Drawings

FIG. 1 is a schematic structural diagram of a uplift pile model test device in any tension direction;

FIG. 2 is a schematic view of the mold box and loading mechanism assembly;

FIG. 3 is a schematic view of the non-welded crown block attachment of the present invention;

FIG. 4 is a schematic view of the support structure of the present invention;

FIG. 5 is a schematic view of a pile cap of the present invention;

FIG. 6 is a schematic view of the arrangement of monitoring elements;

in the figure, 1 is a mold box: 11 is toughened glass, 12 is a steel plate, 13 is a rigid frame, and 14 is a preset bolt; 2, a loading mechanism: the steel support frame 21 is a support steel frame, the steel support frame 22 is a connecting steel sheet, the steel support frame 23 is a welding fixed pulley, the steel support frame 24 is a non-welding fixed pulley, the steel support frame 25 is a T-shaped bolt, the steel support frame 26 is a nut, the steel wire rope 27 is a steel wire rope, and the steel support frame 28 is a bearing barrel; 3 is excavation supporting and pile foundation structure: 31 is a PVC plate, 32 is a clamping groove, 33 is a pile body, and 34 is a pile top cover; and 4, monitoring components: 41 is resistance strain gauge, 42 is soil pressure cell, and 43 is displacement dial gauge.

Detailed Description

The specific embodiments of the utility model are shown in the attached drawings.

As shown in fig. 1, the uplift pile model test device in any tension direction of the embodiment is composed of four parts, namely a model box 1 for placing test materials and equipment, a loading mechanism 2 for applying uplift force, a foundation pit supporting and pile foundation structure 3, and a monitoring component 4 for measuring various parameters in the test process. The upper loading mechanism 2 and the lower model box 1 are assembled structures and are fixed with the preset bolts at four corners of the model box through nuts; and the loading mechanism 2 is connected with the simulation pile through a steel wire rope.

The mold box 1 of the present embodiment is a frame structure, and includes a tempered glass 11, a steel plate 12, and a rigid frame 13. A rigid frame and a preset bolt 14; the model box frame structure is formed by welding cylindrical steel pipes with certain thickness, and provides support protection for the bottom surface and the side surface of the glass box body. The periphery of the frame is filled with transparent high-pressure-resistant toughened glass 11, and the bottom of the frame is provided with a steel plate 12 with a certain thickness. The four top corners of the frame are provided with two pre-bolts 14, respectively, for assembling the loading mechanism, as shown in fig. 2. In addition, all the rigid frames of the mold box are painted with rust-proof paint to prevent the steel from rusting. The toughened glass 11 also has certain thickness, and rigidity is higher and sealed good, and the transparent glass encloses the chamber and is favorable to clearly observing the atress destruction process of foundation ditch and pile foundation.

The loading mechanism 2 of the embodiment is composed of a supporting steel frame 21, a connecting steel sheet 22, a welding fixed pulley 23, a non-welding fixed pulley 24, a T-shaped bolt 25, a nut 26, a steel wire rope 27, a bearing barrel 28 and a heavy object.

The support steel frame 21 comprises four vertical support steel frames, six horizontal support steel frames and six inclined support steel frames. Two sides of one end of the vertical supporting steel frame are respectively welded with a connecting steel sheet 22, the connecting steel sheets 22 are provided with round holes for butt joint with bolts at four top corners of the lower rigid frame, and then the loading mechanism can be fixed on the model box through nuts, as shown in fig. 2. The horizontal support steel frames are welded with the vertical support steel frames, three of the horizontal support steel frames are vertical to the stress loading direction, and the other three horizontal to the stress loading direction; the third vertical horizontal supporting steel frame is positioned above the outer part of the model box, the gravity center and the center of the bearing barrel are on the same vertical line, and the second horizontal supporting steel frame is positioned on the same vertical line. One end of the inclined supporting steel frame is welded and fixed with the vertical supporting steel frame, and the other end of the inclined supporting steel frame is welded and fixed with the horizontal supporting steel frame, so that the overall stability of the stress loading mechanism is ensured.

The welded fixed pulley 23 and the non-welded fixed pulley 24 are on the same horizontal line, so that the wire rope 27 is also kept horizontal. The fixed pulley 23 is welded at the center of the third vertical horizontal supporting steel frame, the other non-welded fixed pulley 24 can freely move along the second horizontal supporting steel frame, and can be fixed at a required position by using a T-shaped bolt 25 and a nut 26, as shown in fig. 3, so that the tension test of the pile foundation at different angles is facilitated. One end of the steel wire rope 27 is connected with the bearing barrel 28, and the other end of the steel wire rope is provided with a hook and is connected with a circular ring of the simulation pile top through two fixed pulleys. The weight bearing barrel 28 is used for placing weights and other weights.

Foundation ditch support and pile foundation structure 3 includes supporting construction and simulation stake.

Since the test of this embodiment is performed under the excavation condition of the foundation pit, it is necessary to ensure that the foundation pit does not collapse, and therefore, a supporting structure, i.e., an underground continuous wall, is applied around the foundation pit. On the premise of considering cost and construction, the supporting structure selects four PVC plates 31 with certain thickness, and the PVC plates are mutually spliced into a foundation pit shape through the clamping grooves 32 to simulate the ground connection wall, as shown in FIG. 4. The simulation pile is composed of a hollow aluminum pipe pile body and a pile top cover, and the process of adhering the strain gauge is more convenient due to the combined structure. The surface of the shaft 33 may be provided with a smooth surface or a threaded surface. The middle part above the pile top cover 34 is provided with a circular ring for applying an upper pulling force, as shown in fig. 5; a wire guide port is arranged nearby, so that the data wire can be conveniently led out; the lower part is provided with a threaded cylindrical surface which is embedded with threads in the top of the pile body, so that the two parts form a whole.

The monitoring component 4 of the present embodiment includes a resistance strain gauge 41, a soil pressure cell 42, and a displacement dial indicator 43. The resistance strain gauge 41, the soil pressure cell 42 and the displacement dial indicator 43 are respectively connected with the data acquisition unit through data lines. The resistance strain gauges 41 are symmetrically arranged along different scales inside the pile body so as to obtain axial force and side grinding resistance of the uplift pile in real time; the soil pressure box 42 is buried in the soil around the simulation pile to obtain the change situation of the soil pressure at the side of the pile, as shown in fig. 6; the displacement dial indicators 43 are uniformly arranged on the pile top cover 34 to accurately monitor the pile top displacement.

The specific implementation steps of this embodiment are as follows:

(1) preparation of the test: before the test, a mark pen is used for marking model piles, embedding positions of all detection elements, excavation positions of foundation pits and the like in the model box 1, and a layer of medical Vaseline is coated on the inner wall of the model box 1 to reduce the boundary effect of the test. The round holes of the connecting steel sheets 22 of the loading mechanism 2 are aligned with the preset bolts 14 at the four top corners of the model box 1, and then are assembled through nuts 26, as shown in fig. 2.

(2) Filling a test soil body: according to the information of the actual field stratum, the test soil body is filled into the model box 1 in a layered mode through a rain falling method, the overall compactness of the soil layer is controlled through weighing and controlling the sand filling quality each time, and finally, a vibration compactor is used for carrying out vibration compaction on the soil layer.

(3) Installing a monitoring component: as shown in fig. 6, two rows of resistance strain gauges 41 are symmetrically arranged along the inside of the pile body 33, and the wires of the strain gauges are led out from the reserved outlet of the pile top cover 34 to prevent disturbance of the soil mass around the pile and are connected to the strain gauge measurement channel together with the wires of the soil pressure box 42. In order to obtain the displacement of the pile top better, the pile top cover 34 is divided into 4 parts in a circular average way, and a displacement dial indicator 43 is arranged at the center of each part.

(4) Burying supporting construction, pile foundation and monitoring component underground: the PVC sleeve is required to be arranged above the excavation surface of the pile body of the model pile, so that the pile surface is smooth, and the influence of the friction force between the unloaded soil body and the pile on the test is reduced when the foundation pit is excavated. When the test soil uniformly spread in the model box 1 reaches the bottom elevation of the foundation pit support and pile foundation structure 3, the support structure assembled by the PVC plates 31 and the clamping grooves 32 and the model pile composed of the pile body 33 and the pile top cover 34 are gently placed in the sand, the sand is continuously spread until the top of the foundation pit is level with the upper edge of the foundation pit, and then the model pile is stood for at least 24 hours to ensure the deformation stability of the soil. In the sand filling process, sand and soil are kept to be scattered into the box from the same elevation, so that the stress of the soil before and after the pile is equal; when the designed elevation of the soil pressure box 42 is reached, the soil pressure box 42 is lightly placed, and the lead wires are led out of the mold box 1.

(5) Excavation of a foundation pit: after the soil body is deformed and stabilized, the soil body in the foundation pit is gradually excavated, one side of the foundation pit is prevented from being excavated, the excavated surface is kept horizontal, then the model pile is uniformly stressed in the excavation process, and the pile body 33 is prevented from inclining. And standing for a period of time after the specified depth is reached, and recording the acquired data after the change value of the displacement dial indicator 43 within 20min is less than 0.01 mm.

(6) Pulling up the model pile: according to the test requirement, a model pile pulling resistance test under a required angle is carried out, firstly, the non-welding fixed pulley 24 is moved to a required position, an included angle between the steel wire rope 27 and the vertical direction reaches a model pile pulling angle specified by the test, the steel wire rope is fixed through a T-shaped bolt 25 and a nut 26, as shown in fig. 3, the steel wire rope 27 penetrates through the welding fixed pulley 23 and the non-welding fixed pulley 24 above the model box 1, the end with an iron hook is connected with a circular ring of a pile top cover 34, and the other end of the steel wire rope is connected with a bearing barrel 28. And then, applying an external pulling force by loading heavy objects step by step, wherein the external force acts on the model pile through the welding fixed pulley 23, the non-welding fixed pulley 24 and the steel wire rope 27. And reading every 10min after the deformation is stabilized every loading one stage until the model pile loses the bearing capacity. The termination condition principle should meet the technical specification for building pile foundation detection (JGJ 106-. The termination conditions of the test are as follows: if the pile foundation structure is damaged and pulled out, the test termination can be determined.

(7) And after the test is finished, removing the heavy object, unloading the loading mechanism 2, moving the foundation pit support and pile foundation structure 3 out of the test soil body, cleaning the soil body in the model box 1, and preparing the box body for other tests. Repeating the steps 1-6, replacing the pile body 33 with different roughness, then carrying out uplift pile tests with different surface roughness, and analyzing the influence rule of factors such as the roughness of the pile on the bearing capacity of the uplift pile.

Claims (7)

1. An uplift pile model test device in any tension direction is characterized by comprising a model box, a loading mechanism, a monitoring component, a foundation pit support and a pile foundation structure; the foundation pit support and pile foundation structure are arranged in the model box; the loading mechanism is arranged at the upper part of the model box, the upper loading mechanism and the lower model box form an assembly structure, and the assembly structure is fixed with the preset bolts at four corners of the model box through nuts; the monitoring components are arranged in a foundation pit support and pile foundation structure.

2. The uplift pile model test device in any tension direction as claimed in claim 1, wherein the model box is of a square frame structure and is composed of a rigid frame, tempered glass and a steel plate; the rigid frame is a square steel structure frame, toughened glass is arranged on the periphery of the frame, and a steel plate is arranged at the bottom of the frame.

3. The uplift pile model test device according to claim 1, wherein the loading mechanism comprises a supporting steel frame, a connecting steel sheet, a welding fixed pulley, a non-welding fixed pulley, a T-shaped bolt, a nut, a steel wire rope and a bearing barrel; the supporting steel frame consists of four vertical supporting steel frames, six horizontal supporting steel frames and six inclined supporting steel frames; the horizontal support steel frames are welded with the vertical support steel frames, three of the horizontal support steel frames are perpendicular to the stress loading direction, and the other three horizontal support steel frames are horizontal to the stress loading direction; wherein the third vertical horizontal supporting steel frame is positioned above the outside of the model box, and the center of gravity and the center of the bearing barrel are on the same vertical line; the center of gravity of the second horizontal supporting steel frame and the center of the model box are on the same vertical line; one end of the inclined support steel frame is welded and fixed with the vertical support steel frame, and the other end of the inclined support steel frame is welded and fixed with the horizontal support steel frame; the welding fixed pulley and the non-welding fixed pulley are positioned on the same horizontal line, the welding fixed pulley is positioned at the center of a third vertical horizontal supporting steel frame, the non-welding fixed pulley freely moves along a second horizontal supporting steel frame, and the non-welding fixed pulley is fixed at a required position by utilizing a T-shaped bolt and a nut; one end of the steel wire rope is connected with the bearing barrel, the other end of the steel wire rope is provided with a hook, and the steel wire rope is connected with a ring of the simulation pile top through a welding fixed pulley and a non-welding connection fixed pulley; the bearing barrel is used for placing weights and weights.

4. The apparatus of claim 1, wherein the excavation supporting and piling structure comprises a supporting structure and a dummy pile; the supporting structure consists of four PVC plates and clamping grooves, and the four PVC plates are spliced into a foundation pit shape through the clamping grooves so as to simulate a diaphragm wall; the simulation pile consists of a hollow aluminum pipe pile body and a pile top cover.

5. The uplift pile model test device in any tension direction as claimed in claim 1, wherein the monitoring components comprise a resistance strain gauge, a soil pressure cell and a displacement dial indicator; the resistance strain gauge, the soil pressure cell and the displacement dial indicator are respectively connected with the data acquisition unit through data lines; the resistance strain gauges are symmetrically distributed along different scales inside the pile body; the soil pressure box is buried in soil around the simulation pile; and the displacement dial indicators are uniformly arranged on the pile top cover.

6. The apparatus of claim 3, wherein a connecting steel plate is welded to each side of one end of the vertical support steel frame, the connecting steel plate is provided with a round hole for butt joint with bolts at four top corners of the lower rigid frame, and the loading mechanism is fixed to the mold box through nuts.

7. The uplift pile model test device in any tension direction as claimed in claim 4, wherein a ring is arranged in the middle of the upper part of the pile top cover, and a wire guide port is arranged nearby; the lower part is provided with a threaded cylindrical surface which is embedded with the thread in the top of the pile body.

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