Non-contact test device and test method for flow of saturated zero-stress soil around structures

Abstract

The present invention discloses a non-contact test device and test method for the flow of saturated zero-stress soil around a structure. The test device includes: a transparent organic glass box and its sample loading accessories, an electromagnetic generator, a magnetic drag tube (plate), a guide rod and its support frame, an electromagnetic sensor, and a camera device. The beneficial effects of the present invention are: using a test device made of magnetic materials, an external electromagnetic loading device and an electromagnetic sensor, the structure is caused to produce relative motion and relevant data is measured in a non-contact manner, and the drag plate test is used to reveal the relevant characteristics of dynamic soil pressure and viscous shear force; the force of the drag tube (plate) is back-calculated through the magnetic field strength, so as to obtain the elastic modulus characterizing the solid characteristics of the soil and the apparent viscosity characterizing the fluid characteristics of the soil under different effective stress states.

Description

Technical Field

[0001] The invention belongs to the technical field of geotechnical earthquake engineering, and particularly relates to a non-contact testing device and a testing method for the flow of saturated zero-stress soil around a structure. Background Art

[0002] Since the 1964 Niigata earthquake in Japan and the Alaska earthquake in the United States, the liquefaction phenomenon has received increasing attention from the academic and engineering communities, and its occurrence mechanism and derived diseases have been gradually recognized. Liquefaction is one of the important causes of earthquake damage to sites. About 50% of foundation failures caused by earthquakes are caused by liquefaction. The Soil Dynamics Committee of the Geotechnical Engineering Division of the American Society of Civil Engineering defines liquefaction as: the behavior and process of any substance turning into liquid.

[0003] The zero effective stress state of part of the foundation soil at the epicenter and after the earthquake and the zero effective stress state of the liquefied foundation soil, the relative displacement of the soil and the pile foundation under these foundation damage states, and the mechanical response mechanism between the soil and the pile foundation have always been the focus and difficulty of seismic research in geotechnical earthquake engineering.

[0004] After literature research, it is found that the research on the seismic damage mechanism of liquefied foundation in the existing technology mainly focuses on the pile-soil interaction direction of the liquefied site, and its experimental limitations are specifically manifested in the following four points.

[0005] (1) The overall stress analysis of the pile-soil interaction under low (zero) effective stress state was performed, but the occurrence mechanism and composition of its mechanical response were not further studied.

[0006] (2) Passive measurement of the relative displacement of piles and soil in the low (zero) effective stress state did not achieve controllable operation of the relative displacement of piles and soil in this state, and no further quantitative analysis of the flow effect of the soil in this state was performed to study its changing law.

[0007] (3) The presence of wired sensors and transmission equipment in traditional tests will have a certain impact on the test results.

[0008] (4) The visualization of the test equipment and specimens is low. Summary of the invention

[0009] The purpose of the present invention is to make up for the limitations of traditional test schemes, overcome the errors caused by contact measurement and transmission on the test results, and propose a non-contact test device and test method for the flow of saturated zero-stress soil around a structure.

[0010] The technical solution of the present invention is as follows:

[0011] A non-contact testing device for the flow of saturated zero-stress soil around a structure, comprising: a transparent organic glass box, a sample loading accessory;

[0012] The sample loading accessory contains a sodium chloride solution, and the sample loading accessory is connected to the transparent organic glass box through a connecting pipe, and a valve is arranged on the connecting pipe;

[0013] A towing tube or towing plate, a guide rod support frame, and a plurality of parallel guide rods are arranged in a transparent organic glass box; the guide rod support frame is arranged at the bottom of the transparent organic glass box, and the guide rod is fixedly arranged on the guide rod support frame; a towing tube or towing plate is also placed on the guide rod, and the towing tube or towing plate can move along the guide rod;

[0014] The transparent organic glass box is also filled with plastic sand, and the height of the plastic sand is higher than the height of the drag tube or the drag plate.

[0015] A further design also includes: a motion control device, which controls the drag tube or the drag plate to move along the guide rod.

[0016] In a further design, the bottom height of the sample loading accessory is higher than the top height of the transparent organic glass box.

[0017] A further design also includes: an electromagnetic generator, the drag tube or the drag plate is made of magnetic material, and the electromagnetic generator generates a magnetic field when energized. Under the action of the magnetic field, the drag tube or the drag plate can move along the guide rod.

[0018] A further design also includes: a camera device, which is used to collect the test process.

[0019] A further design also includes: multiple electromagnetic sensors, which are used to obtain the measured intensity of the magnetic field distribution at the test site.

[0020] The non-contact test method for the flow of saturated zero-stress soil around a structure comprises the following steps:

[0021] (1) Screen plastic sand and prepare soil fixed particle samples according to the gradation curve required by the test soil;

[0022] (2) adjusting the concentration of sodium chloride solution and mixing the selected plastic sand to prepare a suspended particle soil sample to simulate the zero effective stress state of the soil;

[0023] (3) Fix the guide rod support frame on the transparent organic glass box, and fix the guide rod on the support frame. The guide rod is distributed parallel to the observation surface, and it is confirmed that the support frame and the guide rod are arranged stably;

[0024] (4) Place the vertical observation surface of the magnetic drag tube or magnetic carriage at the predetermined starting position on the guide rod, and confirm that the magnetic drag tube or magnetic carriage, support frame and guide rod are arranged stably;

[0025] (5) Confirm that the valve at the connection between the transparent organic glass box and the sample loading accessory is in the closed state, add an appropriate amount of test sample to the sample loading accessory, and slowly open the valve. During the loading process, pay attention to the sample flow rate and adjust the valve to ensure that the upper surface of the sample in the transparent organic glass box rises steadily and horizontally. When the upper surface of the sample in the accessory is close to the upper surface of the sample in the box, close the valve at the connection;

[0026] (6) Repeat step (5) until the upper surface of the sample in the transparent plexiglass box reaches the required height for the test, and confirm that there is still sufficient sodium chloride solution in the sample loading attachment;

[0027] (7) Preliminarily determine the position of the electromagnetic generator according to the instrument power, and arrange the corresponding number of electromagnetic sensors 4 according to the accuracy required by the test to obtain the measured intensity of the magnetic field distribution at the test site;

[0028] (8) Arrange the camera equipment, confirm that the equipment has clear imaging, and ensure that the collected images are effective and usable;

[0029] (9) Turn on the electromagnetic generator, adjust the output power, ensure that the magnetic drag tube or magnetic drag plate moves slowly and evenly to the specified test position, and turn off the electromagnetic generator.

[0030] The beneficial effects of this application are:

[0031] 1) A transparent organic glass box 1 is used. In the test, the zero effective stress soil is simulated by plastic sand 8 (plastic sand 8 is selected with a gradation curve close to that of standard sand) and sodium chloride solution 7. The glass box and the soil have good light transmission properties, ensuring the visualization of the entire test process.

[0032] 2) A loading accessory 11 for adding test samples is attached to the transparent organic glass box. The loading accessory 11 needs to be placed higher than the final height of the sample in the box. There is an opening at the bottom of the box to connect with the accessory. A valve 9 is provided at the connection to control the loading progress. The concentration of the sodium chloride solution 7 is adjusted according to the test requirements to make the plastic sand 8 in a suspended state to simulate the zero effective stress state of the soil during liquefaction.

[0033] 3) The magnetic drag tube 10 (or magnetic drag plate 3) is made of magnetic material and moves under magnetic traction in the magnetic field, thereby simulating the relative displacement and mechanical response between the pile and the soil under the zero effective stress state. The test uses an electromagnetic generator 2 with adjustable output power as the magnetic field source to output the required stable uniform magnetic field.

[0034] 4) The tube drag test simulates the overall state of the interaction between the pile and the soil; in the plate drag test, the plate width of the magnetic plate 3 is selected to be the equivalent width of the diameter of the magnetic tube 10. When the plate surface of the magnetic plate 3 is perpendicular to the direction of the mutual movement of the pile and the soil, the simple lateral dynamic earth pressure between the pile and the soil under ideal conditions is simulated. When the plate surface of the plate 3 is parallel to the direction of the mutual movement of the pile and the soil, the simple viscous shear force between the pile and the soil under ideal conditions is simulated. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be further described in detail below in conjunction with the embodiments in the accompanying drawings, but this does not constitute any limitation to the present invention.

[0036] Figure 1 It is a schematic diagram of the test device of the present invention.

[0037] Figure 2 Schematic diagram of the test principle of the device of the present invention.

[0038] Figure 3 Schematic diagram of the simulation test of pile-soil interaction under zero effective stress state of soil.

[0039] Figure 4 Schematic diagram of the simulation test of simple viscous shear force between pile and soil under ideal conditions.

[0040] Figure 5 Schematic diagram of the simulation test of simple lateral dynamic earth pressure between pile and soil under ideal conditions.

[0041] The following are the descriptions of the reference numerals:

[0042] 1. Transparent plexiglass box; 2. Electromagnetic generator; 3. Magnetic drag plate; 4. Electromagnetic sensor; 5. Guide rod support frame; 6. Guide rod; 7. Sodium chloride solution; 8. Plastic sand; 9. Valve; 10. Magnetic drag tube; 11. Sample loading accessories; 12. Camera device. DETAILED DESCRIPTION

[0043] Embodiment 1, as Figures 1 to 5 As shown, a non-contact testing device for the flow of saturated zero-stress soil around a structure comprises: a transparent organic glass box 1, a sample loading accessory 11;

[0044] A sodium chloride solution 7 is contained in the sample loading attachment 11, and the bottom of the sample loading attachment 11 is connected to the bottom of the transparent organic glass box 1 through a connecting pipe, and a valve 9 is provided on the connecting pipe to control the opening and closing of the connecting pipe;

[0045] The transparent organic glass box 1 is provided with: a magnetic drag tube 10 or a magnetic drag plate 3, a guide rod support frame 5, and a plurality of parallel guide rods 6; the guide rod support frame 5 is arranged at the bottom of the transparent organic glass box 1, and the guide rods 6 are fixedly arranged on the guide rod support frame 5; the magnetic drag tube 10 or the magnetic drag plate 3 is also placed on the guide rod 6, and the magnetic drag tube 10 or the magnetic drag plate 3 can move along the guide rod 6;

[0046] The transparent organic glass box 1 is also filled with: plastic sand 8, the height of the plastic sand 8 is higher than the height of the magnetic drag tube 10 or the magnetic drag plate 3;

[0047] The bottom height of the sample loading accessory 11 is higher than the top height of the transparent organic glass box 1 .

[0048] The non-contact testing device for the flow of saturated zero-stress soil around a structure also includes an electromagnetic generator 2, which generates a magnetic field. The magnetic drag tube 10 or the magnetic drag plate 3 can move along the guide rod 6 under the action of the magnetic field.

[0049] It also includes: a camera device; and collecting test process.

[0050] It also includes: a plurality of electromagnetic sensors 4, which are used to obtain the measured intensity of the magnetic field distribution at the test site.

[0051] The equipment developed in Example 1 uses a test device made of magnetic materials, an external electromagnetic loading device and an electromagnetic sensor to make the structure produce relative movement and measure relevant data in a non-contact manner, thereby avoiding the interference of the wired transmission, measuring equipment and other devices in conventional tests on the test results; plastic sand and a solution with the same refractive index are configured into a visual sample with zero effective stress, and combined with the transparent performance of the organic glass box material, the visual observation and measurement of the entire test process are realized; a saturated suspended sand drag tube test is used to simulate the mechanical effect of the soil on the pile under the zero effective stress state; a drag plate test is used to reveal the relevant characteristics of the dynamic earth pressure and the viscous shear force; the drag tube (plate) force is inversely calculated by the magnetic field strength, thereby obtaining the elastic modulus characterizing the solid properties of the soil and the apparent viscosity characterizing the fluid properties of the soil under different effective stress states.

[0052] The present invention also relates to a test method for testing the flow effect of soil under a zero effective stress state, and the main technical steps include:

[0053] (1) Screening plastic sand 8, and configuring a soil fixed particle sample according to the gradation curve required by the test soil;

[0054] (2) adjusting the concentration of the sodium chloride solution 7 and mixing the selected plastic sand 8 to prepare a suspended particle soil sample to simulate the zero effective stress state of the soil;

[0055] (3) The guide rod support frame 5 is fixedly set on the transparent organic glass box 1, and the guide rod 6 is fixedly placed on the support frame 5. The guide rod 6 is distributed parallel to the observation surface, and it is confirmed that the support frame 5 and the guide rod 6 are arranged stably;

[0056] (4) Place the magnetic drag tube 10 (or magnetic drag plate 3) vertically on the observation plane at a predetermined starting position on the guide rod 6, and confirm that the magnetic drag tube 10 (or magnetic drag plate 3), the support frame 5 and the guide rod 6 are arranged stably;

[0057] (5) Confirm that the valve 9 at the connection between the transparent organic glass box 1 and the sample loading attachment 11 is in the closed state, add an appropriate amount of test sample to the sample loading attachment, slowly open the valve 9, pay attention to observe the sample flow rate during the loading process and adjust the valve 9 to ensure that the upper surface of the sample in the transparent organic glass box 1 rises steadily and horizontally. When the upper surface of the sample in the attachment is close to the upper surface of the sample in the box, close the valve 9 at the connection;

[0058] (6) Repeat step (5) until the upper surface of the sample in the transparent organic glass box 1 reaches the required height for the test, and confirm that there is still a sufficient amount of sample in the sample loading attachment 11;

[0059] (7) Preliminarily determine the position of the electromagnetic generator 2 according to the instrument power, and arrange the corresponding number of electromagnetic sensors 4 according to the accuracy required by the test to obtain the measured intensity of the magnetic field distribution at the test site;

[0060] (8) Arrange the camera equipment 12, confirm that the equipment has clear imaging, and ensure that the captured images are valid and usable;

[0061] (9) Turn on the electromagnetic generator 2, adjust the output power, ensure that the magnetic drag tube 10 (or the magnetic drag plate 3) moves slowly and evenly to the specified test position, and turn off the electromagnetic generator 2;

[0062] According to the actual measured value of the electromagnetic sensor 4, the output power correction coefficient of the electromagnetic generator 4 is determined, and according to the moving speed of the magnetic drag tube 10 (or the magnetic drag plate 3), the position of the electromagnetic generator 2 and the electromagnetic sensor 4 is readjusted;

[0063] Repeat steps (1) to (9) to complete the experiment (i.e., complete multiple groups of experiments).

[0064] The above embodiments are preferred implementation modes of the present invention and are only used to facilitate the description of the present invention. They are not intended to limit the present invention in any form. Any person with ordinary knowledge in the relevant technical field, if they do not depart from the scope of the technical features of the present invention, can make equivalent embodiments by partial changes or modifications to the technical contents disclosed in the present invention, and they still fall within the scope of the technical features of the present invention without departing from the technical features of the present invention.

Claims

1. A non-contact test device for the flow of saturated zero-stress soil around a structure, characterized in that: include: Transparent plexiglass box, sample loading accessories, electromagnetic generator, and multiple electromagnetic sensors; The sample loading accessory contains a sodium chloride solution, and the sample loading accessory is connected to the transparent organic glass box through a connecting pipe, and a valve is arranged on the connecting pipe; A towing tube or towing plate, a guide rod support frame, and a plurality of parallel guide rods are arranged in a transparent organic glass box; the guide rod support frame is arranged at the bottom of the transparent organic glass box, and the guide rod is fixedly arranged on the guide rod support frame; a towing tube or towing plate is also placed on the guide rod, and the towing tube or towing plate can move along the guide rod; The transparent organic glass box is also filled with: plastic sand, the height of the plastic sand is higher than the height of the drag tube or the drag plate; The drag tube or drag plate is made of magnetic material. When the electromagnetic generator is powered on, a magnetic field is generated. Under the action of the magnetic field, the drag tube or drag plate can move along the guide rod; Electromagnetic sensors are used to obtain the measured intensity of the magnetic field distribution at the test site.

2. A non-contact testing device for the flow of saturated zero-stress soil around a structure according to claim 1, characterized in that: Also includes: The motion control device controls the drag tube or the drag plate to move along the guide rod.

3. A non-contact testing device for the flow of saturated zero-stress soil around a structure according to claim 1, characterized in that: The bottom height of the sample loading accessory is higher than the top height of the transparent organic glass box.

4. The non-contact testing device for the flow of saturated zero-stress soil around a structure according to claim 1, characterized in that: Also includes: Camera device: The camera device is used to capture the test process.

5. A non-contact test method for the flow of saturated zero-stress soil around a structure, characterized in that the test is carried out using the non-contact test device for the flow of saturated zero-stress soil around a structure as claimed in claim 1, comprising the following steps: (1) Screen plastic sand and prepare soil fixed particle samples according to the gradation curve required by the test soil; (2) Adjust the concentration of sodium chloride solution and mix the selected plastic sand to make a suspended particle soil sample to simulate the zero effective stress state of the soil; (3) Fix the guide rod support frame on the transparent plexiglass box, and fix the guide rods on the support frame. The guide rods are distributed parallel to the observation surface, and make sure that the support frame and guide rods are arranged stably; (4) Place the vertical observation surface of the magnetic drag tube or magnetic drag plate at the predetermined starting position on the guide rod, and confirm that the magnetic drag tube or magnetic drag plate, support frame and guide rod are arranged stably; (5) Confirm that the valve at the connection between the transparent organic glass box and the sample loading accessory is in the closed state, add an appropriate amount of test sample to the sample loading accessory, slowly open the valve, pay attention to the sample flow rate during the loading process and adjust the valve to ensure that the upper surface of the sample in the transparent organic glass box rises steadily and horizontally. When the upper surface of the sample in the accessory is close to the upper surface of the sample in the box, close the valve at the connection; (6) Repeat step (5) until the upper surface of the sample in the transparent plexiglass box reaches the required height for the test, and confirm that there is still sufficient sodium chloride solution in the sample loading attachment; (7) Preliminarily determine the location of the electromagnetic generator based on the instrument power, and arrange the corresponding number of electromagnetic sensors (4) according to the accuracy required by the test to obtain the measured intensity of the magnetic field distribution at the test site; (8) Arrange the camera equipment, confirm that the equipment images are clear, and ensure that the collected images are effective and usable; (9) Turn on the electromagnetic generator, adjust the output power, ensure that the magnetic drag tube or magnetic drag plate moves slowly and evenly to the specified test position, and turn off the electromagnetic generator.

6. The non-contact test method for flow of saturated zero-stress soil around a structure according to claim 5, characterized in that: Step (9) also includes: readjusting the positions of the electromagnetic generator and the electromagnetic sensor according to the moving speed of the magnetic drag tube or the magnetic drag plate, and performing the test again according to steps (1) to (9).

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