CN111155568A

CN111155568A - Pile foundation installation and load-bearing simulation test device and method capable of restoring ocean deep water pressure field and ground stress field

Info

Publication number: CN111155568A
Application number: CN201911418030.3A
Authority: CN
Inventors: 周文杰; 李佳豪; 国振; 李玲玲; 芮圣洁; 李雨杰
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2019-12-31
Filing date: 2019-12-31
Publication date: 2020-05-15

Abstract

The invention discloses a pile foundation installation and load-bearing simulation test device capable of reducing an ocean deep water pressure field and a ground stress field, which mainly comprises: outer barrel, steel soil, coil, model pile, step motor, etc. According to the invention, a supergravity environment is provided for the steel soil through the uniform magnetic field formed by the coils wound at the two ends of the outer barrel, the real stress state of the soil body in the reduced scale model test is restored, high-pressure air is injected through the pressurizing hole to simulate the high-pressure condition in the ocean deep water environment, and the upper cover plate of the outer barrel and the barrel body of the outer barrel are fixed through the buckle to realize strict sealing. The test device provided by the invention is simple in equipment, convenient to operate and accurate in result. The invention solves the problem that the high-pressure environment under the marine deepwater environment cannot be simulated by the corresponding test instrument at present and the soil pressure cannot be restored due to the scale effect of the model, and has the advantages of high test efficiency, flexible operation and outstanding advantages.

Description

Pile foundation installation and load-bearing simulation test device and method capable of restoring ocean deep water pressure field and ground stress field

Technical Field

The invention belongs to the technical field of civil engineering tests, and relates to a pile foundation installation load simulation test device and method capable of restoring an ocean deep water pressure field and a ground stress field.

Background

Since the twenty-first century, many countries in the world have increasingly conducted exploration and development of marine resources. Due to the severe marine environment and the continuous action of cyclic loads such as wind, wave and the like, a plurality of technical problems occur in the construction process of marine structures, such as the cyclic action problem of marine pile foundations and deep sea seabed soil bodies, and experimental research is the most reliable technical means at present. It is very difficult to develop the test of the structure and the soil body in the deep sea environment and restore the real stress state of the high-pressure environment and the seabed soil body under the deep sea condition. At present, the real stress state of the soil body can be restored in the model test only in a centrifuge test mode, and the centrifuge applies centrifugal force to the soil body through high-speed rotation to realize the hypergravity environment of the soil body, so that the soil body acting force of the scale model is consistent with the actual working condition. However, the centrifuge test is expensive, the operation difficulty is high, and it is difficult to realize a deep water high pressure environment at the same time.

Disclosure of Invention

The invention provides a pile foundation installation and load simulation test device capable of reducing an ocean deep water pressure field and a ground stress field, aiming at the simulation problem of deep sea high pressure environment in an indoor test process and under the condition that the prior art has many defects and cannot simulate actual working conditions. The invention provides the hypergravity environment of the soil body by the constant vertical force of the steel soil under the action of the uniform magnetic field, restores the actual stress state of the soil body, and simulates high-pressure seawater in the deep sea environment by high-pressure air. The method has the advantages of large simulation depth range, simple test flow and the like, and solves the problems that a test instrument cannot simulate the marine deep water environment and restore the true ground stress in the scientific research process.

The invention adopts the following technical scheme:

a pile foundation installation and load bearing simulation test device capable of restoring an ocean deep water pressure field and a ground stress field comprises an outer barrel, two coils arranged in the outer barrel, a model pile, a first stepping motor and a second stepping motor; the outer barrel is filled with steel soil; one coil is positioned below the steel soil, and the other coil is positioned above the steel soil; the inner wall of the outer barrel is provided with a crossed steel frame; the first stepping motor is arranged on the crossed steel frame and used for pressing the model pile into steel soil; and the second stepping motor is arranged on the side wall of the outer barrel and is used for applying horizontal load to the model pile.

In the above technical solution, further, the two coils are respectively fixed at the upper and lower parts of the outer tub, the diameter and the distance between the two coils are the same as the outer diameter of the outer tub, and the two coils are electrified to form a uniform magnetic field; the steel soil is subjected to vertical downward field acting force under the action of the uniform magnetic field, so that the hypergravity environment of the soil body is realized, and the real stress state of the soil body corresponding to the reduced scale model is restored.

Furthermore, the outer barrel is made of aluminum alloy and is not influenced by magnetic force.

Furthermore, the side surface of the outer barrel is provided with a pressurizing hole and a toughened glass window.

Furthermore, a loading rod is arranged at the end part of the second stepping motor, a hoop is arranged at the other end of the loading rod, and the model pile penetrates through the hoop to be connected with the loading rod.

The invention also provides a test method of the pile foundation installation and load simulation test device capable of restoring the ocean deep water pressure field and the ground stress field, which is realized based on the test device capable of simulating the installation process of the suction bucket in the ocean deep water environment, and the specific test method comprises the following steps: vertically placing a model pile on the surface of the steel soil, adjusting the position of the model pile to enable the axis of the model pile and the axis of the stepping motor to be on the same straight line, and covering an upper cover plate; electrifying the coil to enable the strength of the uniform magnetic field to reach a design value, realizing a supergravity environment, and determining the basis as the reduction ratio of the model pile; inflating and pressurizing to a design pressure through the pressurizing hole, and determining a pressure value according to the seawater depth to be simulated; turning on a first stepping motor to press the model pile into the steel soil until the design depth is reached; and then the second stepping motor is started to apply horizontal load to the model pile penetrating through the hoop through the loading rod.

The invention principle of the invention is as follows:

according to the invention, a supergravity environment is provided for the steel soil through the uniform magnetic field formed by the coils wound at the two ends of the outer barrel, the real stress state of the soil body in the reduced scale model test is restored, high-pressure air is injected through the pressurizing hole to simulate the high-pressure condition in the ocean deep water environment, and the upper cover plate of the outer barrel and the barrel body of the outer barrel are fixed through the buckle to realize strict sealing.

The beneficial effects of the invention are as follows:

the pile foundation installation and load simulation test device capable of restoring the ocean deep water pressure field and the ground stress field is simple in structure, and the supergravity is simulated by applying uniform vertical field force to steel soil through electromagnetic force; high water pressure in a marine deep water environment is simulated by high-pressure gas.

The method of the invention can realize that: the simulated seawater depth and the supergravity can be adjusted at will; the test flow is simple and efficient.

Drawings

FIG. 1 is a schematic view of a test apparatus according to the present invention;

FIG. 2 is a top view of the test device of the present invention;

FIG. 3 is a schematic view of a stepper motor position;

FIG. 4 is a schematic illustration of the piling process of the test rig of the present invention;

FIG. 5 is a schematic view of the horizontal loading of the model pile of the testing device of the present invention

The device comprises a shell, an outer barrel, a model pile, a stepping motor I, a stepping motor II.

Detailed Description

The pile foundation installation and load bearing simulation test device capable of restoring the ocean deep water pressure field and the ground stress field comprises an outer barrel 1, steel soil 2, a coil 3, a model pile 4, a stepping motor I5 and the like. The two ends of the outer barrel 1 are provided with coils 3, the diameter of each coil 3 is the same as that of the outer barrel 1, the distance between the two coils 3 is the same as that of the coil 3, after the coils 3 are electrified, a uniform magnetic field can be formed in the middle of the outer barrel 1, and the size of the uniform magnetic field can be adjusted through the current of the coils 3; the outer barrel 1 is made of aluminum alloy, and a pressurizing hole 6 and a toughened glass window 13 are arranged on the side surface of the outer barrel 1; the steel soil 2 is iron powder; the stepping motor I5 is arranged on a crossed steel frame 14 welded on the inner wall of the outer barrel 1; the upper cover plate 7 is connected with the outer barrel 1 by a buckle, and a rubber strip seal is arranged at the contact part; the second stepping motor 10 is welded on the inner wall of the outer barrel 1, a loading rod 11 is arranged at the other end of the second stepping motor 10, and the model pile 4 penetrates through the hoop 12 to be connected with the loading rod 11. The specific test flow and the operation steps are as follows:

step 1: slightly placing the model pile on the steel soil, penetrating the model pile into the soil body by a certain depth by means of the dead weight of the model pile, adjusting the position of the model pile to enable the axis of the model pile and the axis of the stepping motor to be on the same straight line, covering an upper cover plate and sealing tightly;

step 2: electrifying the electromagnet, adjusting the strength of the uniform magnetic field to a design value, and inflating through the pressurizing hole to enable the air pressure to reach the design value;

and step 3: pressing the model pile into the steel soil through the first stepping motor to enable the model pile to penetrate into the steel soil to a set depth;

and 4, step 4: and applying horizontal load to the model piles through the stepping motor.

Claims

1. A pile foundation installation and load bearing simulation test device capable of restoring an ocean deep water pressure field and a ground stress field is characterized by comprising an outer barrel (1), two coils (3) arranged in the outer barrel (1), a model pile (4), a first stepping motor (5) and a second stepping motor (10); the outer barrel (1) is internally provided with steel soil (2); one coil (3) is positioned below the steel soil (2), and the other coil (3) is positioned above the steel soil (3); the inner wall of the outer barrel (1) is provided with a crossed steel frame (14); the first stepping motor (5) is arranged on the crossed steel frame (14) and used for pressing the model pile (4) into the steel soil (2); the second stepping motor (10) is arranged on the side wall of the outer barrel (1) and is used for applying horizontal load to the model pile (4).

2. The pile foundation installation and load bearing simulation test device capable of reducing the ocean deep water pressure field and the ground stress field according to claim 1, wherein the two coils (3) are respectively fixed at the upper part and the lower part of the outer barrel (1), the diameter of the two coils and the distance between the two coils are the same as the outer diameter of the outer barrel (1), and the two coils (3) are electrified to form a uniform magnetic field; the steel soil (2) is subjected to vertical downward field acting force under the action of the uniform magnetic field, so that the hypergravity environment of the soil body is realized, and the real stress state of the soil body corresponding to the reduced scale model is restored.

3. The pile foundation installation and load bearing simulation test device for the reducible ocean deep water pressure field and the ground stress field according to claim 1, wherein the outer barrel (1) is made of aluminum alloy and is not affected by magnetic force.

4. The pile foundation installation and load bearing simulation test device capable of reducing the ocean deep water pressure field and the ground stress field according to claim 1, wherein a pressurizing hole (6) and a toughened glass window (13) are arranged on the side surface of the outer barrel (1).

5. The pile foundation installation and load bearing simulation test device capable of reducing the ocean deep water pressure field and the ground stress field according to claim 1, wherein a loading rod (11) is arranged at the end part of the second stepping motor (10), a hoop (12) is arranged at the other end of the loading rod (11), and the model pile (4) penetrates through the hoop (12) to be connected with the loading rod (11).

6. A pile foundation installation and load bearing simulation test method capable of reducing an ocean deep water pressure field and an earth stress field is characterized by being realized based on the pile foundation installation and load bearing simulation test device capable of reducing the ocean deep water pressure field and the earth stress field according to any one of claims 1 to 4, and the specific test method is as follows: vertically placing the model pile (4) on the surface of the steel soil (2), adjusting the position of the model pile (4), enabling the axis of the model pile (4) and the axis of the stepping motor I (5) to be on the same straight line, and covering an upper cover plate (7); electrifying the coil (3) to enable the strength of the uniform magnetic field to reach a design value, realizing a supergravity environment, and determining the basis as the reduction ratio of the model pile; inflating and pressurizing to a design pressure through the pressurizing hole (10), and determining a pressure value according to the seawater depth to be simulated; turning on a first stepping motor (5) to press the model pile (4) into the steel soil (2) until the design depth is reached; and then, the second stepping motor (10) is started to apply horizontal load to the model pile (4) through the loading rod (11).