High stress slow soft rock traffic tunnel inverted arch creep floor drum control method and system

Abstract

The application discloses a high ground stress slow-inclined soft rock traffic tunnel inverted arch creep floor heave control method and system, the floor heave control method comprises the following steps: determining a section where floor heave is likely to occur in a tunnel, and determining an optimal energy release hole arrangement mode in the section where floor heave is likely to occur; calculating the stress at different positions around the energy release hole by adopting an energy release hole surrounding stress calculation method, and selecting the minimum value of all the stresses as the upper limit value of the strength of a creep energy release material filled in the energy release hole; selecting the creep energy release material, and introducing a three-dimensional numerical model to verify whether the optimal energy release hole arrangement mode reaches a floor heave control effect; if not, adjusting the energy release hole arrangement mode until the floor heave control effect is reached; and when the floor heave control effect is reached, setting the energy release hole according to the optimal energy release hole arrangement mode in the section where floor heave is likely to occur, and placing a plastic pipe filled with the selected creep energy release material in the energy release hole.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tunnel engineering support, in particular to a high ground stress soft rock traffic tunnel invert creep floor heave control method and system. BACKGROUND

[0002] With the continuous improvement of tunnel construction technology, China's tunnels and underground engineering have developed rapidly and achieved remarkable results. China is currently the world's largest tunnel country in terms of the number of tunnels, construction scale, and development speed. However, with the planning and construction of the Sichuan-Tibet Railway, a series of construction challenges such as special geology and climate, high altitude, high ground stress, permafrost in cold regions, broken faults, and ecological protection need to be researched and solved. Among them, under high ground stress, soft rock tunnel bottom arch deformation is common, which poses a great threat to the safe operation of the tunnel, so we urgently need to conduct in-depth research on its control technology to solve the possible floor heave problems during the construction and operation of high ground stress soft rock tunnels.

[0003] Current tunnel floor heave control techniques mainly rely on floor anchor rods, floor grouting, and closed support reinforcement methods. These methods have their own limitations. For example, the inverted arch support method generally requires the tunnel to be fully enclosed to be effective. The anchor rod reinforcement method fails to ensure the construction quality of the anchor rod due to the broken surrounding rock at the bottom of the invert and the uncertainty of the floor heave range. Moreover, in high ground stress conditions, ordinary anchor rods are difficult to withstand the stress from the surrounding rock, often leading to anchor rod breakage and ultimately resulting in disasters. For deformation in high ground stress soft rock tunnels, support reinforcement methods are difficult to achieve the desired control requirements due to the large stress concentration near the support structure and the inability of the stress to transfer to the deep part, leading to severe deformation or even failure of the support structure, and the floor heave control effect is not ideal.

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

[0005] 1. Most of them can only passively maintain the tunnel bottom structure, and under high stress and creep deformation conditions, they cannot fully utilize their bearing capacity and maintain the long-term stability of the invert structure of the soft rock tunnel; 2. The construction process is complicated, not only consuming a lot of manpower and resources, but also affecting construction efficiency; 3. It cannot effectively improve the stress environment of the tunnel and protect the tunnel invert structure while releasing the stress at the bottom of the tunnel, thereby effectively preventing and controlling the tunnel floor heave problem. SUMMARY

[0006] To overcome the above-mentioned deficiencies in the prior art, the high ground stress soft rock traffic tunnel invert creep floor heave control method provided by the present application solves the problem of complex process and poor floor heave control of the existing floor heave control method.

[0007] To achieve the above object, the technical scheme adopted by the present application is:

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

[0009] S1, collecting the geological conditions and stress state of the bottom of the inverted arch of the tunnel to determine the section of the tunnel where the floor heave is likely to occur;

[0010] S2, constructing a three-dimensional numerical model of the tunnel with different arrangement forms of creep deformation energy release holes in the section of the tunnel where the floor heave is likely to occur according to the rock mass mechanical parameters, tunnel geometry and support parameters of the tunnel;

[0011] S3, using the three-dimensional numerical model to simulate and predict the upward deformation of the tunnel bottom inverted arch under high ground stress conditions for 100 years, and determining the optimal energy release hole arrangement based on the upward deformation;

[0012] S4, calculating the stress at different positions around the energy release hole using the energy release hole surrounding stress calculation method, and selecting the minimum value of all stresses as the upper limit of the strength of the creep energy release material filled in the energy release hole;

[0013] S5, selecting a creep energy release material according to the upper limit of the strength, introducing it into the three-dimensional numerical model to verify whether the optimal energy release hole arrangement achieves the floor heave control effect, if yes, entering step S7, otherwise entering step S6;

[0014] S6, adjusting the energy release hole arrangement until the floor heave control effect is met, and taking the energy release hole arrangement that meets the floor heave control effect as the final optimal energy release hole arrangement, and then entering step S7;

[0015] S7, setting the energy release hole according to the optimal energy release hole arrangement in the section where the floor heave is likely to occur, and placing a plastic pipe filled with the selected creep energy release material in the energy release hole.

[0016] Further, the step S4 further comprises:

[0017] S41, calculating the plastic zone radius of the surrounding rock at the tunnel according to the friction angle of the surrounding rock at the tunnel, the inner and outer radii of the lining and the inverted arch support resistance:

[0018]

[0019] wherein R is the plastic zone radius; 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 center of the tunnel; P is the inverted arch support resistance; and φ is the friction angle of the surrounding rock;

[0020] S42, in the plastic zone range, the radial stress F of the surrounding rock around the energy release hole at different depths is calculated r and the vertical stress F v :

[0021]

[0022] Wherein, r is the radial distance from the center of the tunnel at different depths;

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

[0024]

[0025] Wherein, r c is the maximum value of the radial distance from the center of the tunnel at the bottom of all energy release holes; σ R is the radial stress of the creep deformation energy release hole when the depth is R from the center of the tunnel;

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

[0027] S45, the minimum value of the radial stress F r (z) and the vertical stress F v (z) in the z-axis direction of each group is selected as the characteristic stress corresponding to the radial stress F r and the vertical stress F v .

[0028] S46, the minimum value of all characteristic stresses is selected, and it is used as the upper limit value of the strength of the creep energy release material filled in the energy release hole.

[0029] Further, the expression of the inverted arch support resistance is:

[0030]

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

[0032] Further, between step S5 and step S6, the diameter of the energy release hole is also optimized:

[0033] The deformation of the selected creep energy release material is calculated:

[0034] U c = d·ε m

[0035] wherein 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] Further, when installing the plastic pipe in step S7, the following steps are also included:

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

[0039] Further, the determination method of the first thickness includes:

[0040] The material compressive strength range of the waterproof cementable material when it is not crushed is calculated:

[0041] σ m ≥ γ·F min

[0042] wherein σ m is the material compressive strength; γ is the material strength design coefficient of the waterproof cementable material, with a value of 1.2-1.5, and F min is the upper limit of the strength of the creep energy release material;

[0043] According to the material compressive strength range, the lower limit of the first thickness of the waterproof cementable material is determined:

[0044]

[0045] wherein h b is the first thickness; F max is the stress required to be borne by the waterproof cementable material;

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

[0047] Further, the determination method of the second thickness includes:

[0048] According to the foundation conditions at the bottom of the tunnel, the foundation reaction at the tunnel is calculated:

[0049] F b =k*delta

[0050] Wherein, F b is the ground reaction force; k is the ground reaction force coefficient; delta is the vertical deformation of the tunnel bottom;

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

[0052] sigma c >=lambda*max(Q,F b )

[0053] Wherein, sigma c is the strength of the blocking concrete; lambda is the strength design coefficient of the blocking concrete, and the value is 1.2-1.5; Q is the train load; max is the maximum value;

[0054] According to the strength of the blocking concrete, the lower limit value of the second thickness of the blocking concrete filling is determined:

[0055]

[0056] Wherein, h t is the second thickness;

[0057] According to the lower limit value of the second thickness, the second thickness of the blocking concrete filling is selected.

[0058] Further, the energy release hole arrangement mode includes the installation position of the energy release hole, the spacing of adjacent energy release holes, the depth of the energy release hole and the diameter of the energy release hole;

[0059] The optimal energy release hole arrangement mode is determined based on the upward arch deformation amount, which includes:

[0060] Select the upward arch deformation amount less than the design allowed bottom drum deformation amount, and when the number of selected upward arch deformation amounts is 1, the corresponding energy release hole arrangement mode is selected as the optimal energy release hole arrangement mode;

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

[0062] In the second aspect, a system for controlling the upward arch creep bottom drum of a high ground stress and gently inclined soft rock traffic tunnel is provided, which includes a plurality of energy release holes opened in the section of the tunnel where the bottom drum may occur according to the optimal energy release hole arrangement mode and a plastic pipe placed in the energy release hole; the plastic pipe is filled with a creep energy release material with a strength less than the upper limit value of the strength of the creep energy release material.

[0063] Further, the energy releasing hole below the plastic pipe is filled with waterproof cementable material, and the energy releasing hole above the plastic pipe is filled with blocking concrete.

[0064] Compared with the prior art, the application has the following advantages:

[0065] (1) The method of the application can transfer the stress peak of surrounding rock by excavating the creep deformation energy releasing hole at the bottom of the tunnel and filling the creep energy releasing material, so that the stress originally concentrated near the tunnel is transferred to the deep part, and thus the tunnel is in a stress reduction area.

[0066] (2) The creep energy releasing material selected by the application is determined according to the geological conditions and stress state of the tunnel, and the size and material mechanics parameters of the surrounding rock of the tunnel, so as to provide a certain compensation space for the deformation of the tunnel surrounding rock, absorb a part of the deformation, and thus reduce the deformation of the tunnel bottom heave.

[0067] The creep energy releasing material filled in the plastic pipe can be prefabricated by the factory before construction, and directly assembled on site during construction. The tunnel bottom heave control method can effectively prevent and control the inverted arch bottom heave phenomenon often occurring in the current tunnel engineering, and can be widely used in the related field.

[0068] (3) The optimal energy releasing hole arrangement mode of the application is selected under high stress conditions, and is especially suitable for the slow-dipping soft rock high-speed railway tunnel, and has remarkable effect and applicability for preventing the bottom heave deformation caused by the creep of surrounding rock. BRIEF DESCRIPTION OF DRAWINGS

[0069] Figure 1 The step flow chart of the inverted arch creep bottom heave control method for the high stress slow-dipping soft rock traffic tunnel.

[0070] Figure 2 The analysis diagram of the stress state of the unit body in different depth elastic-plastic ranges of the creep deformation energy releasing hole of the application.

[0071] Figure 3 The stress-strain curve diagram of the creep energy releasing material of the application.

[0072] Figure 4 The structure diagram of the inverted arch creep bottom heave control system of the high stress slow-dipping soft rock traffic tunnel of the application arranged at the bottom of the lining of the tunnel.

[0073] Figure 5 The exploded view of the plastic pipe.

[0074] Figure 6 The cross-sectional view of the inverted arch creep bottom heave control system of the high stress slow-dipping soft rock traffic tunnel of the application arranged at the bottom of the lining of the tunnel.

[0075] Wherein, 1, lining; 2, blocking concrete; 3, waterproof cementable material; 4, energy-releasing hole; 5, creep energy-releasing structure; 6, plastic pipe; 7, creep energy-releasing material; 8, surrounding rock; 9, energy-releasing hole depth; 10, energy-releasing hole spacing; 11, energy-releasing hole diameter. DETAILED DESCRIPTION

[0076] The specific embodiments of the present application are described below to facilitate the understanding of the present application for those skilled in the art, but it should be clear that the present application is not limited to the scope of the specific embodiments, and for those skilled in the art, any changes that are obvious within the spirit and scope of the present application as defined and determined by the appended claims are within the scope of the present application.

[0077] REFERENCE Figure 1 , Figure 1 A step flow chart of the method for controlling the creep bottom heave of the inverted arch of a high-stress and gently-inclined soft rock traffic tunnel is shown; as shown in the figure, Figure 1 The method S includes steps S1-S7.

[0078] In step S1, the geological conditions and stress state of the bottom of the inverted arch of the tunnel are collected, and the section of the tunnel where the bottom heave is likely to occur is determined; the geological conditions and stress state can be determined by survey.

[0079] The occurrence of the bottom heave phenomenon is mainly due to the fact that the stress of the surrounding rock exceeds the bearing capacity of the inverted arch, and the long-term creep effect and insufficient structural support, etc. Therefore, when determining the section of the tunnel where the bottom heave is likely to occur, the following conditions are considered:

[0080] 1. High stress condition of surrounding rock: in a high stress environment, when the stress of the surrounding rock exceeds the bearing capacity of the inverted arch and the supporting structure, it is easy to cause the bottom heave. The stress concentration area, for example, when the tunnel passes through complex geological conditions (such as faults or weak interlayers), the stress concentration of the surrounding rock will generate more pressure on the inverted arch, increasing the risk of bottom heave.

[0081] 2. Creep effect of surrounding rock: in rock layers with obvious creep effect (such as soft rock or rock layers with plastic deformation characteristics), the surrounding rock will produce slow deformation under long-term load. This long-term cumulative deformation will gradually transfer more force to the inverted arch, leading to the bottom heave phenomenon. Stress redistribution and long-term creep deformation will intensify the mechanical action between the surrounding rock and the inverted arch, causing the deformation of the inverted arch bottom to gradually accumulate, and eventually leading to the bottom heave.

[0082] 3. Insufficient or failed tunnel support: if the support system is not reasonably designed or has insufficient strength, it cannot effectively resist the high stress of the surrounding rock, which is easy to cause the bottom heave of the inverted arch.

[0083] 4. Insufficient stiffness of inverted arch structure: If the stiffness of the inverted arch structure is not designed enough, it cannot bear the load transmitted to the bottom of the tunnel, and uneven stress distribution will cause the floor heave, especially the deformation may continue to increase under the condition of creep.

[0084] 5. Construction technology and quality: Unreasonable construction technology will cause disturbance of surrounding rock, increase the stress complexity of inverted arch, and then may cause floor heave. Improper arrangement of energy release device (such as unreasonable design of spacing or depth) will affect its adjustment effect, so that the inverted arch cannot effectively relieve the stress of surrounding rock, increasing the risk of floor heave.

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

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

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

[0088] Determination of the position of the creep deformation energy release hole: according to the stress distribution results, the area with high stress concentration and large deformation is determined as the position of the creep deformation energy release hole, and the stress concentration area at the bottom of the inverted arch is preferentially selected for drilling;

[0089] Determination of the spacing W of the creep deformation energy release hole: according to the numerical simulation results, the effect of different spacings on stress release and deformation control is analyzed, and the spacing of the creep deformation energy release hole is optimized to achieve the best stress release effect while controlling the deformation within the allowable range;

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

[0091] Determination of the diameter D of the creep deformation energy release hole: according to the size of the filling material and the pipe, the diameter of the creep deformation energy release hole is determined to ensure that the diameter of the creep deformation energy release hole can accommodate the filling material and the pipe, and at the same time has construction operability.

[0092] In order to facilitate the understanding of the arrangement of the energy release hole, the arrangement of the energy release hole is marked in Figure 6 the energy release hole spacing 10, the energy release hole depth 9 and the energy release hole diameter 11, and the energy release hole 4 is opened in the surrounding rock 8 below the lining 1.

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

[0094] The final drilling diameter needs to meet the following conditions: ① it can accommodate the filled energy release material (including plastic pipe); ② it provides enough space for material compression to achieve the expected energy release effect. Because the selection of the diameter is not completely dependent on the compression performance of the energy release material, the diameter range determined by the preliminary simulation is verified and fine-tuned in combination with the compression requirements of the energy release material.

[0095] Determining the optimal energy release hole arrangement based on the invert deformation includes:

[0096] Selecting the invert deformation that is less than the design allowed bottom heave deformation, when the number of selected invert deformations is 1, the corresponding energy release hole arrangement is taken as the optimal energy release hole arrangement;

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

[0098] The multiple evaluation indexes include stress uniformity, structural stability, construction feasibility, material economy, long-term creep effect, and environmental and maintenance impact. According to these evaluation indexes, different energy release hole arrangements are quantitatively evaluated by multi-objective optimization method or weight analysis, and after determining the weight of each index, 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 by different creep deformation energy release hole arrangements on the invert bottom, compares it with the ultimate bearing capacity of the invert, and measures the invert deformation at the bottom of the tunnel under the condition of 100-year creep and the design allowed bottom heave deformation, to ensure that the bearing capacity and deformation of the invert are within the allowed range.

[0100] In step S4, the stress at different positions around the energy release hole is calculated using the energy release hole peripheral stress calculation method, and the minimum value of all stresses is selected as the upper limit of the strength of the creep energy release material filled in the energy release hole.

[0101] The creep energy release material is preferably EPP concrete, and the material performance and strength of the EPP concrete are measured through a side limit compression test, and the side limit compression stress-strain curve can be referred to Figure 3 .

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

[0103] S41, according to the friction angle of the surrounding rock at the tunnel, the inner and outer radii of the lining of the tunnel and the invert support resistance, the plastic zone radius of the surrounding rock at the tunnel is calculated:

[0104]

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

[0106] S42, within the plastic zone range, the radial stress F r and the vertical stress F v of the surrounding rock at the periphery of the energy release hole at different depths are calculated:

[0107]

[0108] Wherein, r is the radial distance from the center of the tunnel at different depths;

[0109] S43, within the elastic zone range where the energy release hole is located, the radial stress F r and the vertical stress F v of the surrounding rock at the periphery of the energy release hole at different depths are calculated:

[0110]

[0111] Wherein, r c is the maximum value of the radial distance from the center of the tunnel at the bottom of all energy release holes; σ R is the radial stress when the creep deformation energy release hole depth is R from the center of the tunnel;

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

[0113] S45, the radial stress F r (z) and the vertical stress Fv The minimum value in (z) as the upper limit of the strength of the creep energy-releasing material r and the vertical stress F v corresponding characteristic stress;

[0114] S46, selecting the minimum value of all characteristic stresses as the upper limit of the strength of the creep energy-releasing material filling the energy-releasing hole.

[0115] In the process of determining the upper limit of the strength of the creep energy-releasing material, the analysis of the elastic-plastic range of the creep deformation energy-releasing hole at different depths and the stress state of the unit body can refer to Figure 2 .

[0116] The scheme adopts the above-mentioned way to select a creep energy-releasing material that meets the strength requirement and has compression performance, ensures that the strength of the selected material is less than the minimum value of the circumferential stress at the filling position, so as to realize the cooperative deformation with the surrounding rock, and tests the selected creep energy-releasing material to verify the strength, energy absorption and compression performance of the material, and test the stability and durability of the material under long-term creep conditions.

[0117] In implementation, the expression of the invert support resistance is preferably

[0118]

[0119] Wherein, μ and E are the Poisson's ratio and the elastic modulus of the 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, the creep energy-releasing material is selected according to the upper limit of the strength, and is introduced into the three-dimensional numerical model to verify whether the optimal energy-releasing hole arrangement meets the bottom heave control effect, if yes, step S7 is entered, otherwise, step S6 is entered;

[0121] The determination method of whether the bottom heave control effect is met can be that the upward heave deformation amount of the tunnel bottom invert under the condition of 100 years is simulated and predicted, and the upward heave deformation amount is compared with the design allowable bottom heave deformation amount, if the upward heave deformation amount is less than the design allowable bottom heave deformation amount, it is considered that the bottom heave control effect is met, otherwise, it is considered that the bottom heave control effect is not met.

[0122] In step S6, the energy-releasing hole arrangement is adjusted until the bottom heave control effect is met, the energy-releasing hole arrangement that meets the bottom heave control effect is taken as the final optimal energy-releasing hole arrangement, and then step S7 is entered;

[0123] In step S7, the energy-releasing hole is arranged according to the optimal energy-releasing hole arrangement in the section where the bottom heave may occur, and the plastic tube filled with the selected creep energy-releasing material is placed in the energy-releasing hole.

[0124] According to the optimal energy release hole arrangement mode and construction conditions determined by numerical simulation calculation, in the supporting stage, a drill is used to drill a hole vertically downward at the corresponding position of the tunnel bottom plate, the hole depth is reviewed after the drilling is completed, and the hole is cleaned with high-pressure air; then the plastic pipe is installed.

[0125] The plastic pipe is used to contain compressible material 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 plastic pipe has an outer diameter and thickness determined according to the diameter of the creep deformation energy release hole 11, so that it can be smoothly placed in the creep deformation energy release hole and can be in close contact with the hole.

[0126] The creep energy release material is filled in the plastic pipe to form a creep energy release structure 5 under high ground stress, and the filling process ensures uniform distribution of the buffer compression material, no gap and movement. The pipe is arranged and placed 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 energy release hole wall and prevents movement, which can be used for stress release and floor heave suppression.

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

[0128] The deformation amount of the selected creep energy release material is calculated:

[0129] U c = d·ε m

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

[0131] The deformation amount 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 selected to be smaller than the lower limit.

[0132] Since the diameter of the energy release hole is selected within a predetermined range, which is generally determined by experience, the diameter of the energy release hole obtained is not very accurate. The present scheme determines the diameter of the energy release hole by the above-mentioned manner, and comprehensively considers the strength of the selected creep energy release material, so that the energy release hole obtained is more suitable for specific engineering to adapt to floor heave control.

[0133] In order to facilitate the stability of the creep energy release material filled in the plastic pipe in the energy release hole, the present scheme preferably further includes, when the plastic pipe is installed in step S7:

[0134] Before installing the ductile pipe, clean the energy release hole and set waterproof cementable material with a first thickness at the bottom of the energy release hole; after installing the ductile pipe, set the plugging concrete with a second thickness at the top of the energy release hole.

[0135] The waterproof cementable material fills the bottom stress and prevents water from penetrating, and before injecting the material, the soil and gravel at the bottom of the drilling hole should be cleaned to ensure that the sealing material can be in close contact with the bottom rock-soil. In the preferred embodiment, the plugging concrete is geopolymer concrete.

[0136] In the implementation, the preferred method for determining the first thickness includes:

[0137] Calculate the compressive strength range of the waterproof cementable material when it is not crushed:

[0138] σ m ≥γ.F min

[0139] wherein σ m is the compressive strength of the material; γ is the material strength design coefficient of the waterproof cementable material, and the value is 1.2-1.5; F min is the upper limit value of the strength of the creep energy release material;

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

[0141]

[0142] wherein h b is the first thickness; F max is the stress that the waterproof cementable material needs to bear;

[0143] According to the lower limit value of the first thickness, select the first thickness of the waterproof cementable material filling, specifically, as long as the selected first thickness satisfies the condition of being less than or equal to the lower limit value of the first thickness.

[0144] In the implementation, the preferred method for determining the second thickness includes:

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

[0146] F b =k·δ

[0147] wherein F b is the foundation reaction; k is the foundation reaction coefficient; δ is the vertical deformation at the bottom of the tunnel;

[0148] According to the train load and the foundation reaction, calculate the strength range of the plugging concrete:

[0149] σ c≥ λ · max(Q, F b )

[0150] wherein σ c is the strength of the sealing concrete; λ is a design coefficient of the strength of the sealing concrete, and is taken as 1.2-1.5; Q is the train load; max is taken as the maximum value;

[0151] According to the strength of the sealing concrete, a lower limit value of the second thickness of the sealing concrete filling is determined:

[0152]

[0153] wherein 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 the lower limit value of the second thickness, it is acceptable.

[0155] In Figure 4 and Figure 6 , the present scheme shows a perspective view and a sectional view of the arrangement of the creep bottom heave control system of the inverted arch of the high ground stress gently inclined soft rock traffic tunnel at the bottom of the lining 1 of the tunnel, as shown in Figures 4-6 , the present scheme also provides a system applied to a creep bottom heave control method of the inverted arch of the high ground stress gently inclined soft rock traffic tunnel, which comprises a plurality of energy release holes 4 opened in the surrounding rock 8 of the section of the tunnel where the bottom heave is likely to occur according to the optimal energy release hole arrangement mode and a plastic pipe 6 placed in the energy release hole 4, and the creep energy release material 7 filled into the plastic pipe 6 constitutes a creep energy release structure 5; the plastic pipe 6 is filled with a creep energy release material with a strength less than the upper limit value of the strength of the creep energy release material.

[0156] As shown in Figure 5 , the plastic pipe 5 needs to be segmented and assembled according to the required number of segments determined by the depth H of the energy release hole at the tunnel construction site, and then placed into the energy release hole 4, and the plastic pipe 6 is ensured to be in close contact with the wall of the energy release hole 4 to prevent movement. During the construction process of the energy release hole 4, the generation of water in the hole should be prevented, the plastic pipe 6 should have the characteristics of being compressed and deformed without being damaged to prevent water, and at the same time, the materials used should not pollute the surrounding rock environment.

[0157] In implementation, the energy release hole below the plastic pipe 6 of the present scheme is filled with a waterproof cementable material 3, which is pumped into the energy release hole 4 in a pumping manner to close the bottom of the energy release hole 4; after the installation of the plastic pipe 6 is completed, considering the ground reaction force and the upper train load, high-strength sealing concrete 2 is used to close 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 sealing material: through geological exploration and numerical simulation, combined with theoretical analysis, the stress distribution and deformation of the bottom sealing material under the maximum ground stress are calculated; a material with high compressive strength, certain ductility and deformation capacity is selected to ensure that no damage or plastic deformation occurs under the maximum ground stress.

[0159] In summary, the scheme can effectively prevent and control the floor heaving problem of high ground stress and gently inclined soft rock traffic tunnel. It also has significant applicability and effect on the floor heaving deformation caused by surrounding rock creep, avoids the damage of inverted arch structure, and reduces the cost of tunnel maintenance in later period.

Claims

1. A method for controlling the creep floor heave of an inverted arch in a high ground stress, gently inclined soft rock traffic tunnel, characterized in that, The method comprises the steps of: S1, collecting the geological conditions and stress state of the invert bottom of the tunnel to determine the section where the tunnel is likely to have a floor heave; S2, constructing a three-dimensional numerical model of the tunnel with different arrangement forms of creep deformation energy release holes in the section where the tunnel is likely to have a floor heave according to the rock mass mechanical parameters of the tunnel, the tunnel geometry and the support parameters; S3, simulating and predicting the upward deformation of the invert bottom of the tunnel under high ground stress conditions for 100 years using the three-dimensional numerical model, and determining the optimal energy release hole arrangement based on the upward deformation; S4, calculating the stress at different positions around the energy release hole using the energy release hole surrounding stress calculation method, and selecting the minimum value of all stresses as the upper limit of the strength of the creep energy release material filled in the energy release hole; S5, selecting the creep energy release material according to the upper limit of the strength, introducing it into the three-dimensional numerical model to verify whether the optimal energy release hole arrangement achieves the floor heave control effect, if yes, entering step S7, otherwise entering step S6; S6, adjusting the energy release hole arrangement until the floor heave control effect is met, taking the energy release hole arrangement that meets the floor heave control effect as the final optimal energy release hole arrangement, and then entering step S7; S7, setting the energy release hole according to the optimal energy release hole arrangement in the section where the floor heave is likely to occur, and placing the plastic pipe filled with the selected creep energy release material in the energy release hole; Between step S5 and step S6, the diameter of the energy release hole is also optimized: Calculate the deformation of the selected creep energy release material: wherein 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; Use the deformation of the creep energy release material as the lower limit of the diameter of the energy release hole, and select the diameter of the energy release hole according to the lower limit; When installing the plastic pipe in step S7, it also includes: Before installing the plastic pipe, clean the energy release hole and set a first thickness of waterproof cementable material at the bottom of the energy release hole; after installing the plastic pipe, set a second thickness of sealing concrete at the top of the energy release hole; The determination method of the first thickness includes: Calculate the material compressive strength range when the waterproof cementable material is not crushed: Wherein, sigma m is the compressive strength of the material; gamma is the material strength design coefficient of the waterproof cementable material, and is 1.2-1.5, F min is the upper limit value of the strength of the creep energy release material; Determine the lower limit value of the first thickness of the waterproof cementable material filling according to the material compressive strength range: wherein h b is a first thickness; F max is the stress to be carried by the waterproof cementable material; Select the first thickness of the waterproof cementable material filling according to the lower limit value of the first thickness; The determination method of the second thickness includes: Calculate the ground reaction force at the tunnel according to the foundation conditions at the tunnel bottom: where F b is the ground reaction force; k is the ground reaction coefficient; and δ is the vertical deformation of the tunnel bottom. Calculate the strength range of the sealing concrete according to the train load and the ground reaction force: Wherein, σ c is the strength of the sealing concrete; λ is the strength design coefficient of the sealing concrete, and the value is 1.2-1.5; is the train load; max is the maximum value; Determine the lower limit value of the second thickness of the sealing concrete filling according to the strength of the sealing concrete: wherein h t is a second thickness; Select the second thickness of the sealing concrete filling according to the lower limit value of the second thickness.

2. The high ground stress gently inclined soft rock traffic tunnel inverted arch creep floor heave control method according to claim 1, characterized in that, The step S4 further includes: S41, calculate the plastic zone radius of the surrounding rock at the tunnel according to the friction angle of the surrounding rock at the tunnel, the inner and outer radii of the tunnel lining and the invert support resistance: where R is the plastic zone radius; r2 is the lining outer radius; c is the surrounding rock cohesion; σ Z is the tangential stress when the energy release hole depth is R from the tunnel center; P is the invert support resistance; is the friction angle of the surrounding rock; S42、In the plastic zone range, the radial stress F of the surrounding rock around the energy release hole at different depths is calculated r With the vertical stress F v : Wherein, r is the radial distance at different depths from the center of the tunnel; S43、In the elastic zone where the energy release hole is located, the radial stress F of the surrounding rock at different depths around the energy release hole is calculated r With the vertical stress F v : where r c is the maximum value of the radial distance from the tunnel center of the bottom of all energy release holes; σ R is the radial stress at the depth of the creep deformation energy release hole at a distance R from the tunnel center; S44, according to the geological parameters of the surrounding rock, the creep characteristics and the tunnel support form, the finite element simulation software is used to draw the distribution curve of each group of radial stress F r and vertical stress F v , and the radial stress F r (z) and the vertical stress F v (z) in the z-axis direction are determined according to the distribution curve. S45, selecting the radial stress F in the z-axis direction of each group r (z) and the minimum value in the vertical stress F v (z) as the radial stress F of each group r and the minimum value in the vertical stress F v corresponding characteristic stress; S46, select the minimum value of all characteristic stresses as the upper limit of the strength of the creep energy release material filled in the energy release hole.

3. The method according to claim 2, wherein, The expression of the invert support resistance is: ， wherein, and E are the Poisson's ratio and the elastic modulus of the surrounding rock, respectively; , and are the stiffness coefficient, the Poisson's ratio and the elastic modulus of the inverted arch support structure, respectively; and r1 is the inner radius of the lining.

4. The method for controlling the creep floor heave of the inverted arch of the high ground stress gently inclined soft rock traffic tunnel according to claim 1, characterized in that, The energy release hole arrangement includes the installation position of the energy release hole, the spacing of adjacent energy release holes, the depth of the energy release hole and the diameter of the energy release hole; Determining the optimal energy release hole arrangement based on the upward deformation includes: An upper arch deformation amount less than a design allowed bottom heave deformation amount is selected, and when the selected upper arch deformation amount is 1, a corresponding energy releasing hole arrangement mode is taken as an optimal energy releasing hole arrangement mode; When the selected upper arch deformation amount is greater than or equal to 2, a plurality of evaluation indexes are used to evaluate the energy releasing hole arrangement mode corresponding to the upper arch deformation amount, and an energy releasing hole arrangement mode with the highest evaluation score is selected as the optimal energy releasing hole arrangement mode.

5. A system applied to the method for controlling the creep floor heave of the inverted arch of the high-stress gently-inclined soft rock traffic tunnel according to any one of claims 1-4, characterized in that, The tunnel structure includes a plurality of energy releasing holes opened in a section of the tunnel where bottom heave is likely to occur according to the optimal energy releasing hole arrangement mode and a plasticity pipe placed in the energy releasing holes; the plasticity pipe is filled with a creep energy releasing material with a strength less than an upper limit value of a strength of the creep energy releasing material.

6. The system of claim 5, wherein, The energy releasing hole below the plasticity pipe is filled with a waterproof cementable material, and the energy releasing hole above the plasticity pipe is filled with a plugging concrete.

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