A finely controlled deformation grouting process for deep-buried large-section tunnels

Abstract

The present invention relates to a grouting process for finely controlling deformation of a deep-buried large-section tunnel, comprising the following construction steps: (1) collecting engineering parameters of the deep-buried large-section tunnel, and modeling and simulating them to determine the construction parameters of the underground excavation; (2) running a calculation program to determine the grouting conditions during the underground excavation construction; (3) preparing grouting slurry; (4) underground excavation construction, grouting, real-time monitoring and adjustment; (5) after the underground excavation construction is completed and the slurry solidifies, testing the grouting effect. The present invention solves the problem that the existing underground excavation advance reinforcement method is not applicable to the working conditions of deep-buried large-section tunnels, which are prone to soil deformation and tunnel deformation, and can achieve good results in finely controlling deformation.

Description

Technical Field

[0001] The present invention relates to the technical field of underground engineering construction, and in particular to a finely controlled deformation grouting process for a deeply buried large-section tunnel. Background Art

[0002] Rail transit is developing rapidly. Due to the terrain characteristics and the terrain required for rail transit, rail transit designs often incorporate numerous tunnels. However, rail transit projects are characterized by short construction periods, high quality standards, and significant impacts on municipal facilities and residents' lives. This means that tunnel construction must not only minimize disturbance during underground excavation but also be fast.

[0003] The current methods for tunnel excavation include the full-section method, the step method, the middle partition wall method, the cross-middle wall method, and the double-side wall pilot tunnel method. The full-section method is characterized by full use of machinery, reduced manpower, and sequential excavation. It is suitable for dark excavation operations with small cross-sections and less stringent requirements for vibration generated during excavation. The step method is suitable for the construction of tunnels with large cross-sections and soft or broken rock structures, but its surrounding rock is poor and the process is complicated. The middle partition wall method, the cross-middle wall method, and the double-side wall pilot tunnel method have the problems of excessive temporary supports, uneconomical operation, inconvenient construction operation, reduced construction freedom, and the risk of force system conversion when removing temporary supports, which leads to limited support removal distance at one time.

[0004] Large-section tunnel projects are increasing day by day. For large-section tunnels in rail transit, the above methods are not well applicable. They are difficult to meet the requirements of small disturbance, fast construction, and applicability for large-section tunnel construction.

[0005] As a trenchless construction method for underground projects, underground excavation is crucial in urban areas with heavy traffic, dense populations, numerous surface buildings, and complex underground structures and pipelines. Its construction features minimal impact on surface traffic and pipelines in the soil, as well as minimal vibration and high speed during construction. However, soil deformation must be strictly controlled during construction.

[0006] Traditional soil deformation control measures use synchronous grouting, but it is difficult to strictly control complex strata, and there are no clear control and compensation measures for jacking sections that have already formed large settlements. Summary of the Invention

[0007] To address the aforementioned issues in the existing technology, the present invention provides a grouting process for finely controlling deformation in deep, large-section tunnels. This technology addresses the issues of soil and tunnel deformation that can easily occur in deep, large-section tunnels, making existing underground grouting reinforcement unsuitable. It achieves excellent results in finely controlling deformation.

[0008] To achieve the above-mentioned object, the present invention provides a finely controlled deformation grouting process for deep-buried large-section tunnels, comprising the following construction steps:

[0009] (1) Collect engineering parameters of deep-buried large-section tunnels and conduct modeling and simulation to determine the geological characteristics, stability state, and constitutive model of the tunnel. Apply different loads and add critical values ​​to define the safety critical value of the tunnel geological deformation, thereby determining the construction parameters of the underground excavation process.

[0010] (2) running a calculation program, inputting the construction parameters, performing calculation analysis on the modeling, and determining the grouting conditions of the tunnel excavation construction process based on the stable state of the tunnel geology, so as to precisely control the deformation of the tunnel geology;

[0011] (3) According to the grouting conditions, select appropriate raw material components and prepare grouting slurry that meets the requirements of deformation control;

[0012] (4) performing dark excavation construction according to the construction parameters, and injecting the grouting slurry into the space between the installed tunnel primary support structure and the geology through multiple pressure grouting devices at the same time, and performing real-time monitoring and adjustment during the grouting process to determine whether the grouting condition determined in step (2) is achieved;

[0013] (5) After the underground excavation and grouting are completed and the slurry solidifies, the grouting effect is tested to determine whether the final effect of fine deformation control is met.

[0014] Preferably, in step (1), the engineering parameters include the engineering geological conditions and hydrogeological conditions of the deep-buried large-section tunnel; the construction parameters include the geological internal pressure of the deep-buried large-section tunnel and the stress release of the underground excavation stratum.

[0015] In any of the above schemes, it is preferred that in step (2), the grouting conditions include grouting pressure, grouting volume, grouting thickness and slurry solidification strength; taking the stable state of tunnel geology as the benchmark means that the deformation of tunnel geology after grouting meets the design requirements, and even the tunnel geology after grouting is stronger than the theoretical stable state.

[0016] In any of the above schemes, preferably, in step (3), the grouting slurry includes the following components in parts by weight: 30-40 parts of pozzolana cement, 30-35 parts of double-fast cement, 25-30 parts of machine-made sand, 15-18 parts of sodium silicate, 8-12 parts of aluminum oxide powder, 5-10 parts of diethylpropylenediamine, 10-20 parts of hydroxypropyl methylcellulose, 3-5 parts of putrescine, 2-3 parts of Granham salt, 1-2 parts of naphthalenesulfonate formaldehyde condensate, 1-3 parts of polyacrylamide, and 3-5 parts of potassium sulfate.

[0017] In any of the above schemes, preferably, in step (4), the grouting pressure, grouting amount and grouting thickness are monitored and adjusted in real time according to the grouting conditions determined in step (2) during the grouting process, and the deformation of the tunnel geology is monitored in real time; the specific operation of monitoring and adjusting the grouting thickness is:

[0018] a. Before construction, ultrasonic sensors are used to transmit ultrasonic waves, and detection equipment is used to measure the propagation speed of ultrasonic waves in the air, within the tunnel primary support structure, within the grouting slurry, and within the tunnel geology.

[0019] b. During the grouting process, an ultrasonic sensor is placed at the tunnel's primary support structure and transmits ultrasonic waves radially upward along the tunnel. The ultrasonic waves sequentially reach the tunnel's primary support structure, the grouting slurry, and the tunnel geology. The propagation velocity of the ultrasonic waves is recorded in real time. When the propagation velocity value corresponds to the propagation velocity value within the grouting slurry, the ultrasonic wave is considered to have begun to reach the grouting slurry. When the propagation velocity value no longer corresponds to the propagation velocity value within the grouting slurry, the ultrasonic wave is considered to have left the grouting slurry.

[0020] c. Record the time interval between the ultrasonic wave starting to reach the grouting slurry and leaving the grouting slurry, multiply the time interval by the propagation velocity of the ultrasonic wave in the grouting slurry to obtain the distance the ultrasonic wave travels through the grouting slurry, which is the thickness of the grouting slurry;

[0021] d. Compare the thickness of the grouting slurry obtained in step c with the grouting thickness determined in step (2) to make adjustments in real time.

[0022] In any of the above schemes, it is preferred that in step (5), the detection of the grouting effect includes detecting the internal voids and solidification strength of the slurry after solidification, so as to determine whether the effect of finely controlling deformation is ultimately satisfied.

[0023] The beneficial effects of the present invention are:

[0024] 1. The present invention solves the problem that the existing underground excavation advance reinforcement grouting method is not applicable to the working conditions of deep burial and large sections, and is prone to soil deformation and tunnel deformation, and can achieve good results in fine control of deformation.

[0025] 2. The present invention improves the grouting slurry, significantly improves its early strength, significantly shortens the setting time, greatly improves the slurry quality and bonding properties, and greatly improves the construction performance and economic benefits of the project; by adopting automated, full-section grouting, the construction quality and efficiency are effectively guaranteed.

[0026] 3. The slurry of the present invention has the characteristics of short and controllable setting time, high early strength, high stability, high bonding strength, etc., and has good pumpability; it compensates for the deformation of the tunnel geology through grouting, effectively reduces and controls the geological deformation of the construction section, and even further strengthens the tunnel geology so that the deformation parameters meet the construction requirements; automatic operation and data collection, precise control of the injection volume and injection pressure, ensure the continuity and integrity of the grouting.

[0027] 4. During the grouting process, the present invention monitors and adjusts various grouting parameters and conditions in real time and accurately, thereby comprehensively and accurately ensuring the grouting effect, and can more intuitively and finely control the geological deformation of the tunnel, achieving a very good deformation control purpose and ensuring the safety of construction. DETAILED DESCRIPTION

[0028] The technical solution of the present application will be described in detail below in conjunction with the specific implementation methods of the present application, but the following examples are only for understanding the present invention. The embodiments and features in the embodiments of the present application can be combined with each other, and the present application can be implemented in a variety of different ways as defined and covered by the claims.

[0029] Example 1

[0030] A finely controlled deformation grouting process for deep-buried large-section tunnels includes the following construction steps:

[0031] (1) Collect engineering parameters of deep-buried large-section tunnels and conduct modeling and simulation to determine the geological characteristics, stability state, and constitutive model of the tunnel. Apply different loads and add critical values ​​to define the safety critical value of the tunnel geological deformation, thereby determining the construction parameters of the underground excavation process.

[0032] (2) running a calculation program, inputting the construction parameters, performing calculation analysis on the modeling, and determining the grouting conditions of the tunnel excavation construction process based on the stable state of the tunnel geology, so as to precisely control the deformation of the tunnel geology;

[0033] (3) According to the grouting conditions, select appropriate raw material components and prepare grouting slurry that meets the requirements of deformation control;

[0034] (4) performing dark excavation construction according to the construction parameters, and injecting the grouting slurry into the space between the installed tunnel primary support structure and the geology through multiple pressure grouting devices at the same time, and performing real-time monitoring and adjustment during the grouting process to determine whether the grouting condition determined in step (2) is achieved;

[0035] (5) After the underground excavation and grouting are completed and the slurry solidifies, the grouting effect is tested to determine whether the final effect of fine deformation control is met.

[0036] In step (1), the engineering parameters include the engineering geological conditions and hydrogeological conditions of the deep-buried large-section tunnel; the construction parameters include the geological internal pressure of the deep-buried large-section tunnel and the stress release of the underground excavation stratum.

[0037] In the step (2), the grouting conditions include grouting pressure, grouting volume, grouting thickness and slurry solidification strength; taking the stable state of tunnel geology as the benchmark means that the deformation of tunnel geology after grouting meets the design requirements, and even the tunnel geology after grouting is stronger than the theoretical stable state.

[0038] In step (3), the grouting slurry includes the following components in parts by weight: 30 parts of pozzolana cement, 35 parts of double-fast cement, 25 parts of machine-made sand, 18 parts of sodium silicate, 8 parts of aluminum oxide powder, 10 parts of diethylpropylenediamine, 10 parts of hydroxypropyl methylcellulose, 5 parts of putrescine, 2 parts of Granham salt, 2 parts of naphthalenesulfonate formaldehyde condensate, 1 part of polyacrylamide, and 5 parts of potassium sulfate.

[0039] In step (4), during the grouting process, the grouting pressure, grouting volume and grouting thickness are monitored and adjusted in real time according to the grouting conditions determined in step (2), and the deformation of the tunnel geology is monitored in real time; the specific operations for monitoring and adjusting the grouting thickness are:

[0040] a. Before construction, ultrasonic sensors are used to transmit ultrasonic waves, and detection equipment is used to measure the propagation speed of ultrasonic waves in the air, within the tunnel primary support structure, within the grouting slurry, and within the tunnel geology.

[0041] b. During the grouting process, an ultrasonic sensor is placed at the tunnel primary support structure and transmits ultrasonic waves radially upward along the tunnel. The ultrasonic waves will sequentially reach the tunnel primary support structure, the grouting slurry, and the tunnel geology. The propagation velocity of the ultrasonic waves is recorded in real time. When the propagation velocity value corresponds to the propagation velocity value within the grouting slurry, the ultrasonic wave is considered to have begun to reach the grouting slurry. When the propagation velocity value no longer corresponds to the propagation velocity value within the grouting slurry, the ultrasonic wave is considered to have left the grouting slurry.

[0042] c. Record the time interval between the ultrasonic wave starting to reach the grouting slurry and leaving the grouting slurry, multiply the time interval by the propagation velocity of the ultrasonic wave in the grouting slurry to obtain the distance the ultrasonic wave travels through the grouting slurry, which is the thickness of the grouting slurry;

[0043] d. Compare the thickness of the grouting slurry obtained in step c with the grouting thickness determined in step (2) to make adjustments in real time.

[0044] In the step (5), the grouting effect is tested, including the internal voids and solidification strength of the slurry after solidification, to determine whether the effect of finely controlling deformation is ultimately satisfied.

[0045] Example 2

[0046] In this embodiment, the grouting slurry includes the following components in parts by weight: 40 parts of pozzolana cement, 30 parts of double-fast cement, 30 parts of machine-made sand, 15 parts of sodium silicate, 12 parts of aluminum oxide powder, 5 parts of diethylpropylenediamine, 20 parts of hydroxypropyl methylcellulose, 3 parts of putrescine, 3 parts of Granham salt, 1 part of naphthalenesulfonate formaldehyde condensate, 3 parts of polyacrylamide, and 3 parts of potassium sulfate.

[0047] The other contents are the same as the technical features of Example 1.

[0048] Example 3

[0049] In this embodiment, the grouting slurry includes the following components in parts by weight: 35 parts pozzolana cement, 32 parts double-fast cement, 28 parts machine-made sand, 16 parts sodium silicate, 10 parts aluminum oxide powder, 8 parts diethylpropylenediamine, 15 parts hydroxypropyl methylcellulose, 4 parts putrescine, 2.5 parts Graham salt, 1.5 parts naphthalenesulfonate formaldehyde condensate, 2 parts polyacrylamide, and 4 parts potassium sulfate. The fineness modulus of the machine-made sand is 2.

[0050] The other contents are the same as the technical features of Example 1.

[0051] Example 4

[0052] In order to further improve the technical effect of the present invention, in this embodiment, in step (2), the grouting thickness is determined by the following formula:

[0053]

[0054] Where p is the maximum compressive strength of the tunnel's geology, T is the safety threshold for tunnel deformation, and r is the tunneling radius. The optimal grouting thickness is calculated to be 1.8m. The grouting volume is then V = H * L, where L is the tunneling length. This allows for precise control of grouting thickness and volume, ensuring both safety and effectiveness.

[0055] The grouting pressure is determined based on the safety threshold of tunnel geological deformation, set at 0.45-0.55 MPa. Based on the actual geological conditions or construction requirements, the grouting slurry's solidification strength after grouting should ensure that the tunnel geological deformation meets the design requirements. Ideally, the tunnel geological conditions after grouting should be stronger than the theoretical stable state. During the grouting process, the deformation of the tunnel's primary support structure and the tunnel geological conditions inside the tunnel should be closely monitored. Grouting should be stopped immediately if the deformation exceeds the design allowable value.

[0056] Six grouting ports are evenly spaced axially along the primary support structure of the tunnel. These ports are connected to the grouting pipeline, and each port is equipped with a flow control device to monitor and control the grouting pressure and volume through each port. During grouting, as underground excavation progresses, grouting is injected through these ports between the outer surface of the primary support structure and the tunnel geology, and the grouting progress is monitored at all times.

[0057] The process of this embodiment can utilize the strength of the grouting slurry to improve the geological bearing capacity and achieve the purpose of finely controlling deformation. By real-time monitoring of the grouting situation, timely adjustments can be made to provide effective, timely and reliable guidance for the next grouting step, and the construction process can be continuously optimized based on the detection to improve the construction quality.

[0058] When preparing grouting slurry,

[0059] 1) Stir the pozzolana cement, machine-made sand, diethylpropylenediamine, Granham salt and naphthalenesulfonate formaldehyde condensate in the above-mentioned parts by weight at a speed of 1800-2000 rpm for 15-20 minutes, add an appropriate amount of water during the stirring process, mix well, and let it stand for 3 minutes;

[0060] 2) Add the above-mentioned parts by weight of double-fast cement, sodium silicate, hypromellose and putrescine again, stir at a speed of 2200-2400 rpm for 15-20 minutes, add appropriate amount of water during the stirring process, mix well, and let it stand for 3 minutes;

[0061] 3) Add the remaining components in the above parts by weight, stir at a speed of 3000-3500 rpm for 5-10 minutes, mix evenly, and let it stand for 10-15 minutes before grouting.

[0062] The grouting slurry prepared by the above process can ensure the full reaction of each component, maximize the comprehensive effect, and has the advantages of small water addition, increased setting time and strength of the slurry, and greatly improved work efficiency and quality.

[0063] The rest of the contents are the same as the technical features of Example 2.

[0064] Example 5

[0065] In order to further improve the technical effect of the present invention, in this embodiment, the internal voids of the slurry after solidification are detected, including the following steps:

[0066] 1) Under lighting conditions, use a microscopic camera to photograph the solidified slurry layer; convert the photographed image into a microscopic grayscale image and establish a database; the microscopic camera can be replaced with lenses of different magnifications as needed;

[0067] 2) Establishing the correspondence between the voids in the slurry layer and the grayscale value intervals in the database and marking them;

[0068] 3) Count the number of pixels in the grayscale value range representing voids in the microscopic grayscale image, establish a quantitative relationship between the void ratio and the number of pixels, and obtain the porosity of the solidified slurry layer.

[0069] After detecting the internal voids of the slurry after solidification, it is determined whether repair grouting is needed to make it reach the designed strength to further ensure the effect of controlling deformation.

[0070] This method eliminates the need for laboratory testing and instead directly conducts on-site video evaluation of the slurry layer after solidification, improving test accuracy. It allows for real-time detection of the slurry layer's condition after solidification, enabling more accurate identification. Furthermore, the method is rapid and easy to operate, improving detection efficiency and providing faster real-time data analysis technology.

[0071] In addition, in step (1), MIDAS-GTS software modeling was used for computational analysis.

[0072] The rest of the contents are the same as the technical features of Example 3.

[0073] In addition, in order to ensure the technical effect of the present invention, the technical solutions of the above embodiments can be reasonably combined.

[0074] test

[0075] 1. Slurry performance test

[0076] The following performance tests were performed on the grouting slurries configured in Examples 1-5 respectively.

[0077] Setting time test: According to GBT 50080-2002 Standard for Test Methods of Performance of Ordinary Concrete Mixtures, the initial setting time and final setting time are tested.

[0078] Compressive strength test: According to GB / T 50010 “Test methods for mechanical properties of ordinary concrete”, slurry specimens were prepared and the compressive strength of the specimens was tested after curing for 2 hours under standard conditions.

[0079] sample Initial setting (min) Final setting (min) Compressive strength 2h Examples 1-5 15-18 20-25 38.3-40.1 Prior art slurry 36-40 50-55 18.5-19.9

[0080] As can be seen from the above table, the slurry of the present invention has a fast setting time, high strength, and good self-compacting properties, which greatly saves construction operation time and improves work efficiency.

[0081] 2. Control deformation effect test

[0082] Geological subsidence control Tunnel convergence deformation Tunnel Floating Misalignment Specified value -3cm~-5cm 5mm~10mm 10cm~20cm <5cm Examples 1-5 <-1.5cm 2mm~3mm 2cm~3cm <1.5cm

[0083] It can be seen from the above table that the method of the present invention has a good effect of controlling geological deformation.

[0084] It can be seen from the above embodiments that the present invention solves the problems that the existing grouting method is not applicable to deep-buried large-section working conditions and is prone to soil deformation and tunnel deformation, and can achieve good results in finely controlling deformation.

[0085] The present invention improves the grouting slurry, significantly improves its early strength, significantly shortens the setting time, greatly improves the slurry quality and bonding properties, and greatly improves the construction performance and economic benefits of the project; by adopting automated, full-section grouting, the construction quality and efficiency are effectively guaranteed.

[0086] The slurry of the present invention has the characteristics of short and controllable setting time, high early strength, high stability, high bonding strength, etc., and has good pumpability; it compensates for the deformation of tunnel geology through grouting, effectively reduces and controls the geological deformation of the construction section, and even further strengthens the tunnel geology so that the deformation parameters meet the construction requirements; automatic operation and data collection, precise control of injection volume and injection pressure, ensure the continuity and integrity of grouting.

[0087] The present invention ensures the grouting effect comprehensively and accurately by real-time and precise monitoring and adjustment of various grouting parameters and conditions during the grouting process, can more intuitively and finely control the geological deformation of the tunnel, achieves the purpose of very good deformation control, and ensures the safety of construction.

[0088] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

Claims

1. A finely controlled deformation grouting process for deep-buried large-section tunnels, characterized in that: The construction steps include: (1) Collect engineering parameters of deep-buried large-section tunnels and conduct modeling and simulation to determine the geological characteristics, stability state, and constitutive model of the tunnel. Apply different loads and add critical values ​​to define the safety critical value of the tunnel geological deformation, thereby determining the construction parameters of the underground excavation process. (2) Run the calculation program, input the construction parameters, perform calculation analysis on the model, and determine the grouting conditions during the tunnel construction process based on the stable state of the tunnel geology to precisely control the deformation of the tunnel geology; (3) According to the grouting situation, select appropriate raw material components and prepare grouting slurry that meets the requirements of deformation control; the grouting slurry includes the following components in parts by weight: 30-40 parts of pozzolana cement, 30-35 parts of double-fast cement, 25-30 parts of machine-made sand, 15-18 parts of sodium silicate, 8-12 parts of aluminum oxide powder, 5-10 parts of diethylpropylenediamine, 10-20 parts of hydroxypropyl methylcellulose, 3-5 parts of putrescine, 2-3 parts of Granham salt, 1-2 parts of naphthalenesulfonate formaldehyde condensate, 1-3 parts of polyacrylamide, and 3-5 parts of potassium sulfate; (4) Conducting underground excavation according to the construction parameters, and injecting grouting slurry into the space between the installed tunnel primary support structure and the geology through multiple pressure grouting devices at the same time, and conducting real-time monitoring and adjustment during the grouting process to determine whether the grouting conditions determined in step (2) are achieved; (5) After the underground excavation and grouting are completed and the slurry solidifies, the grouting effect is tested, including the internal voids and solidification strength of the slurry after solidification, to determine whether the final effect of fine deformation control is met; the internal voids are tested specifically as follows: 1) Under lighting conditions, use a microscopic camera to photograph the solidified slurry layer; convert the photographed image into a microscopic grayscale image and establish a database; the microscopic camera can be replaced with lenses of different magnifications as needed; 2) Establish the correspondence between the voids in the slurry layer and the grayscale value intervals in the database and mark them; 3) Count the number of pixels in the grayscale value range representing voids in the microscopic grayscale image, establish a quantitative relationship between the void ratio and the number of pixels, and obtain the porosity of the solidified slurry layer.

2. The finely controlled deformation grouting process for deep-buried large-section tunnels according to claim 1 is characterized in that: In the step (1), the engineering parameters include the engineering geological conditions and hydrogeological conditions of the deep-buried large-section tunnel; the construction parameters include the geological internal pressure of the deep-buried large-section tunnel and the stress release of the underground excavation stratum.

3. The finely controlled deformation grouting process for deep-buried large-section tunnels according to claim 2 is characterized in that: In the step (2), the grouting conditions include grouting pressure, grouting volume, grouting thickness and slurry solidification strength; taking the stable state of the tunnel geology as the benchmark means that the deformation of the tunnel geology after grouting meets the design requirements.

4. The finely controlled deformation grouting process for deep-buried large-section tunnels according to claim 3 is characterized in that: In the step (2), taking the stable state of the tunnel geology as a benchmark means that the geological condition of the tunnel after grouting is stronger than the theoretical stable state.

5. The finely controlled deformation grouting process for deep-buried large-section tunnels according to claim 3 or 4, characterized in that: In step (4), during the grouting process, the grouting pressure, grouting volume and grouting thickness are monitored and adjusted in real time according to the grouting conditions determined in step (2), and the deformation of the tunnel geology is monitored in real time; the specific operations for monitoring and adjusting the grouting thickness are: a. Before construction, ultrasonic sensors are used to transmit ultrasonic waves, and detection equipment is used to measure the propagation speed of ultrasonic waves in the air, within the tunnel primary support structure, within the grouting slurry, and within the tunnel geology. b. During the grouting process, an ultrasonic sensor is placed at the tunnel's primary support structure and transmits ultrasonic waves radially upward along the tunnel. The ultrasonic waves sequentially reach the tunnel's primary support structure, the grouting slurry, and the tunnel geology. The propagation velocity of the ultrasonic waves is recorded in real time. When the propagation velocity value corresponds to the propagation velocity value within the grouting slurry, the ultrasonic wave is considered to have begun to reach the grouting slurry. When the propagation velocity value no longer corresponds to the propagation velocity value within the grouting slurry, the ultrasonic wave is considered to have left the grouting slurry. c. Record the time interval between the ultrasonic wave starting to reach the grouting slurry and leaving the grouting slurry, multiply the time interval by the propagation velocity of the ultrasonic wave in the grouting slurry to obtain the distance the ultrasonic wave travels through the grouting slurry, which is the thickness of the grouting slurry; d. Compare the thickness of the grouting slurry obtained in step c with the grouting thickness determined in step (2) to make adjustments in real time.

Images