Test Method for the Ability of the Cutting Surface Material in a Shield Cutterhead to Adsorb Mud Viscosity

Abstract

The present invention relates to the field of shield cutter head performance detection methods, in particular to a test method for the adhesion ability of the cutting surface material in a shield cutter head to the viscosity of slurry. It aims to design a detection method for the slurry-retaining cutting surface of the cutter head to quickly obtain information about the cutting surface and specify the most reasonable plan. The present invention includes clay configuration, measurement of the sliding start angle of the clay, and analysis of the sliding situation between the cutting surface and the clay. The advantages are: saving site space, being convenient for rolling, labor-saving, and being more convenient for on-site management.

Description

Technical Field

[0001] The present invention relates to the field of shield cutter head performance detection methods, and particularly to a test method for the adhesion ability of the cutting surface material in a shield cutter head to mud viscosity. Background Art

[0002] During shield tunneling operations, the strata at the top of the tunnel mainly consist of silty clay, silty fine sand, clay, gravelly soil, and cobble soil. The strata traversed by the tunnel are as follows: silty clay accounts for 16%, silty fine sand accounts for 11%, clay accounts for 8%, gravelly soil accounts for 15%, cobble soil accounts for 5%, strongly weathered mudstone accounts for 25%, moderately weathered mudstone accounts for 14%, and moderately weathered gravelly argillaceous sandstone accounts for 2%. Karst also exists in some local positions.

[0003] Clay, strongly to moderately weathered mudstone contain a large amount of viscous minerals, and the soil adhesion is strong. Viscous particles have certain water absorption expansion and adsorption capabilities. The clay cut by the cutter is extremely easy to adhere to the cutter head panel and the cutter head opening position, and it is not easy to circulate out of the bin, prone to stagnant discharge, and form a piled bottom bin at the bottom of the bin. The viscous soil attached to the cutter head forms mud cakes on the cutter head panel under the extrusion effect, clogging the cutter head opening with mud paste, resulting in poor circulation in the bin, reducing the tunneling efficiency. When tunneling in strata containing clay and mudstone for more than 2400 meters, preventing and controlling mud cake formation on the cutter head during the tunneling process of this project is a key and difficult point.

[0004] At present, the analysis and prediction of mud cake data on the cutter head mainly focus on simulating the on-site working conditions. For example, in the publicly disclosed Chinese patent documents, the patent with the application number CN201810116195.4, titled "An experimental device and method for simulating mud cake formation on a soil pressure balance shield cutter head", simulates the tunneling of a shield in a specific soil body, adjusts the cutter arrangement and construction parameters, and observes the distribution and morphology of mud cakes, thereby providing a basis for studying the generation mechanism of mud cake phenomena and mud cake prevention and disposal methods. Another example is the patent with the application number CN 202110140730.1, titled "A simulation system for regulating mud cake formation on a shield cutter head", which also provides a basis for mud cake prevention and disposal methods through the simulation of the cutter head.

[0005] However, the applicant believes that the current technology mainly focuses on simulating the cutter head system, measuring the real-time temperature and pressure on the cutter head, and then improving the cutter head in combination with the sample situation. However, in actual operation, it is known that the adjustable space for the cutting angle and cutting temperature on the cutter head is actually very low, and in most cases, appropriate adjustments cannot be fully made. Summary of the Invention

[0006] The purpose of the present invention is to solve the problems in the prior art that mud congestion is likely to occur on the cutting surface, and there is a lack of detection methods for the selection of cutting surface materials, making it difficult to detect.

[0007] The specific solution of the present invention is as follows:

[0008] It includes the following steps: (1) Clay preparation: (a) Weigh 300 g of natural clay or simulated shield-site clay and pour it into a mixing bucket; (b) Weigh 20 g of Class II bentonite and pour it into the above mixing bucket, and stir evenly by a motor at a speed of 60 - 120 revolutions per minute; (c) Measure 100 ml of tap water with a measuring cylinder and slowly pour it into the above mixing bucket, and stir evenly again at a speed of 60 - 120 revolutions per minute; (d) Put the prepared clay into a dry sample box and weigh the total mass of the clay and the sample box.

[0009] (2) Clay sliding starting angle test: (a) Select a cutting-surface imitation panel made of the same material as the cutting surface as the experimental board. First, adjust the installation inclination angle of the experimental board relative to the horizontal plane to 0°, then place the sample box containing the clay on the upper part of the steel plate surface. One end of a tensiometer is hung inside the sample box, and the other end is hung on the edge of the experimental board; (b) By making the experimental board rotate, gradually adjust the rotation inclination angle of the experimental board until the sample box starts to rotate on the steel plate surface, record the sliding starting angle, and at the same time measure the tension of the tensiometer, and convert it into the frictional force of the steel plate on the clay through calculation; (c) Use the same steps to adjust the installation inclination angle of the rotating shaft of the experimental board to 5° and 10° respectively to simulate the situation of the cutter head tilting, conduct repeated tests, and record the data to obtain the experimental data of the clay starting angle and starting tension.

[0010] (3) Data analysis to obtain the influence of the installation inclination angle on the starting angle and verify the mud viscosity adsorption ability of the material of this experimental board.

[0011] It also includes step (4) adjustment. The step (4) adjustment includes that when in the results of step (3), the starting angle at any installation angle is greater than 30 degrees, an auxiliary board is introduced to increase the frictional force of the cutting surface. The auxiliary board and the cutting surface are fixed by inner hexagon bolts and screw holes. The test method of the performance of the auxiliary board is as shown in steps (1) to (3).

[0012] Within the said step (2), the rotation speed of the self-rotation is less than 6 revolutions per minute.

[0013] In step (1), replace it with measuring 20 ml of tap water with a measuring cylinder to form clay B, and then measure the sliding starting angle of clay B on the experimental board when it is in the sample box.

[0014] Add a pre-step before step (1). The pre-step includes extracting 500 g of clay on-site.

[0015] It also includes step (5) fatigue test. The step (5) includes controlling the experimental board to rotate bidirectionally within the starting angle for more than 3 days, and then measuring the surface friction degree and flatness error of the area where the sample box is located on the experimental board.

[0016] The experimental board is formed by stacking two of the materials steel, molybdenum-vanadium alloy, 65Mn, or chromium-nickel alloy layer by layer.

[0017] The beneficial effects are as follows: Different from the prior art, for the first time, the research on the mud cake is proposed, and then according to the data of the mud cake, the steel sheet most suitable for the current year's mud cake is found. Further, the steel sheet is equivalent to adding a toughened film that is beneficial to the sliding of the mud on the cutting head. At the same time, the toughened film itself has a set of detection platforms, which can be adjusted and replaced in real time under different working conditions, greatly improving the space for changing the properties of the cutting head;

[0018] Specifically, the blade installed on the rake face of the cutting head, that is, the main working surface, has the excellent characteristic of low surface friction, which can greatly reduce the adhesion of the mud on the main cutting surface. At the same time, due to different blade materials, it can meet the requirements of different excavation soil layers with different requirements, maximizing the avoidance of blockage of the mud on the steel sheet caused by reciprocating bouncing while ensuring the cost;

[0019] In the present invention, through the research on the viscosity of the mud between the cutting surface and the mud, it is obtained what materials and at what angles there are reciprocating surges. The reciprocating surges are the key to the congestion of the mud channel. In the research of the present invention, the data of the mud viscosity of different blade materials under different working environments are obtained, which can determine whether the mud channel will be congested in future specific work. If there are potential hazards, solutions can also be proposed in time, the material of the cutting surface of the cutting head can be replaced, and at the same time, it can be verified whether the solution is reasonable. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic diagram of the initial position of the test installation in the present invention;

[0021] Figure 2 is a schematic diagram of the appropriate turning of the simulated shield cutter head;

[0022] Figure 3 is a schematic diagram of the shield cutter head;

[0023] Names of each component in the figure: 1. Experimental board; 2. Tensile meter; 3. Sample box; 4. Rotating shaft; 5. Test bench; 6. Cutting surface. DETAILED DESCRIPTION OF THE INVENTION

[0024] The following is a description of the preferred embodiments of the present invention with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0025] A test method for the mud viscosity adsorption capacity of the cutting surface material in a shield cutter head, comprising the following steps: (1) Clay preparation: (a) Weigh 300 g of natural clay or simulated shield site cost clay and pour it into a stirring bucket; (b) Weigh 20 g of Class II bentonite and pour it into the above stirring bucket, and stir evenly by a motor at a speed of 60 - 120 revolutions per minute; (c) Measure 100 ml of tap water with a measuring cylinder, slowly pour it into the above stirring bucket, and stir evenly again at a speed of 60 - 120 revolutions per minute; (5) Put the prepared clay into a dry sample box and weigh the total mass of the clay and the sample box.

[0026] (2) Clay sliding start angle test: (a) Select an imitation cutting surface panel made of the same material as the cutting surface as the experimental board. First, adjust the installation inclination angle of the experimental board relative to the horizontal plane to 0°, then place the sample box containing clay on the upper part of the steel plate surface. One end of the tensiometer is hung inside the sample box, and the other end is hung on the edge of the experimental board; (b) By rotating the experimental board, gradually adjust the rotation inclination angle of the experimental board until the sample box starts to rotate on the steel plate surface, record the sliding start angle, and at the same time measure the tension of the tensiometer, and convert it into the friction force of the steel plate on the clay through calculation; (c) Use the same steps to adjust the installation inclination angle of the rotating shaft of the experimental board to 5° and 10° respectively to simulate the situation of the cutter head tilt, conduct repeated tests, and record the data to obtain the clay start angle and start tension test data.

[0027] (3) Data analysis, obtain the influence of the installation inclination angle on the start angle, and verify the mud viscosity adsorption capacity of the material of this experimental board.

[0028] It also includes step (4) adjustment. The step (4) adjustment includes that when in the results of step (3), the start angle at any installation angle is greater than 30 degrees, an auxiliary board is introduced to increase the cutting surface friction force. The auxiliary board and the cutting surface are fixed by inner hexagon bolts and screw holes. The test method for the performance of the auxiliary board is as shown in steps (1) to (3).

[0029] In step (2), the rotation speed of the self-rotation is less than 6 revolutions per minute.

[0030] In step (1), replace it with measuring 20 ml of tap water with a measuring cylinder to form clay B, and then measure the sliding start angle of clay B on the experimental board in the sample box.

[0031] Add a pre-step before step (1). The pre-step includes extracting 500 g of clay on site.

[0032] It also includes step (5) fatigue test. The step (5) includes controlling the experimental board to rotate bidirectionally within the start angle for more than 3 days, and then measuring the surface friction degree and flatness error of the area where the sample box is located on the experimental board.

[0033] During the experiment, a simulation test bench was also used. The simulation test bench includes a test bench frame. The test bench frame includes a lower storage and support area and an upper equipment inclination area. There is a hinge connection with a hinge structure component between the lower storage and support area and the upper equipment inclination area. An experimental board support platform driven by a bidirectional motor is installed in the upper equipment inclination area. The experimental board support platform is installed on a gantry bracket and includes a rotating shaft at the bottom and a claw installed on the bottom rotating shaft. The claw clamps an experimental board with a length of 40 to 60 cm and a width of 40 to 60 cm.

[0034] The rotating shaft is installed at the top of the gantry bracket via a bearing, and its input end is connected to the output shaft of the bidirectional motor. The experimental board corresponds to the steel plate material.

[0035] The following takes a single working process as an example:

[0036] First, prepare the clay: (1) Weigh 300 g of natural clay and pour it into a stirring bucket; (2) Weigh 20 g of Class II bentonite and pour it into the above-mentioned stirring bucket, and stir evenly.

[0037] 3) Measure 100 ml of tap water with a measuring cylinder, slowly pour it into the above-mentioned stirring bucket, and stir evenly; 4) Put the prepared clay into a dry sample box and weigh the total mass of the clay and the sample box.

[0038] Secondly, conduct a test on the clay sliding starting angle. Adjust the upper equipment inclination area to first adjust the installation inclination of the specially processed experimental board to 0°, and then place the sample box containing the clay on the upper part of the steel plate surface; (2) Through the control system, gradually adjust the rotation inclination of the steel plate until the clay starts to rotate on the steel plate surface, record the sliding starting angle, and at the same time measure the pulling force of the tensiometer, and convert it into the frictional force of the steel plate on the clay through calculation; (3) Use the same steps to adjust the installation inclination of the steel plate to 5° and 10° respectively, conduct repeated tests, and record the data. The specific data is shown in Table 1.

[0039] Table 1 Experimental data of clay starting angle and starting pulling force

[0040]

[0041] After that, conduct data analysis:

[0042] Based on the experimental data, the influence of the installation inclination on the clay sliding starting angle was analyzed. The research found that under the experimental conditions, as the installation inclination increases, the clay sliding starting inclination gradually decreases, that is, as the installation inclination increases, it is more and more beneficial for the clay to slide off the steel plate surface. Taking Q345 steel plate with Ra0.012 as an example, draw the influence relationship curve of the installation inclination on the clay sliding starting inclination. Ra0.012 is equal to a roughness of 0.012.

[0043] Going further, we can analyze the influence of steel properties on the starting angle:

[0044] The characteristics of steel in this study mainly include the type of steel and the influence of finish. According to data analysis, it can be concluded that for the same type of steel, when the finish is different, it has a greater impact on the starting angle of clay sliding, that is, the better the finish, the smaller the starting angle under the same conditions, that is, under the same sliding length, it can buy more time for clay sliding on the steel plate; by comparing the curve Q345 (Ra0.012) with the molybdenum-vanadium alloy curve (Ra0.012), and the curve Q345 (Ra0.2) with the molybdenum-vanadium alloy curve (Ra0.2), it can be concluded that for different steels with the same finish, the molybdenum-vanadium alloy steel plate has a better anti-mud cake effect than the Q345 steel plate. The specific molybdenum-vanadium alloy can be Cr12, Cr16, Cr20, and Q235 can also be replaced by Q225, Q245. After that, combined with the on-site situation and cost control, the most suitable material is selected as the cutting surface. The cutting surface can be directly formed by material or by patch.

[0045] Furthermore, the influence of steel properties on the sliding friction of clay was analyzed.

[0046] Since the sliding friction force of the steel plate on the clay in the indoor test is not easy to obtain directly, the method of directly measuring the tensile force when the clay slides is adopted. 下滑力 =F 拉力 +F 摩擦力 , and the friction force when the clay slides down can be converted. That is, when the sliding force is constant, the greater the measured pulling force, the smaller the friction force when the clay slides down, and the less likely it is to form mud cakes. For the convenience of calculation, the analysis was carried out under the condition of installation inclination angle of 0°. The total mass of the clay box sample box is 286g. The specific tensile test data and calculated friction force are shown in Table 4. By comparing the friction data of Q345 (Ra0.012) and Q345 (Ra0.2), and the friction data of molybdenum-vanadium alloy (Ra0.012) and molybdenum-vanadium alloy (Ra0.2), it can be seen that for the same steel plate, the higher the smoothness, the smaller the friction force; by comparing the friction data of Q345 (Ra0.012) and molybdenum-vanadium alloy (Ra0.012), and the friction data of Q345 (Ra0.2) and molybdenum-vanadium alloy (Ra0.2), it can be seen that when the smoothness is the same, the friction force of the clay on the molybdenum-vanadium alloy steel plate is less than that on the Q345 steel plate.

[0047] Table 2 Statistical table of friction of different materials and smooth surfaces at installation angle 0°

[0048]

[0049] Furthermore, the influence of the cutter head rotation speed on the mud cake was tested and analyzed.

[0050] 5.2.1 Test steps

[0051] (1) Weigh the prepared clay, fix the contact area between the clay and the steel plate, ensure that the contact area remains consistent for each test, and then press the clay with the same force to make the clay and the steel plate stick together;

[0052] (2) Adjust the multifunctional steel plate clamping device to rotate it at different speeds and record the sliding of the clay on the steel plate;

[0053] (3) Weigh different masses of clay and repeat the above test.

[0054] 5.2.2 Data Analysis

[0055] Through the above test, the data on the effect of the cutter head speed on the sliding of clay of different masses for the same steel plate and the same finish were obtained, and the test phenomena were recorded. The test data are shown in Table 3. From the data analysis in the table, it can be seen that for a fixed mass per unit area, the faster the steel plate speed, the less conducive it is for the clay to slide, and the easier it is to accumulate and form a mud cake. The specific phenomenon in the test is that as the steel plate speed increases, the clay will swing back and forth without falling off during the 0-360° rotation process. When the steel plate speed is below the critical speed, the mud will slide off the edge of the steel plate during the 0-180° rotation process.

[0056] Table 3 Statistical table of the effect of steel plate rotation speed on clay sliding

[0057]

[0058] Since the contact area between clay and steel plates of different masses is the same, a corresponding relationship can be formed between the clay mass per unit area and the steel plate rotation speed, so as to provide a parameter basis for setting the penetration rate and cutter head rotation speed of the on-site shield machine.

[0059] Table 4 Corresponding relationship between K and critical speed of steel plate clay sliding

[0060]

[0061] Based on the data in Table 4, the data are fitted.

[0062] In the specific work, a plate is installed above the lower storage support area to receive the fallen mud cake. Finally, for the case of clay as the material, the test conclusions and suggestions are drawn.

[0063] (1)For different installation inclinations of the same steel plate, the larger the installation inclination, the smaller the starting angle of clay sliding, and the more conducive it is to the discharge of clay. It is recommended to appropriately increase the slope angle of the steel at the cutter head opening while ensuring the strength at the cutter head opening.

[0064] (2)For different surface finishes of the same steel plate, the higher the surface finish, the smaller the starting angle of clay sliding under the condition of the same installation inclination, and the more conducive it is to the discharge of muck in the clay stratum. It is recommended to install high-gloss mirror steel plates on the rough steel plate surface at the cutter head opening of the existing shield machine and conduct on-site tests.

[0065] (3)Through the comparison of tests between Q345 steel plates and molybdenum-vanadium alloy steel plates, in terms of preventing mud cake formation, molybdenum-vanadium steel plates have better performance than Q345 steel plates. However, compared with the rough surfaces of traditional steel materials, both types of steel can show obvious advantages. It is recommended to install the two types of steel plates respectively at the opposite support parts of the on-site cutter head for testing to determine which material is more economical and reasonable for later use.

[0066] (4)The cutter head speed has a great influence on the sliding of clay on the steel plate. For clay with a certain unit area mass, when the cutter head speed is below the critical speed, the clay can smoothly slide down from the edge of the steel plate. When the cutter head speed is above the critical speed, the clay adheres and swings left and right with the 360° rotation of the steel plate and is not easy to slide off the steel plate surface. It is recommended to adjust the cutter head speed in a timely manner according to the amount of muck when tunneling on-site in strata prone to mud cake formation.

[0067] In specific implementation, by following the above method, targeted conclusions for different soil types can be obtained. Thus, in combination with cost control, the most suitable material can be selected as the steel sheet to be laid on the main cutting surface of the shield cutting, and the channel situation of the mud retention can be adjusted and improved.

[0068] Figure 2 The angle in [angle] simulates the inclination of the tunnel and the turning situation of the cutter head.

[0069] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention. Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A test method for the mud viscosity adsorption capacity of the cutting surface material in a shield cutter head, characterized in that, a simulation test bench is used. The simulation test bench includes a test bench frame, and the test bench frame includes a lower storage and support area and an upper equipment inclination area. There is a hinge connection structure connected by a hinge structure component between the lower storage and support area and the upper equipment inclination area. An experimental plate support platform driven by a bidirectional motor is installed in the upper equipment inclination area. The experimental plate support platform includes a rotating shaft at the bottom and a claw installed on the bottom rotating shaft. The claw clamps the experimental plate; the input end of the rotating shaft is connected to the output shaft of the bidirectional motor; the test method includes the following steps: (1) Clay preparation: (a) Weigh 300 g of natural clay or simulated shield site clay and pour it into a stirring bucket; (b) Weigh 20 g of Class II bentonite and pour it into the above stirring bucket, and stir evenly by a motor at a speed of 60 - 120 revolutions per minute; (c) Measure 100 ml of tap water with a measuring cylinder and slowly pour it into the above stirring bucket, and stir evenly again at a speed of 60 - 120 revolutions per minute; (d) Put the prepared clay into a dry sample box and weigh the total mass of the clay and the sample box; (2) Clay sliding start angle test: (a) Select an imitation cutting surface panel made of the same material as the cutting surface as the experimental plate. Adjust the upper equipment inclination area to first adjust the installation inclination of the experimental plate relative to the horizontal plane to 0°, and then place the sample box containing clay on the upper part of the experimental plate. One end of a tensiometer is hung inside the sample box and the other end is hung on the edge of the experimental plate; (b) By rotating the experimental plate, gradually adjust the rotation inclination of the experimental plate until the sample box starts to rotate on the surface of the experimental plate, record the sliding start angle, and at the same time measure the tension of the tensiometer, and convert it into the friction force of the experimental plate on the clay through calculation; (c) Use the same steps to adjust the installation inclination of the rotating shaft of the experimental plate to 5° and 10° respectively to simulate the situation of the cutter head tilting, conduct repeated tests, and record the data to obtain the clay start angle and start tension test data; (3) Data analysis to obtain the influence of the installation inclination on the start angle and verify the mud viscosity adsorption capacity of the material of this experimental plate; (4) Adjustment. When in the result of step (3), the start angle at any installation inclination is greater than 30 degrees, an auxiliary plate is introduced to increase the cutting surface friction force. The auxiliary plate and the cutting surface are fixed by inner hexagon bolts and screw holes. The test method for the performance of the auxiliary plate is as shown in steps (1) to (3).

2. The test method for the mud viscosity adsorption capacity of the cutting surface material in a shield cutter head as described in claim 1, characterized in that: in step (2), the rotation speed of the self-rotation is less than 6 revolutions per minute.

3. The test method for the mud viscosity adsorption capacity of the cutting surface material in a shield cutter head as described in claim 1, characterized in that: in step (1), replace it with measuring 20 ml of tap water with a measuring cylinder to form clay B, and then measure the sliding start angle of clay B on the experimental plate when it is in the sample box.

4. The test method for the mud viscosity adsorption capacity of the cutting surface material in a shield cutter head as described in claim 3, characterized in that: Add a pre-step before step (1), and the pre-step includes extracting 500 g of clay on-site.

5. The test method for the mud viscosity adsorption capacity of the cutting surface material in the shield cutter head as described in claim 1, characterized in that: It further includes step (5) fatigue test, and the step (5) includes controlling the experimental plate to rotate bidirectionally within the starting angle for more than 3 days, and then measuring the surface friction and flatness error of the area where the sample box is located on the experimental plate.

6. The test method for the mud viscosity adsorption capacity of the cutting surface material in the shield cutter head as described in claim 5, wherein the experimental plate is formed by stacking two of the materials steel, molybdenum vanadium alloy, 65Mn, or chromium nickel alloy layer by layer.

Images