Tunnel advance support method suitable for soft rock geology

Abstract

The invention discloses a tunnel forepoling method suitable for soft rock geology, and relates to the technical field of soft rock tunnel construction.The tunnel forepoling method suitable for the soft rock geology comprises the steps that surrounding rock of the soft rock geology corresponding to a tunnel is divided into a core reinforcing layer, a transition buffer layer and a peripheral protection layer along the excavation contour line of the tunnel; performing grouting reinforcement on the core reinforcement layer, the transition buffer layer and the peripheral protection layer to form an advance support surface; constructing a cross anchoring network by utilizing the forepoling surface; and a stress monitoring system is installed through the forepoling face, and tunnel forepoling construction of the soft rock geology is completed. The surrounding rock is divided into the core reinforcement layer, the transition buffer layer and the peripheral protection layer for differential grouting reinforcement, and the cross anchoring network is constructed to cooperatively control the shear slippage of the structural surface, so that the construction safety of the soft rock tunnel is improved.

Description

Technical Field

[0001] This invention relates to the field of soft rock tunnel construction technology, and in particular to a tunnel advance support method suitable for soft rock geology. Background Technology

[0002] Soft rock tunnel engineering is a major technical challenge in underground engineering construction. Due to the characteristics of soft rock geology such as low strength, large deformation and poor stability, the surrounding rock is prone to collapse and large deformation after tunnel excavation. Therefore, reliable advanced support technology must be adopted to ensure construction safety.

[0003] Currently, the main technical approach for advance support of soft rock tunnels is a combination of grouting reinforcement and anchoring. For grouting reinforcement, existing technologies typically use a single-component grouting material to uniformly treat the entire reinforced area, with consistent spacing and depth of grouting holes to form a relatively uniform reinforced layer. For anchoring, traditional methods mainly employ radial anchors or pipe roof supports, with anchoring elements arranged along the tunnel's axial or radial direction, providing constraint force to the surrounding rock through prestressing tension. However, existing advance support technologies for soft rock tunnels have the following technical shortcomings: single-layer grouting reinforcement fails to optimize for the rock mass strength gradient distribution. From the excavation outline outwards, the stress state and deformation characteristics of the soft rock surrounding rock exhibit a gradient change, and existing single-layer uniform grouting reinforcement methods cannot match this gradient distribution characteristic; the uncoordinated force distribution in each direction of the anchoring system leads to shear failure of the structural surface, and traditional unidirectional anchoring systems cannot effectively control shear slippage of the structural surface. The aforementioned technical defects directly affect the reliability and economy of advance support for soft rock tunnels, easily leading to safety accidents such as support failure and surrounding rock collapse, while also increasing project costs and construction period. Summary of the Invention

[0004] The main objective of this invention is to propose a tunnel pre-support method suitable for soft rock geology, aiming to improve the construction safety of soft rock tunnels.

[0005] To achieve the above objectives, the present invention proposes a tunnel pre-support method suitable for soft rock geology, comprising:

[0006] Along the excavation outline of the tunnel, the surrounding rock of the soft rock geology corresponding to the tunnel is divided into a core reinforcement layer, a transition buffer layer, and an outer protective layer.

[0007] Grouting reinforcement is performed on the core reinforcement layer, the transition buffer layer and the outer protective layer respectively to form an advanced support surface;

[0008] A cross-anchoring network is constructed using the aforementioned advanced support surface;

[0009] The stress monitoring system installed on the aforementioned advanced support surface is used to complete the advanced support construction of the tunnel in the soft rock geology.

[0010] In one embodiment, the step of dividing the surrounding rock of the soft rock geology corresponding to the tunnel into a core reinforcement layer, a transition buffer layer, and an outer protective layer along the excavation outline of the tunnel includes:

[0011] The area of ​​the surrounding rock, defined as range A outside the excavation outline, is divided into the core reinforcement layer; 0.5m ≤ A ≤ 1.5m;

[0012] The area of ​​the surrounding rock, with a range of B outside the core reinforcement layer, is divided into the transition buffer layer along the excavation outline; 1.5m < B ≤ 3m;

[0013] The area of ​​the surrounding rock, within a range of C outside the transition buffer layer, is divided into the outer protective layer along the excavation outline; 3m < C ≤ 5m.

[0014] In one embodiment, before the step of grouting and reinforcing the core reinforcement layer, the transition buffer layer, and the outer protective layer to form the advanced support surface, the tunnel advanced support method suitable for soft rock geology further includes:

[0015] A first pre-treated hole group is drilled in the outer protective layer with a first preset spacing D1 and a first preset depth H1; wherein, 1.2m < D1 ≤ 2m, 1.5m ≤ H1 ≤ 2m;

[0016] A first pre-treatment hole group is drilled in the outer protective layer with a second preset spacing D2 and a second preset depth H2; wherein, 0.8m < D2 ≤ 1.2m, 2m ≤ H2 ≤ 3m;

[0017] A first pre-treatment hole group is drilled in the outer protective layer with a third preset spacing D3 and a third preset depth H3; wherein, 0.5m < D3 ≤ 0.8m, 3m ≤ H3 ≤ 5m.

[0018] In one embodiment, before the step of grouting and reinforcing the core reinforcement layer, the transition buffer layer, and the outer protective layer to form the advanced support surface, the tunnel advanced support method suitable for soft rock geology further includes:

[0019] The core reinforcement layer concrete is prepared by means of 80 parts cement, 30 parts fly ash and 2 parts penetrating agent by weight.

[0020] A transition buffer layer concrete is prepared, wherein the transition buffer layer concrete comprises 100 parts cement, 20 parts bentonite and 1 part retarder by weight.

[0021] The outer protective layer concrete is prepared by means of 100 parts by weight of quick-setting cement, 15 parts by weight of silica fume and 3 parts by weight of quick-setting agent.

[0022] In one embodiment, the step of constructing a cross-anchoring network using the advanced support surface includes:

[0023] Multiple sets of anchor points are set along the excavation outline of the tunnel on the advanced support surface;

[0024] Install tangential anchoring components using multiple sets of the aforementioned anchoring points;

[0025] Multiple axial anchoring bands are respectively installed on the arch, sidewalls and invert of the tunnel, and multiple anchoring holes parallel to the axis of the tunnel are drilled in each of the axial anchoring bands.

[0026] An axial anchoring assembly is installed using multiple of the aforementioned anchoring holes;

[0027] The tangential anchoring assembly and the axial anchoring assembly are connected using a connector to obtain the cross anchoring network.

[0028] In one embodiment, the step of setting multiple sets of anchor points along the excavation outline of the tunnel on the pre-support face includes:

[0029] Along the excavation outline of the tunnel, a set of anchor points is arranged at intervals E on the advance support surface; wherein, 2m≤E≤3m;

[0030] Drill 3 to 5 tangential holes with a depth of H4 at each of the anchor points; wherein 3m≤H4≤5m.

[0031] In one embodiment, the step of installing the tangential anchoring assembly using multiple sets of said anchoring points includes:

[0032] A short rod is inserted into each of the tangential holes. The length of the short rod is F, and 3m≤E≤5m.

[0033] An annular tray is installed using the short rod; wherein the annular tray has an arc adapted to the surrounding rock.

[0034] In one embodiment, the step of installing the axial anchoring assembly using the plurality of said anchoring holes includes:

[0035] A connecting rod is inserted into each of the anchoring holes;

[0036] The axial anchoring assembly is installed by using U-shaped clips to fix two adjacent sets of connecting rods together.

[0037] In one embodiment, the step of connecting the tangential anchoring assembly and the axial anchoring assembly using a connector to obtain the cross-anchoring network includes:

[0038] The tangential anchoring component and the axial anchoring component are hinged together using a connector to obtain the cross anchoring network.

[0039] In one embodiment, the steps of using the stress monitoring system installed on the pre-support face to complete the pre-support construction of the tunnel in soft rock geology include:

[0040] Stress sensing probes are installed at intervals G on the tunnel's arch crown, arch shoulder, sidewalls, and invert using the aforementioned advanced support surface; wherein 1m≤G≤2m;

[0041] Using the advanced support surface, stress sensing probes are installed at intervals of K in the area of ​​the tunnel excluding the arch crown, arch shoulder, sidewalls and invert arch, to form the stress monitoring system and complete the advanced support construction of the tunnel in soft rock geology; wherein, 3m≤K≤5m.

[0042] The technical solution of this invention divides the surrounding rock into a core reinforcement layer, a transition buffer layer, and an outer protective layer for differentiated grouting reinforcement, and constructs a cross-anchoring network to collaboratively control the shear slip of the structural surface, thereby improving the integrity of the support structure and effectively suppressing the deformation and damage of the surrounding rock. It achieves precise matching between the reinforcement strength and stress distribution of the surrounding rock, improving the utilization rate of grouting materials; it constructs a multi-directional collaborative force-bearing anchoring system, enhancing the shear resistance of the structural surface; and it establishes a zoned and graded monitoring network, providing reliable data support for the stability assessment of the support system and effectively ensuring the safety of soft rock tunnel construction. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0044] Figure 1 This is a schematic flowchart of an embodiment of the tunnel advance support method for soft rock geology provided by the present invention.

[0045] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0047] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0048] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0049] Soft rock tunnel engineering is a major technical challenge in underground engineering construction. Due to the characteristics of soft rock geology such as low strength, large deformation and poor stability, the surrounding rock is prone to collapse and large deformation after tunnel excavation. Therefore, reliable advanced support technology must be adopted to ensure construction safety.

[0050] Currently, the main technical approach for advance support of soft rock tunnels is a combination of grouting reinforcement and anchoring support. For grouting reinforcement, existing technologies typically use a single-component grouting material to uniformly treat the entire reinforced area, with consistent spacing and depth of grouting holes to form a relatively uniform reinforced layer. For anchoring support, traditional methods mainly employ radial anchors or pipe roof supports, with anchoring elements arranged along a single axial or radial direction of the tunnel, providing constraint force to the surrounding rock through prestressing tension.

[0051] However, existing advanced support technologies for soft rock tunnels have the following technical shortcomings:

[0052] First, the stress state and deformation characteristics of soft surrounding rock change gradually from the excavation outline outwards: the stress concentration and deformation are high in the area near the excavation face, requiring high-strength and rapid reinforcement; the middle area acts as a transition buffer and requires reinforcement with a certain degree of toughness; the outer area mainly bears the overall stability and requires large-scale protective reinforcement. However, the existing single-layer uniform grouting reinforcement method cannot match this gradient distribution characteristic, resulting in insufficient reinforcement strength in the area near the excavation face, material waste in the outer area, and an unsatisfactory overall reinforcement effect.

[0053] Second, soft rock commonly contains structural planes such as bedding and joints, which are weak points for surrounding rock instability. Traditional unidirectional anchoring systems (such as radial anchors or axial pipe roofs) can only provide restraint in a specific direction and cannot effectively control the shear slip of structural planes. When the surrounding rock is subjected to stress, structural planes are prone to shear slip along the weak direction of anchoring restraint, leading to anchoring failure and surrounding rock instability.

[0054] The aforementioned technical defects directly affect the reliability and economy of pre-support in soft rock tunnels, easily leading to safety accidents such as support failure and surrounding rock collapse, while also increasing project costs and construction period.

[0055] To address this technical problem, this invention proposes a tunnel pre-support method suitable for soft rock geology.

[0056] Please see Figure 1 In one embodiment of the present invention, the tunnel pre-support method applicable to soft rock geology includes:

[0057] Step S10: Divide the surrounding rock of the soft rock geology corresponding to the tunnel into a core reinforcement layer, a transition buffer layer and an outer protective layer along the excavation outline of the tunnel.

[0058] Step S20: Grouting is performed on the core reinforcement layer, the transition buffer layer and the outer protective layer respectively to form an advanced support surface;

[0059] Step S30: Construct a cross-anchoring network using the advanced support surface;

[0060] Step S40: Install a stress monitoring system on the advanced support surface to complete the advanced support construction of the tunnel in the soft rock geology.

[0061] The core reinforcement layer refers to the surrounding rock area immediately adjacent to the excavation outline. It can be densely filled with high-strength grouting material to quickly form a load-bearing structure. The transition buffer layer is located outside the core layer and can be grouting material with gradually changing elastic modulus to achieve stress transfer and energy dissipation. The outermost protective layer is the outermost layer and can be formed by large-scale permeable grouting to create an overall stable zone. The cross-anchoring network consists of tangential and axial anchoring components hinged together by connectors. It can be formed by arranging short rods and connecting rods in a cross pattern to create a spatial constraint system. The stress monitoring system consists of distributed probes, which can be installed at key locations such as the arch crown and sidewalls to collect surrounding rock stress data in real time.

[0062] Specifically, during construction, three reinforcement layers are first defined based on the mechanical properties of the surrounding rock. The core layer uses high-strength grouting to quickly consolidate the rock mass, the transition layer is injected with tough materials to buffer deformation stress, and the outer layer forms a protective shell through permeable grouting. Then, tangential anchor points are arranged on the pre-support surface, and short rods are installed to form tangential constraints with the annular tray. Connecting rods are installed in the axial anchoring zone through drilling, and connected by U-shaped clips to form axial constraints. Finally, the tangential and axial anchoring components are cross-hinged to form a multi-directional force-bearing spatial network, and stress-sensing probes are placed at key locations for real-time monitoring.

[0063] Compared to existing technologies, traditional methods using homogeneous grouting layers lead to a mismatch between material properties and stress distribution. This solution achieves precise matching of material properties and surrounding rock stress gradients through layered grouting. Traditional unidirectional anchoring provides only constraint in one direction; this solution uses a cross-anchoring network to form a spatial truss structure, effectively suppressing structural shear slip. Traditional monitoring systems suffer from insufficient point density; this solution sets differentiated monitoring intervals based on regional stress differences.

[0064] Through the above technical solutions, this application divides the surrounding rock into a core reinforcement layer, a transition buffer layer, and an outer protective layer for differentiated grouting reinforcement, and constructs a cross-anchoring network to collaboratively control structural surface shear slip, thereby improving the integrity of the support structure and effectively suppressing the deformation and damage of the surrounding rock. It achieves precise matching between the reinforcement strength and stress distribution of the surrounding rock, improving the utilization rate of grouting materials; constructs a multi-directional collaborative force-bearing anchoring system, enhancing the shear resistance of the structural surface; and establishes a zoned and graded monitoring network, providing reliable data support for the stability assessment of the support system and effectively ensuring the safety of soft rock tunnel construction.

[0065] In an embodiment of the present invention, the step of dividing the surrounding rock of the soft rock geology corresponding to the tunnel into a core reinforcement layer, a transition buffer layer, and an outer protective layer along the excavation outline of the tunnel includes:

[0066] Step S11: Divide the area of ​​the surrounding rock outside the excavation outline (range A) into the core reinforcement layer; 0.5m ≤ A ≤ 1.5m;

[0067] Step S12: Divide the area of ​​the surrounding rock with a range of B outside the core reinforcement layer into the transition buffer layer along the excavation outline; 1.5m < B ≤ 3m;

[0068] Step S13: Divide the area of ​​the surrounding rock with a range of C outside the transition buffer layer into the outer protective layer along the excavation outline; 3m < C ≤ 5m.

[0069] The core reinforcement layer refers to the rock mass reinforcement area immediately adjacent to the excavation outline. This can be achieved through grouting reinforcement, and its range is set between 0.5 and 1.5 meters. It provides high-strength support to address the high stress concentration near the excavation face. The transition buffer layer refers to the rock mass treatment area outside the core reinforcement layer. This can be achieved by filling joints and fissures with flexible grouting materials, and its range is set between 1.5 and 3 meters. It absorbs the deformation energy of the surrounding rock through the material's toughness. The outermost protective layer refers to the outermost stable rock mass area, which can be achieved through large-scale grouting consolidation, and its range is set between 3 and 5 meters. This forms an integral protective structure to maintain the stability of the surrounding rock.

[0070] Specifically, a core reinforcement layer, a transition buffer layer, and an outer protective layer are sequentially arranged outward from the excavation outline. The extent of each layer is determined based on the stress gradient distribution of the surrounding rock. The core reinforcement layer rapidly forms a high-strength reinforcement zone through dense grouting over a small area. The transition buffer layer forms a deformation buffer zone through flexible grouting over a medium area. The outer protective layer forms an overall stable zone through consolidation grouting over a larger area. The thickness of each layer is determined through on-site rock mechanics testing. For example, core drilling can be used to determine the rock mass strength attenuation curves at different depths, thereby matching the reinforcement requirements of each layer.

[0071] Compared with existing technologies, traditional single-layer grouting reinforcement methods do not consider the gradient characteristics of the decrease in surrounding rock strength with depth, resulting in insufficient reinforcement in the near-excavation area and redundant material in the outer area. This scheme divides the reinforcement into three layers, allowing the grouting parameters to be matched to the mechanical properties of the surrounding rock at different depths. For example, the core reinforcement layer uses a high-permeability material to quickly seal surface cracks, the transition buffer layer uses a composite material with gradually changing elastic modulus to adapt to deformation coordination, and the outer protective layer uses a low-viscosity grout to achieve large-scale diffusion consolidation.

[0072] Through the above technical solution, this application can implement differentiated reinforcement based on the stress distribution characteristics of different depth areas in soft rock geology. The core reinforcement layer effectively inhibits rock spalling near the excavation face, the transition buffer layer alleviates deformation transmission caused by stress redistribution, and the outer protective layer prevents the loosening and expansion of deep rock mass, thereby forming a synergistic composite reinforcement system that significantly improves the overall stability and deformation resistance of the advanced support structure.

[0073] In an embodiment of the present invention, before the step of grouting and reinforcing the core reinforcement layer, the transition buffer layer, and the outer protective layer to form an advanced support surface, the tunnel advanced support method suitable for soft rock geology further includes:

[0074] Step S101: Drill a first pre-treated hole group in the outer protective layer with a first preset spacing D1 and a first preset depth H1; wherein, 1.2m < D1 ≤ 2m, 1.5m ≤ H1 ≤ 2m;

[0075] Step S102: Drill a first pre-treatment hole group in the outer protective layer with a second preset spacing D2 and a second preset depth H2; wherein, 0.8m < D2 ≤ 1.2m, 2m ≤ H2 ≤ 3m;

[0076] Step S103: Drill a first pre-treatment hole group in the outer protective layer with a third preset spacing D3 and a third preset depth H3; wherein, 0.5m < D3 ≤ 0.8m, 3m ≤ H3 ≤ 5m.

[0077] The first pretreatment borehole group refers to a group of boreholes with relatively large spacing and shallow depth formed on the surface of the outer protective layer. This can be achieved using a hydraulic drilling rig positioned according to a preset coordinate grid, and its function is to provide channels for initial infiltration grouting. The second pretreatment borehole group refers to a group of boreholes with medium spacing and medium depth, which can be achieved using a step-by-step drilling process. Its function is to enhance the diffusion range of the grouting material within the rock mass. The third pretreatment borehole group refers to a group of boreholes with smaller spacing and greater depth, which can be achieved using a casing-following drilling process. Its function is to establish deep grouting channels to form a continuous reinforcement structure.

[0078] Specifically, during the phased drilling operation of the outer protective layer, the first pretreatment hole group is drilled with a relatively large spacing and shallow depth, for example, a spacing of 1.5m and a depth of 1.8m. Low-viscosity grout is injected through this hole group to achieve shallow penetration. Subsequently, the second pretreatment hole group is drilled with a denser spacing and a deeper depth, for example, a spacing of 1.0m and a depth of 2.5m, and medium-viscosity grout is injected to fill the rock mass fissures. Finally, the third pretreatment hole group is drilled with the smallest spacing and the largest depth, for example, a spacing of 0.6m and a depth of 4m, and high-viscosity grout is injected to form a deep skeletal structure. The three sets of pretreatment holes with different parameters form a grouting channel network from shallow to deep and from sparse to dense.

[0079] Compared to existing technologies, the current method uses a single spacing and depth for grouting holes, resulting in uneven grout diffusion and an inability to adapt to the stress gradient distribution of the outer protective layer. This proposed solution uses pre-treated hole groups with different spacings and depths in stages, allowing the grouting material to sequentially fill rock fissures at different depths. This creates a layered reinforcement structure that penetrates from the shallow layer to the deep framework, effectively matching the strength gradient requirements of the surrounding rock in the outer area.

[0080] Through the above technical solution, this application achieves hierarchical control of grouting reinforcement of the outer protective layer, avoiding the problems of shallow grout waste and insufficient deep reinforcement caused by traditional uniform grouting. The staged drilling process allows the grout to gradually penetrate into rock fissures at different depths, forming a continuous and dense reinforcement layer, significantly improving the outer protective layer's ability to constrain the overall deformation of the surrounding rock, while reducing the amount of grouting material used by approximately 20% to 30%.

[0081] In an embodiment of the present invention, before the step of grouting and reinforcing the core reinforcement layer, the transition buffer layer, and the outer protective layer to form an advanced support surface, the tunnel advanced support method suitable for soft rock geology further includes:

[0082] Step S104: Prepare the core reinforcement layer concrete, which comprises 80 parts cement, 30 parts fly ash and 2 parts penetrant by mass.

[0083] Step S105: Prepare the transition buffer layer concrete, wherein the transition buffer layer concrete comprises 100 parts cement, 20 parts bentonite and 1 part retarder by mass.

[0084] Step S106: Prepare the outer protective layer concrete, wherein the outer protective layer concrete comprises 100 parts by weight of quick-setting cement, 15 parts by weight of silica fume and 3 parts by weight of quick-setting agent.

[0085] The core reinforcement layer concrete refers to the high-strength grouting material used in the area near the excavation face. Specifically, it can be achieved using cement as the main binder, fly ash as the filler, and a penetrant as an additive to improve the grout's permeability. This mix enhances the filling effect on loose rock masses by increasing permeability. The transition buffer layer concrete refers to the toughening grouting material used in the intermediate transition area. Specifically, it can be achieved using bentonite as a toughening component and a retarder as an additive to regulate setting time. This mix ensures sufficient diffusion of the grout in fissures by delaying setting time. The outer protective layer concrete refers to the rapidly curing material used in the outer area. Specifically, it can be achieved using fast-setting cement as the base material, silica fume as a reinforcing agent, and a accelerator as an additive to accelerate the curing reaction. This mix achieves timely support of the outer rock mass by rapidly forming a strength layer.

[0086] Specifically, prior to grouting, specialized concrete is prepared for the functional requirements of different reinforcement areas. The core reinforcement layer uses a highly permeable grout, which, through a penetrating agent, promotes the penetration of the grout into the micro-fractures of the rock mass, forming a dense reinforced body. The transition buffer layer uses a plastic grout containing bentonite, with a retarder extending the grout flow time to form a ductile buffer layer. The outer protective layer uses a fast-setting material, with a quick-setting agent shortening the setting time to rapidly form a high-strength protective shell. This achieves a gradient reinforcement system from the inside out, matching the stress distribution characteristics of different areas.

[0087] Compared with existing technologies, traditional grouting processes use a single-component grout for full-section reinforcement, which cannot meet the different needs of the high-stress concentration zone near the excavation face and the low-stress zone on the periphery. In contrast, this solution adjusts the grout ratio in layers to achieve high-permeability reinforcement in the core area, a flexible buffer in the transition zone, and rapid support in the outer area, forming a composite reinforcement structure that matches the stress gradient of the surrounding rock.

[0088] Through the above technical solution, this application solves the problem that a single grouting material cannot meet the functional requirements of different reinforcement areas, and realizes efficient permeable reinforcement of the near-excavation face area, deformation buffering of the middle area and rapid support of the outer area, effectively improving the overall stability and economy of the advanced support system for soft rock tunnels.

[0089] In an embodiment of the present invention, the step of constructing a cross-anchoring network using the advanced support surface includes:

[0090] Step S31: Set multiple sets of anchor points on the advanced support surface along the excavation outline of the tunnel;

[0091] Step S32: Install tangential anchoring components using multiple sets of anchoring points;

[0092] Step S33: Multiple axial anchoring bands are respectively installed on the arch, sidewalls and invert of the tunnel, and multiple anchoring holes parallel to the axis of the tunnel are drilled in each of the axial anchoring bands.

[0093] Step S34: Install the axial anchoring assembly using the plurality of anchoring holes;

[0094] Step S35: Connect the tangential anchoring assembly and the axial anchoring assembly using a connector to obtain the cross anchoring network.

[0095] The cross-anchoring network refers to a three-dimensional support system formed by the spatial cross-connection of tangential and axial anchoring components. Tangential anchoring components, through annular trays adapted to the curvature of the surrounding rock surface, provide radial restraint; axial anchoring components, connected by U-shaped clips, form a continuous support band, restricting longitudinal displacement. Connectors use a hinged method to connect anchoring components in different directions, allowing for minor deformation of each component under stress while maintaining overall coordination. The spacing between anchoring points is controlled within a reasonable range, for example, 2–3 meters, to ensure that the support density matches the stress distribution of the surrounding rock.

[0096] Specifically, anchor point groups are arranged at predetermined intervals on the pre-support surface. Each group has multiple tangential holes drilled and short rods and annular trays installed to form a tangential constraint system. Simultaneously, anchoring strips are installed along the tunnel axis, with anchoring holes drilled parallel to the axis and connecting rods installed, forming a continuous axial support structure via U-shaped clips. Finally, tangential and axial components are connected at intersections using hinged connectors to form a spatial network structure. This network suppresses radial deformation of the surrounding rock through tangential components, restricts longitudinal slippage through axial components, and coordinates force transmission in different directions through connectors. For example, when structural shear occurs, the hinged connections at intersections can redistribute stress and avoid localized stress concentration.

[0097] Compared to existing technologies, traditional unidirectional anchoring systems can only provide constraints in a single direction, while cross-anchoring networks form a multi-directional constraint system through spatial cross-connections. In existing technologies, radial anchors cannot effectively control axial displacement, and pipe roof supports lack radial constraints. This solution, however, through the synergistic effect of tangential and axial components, can simultaneously suppress radial deformation and longitudinal slippage of the surrounding rock. Furthermore, the hinged connection method, compared to rigid connections, allows the support structure to adaptively adjust during surrounding rock deformation, avoiding anchoring failure due to excessive local stress.

[0098] Through the above technical solution, this application effectively solves the problem of structural surface shear failure in soft rock tunnels. The cross-anchoring network suppresses the relative displacement of the structural surface in different directions through multi-directional constraints, and the hinged connection enhances the adaptability of the support system to surrounding rock deformation. The spatial cross arrangement of axial anchoring strips and tangential anchoring components significantly improves the overall synergy of the support structure, enabling the surrounding rock stress to be uniformly transmitted through the mesh structure, avoiding anchoring failure caused by local stress concentration.

[0099] In an embodiment of the present invention, the step of setting multiple sets of anchor points along the excavation outline of the tunnel on the pre-support surface includes:

[0100] Step S311: Along the excavation outline of the tunnel, arrange a set of anchor points at intervals E on the advance support surface; wherein, 2m≤E≤3m;

[0101] Step S312: Drill 3 to 5 tangential holes with a depth of H4 at each of the anchor points; wherein 3m≤H4≤5m.

[0102] The interval range E refers to the horizontal distance between two adjacent sets of anchor points. This can be achieved using a laser rangefinder in conjunction with positioning markers. This interval range balances anchor density and construction efficiency, avoiding material waste due to overly dense anchor points or insufficient support strength due to overly sparse anchor points. The tangential hole depth H4 refers to the length of the borehole extending tangentially into the surrounding rock. This can be controlled using a hydraulic anchor drilling rig in conjunction with a depth sensor. This depth range ensures that the anchoring force is effectively transmitted to the stress adjustment zone of the surrounding rock, enhancing the constraint on surrounding rock deformation.

[0103] Specifically, the arrangement of anchor points, through optimization of the interval range E, ensures a uniform stress distribution throughout the tunnel circumference. Each anchor point group is designed with 3 to 5 tangential holes, forming a multi-directional anchoring support unit. The tangential hole depth H4 allows the anchor components to penetrate the loosened zone of the surrounding rock, with the anchor ends embedded in stable rock strata. This arrangement effectively suppresses layered stripping and localized collapse of the surrounding rock by controlling the density and spatial distribution of the anchoring units.

[0104] Compared to existing technologies, traditional methods typically involve anchor point spacing greater than 3 meters and insufficient drilling depth, resulting in ineffective anchoring force coverage of the fractured rock zone. This solution, by limiting the range of anchor point spacing and drilling depth, avoids support blind spots caused by insufficient anchoring density and prevents the risk of anchor bolt detachment due to excessively shallow anchoring depth, significantly improving the overall synergistic effect of the anchoring system.

[0105] Through the above technical solutions, this application achieves adaptive control of the deformation gradient of the surrounding rock. The reasonable spacing of the anchor points and the combination of borehole depth effectively suppress the shear slip of the structural surface. The arrangement of multiple tangential holes forms a spatial anchoring matrix, which enhances the support system's ability to constrain the multi-directional deformation of the surrounding rock and prevents support failure caused by local stress concentration.

[0106] In an embodiment of the present invention, the step of installing a tangential anchoring assembly using multiple sets of anchoring points includes:

[0107] Step S321: Insert short rods into each of the tangential holes. The length of the short rods is F, 3m≤E≤5m.

[0108] Step S322: Install the annular tray using the short rod; wherein the annular tray has an arc adapted to the surrounding rock.

[0109] The short rod refers to a rigid support component installed within the tangential hole, which can be made of threaded steel or fiberglass anchor rods, with a length ranging from 3 to 5 meters, used to transfer the anchoring force to the deeper parts of the surrounding rock. The annular plate refers to an arc-shaped pressure-bearing plate connected to the end of the short rod, which can be manufactured by stamping or casting steel plates. Its curvature design can be matched according to the curvature of the tunnel excavation outline, used to increase the contact area with the surrounding rock and achieve uniform stress distribution.

[0110] Specifically, after short rods are inserted into the tangential borehole, the annular tray conforms to the surrounding rock surface through its curvature, forming a surface contact support structure. When the surrounding rock deforms, the annular tray, through its curvature adaptation, transforms localized concentrated stress into surface load, preventing tray deformation or surrounding rock crushing caused by stress concentration. Simultaneously, the combination of the short rods and the annular tray evenly distributes the tangential anchoring force along the tunnel outline, enhancing the restraint effect of the anchoring components on the surrounding rock.

[0111] Compared to existing technologies, traditional anchoring systems using planar trays or unidirectional anchors result in uneven stress distribution at the contact surface between the surrounding rock and the tray, making them prone to shear failure at the structural surface. This solution, however, uses a circular tray with an adapted curvature to ensure that the anchoring support force is orthogonal to the deformation direction of the surrounding rock, effectively suppressing shear slip at the structural surface.

[0112] Through the above technical solution, this application significantly improves the shear resistance of the tangential anchoring component, enabling the anchoring system to adapt to the deformation characteristics of soft surrounding rock, preventing anchoring failure caused by local stress concentration, thereby improving the overall stability of the advanced support structure.

[0113] In an embodiment of the present invention, the step of installing the axial anchoring assembly using the plurality of anchoring holes includes:

[0114] Step S341: Insert connecting rods into each of the anchoring holes;

[0115] Step S342: Use U-shaped clips to fix two adjacent sets of connecting rods together, thus completing the installation of the axial anchoring assembly.

[0116] Among them, the connecting rod refers to a rigid support component extending along the tunnel axis, which can be made of threaded steel rod or fiberglass anchor rod. Its function is to form a continuous force transmission path through axial extension, so as to uniformly transfer the stress of the surrounding rock along the longitudinal direction of the tunnel. The U-shaped buckle refers to a metal connector with a U-shaped cross section, which can be made of hot-dip galvanized steel sheet by stamping. Its function is to achieve mechanical interlocking between multiple rods by wrapping the ends of adjacent connecting rods, so as to form an overall structure that cooperates in bearing the force.

[0117] Specifically, after drilling the anchoring holes, the connecting rods are first inserted into the holes and extended to the designed length. The ends of adjacent sets of connecting rods are secured with U-shaped clips, with the inner wall of the clips tightly fitted to the surface of the rods. Pre-tightening force is applied using a bolt fastening device. This connection method creates a continuous support system between anchoring bands of different axes. When the surrounding rock deforms, the connecting rods achieve stress redistribution through the constraint of the U-shaped clips, avoiding anchoring failure caused by localized stress concentration.

[0118] Compared to existing technologies, traditional axial anchoring often uses independent anchor rods with a support plate for fixation, lacking effective connections between adjacent anchor rods, resulting in a discrete distribution of axial restraint forces. This solution, however, uses U-shaped clips to achieve a rigid connection between adjacent connecting rods, forming a continuous axial support network, significantly improving the anchoring system's resistance to structural shear deformation.

[0119] Through the above technical solution, this application effectively solves the problem of insufficient synergy of axial anchoring elements in soft rock tunnels. By using a rigid connection structure, the axial anchoring band forms an integral force-bearing system. When shear slip occurs in the surrounding rock, the shear stress can be dispersed through the synergistic effect of the connecting rod and the U-shaped buckle, preventing support failure caused by structural surface misalignment.

[0120] In an embodiment of the present invention, the step of connecting the tangential anchoring component and the axial anchoring component using a connector to obtain the cross-anchoring network includes:

[0121] Step S351: Using a connector, the intersecting portions of the tangential anchoring component and the axial anchoring component are hinged to obtain the cross-anchoring network.

[0122] A connector is a mechanical device used to connect anchoring components in different directions. Specifically, it can be implemented using a metal component with a rotary joint, and its internal hinge mechanism allows for adjustable angles. A hinge is a connection method that allows two connecting parts to rotate relative to each other within a certain angle range. This can be achieved through a ball joint or pin structure, enabling the anchoring component to adaptively adjust its angle under stress.

[0123] Specifically, in a cross-anchoring network, the tangential anchoring component is attached to the surrounding rock surface via an annular tray, while the axial anchoring component extends along the tunnel axis via a connecting rod. When the surrounding rock deforms, the hinged connector allows for slight angular changes at the intersection of the tangential and axial anchoring components, avoiding stress concentration caused by rigid connections. For example, when shear displacement occurs at the structural surface, the rotational degree of freedom at the hinge can absorb some of the displacement, maintaining the overall stress balance of the anchoring network.

[0124] In some implementations, the hinge portion of the connector can be filled with damping material to control the rotation amplitude, or the maximum rotation angle can be adjusted by a limit bolt. For example, a ball joint connector may have an internal rubber gasket that allows rotation while providing elastic restraint.

[0125] Compared to existing technologies, traditional anchoring systems use welding or bolting to connect anchoring elements in different directions, leading to excessive bending moments at the connection points and eventual failure during structural shear. This solution, however, utilizes a hinged design, allowing the anchoring network to adaptively adjust to surrounding rock deformation and preventing localized stress exceeding limits.

[0126] Through the above technical solution, this application effectively solves the problem of uncoordinated forces in all directions of the anchoring system, significantly reducing the risk of shear failure of the structural surface. The hinged connection method enables the tangential and axial anchoring components to form a dynamic and coordinated system, which can maintain overall stability even under large deformation conditions in soft rock, and improves the adaptability of the support structure to complex stress states.

[0127] In an embodiment of the present invention, the steps for completing the tunnel pre-support construction in soft rock geology by using the stress monitoring system installed on the pre-support face include:

[0128] Step S41: Using the advanced support surface, stress sensing probes are installed at intervals G on the tunnel's arch crown, arch shoulder, sidewalls, and invert; wherein 1m≤G≤2m;

[0129] Step S42: Using the advanced support surface, stress sensing probes are installed at intervals of K in the area of ​​the tunnel excluding the arch crown, arch shoulder, sidewall, and invert arch to form the stress monitoring system and complete the advanced support construction of the tunnel in soft rock geology; wherein, 3m≤K≤5m.

[0130] In this context, G-spacing refers to the density of stress-sensing probes in key stress-bearing areas such as the tunnel crown, shoulders, sidewalls, and invert. A spacing of 1 to 2 meters is typically used, balancing monitoring accuracy with equipment cost. K-spacing refers to the density of probes in other non-critical areas of the tunnel, typically using a spacing of 3 to 5 meters. This spacing reduces the number of probes while ensuring basic monitoring coverage. Stress-sensing probes are sensor devices used to monitor changes in surrounding rock stress in real time. They can be resistive or fiber optic sensors, embedded within the reinforced layer to capture stress fluctuation signals. The stress monitoring system is a distributed monitoring network composed of multiple stress-sensing probes. Data can be collected and sent to a central processor via wireless transmission or wired connection to achieve dynamic monitoring of the surrounding rock stress state.

[0131] Specifically, after the pre-support face is formed, stress sensing probes are first installed in key areas such as the arch crown, arch shoulders, sidewalls, and invert at intervals of 1 to 2 meters. For example, one probe is placed every 1.5 meters on the arch crown. Subsequently, probes are installed in the remaining areas of the tunnel at intervals of 3 to 5 meters, for example, one probe is placed every 4 meters in non-critical sections of the sidewalls. All probes are connected to a monitoring terminal via data cables, forming a monitoring network covering the entire tunnel cross-section. During construction, the probes collect surrounding rock stress data in real time, and the system can issue early warning signals promptly when abnormal stress concentration is detected.

[0132] Compared to existing technologies, traditional stress monitoring systems typically employ a uniform distribution across the entire tunnel cross-section, resulting in insufficient monitoring density in critical areas and redundant equipment in non-critical areas. This solution, by dividing critical and non-critical areas and setting differentiated spacing, ensures monitoring sensitivity in high-stress areas while reducing overall equipment investment.

[0133] Through the above technical solution, this application can accurately capture the stress concentration phenomenon in key parts of soft rock tunnels, provide timely warnings before shear slippage occurs in the surrounding rock, and reduce the construction cost of the monitoring system by optimizing the density of probes, thus achieving a balance between safety and economy.

[0134] Based on the above embodiments, a specific implementation method is shown here for ease of understanding:

[0135] The soft rock tunnel pre-support method of this invention includes three main technical stages: First, a layered progressive pretreatment stage, which pre-treats the soft rock mass in layers to create favorable conditions for subsequent support; second, a multi-directional cross-anchoring network construction stage, which establishes a three-dimensional support network based on the pretreatment; and finally, a dynamic stress transfer control stage, which achieves surrounding rock stability by controlling the stress transfer path. These three stages are performed sequentially in time and overlap spatially to form a continuous support effect.

[0136] Detailed implementation plan for the layered progressive pretreatment stage:

[0137] The layered, progressive pretreatment stage is the foundation of the entire advanced support method. The core of this stage lies in layering the surrounding rock mass according to different structural features and strength distributions, based on the geological characteristics of the soft rock. In practice, a detailed geological survey of the soft rock mass ahead of the tunnel excavation face is first required. Through drilling and on-site testing, the bedding structure, joint development, and physical and mechanical parameters of each rock layer are determined. Based on this data, the surrounding rock mass ahead is divided into three different treatment layers: a core reinforcement layer, a transition buffer layer, and an outer protective layer.

[0138] The core reinforcement layer is located within 0.5 to 1.5 meters outside the tunnel excavation outline, and this layer is the area most directly affected by excavation disturbance. In this layer, a dense pretreatment method is required. Specifically, a treatment point is set every 0.8 meters along the tunnel outline, and at each treatment point, a pretreatment hole with a depth of 3 to 5 meters is drilled into the soft rock mass ahead. The arrangement of these pretreatment holes must take into account the orientation of the soft rock's structural planes. When the soft rock has obvious bedding planes, the pretreatment holes should be at an angle of 30 to 45 degrees to the bedding planes to avoid drilling along weak structural planes. After drilling is completed, a rapidly solidifying reinforcement material is injected into the holes using a high-pressure injection method, significantly improving the strength and integrity of the soft rock mass.

[0139] The transition buffer layer is located within 1.5 to 3 meters outside the core reinforcement layer. Its function is to mitigate the transfer of excavation stress to the deeper rock mass. Within the transition buffer layer, the spacing between pretreatment points can be appropriately widened to 1.2 meters, and the depth of the pretreatment holes should be controlled at 2 to 3 meters. Because this layer is relatively far from the excavation face and experiences less direct disturbance, a more permeable but longer-setting reinforcement material can be used. When injecting the reinforcement material, the injection pressure needs to be controlled to avoid adversely affecting the already treated core reinforcement layer.

[0140] The outer protective layer is located within 3 to 5 meters of the transition buffer layer. This layer mainly serves to stabilize the overall structure and disperse stress. Within the outer protective layer, the spacing between pretreatment points is further increased to 2 meters, and the depth of the pretreatment holes is 1.5 to 2 meters. The focus of this layer is not on significantly increasing the strength of the rock mass, but on improving the integrity of the rock mass and preventing large-scale loosening and collapse.

[0141] The entire layered, progressive pretreatment process must be strictly carried out in the order from the outer protective layer to the core reinforcement layer. This ensures sufficient surrounding rock constraint during the treatment of the inner layers and avoids uncontrollable deformation during the treatment process. After each layer of pretreatment is completed, a curing period of 24 to 48 hours is required to ensure that the reinforcement material can fully function before proceeding to the next layer.

[0142] Detailed implementation plan for the construction phase of the multi-directional cross-anchoring network:

[0143] After the layered, progressive pretreatment is completed and the design strength is achieved, the construction phase of the multi-directional cross-anchoring network begins. The innovation of this phase lies in overcoming the limitations of traditional single-directional anchoring and establishing a three-dimensional anchoring support system. The multi-directional cross-anchoring network consists of three subsystems: a main anchoring system, an auxiliary anchoring system, and a connection and reinforcement system.

[0144] The main anchoring system forms the backbone of the entire network and is arranged radially. In practice, using the tunnel centerline as a reference, main anchoring points are set at equal angular intervals on the tunnel cross-section, typically 8 to 12 points per cross-section. Anchoring holes are drilled radially outward from each main anchoring point. The length of the anchoring holes is determined based on the geological conditions of the soft rock, usually 0.8 to 1.2 times the tunnel span. During drilling, the main anchoring holes need to pass through each pre-treated layer to ensure a tight connection between the pre-treated layer and the original surrounding rock, forming an integrated load-bearing structure.

[0145] When drilling the main anchoring hole, special attention must be paid to the influence of structural planes in soft rock. When the anchoring hole encounters a weak structural plane, a variable-angle drilling technique should be used. This involves adjusting the drilling angle as you approach the structural plane, allowing the anchoring hole to pass through the structural plane at a larger angle, thus increasing the effective anchoring length. For soft rock with well-developed bedding, the main anchoring hole should be as perpendicular as possible to the direction of the main bedding plane to maximize the anchoring effect.

[0146] The auxiliary anchoring system adds tangential and axial anchoring components to the main anchoring system. Tangential anchoring is arranged along the tunnel outline, with a group of tangential anchoring points every 2 to 3 meters, each group containing 3 to 5 anchoring holes. The length of the tangential anchoring holes is relatively short, generally 3 to 5 meters, and their main function is to restrain the tangential deformation of the surrounding rock and prevent shear failure. Axial anchoring is arranged along the tunnel axis, with axial anchoring bands installed at the tunnel arch, sidewalls, and invert, each containing multiple parallel axial anchoring holes. The function of axial anchoring is to connect the surrounding rock at different cross-sections into a whole, avoiding longitudinal uneven deformation.

[0147] The connection reinforcement system is a key innovation of the multi-directional cross-anchoring network. This system establishes mechanical connections between anchoring components in different directions, creating a true three-dimensional load-bearing system for the entire anchoring network. The connection reinforcement system must be implemented after the main and auxiliary anchoring installations are completed. Specifically, connection nodes are installed at the outer ends of the anchor holes, and adjacent anchoring components are connected using high-strength connectors. The design of the connection nodes must consider the deformation characteristics of soft rock, employing a connection method with a certain degree of flexibility to both transfer loads and accommodate reasonable deformation of the surrounding rock.

[0148] In constructing a multi-directional cross-anchoring network, the drilling and installation of each anchor hole must be carried out in a specific sequence. First, the anchor holes located at the arch crown and invert positions in the main anchoring system are completed; these anchor holes play the primary load-bearing role. Then, the main anchor holes, tangential anchor holes, and axial anchor holes at the sidewall positions are completed sequentially. After each set of anchor holes is installed, pre-tensioning is required to establish effective prestress between the anchor components and the surrounding rock. The amount of pre-tensioning needs to be determined based on the strength and deformation modulus of the soft rock, generally controlled between 60% and 80% of the design bearing capacity of the anchor components.

[0149] Detailed implementation plan for the dynamic stress transfer control stage:

[0150] The dynamic stress transfer control stage is the third core technical aspect of this invention. Building upon the first two stages, this stage achieves long-term maintenance of surrounding rock stability by actively controlling the stress transmission path and distribution. Dynamic stress transfer control includes three main steps: establishing a stress monitoring network, optimizing stress transmission paths, and dynamic adjustment control.

[0151] The establishment of a stress monitoring network is the foundation of dynamic control. After the multi-directional cross-anchoring network is constructed, stress monitoring points need to be installed at key locations. The layout of monitoring points follows the principle of combining focused monitoring with comprehensive coverage. Dense monitoring points are set up at major stress-bearing parts such as the tunnel arch, abutments, sidewalls, and invert, with a spacing of 1 to 2 meters between monitoring points. General monitoring points are set up at other locations, with a spacing of 3 to 5 meters. Each monitoring point needs to be able to measure stress components in three directions to comprehensively reflect the stress state at that point.

[0152] Stress transmission path optimization is a core component of dynamic control. Based on stress monitoring data, the transmission patterns and distribution characteristics of stress in the surrounding rock are analyzed to identify stress concentration areas and weak points. For stress concentration areas, stress dispersion measures are needed, specifically by adding auxiliary support structures around the stress concentration point to disperse the concentrated stress over a wider area. For stress-weak points, stress strengthening measures are needed, such as locally increasing anchorage density or improving anchorage strength to improve the stress state of the area.

[0153] Optimizing stress transfer paths requires considering the structural features of soft rock. Bedding planes and joints in soft rock are often weak points in stress transfer, prone to stress concentration or interruption. To address this, cross-structural-plane anchoring technology is needed. This involves installing specialized anchoring components that span the main structural plane, connecting the rock mass on both sides of the plane into a unified whole. The direction of the cross-structural-plane anchoring should be perpendicular to the strike of the structural plane, and the anchoring length should be sufficient to traverse the area of ​​influence of the structural plane.

[0154] Dynamic adjustment and control is the final step in the entire method. This step involves real-time adjustments to the support system based on stress monitoring results and surrounding rock deformation. Dynamic adjustment includes three aspects: prestress adjustment, support strength adjustment, and support range adjustment. Prestress adjustment changes the stress state of the surrounding rock by adjusting the tension of the anchoring components. When monitoring reveals that the stress in a certain area is too low, the prestress of the anchoring components in that area can be appropriately increased; when the stress is found to be too high, the prestress can be appropriately reduced or new support structures can be added to share the load.

[0155] Adjusting the support strength involves modifying support parameters based on the actual performance of the surrounding rock. If the stability of the surrounding rock in a certain area is found to be better than expected, the support strength in that area can be appropriately reduced to save materials and costs; if the stability of the surrounding rock in a certain area is found to be worse than expected, the support strength needs to be increased promptly to ensure safety. Adjusting the support range involves adjusting the spatial range of the support based on changes in the area affected by the surrounding rock. When the area of ​​loosened surrounding rock is found to be expanding, the support range needs to be expanded accordingly; when the surrounding rock condition is stable, the support range can be optimized.

[0156] The entire dynamic stress transfer control process needs to be continuous, from the start of tunnel excavation until the surrounding rock condition is completely stable. During control, a robust feedback mechanism is required to adjust control strategies promptly based on monitoring data. Simultaneously, an early warning mechanism is also necessary to ensure construction safety by taking timely emergency measures when monitoring data indicates abnormalities in the surrounding rock condition.

[0157] The above description is merely an exemplary embodiment of the present invention and does not limit the scope of protection of the present invention. Any equivalent structural transformations made based on the technical concept of the present invention and the contents of the specification and drawings of the present invention, or direct / indirect applications in other related technical fields, are included within the scope of protection of the present invention.

Claims

1. A method for advance support of tunnels suitable for soft rock geology, characterized in that, include: Along the excavation outline of the tunnel, the surrounding rock of the soft rock geology corresponding to the tunnel is divided into a core reinforcement layer, a transition buffer layer, and an outer protective layer. Grouting reinforcement is performed on the core reinforcement layer, the transition buffer layer and the outer protective layer respectively to form an advanced support surface; A cross-anchoring network is constructed using the aforementioned advanced support surface; The stress monitoring system installed on the aforementioned advanced support surface is used to complete the advanced support construction of the tunnel in the soft rock geology.

2. The tunnel pre-support method applicable to soft rock geology as described in claim 1, characterized in that, The steps of dividing the surrounding rock of the soft rock geology corresponding to the tunnel into a core reinforcement layer, a transition buffer layer, and an outer protective layer along the excavation outline of the tunnel include: The area of ​​the surrounding rock, defined as range A outside the excavation outline, is divided into the core reinforcement layer; 0.5m ≤ A ≤ 1.5m; The area of ​​the surrounding rock, with a range of B outside the core reinforcement layer, is divided into the transition buffer layer along the excavation outline; 1.5m < B ≤ 3m; The area of ​​the surrounding rock, within a range of C outside the transition buffer layer, is divided into the outer protective layer along the excavation outline; 3m < C ≤ 5m.

3. The tunnel advance support method applicable to soft rock geology as described in claim 2, characterized in that, Before the step of grouting and reinforcing the core reinforcement layer, the transition buffer layer, and the outer protective layer to form the advanced support surface, the tunnel advanced support method suitable for soft rock geology further includes: A first pre-treated hole group is drilled in the outer protective layer with a first preset spacing D1 and a first preset depth H1; wherein, 1.2m < D1 ≤ 2m, 1.5m ≤ H1 ≤ 2m; A first pre-treatment hole group is drilled in the outer protective layer with a second preset spacing D2 and a second preset depth H2; wherein, 0.8m < D2 ≤ 1.2m, 2m ≤ H2 ≤ 3m; A first pre-treatment hole group is drilled in the outer protective layer with a third preset spacing D3 and a third preset depth H3; wherein, 0.5m < D3 ≤ 0.8m, 3m ≤ H3 ≤ 5m.

4. The tunnel advance support method applicable to soft rock geology as described in claim 3, characterized in that, Before the step of grouting and reinforcing the core reinforcement layer, the transition buffer layer, and the outer protective layer to form the advanced support surface, the tunnel advanced support method suitable for soft rock geology further includes: The core reinforcement layer concrete is prepared by means of 80 parts cement, 30 parts fly ash and 2 parts penetrating agent by weight. A transition buffer layer concrete is prepared, wherein the transition buffer layer concrete comprises 100 parts cement, 20 parts bentonite and 1 part retarder by weight. The outer protective layer concrete is prepared by means of 100 parts by weight of quick-setting cement, 15 parts by weight of silica fume and 3 parts by weight of quick-setting agent.

5. The tunnel advance support method applicable to soft rock geology as described in any one of claims 1 to 4, characterized in that, The steps for constructing a cross-anchoring network using the aforementioned advanced support surface include: Multiple sets of anchor points are set along the excavation outline of the tunnel on the advanced support surface; Install tangential anchoring components using multiple sets of the aforementioned anchoring points; Multiple axial anchoring bands are respectively installed on the arch, sidewalls and invert of the tunnel, and multiple anchoring holes parallel to the axis of the tunnel are drilled in each of the axial anchoring bands. An axial anchoring assembly is installed using multiple of the aforementioned anchoring holes; The tangential anchoring assembly and the axial anchoring assembly are connected using a connector to obtain the cross anchoring network.

6. The tunnel advance support method applicable to soft rock geology as described in claim 5, characterized in that, The step of setting multiple sets of anchor points along the excavation outline of the tunnel on the pre-support face includes: Along the excavation outline of the tunnel, a set of anchor points is arranged at intervals E on the advance support surface; wherein, 2m≤E≤3m; Drill 3 to 5 tangential holes with a depth of H4 at each of the anchor points; wherein 3m≤H4≤5m.

7. The tunnel advance support method applicable to soft rock geology as described in claim 6, characterized in that, The steps of installing the tangential anchoring assembly using multiple sets of the aforementioned anchoring points include: A short rod is inserted into each of the tangential holes. The length of the short rod is F, and 3m≤E≤5m. An annular tray is installed using the short rod; wherein the annular tray has an arc adapted to the surrounding rock.

8. The tunnel advance support method applicable to soft rock geology as described in claim 7, characterized in that, The steps of installing the axial anchoring assembly using the plurality of said anchoring holes include: A connecting rod is inserted into each of the anchoring holes; The axial anchoring assembly is installed by using U-shaped clips to fix two adjacent sets of connecting rods together.

9. The tunnel advance support method applicable to soft rock geology as described in claim 8, characterized in that, The step of connecting the tangential anchoring assembly and the axial anchoring assembly using a connector to obtain the cross-anchoring network includes: The tangential anchoring component and the axial anchoring component are hinged together using a connector to obtain the cross anchoring network.

10. The tunnel advance support method applicable to soft rock geology as described in claim 9, characterized in that, The steps for completing the tunnel pre-support construction in soft rock geology by installing a stress monitoring system on the pre-support face include: Stress-sensing probes are installed at intervals G on the tunnel's arch crown, arch shoulder, sidewalls, and invert using the aforementioned advanced support surface; wherein 1m≤G≤2m; Using the advanced support surface, stress sensing probes are installed at intervals of K in the area of ​​the tunnel excluding the arch crown, arch shoulder, sidewalls and invert arch, to form the stress monitoring system and complete the advanced support construction of the tunnel in soft rock geology; wherein, 3m≤K≤5m.

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