Characterization Method for the Floating Control Effect of Synchronous Grouting Materials in Shield Tunnels

Abstract

The present invention discloses a method for characterizing the floating control effect of a synchronous grouting material for a shield tunnel. First, the simulated segment is immersed in the prepared grouting material slurry, and the displacement change of the simulated segment under the buoyancy force of the slurry is detected. Secondly, the early shrinkage deformation curve of the slurry under sealed conditions is tested, and the influence of factors such as the self-shrinkage deformation of the slurry is deducted to obtain the displacement amount of the simulated segment. The gravity change of the simulated segment in the slurry is collected by a force sensor, and the upward buoyancy force received by the simulated segment is calculated. Finally, according to the displacement and load change data of the simulated segment, the time node when the slurry buoyancy force is lost and the magnitude of the acting force at this time are determined, the upward buoyancy force - upward displacement change curve in this time period is plotted, and the work done by the slurry buoyancy force on the segment in this time period is calculated, so as to characterize the floating control effects of slurries with different performances. The method of the present invention can intuitively and accurately reflect the differences in the slurry performance, and is simple to operate and low in cost.

Description

Technical Field

[0001] The invention belongs to the technical field of testing the floating control effect of grouting materials, and particularly relates to a method for characterizing the floating control effect of synchronous grouting materials for shield tunnels. Background Art

[0002] The shield method is widely used in the construction of underground spaces such as urban subways and cross-river tunnels, and the diameter of shield tunnels shows an increasing trend. According to the construction principle of the shield method and the stress state of the formed segments, the buoyancy force on the formed segments of shield tunnels increases as a quadratic power function with the segment diameter, and the increase in buoyancy force is much greater than the anti-buoyancy force of the segment structure's self-weight. As the excavation diameter of shield tunnels increases, the problem of segment floating becomes more prominent. The buoyancy force on the segments after they are assembled and withdrawn from the shield tail will increase exponentially, and the segments will float severely, which may lead to segment cracking, threatening the control of the shield attitude and increasing the shield attitude deviation, causing difficulties in segment assembly, misalignment, and even damage, seriously affecting the waterproof effect of the tunnel and the safety of later operation. The synchronous grouting material for shield tunnels can play a role in controlling segment floating, reducing ground settlement, transferring loads, and constructing the first waterproof and anti-seepage barrier.

[0003] During the construction of shield tunnels, the parameters such as the performance of grouting materials, grouting pressure, grouting volume, and tunneling rate are often adjusted by real-time monitoring of the floating amount of segments. The regulation of the performance of grouting materials is crucial for realizing the floating control of segments. There are certain technical risks and it is time-consuming and laborious to adjust the performance of grouting materials through the actual measurement and feedback of the floating amount of engineering segments, increasing the construction operation cost. Simulating and evaluating the performance differences of grouting materials under laboratory conditions is simple and low-cost for the floating control effect of segments, and can provide sufficient technical accumulation and support for on-site operations. Usually, under laboratory conditions, the buoyancy force of simulated segments in the slurry is detected and evaluated through force analysis to compare the floating control effects of different slurries. Compared with inert slurries, the single-component slurry or two-component slurry that is widely used at home and abroad is mostly an active slurry. After the slurry is injected into the segment gap, its performance is a gradual change process, that is, the buoyancy force and viscous force on the segment are dynamic change processes, and both exist simultaneously and cannot be separated. Therefore, the method of simulating segment force analysis cannot clearly determine the buoyancy loss process of the slurry and cannot truly and effectively characterize the anti-floating effect of the slurry. Summary of the Invention

[0004] Object of the Invention: To solve the problems existing in the prior art, the object of the invention is to provide a method for characterizing the floating control effect of synchronous grouting materials for shield tunnels. This method jointly analyzes by simulating the displacement and load changes of segments in the slurry, determines the time node of the loss of upward buoyancy force of the slurry, calculates the work done by the upward buoyancy force of the slurry to evaluate the floating control effect of the slurry, intuitively and accurately reflects the performance differences of the slurry, and is simple to operate and low in cost.

[0005] Technical solution: To achieve the above-mentioned invention objective, the technical solution adopted by the present invention is as follows:

[0006] A method for characterizing the floating control effect of a synchronous grouting material for a shield tunnel, characterized by comprising the following steps:

[0007] Step S1: Prepare the synchronous grouting slurry, immerse the simulated segment in the synchronous grouting slurry, and configure weights on the simulated segment to simulate the binding force of the shield shell of the shield machine, and detect and obtain the displacement-time change curve 1 of the simulated segment under the action of the buoyancy force;

[0008] Step S2: Test and calculate the early shrinkage deformation amount caused by the self-shrinkage deformation of the grouting slurry under the sealed condition, and add the influence of the early shrinkage deformation amount to the displacement-time change amount to obtain the displacement-time correction change curve 2 of the simulated segment under the action of the buoyancy force; the adding the influence of the early shrinkage deformation amount to the displacement-time change amount is specifically adding the early shrinkage deformation amount corresponding to each time point to the displacement amount corresponding to each time point of curve 1.

[0009] Step S3: Immerse the simulated segment in the grouting slurry, collect the gravity change of the simulated segment in the grouting slurry to obtain the buoyancy force-time change curve 3 of the simulated segment under the action of the buoyancy force;

[0010] Step S4: Use the time node when the displacement change in the displacement-time correction change curve 2 tends to be stable as the determination time node T for the loss of the buoyancy force of the grouting slurry, obtain the buoyancy force magnitude at the corresponding time point through the buoyancy force-time change curve 3, and draw the buoyancy force-displacement change curve of the simulated segment within the time range of 0 to T, and calculate the shaded area surrounded by the buoyancy force-displacement change curve using the calculus principle as the work value of the buoyancy force on the simulated segment, which is used to characterize the floating control performance of the grouting slurry: within the time range of 0 to T, the smaller the work value, the smaller the displacement of the simulated segment, the smaller the buoyancy force received, and the better the anti-floating performance of the grouting slurry.

[0011] As a specific implementation method, in step S1, the method steps for configuring weights on the simulated segment to simulate the binding force of the shield shell of the shield machine are as follows:

[0012] Estimate the initial buoyancy force magnitude of the simulated segment in the grouting slurry according to the density of the grouting slurry and the appearance size of the simulated segment;

[0013] Add weights to the simulated segment so that the sum of the self-weight of the simulated segment and the weight of the weights is slightly less than the initial buoyancy force magnitude;

[0014] At regular time intervals during the test , The range of values is from 1h to 2h. Remove 1 / N of the weights added to the simulated segment, where N is a positive integer not less than 5, until all the weights are removed, so as to simulate the constraint force applied by the shield shell of the shield machine to the segment and the attenuation process.

[0015] As a specific implementation scheme, in step S2, the method for obtaining the early shrinkage deformation of the grouting slurry is as follows:

[0016] Place the same grouting slurry used in the test in a cube mold. Cover the four surrounding surfaces of the mold with plastic film to keep the grouting slurry in a sealed environment, prevent humidity exchange between the grouting slurry and the external environment, and make the temperature in the mold consistent with the environmental temperature during the test. Then, use a laser displacement sensor to collect and record the early shrinkage deformation of the grouting slurry in real time.

[0017] As a specific implementation scheme, the upward buoyancy force is formed by the combined action of the slurry buoyancy force, the slurry viscosity force, the self-weight of the segment, and the weight of the counterweight used to simulate the shield shell constraint force.

[0018] As a specific implementation scheme, in step S3, a load sensor is used to collect the change in the gravity of the simulated segment in the grouting slurry.

[0019] As a specific implementation scheme, in step S3, the simulated segment is horizontally arranged. A rigid rod is fixedly connected to the lower pipe wall of the simulated segment, and the other end of the rigid rod is connected to a load sensor.

[0020] As a specific implementation scheme, in step S4, the method for drawing the upward buoyancy force-displacement change curve of the simulated segment within 0 to T time is as follows:

[0021] Take the time node when the displacement change in the displacement-time correction curve 2 tends to be stable as the determination time node T for the loss of the upward buoyancy force of the grouting slurry. Obtain the magnitude F1 of the upward buoyancy force corresponding to the loss time node T through the upward buoyancy force-time change curve 3. The force at the initial moment in the upward buoyancy force-time change curve 3 is denoted as F0. Plot the graph based on the displacement change data within the 0 to T time period in the displacement-time correction curve 2 and the force change data from F0 to F1 in the upward buoyancy force-time change curve 3 to obtain the upward buoyancy force-displacement change curve of the simulated segment within 0 to T time.

[0022] As a specific implementation scheme, the simulated segment is made of a hollow cylindrical metal, and it always moves up and down in the vertical direction during the test, and the simulated segment is horizontally arranged.

[0023] As a further preferred solution, a vertical transmission rod is fixedly connected to the upper pipe wall of the simulated segment. The transmission rod is arranged through a vertically fixedly arranged linear bearing to limit the up-and-down movement of the simulated segment in the vertical direction. A counterweight platform is arranged at the top of the transmission rod for configuring and adding weights for simulating the constraint force of the shield shell of the shield machine.

[0024] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0025] The test method for characterizing the floating control effect of the synchronous grouting material for shield tunnels provided by the present invention first obtains the displacement change of the simulated segment affected by the buoyancy of the slurry, and considers the problem of large self-shrinkage deformation caused by bleeding and segregation due to poor slurry quality, and eliminates the influence of this part on the displacement of the simulated segment to obtain test data that more truly reflects the floating control effect of the slurry. On this basis, combined with the test data of the force analysis of the simulated segment in the slurry, the magnitude of the upward buoyancy force of the simulated segment affected by slurries with different performances and the law of the loss of the upward buoyancy force can be studied. At the same time, the formation and evolution law of the internal microstructure of the slurry can be studied, providing a theoretical guidance for establishing a rapid determination method for the slurry setting time, and the slurry setting time is an important time node for determining the phase change of its internal structure. By jointly analyzing the changes in the displacement and load of the simulated segment in the slurry, the time node of the loss of the upward buoyancy force of the slurry is obtained, and the work done by the upward buoyancy force of the slurry in this stage is calculated to evaluate the floating control effect. This method can more clearly and accurately reflect the differences in the performance of the slurry, and is simple to operate and low in cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is the displacement-time change curve of the simulated segment according to the embodiment of the present invention;

[0027] Figure 2 is the early shrinkage deformation curve of the synchronous grouting material according to the embodiment of the present invention;

[0028] Figure 3 is the corrected displacement-time corrected change curve of the simulated segment according to the embodiment of the present invention;

[0029] Figure 4 is the time-upward buoyancy force change curve of the simulated segment according to the embodiment of the present invention.

[0030] Figure 5 is the displacement-upward buoyancy force change curve of the simulated segment according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The present invention will be further described below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention, and cannot be used to limit the protection scope of the present invention.

[0032] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific circumstances.

[0033] Embodiment

[0034] In an embodiment of the present invention, the following method is adopted to characterize the floating control effect of the synchronous grouting material for shield tunnels. The specific steps are as follows:

[0035] (1) Prepare the synchronous grouting material by stirring according to a specific mix ratio. Immerse the simulated segment in the prepared grouting slurry, and detect the displacement change of the simulated segment under the combined action of the buoyancy of the slurry, the viscous force of the slurry, the self-weight of the segment, and the weight of the counterweight used to simulate the constraint force of the shield shell.

[0036] Specifically, the above synchronous grouting material is prepared according to the materials and mix ratios shown in Table 1. After mixing all the materials evenly, add water and stir with a mortar mixer for 3 minutes to make the required slurry.

[0037] In actual engineering applications, theoretically, the upward buoyancy of the slurry on the segment is the largest after grouting. However, after grouting, the time point when the segment floating amount reaches the maximum value is generally at the 2 - 3 rings after the segment exits the shield tail. The main reason for this situation is that the shield shell of the shield machine has a certain constraint force on the segment. As the shield machine continuously advances forward, the constraint force of the shield shell on the segment gradually decreases.

[0038] Therefore, in order to be closer to the actual situation, the simulated segment is made of a hollow cylindrical metal, and its weight can be adjusted by adding or reducing counterweights according to the design requirements of the floating amount, and the attenuation process of the constraint force of the simulated segment by the shield shell can be simulated.

[0039] Regarding the method of increasing the initial counterweight of the simulated segment and removing the subsequent counterweights as time progresses, specifically, in actual engineering, the upward buoyancy varies according to the diameter of the segment and is about 2 - 3 times the self-weight of the segment.

[0040] Therefore, first, based on the slurry density and the appearance dimensions of the simulated segment, estimate the initial buoyancy of the simulated segment. The slurry density is ρ, the volume of the simulated segment is V, and the self-weight of the segment is M1. At this time, the viscous force of the slurry on the segment can be ignored. The initial buoyancy of the segment can be approximately simulated as F = ρVg - M1g. Then, by controlling the counterweight of the simulated segment, control the initial upward buoyancy to be about twice the self-weight of the simulated segment. Continuously add counterweights to make the self-weight of the segment slightly less than the initial upward buoyancy. The added counterweight is recorded as M2. Thereafter, take one-sixth of the counterweight added to the segment every 1.5 h (recorded as M0, M2 = 6M0), and take all the counterweights on the simulated segment in six times. That is, after 9 h, the self-weight of the simulated segment returns to M1.

[0041] In addition, in order to limit the simulated segment to always move vertically up and down during the test, the cylindrical simulated segment is fixedly connected to the transmission rod and used in conjunction with a linear bearing. Under the action of the upward buoyancy of the slurry, the simulated segment and the transmission rod can freely slide up and down under the action of the linear bearing with extremely small friction. And the displacement-time change curve S0-T of the simulated segment is collected by a displacement sensor, as Figure 1 shown.

[0042] Table 1 Components and contents of the slurry test mix ratio in the embodiment

[0043]

[0044] (2) Prepare the slurry according to the mix ratio shown in Table 1, and test the early deformation data of the grouting slurry under sealed conditions. The method is as follows:

[0045] During the test, the slurry is placed in a 100*100*100 mm cube mold, and a plastic film is covered on its surrounding surfaces to ensure that the slurry is in a sealed environment, avoid humidity exchange between the slurry and the external environment, and the environmental temperature needs to be consistent with the environmental temperature during the test. And the early deformation data of the slurry is collected by a laser displacement sensor, as Figure 2 shown.

[0046] Since the synchronous grouting material for shield tunnels is a system with a very large water-binder ratio, the free water content in the slurry is too high, and it is prone to slurry bleeding and segregation phenomena, and the slurry shrinkage strain is relatively large. Therefore, when using the slurry displacement change curve to characterize the floating control effect of the slurry on the segment, if the displacement change caused by the difference in the self-shrinkage deformation of the slurry itself is not considered, it will bring errors to the experimental results.

[0047] Based on the displacement change curve of the simulated segment, add the displacement change of the simulated segment caused by factors such as the self-shrinkage deformation of the slurry, and the corrected displacement-time correction change curve S1-T of the simulated segment under the action of the slurry buoyancy can be obtained, as Figure 3 shown.

[0048] (3) Connect the simulated segment to the load sensor through a rigid rod. Prepare the grout according to the mix ratio shown in Table 1. Re-inject the prepared synchronous grout into the slurry storage tank so that the grout just submerges the simulated segment. Collect the change in the gravity of the simulated segment in the grout through the load sensor, calculate the buoyancy force acting on the simulated segment, and plot the buoyancy force-time change curve F-T, as shown in Figure 4 shown.

[0049] Specifically, an S-type strain gauge load sensor with a range of 50 N is used. This sensor can detect both positive pressure and reverse tension.

[0050] (4) Combine the displacement and load change data of the simulated segment to determine the time node when the buoyancy force of the grout is lost and the magnitude of the buoyancy force corresponding to the time node. Plot the buoyancy force-buoyancy rise F-S change curve during this time period, and calculate the work done by the buoyancy force of the grout on the segment during this time period, so as to characterize the floating control effect of grouts with different performances.

[0051] Generally, the floating control effect of different grout performances can be characterized by the buoyancy rise of the segment on the one hand and the magnitude of the buoyancy force on the other hand. When the grout is just injected into the shield tail gap, it is almost in a liquid state, and at this time the buoyancy force is at its maximum value. During the entire grouting process, the performance of the grout is constantly changing, and the buoyancy force and viscous force of the grout acting on the simulated segment are also in a dynamic change process. During the buoyancy force test, the viscous resistance and buoyancy force cannot be distinguished and effectively separated.

[0052] In the initial stage, the simulated segment has a tendency to move upward under the action of its own gravity and the buoyancy force of the grout. At this time, the direction of the viscous resistance force of the grout on the segment is downward. As time progresses, the cementitious material in the grout gradually hydrates, the internal structure of the matrix slowly undergoes a phase change until it hardens, and the buoyancy force of the grout gradually weakens. When the buoyancy force is less than the gravity of the simulated segment, the viscous resistance force of the grout on the simulated segment may turn into an upward frictional force over time. In addition, affected by the self-shrinkage of the grout, the force-bearing process of the simulated segment becomes extremely complex. As Figure 4 shown, the buoyancy force of the grout acting on the simulated segment is always in a dynamic change. Therefore, it is impossible to determine the time node when the buoyancy force of the grout disappears through the time-force curve. However, the magnitude of the initial buoyancy force of the grout and the speed at which the buoyancy force is lost are related to the overburden pressure and counterweight. The greater the buoyancy force of the grout on the segment, the greater the counterweight required to resist the buoyancy force, and the slower the buoyancy force is lost, the longer the influence effect of the buoyancy force of the grout on the segment, and the greater the difficulty of floating control.

[0053] Therefore, the technical solution provided by the present invention determines the time node when the buoyancy force acting on it through the time-displacement curve of the simulated segment, as shown in Figure 3As shown in the figure, the time node when the displacement of the simulated segment tends to be stable is recorded as T1, which is regarded as the node when the buoyancy of the slurry is lost. The time point of T1 is Figure 4 The corresponding acting force is recorded as F1. Figure 4 The acting force at the initial moment of the slurry is recorded as F0.

[0054] According to Figure 3 the displacement change data in the time period of 0 to T1 in Figure 4 and the acting force change data of F0 to F1 in Figure 5 plot a graph, the buoyancy-displacement curve F-S of the simulated segment in the time period of 0 to T1 can be obtained. Calculate the shaded area of this region according to the calculus principle, as

[0055] shown. This is the work W done by the slurry buoyancy on the segment in this time period. The better the anti-floating effect of the slurry, the smaller the upward acting force, the smaller the displacement of the simulated segment, and the smaller the calculated W value. Therefore, the anti-floating effect of different performance slurries on the segment can be characterized by the W value.

[0055] The above is only the preferred implementation manner of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and deformations can be made, and these improvements and deformations should also be regarded as the protection scope of the present invention.

Claims

1. A method for characterizing the floating control effect of synchronous grouting materials for shield tunnels, characterized in that, It includes the following steps: Step S1: Prepare the synchronous grouting slurry, immerse the simulated segment in the synchronous grouting slurry, and configure weights on the simulated segment to simulate the constraint force of the shield shell of the shield machine, and detect and obtain the displacement-time change curve 1 of the simulated segment under the action of the buoyancy force; Step S2: Test and calculate the early shrinkage deformation amount caused by the self-shrinkage deformation of the grouting slurry under the sealed condition, and add the influence of the early shrinkage deformation amount to the displacement-time change amount to obtain the displacement-time correction change curve 2 of the simulated segment under the action of the buoyancy force; Step S3: Immerse the simulated segment into the grouting slurry, collect the gravity change of the simulated segment in the grouting slurry to obtain the buoyancy-time change curve 3 of the simulated segment under the action of the buoyancy force; Step S4: Use the time node when the displacement change in the displacement-time correction change curve 2 tends to be stable as the determination time node T for the loss of the buoyancy force of the grouting slurry, obtain the buoyancy force magnitude at the corresponding time point through the buoyancy-time change curve 3, and thus draw the buoyancy-displacement change curve of the simulated segment within the time range of 0 to T, and use the calculus principle to calculate the shaded area enclosed by the buoyancy-displacement change curve as the work value of the buoyancy force on the simulated segment, which is used to characterize the floating control performance of the grouting slurry: within the time range of 0 to T, the smaller the work value, the smaller the displacement of the simulated segment, the smaller the buoyancy force received, and the better the anti-floating performance of the grouting slurry.

2. The characterization method for the floating control effect of the synchronous grouting material for shield tunnels according to claim 1, wherein, In step S1, the method steps for configuring weights on the simulated segment to simulate the constraint force of the shield shell of the shield machine are as follows: Estimate the initial buoyancy force magnitude of the simulated segment in the grouting slurry according to the density of the grouting slurry and the external dimensions of the simulated segment; Add weights to the simulated segment so that the sum of the self-weight of the simulated segment and the weight of the weights is slightly less than the initial buoyancy force magnitude; At regular time intervals during the test , The value range is 1h to 2h. Take 1 / N of the weights added to the simulated segment, where N is a positive integer not less than 5, until all the weights are removed, so as to simulate the constraint force applied by the shield shell of the shield machine to the segment and the attenuation process.

3. The characterization method of the floating control effect of the synchronous grouting material for shield tunnels according to claim 1, wherein, In step S2, the method for obtaining the early shrinkage deformation amount of the grouting slurry is as follows: Place the same grouting slurry as used in the test in a cube mold, cover the four surrounding surfaces of the mold with plastic film to make the grouting slurry in a sealed environment condition, avoid humidity exchange between the grouting slurry and the external environment, and make the temperature in the mold consistent with the environmental temperature during the test, and then use a laser displacement sensor to collect and record the early shrinkage deformation amount of the grouting slurry in real time.

4. The characterization method of the floating control effect of the synchronous grouting material for shield tunnels according to claim 1, characterized in that, In step S3, a load sensor is used to collect the gravity change of the simulated segment in the grouting slurry.

5. The method for characterizing the floating control effect of the synchronous grouting material for shield tunnels according to claim 1, characterized in that, In step S3, the simulated segment is horizontally arranged, and a rigid rod is fixedly connected to the lower pipe wall of the simulated segment, and the other end of the rigid rod is connected to the load sensor.

6. The method for characterizing the floating control effect of the synchronous grouting material for shield tunnels according to claim 1, wherein In step S4, the method for drawing the buoyancy-displacement change curve of the simulated segment within the time range of 0 to T includes the following: Based on the time node when the displacement change in the displacement-time correction curve 2 tends to be stable, it is used as the determination time node T for the loss of the upward buoyancy of the grouting slurry. The magnitude of the upward buoyancy F1 corresponding to the loss time node T is obtained through the upward buoyancy-time change curve 3. The acting force at the initial moment in the upward buoyancy-time change curve 3 is denoted as F0. Plotting is performed based on the displacement change data within the time period of 0 to T in the displacement-time correction curve 2 and the acting force change data from F0 to F1 in the upward buoyancy-time change curve 3 to obtain the upward buoyancy-displacement change curve of the simulated segment within the time of 0 to T.

7. The characterization method of the floating control effect of the synchronous grouting material for shield tunnels according to claim 1, characterized in that, The simulated segment is made of a hollow cylindrical metal and always moves up and down in the vertical direction during the test, and the simulated segment is horizontally arranged.

8. The characterization method for the floating control effect of the synchronous grouting material for shield tunnels according to claim 7, characterized in that, A vertical transmission rod is fixedly connected to the upper pipe wall of the simulated segment. The transmission rod is arranged through a vertically fixedly arranged linear bearing to restrict the up and down movement of the simulated segment in the vertical direction, and a counterweight platform is arranged at the top of the transmission rod for configuring and adding counterweights for simulating the constraint force of the shield shell of the shield machine.

Images