Method for optimizing tunneling parameters of shield simulation device based on rubber pad

Abstract

The invention relates to a method for optimizing tunneling parameters of a shield simulation device based on a rubber pad, which comprises the following steps: cutting an arc-shaped rubber pad with a certain size to simulate a stratum, the size of the arc-shaped rubber pad corresponds to a horizontal foundation bed coefficient of the stratum, and arranging the arc-shaped rubber pad on a pile body curved surface far away from a model shield tunneling machine in a clinging manner, the effect of the shield jacking force of the pile body on the cambered surface of the arc-shaped rubber pad is equivalent to the effect of the vertical load on the plane of the rectangular rubber pad; and setting a tunneling parameter interval, traversing reference values in the interval to carry out a cutting experiment, evaluating and recording the pile breaking conditions of the pile foundation under different tunneling parameter values, and determining the optimal tunneling parameter meeting the evaluation standard. According to the method, the condition of a single pile under the action of soil resistance during shield cutting can be simulated, the damage process of the pile body can be observed, so that shield tunneling parameters can be better optimized based on experimental results, and the method is simple, convenient, easy to operate and beneficial to popularization and application and has great reference and guiding significance for construction of actual shield tunnel engineering.

Description

Technical Field

[0001] The invention relates to the technical field of shield construction, and in particular to a method for optimizing excavation parameters of a shield simulation device based on a rubber pad. Background Art

[0002] With the gradual development of large-scale subway construction in my country, the research on urban underground engineering construction technology has developed into an important topic. Shield technology has been widely studied, applied and developed in countries around the world for its advantages such as safety, speed and environmental protection. It has become the main construction method for building urban tunnels such as subways, telecommunications, and water supply and sewers. After long-term engineering practice and research and exploration, my country has accumulated considerable experience in using shield method to construct subway tunnels and has a relatively complete shield method tunnel construction theory.

[0003] However, when a new subway tunnel is built using the shield method, the shield tunnel will inevitably pass through existing buildings, and the probability of passing through will become increasingly greater. Due to the characteristics of subway and underground engineering construction and the influence of many uncertain factors such as hydrogeology, subway and underground engineering construction inevitably involve many engineering construction risks. In previous projects, when the shield machine cuts reinforced concrete piles in the soil layer, the incomplete cutting, winding and breaking of the steel bars can easily cause the shield cutter head torque to increase instantly, resulting in damage to the shield cutter head. At the same time, inappropriate shield machine excavation parameters can easily lead to greater disturbance of the stratum during the shield cutting pile foundation, resulting in greater surface settlement. At present, the optimization of excavation parameters for shield cutting underground pile foundations in China only relies on the excavation parameters provided by the project site for analysis, and the analysis results have large deviations.

[0004] The industry has introduced the shield simulation experiment method, in which strain gauges and other monitoring devices are attached to a model pile body, and a similar-scaled model shield machine is used to cut the pile body, and the strain force changes during the pile body destruction process are recorded, so as to study the pile body destruction mechanism. Among them, the shield model experiment is divided into two cases: the pile body is buried in the ground and not buried in the ground. After the pile body is buried in the ground, it is impossible to effectively observe the destruction process of the pile body being cut by the cutter head; the shield machine cutting single pile experiment without the pile body buried in the ground can effectively avoid the above shortcomings, but because the pile body is not buried in the ground, there is a lack of rear and lateral soil support. When the shield machine cuts the single pile that is not buried in the ground, it cannot truly restore the situation where the pile body has stratum resistance support. At the same time, the single pile experiment without burying in the ground generally adopts point support. Because there is no uniform support on the rear side of the pile foundation, the pile body is prone to stress concentration under the action of the shield top thrust, resulting in the single pile being sheared and producing a large number of transverse cracks, which interferes with the experimental observation and analysis of experimental results.

[0005] Therefore, some people have proposed a phased simulation experiment combining the two methods. For example, Chinese Patent Publication No. CN118407766A discloses a test system for determining the excavation parameters of shield tunneling in cutting underground pile foundations. First, a single pile cutting experiment of a shield machine without entering the ground is carried out, and then a pile foundation cutting experiment of a shield machine covered with soil is carried out to further verify and adjust these parameters. This method is cumbersome and difficult to operate, and is difficult to promote and use.

[0006] The above problems are worth solving. Summary of the invention

[0007] In order to overcome the shortcomings of the existing technology, the present invention provides a method for optimizing the excavation parameters of a shield simulation device based on a rubber pad, which is an experimental optimization method for shield cutting of a single pile that is not buried in the ground. The experimental method can simulate the stratum resistance to closely fit the actual construction situation of the shield tunnel, and can provide uniform back support for the single pile that is not buried in the ground, so that the experimental process can simulate the situation of the shield cutting a single pile under the action of soil resistance.

[0008] The technical solution of the present invention is as follows:

[0009] A method for optimizing the tunneling parameters of a shield simulator based on rubber pads:

[0010] Cutting a curved rubber pad of a certain size to simulate a stratum, wherein the size of the curved rubber pad corresponds to the horizontal bed coefficient of the stratum, and the curved rubber pad has a curved surface for fitting the curved surface of the pile body;

[0011] An arc-shaped rubber pad is arranged close to the curved surface of the pile body away from the model shield machine, so that the shield thrust of the pile body acting on the curved surface of the arc-shaped rubber pad is equivalent to the vertical load acting on the plane of the rectangular rubber pad;

[0012] Set the excavation parameter range, traverse the parameter values ​​within the range to conduct cutting experiments, evaluate and record the pile foundation breakage under different excavation parameter values, and determine the optimal excavation parameters that meet the evaluation standards.

[0013] The present invention according to the above solution is characterized in that the step of cutting the arc-shaped rubber pad of a certain size to simulate the stratum includes:

[0014] Determine the type of stratum at the construction site and query its horizontal base coefficient;

[0015] Let the equivalent stratum base coefficient of the rectangular rubber pad be equal to the stratum horizontal base coefficient, and calculate the length, width and thickness of the rectangular rubber pad;

[0016] The arc length of the arc rubber pad is equal to the length of the rectangular rubber pad, the arc length of the arc rubber pad in the width direction is equal to the width of the rectangular rubber pad, and the thickness of the arc rubber pad is equal to the thickness of the rectangular rubber pad. The arc rubber pad is cut out.

[0017] The present invention according to the above scheme is characterized in that the stratum types include silty clay, medium-coarse sand, silty clay, sandy clay, fully weathered granite, and strongly weathered granite. The horizontal base bed coefficient of the silty clay is 20.97 MPa / m, the horizontal base bed coefficient of the medium-coarse sand is 21.80 MPa / m, the horizontal base bed coefficient of the silty clay is 53.63 MPa / m, the horizontal base bed coefficient of the sandy clay is 62.91 MPa / m, and the horizontal base bed coefficient of the fully weathered granite is 35-40 MPa / m.

[0018] The present invention according to the above scheme is characterized in that the calculation formula of the equivalent formation base coefficient and stiffness of the rectangular rubber pad is: equivalent formation base coefficient = stiffness ÷ (length × width); and the calculation formula of the stiffness of the rectangular rubber pad is: stiffness = apparent elastic modulus × (length × width) ÷ thickness.

[0019] The present invention according to the above scheme is characterized in that the step of closely arranging an arc-shaped rubber pad on the curved surface of the pile body away from the model shield machine comprises:

[0020] An I-beam is installed inside the opening of the model box of the shield simulator;

[0021] Installing piles outside the opening of the model box of the shield simulation device;

[0022] The arc-shaped rubber pad is arranged between the pile body and the I-beam, with one side of the arc-shaped rubber pad close to the curved surface of the pile body and the other side against the I-beam.

[0023] Furthermore, when a curved rubber pad is arranged between the pile body and the I-beam, if the space between the pile body and the I-beam is insufficient to arrange the curved rubber pad, the I-beam is adjusted to increase the installation space; if there is a gap between the curved rubber pad and the I-beam after the curved rubber pad is arranged, a steel plate is added to the gap.

[0024] Furthermore, the step of installing a pile body outside the opening of the model box of the shield simulator includes:

[0025] A first arc-shaped slot block is fixed on the outer side wall above the opening of the model box;

[0026] Fixing the bottom support of the pile foundation on the outer side wall below the opening of the model box;

[0027] Place the bottom of the pile body on the bottom support of the pile foundation, and place the top of the pile body into the semicircular groove of the first arc-shaped groove block;

[0028] The second arc-shaped slot block is buckled with the first arc-shaped slot block and is tightened with bolts, so that the first arc-shaped slot block and the second arc-shaped slot block clamp the top of the pile body.

[0029] The present invention according to the above scheme is characterized in that the excavation parameters include shield thrust and cutter head speed, and the values ​​within the range of shield thrust and the values ​​within the range of cutter head speed are combined in pairs in sequence as parameter combinations for shield cutting experiments.

[0030] The present invention according to the above solution is characterized in that the evaluation criteria for pile foundation broken conditions include:

[0031] A. No transverse cracks are produced in the cut pile body;

[0032] B. Measure the strain of the pile body. The maximum bending moment during the pile cutting process is less than 300N·m;

[0033] C. The steel bars are in a cut state, not a pulled state;

[0034] D. The maximum particle size of the exfoliated concrete debris shall not exceed the diameter of the auger excavator;

[0035] E. When the pile is destroyed, the shield cutting depth shall be at least half of the pile diameter.

[0036] Furthermore, the step of measuring the pile body strain during the pile body cutting process includes:

[0037] Several strain gauges are arranged on the back side and left and right sides of the pile body along the axis direction of the pile body;

[0038] Use strain gauges to test the internal force change data of the pile, including the bending moment change data.

[0039] The present invention according to the above scheme has the following beneficial effects:

[0040] The present invention uses an arc-shaped rubber pad to simulate the soil resistance of the stratum, and sets the arc-shaped rubber pad on the pile body that is not buried in the ground, so as to realize the simulated soil body wrapping the back of the pile body, which can not only simulate the pile body under the action of the soil resistance during shield cutting, but also directly observe the pile body condition, thereby realizing intuitive judgment using multiple evaluation criteria during the pile body destruction process, improving the judgment accuracy, and finding the best excavation parameters;

[0041] The present invention determines the excavation parameters by observing the pile breaking situation, and can simulate the type of stratum where the prototype pile foundation is located, which is conducive to fitting the actual situation, so that the theoretical experimental results have a greater reference and guiding significance for the construction of actual shield tunnel engineering; the present invention optimizes the shield excavation parameters based on the experimental results, the method is simple and easy to operate, the efficiency is higher, and it is conducive to promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a flow chart of the method of the present invention;

[0043] Figure 2It is a structural schematic diagram of the present invention;

[0044] Figure 3 It is a partial enlarged view of the present invention;

[0045] Figure 4 It is a schematic diagram of the structure of the model shield machine, pile body and arc-shaped rubber pad in the present invention;

[0046] Figure 5 Schematic diagram of the force model of rubber pad and pile.

[0047] In the figure,

[0048] 1. Model box; 2. Model shield machine; 3. Pile body; 31. Strain gauge; 4. Arc rubber pad; 5. I-beam; 6. Pile top fixing parts; 7. Pile foundation bottom support; 8. Shield propulsion support reaction frame; 81. Side channel steel; 82. Front steel plate; 9. Shield propulsion sliding support. DETAILED DESCRIPTION

[0049] In order to better understand the purpose, technical scheme and technical effect of the present invention, the present invention is further explained in conjunction with the accompanying drawings and embodiments. It should be noted that similar numbers and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. At the same time, it is stated that the embodiments described below are only used to explain the present invention and are not used to limit the present invention.

[0050] It should be noted that when an element is referred to as being "fixed on" or "disposed on" another element, it may be directly on the other element or there may also be a central element, and when an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time.

[0051] The indicated orientation or position relationship is based on the orientation or position relationship shown in the drawings, or the orientation or position relationship in which the product of the application is usually placed when used, or the orientation or position relationship commonly understood by technical personnel in this field, or the orientation or position relationship in which the product of the application is usually placed when used. It is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0052] The terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features. "Several" means two or more, unless otherwise clearly and specifically defined.

[0053] like Figures 1 to 5As shown, a method for optimizing the excavation parameters of a shield simulation device based on a rubber pad is used to realize the experiment of shield cutting a single pile that is not buried in the ground. The damage process of the pile body 3 being cut by the cutter head during the cutting process can be observed intuitively, and the excavation parameters corresponding to the required shield cutting effect can be better sought. At the same time, the optimized experimental method of the present invention can also simulate the formation resistance to closely fit the actual construction situation of the shield tunnel, and provide uniform back support for the single pile that is not buried in the ground; the specific method is:

[0054] Cut a certain size of arc-shaped rubber pad to simulate the stratum, the size of the arc-shaped rubber pad corresponds to the horizontal bed coefficient of the simulated stratum, and the arc-shaped rubber pad has an arc surface for fitting the curved surface of the pile body; set the arc-shaped rubber pad close to the curved surface of the pile body 3 away from the model shield machine 2, so that the shield thrust of the pile body acting on the curved surface of the arc-shaped rubber pad is equivalent to the vertical load acting on the plane of the rectangular rubber pad. Set the excavation parameter interval according to the on-site working conditions, traverse the parameter values ​​in the interval to conduct cutting experiments, evaluate and record the pile foundation broken pile situation under different excavation parameter values, and determine the best excavation parameters that meet the evaluation standards.

[0055] Among them, the excavation parameters include shield thrust and cutter head speed. According to the on-site feedback of actual working conditions, the shield thrust range is A1 to An (kilonewton), and the cutter head speed range is B1 to Bn (rpm), where n is a natural number. A parameter combination (An, Bn) is set in the model shield machine, and the pile cutting experiment is performed, and the pile foundation breakage situation is evaluated and recorded.

[0056] The specific thrust range of the shield machine and the cutterhead speed range are obtained from the front-end work report, which is related to the type of stratum in the actual working conditions, as well as the number of cutting cutters on the prototype shield machine, the width of the cutter blade, the compressive strength of the pile foundation, etc., and can be directly obtained by querying the front-end work report. For example, 10kN~20kN, 0.5rpm~2.0rpm, so the parameter combinations of multiple groups of experiments are (10kN, 0.5rpm), (10kN, 0.6rpm), ... (11kN, 1.0rpm), (20kN, 2.0rpm), etc.

[0057] In the above method, arc-shaped rubber pads of different sizes have different stiffnesses, which can simulate the stratum resistance. The cut arc-shaped rubber pad can closely fit the curved surface of the pile body by using its curved surface, so as to simulate the effect of soil wrapping the back of the pile body 3 as much as possible. In addition, by setting the rubber pad in such a way that the arc-shaped rubber pad fits the curved surface of the pile body, it can better meet the load shape of the shield top thrust transmitted through the pile body as a circular surface, so that the shield top thrust of the pile body acting on the arc-shaped rubber pad is equivalent to the vertical load acting on the plane of the rectangular rubber pad. In this way, the cutting size of the arc-shaped rubber pad 4 can be calculated by the equivalent rectangular rubber pad.

[0058] In a specific embodiment, the stiffness calculation formula of the rectangular rubber pad under vertical load is as follows:

[0059] G=0.117e 0.03HS (1)

[0060] E a =iG (2)

[0061] i=3.6(1+2.22S 2 ) (3)

[0062]

[0063] Where: G is the shear elastic modulus of the rubber material, in MPa; HS is the Shore hardness of the rubber; E a is the apparent elastic modulus of the compression rubber spring; i is the influencing factor of the geometric shape; S is the ratio of the bearing area to the free area of ​​the rectangular rubber spring, the bearing area is the area of ​​one side in contact with the load, and the free area is the remaining area after removing the bearing area; a and b are the length and width of the rectangular rubber pad, respectively, in mm; h is the thickness of the rectangular rubber pad, in mm; P is the rubber stiffness, in N / mm; K is the equivalent formation bed coefficient of the rubber pad, in GPa / m.

[0064] From the above, it can be seen that by adjusting the Shore hardness and size of the rubber pad, the equivalent stratum base coefficient of the rubber pad can be changed, thereby simulating the horizontal base coefficient of different types of strata. The principle is that the axis of the pile body is perpendicular to the ground. When the shield pushes and cuts the pile body, the direction of the resistance applied by the stratum is perpendicular to the shield cutter head and can be regarded as the horizontal direction. Therefore, when simulating the stratum resistance, the simulation of the horizontal stratum resistance is mainly considered; and the stratum resistance calculation formula is: stratum resistance = horizontal base coefficient × displacement; therefore, when simulating the stratum resistance, the focus is on the equivalence of the horizontal base coefficient.

[0065] In the present invention, the step of cutting a curved rubber pad of a certain size to simulate a stratum specifically includes:

[0066] S1. Determine the type of stratum at the construction site and query its horizontal base bed coefficient;

[0067] The types of strata include silty clay, medium-coarse sand, silty clay, sandy clay, fully weathered granite, and strongly weathered granite. The horizontal base coefficient of the silty clay is 20.97MPa / m, the horizontal base coefficient of the medium-coarse sand is 21.80MPa / m, the horizontal base coefficient of the silty clay is 53.63MPa / m, the horizontal base coefficient of the sandy clay is 62.91MPa / m, and the horizontal base coefficient of the fully weathered granite is 35-40MPa / m. Please refer to the following table for details:

[0068]

[0069] S2. Let the equivalent stratum base coefficient K of the rectangular rubber pad be equal to the stratum horizontal base coefficient Kh, and calculate the Shore hardness and size of the rectangular rubber pad according to the formula to obtain the length, width and thickness of the rectangular rubber pad;

[0070] For example, if the simulated stratum type is determined to be fully weathered granite, and its horizontal bed coefficient Kh is known to be 35-40 (Mpa / m), then the K value of the equivalent stratum bed coefficient of the rectangular rubber pad is 35-40 (Mpa / m), so the size of the rectangular rubber pad can be deduced using the above formulas (1) to (6). Specifically, from the equivalent stratum bed coefficient = stiffness ÷ (length × width), stiffness = apparent elastic modulus of the rectangular rubber pad × (length × width) ÷ thickness, the length, width and thickness of the rectangular rubber pad can be deduced.

[0071] S3, define that the arc length of the arc rubber pad 4 is equal to the length of the rectangular rubber pad, the arc length of the arc width direction of the arc rubber pad 4 is equal to the width of the rectangular rubber pad, and the thickness of the arc rubber pad 4 is equal to the thickness of the rectangular rubber pad, and cut out the arc rubber pad 4.

[0072] As can be seen from the foregoing, the present invention arranges the rubber pad in such a way that the arc-shaped rubber pad fits the curved surface of the pile body, so that the shield thrust of the pile body acting on the arc-shaped rubber pad is equivalent to a vertical load acting on the plane of the rectangular rubber pad. Therefore, the length, width and thickness calculated in step S2 can be used as the relevant dimensions of the arc-shaped rubber pad 4.

[0073] In the present invention, the step of closely arranging an arc-shaped rubber pad on the curved surface of the pile body 3 away from the model shield machine 2 specifically includes:

[0074] An I-beam 5 is installed inside the opening of the model box 1 of the shield simulator;

[0075] A pile body 3 is installed outside the opening of the model box 1 of the shield simulation device;

[0076] The arc-shaped rubber pad 4 is arranged between the pile body 3 and the I-beam 5 , with one side of the arc-shaped rubber pad 4 close to the curved surface of the pile body and the other side against the I-beam 5 .

[0077] The model box 1 is filled with heavy objects, so that the box is not easy to move and can provide back support for the arc-shaped rubber pad and the pile body.

[0078] The model shield machine 2 is arranged outside the model box 1, and the pile body 3 to be cut is located between the box (model box 1) and the model shield machine 2. The I-beam 5 is installed inside the opening of the model box 1, and the I-beam 5 is arranged parallel to the pile body 3, and is used to provide rigid boundary support when the shield cuts the pile body 3.

[0079] The I-beam 5 is against the back side of the arc-shaped rubber pad 4. If the thickness of the arc-shaped rubber pad 4 is small, there will be a gap between the arc-shaped rubber pad and the I-beam after the arc-shaped rubber pad is set, and a steel plate is placed between the arc-shaped rubber pad 4 and the I-beam 5; if the thickness of the arc-shaped rubber pad 4 is large, resulting in insufficient space between the pile body and the I-beam to set the arc-shaped rubber pad, the I-beam 5 is removed and the I-beam 5 is moved and adjusted in the box. Generally, after the I-beam 5 is adjusted, the soil is filled into the box, and the bottom of the I-beam 5 is covered as much as possible, and the amount of soil does not exceed the box opening.

[0080] The physical and mechanical parameters of the pile body 3 used in the simulation are also calculated and determined by similar simulation, and the calculation is as follows:

[0081] Pile diameter: Where R m is the diameter of the model pile; R p is the diameter of the prototype pile foundation; C L is the geometric similarity ratio of the model experiment.

[0082] Modulus of elasticity: Where E m is the elastic modulus of the model pile; E p is the elastic modulus of the prototype pile foundation.

[0083] Pile compressive strength: where σ m is the compressive strength of the model pile; p is the compressive strength of the prototype pile foundation.

[0084] Steel bar tension and compression stiffness: Where E m is the elastic modulus of the model steel bar; A m is the cross-sectional area of ​​the model steel bar; E p is the elastic modulus of the prototype steel bar; A p is the cross-sectional area of ​​the prototype steel bar.

[0085] In the present invention, the step of installing the pile body 3 outside the opening of the model box 1 of the shield simulation device specifically includes:

[0086] A first arc-shaped slot block is fixed on the outer side wall above the opening of the model box 1;

[0087] A pile foundation bottom support 7 is fixed to the outer side wall below the opening of the model box 1;

[0088] Place the bottom of the pile body 3 on the pile foundation bottom support 7, and place the top of the pile body 3 into the semicircular groove of the first arc-shaped groove block;

[0089] The second arc-shaped slot block is buckled with the first arc-shaped slot block and is tightened with bolts, so that the first arc-shaped slot block and the second arc-shaped slot block clamp the top of the pile body 3 .

[0090] The first arc slot block and the second arc slot block serve as the pile top fixing installation member 6. The first arc slot block is fixedly connected to the model box body 1. When the pile body 3 is replaced, there is no need to disassemble the first arc slot block. The second arc slot block is detachably connected to the first arc slot block. The size and shape of the second arc slot block match those of the first arc slot block. After the two are buckled together, there is a circular or elliptical clamping opening in the middle. After the second arc slot block is buckled with the first arc slot block, the top of the pile body 3 can be clamped through the clamping opening; the edges of the first arc slot block and the second arc slot block are correspondingly provided with screw holes for passing bolts, and the first arc slot block and the second arc slot block can be fastened and connected using ordinary bolts.

[0091] The pile foundation bottom support 7 can fix the bottom of the pile body 3 to prevent the pile body 3 from displacement during the cutting process. In a preferred embodiment, the pile foundation bottom support 7 is provided with a limiting notch to better fix the bottom end of the pile body 3.

[0092] In the present invention, the evaluation criteria for pile foundation broken conditions include:

[0093] A. No transverse cracks are produced in the cut pile body;

[0094] B. Measure the strain of the pile body. The maximum bending moment during the pile cutting process is less than 300N·m;

[0095] C. The steel bars are in a cut state, not a pulled state;

[0096] The cut steel bars will fall off immediately, while the broken steel bars are pulled out by the shield cutter hook. In addition, the broken steel bars are usually long, so they will continue to wrap around the cutter head and affect the excavation.

[0097] D. The maximum particle size of the exfoliated concrete debris does not exceed the diameter of the spiral excavator inside the model shield machine;

[0098] If the particle size of the concrete fragments is too large, it may wear the cutter head during construction and is not easy to be discharged by the spiral excavator. The particle size assessment standard for the concrete fragments is that it does not exceed the diameter of the spiral excavator.

[0099] E. When the pile is destroyed, the shield cutting depth is at least more than half of the pile diameter;

[0100] Theoretically, the greater the shield cutting depth when the pile foundation is finally destroyed, the better the stability of the lower part of the pile foundation can be maintained during the cutting process. If the lower part of the pile foundation has better stability, the impact on the upper part of the pile foundation and surface buildings should be relatively small.

[0101] In a specific embodiment, the step of measuring the change of bending moment during the cutting process of the pile body 3 includes:

[0102] A plurality of strain gauges 31 are arranged on the back side and the left and right sides of the pile body 3 along the axial direction of the pile body 3 ; the strain gauges 31 are used to test the internal force variation data of the pile body 3 , including the bending moment variation data.

[0103] For example, the Shore hardness of the rubber pad is 55, and the size of the arc rubber pad 4 is determined to be 500mm×150mm×10mm. The equivalent stratum base coefficient calculated according to the theoretical formula is 38.14 (MPa / m), which is 35-40 (MPa / m) in the horizontal base coefficient range of fully weathered granite. Each time a combined parameter value is selected within the excavation parameter range, a cutting experiment is performed, and each experiment uses the arc rubber pad of the determined size as described above, and multiple groups of experimental results are obtained, and the experimental results are evaluated. Through evaluation and comparison, it is concluded that when the thrust of the experimental model shield machine 2 is 11kN and the cutter head speed is 1.0rpm, the experimental results show that the pile body 3 does not produce transverse cracks and there is no block crushing. The maximum bending moment of the pile body 3 measured is 280N·m, the steel bars in the pile body are all cut off, the particle size of the peeling concrete debris meets the requirements, and the shield cuts off at least three-quarters of the pile diameter depth, meeting the evaluation standard for pile breakage after cutting a single pile.

[0104] The shield simulation device of the present invention comprises a model box 1, a model shield machine 2, and a model pile body (hereinafter referred to as pile body 3), wherein the pile body 3 is arranged between the model box 1 and the model shield machine 2. An opening is arranged on the side of the box body of the model box 1 close to the model shield machine 2, and the pile body 3 is detachably mounted on the outer side wall of the box body opening, and an I-beam 5 is arranged on the inner side wall of the box body opening, and an arc-shaped rubber pad 4 is arranged between the I-beam 5 and the pile body 3, and the arc surface of one side of the arc-shaped rubber pad 4 is closely attached to the arc surface of the pile body 3, and the other side of the arc-shaped rubber pad 4 is against the I-beam 5.

[0105] In this embodiment, the outer side wall above the box opening is provided with a pile top fixing installation member 6, and the pile top fixing installation member 6 includes a first arc slot block and a second arc slot block, the first arc slot block is fixedly connected to the box, the second arc slot block is detachably connected to the first arc slot block, and the first arc slot block and the second arc slot block are both provided with an arc slot, and screw holes are provided on the side of the arc slot. When in use, the top of the pile body 3 is first placed in the arc slot of the first arc slot block, and then the arc slot of the second arc block is buckled on the other side of the pile body 3, and finally bolts are passed through the corresponding screw holes of the two arc slot blocks, and tightened to complete the installation of the top of the pile body 3.

[0106] In this embodiment, a pile foundation bottom support 7 is provided on the outer side wall below the box opening, and the pile foundation bottom support 7 is placed on the ground or the same platform together with the box, and the pile foundation bottom support 7 is fixedly connected to the box, and the bottom of the pile body 3 is fixed on the pile foundation bottom support 7. In order to prevent the pile body 3 from being displaced during the cutting process, a limiting notch can be provided on the pile foundation bottom support 7, and the bottom of the pile body 3 is placed in the limiting notch, which can also better fix the bottom end of the pile body 3.

[0107] In this embodiment, the cross section of the arc-shaped rubber pad 4 is fan-shaped, and the thickness of the arc-shaped rubber pad 4 is uniform, so that the simulated soil uniformly wraps the back of the pile body 3 .

[0108] In this embodiment, the I-beam 5 is arranged inside the box body parallel to the pile body 3, which can increase the contact surface with the arc rubber pad 4 and ensure that the arc rubber pad 4 is closely attached to the pile body curved surface of the pile body 3. The I-beam 5 is fixed to the inner wall of the box body in a detachable installation manner. When the required arc rubber pad 4 is thicker and the space between the I-beam 5 and the pile body 3 is insufficient to place the arc rubber pad 4, the I-beam 5 can be removed, and the I-beam 5 can be fine-tuned and moved inside the box body, and then reinstalled and fixed. In an optional embodiment, a steel plate is provided between the I-beam 5 and the arc rubber pad 4 to make up for the gap between the I-beam 5 and the arc rubber pad 4.

[0109] In this embodiment, a shield propulsion support reaction frame 8 is provided on one side of the model box 1, and the shield propulsion support reaction frame 8 includes a side channel steel 81 and a front steel plate 82. Three parallel side channel steels 81 are provided on each side of the box, and each side channel steel 81 is reversely bent and welded to the edge of the box. The front steel plate 82 is respectively connected to the side channel steels 81 on both sides of the box. Specifically, the side of the front steel plate 82 is extended with a connecting channel steel, and the connecting channel steel is welded to the side channel steel 81 of the corresponding height. A square hole is provided in the center of the front steel plate 82 to ensure that the oil pump of the model shield machine 2 can pass through and avoid the oil pump from abutting against the front steel plate 82.

[0110] A model shield machine 2 is placed in the internal space of the shield propulsion support reaction frame 8. Specifically, the internal space is provided with a shield propulsion sliding support 9, and the shield propulsion sliding support 9 is provided with a curved slide groove adapted to the bottom of the model shield machine 2. The model shield machine 2 is driven by the power equipment to excavate toward the box body on the shield propulsion sliding support 9.

[0111] The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0112] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for optimizing the excavation parameters of a shield simulation device based on a rubber pad, characterized in that: Cutting a curved rubber pad of a certain size to simulate a stratum, wherein the size of the curved rubber pad corresponds to the horizontal bed coefficient of the stratum, and the curved rubber pad has a curved surface for fitting the curved surface of the pile body; An arc-shaped rubber pad is arranged close to the curved surface of the pile body away from the model shield machine, so that the shield thrust of the pile body acting on the curved surface of the arc-shaped rubber pad is equivalent to the vertical load acting on the plane of the rectangular rubber pad; Set the excavation parameter range, traverse the parameter values ​​within the range to conduct cutting experiments, evaluate and record the pile foundation breakage under different excavation parameter values, and determine the optimal excavation parameters that meet the evaluation standards.

2. According to claim 1, the method for optimizing the excavation parameters of the shield simulation device based on the rubber pad is characterized in that: The step of cutting the arc-shaped rubber pad of a certain size to simulate the stratum includes: Determine the type of stratum at the construction site and query its horizontal base coefficient; Let the equivalent stratum base coefficient of the rectangular rubber pad be equal to the stratum horizontal base coefficient, and calculate the length, width and thickness of the rectangular rubber pad; The arc length of the arc rubber pad is equal to the length of the rectangular rubber pad, the arc length of the arc rubber pad in the width direction is equal to the width of the rectangular rubber pad, and the thickness of the arc rubber pad is equal to the thickness of the rectangular rubber pad. The arc rubber pad is cut out.

3. The method for optimizing the excavation parameters of a shield simulation device based on a rubber pad according to claim 2 is characterized in that: The calculation formulas for the equivalent formation base coefficient and stiffness of the rectangular rubber pad are: Equivalent formation base coefficient = stiffness ÷ (length × width); and the calculation formula for the stiffness of the rectangular rubber pad is: Stiffness = apparent elastic modulus × (length × width) ÷ thickness.

4. The method for optimizing the excavation parameters of a shield simulation device based on a rubber pad according to claim 1 is characterized in that: The step of providing a curved rubber pad in close contact with the curved surface of the pile body away from the model shield machine comprises: An I-beam is installed inside the opening of the model box of the shield simulator; Installing piles outside the opening of the model box of the shield simulation device; The arc-shaped rubber pad is arranged between the pile body and the I-beam, with one side of the arc-shaped rubber pad close to the curved surface of the pile body and the other side against the I-beam.

5. The method for optimizing the excavation parameters of a shield simulation device based on a rubber pad according to claim 4 is characterized in that: When setting the arc-shaped rubber pad between the pile body and the I-beam, if the space between the pile body and the I-beam is insufficient to set the arc-shaped rubber pad, adjust the I-beam to increase the installation space; if there is a gap between the arc-shaped rubber pad and the I-beam after the arc-shaped rubber pad is set, add a steel plate in the gap.

6. The method for optimizing the tunneling parameters of a shield simulator based on a rubber pad according to claim 4 is characterized in that: The step of installing the pile body outside the opening of the model box of the shield simulator includes: A first arc-shaped slot block is fixed on the outer side wall above the opening of the model box; Fixing the bottom support of the pile foundation on the outer side wall below the opening of the model box; Place the bottom of the pile body on the bottom support of the pile foundation, and place the top of the pile body into the semicircular groove of the first arc-shaped groove block; The second arc-shaped slot block is buckled with the first arc-shaped slot block and is tightened with bolts, so that the first arc-shaped slot block and the second arc-shaped slot block clamp the top of the pile body.

7. The method for optimizing the excavation parameters of a shield simulation device based on a rubber pad according to claim 6 is characterized in that: A limiting notch is arranged on the top of the support at the bottom of the pile foundation.

8. The method for optimizing the tunneling parameters of a shield simulator based on a rubber pad according to claim 1 is characterized in that: The excavation parameters include shield thrust and cutter head rotation speed. The values ​​within the range of shield thrust and the values ​​within the range of cutter head rotation speed are combined in pairs in sequence as the parameter combination of the shield cutting experiment.

9. The method for optimizing the excavation parameters of a shield simulator based on a rubber pad according to claim 1, characterized in that: The assessment criteria for pile foundation failure include: A. No transverse cracks are produced in the cut pile body; B. Measure the strain of the pile body. The maximum bending moment during the pile cutting process is less than 300 N∙m; C. The steel bars are in a cut state, not a pulled state; D. The maximum particle size of the exfoliated concrete debris does not exceed the diameter of the auger; E. When the pile is destroyed, the shield cutting depth shall be at least half of the pile diameter.

10. The method for optimizing the excavation parameters of a shield simulation device based on a rubber pad according to claim 9 is characterized in that: The steps of measuring the pile body strain during the pile body cutting process include: Several strain gauges are arranged on the back side and left and right sides of the pile body along the axis direction of the pile body; Use strain gauges to test the internal force change data of the pile, including the bending moment change data.

Images