Micro-settlement control method for large-span tunnel with pipe-roofing pre-built structure

Abstract

The invention discloses a pipe-roofing pre-built structure large-span tunnel micro-settlement control method, and relates to the technical field of tunnel engineering.The pipe-roofing pre-built structure large-span tunnel micro-settlement control method comprises the following steps that S1, geological exploration is conducted on a target construction area, and the elastic modulus E and the deformation coefficient K of a stratum of the target construction area are obtained; calculating to obtain the minimum pipe spacing Lmin which does not cause the stratum deformation superimposed effect; s2, interval synchronous pipe jacking construction is conducted, multiple times of synchronous jacking construction are conducted on the pipe sheds step by step along the contour line of the tunnel, at least two pipe sheds are jacked synchronously each time, and during single-time synchronous jacking construction, the distance between the adjacent pipe sheds is controlled to be larger than the minimum pipe distance Lmin; and S3, interval synchronous grouting construction is carried out, and multiple times of synchronous grouting construction are carried out according to the sequence of multiple times of synchronous jacking construction. According to the technical scheme, the project progress and the construction reliability are both considered.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel engineering, and in particular to a micro-settlement control method for a large-span tunnel with a pipe-roof prefabricated structure. Background Art

[0002] During the construction process, the sensitivity of the crossing environment has become a major problem. Especially when crossing under sensitive urban environmental areas, the control of deformation and settlement becomes extremely difficult. For crossings under special conditions, such as high-speed rail lines and historical and cultural relics protection areas, the difficulty and risk of construction are multiplied. Against the backdrop of these complex challenges, millimeter-level settlement control has become the core goal of engineering design and construction.

[0003] However, the related technology is difficult to balance the project progress and construction reliability when carrying out the pipe curtain method construction. Summary of the invention

[0004] The main purpose of the present invention is to propose a construction method for a pipe-roof prefabricated mechanism based on large-span tunnel construction, aiming to balance engineering progress and construction reliability.

[0005] To achieve the above object, the present invention proposes a micro-settlement control method for a large-span tunnel with a pipe-roof prefabricated structure, and the micro-settlement control method for a large-span tunnel with a pipe-roof prefabricated structure comprises the following steps: Step S1: Conduct geological exploration of the target construction area, obtain the elastic modulus E and deformation coefficient K of the strata in the target construction area, and calculate the minimum pipe spacing L that will not cause the superposition effect of stratum deformation. min ; Step S2: Perform synchronous pipe jacking at intervals, and gradually perform multiple synchronous jacking operations on the pipe sheds along the contour line of the tunnel. Each time, at least two pipe sheds are synchronously jacked. During a single synchronous jacking operation, the spacing between adjacent pipe sheds is controlled to be greater than the minimum pipe spacing L. min ; Step S3, performing interval synchronous grouting, and performing multiple synchronous grouting operations in the order of multiple synchronous jacking operations.

[0006] In some embodiments, the minimum tube spacing L min The calculation formula is as follows: ; Where D is the diameter of a single pipe rack.

[0007] In some embodiments, the formation deformation coefficient K is determined according to the bottom layer type and soil properties, where: For sandy soil layers, the K value ranges from 1.2 to 1.5; For clay layers, K ranges from 1.0 to 1.2; For gravel layers, the K value ranges from 1.5 to 1.8.

[0008] In some embodiments, each time the pipe jacking is synchronously performed, the ground deformation is monitored in real time and the total ground deformation is calculated. When the total ground deformation is higher than the allowable surface settlement value, the parameters of the pipe jacking are adjusted.

[0009] In some embodiments, the total deformation of the formation is calculated as follows: ; Among them, S total is the total ground deformation, S1 is the ground deformation caused by the construction of a single jacking pipe, S2 is the ground deformation caused by the construction of adjacent jacking pipes, and L is the actual spacing between jacking pipes.

[0010] In some embodiments, adjusting the parameters of the pipe jacking operation includes at least one of the following steps: Increase the distance between adjacent ceilings during single synchronous pipe jacking; Reduce the speed of pipe jacking during single synchronous pipe jacking; Adjust the order of multiple pipe jacking operations.

[0011] In some embodiments, the sequence of multiple interval synchronous pipe jacking operations is: Conduct synchronous pipe jacking at intervals in the stratum at the bottom of the tunnel contour; Perform synchronous pipe jacking at intervals on both sides of the tunnel contour line, and synchronously jack at least two pipe sheds on both sides opposite to each other in the order of first down and then up; The synchronous pipe jacking is carried out at intervals in the stratum where the top of the tunnel contour is located.

[0012] In some embodiments, the following steps are also included: Use a level to measure the ground settlement in real time and stop construction when the ground settlement exceeds the allowable amount; and / or During each synchronous pipe jacking operation, strain gauges and displacement sensors are used to monitor at least one pipe shed in real time. Construction is stopped when the real-time displacement of the pipe shed exceeds the allowable displacement or the real-time stress value exceeds the allowable stress value.

[0013] In some embodiments, when the interval synchronous grouting is performed, the segmented grouting technology is implemented for each pipe jack, and the length of each grouting section is 1 / 3 to 1 / 2 of the total length of the jacking pipe.

[0014] In some embodiments, before grouting each pipe rack, the grouting pressure P is calculated by the following formula: inj : ; Among them, P0 is the foundation grouting pressure, γ is the unit weight of the formation, H is the construction burial depth, n is the grouting depth correction coefficient, S is the construction load, L is the jacking pipe length, and K is the grouting pressure distribution coefficient.

[0015] The technical solution of the present invention obtains the elastic module E and deformation coefficient K of the stratum in the target construction area through geological exploration of the target construction area, and calculates and obtains the minimum pipe spacing L that will not cause the superposition effect of stratum deformation. min The method of intermittent synchronous pipe jacking is adopted during the construction of the pipe jacking, which can reduce the superposition and cumulative effect of the surface settlement troughs between two adjacent ceilings during the synchronous pipe jacking, thereby reducing the surface settlement during the construction of the pipe curtain prefabricated structure and improving the stability of the structure and environment during the construction process. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0017] Figure 1 A flowchart of a method for controlling micro-settlement of a large-span tunnel with a prefabricated pipe-roof structure provided in one embodiment of the present invention; Figure 2 A partial flow chart of a method for controlling micro-settlement of a large-span tunnel with a prefabricated pipe-roof structure provided in one embodiment of the present invention; Figure 3 A partial schematic diagram of a pipe-roof structure obtained after synchronous interval jacking operation is performed in a method for controlling micro-settlement of a large-span tunnel with a pipe-roof prefabricated structure provided in an embodiment of the present invention.

[0018] The reference numerals in the figures are as follows: 100, ordinary pipe-roof structure; 110, pipe body; 120, male connector; 130, female connector; 200, special pipe-roof structure; 210, pipe body; 220, male connector.

[0019] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0022] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0023] In modern urban construction and infrastructure development, large-span tunnel construction faces severe challenges. Especially when tunnel construction is carried out in environmentally sensitive areas, controlling surface settlement becomes a key issue. This situation is particularly prominent when crossing special areas such as high-speed railway lines and historical and cultural relics protection areas, and the construction difficulty and risk are significantly increased.

[0024] In these complex construction environments, achieving millimeter-level settlement control has become the core goal of engineering design and construction. However, traditional construction methods often seem powerless in the face of these challenges. In the process of tunnel pipe curtain construction, single-tube sequential construction can significantly reduce the superposition effect of stratum deformation when adjacent pipe curtains are jacked in, but it undoubtedly requires a longer construction period; while the use of group pipes for simultaneous construction can shorten the construction period, it will cause a large deformation superposition effect, resulting in a significant increase in surface settlement. This makes it difficult to strike a balance between project progress and construction reliability.

[0025] Based on the above questions, please refer to Figure 1 The present invention proposes a micro-settlement control method for a large-span tunnel with a pipe-roof prefabricated structure, and the micro-settlement control method for a large-span tunnel with a pipe-roof prefabricated structure comprises the following steps: Step S1: Conduct geological exploration of the target construction area, obtain the elastic modulus E and deformation coefficient K of the strata in the target construction area, and calculate the minimum pipe spacing L that will not cause the superposition effect of stratum deformation. min .

[0026] This step is a preparatory step before construction. By fully understanding the characteristics of the stratum before construction, it provides a theoretical basis for subsequent construction. First, geological exploration is carried out in the target construction area to obtain the elastic modulus E and deformation coefficient K of the stratum. The elastic modulus E refers to the ability of the stratum material to deform during the stress process, and the deformation coefficient K refers to the degree of deformation of the stratum material during the stress process.

[0027] Among them, the determination of the elastic modulus E of the stratum can be carried out by taking samples on site and then measuring the elastic modulus E of the stratum by static load test or dynamic test; the determination of the deformation coefficient K of the stratum can be carried out by measuring the deformation coefficient K of the soil body through laboratory test according to the physical and mechanical properties of the soil body. For example, for a sandy soil layer, the K value can be determined by measuring its density, water content, particle grading and other indicators; for a clay layer, the K value can be determined by measuring its plasticity index, liquid limit, compression coefficient and other indicators.

[0028] Based on these data, the minimum pipe spacing L that will not cause the superposition effect of formation deformation can be calculated. min The distance is calculated to ensure that during the construction process, adjacent jacking pipes will not affect each other and produce excessive stratum deformation superposition effect.

[0029] That is to say, during the pipe jacking operation, as long as the distance between adjacent pipe sheds is controlled to be greater than the minimum pipe spacing L min , which can reduce the superposition effect of stratum deformation between adjacent pipe shelves when the pipe shelves are pushed forward synchronously.

[0030] Step S2, perform synchronous pipe jacking at intervals, and perform multiple synchronous jacking operations on the pipe sheds step by step along the contour line of the tunnel, with at least two pipe sheds being synchronously jacked each time, and during a single synchronous jacking operation, the spacing between adjacent pipe sheds is controlled to be greater than the minimum pipe spacing Lmin.

[0031] In this step, at least two pipe racks are pushed forward simultaneously each time, which means that the number of pipe racks pushed forward simultaneously each time can be selected according to the size of the tunnel entrance, and at least two pipe racks are pushed forward simultaneously. In this way, the construction period can be greatly shortened under the premise of controlling the surface settlement.

[0032] Step S3, performing interval synchronous grouting, and performing multiple synchronous grouting operations in the order of multiple synchronous jacking operations.

[0033] Accordingly, after all pipe sheds have completed the pipe jacking process, the consistency between the pipe shed and the stratum can be improved by grouting into the pipe shed, further improving the reliability of the micro-settlement control method for large-span tunnels with prefabricated pipe-curtain structures.

[0034] At the same time, in these embodiments of the present application, by performing synchronous grouting at intervals, the next grouting is performed after the slurry injected in the previous step solidifies. At the same time, grouting is performed synchronously on pipe racks at a certain distance during grouting, which can reduce the risk of weakening the strength of the formation due to a large amount of grouting in a certain area at the same time.

[0035] After all the pipe-roof grouting is completed and the slurry is solidified, a pipe-roof prefabricated structure with a certain strength can be formed. At this time, by excavating and reinforcing the soil layer covered in the pipe-roof prefabricated structure, the tunnel can be built while reducing surface settlement.

[0036] In these embodiments of the present application, by adopting a method of multiple synchronous jacking during the jacking operation, the surface settlement caused by the construction of the pipe curtain prefabricated structure can be reduced while shortening the construction period. Furthermore, in other jacking operations except the first time, it is necessary to connect the pipe shed of this jacking with the pipe shed that has completed the jacking through the interface structure (mortise and tenon) set on the surface of the pipe shed before jacking, so that adjacent pipe sheds can be connected through the interface structure, thereby improving the structural stability and waterproof performance after grouting. However, in these embodiments of the present application, the jacking is carried out by adopting a method of multiple synchronous interval jacking. Under the premise that the structures of each pipe shed are the same, it is easy to have a size mismatch during the last jacking, which makes it impossible for the pipe shed to be connected with other pipe sheds through the interface structure.

[0037] Based on this, in the last jacking of the interval synchronous jacking, a pipe shed structure with adjustable interface structure can be selected. Figure 3 The common pipe-roof structure 100 includes a pipe body 110 and a male connector 120 and a female connector 130 which are arranged on opposite sides of the pipe body 110 and extend along the length direction. The male connector 120 and the female connector 130 are fixedly connected to the pipe body 110 to improve the structural consistency of the common pipe-roof structure 100, thereby obtaining a higher structural strength.

[0038] During the last jacking of the interval synchronous pipe jacking, a special pipe roof structure 200 can be selected. In the special pipe roof structure 200, a detachable connection can be set between the male connector 220 and the pipe body 210. In this way, during the last jacking of the interval synchronous pipe jacking, the male connector 220 of a suitable size can be selected first, and after connecting the male connector 220 to the pipe body 210, the special pipe roof structure 200 can be connected to the interface structure of two ordinary pipe roof structures 100 on both sides for jacking. This solves the problem that the pipe roof size cannot correspond to the construction error in the last step of jacking during the interval synchronous pipe jacking, thereby improving the fluency of the micro-settlement control method of large-span tunnels with pipe-curtain prefabricated structure.

[0039] According to the micro-settlement control method for a large-span tunnel with a pipe-roof prefabricated structure provided in the embodiment of the present application, the elastic module E and deformation coefficient K of the stratum in the target construction area are obtained by geological exploration of the target construction area, and the minimum pipe spacing L that will not cause the superposition effect of stratum deformation is calculated. min The method of intermittent synchronous pipe jacking is adopted during the construction of the pipe jacking, which can reduce the superposition and cumulative effect of the surface settlement troughs between two adjacent ceilings during the synchronous pipe jacking, thereby reducing the surface settlement during the construction of the pipe curtain prefabricated structure and improving the stability of the structure and environment during the construction process.

[0040] In some embodiments, the minimum tube spacing Lmin is calculated as follows: ; Where D is the diameter of a single pipe rack.

[0041] In these embodiments of the present application, the larger the diameter D of the pipe rack is, the larger the disturbance range of the pipe rack to the formation is, and therefore a larger spacing distance is required to avoid mutual influence.

[0042] The elastic modulus E of the formation reflects the rigidity of the formation material. The larger the elastic modulus, the harder the formation and the smaller the deformation; conversely, the softer the formation, the greater the deformation.

[0043] The formation deformation coefficient K is an empirical coefficient related to the formation type and soil properties, and is used to adjust the impact of formation deformation on the jacking pipe interval.

[0044] Half of the jacking pipe diameter D, "D / 2", is based on the physical size of the jacking pipe itself, ensuring that there is enough space between adjacent jacking pipes to avoid direct contact. The "E / K" portion is a correction term based on the properties of the formation. Formation elastic modulus E The larger the value, the harder the stratum, and the smaller the disturbance range of the stratum caused by the jacking construction, so the jacking interval can be appropriately reduced; and the stratum deformation coefficient K Adjustments are made according to the stratum type (such as sand, clay, and gravel layers) to reflect the deformation characteristics of different strata.

[0045] In some embodiments, the formation deformation coefficient K is determined according to the bottom layer type and soil properties, where: For sandy soil layers, the K value ranges from 1.2 to 1.5; for clay layers, the K value ranges from 1.0 to 1.2; and for gravel layers, the K value ranges from 1.5 to 1.8.

[0046] These ranges are derived from a large number of experiments and engineering practices, and can more accurately reflect the deformation characteristics of different soil layers. Specifically, the physical and mechanical properties of the soil can be measured through field sampling and laboratory testing to determine the appropriate K value. For example, for sandy soil layers, the K value can be determined by measuring its density, water content, particle grading and other indicators; for clay layers, the K value can be determined by measuring its plasticity index, liquid limit, compression coefficient and other indicators; for gravel layers, the K value can be determined by measuring its particle composition, porosity, compression modulus and other indicators.

[0047] This application provides a range of K values ​​for different types of soil layers, making the calculated minimum pipe spacing Lmin more accurate, thereby better controlling stratum deformation during construction and ensuring the safety and reliability of construction. Compared with the prior art, this application can better adapt to complex geological conditions by clarifying the range of K values ​​for different soil layers, improving the accuracy of calculation and the reliability of construction. As a result, this application not only improves the safety of construction, but also effectively controls stratum deformation and settlement problems, and has high practical value.

[0048] In some embodiments, each time the pipe jacking is synchronously performed, the ground deformation is monitored in real time and the total ground deformation is calculated. When the total ground deformation is higher than the allowable surface settlement value, the parameters of the pipe jacking are adjusted.

[0049] In some embodiments, the total deformation of the formation is calculated as follows: ; Among them, S total is the total ground deformation, S1 is the ground deformation caused by the construction of a single jacking pipe, S2 is the ground deformation caused by the construction of adjacent jacking pipes, and L is the actual spacing between jacking pipes.

[0050] When the actual spacing L of the top pipe is equal to the minimum clearance L min When the deformation of adjacent jacking pipes is the smallest, the total deformation S total The deformation S1 is close to that of a single jacking pipe.

[0051] When the actual spacing L of the top pipe is less than the minimum spacing L min When the deformation of adjacent jacking pipes increases significantly, the total deformation S total Will increase.

[0052] In the formula, "1-L / L min The " part is a correction factor used to quantify the effect of the jacking interval on the deformation superposition effect. When L is close to L min When L is much smaller than L min When , the correction coefficient is close to 1, and the deformation superposition effect is significant.

[0053] In the actual construction process, the ground deformation can be monitored in real time, and the total deformation S can be calculated by combining the above formula. total , to assess whether the impact of the construction team's strata is within the controllable range. In other words, if the calculated S total If the ground settlement approaches or exceeds the allowable value (such as 10 mm), the pipe jacking construction parameters need to be adjusted to ensure construction safety and control of ground settlement.

[0054] It should be noted that in these embodiments of the present application, the stratum deformation amount S1 caused by the construction of a single jacking pipe can be obtained by on-site detection, using strain gauges and displacement sensors to monitor the bottom deformation amount caused by the construction of a single jacking pipe in real time. The stratum deformation amount S2 caused by the construction of adjacent jacking pipes can be obtained by numerical simulation, using finite element analysis software to simulate the bottom deformation amount caused by the construction of adjacent jacking pipes.

[0055] In some embodiments, adjusting the parameters of the pipe jacking operation includes at least one of the following steps: Increase the spacing between adjacent ceilings during a single synchronous pipe jacking operation. For example, when the total deformation of the stratum monitored in real time is close to the allowable surface settlement value, the spacing between adjacent ceilings can be increased by 10% to 20%.

[0056] Reduce the speed of pipe jacking during a single synchronous pipe jacking operation. For example, when the total deformation of the stratum monitored in real time is close to the allowable surface settlement value, the speed of pipe jacking can be reduced by 20% to 30%.

[0057] Adjust the order of multiple pipe jacking operations.

[0058] In some embodiments, the sequence of multiple interval synchronous pipe jacking operations is: Conduct synchronous pipe jacking at intervals in the stratum at the bottom of the tunnel contour; Perform synchronous pipe jacking at intervals on both sides of the tunnel contour line, and synchronously jack at least two pipe sheds on both sides opposite to each other in the order of first down and then up; The jacking is carried out synchronously at intervals in the stratum at the top of the tunnel contour line. That is, the refined construction process of "circumferential stratification (upper, middle and lower layers), longitudinal segmentation, first lower and then upper, and symmetrical jump-hitting" is adopted to control the peak value of surface settlement within the allowable range.

[0059] In some embodiments, the following steps are also included: Use a level to measure the ground settlement in real time and stop construction when the ground settlement exceeds the allowable amount; and / or During each synchronous pipe jacking operation, strain gauges and displacement sensors are used to monitor at least one pipe shed in real time. Construction is stopped when the real-time displacement of the pipe shed exceeds the allowable displacement or the real-time stress value exceeds the allowable stress value.

[0060] The technical solution of this application is mainly to ensure that the settlement and displacement during the construction process are within a safe range by real-time monitoring and control of the surface settlement and the displacement of the pipe shed, thereby effectively solving the technical problem of micro-settlement control. Specifically, the use of a level for real-time measurement can accurately monitor the surface settlement and stop construction in time when it exceeds the allowable value to avoid further settlement from affecting the surrounding environment. At the same time, by real-time monitoring of the pipe shed through strain gauges and displacement sensors, the displacement and stress values ​​of the pipe shed can be accurately grasped. When these parameters exceed the allowable range, construction is stopped in time to ensure construction safety.

[0061] Furthermore, the level can adopt a high-precision electronic level to improve the measurement accuracy and response speed. The strain gauge can be arranged at the key position of the pipe shed to more accurately reflect the stress condition of the pipe shed. The displacement sensor can adopt a laser displacement sensor or an inductive displacement sensor to improve the accuracy and stability of the measurement. In addition, the data of these monitoring devices can be transmitted to the central control system in real time to realize real-time monitoring and adjustment of the construction process.

[0062] Through the above technical means, this application can not only detect and respond to abnormal situations in a timely manner during the construction process, avoid construction risks and safety hazards caused by excessive settlement or displacement, but also improve the reliability of construction and ensure the safety and stability of the project. Compared with the existing technology, the method of this application has significant advantages in improving monitoring accuracy and response speed, and can better meet the requirements of micro-settlement control in large-span tunnels.

[0063] In some embodiments, when the interval synchronous grouting is performed, the segmented grouting technology is implemented for each pipe jack, and the length of each grouting section is 1 / 3 to 1 / 2 of the total length of the jacking pipe.

[0064] In these embodiments of the present application, the length of the grouting section can be determined first, and the top pipe can be divided into several sections according to the length of the top pipe and the construction requirements, and the length of each section is usually 1 / 3 to 1 / 2 of the top pipe length. This segmentation method can effectively control the grouting range and avoid excessive soil disturbance.

[0065] Since each section of the pipe shed is provided with grouting holes on the side wall or top, the slurry injected into the pipe shed can flow out through the grouting holes and mix with the stratum to reinforce the structure of the stratum. The spacing of the grouting holes should be determined according to the diffusion radius of the slurry, which is generally twice the diffusion radius of the slurry. Among them, the location of the grouting holes should avoid the key stress-bearing parts of the jacking pipe to prevent the grouting pressure from damaging the jacking pipe structure.

[0066] Finally, grouting is carried out in sequence according to the segmented order. After each segment is grouting, wait for the slurry to solidify before grouting the next segment. During the grouting process, the grouting pressure and grouting volume should be strictly controlled to avoid excessive pressure causing soil uplift or slurry loss.

[0067] In these embodiments of the present application, during the grouting process, the ground deformation is monitored in real time, including ground settlement, soil displacement, etc. If the deformation is too large, the grouting parameters (such as grouting pressure, grouting volume) should be adjusted in time or the grouting should be suspended, and corresponding remedial measures should be taken.

[0068] In these embodiments of the present application, local reinforcement and stress dispersion can be achieved by adopting the method of segmented grouting. Segmented grouting forms a reinforcement body by injecting slurry in a local area, thereby improving the bearing capacity and stability of the stratum. This local reinforcement can effectively disperse the stress generated during the pipe jacking construction process and avoid soil deformation caused by stress concentration. At the same time, the disturbance range of the soil can be reduced. Compared with continuous grouting, segmented grouting can limit the grouting range to a smaller area to avoid large-area soil disturbance. This helps to reduce the plastic deformation of the soil and the generation of additional stress, thereby reducing the risk of deformation of the bottom layer. The gaps can also be filled in time. During the pipe jacking construction process, the soil between the pipes may have gaps due to excavation. Segmented grouting can fill these gaps in time to prevent further collapse or deformation of the soil. Filling grouting can also increase the friction between the pipe curtain and the surrounding rock and reduce the jacking resistance. Controlling the grouting parameters, segmented grouting allows construction personnel to adjust the grouting pressure and grouting amount according to the specific conditions of each section to avoid soil uplift or slurry loss caused by excessive grouting or excessive pressure. This refined grouting control can effectively reduce the deformation of the underlying layer.

[0069] In some embodiments, before grouting each pipe rack, the grouting pressure P is calculated by the following formula: inj : ; Among them, P0 is the foundation grouting pressure, γ is the unit weight of the formation, H is the construction burial depth, n is the grouting depth correction coefficient, S is the construction load, L is the jacking pipe length, and K is the grouting pressure distribution coefficient.

[0070] For each parameter in the formula, P inj It is the actual grouting pressure that needs to be applied during construction.

[0071] P0 is the initial pressure determined according to the grouting material and formation type, and is usually in the range of 0.1 to 0.3 MPa, which is used to ensure that the slurry can be smoothly injected into the formation.

[0072] The value of γ reflects the density and gravity of the bottom layer. For different stratum types, the value range of γ is generally 15 to 20 KN / m 3 .

[0073] H is the depth of the pipe jacking construction area. A shallow burial depth means that the formation pressure is relatively small, but the construction load is high, so the grouting pressure needs to be adjusted.

[0074] The value of n is used to adjust the effect of the burial depth on the grouting pressure. Under shallow burial conditions, the value of n can be set in the range of 1.2 to 1.5; while under deeper burial conditions, the value of n can be set in the range of 1.0 to 1.2.

[0075] S reflects the additional load imposed on the stratum during the construction process. In areas with high loads, higher grouting pressure is required to balance the construction load.

[0076] L represents the length of the jacking pipe, so that the grouting pressure can be adjusted according to the length of the jacking pipe to improve the uniformity of the distribution of the slurry in the pipe shed.

[0077] The value of K is used to adjust the distribution of grouting pressure along the length of the jacking pipe. Generally speaking, the value of K can be controlled in the range of 2.0 to 3.0.

[0078] In these embodiments of the present application, the unit weight γ of the formation and the construction burial depth H can be first determined based on the results of the address exploration, the construction load S and the jacking pipe length L can be determined based on the construction design, and the appropriate grouting depth correction coefficient n and grouting pressure distribution coefficient K can be selected based on the bottom layer type and construction conditions. In this way, before the grouting stage begins, the grouting pressure can be calculated based on the aforementioned parameters obtained to obtain a better grouting pressure value.

[0079] In these embodiments of the present application, the formation deformation and grouting pressure can also be monitored in real time during the grouting process. If it is found that the formation deformation is too large or the slurry is lost, the grouting pressure can be appropriately reduced; if the grouting effect is not good (such as the slurry cannot fully fill the voids), the grouting pressure can be appropriately increased.

[0080] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention's specification and drawings, or directly / indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for controlling micro-settlement of a large-span tunnel with a prefabricated pipe-roof structure, characterized in that: The steps include: Conduct geological exploration of the target construction area, obtain the elastic modulus E and deformation coefficient K of the strata in the target construction area, and calculate the minimum pipe spacing L that will not cause the superposition effect of strata deformation. min ; The synchronous pipe jacking is carried out at intervals, and the pipe sheds are gradually pushed forward multiple times along the contour line of the tunnel. At least two pipe sheds are pushed forward synchronously each time, and during a single synchronous jacking operation, the spacing between adjacent pipe sheds is controlled to be greater than the minimum pipe spacing L. min ; The synchronous grouting is carried out at intervals, and multiple synchronous grouting operations are carried out in the order of multiple synchronous jacking operations.

2. The micro-settlement control method for a large-span tunnel with a pipe-roof prefabricated structure according to claim 1 is characterized in that: Minimum tube spacing L min The calculation formula is as follows: ； Where D is the diameter of a single pipe rack.

3. The micro-settlement control method for a large-span tunnel with a pipe-roof prefabricated structure according to claim 2 is characterized in that: The stratum deformation coefficient K is determined according to the bottom layer type and soil properties, where: For sandy soil layers, the K value ranges from 1.2 to 1.5; For clay layers, K ranges from 1.0 to 1.2; For gravel layers, the K value ranges from 1.5 to 1.

8.

4. The micro-settlement control method for a large-span tunnel with a pipe-roof prefabricated structure according to claim 1 is characterized in that: Each time the pipe jacking is synchronously pushed in, the ground deformation is monitored in real time and the total ground deformation is calculated. When the total ground deformation is higher than the allowable surface settlement value, the parameters of the pipe jacking are adjusted.

5. The micro-settlement control method for a large-span tunnel with a pipe-roof prefabricated structure according to claim 4 is characterized in that: The calculation formula of the total deformation of the stratum is as follows: ； Among them, S total is the total ground deformation, S1 is the ground deformation caused by the construction of a single jacking pipe, S2 is the ground deformation caused by the construction of adjacent jacking pipes, and L is the actual spacing between jacking pipes.

6. The micro-settlement control method for a large-span tunnel with a pipe-roof prefabricated structure according to claim 4 is characterized in that: The step of adjusting the parameters of the pipe jacking operation comprises at least one of the following steps: Increase the distance between adjacent ceilings during single synchronous pipe jacking; Reduce the speed of pipe jacking during single synchronous pipe jacking; Adjust the order of multiple pipe jacking operations.

7. The micro-settlement control method for a large-span tunnel with a pipe-roof prefabricated structure according to claim 6 is characterized in that: The order of multiple interval synchronous pipe jacking operations is: Carry out the interval synchronous pipe jacking in the stratum located at the bottom of the tunnel contour line; Perform synchronous pipe jacking at intervals on both sides of the tunnel contour line, and synchronously jack at least two pipe sheds on both sides opposite to each other in the order of first down and then up; The interval synchronous pipe jacking is carried out in the stratum where the top of the tunnel contour line is located.

8. The micro-settlement control method for a large-span tunnel with a pipe-roof prefabricated structure according to claim 1 is characterized in that: The following steps are also included: Use a level to measure the ground settlement in real time and stop construction when the ground settlement exceeds the allowable amount; and / or During each synchronous pipe jacking operation, strain gauges and displacement sensors are used to monitor at least one pipe shed in real time. Construction is stopped when the real-time displacement of the pipe shed exceeds the allowable displacement or the real-time stress value exceeds the allowable stress value.

9. The micro-settlement control method for a large-span tunnel with a pipe-roof prefabricated structure according to any one of claims 1 to 7, characterized in that: When the interval synchronous grouting is carried out, the segmented grouting technology is implemented for each of the pipe racks, and the length of each grouting section is 1 / 3 to 1 / 2 of the total length of the jacking pipe.

10. The micro-settlement control method for a large-span tunnel with a pipe-roof prefabricated structure according to claim 9 is characterized in that: Before grouting each pipe shed, the grouting pressure P is calculated by the following formula: inj : ； Among them, P0 is the foundation grouting pressure, γ is the unit weight of the formation, H is the construction burial depth, n is the grouting depth correction coefficient, S is the construction load, L is the jacking pipe length, and K is the grouting pressure distribution coefficient.

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