Apparatus and method for evaluating cohesion within a soil mass

Abstract

The application discloses a device and a method for evaluating the cohesion force inside soil, and the device comprises a power component and a detection component, the power component comprises a base, a motor is installed on the base, the output shaft of the motor is fixedly connected with one end of a transmission vertical rod, the other end of the transmission vertical rod is fixedly connected with a plurality of horizontal rods, and the detection component is installed on each horizontal rod; the detection component comprises an experimental platform, a soil sample containing barrel is installed on the experimental platform, a plurality of circular holes are formed in the wall surface of the soil sample containing barrel, a hydraulic oil cylinder is arranged at the upper portion of the soil sample containing barrel, and a gravity sensor is arranged at the lower portion of the soil sample containing barrel; the device can preliminarily estimate the size of the cohesion force inside the soil sample according to the mass loss of the soil sample after simple centrifugal rotation, comprehensively research the stress conditions of the soil sample under different external conditions, and realize quantitative description of the cohesion force value.

Description

Technical Field

[0001] This invention relates to the field of soil testing technology, specifically to a device and method for assessing the internal cohesion of soil. Background Technology

[0002] With rapid economic development, more and more underground tunnel construction projects are choosing to use tunnel boring machines (TBMs) to quickly and safely construct the main tunnel structure. In some areas with poor soil conditions, the excavated soil can easily form large mud cakes at the cutterhead of the TBM, significantly impacting construction progress. Whether the internal cohesion of the mud cake can withstand the stress changes within the excavation chamber is a crucial condition for determining whether the mud cake will continue to develop. As construction progresses, newly generated excavated soil will re-attach to the existing mud cake. If the mud cake has high cohesion, it will form an even larger mud cake, and vice versa. Therefore, an experimental device and method are needed to quickly assess the internal cohesion of the soil.

[0003] The existing methods for assessing soil cohesion have the following shortcomings: 1. Existing calculation methods all consider the cohesion of soil under natural conditions, without uniformly considering the influence of internal pressure of the excavation chamber, soil moisture content, and soil type on cohesion; 2. Existing testing methods need to be carried out in the laboratory, and there is no simple, fast, and efficient assessment device or method suitable for construction sites. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a device and method for evaluating the cohesion within soil. By measuring the mass loss of a soil sample after centrifugal rotation, the magnitude of the cohesion within the soil sample can be evaluated, providing experimental basis for the improvement and optimization of tunnel boring machine excavated soil.

[0005] The technical solution of the present invention is as follows:

[0006] In a first aspect of the invention, an apparatus for evaluating the internal cohesion of soil includes a power component and a detection component. The power component includes a base on which a motor is mounted. The output shaft of the motor is fixedly connected to one end of a transmission vertical rod, and the other end of the transmission vertical rod is fixedly connected to a plurality of horizontal rods, each of which is equipped with a detection component. The detection component includes an experimental platform on which a soil sample container is mounted. The wall of the soil sample container has a plurality of circular holes. A hydraulic cylinder is installed at the upper part of the soil sample container, and a gravity sensor is installed at the lower part.

[0007] In some embodiments of the present invention, the hydraulic cylinder is fixed above the soil sample container by a bracket, a pressure sensor is provided on the hydraulic cylinder, the hydraulic cylinder is connected to a pressure disc, and the pressure disc applies pressure to the soil sample in the soil sample container.

[0008] In some embodiments of the present invention, the diameter of the pressure disc is smaller than the inner diameter of the soil sample container, and a rubber sealing ring is provided on the side of the pressure disc, which is in contact with the inner wall of the soil sample container.

[0009] In some embodiments of the present invention, the horizontal bar is fixedly connected to the experimental platform.

[0010] In some embodiments of the present invention, the angles between multiple detection components are the same.

[0011] In some embodiments of the present invention, the gravity sensor is connected to a computer.

[0012] In a second aspect of the invention, a method for evaluating the internal cohesion of soil is provided, comprising the following steps:

[0013] Add the same mass of soil samples to each soil sample container, and apply a specified amount of pressure to the soil samples by driving the pressure disc with a hydraulic cylinder.

[0014] Once the readings of all pressure gauges are the same and stable, the motor drives the soil sample container to rotate for centrifugation. After a period of time, the rotation is stopped.

[0015] After the container has finished rotating, record the data for each part and calculate the arithmetic average. The amount of mass loss characterizes the internal cohesion of the soil sample.

[0016] In some embodiments of the present invention, when performing centrifugation experiments, the motor speed range is 500-1500 r / min, and the rotation time is controlled within 5-10 min.

[0017] In some embodiments of the present invention, the formula for calculating the mass loss rate η of the soil sample is:

[0018]

[0019] In the formula, m1 is the mass of the soil sample before the test, and m2 is the mass of the soil sample after the test.

[0020] In some embodiments of the present invention, after the soil sample is placed into a soil sample container, the soil sample is lightly vibrated to make the soil sample in the container uniform and compacted.

[0021] Stress and state analyses of the soil samples reveal that the lower the internal cohesion, the weaker the soil sample's ability to resist centrifugal force generated by rotation during the test, resulting in more soil particles being ejected. In other words, a higher soil sample mass loss rate η corresponds to lower internal cohesion, and vice versa.

[0022] One or more technical solutions of the present invention have the following beneficial effects:

[0023] (1) The cohesion assessment device provided by the present invention has a simple structure and can quickly assess the cohesion of soil at the construction site. In addition, the assessment comprehensively considers the influence of pressure, soil moisture content and soil type on soil cohesion, which is consistent with the actual construction situation and provides a basis for the improvement of slag and soil under the problem of cutterhead mud cake.

[0024] (2) The cohesion assessment device and method provided by the present invention are suitable for quantitative research under on-site construction. They use centrifugal motion to amplify the gravity effect of soil samples, calculate the mass loss rate of soil samples during the test, estimate the magnitude of cohesion within the soil samples, and realize a quantitative description of cohesion values.

[0025] (3) The cohesion assessment device and method provided by the present invention proposes for the first time to use the mass loss rate of soil sample during rotation to assess the magnitude of cohesion inside the soil, realizing rapid assessment of cohesion inside the soil at the construction site. Compared with existing detection methods, the device and method are relatively simple and can meet the requirements of rapid assessment of cohesion inside the soil at the construction site. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall structure of the device for evaluating the internal cohesion of soil according to the present invention.

[0027] Figure 2 This is a schematic diagram of the detection component in the device for evaluating the internal cohesion of soil according to the present invention.

[0028] In the diagram: 1. Base, 2. Motor, 3. Transmission rod, 4. Horizontal rod, 5. Experimental platform, 6. Detection component, 7. Pressure sensor, 8. Hydraulic cylinder, 9. Pressure disc, 10. Rubber sealing ring, 11. Soil sample container, 12. Gravity sensor. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0030] Example 1

[0031] In a typical embodiment of the present invention, a device for evaluating the internal cohesion of soil is proposed, such as... Figure 1 and Figure 2As shown, the device includes a power unit and a detection unit. The power unit includes a base 1, which provides support for the entire device. A motor 2 is mounted on the base 1, and the output shaft of the motor 2 is fixedly connected to one end of a transmission vertical rod 3. The other end of the transmission vertical rod 3 is fixedly connected to multiple horizontal rods 4, each of which has a detection unit mounted on it. Under the action of the motor, the detection unit on the horizontal rod can be driven to rotate and make circular motion. The detection unit includes an experimental platform 5, on which a soil sample container 11 is mounted. Multiple circular holes are opened on the wall of the soil sample container 11, with the diameter of the holes being 1 / 20 of the bottom diameter of the soil sample container 11. When the soil sample container rotates, some soil sample will be thrown out from the circular holes under the action of centrifugal force. A hydraulic cylinder 8 is installed at the upper part of the soil sample container 11 to provide a certain pressure inside the soil sample container. A gravity sensor 12 is installed at the lower part of the soil sample container to measure the mass loss of the soil sample during the rotation process.

[0032] Specifically, the horizontal rod 4 is fixedly connected to the experimental platform 5 in the detection component. The experimental platform 5 provides support for the detection component. From bottom to top, a gravity sensor 12 and a soil sample container 11 are installed on the experimental platform 5. A bracket with a U-shaped structure is installed on the upper surface of the soil sample container. A hydraulic cylinder 8 is installed at the center of the lower surface of the bracket beam. A pressure sensor 7 is installed on the hydraulic cylinder 8, which can monitor the pressure applied by the hydraulic cylinder in real time. The hydraulic cylinder 8 is connected to a pressure disc 9, which applies pressure to the soil sample in the soil sample container. Different pressures can be applied to the soil sample in the container according to the different pressures inside the actual excavation chamber, thus enabling the evaluation of the cohesion of the soil sample under different stress conditions. The diameter of the pressure disc is smaller than the inner diameter of the soil sample container. A rubber sealing ring is installed on the side of the pressure disc, which fits against the inner wall of the soil sample container to prevent the soil sample from being thrown out from the top of the container during rotation.

[0033] In this embodiment, in order to improve the efficiency of the test (to conduct multiple tests at the same time), the number of detection components can be increased or decreased according to the experimental needs. However, it must be ensured that the angles between the experimental platforms are uniform and that the center of gravity of the device is always on the transmission vertical rod during the experiment. In some implementations, five detection components are set, and the angle between adjacent detection components is 72°.

[0034] In this embodiment, the gravity sensor is connected to a computer. The gravity sensor can detect the loss of soil sample mass, record soil sample mass data in real time during the experiment, and calculate the cohesion inside the soil sample based on the soil sample mass data.

[0035] In this embodiment, the base, transmission vertical rod, experimental platform, and horizontal rod in the device are all made of high-rigidity and high-strength materials to avoid deformation and bending caused by their own rotation or the weight of the soil sample. At the same time, the transmission vertical rod and the horizontal rod, as well as the horizontal rod and the experimental platform, are fixedly connected to ensure that the detection components will not shift during the experiment.

[0036] When using the device, place it on the construction site. To ensure the stability of the device during rotation, the base can be fixed. Then, add soil samples of different moisture contents and types that need to be tested for cohesion into the soil sample container with the same mass. According to the different pressure requirements of the construction site, the hydraulic cylinder drives the pressure disc to apply a specified amount of pressure to the soil sample. After the values ​​of each pressure gauge are the same and stable, the motor drives the soil sample container to rotate to perform a centrifugal test. After a period of time, stop the rotation. After the gravity sensor data stabilizes, record the data of each part and perform an arithmetic average. The amount of mass loss characterizes the internal cohesion of the soil sample.

[0037] The device for evaluating the internal cohesion of soil according to the present invention can comprehensively consider the influence of pressure, soil moisture content and soil type on soil cohesion, which is consistent with the actual construction situation and provides a basis for the improvement of slag and soil under the problem of cutterhead mud cake.

[0038] Example 2

[0039] In a typical embodiment of the present invention, a method for evaluating the internal cohesion of soil is proposed, comprising the following steps:

[0040] Add the same mass of soil sample to each soil sample container, and apply a specified pressure of 0-100kN to the soil sample by driving the pressure disc with a hydraulic cylinder.

[0041] Once the readings of all pressure gauges are the same and stable, the motor drives the soil sample container to rotate for centrifugation. After a period of time, the rotation is stopped.

[0042] After the gravity sensor data stabilizes, record the data for each part and perform an arithmetic average. The amount of mass loss characterizes the internal cohesion of the soil sample.

[0043] In this embodiment, when performing the centrifugation experiment, the speed is 500-1500 r / min, and the rotation time is controlled within 5-10 min.

[0044] In this embodiment, the formula for calculating the mass loss rate η of the soil sample is:

[0045]

[0046] In the formula, m1 is the mass of the soil sample before the test, and m2 is the mass of the soil sample after the test.

[0047] It should be noted that after the soil sample is placed into the soil sample container, the soil sample should be gently vibrated to make the soil sample in the container uniform and compacted. After the device stops rotating, the soil sample left on the experimental platform should be cleaned up in time to ensure the accuracy of the gravity sensor reading.

[0048] When conducting tests to assess the internal cohesion of soil, soil samples with varying pressure, moisture content, and soil type are tested in a centrifugal apparatus based on the on-site construction conditions. The internal cohesion of the soil sample is preliminarily assessed by calculating the mass loss rate of the soil sample. The greater the mass loss rate of the soil sample, the smaller the cohesion of the soil sample, and vice versa.

[0049] By conducting stress and state analysis on the soil sample, it was found that the smaller the cohesion inside the soil sample, the weaker its ability to resist the centrifugal force generated by rotation during the test. Therefore, more soil particles will be thrown out during the test. Thus, the mass loss rate of the soil sample during rotation can be used to characterize the magnitude of the cohesion inside the soil, thereby achieving a quantitative description of the cohesion value and enabling rapid assessment of the cohesion inside the soil at the construction site.

[0050] The embodiments described above provide a detailed explanation of the technical solution of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, or similar substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A device for evaluating the internal cohesion of soil, characterized in that, The device includes a power component and a detection component. The power component includes a base on which a motor is mounted. The output shaft of the motor is fixedly connected to one end of a transmission vertical rod, and the other end of the transmission vertical rod is fixedly connected to multiple horizontal rods. A detection component is mounted on each horizontal rod. The detection component includes an experimental platform on which a soil sample container is mounted. Multiple circular holes are formed on the wall of the soil sample container. A hydraulic cylinder is installed at the top of the soil sample container, and a gravity sensor is installed at the bottom to monitor mass loss in real time. The hydraulic cylinder is fixed above the soil sample container by a bracket. A pressure sensor is installed on the hydraulic cylinder. The hydraulic cylinder is connected to a pressure disc. The pressure disc applies adjustable pressure to the soil sample in the soil sample container. The diameter of the pressure disc is smaller than the inner diameter of the soil sample container. A rubber sealing ring is provided on the side of the pressure disc, and the rubber sealing ring is in contact with the inner wall of the soil sample container to prevent the soil sample from being thrown out from the top of the soil sample container.

2. The apparatus for evaluating the internal cohesion of soil as described in claim 1, characterized in that, The horizontal bar is fixedly connected to the experimental platform.

3. The apparatus for evaluating the internal cohesion of soil as described in claim 1, characterized in that, The angles between multiple detection components are the same.

4. The apparatus for evaluating the internal cohesion of soil as described in claim 1, characterized in that, The gravity sensor is connected to a computer.

5. A method for evaluating the internal cohesion of soil, implemented using the apparatus described in any one of claims 1-4, characterized in that, Includes the following steps: Add the same mass of soil samples to each soil sample container, and apply a specified amount of pressure to the soil samples by driving the pressure disc with a hydraulic cylinder. Once the readings of all pressure gauges are the same and stable, the motor drives the soil sample container to rotate for centrifugation. After a period of time, the rotation is stopped. After the gravity sensor data stabilizes, record the data for each part and perform an arithmetic average. The amount of mass loss characterizes the internal cohesion of the soil sample. Based on the on-site construction conditions, soil samples with varying pressure, soil moisture content, and soil type were centrifuged in the device, and the internal cohesion of the soil samples was preliminarily assessed by calculating the mass loss rate of the soil samples. When conducting centrifugation experiments, the motor speed range is 500-1500 r / min, and the rotation time is controlled within 5-10 min.

6. The method for evaluating the internal cohesion of soil as described in claim 5, characterized in that, mass loss rate of soil samples The calculation formula is: In the formula, m 1 refers to the soil sample quality before the test. m 2 refers to the soil sample quality after the test.

7. The method for evaluating the internal cohesion of soil as described in claim 5, characterized in that, After the soil sample is placed into the soil sample container, it is gently vibrated to make the soil sample in the container uniform and compacted.

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