Anchoring structure and construction method for preventing floor heave in a roadway

Abstract

This invention belongs to the field of disaster prevention technology in underground engineering and tunnel engineering, and particularly relates to an anchoring structure and construction method for preventing roadway floor heave. The structure includes a crushed stone cushion layer at the bottom of the roadway, on which multiple bottom plate anchors are installed. Anchor mesh and steel strips are laid on the surface of the crushed stone cushion layer and fixed to the tops of the multiple bottom plate anchors. The edges of the anchor mesh and steel strips are turned upwards along the roadway sidewall and fixed to one end of a sidewall anchor fixed below the roadway sidewall. The bottom plate anchor includes a rod body and clamping parts fixed at both ends of the rod body. The clamping parts include trays and nuts, with the crushed stone cushion layer, anchor mesh, and steel strip clamped between two trays. A prefabricated steel mold is also provided and placed on the surface of the weak rock layer to position the bottom end of the bottom plate anchor. A pre-tightening force is applied by tightening the nuts with a torque wrench. The sidewall anchors are fixed to the rock layer with an anchoring agent. The construction method of this anchoring structure is also disclosed.

Description

Technical Field

[0001] This invention belongs to the field of disaster prevention and control technology in underground engineering and tunnel engineering, and particularly relates to an anchoring structure and construction method for preventing roadway floor heave. Background Technology

[0002] With the continuous development of deep underground engineering, the high ground stress environment in which tunnels are located is becoming increasingly complex.

[0003] During the construction and service of tunnels, even with adequate support for the roof and sides, the tunnel floor often becomes the weakest link in the entire support system. Under intense high ground stress and severe compression from the overlying strata, the surrounding rock of the floor is prone to deviatoric stress concentration, which can induce plastic failure of the rock mass and the initiation of shear slip zones. Under subsequent construction disturbances and long-term rheological effects, the internal stress environment of the surrounding rock of the floor continuously adjusts dynamically, and the rock mass will undergo continuous expansion and displacement along the slip lines, eventually evolving into severe large deformation disasters of the floor, which greatly threaten the safety and normal operation of the project.

[0004] Traditional methods for controlling floor heave primarily rely on rigid or semi-rigid support methods such as concrete inverted arches, floor grouting, and ordinary anchor bolts. However, in actual engineering projects, these existing structures have revealed significant limitations: high-strength rigid support structures struggle to adapt to the large deformation characteristics of the floor slab, failing to effectively release the deformation energy accumulated deep within the floor slab. Under continuous high ground pressure, they are highly susceptible to structural fracture or cracking failure, inevitably leading to secondary or even multiple severe deformations even after support is in place. Once traditional rigid support structures are damaged, their high material integrity and extreme difficulty in dismantling create significant obstacles to on-site repair and cleanup, greatly increasing construction difficulty and maintenance costs, and severely impacting the tunnel construction progress. Furthermore, existing floor heave prevention systems often lack supporting and effective in-situ testing methods, making it difficult to dynamically and quantitatively assess the internal stress evolution mechanism and prevention effect of the support structure during construction and service.

[0005] Therefore, there is an urgent need for an anchoring structure and construction method for preventing roadway floor heave. Summary of the Invention

[0006] The purpose of this invention is to provide an anchoring structure and construction method for preventing roadway floor heave, so as to solve the above-mentioned problems.

[0007] To achieve the above objectives, the present invention provides the following solution: An anchoring structure for preventing roadway floor heave, comprising: A crushed stone cushion layer is set at the bottom of the tunnel, and multiple bottom plate anchors are provided on the crushed stone cushion layer.

[0008] Anchor mesh and steel strips are laid on the surface of the crushed stone cushion layer, and the anchor mesh and steel strips are fixed to the top of the plurality of bottom plate anchors.

[0009] The edges of the anchor mesh and the steel strip turn upwards along the roadway sidewall and are fixed to one end of the sidewall anchor rod located below the roadway sidewall.

[0010] Optionally, the base plate anchor bolt includes a rod body and clamping portions fixed at both ends of the rod body. The crushed stone cushion layer, the anchor mesh, and the steel strip are located between the two clamping portions, and the clamping portions are threadedly engaged with the rod body.

[0011] After the crushed stone pad is filled between the two clamping parts, the clamping part at the top rotates and, in cooperation with the threaded section of the rod, pushes the anchor mesh and the steel strip to squeeze the crushed stone pad to form a preload.

[0012] Optionally, the clamping part includes a tray and a nut, the nut being threaded into the rod body, and the tray being fixed to the rod body by the nut.

[0013] The crushed stone cushion layer, the anchor mesh, and the steel strip are held between the two trays.

[0014] Optionally, a precast steel mold is also provided, located at the bottom end of the base plate anchor rod.

[0015] The precast steel mold is set on the surface of the weak rock layer below the crushed stone cushion layer. The precast steel mold has a through hole in the middle that matches the nut so that the nut and the precast steel mold are radially limited and matched. One end of the nut has an edge that is longitudinally limited and matched with the precast steel mold. After the nut and the tray are placed into the precast steel mold in sequence, the bottom end of the rod is passed through the tray and tightened with the nut so that the bottom end of the rod passes through the precast steel mold and enters the weak rock layer.

[0016] Optionally, a torque wrench is also included. After the nut engages with the threaded top of the rod and presses against the tray, the anchor mesh, and the steel strip, the torque wrench rotates the nut to apply a preload until the torque wrench reaches a preset torque.

[0017] Optionally, the side anchor bolt is fixed to the rock strata by an anchoring agent.

[0018] A construction method for an anchoring structure used to prevent roadway floor heave, comprising the following steps: Obtain the design depth of the crushed stone cushion layer and the design spacing between the multiple bottom plate anchor bolts.

[0019] The designated area where the weak rock layer is removed is used to create a filling area.

[0020] Multiple base plate anchors are fixed within the filling area.

[0021] The crushed stone cushion layer is formed by laying crushed stone in the filling area.

[0022] The side anchor bolts are fixed by drilling holes on both sides of the tunnel.

[0023] The anchor mesh and the steel strip are laid on the surface of the crushed stone cushion layer, and the anchor mesh and the steel strip are fixed to the top of the multiple bottom plate anchors and one end of the side anchors located below the roadway sidewall.

[0024] A preload is applied to the crushed stone cushion layer.

[0025] Optionally, the method for obtaining the design depth of the crushed stone cushion layer includes the following steps: Obtain the depth of the plastic zone in the tunnel.

[0026] Set the excavation safety factor.

[0027] The design depth of the crushed stone cushion layer is obtained based on the functional relationship between the design depth of the crushed stone cushion layer, the depth of the plastic zone of the roadway, and the excavation safety factor.

[0028] Optionally, the method for obtaining the design spacing of the multiple base plate anchor bolts includes the following steps: Obtain the resistance stress value.

[0029] Obtain the design bearing capacity value of a single anchor bolt in the base plate.

[0030] The design spacing is obtained based on the functional relationship between the design spacing, the design bearing capacity of a single root, and the resistance stress value.

[0031] Compared with the prior art, the present invention has the following advantages and technical effects: This invention integrates the flexible pressure-absorbing characteristics of the crushed stone cushion layer with a rigid anchoring system composed of floor anchors, side anchors, anchor mesh, and steel strips, achieving an organic synergy between flexible floor pressure relief and high-strength anchoring constraints. The anchor mesh and steel strips connect the floor anchors and side anchors to form a closed-loop joint support system, effectively transferring and dispersing concentrated stress from the roadway floor to the sidewalls. The mutual compression effect between crushed stone particles creates a pressure arch effect, adapting to large deformations of the floor under high ground stress. The floor anchors employ a tray and nut clamping structure, with precise pre-tightening force applied using a torque wrench to ensure the crushed stone cushion layer is fully compressed and compacted, enhancing the interlocking force between the anchors and the crushed stone cushion layer. Precast steel molds serve a positioning and guiding function during construction, ensuring the floor anchors remain upright and stable when laying crushed stone, significantly reducing construction difficulty. The base slab anchors are fixed solely by mechanical clamping without the use of anchoring agents, overcoming the technical limitations of conventional anchoring agents being difficult to apply in the special environment of the base slab. Furthermore, when secondary maintenance is required, the crushed stone cushion layer is easily dismantled and cleaned, effectively avoiding the extremely difficult dismantling and severe obstruction of secondary construction that often occurs with rigid support structures such as traditional concrete inverted arches after damage. The side anchors are reliably fixed to the rock strata using anchoring agents, ensuring the stability of the closed support system's edges. This structure achieves immediate load-bearing capacity of the support system, significantly improving the overall load-bearing capacity and support reliability of the surrounding rock of the base slab. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described 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 these drawings without creative effort. Figure 1 This is a schematic diagram of the in-situ soft rock tunnel of the present invention.

[0033] Figure 2 This is a schematic diagram of the bottom slab tunnel of the crushed stone anchoring structure of the present invention.

[0034] Figure 3 This is a schematic diagram of the in-situ test of the bottom plate of the crushed stone anchoring structure in the roadway according to the present invention.

[0035] Figure 4 This is a structural diagram of the crushed stone anchoring structure of the present invention when a preload is applied.

[0036] Figure 5 This is a schematic diagram of the anchoring of the side anchor bolt of the present invention.

[0037] Figure 6 This is a schematic diagram of the arrangement of the anchor bolt force gauge in the base plate of the present invention.

[0038] Figure 7 This is a schematic diagram of the bottom structure of the anchor rod of the base plate of the present invention.

[0039] Among them, 1. hard rock layer; 2. soft rock layer; 3. gravel cushion layer; 4. hydraulic servo jack; 5. monitoring and control platform; 7. torque wrench; 8. nut; 9. pallet; 10. anchor net; 11. steel strip; 12. anchoring agent; 13. precast steel mold. Detailed Implementation

[0040] 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 some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] Example 1: Reference Figures 1 to 7 This invention discloses an anchoring structure for preventing roadway floor heave, comprising: A crushed stone cushion layer 3 is set at the bottom of the tunnel, and multiple bottom plate anchors are provided on the crushed stone cushion layer 3.

[0043] Anchor mesh 10 and steel strip 11 are laid on the surface of the crushed stone cushion layer 3, and the anchor mesh 10 and steel strip 11 are fixed to the top of multiple bottom plate anchor rods.

[0044] The edges of the anchor mesh 10 and the steel strip 11 are turned up along the sidewall of the roadway and fixed to one end of the sidewall anchor rod located below the sidewall of the roadway.

[0045] The tunnel is situated within a hard rock stratum 1, with a soft rock stratum 2 adjacent to its bottom. During construction, a crushed stone cushion layer 3 is first laid at the bottom of the tunnel, upon which multiple floor anchor bolts are installed. Then, anchor mesh 10 and steel strips 11 are laid on the surface of the crushed stone cushion layer 3, securing them to the tops of each floor anchor bolt. Simultaneously, the edges of the anchor mesh 10 and steel strips 11 are turned upwards along the tunnel sidewalls and fixed to one end of a sidewall anchor bolt located below the sidewalls. Through this structure, the crushed stone cushion layer 3 provides flexible pressure relief and energy absorption, while the anchor mesh 10 and steel strips 11 connect the floor anchor bolts and sidewall anchor bolts into a closed combined support system, effectively transferring and dispersing stress from the floor to the sidewalls and preventing large deformations of the floor.

[0046] As an optional implementation, the base plate anchor bolt includes a rod body and clamping parts fixed at both ends of the rod body. The crushed stone cushion layer 3, the anchor mesh 10 and the steel strip 11 are located between the two clamping parts, and the clamping parts are threadedly engaged with the rod body.

[0047] After the crushed stone cushion layer 3 is filled between the two clamping parts, the clamping part at the top rotates and pushes the anchor net 10 and steel strip 11 to squeeze the crushed stone cushion layer 3 under the action of the threaded engagement with the rod body to form a pre-tightening force.

[0048] The base plate anchor bolt includes a bolt body and clamping parts fixed at both ends of the bolt body. A crushed stone cushion layer 3, an anchor mesh 10, and a steel strip 11 are located between the two clamping parts, which are threadedly engaged with the bolt body. During construction, the crushed stone cushion layer 3 is filled first, and then the top clamping part is rotated. Under the action of the threaded engagement, the clamping part pushes the anchor mesh 10 and the steel strip 11 downwards, compressing the crushed stone cushion layer 3 to form a pre-tightening force. This process compacts the crushed stone particles, enhancing the interlocking effect between the crushed stone cushion layer 3 and the base plate anchor bolt.

[0049] As an optional implementation, the clamping part includes a tray 9 and a nut 8, the nut 8 being threaded into the rod body, and the tray 9 being fixed to the rod body by the nut 8.

[0050] The crushed stone cushion layer 3, the anchor mesh 10, and the steel strip 11 are sandwiched between two trays 9.

[0051] Nut 8 is threaded into the rod body, and tray 9 is fixed to the rod body via nut 8. The crushed stone pad layer 3, anchor mesh 10, and steel strip 11 are held between two trays 9. In use, tightening nut 8 pushes tray 9, which presses the anchor mesh 10 and steel strip 11, thereby compressing the crushed stone pad layer 3. Tray 9 increases the pressing contact area, preventing nut 8 from directly damaging the anchor mesh 10 or steel strip 11 and ensuring uniform transmission of preload.

[0052] Specifically, the tray 9 is slidably mounted on the rod. The nut 8 is tightened to limit the fit of the tray 9. After the gravel pad 3 is filled, the tray 9 at the bottom is pressed by the gravel pad 3 due to the limiting effect of the nut 8. The tray 9 at the bottom applies a preload to the top of the gravel pad 3 due to the limiting effect of the nut 8.

[0053] As an optional implementation, a precast steel mold 13 is also provided, located at the bottom end of the bottom plate anchor rod.

[0054] The precast steel mold 13 is set on the surface of the weak rock layer 2 below the crushed stone cushion layer 3. The precast steel mold 13 has a through hole in the middle that matches the nut 8 so that the nut 8 is radially limited to the precast steel mold 13. One end of the nut 8 has an edge that is longitudinally limited to the precast steel mold 13. After the nut 8 and the tray 9 are placed into the precast steel mold 13 in sequence, the bottom end of the rod is passed through the tray 9 and tightened with the nut 8 so that the bottom end of the rod passes through the precast steel mold 13 and enters the weak rock layer 2.

[0055] The precast steel mold 13 is placed on the surface of the weak rock layer 2 below the crushed stone cushion layer 3. During construction, the nut 8 and tray 9 at the bottom of the base plate anchor are first placed into the precast steel mold 13. Then, the bottom end of the base plate anchor is inserted into the tray 9, nut 8, precast steel mold 13, and weak rock layer 2 in sequence. The precast steel mold 13 plays a positioning and guiding role during construction, ensuring that the base plate anchor remains upright and stable when laying crushed stone, thus reducing the difficulty of construction.

[0056] As an optional implementation, it also includes a torque wrench 7. After the nut 8 is threaded into the top of the rod and squeezes the tray 9, the anchor net 10 and the steel strip 11, the torque wrench 7 is used to rotate the nut 8 to apply a preload until the torque wrench 7 reaches the preset torque.

[0057] After the nut 8 engages with the threaded top of the rod and presses against the tray 9, anchor mesh 10, and steel strip 11, the nut 8 is rotated using the torque wrench 7 to apply preload until the torque wrench 7 reaches the preset torque value. Using the torque wrench 7 allows for precise control of the preload, avoiding insufficient or excessive preload, ensuring uniform stress on the anchoring structure and meeting design requirements.

[0058] As an alternative implementation, the side anchor bolt is fixed to the rock strata by anchoring agent 12.

[0059] The sidewall anchors are fixed to the rock strata by anchoring agent 12. Since the surrounding rock of the roadway sidewall is relatively intact, the use of anchoring agent 12 can provide reliable anchoring force, ensuring that the sidewall anchors are firmly bonded to the rock mass, providing a stable fixing point for the upturned edge of the anchor mesh 10 and steel strip 11, and realizing the coordinated bearing of the floor and sidewall support system.

[0060] Example 2: A construction method for an anchoring structure used to prevent roadway floor heave, comprising the following steps: Obtain the design depth of the crushed stone cushion layer 3 and the design spacing of multiple bottom plate anchor bolts.

[0061] The designated area of ​​the weak rock layer 2 is excavated to form a filling area.

[0062] Multiple base plate anchors are fixed within the filling area.

[0063] A crushed stone cushion layer 3 is formed by laying crushed stone in the filling area.

[0064] Drill holes on both sides of the tunnel to fix the side anchor bolts.

[0065] Anchor mesh 10 and steel strip 11 are laid on the surface of the crushed stone cushion layer 3, and the anchor mesh 10 and steel strip 11 are fixed to the top of multiple bottom plate anchors and one end of the side anchors fixed below the roadway sidewall.

[0066] Apply preload to the crushed stone cushion layer 3.

[0067] First, the design depth of the crushed stone cushion layer 3 and the design spacing of the bottom plate anchors are obtained. A designated area of ​​the weak rock layer 2 is excavated to form a filling area. Multiple bottom plate anchors are fixed within the filling area. Crushed stone is laid to form the crushed stone cushion layer 3. Holes are drilled on both sides to fix the side anchors. Anchor mesh 10 and steel strip 11 are laid on the surface of the crushed stone cushion layer 3 and fixed to the top of the bottom plate anchors and one end of the side anchors. Finally, a preload is applied to the crushed stone cushion layer 3. This method achieves the organic integration of a flexible pressure layer and a rigid anchoring system, resulting in high construction efficiency and ease of secondary maintenance.

[0068] As an optional implementation method, the method for obtaining the design depth of the crushed stone cushion layer 3 includes the following steps: Obtain the depth of the plastic zone in the tunnel.

[0069] Set the excavation safety factor.

[0070] The depth of the crushed stone layer on the roadway floor is obtained based on the functional relationship between the depth of the crushed stone layer on the roadway floor, the depth of the roadway plastic zone, and the excavation safety factor.

[0071] When determining the design depth of the crushed stone subbase 3, it is based on the depth of the plastic zone of the roadway. H p And specify the excavation safety factor. k 1. Determine the depth of the crushed stone layer through calculation. H s The calculation formula is shown in equation (1).

[0072] (1) In the formula, H s Depth of the crushed stone layer for the tunnel floor k 1 represents the safety factor. H p The depth of the plastic zone in the tunnel.

[0073] As an optional implementation method, the method for obtaining the design spacing of multiple base plate anchor bolts includes the following steps: Obtain the resistance stress value.

[0074] Obtain the design bearing capacity value of a single anchor bolt in the base plate.

[0075] The design spacing between rows is obtained based on the functional relationship between the design spacing, the design bearing capacity of a single column, and the resistance stress.

[0076] Among them, the resistance stress value is obtained by detecting the ground stress data of the roadway and specifying the safety factor value. The resistance stress value is the product of the ground stress data and the safety factor value.

[0077] The design spacing is obtained based on the functional relationship between the design spacing, the design bearing capacity of a single bar, and the resistance stress value. The calculation formula is shown in equation (2).

[0078] (2) In the formula, Q This represents the design bearing capacity value for a single section. σ d To resist stress values, s This refers to the spacing between anchor bolts.

[0079] The specific construction methods for tunnel floor heave prevention structures are as follows: First, based on the Figure 1 The results of the investigation of the weak rock stratum 2 in the prototype tunnel shown indicate the design depth of the subbase. Subsequently, a pre-treatment process is performed on the floor slab, replacing the weak rock stratum 2 with... Figure 2 The shown is the gravel cushion layer 3.

[0080] Subsequently, holes are drilled at the bottom of the filled area after the foundation is laid, according to the designed spacing, and the anchor rods of the base plate are fixed inside the holes. It is worth noting that no resin anchoring agent is used for the base plate anchor rods. Instead, the anchor rods are kept upright and stable during the subsequent laying of crushed stone by mechanically pressing on the tray 9 placed at the end of the hole and tightening the nut 8.

[0081] The steps for fixing the bottom anchor are as follows: First, place the precast steel mold 13 into the reserved space, then screw the nut 8 into the anchor body, then place the tray 9, and finally tighten the nut until it is completely locked.

[0082] The precast steel mold 13 has a through hole in the middle that matches the structure of the nut 8, and the nut 8 has an edge that cannot pass through the through hole, so that the precast steel mold 13 and the nut 8 can achieve longitudinal and radial limiting.

[0083] This ensures the stability and precise placement of the anchor bolts, and greatly reduces the difficulty of construction.

[0084] After the anchor bolts on the bottom slab are fixed, backfilling and laying of the crushed stone cushion layer 3 begin, and holes are drilled on both sides of the tunnel to drive in the anchor bolts. Figure 5 The side anchor bolts shown are reliably anchored using anchoring agent 12 to ensure corner stability. Next, a metal anchor mesh is laid on the surface of the crushed stone cushion layer 3, connecting the tops of the upright bottom anchor bolts and the tops of the side anchor bolts into a single unit. Steel strips 11 and anchor mesh 10 are then laid on top to form a closed network. Finally, trays and nuts are installed at the ends of all anchor bolts. Construction personnel... Figure 4The torque wrench 7 is used to tighten the nut 8 to apply a preload to the bottom plate anchoring system, thereby enhancing the interlocking force between the anchor rod and the crushed stone cushion layer 3, and finally forming the bottom plate anchoring support structure.

[0085] After the bottom anchor bolt is fixed, the crushed stone cushion layer 3 applies pressure to the tail of the bottom plate anchor bolt to achieve mechanical clamping, thus pre-fixing the anchor bolt. As the thickness of the crushed stone cushion layer 3 gradually increases, the mechanical clamping effect gradually strengthens, the pressure arching effect inside the crushed stone cushion layer 3 gradually intensifies, and the interlocking effect between the anchor bolt and the rock is amplified. Finally, a pre-tightening force is applied to the top of the bottom plate anchor bolt using a torque wrench 7, which greatly enhances the friction effect and interlocking force between the anchor bolt and the crushed stone, thereby achieving the anchor bolt fixing effect.

[0086] Example 3: To verify the structural reliability, during the construction of a project using this structure, when laying the aforementioned crushed stone cushion layer 3, after the paving depth reached the reserved depth for jack placement, a hydraulic servo jack 4 was placed inside the cushion layer and connected to the external monitoring and control platform 5. Crushed stone was then laid and buried. Simultaneously, after laying the anchor mesh 10 and steel strip 11, matching anchor rod force gauges were installed at the fixed ends of the bottom plate anchor rods at key stress locations, and then the nuts 8 were tightened to ensure anchor rod stability.

[0087] After the overall anchoring and anti-bulging structure is constructed, the on-site loading test phase can begin. Testing personnel operate the monitoring and control platform 5 to drive the internally embedded hydraulic servo jacks 4, applying complex simulated load conditions consistent with the engineering site to the anchoring structure. Throughout the test, the system comprehensively analyzes the load and displacement data of the hydraulic servo jacks 4 collected in real time by the monitoring and control platform 5, combined with the stress changes fed back by the anchor bolt force gauge. After loading is completed, by generating corresponding force-displacement curves, technicians can inversely calculate and accurately evaluate the bearing capacity and deformation characteristics of the anchoring structure under actual high ground pressure conditions. This demonstrates that the structure can effectively disperse the horizontal stress of the tunnel floor, thus verifying that the structure can effectively control the floor bulging phenomenon induced by high ground stress in the tunnel.

[0088] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0089] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. An anchoring structure for preventing roadway floor heave, characterized in that, include: A crushed stone cushion layer (3) is set at the bottom of the tunnel, and multiple bottom plate anchors are provided on the crushed stone cushion layer (3); Anchor mesh (10) and steel strip (11) are laid on the surface of the crushed stone cushion layer (3), and the anchor mesh (10) and the steel strip (11) are fixed to the top of the plurality of bottom plate anchor rods; The edges of the anchor net (10) and the steel strip (11) are turned up along the sidewall of the roadway and fixed to one end of the sidewall anchor rod located below the sidewall of the roadway.

2. The anchoring structure for preventing roadway floor heave according to claim 1, characterized in that, The bottom plate anchor includes a rod body and clamping parts fixed at both ends of the rod body. The crushed stone cushion layer (3), the anchor mesh (10) and the steel strip (11) are located between the two clamping parts. The clamping parts are threadedly engaged with the rod body. After the crushed stone pad (3) is filled between the two clamping parts, the clamping part at the top rotates and pushes the anchor net (10) and the steel strip (11) to squeeze the crushed stone pad (3) to form a preload under the action of the threaded engagement with the rod body.

3. The anchoring structure for preventing roadway floor heave according to claim 2, characterized in that, The clamping part includes a tray (9) and a nut (8), the nut (8) is threaded with the rod body, and the tray (9) is fixed to the rod body by the nut (8); The crushed stone cushion layer (3), the anchor net (10) and the steel strip (11) are sandwiched between the two trays (9).

4. The anchoring structure for preventing roadway floor heave according to claim 3, characterized in that, A precast steel mold (13) is also provided, located at the bottom end of the bottom plate anchor rod; The precast steel mold (13) is set on the surface of the weak rock layer (2) below the crushed stone cushion layer (3). The precast steel mold (13) has a through hole in the middle that matches the nut (8) so that the nut (8) and the precast steel mold (13) are radially limited. One end of the nut (8) has an edge that is longitudinally limited to the precast steel mold (13). After the nut (8) and the tray (9) are placed into the precast steel mold (13) in sequence, the bottom end of the rod is passed through the tray (9) and tightened with the nut (8) so that the bottom end of the rod passes through the precast steel mold (13) and enters the weak rock layer (2).

5. An anchoring structure for preventing roadway floor heave according to claim 3, characterized in that, It also includes a torque wrench (7). After the nut (8) is threaded with the top of the rod and squeezes the tray (9), the anchor net (10) and the steel strip (11), the torque wrench (7) is used to rotate the nut (8) to apply a preload until the torque wrench (7) reaches the preset torque.

6. An anchoring structure for preventing roadway floor heave according to claim 1, characterized in that, The side anchor rod is fixed to the rock strata by anchoring agent (12).

7. A construction method for an anchoring structure for preventing roadway floor heave, used in the construction of an anchoring structure for preventing roadway floor heave as described in any one of claims 1-6, characterized in that, Includes the following steps: Obtain the design depth of the crushed stone cushion layer (3) and the design spacing between the multiple bottom plate anchors; The designated area of ​​the weak rock layer (2) is excavated to form a filling area; The plurality of the base plate anchors are fixed within the filling area; The crushed stone cushion layer (3) is formed by laying crushed stone in the filling area. Drill holes in both sides of the tunnel to fix the side anchor bolts; The anchor mesh (10) and the steel strip (11) are laid on the surface of the crushed stone cushion layer (3), and the anchor mesh (10) and the steel strip (11) are fixed to the top of the multiple bottom plate anchors and one end of the side anchors fixed below the roadway sidewall; Preload is applied to the crushed stone cushion layer (3).

8. A construction method for an anchoring structure for preventing roadway floor heave according to claim 7, characterized in that, The method for obtaining the design depth of the crushed stone cushion layer (3) includes the following steps: Obtain the depth of the plastic zone in the tunnel; Set an excavation safety factor; The design depth of the crushed stone cushion layer (3) is obtained based on the functional relationship between the design depth of the crushed stone cushion layer (3), the depth of the plastic zone of the roadway, and the excavation safety factor.

9. A construction method for an anchoring structure for preventing roadway floor heave according to claim 7, characterized in that, The method for obtaining the design spacing of multiple base plate anchor bolts includes the following steps: Obtain the resistance stress value; Obtain the design bearing capacity value of a single anchor bolt in the base plate; The design spacing is obtained based on the functional relationship between the design spacing, the design bearing capacity of a single root, and the resistance stress value.

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