Advanced small guide pipe construction technology for circulating grouting

Abstract

The invention provides a circulating grouting advanced small guide pipe construction technology, and belongs to the technical field of surrounding rock construction, and the circulating grouting advanced small guide pipe construction technology comprises the following steps: S1, adopting a down-the-hole drill to form a double-ring hole in a tunnel wall; s2, inserting the slurry jetting pipe into the small guide pipe, exposing the tail end and connecting a slurry inlet pipe, connecting a grouting port of the small guide pipe with a steel gate valve for sealing, and connecting the tail part with a slurry return pipe through a three-way valve; s3, the prepared slurry enters a slurry storage barrel through a slurry inlet pipe, a slurry jetting pipe, a small guide pipe, a surrounding rock crack and a slurry return pipe, grouting is conducted on the tunnel vault from the two sides in two sequences, cement slurry is poured at the initial pressure of 0.5 MPa, stepped pressure increasing is conducted, and pressure increasing is stopped till the final pressure is reached; s4, in the grouting process, grouting data are collected in real time, and grouting parameters are regulated and controlled; and S5, after grouting is finished and mechanical hole sealing is conducted, manual filling and hole sealing are conducted, and the problem that the reinforcing effect of tunnel vaults and other parts is not ideal due to the fact that it is difficult to ensure that grout is evenly distributed in surrounding rock cracks through a traditional technology is solved.

Description

Technical Field

[0001] This invention belongs to the field of surrounding rock construction technology, and specifically relates to a pre-conduit construction process for cyclic grouting. Background Technology

[0002] In tunnel construction, pre-grouting with small guide pipes is a common pre-support method widely used in tunnel excavation under adverse geological conditions such as weak surrounding rock and fractured rock strata. It plays a crucial role in reinforcing the surrounding rock, controlling collapse, and preventing face instability. Traditional pre-grouting with small guide pipes typically involves inserting a grouting pipe into a small guide pipe and using a unidirectional grouting method. This means the grout is directly injected into the small guide pipe and into the surrounding rock fissures. Excess grout cannot be effectively returned or recycled, resulting in grout waste and high costs. Furthermore, the control of grouting pressure during the grouting process is not precise enough, easily leading to excessive pressure causing rock fracturing or insufficient pressure resulting in inadequate grouting, affecting grouting quality and tunnel support effectiveness.

[0003] Traditional techniques struggle to ensure uniform distribution of grout within the surrounding rock fissures, often resulting in densely grouted areas while other areas retain voids or weak points. This leads to unsatisfactory reinforcement of components such as the tunnel arch, failing to effectively improve the overall stability and bearing capacity of the surrounding rock. Therefore, a circulating grouting technique using advanced small-diameter guide pipes is designed. Summary of the Invention

[0004] This invention provides a pre-conduit construction process for cyclic grouting, which solves the problem that traditional processes cannot ensure the uniform distribution of grout in the surrounding rock fissures, and problems still exist in some areas, resulting in unsatisfactory reinforcement effects in parts such as the tunnel arch and failing to effectively improve the overall stability and bearing capacity of the surrounding rock.

[0005] In view of the above problems, the technical solution proposed by the present invention is as follows:

[0006] This invention provides a pre-conduit construction process for cyclic grouting, comprising the following steps:

[0007] S1, double-ring holes are drilled in the tunnel wall using down-the-hole drilling;

[0008] S2, insert the injection pipe into the small guide pipe, with the tail end exposed and connected to the grout inlet pipe. The grouting port of the small guide pipe is sealed with a steel gate valve, and the tail end is connected to the return grout pipe through a three-way valve.

[0009] S3. The prepared grout is introduced into the storage tank through the grout inlet pipe, grout injection pipe, small guide pipe, surrounding rock fissure, and grout return pipe. Grouting is carried out in two sequences from both sides to the tunnel arch. The cement grout is injected with an initial pressure of 0.5MPa and the pressure is increased in a stepwise manner until the final pressure is 3-5MPa, at which point the pressure increase is stopped.

[0010] S4, during the grouting process, collects grouting data in real time and adjusts grouting parameters;

[0011] S5, after grouting is completed and the hole is mechanically sealed, the hole is manually filled and sealed.

[0012] As a preferred technical solution of the present invention, the double ring hole in step S1 includes a first ring void and a second ring guide hole. The opening position of the first ring void is outside the designed tunnel outline, with an external insertion angle of 15°. The opening position of the second ring guide hole is inside the steel arch frame, with an external insertion angle of 10° to 15°. The first ring void and the second ring guide hole are staggered.

[0013] As a preferred embodiment of the present invention, the process of drilling double-ring holes in step S1 is as follows:

[0014] According to the skip drilling construction method, the first ring of empty holes is constructed first, and the excavation is carried out to the position of the next arch frame and the support is erected. The second ring of guide holes is constructed and the holes are cleaned.

[0015] As a preferred technical solution of the present invention, in step S2, the small guide tube is made of seamless steel pipe, and the grouting port end of the small guide tube is connected to a steel gate valve to seal the gap between the surrounding rock borehole and the small guide tube. The grouting pipe is a galvanized steel pipe and is set inside the small guide tube. The grout return pipe is a four-layer high-pressure steel wire pipe, and the grout return pipe is connected to the small guide tube through a three-way valve.

[0016] As a preferred technical solution of the present invention, the small guide tube is not perforated within 1m from the grouting port end, which is a hole-free section. The rear end is provided with plum blossom-shaped overflow holes at intervals of 25cm. The overflow holes are arranged in 6 rows of holes evenly in the circumference with the axis of the small guide tube as the reference. The axial spacing of each hole group is 25cm, and adjacent circumferential hole rows are arranged in a staggered manner.

[0017] As a preferred technical solution of the present invention, in step S3, the step pressurization is increased by 0.5 MPa every 5 minutes. The grouting pump includes a main pump and an auxiliary pump. When the pressure is ≤2 MPa, the main pump performs grouting. When the pressure is >2 MPa, the auxiliary pump is started to pressurize the return grout to the final pressure.

[0018] As a preferred technical solution of the present invention, in step S4, the grouting data is monitored by a pressure sensor installed at the three-way valve of the return grout pipe to monitor the actual pressure at the orifice. A flow meter and a density meter are installed in the pipe section from the grouting pump outlet to the injection pipe. The flow meter is used to measure the grout intake, and the density meter detects the grout density in real time. The grout pressure is released by a high-pressure valve installed on the return grout pipe.

[0019] As a preferred embodiment of the present invention, the process of first mechanically sealing the hole and then manually sealing the hole in step S5 is as follows:

[0020] After grouting, a hydraulic piston-type sealing pump is used for mechanical sealing, and a biodegradable mold bag is pre-placed in the borehole. The pressure value is taken as the final pressure value reached in step S3 and grouting is continued for 10 minutes. When the flow meter reading drops to the pre-designed flow rate, the pressure is stabilized for 2 minutes and the sealing operation is ended. Before the cement in the mechanically sealed borehole initially sets, manual sealing is performed. The borehole is cleaned with high-pressure air and finally mortar is injected.

[0021] As a preferred technical solution of the present invention, it also includes S6, in which, 24 hours after the sealing of the hole in step S5, an elastic wave test is used to check the grouting quality.

[0022] As a preferred embodiment of the present invention, the grouting quality inspection process in step S6 is as follows:

[0023] After the first ring of hollow holes is constructed, the first wave velocity test is conducted and the first set of data is recorded. After the second ring of guide holes is completed and grouting is completed, the second wave velocity test is conducted to generate the second set of data. The two sets of data are combined and a data table is generated. Finally, the data are compared and analyzed to calculate the lifting rate. If the lifting rate result is less than the lifting rate threshold K, additional grouting is performed until both the final pressure and the lifting rate threshold K are met.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] On the one hand, during the grouting process, the present invention uses a double-ring hole staggered arrangement combined with a small guide pipe plum blossom-shaped overflow hole and a multi-row staggered hole group to make the grout spread evenly, avoiding the problem of uneven distribution in traditional processes. At the same time, the step-by-step pressurization combined with the cooperation of the main and auxiliary pumps allows for fine control within a reasonable pressure range, ensuring that the grout fills the cracks and avoiding the hidden danger of excessive pressure, thereby improving the grouting quality and safety and enhancing the surrounding rock reinforcement effect.

[0026] On the other hand, this invention innovates the sealing process by combining mechanical and manual sealing to prevent grout leakage, ensuring the sealing quality and support effect of the small guide pipes. At the same time, the grouting effect is quantitatively evaluated by calculating the lift rate through elastic wave testing. If the standard is not met, local supplementary grouting is carried out, providing a solid guarantee for the subsequent tunnel construction, ensuring that the reinforcement quality meets the design requirements, and improving the reliability and durability of the tunnel.

[0027] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0028] Figure 1This is a schematic diagram of the construction process of advanced small guide pipe for cyclic grouting disclosed in this invention.

[0029] Figure 2 This is a schematic diagram of grout circulation in a pre-conduit construction process for circulating grouting disclosed in this invention.

[0030] Figure 3 This is a schematic diagram of the arrangement of double-ring holes in a pre-conduit construction process for circulating grouting disclosed in this invention.

[0031] Figure 4 This is a schematic diagram of the structure of the small guide pipe in the advanced small guide pipe construction process of cyclic grouting disclosed in this invention;

[0032] Explanation of reference numerals in the attached drawings: 1. Grout mixer; 2. Gate valve; 3. Grout storage tank; 4. Flow meter; 5. Main pump; 6. Grout inlet pipe; 7. Pressure sensor; 8. High-pressure valve; 9. Return grout pipe; 10. Auxiliary pump; 11. Densitometer; 12. Grouting data recorder; 13. First annular cavity; 14. Second annular guide hole; 15. Small guide pipe; 16. Grouting pipe; 17. Steel gate valve. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0035] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0036] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0037] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0038] Example 1

[0039] See attached document Figure 1-4 As shown, the present invention provides a technical solution: a pre-conduit construction process for circulating grouting, comprising the following steps:

[0040] S1. A down-the-hole drill is used to open a double-ring hole in the tunnel wall. The double-ring hole includes a first ring hole 13 and a second ring guide hole 14. The opening position of the first ring hole 13 is outside the designed tunnel outline, with an external insertion angle of 15°. The opening position of the second ring guide hole 14 is inside the steel arch, with an external insertion angle of 10° to 15°. The first ring hole 13 and the second ring guide hole 14 are spaced 200-300mm apart in the circumferential direction. The double-ring holes are staggered. The vertical spacing between the first ring hole 13 and the second ring guide hole 14 is 200mm. The front and rear spacing of the small guide 15 can be adjusted according to the arch spacing during on-site arrangement.

[0041] S2, insert the grouting pipe 16 into the small guide pipe 15, with the tail end exposed and connected to the grouting pipe 6. The grouting port of the small guide pipe 15 is sealed by the steel gate valve 17, and the tail end is connected to the return grouting pipe 9 through the three-way valve.

[0042] S3. The prepared grout enters the grout storage tank 3 through the grout inlet pipe 6, grout injection pipe 16, small guide pipe 15, surrounding rock fissures, and grout return pipe 9. Grouting is carried out in two sequences from both sides towards the tunnel arch. In accordance with the principle of internal reinforcement, weak areas are reinforced first. Cement grout is injected with an initial pressure of 0.5MPa and pressure is increased in stages until the final pressure is 3-5MPa. The pressure increase is stopped. The step pressure increase is 0.5MPa every 5 minutes. The grouting pump (grouting machine) includes a main pump 5 and an auxiliary pump 10. When the pressure is ≤2MPa, the main pump 5 is used for grouting. When the pressure is >2MPa, the auxiliary pump 10 is started. The working pressure range of the auxiliary pump 10 is 2-6MPa. To avoid overpressure, the return grout is pressurized a second time to the final pressure.

[0043] The main pump 5 is connected to the grouting pipe 16, and the inlet of the auxiliary pump 10 is connected to the grout storage tank 3, and the outlet is connected in parallel to the pipeline of the main pump 5. Together, they supply grout to the grouting pipe 16 to achieve the effect of pressurizing the pipeline. The pressure is read by the pressure sensor 7 in step S4. When the pressure of the main pump 5 is ≤2MPa, it works alone to reduce energy consumption. When the pressure is >2MPa, the auxiliary pump 10 is started. Because the volumetric efficiency of the main pump 5 is insufficient in the high pressure zone, the auxiliary pump 10 provides stable secondary pressurization to ensure that the parameters of the grout are controllable under the final pressure (3-5MPa).

[0044] S4, during the grouting process, collects grouting data in real time and adjusts grouting parameters;

[0045] S5, after grouting is completed and the borehole is mechanically sealed, the borehole is manually filled and sealed;

[0046] S6. 24 hours after the sealing of the hole in step S5, the grouting quality is checked by elastic wave testing.

[0047] The embodiments of the present invention are also implemented through the following technical solutions.

[0048] In an embodiment of the present invention, step S1, which involves drilling a double-ring hole, is as follows:

[0049] Following the skip drilling method, down-the-hole drills were used to drill the first ring of holes 13 along the tunnel outline. The first batch of holes were drilled in sequence, numbered 1, 5, 9... with a 3-hole interval. Temporary protective pipes with a diameter of 60mm were inserted to prevent hole collapse. The remaining holes were drilled. After the first ring of holes 13 was completed, the protective pipes were pulled out using a hydraulic pipe puller before the steel arch frame was erected. The tunnel face was then excavated to the next arch frame. After the initial support arch frame was erected, the second ring of guide pipe holes 14 were constructed. After drilling, the holes were cleaned. After cleaning, the small guide pipes 15 were installed. After installation, the area around the opening of the small guide pipe 15 was filled with cotton to prevent grout leakage during grouting. After the entire small guide pipe 15 was treated, the tunnel face was sealed with shotcrete again. Grouting was carried out after the shotcrete had gained strength.

[0050] In an embodiment of the present invention, in step S2, the small guide tube 15 is made of seamless steel pipe. The grouting port end of the small guide tube 15 is connected to a steel gate valve 17 to seal the gap between the surrounding rock borehole and the small guide tube 15, preventing grout from leaking along the borehole wall. The grouting pipe 16 is a galvanized steel pipe, which is installed inside the small guide tube 15. The front end of the grouting pipe 16 is 50cm away from the grouting port of the small guide tube 15, and the exposed length of the tail end is 50cm. The exposed part is used to connect the grouting pump inlet pipe 6. The grout return pipe 9 is a four-layer high-pressure steel wire pipe, and the grout return pipe 9 is connected to the small guide tube 15 through a three-way valve.

[0051] In an embodiment of the present invention, the small guide tube 15 is not perforated within 1m from the grouting port end, forming a perforated section. At the rear end, slurry overflow holes are opened in a plum blossom shape at intervals of 25cm. The overflow holes are arranged in 6 rows of holes evenly in the circumference with the axis of the small guide tube 15 as the reference. The axial spacing of each hole group is 25cm. Adjacent circumferential hole rows are arranged according to a staggered pattern. The hole diameter is designed according to a gradient change pattern. For example, a small hole diameter (8mm) is used in the high-pressure zone near the grouting port to suppress turbulence, a medium hole diameter (10mm) is used in the middle stable zone to improve permeability, and a micropore (2mm) is used in the low-pressure zone at the tail end to maintain back pressure and filter particulate matter. At the same time, the hole edges are chamfered.

[0052] In an embodiment of the present invention, the detailed process of cyclic grouting in step S3 is as follows:

[0053] The grout (ordinary silicate cement grout) is prepared in a mixer (or grouting tank) and stored in a storage tank 3. The grouting pump (main pump 5) is started, and the grout is pumped out of the storage tank 3. The grout enters the grouting pipeline system through the inlet pipe 6, flows through the grouting machine, and enters the small guide pipe 15 to begin injecting into the surrounding rock fissures. Under pressure, the grout enters the surrounding rock fissures. At the same time, some of the grout that is not injected into the surrounding rock, or when the grout absorption of the surrounding rock is less than the pumping rate, the excess grout will flow out through the return pipe 9 and return to the storage tank 3. In the initial stage, a relatively low pressure of 0.5 MPa is usually used to start grouting to avoid eroding the surrounding rock or clogging small fissures. Based on the grout absorption and geological conditions, the grouting pressure is gradually and slowly increased, and grouting is continued until the pressure reaches the designed final pressure (3-5 MPa). After reaching the final pressure, grout continues to flow steadily out of the return pipe 9 (indicating smooth circulation and saturation of the surrounding rock). Under the final pressure, the grout absorption rate per unit time (injection rate) decreases to the minimum value required by the design (e.g., less than 1 L / min). When the three conditions of final pressure, stable grout return, and grout absorption rate are met simultaneously (or the design-specified end criteria), the grout inlet valve and grout return valve are closed to complete the grouting of the hole. The grout flowing back from the return pipe 9 continues to return to the grout storage tank 3 to participate in the next cycle or be processed.

[0054] In an embodiment of the present invention, in step S4, the grouting data is monitored by a pressure sensor 7 installed on the return pipe 9 upstream of the three-way valve, i.e., on the side near the small guide pipe 15, to monitor the actual pressure at the orifice and prevent rock splitting. A flow meter 4 and a density meter 11 are installed in the pipe section from the grouting pump outlet to the injection pipe 16. A flow meter 4 is installed between the outlet of the main pump 5 and the inlet pipe 6 to measure the grout intake. A flow meter 4 is installed at the end of the return pipe 9, in front of the storage tank 3, to measure the return grout volume. A density meter 11 is installed at the inlet of the injection pipe 16 to detect the grout density in real time. The grout density is monitored by a high-pressure valve installed at the end of the return pipe 9. 8. Pressure relief: When the return grout pressure is greater than the inlet grout pressure, the automatic opening increases to relieve pressure and balance the pressure. When only the main pump 5 is working, the pressure relief threshold is 1.5 times the inlet grout pressure. When the auxiliary pump 10 is started, the pressure relief threshold is adjusted to 1.2 times the auxiliary pump working pressure. All sensors are connected to the grouting data logger 12 to store and analyze data in real time. The grouting data logger 12 is a conventional data logger, such as the OHR-PR50 data logger developed by Hongrun Company, which has multi-channel acquisition, control and recording, large capacity storage space, strong anti-interference ability, and dual channels of RS485 and Ethernet.

[0055] The monitoring process is as follows: A flow meter 4, a density meter 11, a pressure sensor 7, and a high-pressure valve 8 are installed in the grout return pipe 9. The grout storage tank 3 is in a low-pressure zone. When the reading of the pressure sensor 7 reaches the pre-designed final pressure (3-5MPa) and stabilizes for 10-15 minutes, and at the same time meets the requirements that the single-hole injection rate is not greater than 1L / min and the group-hole injection rate is not greater than 0.8L / min, the grouting continues for 30 minutes, and the grouting can be stopped. The grouting work must be carried out continuously. Throughout the process, the flow meter 4, density meter 11, and pressure sensor 7 are all connected to the automatic grouting recorder for data storage and analysis.

[0056] Among them, the single-hole injection rate is no more than 1L / min and (injection volume - return volume) ≤ 1, and the group-hole injection rate is no more than 0.8L / min and Σ(single-hole injection volume - return volume) ≤ 0.8.

[0057] The determination and handling of cross-contamination includes first distinguishing different cross-contamination conditions. If cross-contamination occurs in the first annular cavity 13, it is determined to be primary cross-contamination. At this time, the speed of the grouting pump should be reduced to 50% of the original speed to slow down the grout propulsion speed. Maintain the reduced speed and grout for 10 minutes to control the development of cross-contamination. If cross-contamination occurs in the second annular guide hole 14, it is directly determined to be severe cross-contamination. Before starting the hydraulic grout distributor, the auxiliary pump 10 is turned off and only the main pump 5 supplies grout. The hydraulic grout distributor is started for synchronous grouting.

[0058] The specific operating steps are as follows: Close the steel gate valve 17 at the grouting hole to prevent the grout from flowing out in a disorderly manner. Connect the inlet of the hydraulic grout distributor to the outlet of the main pump 5. Connect the outlet of the hydraulic grout distributor to the return pipe 9 of the grouting hole. Use a sealing ring to ensure a reliable connection seal. Adjust the flow distribution ratio of the grout distributor according to the hole diameter and the surrounding rock conditions, such as main hole: auxiliary hole = 6:4. Start the grouting pump and keep the total grout intake constant. Perform multi-hole synchronous grouting until the design final pressure (3-5MPa) is reached. The final pressure is stable for 10 minutes, and the single hole injection rate is ≤1L / min.

[0059] When grouting through blocked grouting holes: If the grouting pressure suddenly increases, such as a pressure rise of >2MPa / min, immediately shut down the grouting pump, determine if a blockage has occurred, and try to clear the grouting pipe by tapping or rolling the blocked area. If the blockage cannot be cleared, repair the pipe in time to ensure that the grouting system is unobstructed, close the grouting hole, and grout through the adjacent non-grouting hole so that the grout bypasses the grouting area and fills the ungrouted section.

[0060] When the grouting flow rate is large (greater than 30L / min) and the pressure remains constant, adjust the grout concentration (e.g., jump directly from 1:1 to 0.45:1 or 0.3:1), or add fiber material at 0.5%-1% of the cement mass to shorten the gelation time, or use low-flow, low-pressure grouting or intermittent grouting to allow the grout to have a relative residence time in the cracks and promote gelation.

[0061] If any sudden increase in pressure or abnormal grout volume occurs during the grouting process, it should be handled promptly in accordance with the above rules and procedures to ensure grouting quality and construction safety.

[0062] In an embodiment of the present invention, the process of first mechanically sealing the hole and then manually sealing the hole in step S5 is as follows:

[0063] After grouting, mechanical sealing is performed using a hydraulic piston-type sealing pump, and biodegradable formwork bags are pre-placed inside the borehole. After stabilizing the pressure for 10 minutes, the grouting of the biodegradable formwork bags is stopped. The final pressure is achieved through subsequent manual sealing. When the flow meter reading drops to the pre-designed flow rate, the sealing operation is stopped after stabilizing the pressure for 2 minutes. Before the initial setting of the cement in the mechanically sealed borehole, manual sealing is performed using micro-expansion mortar. The pressure inside the hole is increased to the final pressure value by tamping the reinforcing steel. The borehole is cleaned with high-pressure air (0.8MPa, for 30 seconds). Finally, mortar is injected to 2 / 3 of the hole depth, a 16cm diameter reinforcing steel bar is inserted and tamped, and secondary grouting is performed to the hole opening. The surface is then smoothed with a steel trowel to make it flush with the concrete surface.

[0064] The degradation time of the biodegradable formwork bag is ≤24h. The biodegradable formwork bag is used to limit the radial diffusion of the slurry and force axial filling. The material can be polylactic acid fiber woven mesh. The grouting pressure of the biodegradable formwork bag is ≥6MPa to ensure the structural integrity under the final pressure (3-5MPa). Grouting is stopped after stabilizing the pressure for 10 minutes. The biodegradable formwork bag of this material dissolves in 24h when the water temperature is >25℃. Specifically, after grouting and hole cleaning, the biodegradable formwork bag is inserted. The sealing pump injects grout into the biodegradable formwork bag. The radial expansion of the biodegradable formwork bag is restricted, and the slurry is axially advanced. The pressure inside the hole is raised to the final pressure value (3-5MPa) through secondary grouting. Then, manual sealing is performed.

[0065] In addition, when using PLA-PCL composite membrane in low-temperature regions (5°C), the degradation time is 36 hours.

[0066] In an embodiment of the present invention, the process of checking the grouting quality in step S6 is as follows:

[0067] After the first ring of hollow holes 13 is constructed, the first wave velocity test is conducted and the first set of data is recorded. After the second ring of guide holes 14 is completed and grouting is finished, the second wave velocity test is conducted, and the second set of data is generated. The two sets of data are combined and a data table is formed. Finally, the data are compared and analyzed, and the formula for calculating the lift rate is: Where η is the lifting rate, V1 is the reference wave velocity of the adjacent supported surrounding rock (≤2m from the test point), V2 is the test value at the same point 24 hours after grouting, and the lifting rate threshold K is preset according to the surrounding rock type. The value of K is set according to the surrounding rock type. If the calculated lifting rate η is less than K, it indicates that the grouting effect has not achieved the expected reinforcement effect. Then, the grouting and sealing process of steps S3-S5 is repeated in the corresponding area until the final pressure of 3-5MPa is met and η≥K.

[0068] The detailed steps for calculating the improvement rate through elastic wave testing are as follows: Arrange detection points at corresponding positions in the tunnel or structure, install sensors for measuring the elastic wave velocity, ensure the accurate installation position of the sensors and good contact with the measured object, ensure the normal operation of the testing equipment and stable connection of the sensors. Conduct elastic wave velocity testing after cleaning the first annulus hole 13 and before grouting, and record the initial wave velocity V1. Carry out grouting construction according to the design requirements, ensure that the grouting process complies with the process standards, and monitor parameters such as pressure and flow rate during the grouting process in real time to ensure the grouting quality. Each ring of holes is tested independently. Measure V2 for the first annulus hole 13 24 hours after grouting. Similarly, for the second ring of conduit holes 14, conduct the second elastic wave velocity testing, ensure that the testing conditions are the same as the initial testing, accurately record the subsequent wave velocity V2. Record the data of the initial wave velocity V1 and the subsequent wave velocity V2, ensuring the accuracy and integrity of the data. Calculate the improvement rate through the above improvement rate formula. If the improvement rate η≥K, it is considered that the grouting effect is good and no additional grouting is required. If η<K, it indicates that the grouting effect does not meet the expectation, and local grouting needs to be carried out in the corresponding area.

[0069] Among them, for the setting of the K value, for example, for Class I surrounding rock (such as intact granite), K = 10% - 12%;

[0070] for Class II - III surrounding rock (sandstone / shale), K = 12% - 15%;

[0071] for Class IV - V surrounding rock (fault fracture zone), K = 15% - 20%;

[0072] The specific K value needs to be calibrated on site in combination with the tunnel burial depth.

[0073] The above is only the preferred embodiment of the present invention and is not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0074] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process can be rearranged without departing from the protection scope of the present disclosure. The appended method claims present the elements of various steps in an exemplary order and are not intended to be limited to the specific order or hierarchy described.

[0075] In the detailed description above, various features are combined together in a single embodiment to simplify this disclosure. This approach to disclosure should not be construed as reflecting an intention that embodiments of the claimed subject matter require more features than are explicitly stated in each claim. Rather, as reflected in the appended claims, the invention is presented with fewer features than all of the features in a single disclosed embodiment. Therefore, the appended claims are hereby explicitly incorporated into the detailed description, with each claim representing a separate preferred embodiment of the invention.

[0076] Those skilled in the art will also understand that the various illustrative logic blocks, modules, circuits, and algorithm steps described in conjunction with the embodiments herein can be implemented as electronic hardware, computer software, or a combination thereof. To clearly illustrate the interchangeability between hardware and software, the various illustrative components, blocks, modules, circuits, and steps described above are generally described in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system. Those skilled in the art can implement the described functionality in alternative ways for each specific application; however, such implementation decisions should not be construed as departing from the scope of this disclosure.

[0077] The steps of the methods or algorithms described in conjunction with the embodiments herein can be directly embodied in hardware, software modules executed by a processor, or a combination thereof. The software modules can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disks, removable disks, CD-ROMs, or any other form of storage medium well known in the art. An exemplary storage medium is connected to the processor, enabling the processor to read information from and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and storage medium can reside in an ASIC. The ASIC can reside in a user terminal. Alternatively, the processor and storage medium can exist as discrete components in the user terminal.

[0078] For software implementation, the techniques described in this application can be implemented using modules (e.g., procedures, functions, etc.) that perform the functions described in this application. This software code can be stored in memory units and executed by a processor. The memory units can be implemented within the processor or outside the processor; in the latter case, they are communicatively coupled to the processor via various means, as is well known in the art.

[0079] The foregoing description includes examples of one or more embodiments. It is certainly impossible to describe all possible combinations of components or methods in order to describe the above embodiments, but those skilled in the art will recognize that further combinations and arrangements of the various embodiments are possible. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations that fall within the scope of the appended claims. Furthermore, the term "comprising" as used in the specification or claims is interpreted in a manner similar to the term "including," as interpreted when used as a conjunction in the claims. Additionally, the use of any term "or" in the specification of the claims is intended to mean "non-exclusive or."

Claims

1. A pre-conduit construction process for circulating grouting, characterized in that, Includes the following steps: S1, double-ring holes are drilled in the tunnel wall using down-the-hole drilling; S2, insert the grouting pipe (16) into the small guide pipe (15), with the tail end exposed and connected to the grout inlet pipe (6), the grouting port of the small guide pipe (15) is connected to the steel gate valve (17) for sealing, and the tail end is connected to the return grout pipe (9) through a three-way valve; S3. The prepared grout is introduced into the grout storage tank (3) through the grout inlet pipe (6), grout injection pipe (16), small guide pipe (15), surrounding rock fissure, and grout return pipe (9). Grout is injected from both sides to the tunnel arch in two sequences. The cement grout is injected at an initial pressure of 0.5MPa and the pressure is increased in a stepwise manner until the final pressure is 3-5MPa, at which point the pressure increase is stopped. S4, during the grouting process, collects grouting data in real time and adjusts grouting parameters; S5, after grouting is completed and the hole is mechanically sealed, the hole is manually filled and sealed.

2. The advanced small-diameter pipe construction technology for circulating grouting according to claim 1, characterized in that, In step S1, the double-ring hole includes a first annular hole (13) and a second annular guide hole (14). The opening position of the first annular hole (13) is outside the designed tunnel outline, with an external insertion angle of 15°. The opening position of the second annular guide hole (14) is inside the steel arch frame, with an external insertion angle of 10° to 15°. The first annular hole (13) and the second annular guide hole (14) are staggered.

3. The advanced small-diameter pipe construction technology for circulating grouting according to claim 2, characterized in that, The process of drilling the double-ring hole in step S1 is as follows: According to the skip drilling construction method, the first ring hole (13) is constructed first, and the next arch frame is excavated and the support is erected. The second ring guide hole (14) is constructed and the hole is cleaned.

4. The advanced small-diameter pipe construction technology for circulating grouting according to claim 3, characterized in that, In step S2, the small guide tube (15) is made of seamless steel pipe. The grouting port end of the small guide tube (15) is connected to a steel gate valve (17) to seal the gap between the surrounding rock borehole and the small guide tube (15). The grouting pipe (16) is a galvanized steel pipe and is set inside the small guide tube (15). The grout return pipe (9) is a four-layer high-pressure steel wire pipe. The grout return pipe (9) is connected to the small guide tube (15) through a three-way valve.

5. The advanced small-diameter pipe construction technology for circulating grouting according to claim 4, characterized in that, The small guide tube (15) has no holes within 1m from the grouting port end, which is a hole-free section. At the rear end, plum blossom-shaped overflow holes are opened at intervals of 25cm. The overflow holes are based on the axis of the small guide tube (15) and are evenly arranged in 6 rows around the circumference. The axial spacing of each row of holes is 25cm, and adjacent rows of holes are arranged in a staggered manner.

6. The advanced small-diameter pipe construction technology for circulating grouting according to claim 5, characterized in that, In step S3, the step pressurization is increased by 0.5 MPa every 5 minutes. The grouting pump includes a main pump (5) and an auxiliary pump (10). When the pressure is ≤2 MPa, the main pump (5) performs grouting. When the pressure is >2 MPa, the auxiliary pump (10) is started to pressurize the reflux grout to the final pressure.

7. The advanced small-diameter pipe construction technology for circulating grouting according to claim 6, characterized in that, In step S4, the grouting data is monitored by a pressure sensor (7) installed at the three-way valve of the return grout pipe (9) to monitor the actual pressure at the orifice. A flow meter (4) and a density meter (11) are installed in the pipe section from the grouting pump outlet to the injection pipe (16). The flow meter (4) is used to measure the grout intake, and the density meter (11) detects the grout density in real time. The grout pressure is released by a high-pressure valve (8) installed on the return grout pipe (9).

8. The advanced small-diameter pipe construction technology for circulating grouting according to claim 7, characterized in that, The process of first mechanically sealing the hole and then manually sealing it in step S5 is as follows: After grouting, a hydraulic piston sealing pump is used for mechanical sealing, and a biodegradable mold bag is placed in the borehole. The pressure value is taken as the final pressure value reached in step S3 and grouting is continued for 10 minutes. When the flow meter (4) reading drops to the pre-designed flow rate, the sealing operation is ended after stabilizing the pressure for 2 minutes. Before the cement in the mechanically sealed borehole sets, manual sealing is carried out. The borehole is cleaned with high-pressure air and finally mortar is injected.

9. The advanced small-diameter pipe construction technology for circulating grouting according to claim 1, characterized in that, It also includes S6, where, 24 hours after the sealing of the hole in step S5, an elastic wave test is used to check the grouting quality.

10. The pre-conduit construction process for circulating grouting according to claim 9, characterized in that, The grouting quality inspection process in step S6 is as follows: After the first ring hole (13) is completed, the first wave velocity test is carried out and the first set of data is recorded. After the second ring guide hole (14) is completed and grouting is completed, the second wave velocity test is carried out to form the second set of data. The two sets of data are combined and a data table is formed. Finally, the data are compared and analyzed to calculate the lifting rate. If the lifting rate result is less than the lifting rate threshold K, then supplementary grouting is carried out until the final pressure and the lifting rate threshold K are met at the same time.

Images