Test method for representing floating control effect of shield tunnel synchronous grouting material
By simulating the displacement and load changes of tunnel segments in grout, and combining this with calculus calculations of the work done by the buoyancy of the grout, the problem of difficulty in determining the buoyancy control effect of grouting materials in shield tunnels was solved, enabling accurate evaluation of grout performance and reduction of construction costs.
Patent Information
- Application Number
- CN202411155447.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-22
- Publication Date
- 2026-03-03
AI Technical Summary
Existing technologies cannot effectively characterize the buoyancy control effect of synchronous grouting materials in shield tunnels. In particular, they cannot accurately determine the buoyancy loss process of grout when the grout properties change dynamically, which leads to serious problems of segment floating and affects tunnel construction safety and cost.
By simulating the displacement and load changes of tunnel segments in slurry, and combining the principles of calculus to calculate the work done by the buoyancy of the slurry, the time point of loss of buoyancy of the slurry is determined, the buoyancy control effect of the slurry is evaluated, and the influence of slurry shrinkage and deformation is considered. The operation is simple and low cost.
It enables precise assessment of slurry performance differences, provides a clearer reflection of buoyancy control effects, reduces construction costs and operational complexity, and improves the safety and efficiency of tunnel construction.
Smart Images
Figure CN121595845A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of building material testing technology, specifically relating to a test method for characterizing the buoyancy control effect of synchronous grouting materials in shield tunnels. Background Technology
[0002] Shield tunneling is widely used in the construction of underground spaces such as urban subways and river-crossing tunnels, and the diameter of shield tunnels is showing a continuous increasing trend. According to the construction principles of shield tunneling and the stress state of the formed segments, the buoyancy force on the formed segments of a shield tunnel increases with the segment diameter in a quadratic function, and the increase in buoyancy is far greater than the buoyancy resistance of the segment structure's own weight. As the excavation diameter of shield tunnels increases, the problem of segment floating becomes more prominent. After the segments are assembled and exit the shield tail, the buoyancy force they experience will increase exponentially. Severe segment floating can lead to segment cracking, threatening shield attitude control and increasing shield attitude deviation, causing difficulties in segment assembly, misalignment, or even damage, seriously affecting the tunnel's waterproofing effect and subsequent operational safety. Synchronous grouting materials for shield tunnels can play a role in controlling segment floating, reducing ground settlement, transferring loads, and constructing the first waterproof and seepage-resistant barrier.
[0003] During shield tunnel construction, the performance of grouting materials, grouting pressure, grouting volume, and tunneling rate are often adjusted by real-time monitoring of the segment float. Controlling the performance of the grouting material is crucial for controlling segment float. However, directly measuring segment float in engineering projects to adjust grouting material performance carries certain technical risks, is time-consuming and labor-intensive, and increases construction costs. In contrast, simulating and evaluating grouting material performance differences in laboratory conditions is simpler, less costly, and provides sufficient technical experience and support for field operations. Typically, in laboratory settings, stress analysis is used to assess the buoyancy of simulated segments in grout, thereby comparing the float control effects of different grouts. Compared to inert slurries, the single-component or two-component slurries most commonly used at home and abroad are active slurries. After the slurry is injected into the gap between the tunnel segments, its properties change gradually. That is, the buoyancy and viscosity forces on the tunnel segments are dynamically changing. Both exist simultaneously and cannot be separated. Therefore, the simulated tunnel segment stress analysis method cannot clearly determine the buoyancy loss process of the slurry and cannot truly and effectively characterize the anti-buoyancy effect of the slurry. Summary of the Invention
[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a test method for characterizing the buoyancy control effect of synchronous grouting materials in shield tunnels. By simulating the displacement and load changes of tunnel segments in grout, the time point of buoyancy loss of grout is determined, and the work done by grout buoyancy is calculated to evaluate the buoyancy control effect of grout. This method can intuitively and accurately reflect the differences in grout performance and is simple to operate and low in cost.
[0005] To achieve the above objectives, the present invention is implemented using the following technical solution:
[0006] This invention provides a test method for characterizing the buoyancy control effect of synchronous grouting materials in shield tunnels, comprising the following steps:
[0007] Step S1: Prepare synchronous grouting slurry according to the preset material mix ratio requirements, immerse the simulated tunnel segment made of hollow cylindrical metal in the synchronous grouting slurry, and place counterweights on the simulated tunnel segment to simulate the shield shell constraint force of the tunnel boring machine, and detect and obtain the displacement-time change curve of the simulated tunnel segment under the action of buoyancy.
[0008] Step S2: Test and calculate the early shrinkage deformation caused by the shrinkage deformation of the grout itself under sealing conditions, and subtract the influence of the shrinkage deformation from the displacement-time change to obtain the displacement-time correction curve of the simulated segment under the action of buoyancy.
[0009] Step S3: Submerge the simulated segment in the grouting slurry and use a load sensor to collect the gravity change of the simulated segment in the grouting slurry to obtain the buoyancy time change curve of the simulated segment under the action of buoyancy.
[0010] Step S4: Use the time node in the displacement-time correction curve where the displacement change tends to stabilize as the time node T for determining the loss of buoyancy of the grout. Obtain the magnitude of the buoyancy corresponding to the time node T through the buoyancy-time change curve.
[0011] Step S5: Based on the displacement change and buoyancy change of the simulated segment within the time interval 0 to T, plot the buoyancy-displacement change curve of the simulated segment within the time interval 0 to T. Calculate the shaded area enclosed by the buoyancy-displacement change curve using the principle of calculus, and use this area as the work done by the buoyancy on the simulated segment to characterize the buoyancy control performance of the grouting slurry.
[0012] Within the time interval 0 to T, the smaller the work done, the smaller the simulated segment displacement, the smaller the buoyancy force, and the better the anti-buoyancy performance of the grouting slurry.
[0013] Furthermore, the method for configuring counterweights on the simulated tunnel segments to simulate the shield shell constraint force of the tunnel boring machine is as follows:
[0014] The initial buoyancy of the simulated tunnel segment in the grouting slurry is estimated based on the density of the grouting slurry and the external dimensions of the simulated tunnel segment.
[0015] By adding counterweights to the simulated tube segment, the sum of the weight of the simulated tube segment and the weight of the counterweights is made slightly less than the initial buoyancy force.
[0016] During the test, at certain time intervals, ranging from 1h to 2h, one-Nth of the counterweights added to the simulated tunnel segment are removed, where N is a positive integer not less than 5, until all counterweights are removed, in order to simulate the constraint force and attenuation process of the shield shell of the tunnel boring machine on the tunnel segment.
[0017] Furthermore, the method for obtaining the early shrinkage deformation of the grout is as follows:
[0018] The same grout used in the test was placed in a 100*100*100mm cubic mold. The mold was covered with a plastic film to keep the grout in a closed environment, preventing the grout from exchanging humidity with the outside environment. The temperature inside the mold was kept consistent with the ambient temperature during the test. The early shrinkage deformation of the grout was then collected and recorded in real time by a laser displacement sensor.
[0019] Furthermore, the buoyancy force is formed by the combined action of the slurry buoyancy, the slurry viscosity, the weight of the segment itself, and the weight of the counterweight used to simulate the shield shell constraint force.
[0020] Furthermore, the simulated tube segment remained vertically moving up and down throughout the test.
[0021] Furthermore, a vertical transmission rod is fixed to the top of the simulated tunnel segment, and the transmission rod passes through a vertically fixed linear bearing to restrict the simulated tunnel segment from moving up and down in the vertical direction. A counterweight platform is set at the top of the transmission rod to accommodate counterweights for simulating the shield shell constraint force of the tunnel boring machine.
[0022] Furthermore, a rigid rod is fixedly connected to the bottom of the simulated tube segment, and the other end of the rigid rod is connected to the load sensor.
[0023] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:
[0024] The present invention provides a test method for characterizing the buoyancy control effect of synchronous grouting materials in shield tunnels. First, it acquires the displacement changes of simulated tunnel segments under the influence of grout buoyancy. It also considers the problem of significant shrinkage deformation caused by bleeding and segregation due to poor grout quality, eliminating the influence of this on the displacement of the simulated tunnel segments to obtain more realistic test data reflecting the grout buoyancy control effect. Based on this, combined with the stress analysis test data of the simulated tunnel segments in the grout, the magnitude of the buoyancy force exerted on the simulated tunnel segments by grout with different performance characteristics and the law of buoyancy loss can be studied. Simultaneously, the formation and evolution law of the internal microstructure of the grout can be studied, providing theoretical guidance for establishing a rapid determination method for grout setting time, which is a crucial time node for determining the phase transition of its internal structure. By jointly analyzing the displacement and load changes of simulated tunnel segments in the grout, the time node of grout buoyancy loss is obtained. The work done by the grout buoyancy force at this stage is calculated to evaluate the buoyancy control effect. This method can more clearly and accurately reflect the differences in grout performance and is simple to operate and low in cost. Attached Figure Description
[0025] Figure 1 This is a simulation of the segment displacement-time variation curve according to an embodiment of the present invention;
[0026] Figure 2 This is the early shrinkage deformation curve of the synchronous grouting material according to an embodiment of the present invention;
[0027] Figure 3 This is a modified simulated segment displacement time correction curve according to an embodiment of the present invention;
[0028] Figure 4 This is a simulation of the time-buoyancy change curve of the tube segment according to an embodiment of the present invention.
[0029] Figure 5 This is a simulation of the segment displacement-buoyancy change curve according to an embodiment of the present invention. Detailed Implementation
[0030] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.
[0031] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.
[0032] Example
[0033] In this embodiment of the invention, the buoyancy control effect of synchronous grouting material in shield tunnels was characterized using the following method, the specific steps of which are as follows:
[0034] (1) Prepare synchronous grouting material by mixing according to a specific mix ratio, immerse the simulated segment in the prepared grout, and detect the displacement change of the simulated segment under the combined action of grout buoyancy, grout viscosity, segment weight and counterweight used to simulate shield constraint.
[0035] Specifically, the above-mentioned synchronous grouting materials are prepared according to the materials and mixing ratios shown in Table 1. After the materials are mixed evenly, water is added and the mixture is stirred for 3 minutes in a mortar mixer to prepare the required grout.
[0036] In practical engineering applications, theoretically, the buoyancy of the tunnel lining segments is greatest after grouting is completed. However, the segment's upward buoyancy typically reaches its maximum value 2-3 rings after the segment has exited the shield tail. The main reason for this is that the shield shell of the tunnel boring machine exerts a certain restraining force on the segments, which gradually decreases as the machine advances.
[0037] Therefore, in order to more closely resemble the actual situation, the simulated tunnel segments are made of hollow cylindrical metal, which can be adjusted by adding or removing counterweights according to the design requirements of the buoyancy, and simulate the attenuation process of the tunnel segments under the constraint force of the shield shell.
[0038] Regarding the practice of adding initial counterweights to simulate tunnel segments and removing subsequent counterweights over time, specifically, in actual engineering, the buoyancy varies depending on the diameter of the tunnel segment and is approximately 2 to 3 times the weight of the tunnel segment itself.
[0039] Therefore, firstly, based on the slurry density and the external dimensions of the simulated tunnel segment, the initial buoyancy of the simulated tunnel segment is estimated. By controlling the counterweight of the simulated tunnel segment, the initial upward buoyancy is controlled to be approximately twice the self-weight of the simulated tunnel segment. At this point, the self-weight of the tunnel segment is M1. Then, by continuously adding counterweight, the self-weight of the tunnel segment is made slightly less than the initial upward buoyancy. The added counterweight is recorded as M2. Subsequently, every 1.5 hours, one-sixth of the added counterweight is removed from the tunnel segment (recorded as M0, M2 = 6M0), and all counterweights on the simulated tunnel segment are removed in six separate steps. After 9 hours, the self-weight of the simulated tunnel segment returns to M1.
[0040] Furthermore, to ensure the simulated tube segment moves vertically throughout the test, the cylindrical simulated tube segment is fixedly connected to the transmission rod and used in conjunction with a linear bearing. Under the buoyancy of the slurry, the simulated tube segment and transmission rod can slide freely up and down with minimal friction. The displacement-time curve (S0-T) of the simulated tube segment is collected using a displacement sensor, as shown below. Figure 1 As shown.
[0041] Table 1 shows the components and contents of the slurry mix proportions in the examples.
[0042] cement Bentonite fly ash sand water stabilizer 6.8wt% 5.1wt% 16.9wt% 50.8wt% 20.3wt% 0.1wt%
[0043] (2) Prepare the grout according to the mix proportions shown in Table 1, and test the early deformation data of the grout under sealing conditions. The method is as follows:
[0044] During testing, the slurry was placed in a 100*100*100mm cubic mold, and its surrounding surface was covered with a plastic film to ensure a sealed environment, preventing moisture exchange between the slurry and the external environment. The ambient temperature also needed to remain consistent with the ambient temperature during the test. Early deformation data of the slurry was collected using a laser displacement sensor. Figure 2 As shown.
[0045] Because the synchronous grouting material for shield tunnels is a system with a very high water-cement ratio, the grout has a high free water content, which makes it prone to bleeding and segregation. The grout also has a large shrinkage strain. Therefore, when using the grout displacement change curve to characterize the grout's buoyancy control effect on the tunnel segments, if the displacement change caused by the difference in grout's own shrinkage deformation is not considered, it will introduce errors into the experimental results.
[0046] Based on the simulated segment displacement variation curve, after subtracting the displacement variation caused by factors such as grout shrinkage and deformation, the corrected displacement-time variation curve S1-T of the simulated segment under grout buoyancy can be obtained, as shown below. Figure 3 As shown.
[0047] (3) Connect the simulated tunnel segment to the load sensor via a rigid rod. Prepare the grout according to the mix proportions shown in Table 1. Re-inject the prepared synchronous grout into the grout reservoir until the grout just submerges the simulated tunnel segment. Collect the gravity change of the simulated tunnel segment in the grout using the load sensor, calculate the buoyancy force on the simulated tunnel segment, and plot the buoyancy force-time curve (FT). Figure 4 As shown.
[0048] Specifically, an S-type strain gauge load cell with a range of 50N is used. This sensor can detect both positive pressure and negative tension.
[0049] (4) Combine the displacement and load change data of the simulated pipe segments to determine the time node of loss of buoyancy of the grout and the magnitude of the buoyancy effect corresponding to the time node, draw the buoyancy-buoyancy amount FS change curve in the time period, and calculate the work W done by the buoyancy of the grout on the pipe segments in the time period, so as to characterize the buoyancy control effect of grout with different performance.
[0050] The effectiveness of buoyancy control under different grout properties can usually be determined by two methods: the amount of segment buoyancy and the magnitude of buoyancy force. When the grout is first injected into the shield tail gap, it is almost in a liquid state, at which point the buoyancy force is at its maximum. However, throughout the grouting process, the properties of the grout are constantly changing, and the buoyancy force and viscous force acting on the simulated segments are also in a dynamic process. During the buoyancy force test, viscous resistance and buoyancy force cannot be distinguished or effectively separated.
[0051] In the initial stage, the simulated tunnel segments tend to move upwards under the influence of their own weight and the buoyancy of the grout. At this time, the viscous resistance of the grout on the segments is downwards. As time progresses, the grout cementitious material gradually hydrates, the internal structure of the matrix undergoes a slow phase change until it hardens, and the buoyancy of the grout gradually weakens. When the buoyancy is less than the weight of the simulated tunnel segments, the viscous resistance of the grout on the simulated tunnel segments may transform into an upward frictional force over time. In addition, due to the shrinkage of the grout itself, the stress process of the simulated tunnel segments becomes extremely complex, such as... Figure 4 As shown, the simulated tunnel segments are constantly changing under the buoyancy force of the grout, so the time point at which the buoyancy force disappears cannot be determined by the time-force curve. However, the magnitude of the initial buoyancy force of the grout and the rate at which it is lost are related to the overlying soil pressure and the counterweight. The greater the buoyancy force of the grout on the tunnel segments, the greater the counterweight required to counteract the buoyancy. The slower the buoyancy is lost, the longer the effect of the grout's buoyancy on the tunnel segments lasts, and the more difficult it is to control buoyancy.
[0052] Therefore, the technical solution provided by this invention determines the time point at which the buoyancy effect is lost by simulating the time-displacement curve of the tunnel segment, such as... Figure 3 As shown, the time point at which the simulated segment displacement tends to stabilize is designated as T1. This point is considered the point at which the slurry buoyancy is lost. The TI time point is... Figure 4 The corresponding force gauge is F1. Figure 4 The force gauge reading at the initial moment of the slurry is F0.
[0053] according to Figure 3 Displacement change data during the time period from T0 to T1 and Figure 4 Plotting the force variation data from F0 to F1, we can obtain the buoyancy-displacement curve FS of the simulated tunnel segment during the time period from 0 to T1. The shaded area of this region can then be calculated using calculus principles. Figure 5 As shown, W represents the work done by the slurry buoyancy force on the tunnel segment during this time period. The better the slurry's anti-buoyancy effect, the smaller the buoyancy force, the smaller the simulated tunnel segment displacement, and the smaller the calculated W value. Therefore, the W value can be used to characterize the buoyancy control effect of slurries with different properties on the tunnel segment.
[0054] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A test method for characterizing the buoyancy control effect of synchronous grouting materials in shield tunnels, characterized in that, Includes the following steps: Step S1: Prepare synchronous grouting slurry according to the preset material mix ratio requirements, immerse the simulated tunnel segment made of hollow cylindrical metal in the synchronous grouting slurry, and place counterweights on the simulated tunnel segment to simulate the shield shell constraint force of the tunnel boring machine, and detect and obtain the displacement-time change curve of the simulated tunnel segment under the action of buoyancy. Step S2: Test and calculate the early shrinkage deformation caused by the shrinkage deformation of the grout itself under sealing conditions, and subtract the influence of the shrinkage deformation from the displacement-time change to obtain the displacement-time correction curve of the simulated segment under the action of buoyancy. Step S3: Submerge the simulated segment in the grouting slurry and use a load sensor to collect the gravity change of the simulated segment in the grouting slurry to obtain the buoyancy time change curve of the simulated segment under the action of buoyancy. Step S4: Use the time node in the displacement-time correction curve where the displacement change tends to stabilize as the time node T for determining the loss of buoyancy of the grout. Obtain the magnitude of the buoyancy corresponding to the time node T through the buoyancy-time change curve. Step S5: Based on the displacement change and buoyancy change of the simulated segment within the time interval 0 to T, plot the buoyancy-displacement change curve of the simulated segment within the time interval 0 to T. Calculate the shaded area enclosed by the buoyancy-displacement change curve using the principle of calculus, and use this area as the work done by the buoyancy on the simulated segment to characterize the buoyancy control performance of the grouting slurry. Within the time interval 0 to T, the smaller the work done, the smaller the simulated segment displacement, the smaller the buoyancy force, and the better the anti-buoyancy performance of the grouting slurry.
2. The test method for characterizing the buoyancy control effect of synchronous grouting materials in shield tunnels according to claim 1, characterized in that, The steps for configuring counterweights on simulated tunnel segments to simulate the constraint forces of the tunnel boring machine's shield shell are as follows: The initial buoyancy of the simulated tunnel segment in the grouting slurry is estimated based on the density of the grouting slurry and the external dimensions of the simulated tunnel segment. By adding counterweights to the simulated tube segment, the sum of the weight of the simulated tube segment and the weight of the counterweights is made slightly less than the initial buoyancy force. During the test, at certain time intervals ΔT, where ΔT ranges from 1h to 2h, one-Nth of the counterweights added to the simulated tunnel segment are removed, where N is a positive integer not less than 5, until all counterweights are removed, in order to simulate the constraint force and attenuation process of the shield shell of the tunnel boring machine on the tunnel segment.
3. The test method for characterizing the buoyancy control effect of synchronous grouting materials in shield tunnels according to claim 2, characterized in that, The method for obtaining the early shrinkage deformation of the grout is as follows: The same grout used in the test was placed in a 100*100*100mm cubic mold. The mold was covered with a plastic film to keep the grout in a closed environment, preventing the grout from exchanging humidity with the outside environment. The temperature inside the mold was kept consistent with the ambient temperature during the test. The early shrinkage deformation of the grout was then collected and recorded in real time by a laser displacement sensor.
4. The test method for characterizing the buoyancy control effect of synchronous grouting materials in shield tunnels according to claim 1, characterized in that, The buoyancy force is formed by the combined action of the slurry buoyancy, the slurry viscosity, the weight of the tunnel segment itself, and the weight of the counterweight used to simulate the shield shell constraint force.
5. The test method for characterizing the buoyancy control effect of synchronous grouting materials in shield tunnels according to claim 1, characterized in that, The simulated tube segment remained vertical and moved up and down throughout the test.
6. The test method for characterizing the buoyancy control effect of synchronous grouting materials in shield tunnels according to claim 5, characterized in that, A vertical transmission rod is fixed to the top of the simulated tunnel segment, and the transmission rod passes through a vertically fixed linear bearing to restrict the vertical movement of the simulated tunnel segment. A counterweight platform is set at the top of the transmission rod to add counterweights to simulate the constraint force of the shield shell of the tunnel boring machine.
7. The test method for characterizing the buoyancy control effect of synchronous grouting materials in shield tunnels according to claim 1, characterized in that, A rigid rod is fixedly connected to the bottom of the simulated tube segment, and the other end of the rigid rod is connected to the load sensor.