Method for Controlling Micro-Settlement of Large-Span Tunnel with Pipe Roof Prefabricated Structure

Abstract

The present invention discloses a method for controlling micro-settlement of a large-span tunnel with a pipe curtain prefabricated structure, which relates to the technical field of tunnel engineering. Among them, the method for controlling micro-settlement of a large-span tunnel with a pipe curtain prefabricated structure includes the following steps: Step S1, conduct geological exploration on the target construction area, obtain the elastic modulus E and deformation coefficient K of the strata in the target construction area, and calculate and obtain the minimum pipe spacing L that will not cause the superposition effect of stratum deformation min ; Step S2, perform jacking pipe construction at intervals synchronously, gradually perform synchronous jacking construction on the pipe shed multiple times along the contour line of the tunnel. Each time, at least two pipe sheds are jacked synchronously, and during a single synchronous jacking construction, control the spacing between adjacent pipe sheds to be greater than the minimum pipe spacing L min ; Step S3, perform grouting construction at intervals synchronously, and perform multiple synchronous grouting constructions in the order of multiple synchronous jacking constructions. The technical solution of the present invention aims to balance the project progress and construction reliability.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel engineering, and particularly to a method for controlling micro-settlement of 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 passing under in an urban environmental sensitive area, the control of deformation and settlement becomes extremely difficult. For crossings under special conditions, such as high-speed railway lines, historical and cultural relic protection areas, etc., the construction difficulty and risk increase exponentially. Against the backdrop of these complex challenges, millimeter-level settlement control has become the core goal of engineering design and construction.

[0003] However, related technologies are difficult to balance the project progress and construction reliability when conducting pipe roof method construction. Summary of the Invention

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

[0005] To achieve the above object, the present invention proposes a method for controlling micro-settlement of a large-span tunnel with a pipe roof prefabricated structure, and the method for controlling micro-settlement of the large-span tunnel with the pipe roof prefabricated structure includes the following steps:

[0006] Step S1: Conduct geological exploration on the target construction area, obtain the elastic modulus E and deformation coefficient K of the formation in the target construction area, and calculate and obtain the minimum pipe spacing L that will not cause the superposition effect of formation deformation min ;

[0007] Step S2: Carry out jacking pipe construction at intervals synchronously, gradually carry out multiple synchronous jacking operations on the pipe shed along the contour line of the tunnel, jack in at least two pipe sheds synchronously each time, and control the spacing between adjacent pipe sheds to be greater than the minimum pipe spacing L during a single synchronous jacking operation min ;

[0008] Step S3: Carry out grouting construction at intervals synchronously, and carry out multiple synchronous grouting operations in the order of multiple synchronous jacking operations.

[0009] In some embodiments, the calculation formula of the minimum pipe spacing L min is as follows:

[0010] ;

[0011] wherein, D is the diameter of a single pipe shed.

[0012] In some embodiments, the formation deformation coefficient K is determined according to the formation type and soil properties, wherein:

[0013] For sandy soil layers, the value range of K is from 1.2 to 1.5;

[0014] For clay soil layers, the value range of K is from 1.0 to 1.2;

[0015] For gravel layers, the value range of K is from 1.5 to 1.8.

[0016] In some embodiments, each time the pipe shed is jacked synchronously, the formation deformation amount is monitored in real time and the total formation deformation amount is calculated. When the total formation deformation amount is higher than the allowable ground settlement value, the parameters of the pipe jacking construction are adjusted.

[0017] In some embodiments, the calculation formula for the total formation deformation amount is as follows:

[0018] ;

[0019] Wherein, S total is the total formation deformation amount, S 1 is the formation deformation amount caused by the construction of a single pipe jacking, S 2 is the formation deformation amount caused by the construction of adjacent pipe jackings, and L is the actual interval distance between the pipe jackings.

[0020] In some embodiments, adjusting the parameters of the pipe jacking construction includes at least one of the following steps:

[0021] Increase the spacing between adjacent pipe sheds during a single synchronous pipe jacking construction;

[0022] Reduce the pipe shed jacking speed during a single synchronous pipe jacking construction;

[0023] Adjust the sequence of multiple pipe jacking constructions.

[0024] In some embodiments, the sequence of multiple interval synchronous pipe jacking constructions is as follows:

[0025] Carry out interval synchronous pipe jacking construction in the formation where the bottom of the tunnel contour line is located;

[0026] Carry out interval synchronous pipe jacking construction on both sides of the tunnel contour line, and synchronously jack at least two opposite pipe sheds on both sides in the order of from bottom to top;

[0027] Carry out interval synchronous pipe jacking construction in the formation where the top of the tunnel contour line is located.

[0028] In some embodiments, the following steps are further included:

[0029] Use a level to measure the ground settlement amount in real time, and stop the construction when the ground settlement amount exceeds the allowable settlement amount; and / or

[0030] During each synchronous pipe jacking operation, at least one pipe shed is monitored in real time using strain gauges and displacement sensors. 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.

[0031] In some embodiments, during the interval synchronous grouting operation, a segmented grouting technique is implemented for each pipe shed, and the grouting length of each segment is 1 / 3 to 1 / 2 of the total length of the pipe jacking operation.

[0032] In some embodiments, before grouting each pipe shed, the grouting pressure P is calculated using the following formula inj :

[0033] ;

[0034] where P 0 is the basic grouting pressure, γ is the unit weight of the formation, H is the construction depth, n is the grouting depth correction coefficient, S is the construction load, L is the length of the pipe jacking, and K is the grouting pressure distribution coefficient.

[0035] The technical solution of the present invention obtains the elastic modulus E and deformation coefficient K of the formation in the target construction area through geological exploration of the target construction area, calculates and obtains the minimum pipe spacing L that will not cause the superposition effect of formation deformation, and adopts the method of interval synchronous pipe jacking during pipe jacking construction, which can reduce the superposition cumulative effect of the surface settlement trough between adjacent two pipe roofs during synchronous pipe jacking construction, thereby reducing the surface settlement during the construction of the pipe curtain prefabricated structure and improving the stability of the structure and the environment during the construction process. min and can reduce the superposition cumulative effect of the surface settlement trough between adjacent two pipe roofs during synchronous pipe jacking construction, thereby reducing the surface settlement during the construction of the pipe curtain prefabricated structure and improving the stability of the structure and the environment during the construction process. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can be obtained based on the structures shown in these drawings without creative efforts.

[0037] Figure 1 is a flowchart of a method for controlling micro-settlement of a large-span tunnel with a pipe curtain prefabricated structure provided by an embodiment of the present invention;

[0038] Figure 2 is a partial flowchart of a method for controlling micro-settlement of a large-span tunnel with a pipe curtain prefabricated structure provided by an embodiment of the present invention;

[0039] Figure 3 is a partial schematic diagram of a pipe curtain structure obtained after synchronous interval jacking construction of a method for controlling micro-settlement of a large-span tunnel with a pipe curtain prefabricated structure provided by an embodiment of the present invention.

[0040] The reference numerals in the figures are as follows: 100, ordinary pipe roof structure; 110, pipe body part; 120, male joint; 130, female joint; 200, special pipe roof structure; 210, pipe body part; 220, male joint.

[0041] The realization, functional features and advantages of the present invention will be further described in conjunction with the embodiments with reference to the accompanying drawings. Detailed implementation manners

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0043] It should be noted that if there are directional indications (such as up, down, left, right, front, back...) involved in the embodiments of the present invention, the directional indications are only used to explain the relative positional relationship and movement conditions between components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0044] 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 for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, if "and / or" or "and / or" appears throughout the text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or a solution that satisfies both A and B at the same time. In addition, the technical solutions between the embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0045] In modern urban construction and infrastructure development, the construction of large-span tunnels faces severe challenges. Especially when constructing tunnels in environmentally sensitive areas, controlling ground settlement becomes a key issue. This situation is particularly prominent when crossing special areas such as high-speed railway lines and historical and cultural relic protection areas, and the construction difficulty and risk increase significantly.

[0046] 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 prove inadequate when faced with these challenges. During the construction of a tunnel pipe roof, constructing single pipes sequentially can significantly reduce the superposition effect of formation deformation during the jacking of adjacent pipe sheds. However, this undoubtedly requires a longer construction period. While constructing multiple pipes simultaneously can shorten the construction period, it will cause a larger superposition effect of deformation, resulting in a significant increase in the surface settlement. As a result, it is difficult to strike a balance between the project progress and construction reliability.

[0047] Based on the above problems, please refer to Figure 1 , the present invention proposes a method for micro-settlement control of a large-span tunnel with a pipe roof prefabricated structure. The method for micro-settlement control of a large-span tunnel with a pipe roof prefabricated structure includes the following steps:

[0048] Step S1: Conduct a geological exploration of the target construction area to obtain the elastic modulus E and deformation coefficient K of the formation in the target construction area, and calculate and obtain the minimum pipe spacing L that will not cause the superposition effect of formation deformation. min .

[0049] This step is a preparatory step before construction. By fully understanding the formation characteristics before construction, it provides a theoretical basis for subsequent construction. First, conduct a geological exploration of the target construction area to obtain the elastic modulus E and deformation coefficient K of the formation. The elastic modulus E refers to the ability of the formation material to deform during the stress process, and the deformation coefficient K refers to the degree of deformation of the formation material during the stress process.

[0050] Among them, to determine the formation elastic modulus E, after taking on-site samples, the elastic modulus E of the formation can be measured by using a static load test or a dynamic test; to determine the formation deformation coefficient K, according to the physical and mechanical properties of the soil, the deformation coefficient K of the soil can be measured through laboratory tests. For example, for sandy soil layers, the K value can be determined by measuring indicators such as its density, water content, and particle size distribution; for clay layers, the K value can be determined by measuring indicators such as its plasticity index, liquid limit, and compression coefficient.

[0051] Based on these data, the minimum pipe spacing L that will not cause the superposition effect of formation deformation can be calculated. min . The calculation of this distance is to ensure that during the construction process, excessive superposition effects of formation deformation will not occur between adjacent jacked pipes due to mutual influence.

[0052] That is to say, during the jacking of pipes, as long as the distance between adjacent pipe sheds during a single pipe jacking is controlled to be greater than the minimum pipe spacing L. min , the superposition effect of formation deformation between adjacent pipe sheds during the synchronous jacking of pipe sheds can be reduced.

[0053] 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.

[0054] 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.

[0055] Step S3, performing interval synchronous grouting, and performing multiple synchronous grouting operations in the order of multiple synchronous jacking operations.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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 ordinary pipe shed structure 100 includes a pipe body part 110, a male joint 120 and a female joint 130 which are arranged on opposite sides of the pipe body part 110 and extend along the length direction. Both the male joint 120 and the female joint 130 are fixedly connected to the pipe body part 110 to improve the structural integrity of the ordinary pipe shed structure 100, and thus higher structural strength can be obtained.

[0061] During the last jacking operation of the interval synchronous pipe jacking construction, the special pipe shed structure 200 can be selected. In this special pipe shed structure 200, a detachable connection method can be set between the male joint 220 and the pipe body part 210. In this way, during the last jacking operation of the interval synchronous pipe jacking construction, first, a male joint 220 with a suitable size can be selected, and after connecting the male joint 220 to the pipe body part 210, then connect the interface structures of the special pipe shed structure 200 and the two ordinary pipe shed structures 100 on both sides and then carry out pipe jacking, thus solving the problem that the pipe shed sizes cannot correspond under the influence of construction errors during the last step of pipe jacking in the interval synchronous pipe jacking construction, and then improving the smoothness of the micro-settlement control method for large-span tunnels with a pipe curtain prefabricated structure.

[0062] According to the micro-settlement control method for large-span tunnels with a pipe curtain prefabricated structure provided by the embodiments of the present application, by conducting geological exploration on the target construction area to obtain the elastic modulus E and deformation coefficient K of the formation of the target construction area, and calculating to obtain the minimum pipe spacing L that will not cause the superposition effect of formation deformation min , and by adopting the method of interval synchronous pipe jacking construction during pipe jacking operation, the superposition cumulative effect of the ground settlement troughs between adjacent two pipe sheds during synchronous pipe jacking construction can be reduced, thereby reducing the ground settlement during the construction of the pipe curtain prefabricated structure and improving the stability of the structure and the environment during the construction process.

[0063] In some embodiments, the calculation formula of the minimum pipe spacing Lmin is as follows:

[0064] ;

[0065] where D is the diameter of a single pipe shed.

[0066] In these embodiments of the present application, the larger the diameter D of the pipe shed, the greater the disturbance range of the formation to it. Therefore, a larger interval distance is required to avoid mutual influence.

[0067] The formation elastic modulus E reflects the rigidity of the formation material. The larger the elastic modulus, the harder the formation and the smaller the deformation; on the contrary, the softer the formation, the larger the deformation.

[0068] The formation deformation coefficient K is an empirical coefficient related to the formation type and soil properties, and is used to adjust the influence of formation deformation on the pipe jacking interval.

[0069] Half of the pipe jacking diameter D, "D / 2", is based on the physical dimensions of the pipe jacking itself to ensure sufficient space between adjacent pipe jackings to avoid direct contact. The "E / K" part is a correction term based on the formation properties. The formation elastic modulus E The larger it is, the harder the formation, and the smaller the disturbance range of the pipe jacking construction to the formation. Therefore, the pipe jacking interval can be appropriately reduced; while the formation deformation coefficient K is adjusted according to the formation type (such as sandy soil, clay, gravel layer) to reflect the deformation characteristics of different formations.

[0070] In some embodiments, the formation deformation coefficient K is determined according to the formation type and soil properties, where:

[0071] For sandy soil layers, the value range of K is 1.2 to 1.5; for clay layers, the value range of K is 1.0 to 1.2; for gravel layers, the value range of K is 1.5 to 1.8.

[0072] These value ranges are obtained through 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 by on-site sampling and laboratory testing methods, so as to determine the appropriate value of K. For example, for sandy soil layers, the value of K can be determined by measuring its density, water content, particle size distribution and other indicators; for clay layers, the value of K can be determined by measuring its plasticity index, liquid limit, compression coefficient and other indicators; for gravel layers, the value of K can be determined by measuring its particle composition, porosity ratio, compression modulus and other indicators.

[0073] This application provides the value range of K for different types of soil layers, making the calculated minimum pipe spacing Lmin more accurate, so as to better control the formation deformation during construction and ensure the safety and reliability of construction. Compared with the prior art, by clarifying the value range of K for different soil layers, this application can better adapt to complex geological conditions, improve the calculation accuracy and construction reliability. Thus, this application not only improves the construction safety, but also effectively controls the formation deformation and settlement problems, and has high practical value.

[0074] In some embodiments, each time the pipe shed is jacked synchronously, the formation deformation amount is monitored in real time and the total formation deformation amount is calculated. When the total formation deformation amount is higher than the allowable ground settlement value, the parameters of the pipe jacking construction are adjusted.

[0075] In some embodiments, the calculation formula of the total formation deformation amount is as follows:

[0076] ;

[0077] where S total is the total formation deformation amount, S 1 is the formation deformation amount caused by the construction of a single pipe jacking, S2 δ is the ground deformation caused by adjacent pipe jacking construction, and L is the actual distance between pipe jackings.

[0078] When the actual distance L between pipe jackings is equal to the minimum clearance L min , the deformation influence of adjacent pipe jackings is the smallest, and the total deformation δ total is close to the deformation δ of a single pipe jacking. 1 .

[0079] When the actual distance L between pipe jackings is less than the minimum clearance L min , the deformation influence of adjacent pipe jackings will increase significantly, and the total deformation δ total will increase.

[0080] The part "1 - L / L min " in the formula is a correction coefficient used to quantify the influence of the pipe jacking interval on the deformation superposition effect. When L is close to L min , the correction coefficient is close to 0, and the deformation superposition effect is small; when L is much smaller than L min , the correction coefficient is close to 1, and the deformation superposition effect is significant.

[0081] During the actual construction process, the ground deformation can be monitored in real time, and the total deformation δ can be calculated by combining the aforementioned formula total to evaluate whether the influence on the construction team's ground is within the controllable range. That is to say, if the calculated δ total is close to or exceeds the allowable ground settlement value (such as 10 mm), it is necessary to adjust the pipe jacking construction parameters to ensure construction safety and ground settlement control.

[0082] It should be noted that in these embodiments of the present application, the ground deformation δ1 caused by single pipe jacking construction can be obtained through on-site detection, and the ground deformation caused by single pipe jacking construction can be monitored in real time using strain gauges and displacement sensors. The ground deformation δ2 caused by adjacent pipe jacking construction can be obtained by numerical simulation, and the ground deformation caused by adjacent pipe jacking construction can be simulated using finite element analysis software.

[0083] In some embodiments, adjusting the parameters of pipe jacking construction includes at least one of the following steps:

[0084] Increase the distance between adjacent pipe roofs during a single synchronous pipe jacking operation. Exemplarily, when the total ground deformation monitored in real time is close to the allowable ground settlement value, the distance between adjacent pipe roofs can be increased by 10% to 20%.

[0085] Reduce the jacking speed of the pipe shed during a single synchronous pipe jacking operation. Exemplarily, when the total ground deformation monitored in real time is close to the allowable ground settlement value, the jacking speed of the pipe shed can be reduced by 20% to 30%.

[0086] Adjust the construction sequence of multiple pipe jackings.

[0087] In some embodiments, the construction sequence of multiple interval synchronous pipe jackings is as follows:

[0088] Perform interval synchronous pipe jacking in the formation at the bottom of the tunnel contour line;

[0089] Perform interval synchronous pipe jacking on both sides of the tunnel contour line, and synchronously jack at least two opposite pipe sheds on both sides in the order of from bottom to top;

[0090] Perform interval synchronous pipe jacking in the formation at the top of the tunnel contour line. That is, by adopting a refined construction process of "circumferential stratification (upper, middle, and lower three layers), longitudinal segmentation, from bottom to top, and symmetric skip drilling", the peak value of surface settlement can be controlled within the allowable range.

[0091] In some embodiments, the following steps are further included:

[0092] Use a level to measure the surface settlement in real time, and stop construction when the surface settlement exceeds the allowable settlement; and / or

[0093] During each synchronous pipe jacking, use strain gauges and displacement sensors to perform real-time monitoring on at least one pipe shed, and stop construction when the real-time displacement of the pipe shed exceeds the allowable displacement or the real-time stress value exceeds the allowable stress value.

[0094] The technical solution of the present application mainly ensures that the settlement and displacement during the construction process are within the safe range by real-time monitoring and controlling the surface settlement and the displacement of the pipe shed, thereby effectively solving the technical problem of micro-settlement control. Specifically, by using a level for real-time measurement, the surface settlement can be accurately monitored, and construction can be stopped in time when it exceeds the allowable value to avoid further settlement from affecting the surrounding environment. At the same time, by using strain gauges and displacement sensors to perform real-time monitoring on the pipe shed, the displacement and stress values of the pipe shed can be accurately grasped, and construction can be stopped in time when these parameters exceed the allowable range to ensure construction safety.

[0095] Furthermore, a high-precision electronic level can be used to improve the measurement accuracy and response speed. The strain gauges can be arranged at the key positions of the pipe shed to more accurately reflect the stress condition of the pipe shed. The displacement sensors can adopt laser displacement sensors or inductive displacement sensors to improve the measurement accuracy and stability. 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.

[0096] Through the above technical means, the present application can not only timely detect and respond to abnormal situations during the construction process, avoid construction risks and potential safety hazards caused by excessive settlement or displacement, but also improve the construction reliability and ensure the safety and stability of the project. Compared with the prior art, the method of the present application has significant advantages in improving the monitoring accuracy and response speed, and can better meet the requirements of micro-settlement control of large-span tunnels.

[0097] In some embodiments, during the interval synchronous grouting construction, the sectional grouting technology is implemented for each pipe shed, and the grouting length of each section is 1 / 3 to 1 / 2 of the total length of the pipe jacking construction.

[0098] In these embodiments of the present application, the length of the grouting section can be first determined. According to the length of the pipe jacking and the construction requirements, the pipe jacking is divided into several sections, and the length of each section is usually 1 / 3 to 1 / 2 of the pipe jacking length. This sectional method can effectively control the grouting range and avoid excessive soil disturbance.

[0099] Since grouting holes are provided on the side wall or top of each section of the pipe shed, the slurry injected into the pipe shed can flow out through the grouting holes and mix with the formation to reinforce the formation structure. The spacing of the grouting holes should be determined according to the diffusion radius of the slurry, generally twice the diffusion radius of the slurry. Among them, the position of the grouting holes should avoid the key stress parts of the pipe jacking to prevent the grouting pressure from damaging the pipe jacking structure.

[0100] Finally, the grouting is carried out in sequence according to the section. After the grouting of each section is completed, wait for the slurry to solidify before proceeding with the grouting of the next section. During the grouting process, the grouting pressure and grouting volume should be strictly controlled to avoid excessive pressure causing soil heave or slurry loss.

[0101] In these embodiments of the present application, during the grouting process, the deformation of the formation is monitored in real time, including ground settlement, soil displacement, etc. If excessive deformation is found, 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.

[0102] In these embodiments of the present application, by adopting the method of sectional grouting, local reinforcement and stress dispersion can be achieved. Sectional grouting injects slurry in a local area to form a reinforced body, thereby improving the bearing capacity and stability of the formation. This local reinforcement can effectively disperse the stress generated during the pipe jacking construction, avoiding soil deformation caused by stress concentration. At the same time, the range of soil disturbance can be reduced. Compared with continuous grouting, sectional grouting can limit the grouting range to a smaller area, avoiding 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 formation deformation. It can also fill the voids in time. During the pipe jacking construction, voids may be generated in the soil between the pipes due to excavation. Sectional grouting can fill these voids 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, reducing the jacking resistance. By controlling the grouting parameters, sectional grouting allows construction personnel to adjust the grouting pressure and grouting volume according to the specific conditions of each section, avoiding soil heave or slurry loss caused by excessive grouting or too high pressure. This refined grouting control can effectively reduce formation deformation.

[0103] In some embodiments, before grouting each pipe shed, the grouting pressure P is calculated by the following formula inj :

[0104] ;

[0105] where P 0 is the basic 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 pipe jacking length, and K is the grouting pressure distribution coefficient.

[0106] For each parameter in the formula, P inj is the actual grouting pressure that needs to be applied during construction.

[0107] P 0 is the initial pressure determined according to the grouting material and formation type, and its normal value range can be 0.1 to 0.3 MPa, which is used to ensure that the slurry can be smoothly injected into the formation.

[0108] The value of γ reflects the density and gravity influence of the formation. For different formation types, the value range of γ is generally 15 to 20 KN / m 3 .

[0109] H is the depth of the pipe jacking construction area. Shallow burial depth means relatively small formation pressure, but high construction load, so the grouting pressure needs to be adjusted.

[0110] The value of n is used to adjust the influence of the burial depth on the grouting pressure. Under shallow burial conditions, the value range of n can be set from 1.2 to 1.5; while under deeper burial depths, the value range of n can be set from 1.0 to 1.2.

[0111] S reflects the additional load applied to the formation during the construction process. In areas with high loads, a higher grouting pressure is required to balance the construction load.

[0112] L represents the length of the pipe jacking, so that the grouting pressure can be adjusted according to the pipe jacking length, improving the uniformity of the slurry distribution in the pipe shed.

[0113] The value of K is used to adjust the distribution of the grouting pressure in the direction of the pipe jacking length. Generally speaking, the value range of K can be controlled from 2.0 to 3.0.

[0114] In these embodiments of the present application, first, according to the results of the geological exploration, the unit weight γ of the formation and the construction burial depth H can be determined. According to the construction design, the construction load S and the pipe jacking length L can be determined, and according to the formation type and construction conditions, a suitable grouting depth correction coefficient n and a grouting pressure distribution coefficient K can be selected. Thus, before the start of the grouting stage, the grouting pressure can be calculated based on the foregoing parameters obtained to obtain a better grouting pressure value.

[0115] In these embodiments of the present application, the formation deformation and the 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; while if the grouting effect is not good (such as the slurry cannot fully fill the voids), the grouting pressure can be appropriately increased.

[0116] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. All equivalent structural transformations made under the inventive concept of the present invention by using the content of the specification and drawings of the present invention, 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 ; Minimum tube spacing L min The calculation formula is as follows: ； Where D is the diameter of a single pipe rack; Interval synchronous grouting, multiple synchronous grouting operations are carried out in the order of multiple synchronous jacking operations; 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 ground settlement value, the parameters of the pipe jacking are adjusted; 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.

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: The deformation coefficient K of the stratum is determined according to the stratum 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.

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3. 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 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.

4. The micro-settlement control method for a large-span tunnel with a pipe-roof prefabricated structure according to claim 3 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.

5. 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.

6. The micro-settlement control method for a large-span tunnel with a pipe-roof prefabricated structure according to any one of claims 1 to 5, 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.

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: 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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