Curtain grouting reinforcement method for tunnel group in deep backfill area, and reinforcement effect assessment method

Abstract

A curtain grouting reinforcement method for a tunnel group in a deep backfill area, and a reinforcement effect assessment method. The reinforcement method comprises the following steps: S1, calibrating hole positions according to design; S2, mounting a drilling rig; S3, drilling holes; S4, burying orifice pipes; S5, performing grouting; S6, sealing the holes; and S7, performing the next drilling and grouting cycle. Investment saving and safe and efficient construction are achieved, tunnel surrounding rocks can be fully reinforced, engineering geological conditions are improved, tunnel cavern stability is good, and ground surface settlement is small. The reinforcement effect assessment method comprises an inspection-hole drilling method, multi-wave and multi-component engineering seismograph inspection, assessment based on a high-definition drilling video, assessment based on soil and stone mixture parameter changes before and after grouting, etc., such that multi-angle comprehensive analysis can be achieved, grouting reinforcement effect assessment is more accurate, and a curtain grouting effect assessment system is further improved, thereby providing research ideas for inspecting and assessing the grouting effect in soil-rock mixed backfill areas.

Description

A tunnel group curtain grouting reinforcement method and effect evaluation method in deep backfill area

[0001] Cross-reference

[0002] The present application claims priority to the Chinese application No. 2024106025947 filed on May 15, 2024, the contents of which are incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The present application belongs to the technical field of tunnel construction, and particularly relates to a tunnel group curtain grouting reinforcement method and effect evaluation method in deep backfill area. BACKGROUND

[0004] In the process of tunnel construction, it is very common to encounter complex engineering geological environment, such as soft surrounding rock, fault fracture zone, water and mud inrush, etc. These engineering problems may cause safety hazards to tunnel construction, and easily cause tunnel collapse, roof fall, etc. For these engineering problems, reinforcement measures are often taken for tunnel surrounding rock, such as advanced pipe shed grouting, advanced small pipe grouting, advanced curtain grouting, etc.

[0005] Many scholars have studied the technical parameters, construction technology and effect analysis of curtain grouting technology, and proposed that the effect of grouting reinforcement mainly manifests in: ① improving the strength and stiffness of surrounding rock, and also improving the cohesion and internal friction angle of surrounding rock, effectively reducing the relative sliding of internal block stones of surrounding rock, ② jointly acting with lining to reduce the load borne by lining structure, ③ improving the engineering geological environment.

[0006] However, the existing backfill stratum grouting reinforcement method cannot fully reinforce the tunnel surrounding rock to improve the engineering geological conditions, the tunnel chamber stability is poor, the ground surface settlement is large, and it is difficult to accurately evaluate and analyze the effect of grouting reinforcement.

[0007] SUMMARY

[0008] Therefore, the purpose of the present application is to provide a tunnel group curtain grouting reinforcement method and effect evaluation method in deep backfill area, which aims to solve the problem that the existing method cannot fully reinforce the tunnel surrounding rock to improve the engineering geological conditions, the tunnel chamber stability is poor, the ground surface settlement is large, and it is difficult to accurately evaluate the effect of grouting reinforcement.

[0009] The present application solves the above technical problems through the following technical means:

[0010] A tunnel group curtain grouting reinforcement method in deep backfill area, comprising the following steps:

[0011] S1. Marking the hole position according to the design;

[0012] According to the hole position and drilling parameters of the design drawing, find the drilling position on the working face, and mark it with paint;

[0013] S2. Drilling rig installation;

[0014] The multifunctional hydraulic walking down-the-hole drill rig is selected to drill a hole, the inclination and horizontal angle of the drill rod are adjusted, the drilling rig is moved, and the drill bit is directed to the hole position calibrated in step S1; a prism is installed at the tail end of the drill rod to enable the total station to check the posture of the drill rod and to enable adjustment; meanwhile, a compass is used to check the posture of the drill rod according to the calculated azimuth and inclination, to ensure drilling accuracy;

[0015] S3. Drilling;

[0016] The multifunctional hydraulic walking down-the-hole drill rig is used to drill a hole, and high-pressure air is used to blow the hole clean after the hole is formed;

[0017] S4. Embedding a hole pipe;

[0018] The hole pipe is embedded in the stoped wall, the hole pipe is exposed by 200-300 mm, the hole pipe is first filled with cement slurry with a water-cement ratio of 0.5:1 for fixation, then filled with resin anchoring agent and hemp to prevent slurry leakage, and after solidification, a gate valve is installed;

[0019] S5. Grouting;

[0020] S6. Hole sealing;

[0021] S7. Next drilling and grouting cycle.

[0022] Further, in the step S3, the drilling parameters and rules are as follows:

[0023] The drilling spacing is 1.95-2.45 m; the drilling diameter is 90-110 mm; the allowable deviation of the drilling hole position from the design position is ±5 cm; the drilling hole bottom position deviation is less than 30 cm; and the drilling sequence is from outside to inside.

[0024] Further, in the step S5, ordinary cement slurry or double-liquid slurry is used for grouting, and double-liquid slurry is used for the outer periphery 1 m within the grouting reinforcement ring; wherein the water-cement ratio of the ordinary cement slurry is 1:1; and the mixing ratio of the double-liquid slurry is water:cement:water glass=1:1:0.665.

[0025] Further, in the step S5, the calculation expression of the slurry injection amount per hole is:

[0026] Q=π·R 2 ·l·n·α·(1+β)

[0027] In the formula, Q represents the slurry injection amount m 3 ; R represents the effective diffusion radius of the slurry m; l represents the grouting section length m; n represents the porosity of the surrounding rock; α represents the slurry filling coefficient; and β represents the loss rate.

[0028] Further, the step S6 grouting parameters are as follows:

[0029] The slurry diffusion radius is 1-1.5 m; the normal grouting pressure is 0.5-1.2 MPa; the final grouting pressure is not less than 1.5 MPa, which is adjusted according to the stratum condition.

[0030] Further, in the step S5, the deep backfill area grouting reinforcement adopts the full-face curtain grouting hole distribution form, which is divided into 5 rings, the first ring has 27 holes, the second ring has 27 holes, the third ring has 24 holes, the fourth ring has 11 holes, and the fifth ring has 5 holes, 3 exploratory holes and 4 inspection holes, wherein the effective diffusion radius of a single hole in the first, second and third rings is 1 m, and the effective diffusion radius of a single hole in the fourth and fifth rings is 1.5 m.

[0031] Further, in the step S5, the grouting is divided into advancing grouting, retreating grouting and one-time full-hole grouting, which is adjusted according to the stratum condition.

[0032] Further, in the step S7, the borehole grouting reinforcement range is within 3 m of the tunnel excavation contour, and the grouting is 20 m in the tunnel excavation direction per cycle, and 5 m is left after the completion of a grouting section as the lap joint and grouting rock disc of the next cycle.

[0033] The application also provides a deep backfill area tunnel group curtain grouting reinforcement effect evaluation method, which comprises the following steps:

[0034] I. The drilling inspection hole method is used to verify the grouting effect;

[0035] II. The multi-wave multi-component engineering seismograph is used to detect the grouting effect;

[0036] III. The drilling high-definition video is used to evaluate the grouting effect;

[0037] The pipe high-definition video detector is used to take pictures around the drilling hole of the tunnel face after curtain grouting, to test the actual curtain grouting effect of the surrounding rock in front of the backfill area face, and to check the adhesion of the slurry and the backfill soil around the drilling hole;

[0038] IV. The grouting reinforcement effect is evaluated based on the parameter change of the soil and rock mixture before and after grouting;

[0039] The physical and mechanical performance indexes of the soil and rock mixture before and after grouting are measured through indoor uniaxial compression and triaxial experiments, and the actual effect of the deep backfill area tunnel group curtain grouting is analyzed and compared;

[0040] V. The grouting reinforcement effect is tested and evaluated through comprehensive analysis.

[0041] Furthermore, in the aforementioned inspection hole method, the number of inspection holes is 3% to 5% of the total number of holes, and ≥ 5 holes, of which 2 holes are located within the excavation area and 3 holes are located outside the excavation area. The inspection holes are 18m long, and core samples are taken from each hole to verify the water outflow of a single hole, the fullness of the rock mass grouting, and to observe the grout filling situation. If there is no mud or sand inflow in the inspection hole, no hole collapse, and the physical and mechanical properties of the soil are significantly improved, and the seepage rate is less than 0.2L / min.m, subsequent construction can proceed; otherwise, supplementary grouting is carried out. Beneficial effects:

[0042] 1. This invention provides a method for curtain grouting reinforcement of tunnel groups in deep backfill areas. Compared with the previous scheme of external reinforcement of the surrounding environment, the construction method of full-section curtain grouting reinforcement inside the tunnel achieves cost savings, safe and efficient construction, and can fully reinforce the surrounding rock of the tunnel, improve engineering geological conditions, and result in good tunnel stability and small surface settlement.

[0043] 2. This invention also provides a method for evaluating the effect of curtain grouting reinforcement in tunnel groups in deep backfill areas, including borehole inspection method, multi-wave multi-component engineering seismograph detection, high-definition video evaluation of boreholes, and evaluation based on changes in parameters of soil-rock mixture before and after grouting. It can conduct comprehensive analysis from multiple perspectives, making the evaluation of grouting reinforcement effect more accurate, further improving the evaluation system of curtain grouting effect, and providing research ideas for the inspection and evaluation of grouting effect in soil-rock mixture backfill areas.

[0044] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0045] Figure 1 is a flowchart of a curtain grouting reinforcement method for tunnel groups in deep backfill soil areas according to the present invention.

[0046] Figure 2 shows the front view of the borehole in the curtain grouting reinforcement design scheme.

[0047] Figure 3 shows the borehole cross-section of the curtain grouting reinforcement design scheme.

[0048] Figure 4 shows the inspection diagram for verification using the drilling inspection hole method;

[0049] Figure 5 shows an image of the tunnel face before grouting in a multi-wave, multi-component engineering seismic exploration tunnel.

[0050] Figure 6 shows an image of the tunnel face after grouting in multi-wave, multi-component engineering seismic detection.

[0051] Figure 7 shows the video detection results. DETAILED DESCRIPTION

[0052] The advantages and effects of the present application can be understood by those skilled in the art from the disclosure of the specification. It should be noted that the drawings provided in the following examples are only for illustrative purposes, and the representations are only schematic diagrams, not physical drawings, and should not be construed as limiting the present application. In order to better illustrate the embodiments of the present application, some components in the drawings may be omitted, enlarged or reduced, and do not represent the actual size of the product; it can be understood by those skilled in the art that some well-known structures and their descriptions in the drawings may be omitted.

[0053] The same or similar reference numerals in the drawings of the embodiments of the present application correspond to the same or similar components, and in the description of the present application, it should be understood that the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "back" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the terms used to describe the positional relationship in the drawings are only for illustrative purposes, and should not be construed as limiting the present application. For those skilled in the art, the specific meanings of the above terms can be understood according to the specific circumstances.

[0054] The curtain grouting fills the gap between the surrounding rock with slurry, and forms a grouting body by mutual adhesion between the particles. The grouting effect increases the cohesion c and internal friction angle φ of the soil-rock mixture, thereby increasing the bonding strength and density of the stratum, and reinforcing the surrounding rock of the tunnel. Moreover, after the slurry fills the gap between the soil-rock mixture, a water barrier is formed, reducing the water permeability of the soil layer.

[0055] As shown in FIGS. 1, 2 and 3, the present application provides a curtain grouting reinforcement method for a tunnel group in a deep backfill area, comprising the following steps:

[0056] S1. Designated hole position;

[0057] According to the hole position and drilling parameters on the design drawing, find the drilling position on the working face and mark it with paint;

[0058] S2. Drilling machine installation;

[0059] Select a multifunctional hydraulic walking down-the-hole drill rig to drill, adjust the inclination and horizontal angles of the drill rod, and move the drilling machine so that the drill bit is directly opposite the hole position marked in step S1. A prism is installed at the tail end of the drilling machine to allow the total station instrument to check the posture of the drill rod and make adjustments. At the same time, a compass is used to check the state of the drill rod according to the calculated azimuth and inclination, to ensure accurate drilling;

[0060] S3. Drilling;

[0061] The multi-functional hydraulic walking down-the-hole drill rig is used to drill the holes, and high pressure air is used to clean the holes after the holes are formed.

[0062] The drilling spacing is 1.95-2.45 m, the drilling diameter is 90-110 mm, the allowable deviation of the drilling hole position from the design position is ±5 cm, the deflection angle should meet the design requirements, one section is checked after drilling one section, the deviation of the drilling hole bottom position is less than 30 cm, the drilling sequence is from outside to inside, the holes in the same circle are drilled at intervals, and the conditions in the holes, such as falling, collapse, plugging, drilling speed, etc. are recorded in detail during drilling, especially the water inflow needs to be accurately recorded.

[0063] The drilling holes are drilled in the sequence of the outer circle first and then the inner circle. The drilling holes in the inner circle can refer to the sequence of the drilling holes in the outer circle, and the grouting effect of the previous holes can be checked for the subsequent holes. The grouting is gradually increased, on the one hand, the grouting parameters can be adjusted according to the drilling conditions, on the other hand, if the drilling conditions prove that the grouting effect has reached the design requirements, the drilling of the next circle of holes can be carried out, reducing the drilling workload and speeding up the construction progress. During drilling, drilling records, including hole number, footage, start and end time, rock fissure development, water gushing position, water inflow and water inflow pressure, etc. should be strictly recorded.

[0064] S4. Burying the hole pipe;

[0065] A φ108 mm, 5 mm thick hot-rolled seamless steel pipe is buried in the grouting wall as a hole pipe, the grouting pipe is exposed by 200-300 mm, and the hole pipe is 3 m long. The hole pipe is first filled with early strength cement slurry with a water-cement ratio of 0.5:1 to fix it, and then resin anchoring agent and hemp wire and other bonding materials are filled to prevent grouting leakage. After solidification, a gate valve is installed. The hole pipe is firmly buried and has good grouting stopping measures. After the hole pipe is installed, the water pressure and water inflow are measured, and the records are filled in the table, including hole number, footage, start time, rock fissure development, water gushing position, water inflow and water inflow pressure, etc.

[0066] S5. Grouting;

[0067] The grouting adopts ordinary cement slurry, and double liquid slurry is considered for the outer periphery of 1 m in the grouting reinforcement circle to strengthen the grouting effect and slurry control. The water-cement ratio of the ordinary cement slurry is 1:1, and the cement strength grade is not less than R32.5. The mixing ratio of the double liquid slurry is water:cement:sodium silicate (out-of-factory concentration 42, dilution concentration 30-35) = 1:1:0.665.

[0068] The calculation expression of the slurry single-hole grouting volume is:

[0069] Q = π·R 2 ·l·n·α·(1+β)

[0070] In the formula, Q represents slurry injection volume m3; R represents slurry effective diffusion radius m; l represents grouting section length m; n represents surrounding rock porosity; a represents slurry filling coefficient; and b represents loss rate; and the related parameters are recommended in Table 1.

[0071] Table 1: Recommended selection table of geological parameters and grouting parameters

[0072] The grouting parameters are as follows: the slurry diffusion radius is 1-1.5 m; the normal grouting pressure is 0.5-1.2 MPa; and the grouting final pressure is not less than 1.5 MPa, which is adjusted according to the stratum condition.

[0073] In the embodiment, the deep backfill area grouting reinforcement adopts the full-face curtain grouting hole arrangement form, and is divided into 5 rings, 27 holes in the first ring, 27 holes in the second ring, 24 holes in the third ring, 11 holes in the fourth ring, and 5 holes in the fifth ring, 3 exploration holes and 4 inspection holes, wherein the effective diffusion radius of a single hole in the first, second and third rings is 1 m, and the effective diffusion radius of a single hole in the fourth and fifth rings is 1.5 m.

[0074] The grouting is divided into advancing grouting, retreating grouting and one-time full-hole grouting, which is adjusted according to the stratum condition, and the related grouting parameters are shown in Table 2.

[0075] Table 2: Grouting parameter statistics table

[0076] S6. Hole sealing;

[0077] S7. Next drilling grouting cycle;

[0078] The drilling grouting reinforcement range is within 3 m outside the tunnel excavation contour, and the grouting is 20 m in one cycle along the tunnel excavation direction, and 5 m is left after the completion of one grouting section without excavation, as the lap joint and grouting rock disc of the next cycle.

[0079] To ensure the grouting quality, the drilling grouting reinforcement range is within 3 m outside the tunnel excavation contour, and the grouting is 20 m in one cycle along the tunnel excavation direction, and 5 m is left after the completion of one grouting section without excavation, as the lap joint and grouting rock disc of the next cycle.

[0080] The application also provides a deep backfill area tunnel group curtain grouting reinforcement effect evaluation method, which comprises the following steps:

[0081] I. Drilling inspection hole method is adopted to verify the grouting effect;

[0082] The number of inspection holes is 3% to 5% of the total number of holes, and ≥5 holes, of which 2 holes are located within the excavation range and 3 holes are located outside the excavation range, the inspection hole length is 18m, and all are cored, for checking single-hole water yield, the fullness of rock mass grouting, and observing the grout filling condition; if there is no mud and sand gushing, no hole collapse, and the soil physical and mechanical indexes are obviously improved, and the water seepage is less than 0.2L / min.m, the subsequent construction can be carried out, otherwise supplementary grouting is carried out;

[0083] Fig. 4a is the effect of step distribution holes; Fig. 4b is grouting construction; Fig. 4c is core sampling; and Fig. 4d is grout filling condition. As can be seen from Fig. 4, the cement grout and the backfill soil mass have obvious bonding effect, and the original loose structure is changed into a grouting body with greatly improved mechanical strength. The completeness of the drilled core is also improved. From the grout filling condition, the soil and rock mass around the tunnel face and the grout are bonded to form a new consolidated body, which has obvious self-stability compared with the original loose soil and rock mass, indicating that the curtain grouting achieves the expected effect, and the construction safety is greatly guaranteed.

[0084] II. Using a multi-wave multi-component engineering seismograph to detect grouting effect;

[0085] The multi-wave engineering seismograph is composed of a DGY-1 main machine and an intelligent multi-component seismic detector. The working principle of the reflection wave method is that the intelligent component seismic detector is fixed on the tunnel face, and the tunnel face is hammered by a manual hammer to form longitudinal vibration waves. When the vibration waves meet rock-soil bodies with different wave resistance, reflection waves will be generated at the interface of the rock-soil bodies. If the surrounding rock conditions in front of the tunnel face are good, the vibration wave signal image received by the seismograph will be obviously symmetrical; if there are soft surrounding rocks or broken zones, underground water and other adverse geologies in front of the tunnel face, the waveform signal image of the vibration waves emitted by the instrument and the reflected vibration waves will be obviously asymmetric, and if adverse geological conditions are encountered, the received reflection wave signal will be weak.

[0086] 1-3 high-resolution three-component detectors are arranged on the tunnel face along the horizontal measuring line or at any position, and are hammered in the direction perpendicular to the tunnel face. The signal is received by the multi-wave multi-component detection system host, input into the computer, and the corresponding conclusion is obtained through the analysis and processing of professional software. The test results before and after the curtain grouting of the deep backfill soil on the tunnel face are compared as shown in Figs. 5 and 6.

[0087] As can be seen from FIGS. 5 and 6, the surrounding rock in the backfill area before grouting is relatively broken, and the structural characteristics of the soft stratum are obvious. The detection result image presents obvious asymmetry, and contains underground water in the local part. The performance of the surrounding rock is greatly improved after grouting. The signals emitted and received by the hammering tunnel face vibration wave are relatively complete, and the detection image presents obvious symmetry, which indicates that the grouting process fills the surrounding rock fissures well, and the grout and the soil and rock mixed backfill form a consolidated body with good mechanical properties, and the overall performance of the tunnel surrounding rock is greatly improved.

[0088] III. Evaluation of grouting effect based on high-definition video of drilling;

[0089] For the tunnel face drilling after curtain grouting, a pipe high-definition video detector is used to take pictures around the drilling to test the actual curtain grouting effect of the surrounding rock in front of the backfill area. The instrument is composed of a pipe high-definition video detection host, an LPS display, and an external 360° infinite rotation high-definition camera, and the camera is equipped with an LED lamp. The pipe high-definition camera connected by a telescopic cable is inserted into the tunnel face drilling to check the bonding condition of the grout and the backfill soil around the drilling. The detection result is shown in FIG. 7.

[0090] As can be seen from FIG. 7, the original backfill soil tunnel structure is loose and broken, the soil and rock mixture is unevenly distributed, and the mechanical properties are poor. The soil and rock mixture forms a grouting body through grouting reinforcement, which has self-stability ability. The grout fills the gaps between the soil and rock mixture, so that the original loose backfill soil has the ability to bond into blocks, and the surrounding rock strength is greatly improved, which ensures the construction safety of the deep backfill area of the tunnel group.

[0091] IV. Evaluation of grouting reinforcement effect based on parameter changes of soil and rock mixture before and after grouting;

[0092] The existence of joints, fissures, and fracture zones reduces the integrity, strength, and stiffness of the surrounding rock. Grouting can significantly improve the mechanical properties of the structural plane. The original soil and rock mixture in the backfill area has loose structure, poor uniformity, and prominent anisotropy, and its mechanical indicators are poor and the shear strength is low. After curtain grouting, the physical and mechanical properties are significantly improved. Through the analysis and comparison of the physical and mechanical properties of the soil and rock mixture before and after grouting measured by indoor uniaxial compression and triaxial experiments, the actual effect of curtain grouting in the deep backfill area of the tunnel group is evaluated.

[0093] According to the rock mass design parameter value principle and suggestion in the reference interval survey report, the deformation modulus and elastic modulus standard value of the rock mass are 0.7 times the average value of the rock indoor test, and the Poisson's ratio is the average value of the rock indoor test. The shear strength of the rock mass is reduced from the rock indoor shear strength, the reduction factor of the internal friction angle φ is 0.90, and the reduction factor of the cohesion c is 0.3.

[0094] The core sample used in the indoor test is a core sample with a length greater than 10 cm processed from a relatively complete on-site drilling sample, and the cohesion c and the elastic modulus E are reduced by 0.1 times of the non-uniformity coefficient again according to the drilling sample results of the working face, the grout filling situation of the grouting area with a longitudinal 15 m excavation range and a lateral 3 m outside the excavation contour. The reduced elastic modulus E of the grouting reinforcement area is 280 MPa, the Poisson's ratio is 0.3, the cohesion c is 220 kPa, and the internal friction angle φ is 40°.

[0095] The physical and mechanical parameters of the soil-rock mixture before and after grouting are shown in Table 3:

[0096] Table 3.4 Physical and mechanical parameters of soil-rock mixture before and after grouting

[0097] As can be seen from the table 3 of the physical and mechanical parameters of the soil-rock mixture before and after grouting, the physical and mechanical parameters of the soil-rock mixture after grouting are significantly improved, the cohesion c after grouting is 4 times that before grouting, the internal friction angle φ after grouting is 1.1 times that before grouting, and the elastic modulus E after grouting is 7 times that before grouting. The cohesion c and the elastic modulus E of the grouting reinforcement area after curtain grouting increase significantly.

[0098] V. Comprehensive analysis, test and evaluation of grouting reinforcement effect.

[0099] The present application evaluates the curtain grouting effect in the deep backfill soil area by indoor test, field seismic wave detection and hole video detection, and provides a research idea for the test and evaluation of the grouting effect in the soil-rock mixed backfill soil area.

[0100] The above examples are only used to illustrate the technical solutions of the present application and are not limited. Although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or replaced equivalently without departing from the purpose and scope of the present application, and they should be covered in the scope of the claims of the present application. The technical, shape and structure parts not described in detail in the present application are well-known technologies.

Claims

1. A method for tunnel group curtain grouting reinforcement in a deep backfill area, characterized in that, It comprises the following steps: S1. Marking the hole position according to the design; According to the hole position and drilling parameters in the design drawing, find the drilling position on the working surface and mark it with paint; S2. Installing the drilling machine; Select the multifunctional hydraulic walking down-the-hole drill rig to drill, adjust the inclination and horizontal angles of the drill rod, move the drilling machine so that the drill bit is directly opposite the hole position marked in step S1; the tail end of the drilling machine is provided with a prism so that the total station instrument can check the posture of the drill rod and make adjustment; at the same time, a compass is used to check the state of the drill rod according to the calculated azimuth and inclination to ensure the accuracy of drilling; S3. Drilling; Use the multifunctional hydraulic walking down-the-hole drill rig to drill, and use high-pressure air to clean the hole after the hole is formed; S4. Burying the hole pipe; Bury the hole pipe in the stop-slip wall, with 200-300 mm exposed outside the hole pipe; first fill the hole pipe with cement slurry with a water-cement ratio of 0.5:1 for fixation, then fill it with resin anchoring agent and hemp to prevent slurry leakage, and after solidification, install a gate valve; S5. Grouting; S6. Sealing the hole; S7. The next drilling and grouting cycle.

2. The method according to claim 1, wherein the method is characterized by: In step S3, the drilling parameters and rules are as follows: The drilling spacing is 1.95-2.45 m; the drilling diameter is 90-110 mm; the allowable deviation of the drilling hole position from the design position is ±5 cm; the drilling hole bottom position deviation is less than 30 cm; and the drilling sequence is from outside to inside.

3. The method according to claim 1, wherein the method is characterized by: In step S5, ordinary cement slurry or double-liquid slurry is used for grouting, and double-liquid slurry is used for the outer periphery 1 m within the grouting reinforcement ring; wherein the water-cement ratio of the ordinary cement slurry is 1:1; and the mixing ratio of the double-liquid slurry is water:cement:sodium silicate=1:1:0.

665.

4. The method according to claim 3, wherein the method is characterized in that: In the step S5, the calculation expression of the slurry single-hole grouting amount is: Q=π·R 2 ·l·n·α·(1+β) In the formula, Q represents the slurry injection amount m 3 ; R represents the effective diffusion radius of the slurry m; l represents the length of the grouting section m; n represents the porosity of the surrounding rock; a represents the slurry filling coefficient; and β represents the loss rate.

5. The method according to claim 4, wherein the method is characterized in that: In step S6, the grouting parameters during the grouting process are as follows: The slurry diffusion radius is 1-1.5 m; the normal grouting pressure is 0.5-1.2 MPa; the final grouting pressure is not less than 1.5 MPa, which is adjusted according to the stratum conditions.

6. The method according to claim 5, wherein the method is characterized by: In step S5, full-face curtain grouting hole distribution is used for grouting reinforcement in the deep backfill area, which is divided into 5 rings, with 27 holes in the first ring, 27 holes in the second ring, 24 holes in the third ring, 11 holes in the fourth ring, and 5 holes in the fifth ring, 3 exploration holes and 4 inspection holes, wherein the effective diffusion radius of a single hole in the first, second and third rings is 1 m, and the effective diffusion radius of a single hole in the fourth and fifth rings is 1.5 m.

7. The method according to claim 1, wherein the method is characterized by: In step S5, grouting is divided into forward grouting, backward grouting and one-time full-hole grouting, which is adjusted according to the stratum conditions.

8. The method according to claim 1, wherein the method is characterized by: In step S7, the drilling and grouting reinforcement range is within 3 m of the tunnel excavation contour, and the grouting is 20 m in the tunnel excavation direction per cycle; after completing a grouting section, 5 m is left without excavation, which is used as the lap joint and stop-slip rock disc for the next cycle.

9. A method for evaluating the reinforcement effect of curtain grouting of a tunnel group in a deep backfill area, characterized in that, It comprises the following steps: I. Drilling inspection hole method is used to verify the grouting effect; II. Multi-wave multi-component engineering seismograph is used to detect the grouting effect; III. High-definition video evaluation based on drilling is used to evaluate the grouting effect; After curtain grouting, the tunnel face is drilled, and a pipe high-definition video detector is used to take pictures around the drilling hole to test the actual curtain grouting effect of the backfill area in front of the face, and to check the adhesion of the slurry and backfill soil around the drilling hole; IV. Evaluation of grouting reinforcement effect based on changes in soil-rock mixture parameters before and after grouting; Through the indoor single-axis compression and triaxial experiment, the physical and mechanical properties of the soil-rock mixture before and after grouting are determined, analyzed and compared to evaluate the actual effect of curtain grouting in the deep backfill soil area tunnel group; V. Comprehensive analysis, test, and evaluation of grouting reinforcement effect.

10. The method for evaluating the reinforcement effect of curtain grouting of a tunnel group in a deep backfill area according to claim 9, characterized in that: In the drill inspection hole method, the number of inspection holes is 3% to 5% of the total number of drill holes, and ≥5 holes, of which 2 holes are located within the excavation range and 3 holes are located outside the excavation range. The inspection hole length is 18m, and all are cored to check the single-hole water yield, the fullness of rock mass grouting, and observe the grout filling condition. If there is no mud and sand gushing, no hole collapse, and the soil physical and mechanical indicators are significantly improved, and the water seepage is less than 0.2L / min.m, the subsequent construction can be carried out, otherwise supplementary grouting is required.

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