Inverted arch creep heaving floor control method and system for high-ground-stress gently-inclined soft rock traffic tunnel

Abstract

The invention discloses an inverted arch creep floor heave control method and system for a high-ground-stress gently-inclined soft rock traffic tunnel. The floor heave control method comprises the steps that a section where floor heaves possibly occur in the tunnel is determined, and the optimal energy release hole arrangement mode in the section where the floor heaves possibly occur is determined; calculating the stress at different positions around the energy release hole by adopting an energy release hole peripheral stress calculation method, and selecting the minimum value of all the stress as the strength upper limit value of the creep energy release material for filling the energy release hole; selecting a creep energy release material, introducing a three-dimensional numerical model to verify whether the optimal energy release hole arrangement mode achieves a floor heave control effect, if not, adjusting the energy release hole arrangement mode until the floor heave control effect is achieved, and if yes, arranging energy release holes in a section where floor heaves may occur according to the optimal energy release hole arrangement mode, and the plastic pipe filled with the selected creep energy release material is placed in the energy release hole.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel engineering support, and in particular relates to a method and system for controlling creep floor drum of an invert arch of a high-ground stress slow-inclined soft rock traffic tunnel. Background Art

[0002] Driven by the continuous improvement of tunnel construction technology, my country's tunnel and underground engineering has developed rapidly and achieved remarkable results. my country is currently the world's largest tunnel country with the largest number of tunnels, the largest construction scale, and the fastest development speed. However, with the planning and construction of the Sichuan-Tibet Railway, a series of construction problems such as special geological and climatic environment, high altitude, high ground stress, frozen soil in cold areas, broken faults, and ecological protection need to be studied and solved. Among them, under high ground stress environment, the bottom arch deformation of soft rock tunnels is more common, which poses a great threat to the safe operation of the tunnel. Therefore, we urgently need to conduct in-depth research on its control technology in order to solve the problem of bottom drum that may be faced during the construction and operation of high ground stress soft rock tunnels.

[0003] At present, the control technology of tunnel floor drum mainly focuses on support reinforcement methods such as floor anchor rods, floor grouting, and closed brackets. The above methods have their own limitations. For example, the reverse bottom arch support method generally requires the tunnel to be fully closed to be effective. The anchor reinforcement method fails for tunnels with floor drums because the surrounding rock at the bottom of the invert arch is broken and the range of the floor drum is uncertain, which cannot guarantee the construction quality of the anchor rods. Moreover, under high ground stress conditions, ordinary anchor rods are difficult to withstand the stress brought by the surrounding rock, and anchor rods often break, which eventually leads to disasters. For deformation in high ground stress soft rock tunnels, the support reinforcement method is used. Due to the large stiffness of the support structure, it is easy to form a large stress concentration near the support structure, and the stress cannot be transferred to the deep, resulting in serious deformation or even failure of the support structure. The treatment effect of the floor drum is not ideal and it is difficult to meet the control requirements.

[0004] The current tunnel floor drum control method has the following main disadvantages:

[0005] 1. Most of them can only passively maintain the bottom structure of the tunnel. Under the conditions of high stress and creep deformation, they cannot give full play to its bearing capacity and maintain the long-term stability of the bottom arch structure of the tunnel in the gently inclined rock layer; 2. The construction process is cumbersome, which not only consumes a lot of manpower and material resources, but also may affect the construction efficiency; 3. It is impossible to effectively improve the stress environment of the tunnel, and it is impossible to protect the tunnel arch structure while releasing the tunnel bottom stress, so as to effectively prevent and control the tunnel bottom drum problem. Summary of the invention

[0006] In view of the above-mentioned deficiencies in the prior art, the creep floor drum control method of the invert arch of a high-geo-stress and gently inclined soft rock traffic tunnel provided by the present invention solves the problems of the existing floor drum control method having complex process and poor floor drum control.

[0007] In order to achieve the above objectives, the technical solution adopted in this scheme is:

[0008] In a first aspect, a method for controlling creep floor heave of an invert arch of a high-stress, slow-inclined soft rock traffic tunnel is provided, which comprises the following steps:

[0009] S1. Collect the geological conditions and stress state of the bottom of the tunnel invert to determine the section of the tunnel where the bottom heave may occur;

[0010] S2. According to the rock mass mechanical parameters, tunnel geometry and support parameters of the tunnel, a three-dimensional numerical model of the tunnel with creep deformation energy release holes of different arrangements is constructed in the section where the tunnel floor heave may occur;

[0011] S3. Use a three-dimensional numerical model to simulate and predict the deformation of the tunnel bottom invert under high ground stress conditions in 100 years, and determine the optimal arrangement of energy release holes based on the deformation of the invert;

[0012] S4, using a method for calculating the stress around the energy release hole to calculate the stress at different positions around the energy release hole, and selecting the minimum value of all stresses as the upper limit of the strength of the creep energy release material filling the energy release hole;

[0013] S5, selecting creep energy release materials according to the upper strength limit value, and introducing them into the three-dimensional numerical model to verify whether the optimal energy release hole arrangement can achieve the bottom drum control effect, if yes, proceed to step S7, otherwise proceed to step S6;

[0014] S6, adjusting the arrangement of the energy release holes until the bottom drum control effect is satisfied, taking the arrangement of the energy release holes satisfying the bottom drum control effect as the final optimal arrangement of the energy release holes, and then proceeding to step S7;

[0015] S7. Energy release holes are arranged in the section where bottom drum may occur according to the optimal arrangement of energy release holes, and plastic tubes filled with the selected creep energy release material are placed in the energy release holes.

[0016] Furthermore, the step S4 further comprises:

[0017] S41. Calculate the radius of the plastic zone of the surrounding rock at the tunnel based on the friction angle of the surrounding rock at the tunnel, the inner and outer radii of the tunnel lining and the support resistance of the invert arch:

[0018]

[0019] Where, R is the radius of the plastic zone; r2 is the outer radius of the lining; c is the cohesion of the surrounding rock; σ Z is the tangential stress when the depth of the energy release hole is R from the tunnel center; P is the invert support resistance; φ is the friction angle of the surrounding rock;

[0020] S42. Calculate the radial stress F of the surrounding rock around the energy release hole at different depths within the plastic zone. r and vertical stress F v :

[0021]

[0022] Where r is the radial distance from the tunnel center at different depths;

[0023] S43. Calculate the radial stress F of the surrounding rock around the energy release hole at different depths within the elastic zone where the energy release hole is located. r and vertical stress F v :

[0024]

[0025] Among them, r c is the maximum radial distance between the bottom of all energy release holes and the center of the tunnel; σ R is the radial stress when the distance between the creep deformation energy release hole and the tunnel center is R;

[0026] S44. According to the geological parameters of the surrounding rock, creep characteristics and tunnel support form, the finite element simulation software is used to draw the radial stress F of each group. r and vertical stress F v The distribution curve of the radial stress F in the z-axis direction is determined based on the distribution curve. r (z) and vertical stress F v (z);

[0027] S45. Select the radial stress F in each group of z-axis directions r (z) and vertical stress F v The minimum value of (z) is taken as the radial stress F of each group r and vertical stress F v The corresponding characteristic stress;

[0028] S46. Select the minimum value among all characteristic stresses and use it as the upper limit of the strength of the creep energy release material filling the energy release holes.

[0029] Furthermore, the expression of the invert support resistance is:

[0030]

[0031] Wherein, μ and E are Poisson’s ratio and elastic modulus of surrounding rock respectively; K l , μ l and E l are the stiffness coefficient, Poisson's ratio and elastic modulus of the invert support structure respectively; r1 is the inner radius of the lining.

[0032] Furthermore, between step S5 and step S6, the process further includes optimizing the diameter of the energy release hole:

[0033] Calculate the deformation of the selected creep energy release material:

[0034] U c =d·ε m

[0035] Among them, U c is the deformation of the creep energy release material; d is the size of the compressible space uniformly distributed inside the creep energy release material;

[0036] The deformation of the creep energy release material is used as the lower limit of the diameter of the energy release hole, and the diameter of the energy release hole is selected according to the lower limit.

[0037] Furthermore, when installing the plastic tube in step S7, the process further includes:

[0038] Before installing the plastic tube, clean the energy release hole and set a first thickness of waterproof binder material at the bottom of the energy release hole; after installing the plastic tube, set a second thickness of sealing concrete at the top of the energy release hole.

[0039] Further, the method for determining the first thickness includes:

[0040] Calculate the compressive strength range of waterproof and adhesive materials when they are not crushed:

[0041] σ m ≥γ.F min

[0042] Among them, σ m is the compressive strength of the material; γ is the material strength design coefficient of the waterproof bonding material, which is 1.2 to 1.5. min is the upper limit of the strength of creep energy release materials;

[0043] According to the compressive strength range of the material, determine the lower limit of the first thickness of the waterproof adhesive material filling:

[0044]

[0045] Among them, h b is the first thickness; F max The stress that waterproof and adhesive materials need to bear;

[0046] According to the lower limit value of the first thickness, the first thickness of the waterproof adhesive material filling is selected.

[0047] Further, the method for determining the second thickness includes:

[0048] According to the foundation conditions at the bottom of the tunnel, calculate the foundation reaction force at the tunnel:

[0049] F b = k·δ

[0050] Among them, F b is the foundation reaction force; k is the foundation reaction force coefficient; δ is the vertical deformation of the tunnel bottom;

[0051] According to the train load and foundation reaction force, the strength range of the sealing concrete is calculated:

[0052] σ c ≥λ·max(Q,F b )

[0053] Among them, σ c is the strength of the plugging concrete; λ is the strength design coefficient of the plugging concrete, which is 1.2 to 1.5; Q is the train load; max is the maximum value;

[0054] According to the strength of the sealing concrete, determine the lower limit of the second thickness of the sealing concrete filling:

[0055]

[0056] Among them, h t is the second thickness;

[0057] The second thickness of the sealing concrete filling is selected according to the lower limit value of the second thickness.

[0058] Furthermore, the arrangement of the energy release holes includes the installation position of the energy release holes, the spacing between adjacent energy release holes, the depth of the energy release holes and the diameter of the energy release holes;

[0059] The optimal arrangement of energy release holes based on the deformation of the arch includes:

[0060] Select an upper arch deformation amount that is smaller than the bottom drum deformation amount allowed by the design. When the selected upper arch deformation amount is 1, the corresponding energy release hole arrangement mode is taken as the optimal energy release hole arrangement mode;

[0061] When the selected upper arch deformation is greater than or equal to 2, multiple evaluation indicators are used to evaluate the energy release hole arrangement corresponding to the upper arch deformation, and the energy release hole arrangement with the highest evaluation score is selected as the optimal energy release hole arrangement.

[0062] In the second aspect, a system is provided for controlling creep floor drum of an invert arch of a high-ground stress, gently inclined soft rock transportation tunnel, which comprises a plurality of energy release holes opened in a tunnel section where floor drum may occur according to an optimal energy release hole arrangement and a plastic tube placed in the energy release hole; the plastic tube is filled with a creep energy release material whose strength is less than the upper limit of the strength of the creep energy release material.

[0063] Furthermore, the energy release holes below the plastic tube are filled with waterproof bindable material, and the energy release holes above the plastic tube are filled with blocking concrete.

[0064] Compared with the prior art, the present invention has the following beneficial effects:

[0065] (1) This scheme can transfer the peak stress of the surrounding rock by excavating creep deformation energy release holes at the bottom of the tunnel and filling them with creep energy release materials, that is, the stress originally concentrated near the tunnel is transferred to the deep part, so that the tunnel is in a stress reduction zone.

[0066] (2) The creep energy release material selected in this scheme is determined based on the geological conditions and stress state of the tunnel, the size of the tunnel and the material mechanical parameters of the surrounding rock. It provides a certain compensation space for the deformation of the tunnel surrounding rock, absorbs part of the deformation, and thus reduces the deformation of the tunnel floor.

[0067] The creep energy release material filled in the plastic tube can be prefabricated by the factory before construction and directly assembled on site during construction. This tunnel bottom drum control method can effectively prevent and control the invert bottom drum phenomenon that often occurs in tunnel engineering at present, and can be promoted and used in related fields.

[0068] (3) The optimal arrangement of energy release holes in this scheme is selected first under high ground stress conditions, which is particularly suitable for gently inclined soft rock high-speed railway tunnels. It has significant effect and applicability in preventing bottom heave deformation caused by surrounding rock creep. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 The present invention is a flowchart of the steps of the method for controlling the creep bottom heave of the invert arch of a high ground stress and gently inclined soft rock transportation tunnel.

[0070] Figure 2 This is a schematic diagram of the elastic and plastic ranges of different depths of creep deformation energy release holes and the stress state analysis of the unit body in this scheme.

[0071] Figure 3 This is the confined compression stress-strain curve of the creep energy release material in this scheme.

[0072] Figure 4 This is a structural schematic diagram of the creep floor heave control system of the high ground stress and slow-inclined soft rock traffic tunnel of this scheme arranged at the bottom of the tunnel lining.

[0073] Figure 5 Schematic diagram of the decomposition of the plastic tube.

[0074] Figure 6 This is a cross-sectional view of the creep floor heave control system of the high-geo-stress, gently inclined soft rock transportation tunnel of this scheme after it is arranged at the bottom of the tunnel lining.

[0075] Among them, 1. lining; 2. sealing concrete; 3. waterproof bonding material; 4. energy release hole; 5. creep energy release structure; 6. plastic pipe; 7. creep energy release material; 8. surrounding rock; 9. depth of energy release hole; 10. spacing between energy release holes; 11. diameter of energy release hole. DETAILED DESCRIPTION

[0076] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0077] refer to Figure 1 , Figure 1 The flowchart of the steps of the creep bottom heave control method of the invert arch of a high ground stress slow-inclined soft rock traffic tunnel is shown; Figure 1 As shown, the method S includes steps S1 to S7.

[0078] In step S1, the geological conditions and stress state of the bottom of the invert of the tunnel are collected to determine the section of the tunnel where the bottom heave may occur; the geological conditions and stress state can be determined through survey.

[0079] The occurrence of floor heave is mainly due to the surrounding rock stress exceeding the bearing capacity of the invert, as well as the long-term creep effect and insufficient structural support. Therefore, this scheme determines the section of the tunnel where floor heave may occur based on the following conditions:

[0080] 1. High ground stress conditions of surrounding rock: Under high ground stress environment, when the surrounding rock stress exceeds the bearing capacity of the invert and supporting structure, it is easy to cause bottom heave and stress concentration areas. For example, when the tunnel passes through complex geological conditions (such as faults or weak interlayers), the stress concentration of the surrounding rock will produce greater pressure on the invert, increasing the risk of bottom heave.

[0081] 2. Creep effect of surrounding rock: In rock formations with obvious creep effect (such as soft rock or rock formation with plastic deformation characteristics), the surrounding rock will slowly deform under long-term load. This long-term accumulated deformation will gradually transfer more force to the invert, resulting in bottom drum phenomenon. Stress redistribution and long-term creep deformation will intensify the mechanical effect between the surrounding rock and the invert, causing the deformation at the bottom of the invert to gradually accumulate, eventually leading to bottom drum.

[0082] 3. Insufficient or ineffective tunnel support: The support system is not designed properly or is insufficiently strong, which cannot effectively resist the high ground stress of the surrounding rock and easily leads to bottom bulge of the invert.

[0083] 4. Insufficient rigidity of the invert structure: If the rigidity of the invert structure is not designed enough and cannot withstand the load transmitted to the bottom of the tunnel, the uneven stress distribution will cause bottom bulge, and the deformation may continue to increase, especially under creep conditions.

[0084] 5. Construction technology and quality: unreasonable construction technology will cause disturbance of the surrounding rock, increase the complexity of the force of the invert, and may cause bottom drum. Improper arrangement of the energy release device (such as unreasonable spacing or depth design) will affect its adjustment effect, resulting in the invert being unable to effectively relieve the surrounding rock stress and increasing the risk of bottom drum.

[0085] In step S2, according to the rock mass mechanical parameters, tunnel geometry and support parameters of the high ground stress tunnel, a three-dimensional numerical model of the tunnel with creep deformation energy release holes of different arrangements is constructed in the section of the tunnel where the bottom heave may occur.

[0086] In step S3, a three-dimensional numerical model is used to simulate and predict the upward deformation of the tunnel bottom invert under high ground stress conditions for 100 years, and the optimal arrangement of energy release holes is determined based on the upward deformation.

[0087] During implementation, the preferred arrangement of energy release holes in this scheme includes the installation position of the energy release holes, the spacing between adjacent energy release holes, the depth of the energy release holes and the diameter of the energy release holes; the diameter of the energy release holes is selected within a preset range. The selection process of each parameter in the arrangement of energy release holes is as follows:

[0088] Determine the location of the creep deformation energy release hole: According to the stress distribution results, determine the area with stress concentration and large deformation as the location of the creep deformation energy release hole, and give priority to drilling the stress concentration area at the bottom of the invert;

[0089] Determine the creep deformation energy release hole spacing W: According to the numerical simulation results, analyze the effects of different spacings on stress release and deformation control, and optimize the creep deformation energy release hole spacing to achieve the best stress release effect while controlling the deformation within the allowable range;

[0090] Determine the depth H of the creep deformation energy release hole: Determine the depth of the creep deformation energy release hole according to the stress release effect to achieve uniform stress release and control creep deformation;

[0091] Determine the diameter D of the creep deformation energy release hole: Determine the diameter of the creep deformation energy release hole according to the filling material and pipeline size to ensure that the diameter of the creep deformation energy release hole can accommodate the filling material and pipeline and is constructible.

[0092] In order to facilitate the explanation of the energy hole arrangement, this scheme Figure 6 In the figure, the energy release hole spacing 10 , the energy release hole depth 9 and the energy release hole diameter 11 are marked accordingly. The energy release holes 4 are opened in the surrounding rock 8 below the lining 1 .

[0093] Regarding the diameter of the energy release hole: Based on similar geological conditions or experience in tunnel engineering, a reasonable borehole diameter range (such as the common 100-300mm) is selected. In the simulation, the disturbance of the surrounding rock stress field by boreholes of different diameters is analyzed, and the diameter that can effectively reduce the stress concentration of the surrounding rock but not excessively disturb the stability of the surrounding rock is selected. In the preliminary numerical simulation, the borehole diameter is used as a variable. The goal is to explore the influence of diameter on stress distribution and invert deformation, and to provide a preliminary basis for the final plan. The compression behavior of the energy release material is not involved at this time.

[0094] The final drilling diameter needs to meet the following conditions: ① be able to accommodate the filled energy-releasing material (including the plastic tube); ② provide enough material compression space to achieve the expected energy-releasing effect. Because the selection of the diameter is not entirely dependent on the compression performance of the energy-releasing material, the diameter range determined by the preliminary simulation is subsequently verified and fine-tuned in combination with the compression requirements of the energy-releasing material.

[0095] The optimal arrangement of energy release holes based on the deformation of the arch includes:

[0096] Select an upper arch deformation amount that is smaller than the bottom drum deformation amount allowed by the design. When the selected upper arch deformation amount is 1, the corresponding energy release hole arrangement mode is taken as the optimal energy release hole arrangement mode;

[0097] When the selected upper arch deformation is greater than or equal to 2, multiple evaluation indicators are used to evaluate the energy release hole arrangement corresponding to the upper arch deformation, and the energy release hole arrangement with the highest evaluation score is selected as the optimal energy release hole arrangement.

[0098] Multiple evaluation indicators include stress uniformity, structural stability, construction feasibility, material economy, long-term creep effect, and environmental and maintenance impact. Based on these evaluation indicators, different energy release hole arrangements are quantitatively evaluated through multi-objective optimization method or weight analysis. After determining the weight of each indicator, the energy release hole arrangement with the highest comprehensive score is selected as the optimal energy release hole arrangement.

[0099] Based on numerical simulation, this scheme analyzes the reaction force generated on the bottom of the invert by different creep deformation energy release hole arrangements and compares it with the ultimate bearing capacity of the invert. At the same time, it measures the upward deformation of the invert at the bottom of the tunnel under the creep condition of 100 years and the bottom drum deformation allowed by the design to ensure that the bearing capacity and deformation of the invert are within the allowable range.

[0100] In step S4, a method for calculating stress around the energy release hole is used to calculate stresses at different positions around the energy release hole, and the minimum value of all stresses is selected as the upper limit of the strength of the creep energy release material filling the energy release hole.

[0101] The preferred creep energy release material in this scheme is EPP concrete. The performance and strength of EPP concrete material are measured by lateral confined compression test. The lateral confined compression stress-strain curve can be referred to Figure 3 .

[0102] In one embodiment of the present invention, the step S4 further comprises:

[0103] S41. Calculate the radius of the plastic zone of the surrounding rock at the tunnel based on the friction angle of the surrounding rock at the tunnel, the inner and outer radii of the tunnel lining and the support resistance of the invert arch:

[0104]

[0105] Where, R is the radius of the plastic zone; r2 is the outer radius of the lining; c is the cohesion of the surrounding rock; σ Z is the tangential stress when the depth of the energy release hole is R from the tunnel center; P is the invert support resistance; φ is the friction angle of the surrounding rock;

[0106] S42. Calculate the radial stress F of the surrounding rock around the energy release hole at different depths within the plastic zone. r and vertical stress F v :

[0107]

[0108] Where r is the radial distance from the tunnel center at different depths;

[0109] S43. Calculate the radial stress F of the surrounding rock around the energy release hole at different depths within the elastic zone where the energy release hole is located. r and vertical stress F v :

[0110]

[0111] Among them, r c is the maximum radial distance between the bottom of all energy release holes and the center of the tunnel; σ R is the radial stress when the distance between the creep deformation energy release hole and the tunnel center is R;

[0112] S44. According to the geological parameters of the surrounding rock, creep characteristics and tunnel support form, the finite element simulation software is used to draw the radial stress F of each group. r and vertical stress F v The distribution curve of the radial stress F in the z-axis direction is determined based on the distribution curve. r (z) and vertical stress F v (z);

[0113] S45. Select the radial stress F in each group of z-axis directions r (z) and vertical stress Fv The minimum value of (z) is taken as the radial stress F of each group r and vertical stress F v The corresponding characteristic stress;

[0114] S46. Select the minimum value among all characteristic stresses and use it as the upper limit of the strength of the creep energy release material filling the energy release holes.

[0115] In the process of determining the upper limit of the strength of creep energy release materials, the analysis of the elastic and plastic ranges of creep deformation energy release holes at different depths and the stress state of the unit body can be referred to Figure 2 .

[0116] This scheme adopts the above method to select creep energy release materials that meet the strength requirements and have compression properties, ensure that the strength of the selected material is less than the minimum value of the circumferential stress at the filling point, so as to achieve coordinated deformation with the surrounding rock, and conduct experimental tests on the selected creep energy release materials to verify their strength, energy absorption and compression properties, and test the stability and durability of the materials under long-term creep conditions.

[0117] During implementation, the preferred expression of the invert support resistance in this scheme is:

[0118]

[0119] Wherein, μ and E are Poisson’s ratio and elastic modulus of surrounding rock respectively; K l , μ l and E l are the stiffness coefficient, Poisson's ratio and elastic modulus of the invert support structure respectively; r1 is the inner radius of the lining.

[0120] In step S5, creep energy release materials are selected according to the upper strength limit value, and introduced into the three-dimensional numerical model to verify whether the optimal energy release hole arrangement can achieve the bottom drum control effect. If so, proceed to step S7, otherwise proceed to step S6;

[0121] The method for determining whether the bottom drum control effect is achieved can be: by simulating and predicting the upward arch deformation of the tunnel bottom invert under 100-year conditions, and comparing the upward arch deformation with the design allowable bottom drum deformation. If it is less than the design allowable bottom drum deformation, it means that the bottom drum control effect is achieved, otherwise it is considered that it is not achieved.

[0122] In step S6, the arrangement of the energy release holes is adjusted until the bottom drum control effect is satisfied, and the arrangement of the energy release holes that satisfies the bottom drum control effect is taken as the final optimal arrangement of the energy release holes, and then the process proceeds to step S7;

[0123] In step S7, energy release holes are arranged in the section where bottom drum may occur according to the optimal arrangement of energy release holes, and plastic tubes filled with the selected creep energy release material are placed in the energy release holes.

[0124] According to the optimal arrangement of energy release holes and construction conditions determined by numerical simulation calculations, during the support stage, a drilling rig is used to drill holes perpendicular to the bottom plate at the corresponding position of the tunnel bottom plate. After the drilling is completed, the hole depth needs to be checked and the hole needs to be cleaned with high-pressure air; then the plastic pipe can be installed.

[0125] The plastic tube is used to contain compressible materials and has good compression performance and durability; the creep energy release material has good compression performance and energy absorption capacity, and can continuously relieve the surrounding rock stress under long-term high ground stress and creep conditions. The outer diameter and thickness of the plastic tube 6 are determined according to the diameter 11 of the creep deformation energy release hole to ensure that it can be smoothly placed in the creep deformation energy release hole and can be in close contact with it.

[0126] The creep energy release material is filled in the plastic tube to form a creep energy release structure 5 under high ground stress. The filling process must ensure that the buffer compression material is evenly distributed without gaps and movement. The pipe is installed in the creep deformation energy release hole at the tunnel construction site to ensure that the creep energy release structure 5 is in close contact with the wall of the energy release hole to prevent it from moving, which can be used to release stress and suppress bottom drum.

[0127] During implementation, the solution further includes optimizing the diameter of the energy release hole between step S5 and step S6:

[0128] Calculate the deformation of the selected creep energy release material:

[0129] U c =d·ε m

[0130] Among them, U c is the deformation of the creep energy release material; d is the size of the compressible space uniformly distributed inside the creep energy release material;

[0131] The deformation of the creep energy release material is used as the lower limit of the diameter of the energy release hole, and the diameter of the energy release hole is selected according to the lower limit. Specifically, as long as the diameter of the energy release hole is smaller than the lower limit, it will suffice.

[0132] Since the diameter of the energy release hole is selected within a preset range, which is generally determined by experience, the obtained diameter of the energy release hole is relatively inaccurate. This scheme determines the diameter of the energy release hole in the above manner, taking into account the strength of the selected creep energy release material. In this way, the energy release hole obtained is more suitable for specific projects to adapt to the bottom drum control.

[0133] In order to facilitate the stability of the creep energy-releasing material filled in the plastic tube in the energy-releasing hole, the present solution preferably further comprises the following steps when installing the plastic tube in step S7:

[0134] Before installing the plastic tube, clean the energy release hole and set a first thickness of waterproof binder material at the bottom of the energy release hole; after installing the plastic tube, set a second thickness of sealing concrete at the top of the energy release hole.

[0135] The waterproof cementable material filling can withstand the bottom stress and prevent water from penetrating. Before injecting the material, the soil and gravel at the bottom of the borehole should be cleaned to ensure that the sealing material can closely contact the bottom rock and soil. The preferred sealing concrete in this scheme is geopolymer concrete.

[0136] During implementation, the method for determining the first thickness of this solution preferably includes:

[0137] Calculate the compressive strength range of waterproof and adhesive materials when they are not crushed:

[0138] σ m ≥γ.F min

[0139] Among them, σ m is the compressive strength of the material; γ is the material strength design coefficient of the waterproof bonding material, which is 1.2 to 1.5. min is the upper limit of the strength of creep energy release materials;

[0140] According to the compressive strength range of the material, determine the lower limit of the first thickness of the waterproof adhesive material filling:

[0141]

[0142] Among them, h b is the first thickness; F max The stress that waterproof and adhesive materials need to bear;

[0143] According to the lower limit value of the first thickness, the first thickness of the waterproof bindable material is selected. Specifically, as long as the selected first thickness satisfies less than or equal to the lower limit value of the first thickness, it will be sufficient.

[0144] During implementation, the method for determining the second thickness of this solution preferably includes:

[0145] According to the foundation conditions at the bottom of the tunnel, calculate the foundation reaction force at the tunnel:

[0146] F b = k·δ

[0147] Among them, F b is the foundation reaction force; k is the foundation reaction force coefficient; δ is the vertical deformation of the tunnel bottom;

[0148] According to the train load and foundation reaction force, the strength range of the sealing concrete is calculated:

[0149] σ c≥λ·max(Q,F b )

[0150] Among them, σ c is the strength of the plugging concrete; λ is the strength design coefficient of the plugging concrete, which is 1.2 to 1.5; Q is the train load; max is the maximum value;

[0151] According to the strength of the sealing concrete, determine the lower limit of the second thickness of the sealing concrete filling:

[0152]

[0153] Among them, h t is the second thickness;

[0154] According to the lower limit value of the second thickness, the second thickness of the sealing concrete filling is selected; specifically, as long as the selected second thickness satisfies less than or equal to the lower limit value of the second thickness, it will be sufficient.

[0155] exist Figure 4 and Figure 6 This scheme shows a stereoscopic view and a cross-sectional view of the creep bottom drum control system of the high ground stress slow-inclined soft rock traffic tunnel after it is arranged at the bottom of the tunnel lining 1, as shown in FIG. Figure 4-6 As shown, the present scheme also provides a system for controlling the creep bottom drum of an invert arch of a high-stress, gently inclined soft rock transportation tunnel, which comprises a plurality of energy release holes 4 opened in the surrounding rock 8 in a section of the tunnel where bottom drum may occur according to an optimal energy release hole arrangement and a plastic tube 6 placed in the energy release hole 4, and a creep energy release structure 5 is formed after the creep energy release material 7 is filled into the plastic tube 6; the plastic tube 6 is filled with a creep energy release material whose strength is less than the upper limit of the strength of the creep energy release material.

[0156] like Figure 5 As shown, the number of sections required for the plastic tube 5 is determined according to the depth H of the energy release hole at the tunnel construction site, and after being assembled in sections using an assembly process, it is placed in the energy release hole 4, and it is ensured that the plastic tube 6 is in close contact with the wall of the energy release hole 4 to prevent it from moving. During the construction of the energy release hole 4, water accumulation in the hole should be prevented, and the plastic tube 6 should have the characteristics of being compressed and deformed without being damaged to affect waterproofing, and at the same time ensure that the materials used will not cause pollution to the surrounding rock environment.

[0157] During implementation, the energy release hole below the plastic tube 6 of this scheme is filled with waterproof bindable material 3, which is pumped into the energy release hole 4 by pumping to seal the bottom of the energy release hole 4; after the plastic tube 6 is installed, considering the foundation reaction force and the upper train load, high-strength sealing concrete 2 is used to seal the top of the energy release hole 4, and the thickness of the sealing material is determined according to the diameter of the energy release hole 4 and the upper structure load.

[0158] Selection of bottom plugging materials: Through geological exploration and numerical simulation, combined with theoretical analysis, calculate the stress distribution and deformation of the bottom plugging material under maximum ground stress; select materials with high compressive strength, certain ductility and deformation capacity to ensure that no damage or plastic deformation will occur under maximum ground stress.

[0159] In summary, this scheme can effectively prevent and control the floor heave problem of high-stress slow-inclined soft rock transportation tunnels. It also has significant applicability and effect on the floor heave deformation caused by surrounding rock creep, avoiding the damage of the invert structure and reducing the cost of later tunnel maintenance.

Claims

1. A method for controlling creep floor heave of an invert arch in a high-stress, slow-inclined soft rock traffic tunnel, characterized in that: Includes steps: S1. Collect the geological conditions and stress state of the bottom of the tunnel invert to determine the section of the tunnel where the bottom heave may occur; S2. According to the rock mass mechanical parameters, tunnel geometry and support parameters of the tunnel, a three-dimensional numerical model of the tunnel with creep deformation energy release holes of different arrangements is constructed in the section where the tunnel floor heave may occur; S3. Use a three-dimensional numerical model to simulate and predict the deformation of the tunnel bottom invert under high ground stress conditions in 100 years, and determine the optimal arrangement of energy release holes based on the deformation of the invert; S4, using a method for calculating the stress around the energy release hole to calculate the stress at different positions around the energy release hole, and selecting the minimum value of all stresses as the upper limit of the strength of the creep energy release material filling the energy release hole; S5, selecting creep energy release materials according to the upper strength limit value, and introducing them into the three-dimensional numerical model to verify whether the optimal energy release hole arrangement can achieve the bottom drum control effect, if yes, proceed to step S7, otherwise proceed to step S6; S6, adjusting the arrangement of the energy release holes until the bottom drum control effect is satisfied, taking the arrangement of the energy release holes satisfying the bottom drum control effect as the final optimal arrangement of the energy release holes, and then proceeding to step S7; S7, adjusting the arrangement of the energy release holes until the bass drum control effect is satisfied, and taking the arrangement of the energy release holes that satisfies the bass drum control effect as the final optimal arrangement of the energy release holes.

2. The method for controlling creep floor heave of an invert arch of a high-stress, slow-inclined soft rock traffic tunnel according to claim 1 is characterized in that: The step S4 further comprises: S41. Calculate the radius of the plastic zone of the surrounding rock at the tunnel based on the friction angle of the surrounding rock at the tunnel, the inner and outer radii of the tunnel lining and the support resistance of the invert arch: Where, R is the radius of the plastic zone; r2 is the outer radius of the lining; c is the cohesion of the surrounding rock; σ Z is the tangential stress when the depth of the energy release hole is R from the tunnel center; P is the invert support resistance; φ is the friction angle of the surrounding rock; S42. Calculate the radial stress F of the surrounding rock around the energy release hole at different depths within the plastic zone. r and vertical stress F v : Where r is the radial distance from the tunnel center at different depths; S43. Calculate the radial stress F of the surrounding rock around the energy release hole at different depths within the elastic zone where the energy release hole is located. r and vertical stress F v : Among them, r c is the maximum radial distance between the bottom of all energy release holes and the center of the tunnel; σ R is the radial stress when the distance between the creep deformation energy release hole and the tunnel center is R; S44. According to the geological parameters of the surrounding rock, creep characteristics and tunnel support form, the finite element simulation software is used to draw the radial stress F of each group. r and vertical stress F v The distribution curve of the radial stress F in the z-axis direction is determined based on the distribution curve. r (z) and vertical stress F v (z); S45. Select the radial stress F in each group of z-axis directions r (z) and vertical stress F v The minimum value of (z) is taken as the radial stress F of each group r and vertical stress F v The corresponding characteristic stress; S46. Select the minimum value among all characteristic stresses and use it as the upper limit of the strength of the creep energy release material filling the energy release holes.

3. The method for controlling creep floor heave of an invert arch of a high-stress, slow-inclined soft rock traffic tunnel according to claim 2 is characterized in that: The expression of the invert support resistance is: Wherein, μ and E are Poisson’s ratio and elastic modulus of surrounding rock respectively; K l , μ l and E l are the stiffness coefficient, Poisson's ratio and elastic modulus of the invert support structure respectively; r1 is the inner radius of the lining.

4. The method for controlling creep floor heave of an invert arch of a high-stress, slow-inclined soft rock traffic tunnel according to claim 1 is characterized in that: The process between step S5 and step S6 also includes optimizing the diameter of the energy release hole: Calculate the deformation of the selected creep energy release material: U c =d·e m Among them, U c is the deformation of the creep energy release material; d is the size of the compressible space uniformly distributed inside the creep energy release material; The deformation of the creep energy release material is used as the lower limit of the diameter of the energy release hole, and the diameter of the energy release hole is selected according to the lower limit.

5. The method for controlling creep floor heave of an invert arch of a high-stress, slow-inclined soft rock traffic tunnel according to claim 2 is characterized in that: When installing the plastic tube in step S7, the method further includes: Before installing the plastic tube, clean the energy release hole and set a first thickness of waterproof bindable material at the bottom of the energy release hole; after installing the plastic tube, set a second thickness of sealing concrete at the top of the energy release hole.

6. The method for controlling creep floor heave of an invert arch of a high-stress, slow-inclined soft rock traffic tunnel according to claim 5 is characterized in that: The method for determining the first thickness includes: Calculate the compressive strength range of waterproof and adhesive materials when they are not crushed: s m ≥γ.F min Among them, σ m is the compressive strength of the material; γ is the material strength design coefficient of the waterproof bonding material, which is 1.2 to 1.

5. min is the upper limit of the strength of creep energy release materials; According to the compressive strength range of the material, determine the lower limit of the first thickness of the waterproof adhesive material filling: Among them, h b is the first thickness; F max The stress that waterproof and adhesive materials need to bear; According to the lower limit value of the first thickness, the first thickness of the waterproof adhesive material filling is selected.

7. The method for controlling creep floor heave of an invert arch of a high-stress, slow-inclined soft rock traffic tunnel according to claim 5 is characterized in that: The method for determining the second thickness includes: According to the foundation conditions at the bottom of the tunnel, calculate the foundation reaction force at the tunnel: F b =k·δ Among them, F b is the foundation reaction force; k is the foundation reaction force coefficient; δ is the vertical deformation of the tunnel bottom; According to the train load and foundation reaction force, the strength range of the sealing concrete is calculated: σ c ≥λ·max(Q,F b ) Among them, σ c is the strength of the plugging concrete; λ is the strength design coefficient of the plugging concrete, which is 1.2 to 1.5; Q is the train load; max is the maximum value; According to the strength of the sealing concrete, determine the lower limit of the second thickness of the sealing concrete filling: Among them, h t is the second thickness; The second thickness of the sealing concrete filling is selected according to the lower limit value of the second thickness.

8. The method for controlling creep floor heave of an invert arch in a high-stress, slow-inclined soft rock traffic tunnel according to claim 1 is characterized in that: The arrangement of the energy release holes includes the installation position of the energy release holes, the spacing between adjacent energy release holes, the depth of the energy release holes and the diameter of the energy release holes; The optimal arrangement of energy release holes based on the deformation of the arch includes: Select an upper arch deformation amount that is smaller than the bottom drum deformation amount allowed by the design. When the selected upper arch deformation amount is 1, the corresponding energy release hole arrangement mode is taken as the optimal energy release hole arrangement mode; When the selected upper arch deformation is greater than or equal to 2, multiple evaluation indicators are used to evaluate the energy release hole arrangement corresponding to the upper arch deformation, and the energy release hole arrangement with the highest evaluation score is selected as the optimal energy release hole arrangement.

9. A system applied to the method for controlling creep floor heave of an invert arch of a high-stress slow-inclined soft rock traffic tunnel according to any one of claims 1 to 8, characterized in that: It comprises a plurality of energy release holes opened in a tunnel section where bottom drum may occur according to an optimal energy release hole arrangement and a plastic tube placed in the energy release holes; the plastic tube is filled with a creep energy release material whose strength is less than the upper limit of the strength of the creep energy release material.

10. The system according to claim 9, characterized in that The energy release holes below the plastic tube are filled with waterproof bindable materials, and the energy release holes above the plastic tube are filled with blocking concrete.

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