Water jet tunneling method suitable for tunnel of five-center circular arch structure

Abstract

The invention relates to a water jet tunneling method suitable for a five-center dome structure tunnel. The water jet tunneling method comprises the following steps that S1, a jet cutting pre-experiment of a cutting area under a tunnel face is carried out according to tunnel design; s2, measuring the cutting depth D under different jet parameters; s3, according to the cutting depth D, cutting parameters are determined, and a cutting circuit diagram is designed based on the cutting parameters; s4, cutting operation is conducted on the lower cutting area according to the cutting circuit diagram; and S5, cutting operation is conducted on the upper cutting area according to the cutting circuit diagram. According to the method, efficient, accurate, safe and reliable tunneling of the tunnel of the five-center circular arch structure is achieved, the construction quality can be improved, adaptability is enhanced, and the construction cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel engineering, and in particular to a water jet excavation method for a tunnel surface with a five-center circular arch structure. Background Art

[0002] As tunnel construction continues to expand in my country, tunnel types are becoming increasingly diverse. Five-center circular arch tunnels, due to their superior structural performance and ability to adapt to complex geological conditions, are widely used in various major tunnel projects. However, the excavation of five-center circular arch tunnels faces numerous technical challenges, and existing excavation methods have numerous shortcomings, making it difficult to meet the growing demand.

[0003] The traditional drill-and-blast method of tunneling for five-center circular arch structures results in serious over-excavation and under-excavation, leading to large subsequent support projects and increased costs. Construction is also characterized by high noise and dust levels, adversely affecting the health of construction workers and the surrounding environment. The surrounding rock is significantly disturbed, potentially causing instability and compromising construction safety. While shield tunneling technology enables continuous excavation, it carries high equipment operating and maintenance costs, is less adaptable to the unique cross-sectional shape of five-center circular arch tunnels, and is subject to significant construction space restrictions. TBM tunneling technology also presents some challenges, including severe tool wear, frequent tool replacement, and difficulty maintaining it, significantly increasing construction costs. Furthermore, the TBM method has high requirements for the construction environment and is less adaptable to certain special geological conditions, making it difficult to fully realize its excavation efficiency.

[0004] In summary, existing tunneling methods have certain limitations in the construction of five-center circular arch tunnels, making it difficult to meet the requirements for efficient, precise, adaptable, low-cost, safe and reliable tunnel and underground engineering construction. Therefore, there is an urgent need to develop a new five-center circular arch tunneling technology to overcome the shortcomings of existing technologies, improve the construction quality and efficiency of five-center circular arch tunnels, reduce construction costs, ensure construction safety, and promote the further development of tunnel engineering construction.

[0005] For example, patent document CN113153336A discloses a high-pressure abrasive water jet tunneling method. This method uses an axial nozzle to spray abrasive water jets to divide the tunnel face into a grid, and radial nozzles to spray abrasive water jets to radially cut and spall rock at the bottom of the slots. Although this method can achieve full hydraulic cutting and spalling of rock blocks at the tunnel face, it still has the following disadvantages: (1) During tunnel excavation, nozzles need to be frequently switched or replaced, which complicates the excavation process and is not conducive to continuous tunnel excavation; (2) The slots cut by the axial nozzles may close under the action of ground stress, making it impossible for the radial nozzles to enter the slots; (3) When the axial nozzle abrasive water jet cuts the tunnel face with bedding, weak interlayers or complex lithology, the depth of each seam varies greatly, and there may be a large number of repeated cutting paths.

[0006] Another example is a bread-and-bread jet tunneling method for hard rock tunnels, disclosed in patent document CN117418850A. This method uses a camera to capture rock images at the tunnel face, deriving the distribution characteristics of different rocks on the tunnel face based on color and creating a virtual roadmap. A linear abrasive water jet is used to cut the tunnel face traces, a rotary abrasive water jet is used for drilling, and a radial abrasive water jet is used for rotary cutting and exfoliation of the tunnel face rock. While this method can achieve precise hydraulic cutting of tunnel faces in complex strata, it still suffers from the following drawbacks: (1) The dust and water mist generated during tunnel excavation can easily block the camera lens, making it difficult to ensure the quality of the rock sample images obtained; (2) Abrasives are easily accumulated at the nozzle of the radial abrasive water jet emitter, causing the nozzle to be blocked, requiring manual unblocking or replacement of the nozzle, which in turn affects the construction period. Summary of the Invention

[0007] The purpose of the present invention is to provide a water jet excavation method suitable for a five-center circular arch structure tunnel, which can realize efficient, accurate, safe and reliable excavation of the five-center circular arch structure tunnel, and can improve the construction quality, enhance adaptability and reduce construction costs.

[0008] The water jet excavation method for a five-center circular arch structure tunnel according to the present invention comprises: S1. Based on the five-center arch tunnel structure, the semicircular area of ​​the tunnel face is considered the upper cutting zone, and the entire area below it is the lower cutting zone. Based on the tunnel construction design, abrasive water jet pre-cutting experiments were conducted under different jet parameters. Abrasive was sprayed from a nozzle to cut the contour line of the tunnel's lower cutting zone. The water jet has flexible transmission and strong adaptability, making it suitable for tunnel excavation in various complex environments. Operators can control the water jet from a distance, improving construction safety. Water can absorb dust to a large extent and wet the rock to a certain extent, effectively reducing noise and dust.

[0009] S2. After pre-cutting is completed and the rock has cooled, measure the cutting depth D under different jet parameters.

[0010] S3. Based on the cutting depth D obtained from the pre-cutting experiment, cutting parameters were determined, and a cutting route diagram was designed based on these cutting parameters. The cutting route diagram included a first-ring straight cutting route, a first-ring oblique cutting route in the lower cutting area, a second-ring straight cutting route in the lower cutting area, an oblique cutting route in the lower cutting area, a frustum segment route, an upper-cutting area contour route, a semicircular inner parallel cutting route, and a semicircular outer straight cutting route. Cutting methods included parallel cutting, straight cutting, and oblique cutting. By determining various parameters through pre-cutting experiments and drawing a cutting route diagram, precise cutting of the tunnel face was achieved, improving excavation accuracy, effectively controlling over-excavation and under-excavation, and reducing subsequent support costs.

[0011] S4. Cut the lower cutting area according to the cutting route diagram. First, cut along the first straight cutting route and the first oblique cutting route of the lower cutting area. After the cutting operation is completed, the first cutting route will cause rock to peel off. Secondly, cut along the second straight cutting route and the second oblique cutting route of the lower cutting area. After the cutting operation is completed, the second cutting route will cause rock to peel off. Thirdly, extend the cutting along the second straight cutting route and the second oblique cutting route of the lower cutting area. After the cutting operation is completed, the extended cutting will cause rock to peel off, and a frustum will be formed in the lower cutting area. Finally, cut along the frustum link route. After the cutting operation is completed, the frustum will cause rock to peel off. At this point, the lower cutting area has completed one excavation, and the footage is D sin α Gravity peeling can reduce the cutting distance of rock falling, reduce construction costs, improve jet tunneling efficiency, and simplify the process.

[0012] S5. Cut the upper cutting area according to the cutting line diagram. First, cut straight along the contour line of the upper cutting area. Then, cut parallel along the inner parallel cutting line of the semicircle. Finally, cut straight along the outer straight cutting line of the semicircle. After each cutting operation, a long strip of rock will fall. Its height is D sin α At this point, the upper cutting area has completed one excavation, with a footage of D sin α ; Repeat S5 until the upper cutting area is cut.

[0013] Optionally, in the S1 step, in the pre-cutting experiment, the cutting target distance between the nozzle and the cut surface is 20 mm to 40 mm, the abrasive is solid abrasive, and the solid abrasive is ceramsite, garnet or quartz sand with a concentration of 20% to 30%. Different jet pressures and different nozzle movement speeds are set to cut the overall contour of the cutting area.

[0014] Optionally, in S2, after pre-cutting is completed and the rock has cooled, a pulsed ultrasonic wave is emitted toward the rock cut using the transmitting end of the ultrasonic sensor. A timer is simultaneously initialized. When the receiving end of the ultrasonic sensor collects the ultrasonic wave reflected from the bottom interface of the rock, the timer is turned off, and the cutting depth D under different jet parameters is calculated based on the interval. Using an ultrasonic sensor for non-contact measurement enables rapid feedback on the jet cutting results when no one is present at the work surface, reducing labor costs and improving construction safety and reliability.

[0015] Optionally, in step S2, the transmitting power of the ultrasonic sensor is 20-50W and the frequency is 20-40kHz.

[0016] Optionally, in step S3, the cutting parameters include the cutting depth of the abrasive water jet. D and cutting angle α， The cutting angle α is the angle between the nozzle and the tunnel face, and the single excavation depth D sin α Greater than 0.5 D , and reserve the minimum length and cutting angle that can meet the requirements of the equipment for circular cutting of the cone parallel to the tunnel face. α satisfy, L The minimum length required to ensure that the nozzle cuts parallel to the tunnel face.

[0017] The present invention has the following advantages: 1. Benefiting from the flexible transmission characteristics of water jets, the present invention has strong adaptability and is suitable for tunnel excavation in various complex environments. Operators can control the system away from the working surface, thereby improving construction safety.

[0018] 2. The present invention uses abrasive water jet technology to accurately cut the tunnel face by setting different jet parameters, thereby improving excavation accuracy, effectively controlling over-excavation and under-excavation, and reducing subsequent support costs.

[0019] 3. The present invention uses an ultrasonic sensor to perform non-contact measurement of the jet cutting depth, and can quickly obtain feedback on the jet cutting results when there is no one on the working surface, thereby reducing labor costs and improving construction safety and reliability.

[0020] 4. The present invention utilizes gravity to peel off rock blocks, which can reduce the cutting distance for rock blocks to fall, reduce construction costs, and improve jet tunneling efficiency.

[0021] 5. The present invention makes full use of the structural characteristics of the five-center circle tunnel, and the process is simple. The semi-circular cylinder in the upper cutting area only needs to be cut twice before it can fall naturally.

[0022] 6. The present invention adopts an abrasive water jet rock breaking method, which causes little disturbance to the surrounding rock. In addition, for high-stress tunnels, jet cutting can achieve the effect of pressure relief and energy release, thereby realizing active control of surrounding rock deformation.

[0023] 7. The present invention uses water as the main cutting and excavation face throughout the process. Water can absorb dust to a large extent and soak the rock to a certain extent, effectively reducing noise, reducing dust, and preventing rock splashing and injuring people.

[0024] 8. Compared with the shield method and TBM method, the present invention has less equipment loss. Only the nozzle, water pipe and some metal materials are damaged by abrasive erosion or water action. In addition, the unit price of consumables is cheap, which greatly reduces the construction cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic flow chart of the face jet excavation method applicable to a five-center circle tunnel according to an embodiment of the present invention.

[0026] Figure 2 Schematic diagram of an abrasive water jet tunneling system in an embodiment of the present invention.

[0027] Figure 3 It is a schematic diagram of the upper and lower cutting areas and three cutting methods described in the present invention.

[0028] Figure 4 It is a schematic diagram of the tunnel face cutting drop ring and its cutting path according to the present invention.

[0029] Figure 5 It is a schematic diagram of the first round of cutting steps of the tunnel face and the cross section after cutting according to the present invention.

[0030] Figure 6 It is a schematic diagram of the first round of cutting steps of the tunnel face and the left view of the cross section after cutting according to the present invention.

[0031] Figure numerals: 1. Abrasive jet generating system, 101. Water tank, 102. Water, 103. High-pressure water pipe, 104. Engine, 105. High-pressure pump, 106. Overflow valve, 107. Throttle valve, 108. Check valve, 109. Abrasive tank, 110. Abrasive, 111. Mixing chamber, 112. Nozzle, 2. Remote control system, 201. Electronic pressure gauge, 202. Electronic flow meter, 203. Control box, 204. Computer, 205. Ultrasonic sensor, 206. Data line, 3. Upper cutting area, 301. Upper cutting area contour straight cutting line, 302. Semicircular inner parallel cutting line, 303. Semicircular outer straight cutting line, 4. Lower cutting area, 401. First ring straight cutting line of lower cutting area, 402. First ring oblique cutting line of lower cutting area, 403. Second ring straight cutting line of lower cutting area, 404. Second ring oblique cutting line of lower cutting area, 405. Cone ring cutting line, 5. Parallel cutting, 6. Straight cutting, 7. Oblique cutting, 8. First ring rock cutting, 9. Second ring rock cutting, 10. Extended rock cutting, 11. Cone cutting rock, 12. Long strip-shaped rock blocks. DETAILED DESCRIPTION

[0032] The following will describe the implementation of the technical solution of the present invention with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for the purpose of illustrating the invention and are not intended to limit the scope of protection of the invention.

[0033] like Figures 1 to 6 As shown, a water jet excavation method suitable for a five-center circular arch structure tunnel includes the following steps: S1. Based on the five-center circular arch tunnel structure, the semicircular area of ​​the tunnel face is considered the upper cutting zone 3, and the entire area below it is the lower cutting zone 4. Based on the tunnel construction design, abrasive water jet pre-cutting experiments were conducted under different jet parameters. Abrasive 110 was sprayed from nozzle 112 to cut the contour of the tunnel's lower cutting zone 4.

[0034] When conducting the abrasive water jet cutting preliminary experiment, first, different jet parameters are set through the remote control system 2, and then the abrasive jet generating system 1 is started through the control box 203, and the abrasive 110 is sprayed using the nozzle 112 to cut the contour line of the cutting area 4 under the tunnel.

[0035] Water jets are flexible in transmission and highly adaptable, making them suitable for tunnel excavation in a variety of complex environments. Operators can control the water jets from a distance from the working surface, which improves construction safety. Water can absorb dust to a large extent and soak the rocks to a certain extent, effectively reducing noise and dust.

[0036] S2. After pre-cutting is complete and the rock has cooled, measure the cutting depth D under different jet parameters, specifically: The transmitting end of ultrasonic sensor 205 emits pulsed ultrasonic waves toward the rock cut, simultaneously initializing a timer. When the receiving end of ultrasonic sensor 205 collects the ultrasonic waves reflected from the rock bottom interface, the timer is turned off. The cutting depth D under different jet parameters is calculated based on the interval. Using ultrasonic sensors for non-contact measurement enables rapid feedback on jet cutting results without human intervention, reducing labor costs and improving construction safety and reliability.

[0037] S3. Determine the cutting parameters based on the cutting depth D obtained from the pre-cutting experiment, and design the cutting route diagram based on the cutting parameters. Figure 4 The cutting line diagram includes the first ring straight cutting line 401, the first ring oblique cutting line 402 of the lower cutting area, the second ring straight cutting line 403 of the lower cutting area, the second ring oblique cutting line 404 of the lower cutting area, the frustum body segment line 405, the upper cutting area contour line 301, the semicircular inner parallel cutting line 302 and the semicircular outer straight cutting line 303. Among them, the cutting methods include parallel cutting 5, straight cutting 6 and oblique cutting 7. See Figure 3 .

[0038] By determining various parameters through pre-cutting experiments and drawing a cutting route map, precise cutting of the tunnel face was achieved, excavation accuracy was improved, over-excavation and under-excavation were effectively controlled, and subsequent support costs were reduced.

[0039] S4. Cutting operation is performed on the lower cutting area 4 according to the cutting line diagram, specifically: like Figures 3 to 6 As shown, firstly, cutting is performed along the first straight cutting line 401 of the lower cutting area and the first oblique cutting line 402 of the lower cutting area. After the cutting operation is completed, the first cutting rock 8 is peeled off (see Figure 5 and Figure 6 (I) in the figure); then, cutting is performed along the second straight cutting line 403 of the lower cutting area and the second oblique cutting line 404 of the lower cutting area. After the cutting operation is completed, the second cutting rock 9 is peeled off (see Figure 5 and Figure 6 (II) in the figure); again, the extended cutting is performed along the second straight cutting line 403 of the lower cutting area and the second oblique cutting line 404 of the lower cutting area. After the cutting operation is completed, the extended cutting rock 10 is peeled off (see Figure 5 and Figure 6 (III) in the figure), the lower cutting area 4 forms a truncated cone; finally, cutting is performed along the truncated cone segment line 405. After the cutting operation is completed, the truncated cone cut rock 11 is peeled off (see Figure 5 and Figure 6 (IV) in the figure), at this point, the lower cutting area 4 has completed one excavation, and the advance is Dsinα.

[0040] Gravity peeling can reduce the cutting distance of rock falling, reduce construction costs, improve jet tunneling efficiency, and simplify the process.

[0041] S5. Perform cutting operations on the upper cutting area 3 according to the cutting line diagram, specifically: like Figures 3 to 6 As shown, first, a straight cut 6 is performed along the upper cutting area contour line 301; secondly, a parallel cut 5 is performed along the semicircular inner parallel cut line 302; and finally, a straight cut 6 is performed along the semicircular outer straight cut line 303. After each cutting operation is completed, a long strip of rock 12 is dropped, and its height is Dsinα (see Figure 5 and Figure 6 (V) in the figure), so far, the upper cutting area 3 has completed one excavation, and the footage is Dsinα. Repeat the above steps until the upper cutting area 3 is cut (see Figure 5 and Figure 6 (VI) in the text.

[0042] After the cutting operations in the upper cutting area 3 and the lower cutting area 4 are completed, the excavation of a five-center circular arch structure tunnel section is completed.

[0043] This water jet excavation method, which is suitable for five-center circular arch structure tunnels, can achieve efficient, accurate, safe and reliable excavation of five-center circular arch structure tunnels, and can also improve construction quality, enhance adaptability, reduce construction costs, and promote the further development of tunnel engineering construction.

[0044] like Figure 1As shown, in one possible embodiment, an abrasive jet generating system 1 includes a water tank 101, water 102, a high-pressure water pipe 103, an engine 104, a high-pressure pump 105, a relief valve 106, a throttle valve 107, a check valve 108, an abrasive tank 109, abrasive 110, a mixing chamber 111, and a nozzle 112. The engine 104 is used to drive the high-pressure pump 105, supplying water from the water tank 101 to the mixing chamber 111 through the high-pressure water pipe 103. The relief valve 106 is used to discharge excess water back into the water tank 101. The throttle valve 107 is used to change the throttle cross-section to control the water flow rate. The check valve 108 is used to prevent water backflow. The abrasive tank 109 is used to temporarily store abrasive 110, which is mixed with water to enhance the rock-breaking capability of the jet. The mixing chamber 111 is used to mix water and abrasive. Nozzle 112 is used to eject the water and abrasive from mixing chamber 111. All components within the system are connected by a high-pressure water pipe 103, which transports water, abrasive, or a mixture of water and abrasive. This system features simple construction, low material and equipment costs, and minimal wear and tear, effectively reducing construction costs. The nozzle, water pipe, and some metal materials are not subject to wear and tear due to erosion by the abrasive or water, and the low unit price of consumables significantly reduces construction costs.

[0045] like Figure 1 As shown, in one possible embodiment, the remote control system 2 includes an electronic pressure gauge 201, an electronic flow meter 202, a control box 203, a computer 204, an ultrasonic sensor 205, and a data cable 206. The electronic pressure gauge 201 and the electronic flow meter 202 are respectively installed on the high-pressure water pipe 103, located between the throttle valve 107 and the check valve 108, and are used to monitor the pressure and flow of water in the high-pressure pipe 103, respectively. The computer 204 is connected to the electronic pressure gauge 201 and the electronic flow meter 202 via data cables to receive detection data. The computer 204 is connected to the ultrasonic sensor 205 via data cable 206 to receive data from the ultrasonic sensor 205. The computer 204 is connected to the control box 203 via data cable 206 for remote control. The control box 203 is connected to the engine 104 via data cable 206 to start the engine 104 and transmit data. This system is simple in structure, has low material and equipment costs, and minimizes losses, effectively reducing construction costs.

[0046] like Figure 1 As shown, in a possible embodiment, the abrasive 110 is composed of common solid abrasives such as ceramsite, garnet or quartz sand, and the concentration thereof is 20%-30%.

[0047] like Figure 1 As shown, in a possible embodiment, the cutting target distance between the nozzle 112 and the cut surface is 20 mm to 40 mm.

[0048] like Figure 1As shown, in a possible embodiment, in S2, the ultrasonic sensor 205 transmits power of 20-50 W and a frequency of 20 kHz-40 kHz.

[0049] like Figure 3 As shown, in one possible embodiment, the cutting parameters include the cutting depth of the abrasive water jet D and cutting angle α , cutting angle α is the angle between the nozzle and the tunnel face, and the single excavation depth D sin α Greater than 0.5 D , and reserve the minimum length and cutting angle that can meet the requirements of the equipment for circular cutting of the cone parallel to the tunnel face. α satisfy, L The minimum length required to ensure that the nozzle cuts parallel to the tunnel face.

[0050] like Figure 3 As shown, in a possible embodiment, the straight cut 6 is when the nozzle 112 cuts perpendicularly to the tunnel face, and the oblique cut 7 is when the nozzle 112 cuts at an angle of α Parallel cutting means that the nozzle 112 cuts parallel to the tunnel face.

[0051] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A water jet excavation method suitable for a five-center circular arch structure tunnel, characterized in that: The following steps are involved: S1. According to the five-center circular arch tunnel structure, the semicircular area of ​​the tunnel face is regarded as the upper cutting area (3), and the entire area below it is regarded as the lower cutting area (4); according to the tunnel construction design, an abrasive water jet pre-cutting experiment is carried out under different jet parameters, and the abrasive (110) is sprayed by the nozzle (112) to cut the contour line of the lower cutting area of ​​the tunnel; S2. After the pre-cutting is completed and the rock cools down, the cutting depth D under different jet parameters is measured; S3. Determine the cutting parameters according to the cutting depth D obtained from the cutting pre-experiment, and design a cutting route diagram based on the cutting parameters, wherein the cutting route diagram includes a first ring straight cutting route (401), a first ring oblique cutting route (402) in the lower cutting area, a second ring straight cutting route (403) in the lower cutting area, a second ring oblique cutting route (404) in the lower cutting area, a truncated cone segment route (405), an upper cutting area contour route (301), a semicircular inner parallel cutting route (302), and a semicircular outer straight cutting route (303); S4. According to the cutting line diagram, the lower cutting area (4) is cut. First, the cutting is performed along the first ring straight cutting line (401) and the first ring oblique cutting line (402) of the lower cutting area; secondly, the cutting is performed along the second ring straight cutting line (403) and the second ring oblique cutting line (404) of the lower cutting area; again, the cutting is extended along the second ring straight cutting line (403) and the second ring oblique cutting line (404) of the lower cutting area, and at this time, the lower cutting area (4) forms a truncated cone; finally, the cutting is performed along the truncated cone segment line (405). After the cutting operation is completed, the lower cutting area (4) completes one excavation, and the footage is D sin α ; S5. Cutting operation is performed on the upper cutting area (3) according to the cutting line diagram. First, straight cutting is performed along the upper cutting area contour line (301); secondly, parallel cutting is performed along the semicircular inner parallel cutting line (302); finally, straight cutting is performed along the semicircular outer straight cutting line (303); at this point, the upper cutting area (3) completes one excavation, and the advance is Dsinα; S5 is repeated until the upper cutting area (3) is cut.

2. The water jet excavation method for a five-center circular arch structure tunnel according to claim 1 is characterized in that: In the step S1, in the pre-cutting experiment, the cutting target distance between the nozzle (112) and the cut surface is 20 mm-40 mm; the abrasive is solid abrasive, and the solid abrasive is ceramsite, garnet or quartz sand, with a concentration of 20%-30%, and different jet pressures and different nozzle speed combinations are set to cut the overall contour of the lower cutting area (4).

3. The water jet excavation method applicable to a five-center circular arch structure tunnel according to claim 1, characterized in that: In S2, after the pre-cutting is completed and the rock is cooled, a pulse ultrasonic wave is emitted to the rock block cut seam using the transmitting end of the ultrasonic sensor (205), and a timer is initialized at the same time. When the receiving end of the ultrasonic sensor (205) collects the ultrasonic wave reflected back due to encountering the bottom interface of the rock block, the timer is turned off, and the cutting depth D under different jet parameters is calculated based on the interval time.

4. The water jet excavation method applicable to a five-center circular arch structure tunnel according to claim 3 is characterized in that: In the step S2, the transmitting power of the ultrasonic sensor (205) is 20-50W and the frequency is 20-40kHz.

5. The water jet excavation method applicable to a five-center circular arch structure tunnel according to claim 1, characterized in that: In the step S3, the cutting parameters include the cutting depth of the abrasive water jet. D and cutting angle α， The cutting angle α is the angle between the nozzle and the tunnel face, and the single excavation depth D sin α Greater than 0.5 D , and reserve the minimum length and cutting angle that can meet the requirements of the equipment to perform circular cutting of the cone parallel to the tunnel face. α satisfy, L The minimum length required to ensure that the nozzle cuts parallel to the tunnel face.

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