A large-section tunnel construction method for crossing a residual slope accumulation area

Abstract

The present invention relates to the technical field of tunnel construction, and provides a large-section tunnel construction method that crosses a residual slope accumulation area. The present application excavates in the order of upper left pilot pit, upper right pilot pit, lower left pilot pit upper step, lower left pilot pit lower step, lower right pilot pit upper step, lower right pilot pit lower step, lower reserved core soil upper step, and lower reserved core soil lower step, to ensure safety during the excavation process, and facilitate the timely construction of support structures. After excavating each pilot pit, the corresponding initial support on the surrounding rock side is promptly applied, which improves the stability of the surrounding rock, prevents the surrounding rock from becoming unstable due to excavation, and effectively controls the deformation of the surrounding rock. In addition to the initial support, a temporary support structure is also applied to ensure safety during the construction process. The tunnel excavation method provided by the present application can effectively solve the problems of easy collapse and water gushing caused by excessive excavation surface height and excessive single excavation area, making the excavation process safe and orderly.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel construction, in particular to a large-section tunnel construction method that passes through a residual slope accumulation area. Background Art

[0002] In recent years, with the increasing scale of highway tunnel construction, more and more problems such as adverse geology and terrain have been encountered during tunnel construction. For example, shallow buried tunnel sections encounter water-rich residual slope accumulation bodies, which poses great engineering safety risks and poses new challenges to safety during construction and operation. The surrounding rock in the residual slope accumulation body section is relatively loose and the geological conditions are complex, making it difficult for the surrounding rock to form an arch. The original equilibrium state of the slope accumulation body is destroyed during the tunnel excavation process. In addition, due to the effect of water, a slight carelessness during construction can easily cause a collapse accident. Therefore, how to ensure the safety of tunnels in residual slope accumulation body sections, especially large-section and small-clearance tunnels in water-rich residual slope accumulation bodies, has become a difficulty that needs to be overcome in design and construction.

[0003] However, there are few studies on tunnels passing through water-rich residual slope accumulation bodies, especially shallow buried small clearance large span tunnels, and there are no examples to refer to. If the traditional single-side wall or double-side wall pilot pit method is used for excavation, when facing water-rich residual slope accumulation bodies, the accumulation bodies are easily softened and deformed when exposed to water, and the self-stability is extremely poor. In addition, due to the effect of water gushing, if the height between the upper and lower steps is too large, the excavated soil cannot be self-stabilized, and landslides and water gushing are very likely to occur.

[0004] In view of this, it is necessary to propose a large-section tunnel construction method that passes through residual slope accumulation areas to solve or at least alleviate the above-mentioned defects. Summary of the invention

[0005] The main purpose of the present invention is to provide a large-section tunnel construction method that passes through a residual slope accumulation area, so as to solve the technical problem in the prior art that if the traditional single-side wall or double-side wall pilot pit method is used for excavation when the tunnel passes under a water-rich residual slope accumulation area, landslides and water gushing are very likely to occur.

[0006] To achieve the above object, the present invention provides a large-section tunnel construction method for passing through a residual slope accumulation area, comprising the following steps:

[0007] S1, grouting reinforcement of the residual slope accumulation stratum in front of the tunnel face;

[0008] S2, excavating the upper left pilot pit of the tunnel, and performing the first surrounding rock side initial support, the first pilot pit side wall temporary support and the first temporary invert corresponding to the upper left pilot pit;

[0009] S3, excavating the upper right pilot pit and constructing the second surrounding rock side initial support and the second temporary invert corresponding to the upper right pilot pit;

[0010] S4, excavating the upper step of the lower left pilot pit below the upper left pilot pit, and performing the initial support of the third surrounding rock side and the temporary support of the second pilot pit side wall corresponding to the upper step of the lower left pilot pit;

[0011] S5, excavating the lower step of the lower left pilot pit below the upper step of the lower left pilot pit, and performing the initial support of the fourth surrounding rock side and the temporary support of the third pilot pit side wall corresponding to the lower step of the lower left pilot pit;

[0012] S6, excavating the upper step of the lower right pilot pit below the upper right pilot pit, and performing the fifth surrounding rock side initial support and the fourth pilot pit side wall temporary support corresponding to the upper step of the lower right pilot pit;

[0013] S7, excavating the lower right pilot pit lower step below the lower right pilot pit upper step, and performing the sixth surrounding rock side initial support and the fifth pilot pit side wall temporary support corresponding to the lower right pilot pit lower step;

[0014] S8, excavating the lower reserved core soil upper step located between the lower left pilot pit upper step and the lower right pilot pit upper step;

[0015] S9, excavating the lower reserved core soil lower step between the lower left pilot pit lower step and the lower right pilot pit lower step, and performing the seventh surrounding rock side initial support corresponding to the lower reserved core soil lower step;

[0016] S10, dismantle the temporary support of the first pilot pit side wall, the first temporary invert, the second temporary invert, the second pilot pit side wall temporary support, the third pilot pit side wall temporary support, the fourth pilot pit side wall temporary support, and the fifth pilot pit side wall temporary support, and then pour the secondary lining.

[0017] Preferably, the tunnel includes a left tunnel line and a right tunnel line, and the step S1 specifically includes the steps of:

[0018] S11, determining the range of the poorly treated section of the residual slope accumulation body in the stratum according to the positions of the left line of the tunnel and the right line of the tunnel, and determining the target grouting range according to the poorly treated section range;

[0019] S12. Construct a curtain grouting structure within the target grouting range. Among them, the curtain grouting structure extends vertically from the ground surface to the intact rock stratum above the tunnel. The curtain grouting structure includes an intermediate curtain grouting structure located between the left tunnel line and the right tunnel line, a first longitudinal curtain grouting structure located outside the left tunnel line, a second longitudinal curtain grouting structure located outside the right tunnel line, and two transverse curtain grouting structures arranged at intervals along the tunnel extension direction. The intermediate curtain grouting structure, the first longitudinal curtain grouting structure, the second longitudinal curtain grouting structure, and the transverse curtain grouting structure form a "day" - shaped structure on the plane;

[0020] S13. Continue to construct a plurality of left - line primary grouting structures arranged at transverse intervals along the left tunnel line and a plurality of right - line primary grouting structures arranged at transverse intervals along the right tunnel line. Among them, the left - line primary grouting structure is located within the "mouth" - shaped area enclosed by the intermediate curtain grouting structure, the first longitudinal curtain grouting structure, and the transverse curtain grouting structure; the right - line primary grouting structure is located within the "mouth" - shaped area enclosed by the intermediate curtain grouting structure, the second longitudinal curtain grouting structure, and the transverse curtain grouting structure; the left - line primary grouting structure extends vertically from the ground surface to the intact rock stratum above the left tunnel line, and the right - line primary grouting structure extends vertically from the ground surface to the intact rock stratum above the right tunnel line;

[0021] S14. Continue to construct a plurality of left - line secondary grouting structures arranged at transverse intervals along the left tunnel line and a plurality of right - line secondary grouting structures arranged at transverse intervals along the right tunnel line. Among them, the left - line secondary grouting structures and the left - line primary grouting structures are arranged alternately, the right - line secondary grouting structures and the right - line primary grouting structures are arranged alternately. The left - line secondary grouting structure extends vertically from the ground surface to the intact rock stratum above the left tunnel line, and the right - line secondary grouting structure extends vertically from the ground surface to the intact rock stratum above the right tunnel line; the curtain grouting structure, the left - line primary grouting structure, the right - line primary grouting structure, the left - line secondary grouting structure, and the right - line secondary grouting structure jointly form a formation grouting body structure;

[0022] S15. Construct an advanced support structure for the vault in front of the tunnel face.

[0023] Preferably, the advanced support structure for the vault includes a first advanced small - diameter pipe, a second advanced small - diameter pipe, a third advanced small - diameter pipe, and a fourth advanced small - diameter pipe. Among them,

[0024] The external insertion angle of the first advanced small - diameter pipe is 10°, the length is 4m, the longitudinal spacing between adjacent two first advanced small - diameter pipes is 2m, the circumferential spacing is 0.4m. The first advanced small - diameter pipes are fan - shaped and spread from the vault to both sides in the circumferential direction, and the angle between the first advanced small - diameter pipe and the radial direction increases by 1°逐根递增1° from the vault to both sides;

[0025] The second leading small duct has an external insertion angle of 20° and a length of 4m. The longitudinal spacing between two adjacent second leading small ducts is 2m, and the ring spacing is 0.4m. The second leading small duct spreads out in a fan shape from the arch to both sides in the ring direction, and the angle between the second leading small duct and the radial direction increases by 1° from the arch to both sides.

[0026] The third leading small duct has an external insertion angle of 30° and a length of 4.5m. The longitudinal spacing between two adjacent third leading small ducts is 2m, and the ring spacing is 0.4m. The third leading small duct spreads out in a fan shape from the arch to both sides in the ring direction, and the angle between the third leading small duct and the radial direction increases by 1° from the arch to both sides.

[0027] The fourth leading small duct has an external insertion angle of 45° and a length of 4.5 m. The longitudinal spacing between two adjacent fourth leading small ducts is 2 m, and the ring spacing is 0.4 m. The fourth leading small duct spreads out in a fan shape from the arch to both sides in the ring direction, and the angle between the fourth leading small duct and the radial direction increases by 1° from the arch to both sides.

[0028] Among them, the first advance small duct, the second advance small duct, the third advance small duct and the fourth advance small duct are staggered in the longitudinal direction and the transverse direction of the tunnel.

[0029] Preferably, cement slurry is used for grouting of the first advance small duct, and cement-water glass double liquid slurry is used for grouting of the second advance small duct, the third advance small duct and the fourth advance small duct.

[0030] Preferably, the high end of the first leading small conduit, the high end of the second leading small conduit, the high end of the third leading small conduit and the high end of the fourth leading small conduit are all embedded in the formation grouting body structure.

[0031] Preferably, the step S2 specifically comprises the steps of:

[0032] S21, excavating the upper left pilot pit in four cycles, first constructing the first advance small guide pipe on the surrounding rock side within the excavation range of the upper left pilot pit, excavating the first cycle of 0.5m, and constructing the corresponding first surrounding rock side initial support, first pilot pit side wall temporary support and first temporary invert;

[0033] S22, construct the second advance small guide pipe, excavate the second cycle 0.5m, and construct the corresponding first surrounding rock side initial support, the first pilot pit side wall temporary support and the first temporary invert;

[0034] S23, construct the third advance small guide pipe, excavate the third cycle 0.5m, and construct the corresponding first surrounding rock side initial support, the first pilot pit side wall temporary support and the first temporary invert;

[0035] S24, construct the fourth advance small guide tube, excavate the fourth cycle of 0.5m, and construct the corresponding first surrounding rock side initial support, the first pilot pit side wall temporary support and the first temporary invert.

[0036] Preferably, the step S3 specifically comprises the steps of:

[0037] S31, after excavating 2 m of the upper left pilot pit, excavating the upper right pilot pit in four cycles, first constructing the first advance small guide pipe on the surrounding rock side within the excavation range of the upper right pilot pit, excavating the first cycle of 0.5 m, and constructing the corresponding second surrounding rock side initial support and second temporary invert;

[0038] S32, construct the second advance small guide tube, excavate the second cycle 0.5m, and construct the corresponding second surrounding rock side initial support and the second temporary invert;

[0039] S33, construct the third advance small guide tube, excavate the third cycle 0.5m, and construct the corresponding second surrounding rock side initial support and second temporary invert;

[0040] S34, construct the fourth advance small duct, excavate the fourth cycle of 0.5m, and construct the corresponding second surrounding rock side initial support and the second temporary invert.

[0041] Preferably, the steps S4 to S7 specifically include the steps of:

[0042] After the upper right pilot pit is excavated for 2m, the upper step of the lower left pilot pit is excavated in four cycles, with the advance of each cycle controlled at 0.5m. After each cycle of excavation is completed, the corresponding initial support of the third surrounding rock side and temporary support of the second pilot pit side wall are implemented;

[0043] After excavating 2m of the upper step of the lower left pilot pit, excavate the lower step of the lower left pilot pit in four cycles, with the advance of each cycle controlled at 0.5m. After each cycle of excavation, implement the corresponding initial support of the fourth surrounding rock side and temporary support of the third pilot pit side wall;

[0044] After excavating 2m of the lower step of the left pilot pit, the upper step of the right pilot pit was excavated in four cycles, with the advance of each cycle controlled at 0.5m. After each cycle of excavation, the corresponding initial support of the fifth surrounding rock side and temporary support of the fourth pilot pit side wall were implemented;

[0045] After excavating 2m of the upper step of the lower right pilot pit, the lower step of the lower right pilot pit was excavated in four cycles. The advance of each cycle was controlled at 0.5m. After each cycle of excavation was completed, the corresponding initial support of the sixth surrounding rock side and temporary support of the fifth pilot pit side wall were implemented.

[0046] Preferably, the steps S8-S9 specifically include the steps of:

[0047] After excavating 2m of the lower step of the right pilot pit, excavate the upper step of the reserved core soil in the lower part in four cycles, with the advance of each cycle controlled at 0.5m;

[0048] After excavating 2m of the upper step of the lower reserved core soil, the lower step of the lower reserved core soil is excavated in four cycles, with the advance of each cycle controlled at 0.5m, and the corresponding initial support of the seventh surrounding rock side is implemented.

[0049] Preferably, the pouring of the secondary lining in step S10 specifically includes the following steps:

[0050] Cast the tunnel invert lining, apply the tunnel composite waterproof layer on the entire section, and cast the secondary lining corresponding to the tunnel arch and tunnel side wall; the secondary lining should be no more than 20m away from the heading face.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] (1) The present application divides a large-section tunnel into multiple small areas on the cross section for excavation, and excavates in the order of upper left pilot pit, upper right pilot pit, lower left pilot pit upper step, lower left pilot pit lower step, lower right pilot pit upper step, lower right pilot pit lower step, lower reserved core soil upper step, and lower reserved core soil lower step. This order can ensure safety during the excavation process and is conducive to the timely construction of support structures. After excavating each pilot pit, the corresponding initial support on the surrounding rock side is timely applied, which improves the stability of the surrounding rock, prevents the surrounding rock from becoming unstable due to excavation, and effectively controls the deformation of the surrounding rock. In addition to the initial support, temporary support structures such as temporary inverts and temporary side wall supports are also applied. The temporary support structures can provide additional support during the excavation process to ensure safety during the construction process. The tunnel excavation method provided by the present application can effectively solve the problems of easy collapse and water gushing caused by excessive excavation surface height and excessive single excavation area, making the excavation process safe and orderly.

[0053] (2) The present application adopts a three-layer grouting structure implementation method, namely, the first layer is a sun-shaped curtain grouting structure, the second layer is a binocular primary grouting structure, and the third layer is a double sun-shaped secondary grouting structure. The reinforcement effect is excellent, and it can significantly improve the self-stabilization time and bearing capacity of the surrounding rock, reduce the possibility of sudden water inrush during tunnel excavation and operation and maintenance, and effectively solve the stability problem of water-rich residual slope accumulation within a certain range on the surface, thereby ensuring the stability of unfavorable geological layers during tunnel excavation.

[0054] (3) Compared with the traditional small advance conduit, the fan-shaped small conduit arrangement adopted in this application can increase the tunnel top grouting filling rate to more than 80%, and the top grouting height can reach more than 4m, which can be fully connected with the surface grouting. In addition, the fan-shaped small conduit can divide the top reinforcement into four layers, and reinforce them step by step, which has better stability, which is also impossible for the traditional small advance conduit. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0056] Figure 1 is a schematic diagram of a flow chart in one embodiment of the present invention;

[0057] Figure 2 This is a flow chart of the specific steps included in step S1 in one embodiment of the present invention;

[0058] Figure 3 It is a schematic diagram of the plan layout of grouting reinforcement of residual slope accumulation body strata in one embodiment of the present invention;

[0059] Figure 4 It is a schematic diagram of the cross-section arrangement of grouting reinforcement of residual slope accumulation body strata in one embodiment of the present invention;

[0060] Figure 5 is a schematic diagram of the cross-sectional arrangement of the advance small catheter in one embodiment of the present invention;

[0061] Figure 6 It is a schematic diagram of the longitudinal section arrangement of the leading small catheter in one embodiment of the present invention;

[0062] Figure 7 Schematic diagram of the planar layout of the advance small catheter in one embodiment of the present invention;

[0063] Figure 8 is a cross-sectional schematic diagram of a construction method in one embodiment of the present invention;

[0064] Fig. 9 It is a schematic plan view of a construction method in one embodiment of the present invention.

[0065] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments.

[0066] Description of Figure Numbers:

[0067] 110, left line of tunnel; 120, right line of tunnel; 210, upper left pilot pit; 211, initial support of first surrounding rock side; 212, temporary support of first pilot pit side wall; 213, first temporary invert; 220, upper right pilot pit; 221, initial support of second surrounding rock side; 222, second temporary invert; 230, upper step of lower left pilot pit; 231, initial support of third surrounding rock side; 232, temporary support of second pilot pit side wall; 240, lower step of lower left pilot pit; 241 , initial support of the fourth surrounding rock side; 242, temporary support of the side wall of the third pilot pit; 250, upper step of the lower right pilot pit; 251, initial support of the fifth surrounding rock side; 252, temporary support of the side wall of the fourth pilot pit; 260, lower step of the lower right pilot pit; 261, initial support of the sixth surrounding rock side; 262, temporary support of the side wall of the fifth pilot pit; 271, upper step of the reserved core soil at the bottom; 272, lower step of the reserved core soil at the bottom; 280, initial support of the seventh surrounding rock side; 290, secondary lining;

[0068] 310. Intermediate curtain grouting structure; 320. First longitudinal curtain grouting structure; 330. Second longitudinal curtain grouting structure; 340. Transverse curtain grouting structure; 350. First grouting hole; 360. Pre-reinforcement area; 370. Grouting steel pipe; 410. Left line primary grouting structure; 420. Right line primary grouting structure; 430. Second grouting hole; 510. Left line secondary grouting structure; 520. Right line secondary grouting structure; 530. Third grouting hole; 610. First advance small conduit; 620. Second advance small conduit; 630. Third advance small conduit; 640. Fourth advance small conduit; 710. Residual slope accumulation body stratum; 720. Complete rock stratum; 80. Steel arch frame. DETAILED DESCRIPTION

[0069] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0070] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0071] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0072] In addition, the descriptions of "right part", "middle part" and the like in the present invention are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "right part" and "middle part" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0073] Please see attached Figures 1 to 9 In one embodiment of the present invention, a large-section tunnel construction method that passes through a residual slope accumulation area includes the following steps:

[0074] S1, grouting reinforcement of the residual slope accumulation stratum 710 in front of the tunnel face;

[0075] S2, excavating the upper left pilot pit 210 of the tunnel, and constructing the first surrounding rock side initial support 211, the first pilot pit side wall temporary support 212 and the first temporary invert 213 corresponding to the upper left pilot pit 210;

[0076] S3, excavating the upper right pilot pit 220 and constructing the second surrounding rock side initial support 221 and the second temporary invert 222 corresponding to the upper right pilot pit 220;

[0077] S4, excavating the lower left pilot pit upper step 230 located below the upper left pilot pit 210, and implementing the third surrounding rock side initial support 231 and the second pilot pit side wall temporary support 232 corresponding to the lower left pilot pit upper step 230;

[0078] S5, excavating the lower left pilot pit lower step 240 located below the lower left pilot pit upper step 230, and constructing the fourth surrounding rock side initial support 241 and the third pilot pit side wall temporary support 242 corresponding to the lower left pilot pit lower step 240;

[0079] S6, excavating the lower right pilot pit upper step 250 located below the upper right pilot pit 220, and performing the fifth surrounding rock side initial support 251 and the fourth pilot pit side wall temporary support 252 corresponding to the lower right pilot pit upper step 250;

[0080] S7, excavating the lower right pilot pit lower step 260 located below the lower right pilot pit upper step 250, and constructing the sixth surrounding rock side initial support 261 and the fifth pilot pit side wall temporary support 262 corresponding to the lower right pilot pit lower step 260;

[0081] S8, excavating the lower reserved core soil upper step 271 between the lower left pilot pit upper step 230 and the lower right pilot pit upper step 250;

[0082] S9, excavating the lower reserved core soil lower step 272 between the lower left pilot pit lower step 240 and the lower right pilot pit lower step 260, and performing the seventh surrounding rock side initial support 280 corresponding to the lower reserved core soil lower step 272;

[0083] S10, remove the first pilot pit side wall temporary support 212, the first temporary invert 213, the second temporary invert 222, the second pilot pit side wall temporary support 232, the third pilot pit side wall temporary support 242, the fourth pilot pit side wall temporary support 252, and the fifth pilot pit side wall temporary support 262, and then cast the secondary lining 290.

[0084] It is worth noting that the large-section tunnel of the present application, such as a three-lane tunnel, has a single-hole excavation span of 19m and a height of 13m. It is also a small-clearance tunnel, with a clear distance between two holes generally less than 10m. When excavating using the traditional single-sidewall or double-sidewall pilot pit method, when facing a water-rich residual slope accumulation body, the accumulation body is easily softened and deformed when it encounters water, and its self-stability is extremely poor. In addition, due to the effect of water gushing, if the height between the upper and lower steps is too large, the excavated soil body cannot be self-stabilized, and landslides and water gushing are very likely to occur.

[0085] In the present application, grouting reinforcement is performed on the residual slope accumulation stratum 710 in front of the tunnel face, which can enhance the stability and bearing capacity of the stratum and reduce the risk of collapse and instability that may occur during excavation. The present application adopts single-double composite side wall step excavation, which can effectively solve the problems of easy collapse and water gushing caused by excessive excavation height of the excavation face and excessive single excavation area. Specifically, the large-section tunnel is divided into multiple small areas on the cross section for excavation, and the upper left pilot pit 210, the upper right pilot pit 220, and the lower right pilot pit 230 are excavated in sequence. The excavation is carried out in the order of the upper step 230 of the lower left pilot pit, the lower step 240 of the lower left pilot pit, the upper step 250 of the lower right pilot pit, the lower step 260 of the lower right pilot pit, the upper step 271 of the lower reserved core soil, and the lower step 272 of the lower reserved core soil. This order can ensure the safety during the excavation process and is conducive to the timely construction of the support structure. After each pilot pit is excavated, the corresponding initial support on the surrounding rock side is timely applied to improve the stability of the surrounding rock, prevent the surrounding rock from losing stability due to excavation, and effectively control the deformation of the surrounding rock. In addition to the initial support, temporary support structures such as temporary inverts and temporary sidewall supports are also applied. The temporary support structures can provide additional support during the excavation process to ensure safety during the construction process. After all pilot pits are excavated, all temporary support structures are removed. Finally, the secondary lining 290 is poured to form the final structure of the tunnel.

[0086] The tunneling method provided by this application can effectively solve the problems of easy collapse and water gushing caused by too high excavation face height and too large single excavation area, making the excavation process safe and orderly.

[0087] Further, after the upper left pilot tunnel 210 is excavated, 2 small pipes with a diameter of φ42×3.5mm can be used for foot locking at each of the two arch feet on both sides, and cement slurry is injected to reduce the settlement of the steel arch 80 and enhance the structural stability; similarly, after the upper right pilot tunnel 220, the upper bench of the lower left pilot tunnel 230, the lower bench of the lower left pilot tunnel 240, the upper bench of the lower right pilot tunnel 250, and the lower bench of the lower right pilot tunnel 260 are correspondingly excavated, 2 small pipes with a diameter of φ42×3.5mm can be used for foot locking at each of the two arch feet in the corresponding pilot tunnel area, and cement slurry is injected to reduce the settlement of the steel arch 80 and enhance the structural stability.

[0088] As a preferred embodiment, the tunnel includes a left tunnel line 110 and a right tunnel line 120, and the step S1 specifically includes the steps:

[0089] S11, determine the range of the poor treatment section where the stratum is residual slope accumulation according to the positions of the left tunnel line 110 and the right tunnel line 120, and determine the target grouting range according to the range of the poor treatment section;

[0090] S12, construct a curtain grouting structure within the target grouting range; wherein, the curtain grouting structure extends vertically from the ground surface to the intact rock stratum 720 located above the tunnel, and the curtain grouting structure includes an intermediate curtain grouting structure 310 located between the left tunnel line 110 and the right tunnel line 120, a first longitudinal curtain grouting structure 320 located outside the left tunnel line 110, a second longitudinal curtain grouting structure 330 located outside the right tunnel line 120, and two transverse curtain grouting structures 340 arranged at intervals along the tunnel extension direction. The intermediate curtain grouting structure 310, the first longitudinal curtain grouting structure 320, the second longitudinal curtain grouting structure 330, and the transverse curtain grouting structure 340 form a Chinese character "ri" structure on the plane;

[0091] S13, continue to construct a plurality of left-line primary grouting structures 410 arranged at intervals along the left line 110 of the tunnel and a plurality of right-line primary grouting structures 420 arranged at intervals along the right line 120 of the tunnel; wherein the left-line primary grouting structure 410 is located in a U-shaped area enclosed by the middle curtain grouting structure 310, the first longitudinal curtain grouting structure 320 and the transverse curtain grouting structure 340; the right-line primary grouting structure 420 is located in a U-shaped area enclosed by the middle curtain grouting structure 310, the second longitudinal curtain grouting structure 330 and the transverse curtain grouting structure 340; the left-line primary grouting structure 410 vertically extends from the surface to the complete rock layer 720 above the left line 110 of the tunnel, and the right-line primary grouting structure 420 vertically extends from the surface to the complete rock layer 720 above the right line 120 of the tunnel;

[0092] S14, continue to construct a plurality of left-line secondary grouting structures 510 arranged at intervals in the transverse direction along the left line 110 of the tunnel and a plurality of right-line secondary grouting structures 520 arranged at intervals in the transverse direction along the right line 120 of the tunnel; wherein the left-line secondary grouting structures 510 and the left-line primary grouting structures 410 are arranged alternately, and the right-line secondary grouting structures 520 and the right-line primary grouting structures 420 are arranged alternately, the left-line secondary grouting structures 510 vertically extend from the surface to the complete rock stratum 720 above the left line 110 of the tunnel, and the right-line secondary grouting structures 520 vertically extend from the surface to the complete rock stratum 720 above the right line 120 of the tunnel; the curtain grouting structure, the left-line primary grouting structure 410, the right-line primary grouting structure 420, the left-line secondary grouting structure 510 and the right-line secondary grouting structure 520 together form a stratum grouting body structure;

[0093] S15, construct an arch advance support structure in front of the tunnel face.

[0094] It should be noted that over the years, the engineering community has had a large number of tunnel grouting practices, but the design is mainly determined by experience. There is no systematic research on the grouting methods for large-section tunnels passing under water-rich residual slope accumulation bodies, especially shallow buried, small-clearance large-section tunnels. Surface grouting, such as curtain grouting on a large scale, is too expensive, so it is not practical to implement. If anchor rods or steel flower pipes are used for grouting, the water-stopping effect is difficult to guarantee. Therefore, it is difficult for traditional grouting technology to effectively ensure that tunnels pass through water-rich residual slope accumulation areas safely and stably.

[0095] In this embodiment, the scope of the poor geological section belonging to the residual slope accumulation body in the stratum is first determined. Specifically, existing mature technical means, such as on-site survey or in-situ detection, can be used to determine the target area that needs grouting reinforcement based on the scope of the poor disposal section. This area can cover the entire range that may be affected by tunnel excavation to ensure the effectiveness of grouting reinforcement.

[0096] Within the target grouting range, a curtain grouting structure is constructed, extending vertically from the ground surface to the intact rock stratum 720 above the tunnel. The curtain grouting structure includes an intermediate curtain grouting structure 310 (located between the left tunnel line 110 and the right tunnel line 120), a first longitudinal curtain grouting structure 320 (located outside the left tunnel line 110 and extending along the tunnel extension direction), a second longitudinal curtain grouting structure 330 (located outside the right tunnel line 120 and extending along the tunnel extension direction), and two transverse curtain grouting structures 340 arranged at intervals along the tunnel extension direction. As Figure 3 shown, these structures together form a structure in the shape of a Chinese character 'Ri' on the plane, effectively forming a three-dimensional grouting reinforcement framework structure. The curtain grouting structure can effectively block the seepage water from the external area from entering the internal area of the 'Ri'-shaped structure.

[0097] Within the 'Kou'-shaped area enclosed by the curtain grouting structure, a plurality of horizontally spaced primary grouting structures are constructed respectively along the left tunnel line 110 and the right tunnel line 120, further strengthening the stratum; on the basis of the primary grouting structure, a plurality of secondary grouting structures staggered with the primary grouting structure are arranged to form a denser grouting network, further improving the stability and bearing capacity of the stratum.

[0098] As Figure 3 shown, in this embodiment, an implementation method of three grouting structures is adopted, the first 'Ri'-shaped curtain grouting structure, the second 'Shuangmu'-shaped primary grouting structure, and the third 'Shuangri'-shaped secondary grouting structure, with excellent reinforcement effects, can significantly improve the self-stabilization time and bearing capacity of the surrounding rock, reduce the possibility of water inrush during tunnel excavation and operation and maintenance, effectively solve the stability problem of the water-rich residual slope accumulation body within a certain range on the ground surface, and ensure the stability of the poor geological layer during tunnel excavation.

[0099] Furthermore, in front of the tunnel face, an advanced support structure for the arch crown is constructed, which can reinforce and support the stratum in front of the tunnel excavation in advance to prevent the stratum from losing stability or collapsing during the excavation process. The advanced support structure can adopt support structures such as advanced small pipes, steel pipes, steel frames, and anchor rods, and is selected according to specific geological conditions and construction requirements.

[0100] Furthermore, the curtain grouting structure can be obtained by grouting the first grouting hole 350, the primary grouting structure can be obtained by grouting the second grouting hole 430, and the secondary grouting structure can be obtained by grouting the third grouting hole 530. As a preferred example, the opening diameter of the first grouting hole 350, the second grouting hole 430 and the third grouting hole 530 is 91mm, arranged in a plum blossom shape, with a spacing of 1.2×1.2m; the drilling adopts Φ76mm×6mm casing wall protection until entering the vertical reinforcement area. The grouting pipe adopts Φ76mm×6mm grouting steel pipe 370, threaded connection, and the grouting holes are uniformly numbered. The water-cement ratio of cement slurry is 1:2, and 2% water glass is added to the curtain hole slurry.

[0101] The grouting method adopts segmented backward grouting. After the hole is formed once, the grouting is carried out segmentally from bottom to top from the determined grouting section, with 5m as a section. After the initial setting of the grout in the lower section, the grouting pipe is lifted to the upper grouting section, and grouting is carried out again, and so on, until the designed depth. The steel pipe connection adopts threaded connection, and the steel pipe end is processed into a steel flower pipe (Φ8@300) according to 5m.

[0102] Preferably, the reinforcement depth is less than 5.0m for the area with complete rock layer 720 above the tunnel vault, and 5.0m above the top plate of the complete rock layer 720 is the grouting pre-reinforcement area 360, and the direction of the grouting pre-reinforcement area 360 should be consistent with the rock layer distribution line. When there is an unfilled cave on the vault, the grouting depth should extend to 1m below the bottom plate of the cave.

[0103] As a preferred embodiment, Figures 5 to 7 As shown, the arch advance support structure includes a first advance small duct 610, a second advance small duct 620, a third advance small duct 630 and a fourth advance small duct 640; wherein, the first advance small duct 610 has an external insertion angle of 10°, a length of 4m, a longitudinal spacing between two adjacent first advance small ducts 610 of 2m, and an annular spacing of 0.4m, and the first advance small duct 610 is fanned out from the arch to both sides in the annular direction, and the angle between the first advance small duct 610 and the radial direction increases by 1° from the arch to both sides (the radial direction is the direction perpendicular to the surrounding rock, and the angle between the highest point of the arch and the radial direction is 0°);

[0104] The second leading small duct 620 has an external insertion angle of 20° and a length of 4m. The longitudinal spacing between two adjacent second leading small ducts 620 is 2m, and the ring spacing is 0.4m. The second leading small ducts 620 are fanned out from the arch to both sides in the ring direction, and the angle between the second leading small duct 620 and the radial direction increases by 1° from the arch to both sides (the radial direction is the direction perpendicular to the surrounding rock, and the angle between the highest point of the arch and the radial direction is 0°);

[0105] The third leading small conduit 630 has an external insertion angle of 30° and a length of 4.5m. The longitudinal spacing between two adjacent third leading small conduits 630 is 2m, and the ring spacing is 0.4m. The third leading small conduits 630 are fanned out from the arch to both sides in the ring direction, and the angle between the third leading small conduits 630 and the radial direction increases by 1° from the arch to both sides (the radial direction is the direction perpendicular to the surrounding rock, and the angle between the highest point of the arch and the radial direction is 0°);

[0106] The fourth leading small duct 640 has an external insertion angle of 45° and a length of 4.5m. The longitudinal spacing between two adjacent fourth leading small ducts 640 is 2m, and the ring spacing is 0.4m. The fourth leading small duct 640 is fanned out from the arch to both sides in the ring direction, and the angle between the fourth leading small duct 640 and the radial direction increases by 1° from the arch to both sides (the radial direction is the direction perpendicular to the surrounding rock, and the angle between the highest point of the arch and the radial direction is 0°);

[0107] Among them, the first advance small duct 610, the second advance small duct 620, the third advance small duct 630 and the fourth advance small duct 640 are staggered in the longitudinal direction and the transverse direction of the tunnel.

[0108] Specifically, the advance small pipe fills the gaps and cracks in the formation through grouting materials, which improves the integrity and bearing capacity of the formation, thereby realizing the pre-reinforcement of the formation in front of the face. The external insertion angles of the first advance small pipe 610 to the fourth advance small pipe 640 are 10°, 20°, 30° and 45° respectively. This design allows the advance small pipe to gradually penetrate into the formation to form a more stable support structure. The advance small pipe spreads out in a fan shape from the arch to both sides in the annular direction, and the angle with the radial direction increases by 1° from the arch to both sides. This layout method can ensure the uniformity and continuity of the support structure in the lateral direction and improve the support effect. The longitudinal spacing between two adjacent advance small pipes is 2m, and the annular spacing is 0.4m, which can ensure the density and continuity of the support structure in the longitudinal and lateral directions, and further improve the support effect. The first advance small duct 610, the second advance small duct 620, the third advance small duct 630 and the fourth advance small duct 640 are staggered in the longitudinal direction of the tunnel to ensure the continuity and stability of the support structure.

[0109] Compared with the traditional advance small duct, affected by the diffusion radius, especially in the water-rich accumulation area, the grouting filling rate of the ordinary advance small duct is only about 50%, and the grouting reinforcement height is limited, generally not exceeding 2m. It cannot meet the requirements of safe and stable tunnel excavation in areas with large spans, small clearances, and water-rich accumulations. This embodiment adopts a fan-shaped small duct arrangement, which can increase the grouting filling rate of the tunnel roof to more than 80%, and the grouting height of the roof reaches more than 4m, which can be connected with the full coverage of the surface grouting in the above-mentioned embodiment. In addition, the fan-shaped small duct of this embodiment divides the roof reinforcement into four layers, which are reinforced step by step, and have better stability, which is also unattainable by traditional advance small ducts.

[0110] As a better example, the small leading pipes are all made of φ50×5mm hot-rolled seamless steel pipes, and the setting range is 120° of the arch. The front end of the small leading pipe is in a pointed cone shape, and a φ6 stiffening hoop is welded on the tail. The tail end is supported on the tunnel steel arch frame 80 and welded firmly. The longitudinal spacing of the tunnel steel arch frame 80 matches the longitudinal spacing of the small leading pipes. A stop valve is set at the pipe mouth, and φ8mm grouting holes are drilled around the pipe wall. The steel pipe within 0.5m of the pipe mouth section is not drilled, and the rest of the parts are staggered with grouting holes at a spacing of 15cm. After each row of small leading pipes is completed, cement slurry or cement-water glass double liquid slurry needs to be injected. During the grouting process, the grouting pressure should be gradually increased. After reaching 75% strength, the arch is excavated and the initial spraying and steel frame are erected. After the initial support is completed, the next row of steel pipes is drilled. The overlap length between the rings of the small leading pipes is kept at more than 1m.

[0111] As a preferred example, the first advance small duct 610 is grouted with cement slurry, and the second advance small duct 620, the third advance small duct 630 and the fourth advance small duct 640 are grouted with cement-water glass double liquid slurry.

[0112] It is worth noting that cement slurry has high strength and good durability, can form a solid stone body, and provide stable support for the tunnel. Cement-water glass double liquid slurry has the characteristics of rapid setting and controllable setting time, and the gel time of the slurry can be adjusted according to the needs of the project. In addition, the slurry has a high stone rate and high early strength of the stone body, which can effectively improve the stability and bearing capacity of the support structure. By adopting different grouting materials, the advantages of each material can be fully utilized to form a more stable and continuous support structure. In particular, the rapid setting characteristics of cement-water glass double liquid slurry can quickly improve the strength and stability of the support structure and provide strong support for tunnel excavation. The setting time of cement-water glass double liquid slurry is controllable, and the support structure can be quickly formed according to the needs of the project, thereby shortening the construction period and improving construction efficiency.

[0113] As a preferred example, cement slurry is used for grouting of the first advance small tube 610, and the grouting parameters are as follows: ① cement slurry water-cement ratio: 0.8:1~1:1; ② water glass concentration: 35 degrees Baume; modulus: 2.4; ③ grouting pressure: 0.5~1.0MPa; ④ cement to water glass ratio: 1:0.01.

[0114] The second advance small duct 620, the third advance small duct 630 and the fourth advance small duct 640 are grouting with cement-water glass double liquid slurry, and the grouting parameters are as follows: ① Cement slurry water-cement ratio: 0.8:1~1:1; ② Water glass concentration: 35 degrees Baume; modulus: 2.4; ③ Grouting pressure: 0.5~2.0MPa; ④ Cement to water glass ratio: 1:0.25~1:0.32.

[0115] As a preferred embodiment, the high end of the first advance small tube 610, the high end of the second advance small tube 620, the high end of the third advance small tube 630 and the high end of the fourth advance small tube 640 are all embedded in the formation grouting structure.

[0116] Specifically, the high end of the advance small pipe is embedded in the formation grouting structure, which can form a close connection with the formation grouting structure, thereby enhancing the integrity of the entire support structure and improving the bearing capacity and deformation resistance of the support structure; the high end of the advance small pipe is embedded in the grouting structure, which can increase the stability of the support structure. As a filling material, the grouting body can fill the gaps and cracks in the formation and improve the integrity and bearing capacity of the formation. As the main component of the support structure, the high end of the advance small pipe can further increase the stability of the support structure and prevent the formation from loosening and collapse after being embedded in the grouting body.

[0117] As a preferred embodiment, the step S2 specifically includes the following steps:

[0118] S21, excavating the upper left pilot pit 210 in four cycles, firstly constructing the first advance small guide pipe 610 on the surrounding rock side within the excavation range of the upper left pilot pit 210, excavating the first cycle 0.5m, and constructing the corresponding first surrounding rock side initial support 211, the first pilot pit side wall temporary support 212 and the first temporary invert 213;

[0119] S22, construct a second advance small guide tube 620, excavate a second cycle of 0.5m, and construct the corresponding first surrounding rock side initial support 211, first pilot pit side wall temporary support 212 and first temporary invert 213;

[0120] S23, construct the third advance small guide tube 630, excavate the third cycle 0.5m, and construct the corresponding first surrounding rock side initial support 211, the first pilot pit side wall temporary support 212 and the first temporary invert 213;

[0121] S24, construct the fourth advance small guide tube 640, excavate the fourth cycle 0.5m, and construct the corresponding first surrounding rock side initial support 211, the first pilot pit side wall temporary support 212 and the first temporary invert 213.

[0122] Specifically, before each excavation cycle, a small advance pipe is first installed for grouting reinforcement, which effectively improves the stability and bearing capacity of the stratum in front of the excavation face and reduces the risk of stratum collapse. Immediately after excavation, initial support on the surrounding rock side and temporary support on the side wall of the pilot pit, as well as a temporary invert, can quickly form a stable support structure and provide safety for subsequent construction.

[0123] The upper left pilot pit 210 is excavated step by step in four cycles, and each excavation distance is short (preferably 0.5m), which is conducive to controlling the disturbance and deformation of the stratum caused by excavation. Each excavation cycle includes the steps of applying the advance small pipe, excavation, initial support and temporary support, forming a set of standardized operation procedures, which is conducive to improving construction efficiency and quality. Through multiple cycles of excavation and support, a multi-layer support structure is formed, including an advance small pipe grouting reinforcement layer, an initial support layer and a temporary support layer, which jointly improve the overall stability and bearing capacity of the tunnel. The temporary invert is applied in each excavation cycle to increase the lateral stiffness of the support structure and prevent the stratum from being excessively deformed during the excavation process.

[0124] As a preferred implementation, the step S3 specifically includes the following steps:

[0125] S31, after excavating 2 m of the upper left pilot pit 210, excavating the upper right pilot pit 220 in four cycles, firstly constructing the first advance small guide pipe 610 on the surrounding rock side within the excavation range of the upper right pilot pit 220, excavating the first cycle of 0.5 m, and constructing the corresponding second surrounding rock side initial support 221 and second temporary invert 222;

[0126] S32, construct a second advance small guide tube 620, excavate a second cycle of 0.5m, and construct the corresponding second surrounding rock side initial support 221 and second temporary invert 222;

[0127] S33, construct the third advance small guide tube 630, excavate the third cycle 0.5m, and construct the corresponding second surrounding rock side initial support 221 and second temporary invert 222;

[0128] S34, construct the fourth advance small guide tube 640, excavate the fourth cycle 0.5m, and construct the corresponding second surrounding rock side initial support 221 and the second temporary invert 222.

[0129] Specifically, just like excavating the upper left pilot pit 210, the surrounding rock pressure can be gradually released through the method of cyclic excavation and gradual support, avoiding excessive excavation at one time that leads to rapid surface settlement. Timely support is carried out after each excavation to ensure the stability of the excavation surface and provide favorable conditions for subsequent construction. The construction of the second surrounding rock side initial support 221 and the second temporary invert 222 can further reinforce the excavation surface and improve the overall stability of the support structure. The advance small guide tube is combined with the initial support and the temporary invert to form a composite support structure that can better adapt to tunnel excavation under complex geological conditions.

[0130] As a preferred embodiment, the steps S4 to S7 specifically include the following steps:

[0131] After excavating 2m of the upper right pilot pit 220, excavate the upper step 230 of the lower left pilot pit in four cycles, with the advance of each cycle controlled at 0.5m. After each cycle of excavation is completed, the corresponding third surrounding rock side initial support 231 and second pilot pit side wall temporary support 232 are implemented;

[0132] After excavating 2m of the upper step 230 of the lower left pilot pit, the lower step 240 of the lower left pilot pit is excavated in four cycles, with the advance of each cycle controlled at 0.5m. After each cycle of excavation is completed, the corresponding fourth surrounding rock side initial support 241 and the third pilot pit side wall temporary support 242 are implemented;

[0133] After excavating 2m of the lower step 240 of the lower left pilot pit, excavate the upper step 250 of the lower right pilot pit in four cycles, with the advance of each cycle controlled at 0.5m. After each cycle of excavation is completed, the corresponding fifth surrounding rock side initial support 251 and the fourth pilot pit side wall temporary support 252 are implemented;

[0134] After excavating 2m of the upper step 250 of the lower right pilot pit, the lower step 260 of the lower right pilot pit is excavated in four cycles, with the advance of each cycle controlled at 0.5m. After each cycle of excavation is completed, the corresponding initial support 261 of the sixth surrounding rock side and the temporary support 262 of the fifth pilot pit side wall are implemented.

[0135] Specifically, by excavating in steps and cycles, the surrounding rock pressure can be gradually released, reducing the risk of surrounding rock deformation and collapse caused by excessive one-time excavation. After each cycle of excavation is completed, initial support and temporary support are immediately carried out to ensure the stability of the excavation surface and provide safety guarantees for subsequent construction. The step-by-step and cycle-by-cycle excavation method can gradually release the stress in the stratum and avoid excessive one-time excavation that leads to excessive surface settlement. Initial support can quickly reinforce the excavation surface, improve the self-bearing capacity of the surrounding rock, and effectively control surface settlement. The upper pilot pit is excavated first; through multiple cycles of excavation and support, a multi-layer support structure is formed, including initial support and temporary support. These support structures are superimposed on each other to jointly improve the overall stability and bearing capacity of the tunnel.

[0136] As a preferred implementation, the steps S8-S9 specifically include the following steps:

[0137] After excavating 2m of the lower step 260 of the lower right pilot pit, excavate the upper step 271 of the lower reserved core soil in four cycles, with the advance of each cycle controlled at 0.5m;

[0138] After excavating 2 m of the upper step 271 of the lower reserved core soil, the lower step 272 of the lower reserved core soil is excavated in four cycles, with the advance of each cycle controlled at 0.5 m, and the corresponding seventh surrounding rock side initial support 280 is implemented.

[0139] Specifically, by excavating in steps and cycles, the disturbance to the surrounding rock can be reduced, the risk of collapse can be reduced, and the safety of the excavation process can be ensured. The advance of each excavation is controlled at 0.5m, and initial support is applied in time, such as anchor rods, steel mesh, steel arch frame 80 and shotcrete, etc., which can enhance the stability of the surrounding rock, prevent deformation and collapse of the surrounding rock, and ensure the smooth progress of the project.

[0140] Furthermore, the pouring of the secondary lining 290 in step S10 specifically includes the following steps:

[0141] Cast the tunnel invert lining, apply the tunnel composite waterproof layer on the entire section, and cast the secondary lining 290 corresponding to the tunnel arch and tunnel side wall; wherein, the secondary lining 290 should be no more than 20m away from the heading face.

[0142] Specifically, the distance between the secondary lining 290 and the heading face is no more than 20m, which is conducive to controlling the deformation and settlement of the tunnel and ensuring construction safety.

[0143] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereto. Any equivalent structure or equivalent process transformation made by using the contents of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A large-section tunnel construction method for crossing a residual slope accumulation area, characterized in that: It includes the following steps: S1. Grout and reinforce the diluvial-proluvial deposit stratum in front of the tunnel face; S2. Excavate the upper left pilot tunnel of the tunnel, and construct the primary support on the first surrounding rock side corresponding to the upper left pilot tunnel, the temporary support on the side wall of the first pilot tunnel, and the first temporary inverted arch; S3. Excavate the upper right pilot tunnel and construct the primary support on the second surrounding rock side corresponding to the upper right pilot tunnel and the second temporary inverted arch; S4. Excavate the upper bench of the lower left pilot tunnel below the upper left pilot tunnel, and construct the primary support on the third surrounding rock side corresponding to the upper bench of the lower left pilot tunnel and the temporary support on the side wall of the second pilot tunnel; S5. Excavate the lower bench of the lower left pilot tunnel below the upper bench of the lower left pilot tunnel, and construct the primary support on the fourth surrounding rock side corresponding to the lower bench of the lower left pilot tunnel and the temporary support on the side wall of the third pilot tunnel; S6. Excavate the upper bench of the lower right pilot tunnel below the upper right pilot tunnel, and construct the primary support on the fifth surrounding rock side corresponding to the upper bench of the lower right pilot tunnel and the temporary support on the side wall of the fourth pilot tunnel; S7. Excavate the lower bench of the lower right pilot tunnel below the upper bench of the lower right pilot tunnel, and construct the primary support on the sixth surrounding rock side corresponding to the lower bench of the lower right pilot tunnel and the temporary support on the side wall of the fifth pilot tunnel; S8. Excavate the upper bench of the lower reserved core soil between the upper bench of the lower left pilot tunnel and the upper bench of the lower right pilot tunnel; S9. Excavate the lower bench of the lower reserved core soil between the lower bench of the lower left pilot tunnel and the lower bench of the lower right pilot tunnel, and construct the primary support on the seventh surrounding rock side corresponding to the lower bench of the lower reserved core soil; S10. Demolish the temporary support on the side wall of the first pilot tunnel, the first temporary inverted arch, the second temporary inverted arch, the temporary support on the side wall of the second pilot tunnel, the temporary support on the side wall of the third pilot tunnel, the temporary support on the side wall of the fourth pilot tunnel, the temporary support on the side wall of the fifth pilot tunnel, and then pour the secondary lining; The tunnel includes a left tunnel line and a right tunnel line. The step S1 specifically includes the steps: S11. Determine the range of the poor treatment section where the stratum is diluvial-proluvial deposit according to the positions of the left tunnel line and the right tunnel line, and determine the target grouting range according to the range of the poor treatment section; S12. Construct a curtain grouting structure within the target grouting range; wherein, the curtain grouting structure extends vertically from the ground surface to the intact rock stratum above the tunnel. The curtain grouting structure includes an intermediate curtain grouting structure between the left tunnel line and the right tunnel line, a first longitudinal curtain grouting structure outside the left tunnel line, a second longitudinal curtain grouting structure outside the right tunnel line, and two transverse curtain grouting structures arranged at intervals along the tunnel extension direction. The intermediate curtain grouting structure, the first longitudinal curtain grouting structure, the second longitudinal curtain grouting structure, and the transverse curtain grouting structure form a Chinese character 'Ri'-shaped structure on the plane; S13, continue to construct a plurality of left-line primary grouting structures arranged at intervals along the left line of the tunnel and a plurality of right-line primary grouting structures arranged at intervals along the right line of the tunnel; wherein the left-line primary grouting structure is located in a U-shaped area enclosed by the middle curtain grouting structure, the first longitudinal curtain grouting structure and the transverse curtain grouting structure; the right-line primary grouting structure is located in a U-shaped area enclosed by the middle curtain grouting structure, the second longitudinal curtain grouting structure and the transverse curtain grouting structure; the left-line primary grouting structure extends vertically from the surface to the complete rock formation above the left line of the tunnel, and the right-line primary grouting structure extends vertically from the surface to the complete rock formation above the right line of the tunnel; S14, continue to construct a plurality of left-line secondary grouting structures arranged at intervals in the transverse direction along the left line of the tunnel and a plurality of right-line secondary grouting structures arranged at intervals in the transverse direction along the right line of the tunnel; wherein the left-line secondary grouting structure and the left-line primary grouting structure are arranged alternately, and the right-line secondary grouting structure and the right-line primary grouting structure are arranged alternately, the left-line secondary grouting structure extends vertically from the ground surface to the complete rock formation above the left line of the tunnel, and the right-line secondary grouting structure extends vertically from the ground surface to the complete rock formation above the right line of the tunnel; the curtain grouting structure, the left-line primary grouting structure, the right-line primary grouting structure, the left-line secondary grouting structure and the right-line secondary grouting structure together form a stratum grouting body structure; S15, construct an arch advance support structure in front of the tunnel face.

2. The large-section tunnel construction method for crossing a residual slope accumulation area according to claim 1 is characterized in that: The arch advance support structure includes a first advance small conduit, a second advance small conduit, a third advance small conduit and a fourth advance small conduit; wherein, The first leading small duct has an external insertion angle of 10° and a length of 4m. The longitudinal spacing between two adjacent first leading small ducts is 2m, and the circumferential spacing is 0.4m. The first leading small duct spreads out in a fan shape from the dome to both sides in the circumferential direction, and the angle between the first leading small duct and the radial direction increases by 1° from the dome to both sides. The second leading small duct has an external insertion angle of 20° and a length of 4m. The longitudinal spacing between two adjacent second leading small ducts is 2m, and the ring spacing is 0.4m. The second leading small duct spreads out in a fan shape from the arch to both sides in the ring direction, and the angle between the second leading small duct and the radial direction increases by 1° from the arch to both sides. The third leading small duct has an external insertion angle of 30° and a length of 4.5m. The longitudinal spacing between two adjacent third leading small ducts is 2m, and the ring spacing is 0.4m. The third leading small duct spreads out in a fan shape from the arch to both sides in the ring direction, and the angle between the third leading small duct and the radial direction increases by 1° from the arch to both sides. The fourth leading small duct has an external insertion angle of 45° and a length of 4.5 m. The longitudinal spacing between two adjacent fourth leading small ducts is 2 m, and the ring spacing is 0.4 m. The fourth leading small duct spreads out in a fan shape from the arch to both sides in the ring direction, and the angle between the fourth leading small duct and the radial direction increases by 1° from the arch to both sides. The first small advance duct, the second small advance duct, the third small advance duct and the fourth small advance duct are all staggered in the longitudinal direction and the transverse direction of the tunnel.

3. The large-section tunnel construction method for crossing a residual slope accumulation area according to claim 2 is characterized in that: The first advance small duct is grouted with cement slurry, and the second advance small duct, the third advance small duct and the fourth advance small duct are grouted with cement-water glass double liquid slurry.

4. The large-section tunnel construction method for crossing a residual slope accumulation area according to claim 2 is characterized in that: The high end of the first leading small conduit, the high end of the second leading small conduit, the high end of the third leading small conduit and the high end of the fourth leading small conduit are all embedded in the formation grouting body structure.

5. The large-section tunnel construction method for crossing a residual slope accumulation area according to claim 2 is characterized in that: The step S2 specifically includes the following steps: S21, excavating the upper left pilot pit in four cycles, first constructing the first advance small guide pipe on the surrounding rock side within the excavation range of the upper left pilot pit, excavating the first cycle of 0.5m, and constructing the corresponding first surrounding rock side initial support, first pilot pit side wall temporary support and first temporary invert; S22, construct the second advance small guide pipe, excavate the second cycle 0.5m, and construct the corresponding first surrounding rock side initial support, the first pilot pit side wall temporary support and the first temporary invert; S23, construct the third advance small guide pipe, excavate the third cycle 0.5m, and construct the corresponding first surrounding rock side initial support, the first pilot pit side wall temporary support and the first temporary invert; S24, construct the fourth advance small guide tube, excavate the fourth cycle of 0.5m, and construct the corresponding first surrounding rock side initial support, the first pilot pit side wall temporary support and the first temporary invert.

6. The large-section tunnel construction method for crossing a residual slope accumulation area according to claim 5 is characterized in that: The step S3 specifically comprises the following steps: S31, after excavating 2 m of the upper left pilot pit, excavating the upper right pilot pit in four cycles, first constructing the first advance small guide pipe on the surrounding rock side within the excavation range of the upper right pilot pit, excavating the first cycle of 0.5 m, and constructing the corresponding second surrounding rock side initial support and second temporary invert; S32, construct the second advance small guide tube, excavate the second cycle 0.5m, and construct the corresponding second surrounding rock side initial support and the second temporary invert; S33, construct the third advance small guide tube, excavate the third cycle 0.5m, and construct the corresponding second surrounding rock side initial support and second temporary invert; S34, construct the fourth advance small duct, excavate the fourth cycle of 0.5m, and construct the corresponding second surrounding rock side initial support and the second temporary invert.

7. The large-section tunnel construction method for crossing a residual slope accumulation area according to claim 6 is characterized in that: The steps S4 to S7 specifically include the following steps: After the upper right pilot pit is excavated for 2m, the upper step of the lower left pilot pit is excavated in four cycles, with the advance of each cycle controlled at 0.5m. After each cycle of excavation is completed, the corresponding initial support of the third surrounding rock side and temporary support of the second pilot pit side wall are implemented; After excavating 2m of the upper step of the lower left pilot pit, excavate the lower step of the lower left pilot pit in four cycles, with the advance of each cycle controlled at 0.5m. After each cycle of excavation, implement the corresponding initial support of the fourth surrounding rock side and temporary support of the third pilot pit side wall; After excavating 2m of the lower step of the left pilot pit, the upper step of the right pilot pit was excavated in four cycles, with the advance of each cycle controlled at 0.5m. After each cycle of excavation, the corresponding initial support of the fifth surrounding rock side and temporary support of the fourth pilot pit side wall were implemented; After excavating 2m of the upper step of the lower right pilot pit, the lower step of the lower right pilot pit was excavated in four cycles. The advance of each cycle was controlled at 0.5m. After each cycle of excavation was completed, the corresponding initial support of the sixth surrounding rock side and temporary support of the fifth pilot pit side wall were implemented.

8. The large-section tunnel construction method for crossing a residual slope accumulation area according to claim 7 is characterized in that: The steps S8-S9 specifically include the following steps: After excavating 2m of the lower step of the right pilot pit, excavate the upper step of the reserved core soil in the lower part in four cycles, with the advance of each cycle controlled at 0.5m; After excavating 2m of the upper step of the lower reserved core soil, the lower step of the lower reserved core soil is excavated in four cycles, with the advance of each cycle controlled at 0.5m, and the corresponding initial support of the seventh surrounding rock side is implemented.

9. The large-section tunnel construction method for crossing a residual slope accumulation area according to claim 1 is characterized in that: The pouring of the secondary lining in step S10 specifically includes the following steps: Cast the tunnel invert lining, apply the tunnel composite waterproof layer on the entire section, and cast the secondary lining corresponding to the tunnel arch and tunnel side wall; the secondary lining should be no more than 20m away from the heading face.

Images