A method for controlling plastic large deformation of small-clearance jointed surrounding rock

Abstract

The application discloses a small-clearance jointed surrounding rock plastic large deformation control method, which comprises the following steps: selecting a typical jointed surrounding rock area of a small-clearance jointed surrounding rock tunnel; constructing a negative Poisson's ratio anchor cable and truss combined support numerical simulation model according to the typical jointed surrounding rock area; obtaining an optimal deformation control scheme based on the numerical simulation model; and implementing the optimal deformation control scheme to control the deformation of key parts of the tunnel. The negative Poisson's ratio anchor cable and truss combined support method with super support effect is used, on the basis of implementing the truss support in a large range of the small-clearance jointed tunnel surrounding rock, the negative Poisson's ratio anchor cable with super support force is applied to the key parts, so that the effective deformation control is realized, and a new method for the jointed surrounding rock plastic flow large deformation control is provided.

Description

Technical Field

[0001] This invention belongs to the field of tunnel technology, and in particular relates to a method for controlling large plastic deformation of physicochemical surrounding rock with small clearance joints. Background Technology

[0002] The active tectonic activity in the southwestern region has resulted in numerous fault fracture zones and jointed rock masses, posing significant obstacles to tunnel construction. Furthermore, many twin-track tunnels are designed with small clearances due to practical constraints. However, the mutual interference in these small-clearance tunnels is more severe than in conventionally designed tunnels. Therefore, traditional support methods are insufficient to control the large plastic deformation of jointed surrounding rock in small-clearance tunnels, severely hindering the region's modernization process. Thus, research on the plastic failure characteristics and control of jointed surrounding rock in small-clearance tunnels is of significant practical importance. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention proposes a method for controlling large plastic deformation in jointed physicochemical surrounding rock with small clearance joints. This method utilizes a combined support approach of negative Poisson's ratio anchor cables and trusses, which provides exceptional support effects. Based on extensive truss support in the jointed physicochemical tunnel surrounding rock with small clearance joints, negative Poisson's ratio anchor cables with exceptional support forces are applied to key locations, thereby achieving effective deformation control and providing a novel approach for controlling large plastic deformation in jointed surrounding rock.

[0004] To achieve the above objectives, the present invention provides a method for controlling large plastic deformation of physicochemically treated surrounding rocks with small net spacing, comprising:

[0005] Typical jointed rock areas were selected for tunnels with small clearance jointed rock.

[0006] Based on the typical jointed surrounding rock area, a numerical simulation model of negative Poisson's ratio anchor cable and truss combined support is constructed;

[0007] Based on the numerical simulation model, the optimal deformation control scheme is obtained;

[0008] The optimal deformation control scheme is implemented to control the deformation of key parts of the tunnel.

[0009] Optionally, before selecting a typical jointed rock region for a small-clearance jointed rock tunnel, the following may also be included:

[0010] Determine whether the tunnel is a small-clearance joint physicochemical surrounding rock tunnel.

[0011] Optionally, determining whether a tunnel is a small-clearance joint physicochemical surrounding rock tunnel includes:

[0012] Determine whether the number of joints in the jointed surrounding rock has reached the preset number of joints;

[0013] If the preset number of joints is reached, it is a small-clearance jointed surrounding rock tunnel;

[0014] Otherwise, it is not a tunnel with small clearance joints and physicochemical surrounding rock.

[0015] Optionally, the typical jointed surrounding rock regions selected include:

[0016] Obtain the preset characteristics of the jointed surrounding rock region of the small-clearance jointed surrounding rock tunnel;

[0017] Based on the preset characteristics of the jointed surrounding rock region, the typical jointed surrounding rock region is selected.

[0018] Optionally, the preset characteristic jointed surrounding rock region includes:

[0019] Ordinary deformation zone, fault fracture zone, fault fracture zone, water-rich fault fracture zone.

[0020] Optionally, based on the preset characteristics of the jointed surrounding rock region, the typical jointed surrounding rock region selected includes:

[0021] The typical jointed rock surrounding area is selected from the preset characteristic jointed rock surrounding area, which can reflect the large deformation of plastic flow in jointed soft rock or the large deformation of flexural compression of mudstone slab structure driven by engineering force.

[0022] Optionally, constructing a numerical simulation model for the combined support of negative Poisson's ratio anchor cables and trusses includes:

[0023] Construct a numerical simulation model of the tunnel surrounding rock foundation;

[0024] Based on the load loading methods and principles, a deviatoric stress load model is constructed.

[0025] Based on the numerical simulation model and the deviatoric stress load model, a combined support system of negative Poisson's ratio anchor cables and trusses is implemented.

[0026] Optionally, obtaining the optimal deformation control scheme includes:

[0027] The numerical simulation model was debugged and optimized, and the optimal parameters were designed to obtain the best combined support scheme.

[0028] Based on the optimal combined support scheme, the optimal deformation control scheme is obtained through numerical simulation calculation.

[0029] Compared with the prior art, the present invention has the following advantages and technical effects:

[0030] 1) This invention is based on the method for controlling large plastic deformation of physicochemical surrounding rock with small clearance joints. The combined support method of negative Poisson's ratio anchor cable and truss can maintain the stability of the surrounding rock of the tunnel and achieve the effect of uniformly strengthening the tunnel.

[0031] 2) This invention is based on the method of controlling large plastic deformation of physicochemical surrounding rock with small clearance joint. Compared with traditional support materials, negative Poisson's ratio anchor cable has energy absorption characteristics, which can release the deformation energy of the surrounding rock and maintain a high preload to control the stability of the surrounding rock. It has high bearing capacity and deformability.

[0032] 3) This invention is based on the method for controlling large plastic deformation of physicochemical surrounding rock with small clearance joints and the support scheme design based on PFC-FLAC coupled simulation. It reduces the manpower and material resources of repeated trial and error for the support of physicochemical surrounding rock with small clearance joints and greatly improves economic benefits. Attached Figure Description

[0033] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0034] Figure 1 This is a flowchart illustrating the method for controlling large plastic deformation of physicochemical surrounding rock with small clearance joints according to an embodiment of the present invention.

[0035] Figure 2 This is a schematic diagram of particle displacement in the NPR anchor cable truss combined support according to an embodiment of the present invention;

[0036] Figure 3 This is a schematic diagram of the surrounding rock deformation data analysis after NPR anchor cable truss combined support according to an embodiment of the present invention. Detailed Implementation

[0037] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0039] This invention proposes a method for controlling large plastic deformation of physicochemically treated surrounding rocks with small net spacing, such as... Figure 1As shown, the steps include: Step 1: Based on the survey and design data and the on-site working conditions, and with reference to the "Specifications for Geological Survey of Highway Engineering" (JTG C20-2011) and the "Detailed Rules for Design of Highway Tunnels" (JTG / T D70-2010), determine whether it is a tunnel with small clearance joints and physicochemical surrounding rock.

[0040] Step 2: Based on the third-party settlement and the degree of plastic deformation of the surrounding rock during the excavation of the pilot tunnel, the tunnel is divided into zones with different damage characteristics, such as ordinary deformation zone, fault fracture zone, fault fracture zone, and water-rich fault fracture zone.

[0041] Step 3: Select typical tunnel sections with large plastic deformation within the significantly fractured zone. Typical jointed surrounding rock areas include the following two categories:

[0042] Category 1: Areas exhibiting large deformations due to plastic flow in jointed soft rock. Specifically, the surrounding rock at the working face is mainly composed of argillaceous slate, which is disordered due to the influence of fault fracture zones. Under the drive of engineering forces, the support structure and the surrounding rock as a whole shrink and deform.

[0043] The second category includes areas of large-scale flexural and compressive deformation of argillaceous slate structures driven by engineering forces. Specifically, the surrounding rock at the working face is relatively good, with a certain bedding dip angle, and the argillaceous slate is in a moderately weathered state. Under the action of engineering forces, the surrounding rock at the working face undergoes progressive failure along the dip angle of the rock strata.

[0044] Step 4: Construct a PFC-FLAC coupled model of the negative Poisson's ratio anchor cable and truss joint support method based on the parameters of a typical engineering section. The construction of the PFC-FLAC coupled model includes:

[0045] (1) Constructing a numerical simulation model of the tunnel foundation

[0046] The surrounding rock of the tunnel is simulated by PFC particles to simulate the granular structure of the surrounding rock in the field. The tunnel lining structure is simulated by zone elements in FLAC3D. Furthermore, the joints of the surrounding rock are grouped into thin and thick interlayers according to the dip angle using the fish language.

[0047] (2) Loading methods and principles

[0048] First, a tunnel geological model is established using PFC (Precision Flow Control). Then, a servo pressure control program is built using "Wall" elements. This involves first establishing "Wall" elements at the boundary of the study area to enclose the area. An automatic program then controls the wall's servo displacement using wall pressure as an indicator, completing processes such as surrounding rock particle pressure release and in-situ stress generation. After in-situ stress generation, a gravity field is applied, the "Wall" elements are deleted, and the boundary particle elements are rigidly fixed for stability calculations, integrating gravity with existing in-situ stress. After the in-situ stress field is generated, surrounding rock parameters are assigned, with the transformed field parameters applied to the surrounding rock particles. Following assignment, tunnel excavation and support structure application are performed, followed by equilibrium calculations. Finally, the top wall elements are deleted, and zone elements are imported to apply deviatoric stress loads.

[0049] (3) Implement combined support of negative Poisson's ratio anchors and trusses

[0050] In the model constructed using the above steps, truss elements are first added. The truss elements are simulated using beam elements in FLAC3D software. The truss model diagram is constructed using Rhino software, and then the truss point information is edited using the FILE language, assigning parameters to the strength and stiffness of the connecting plate elements. C30 concrete elements are simulated using zone elements. Then, based on the pressure characteristics displayed by the model, negative Poisson's ratio anchor cables are installed. If there is severe eccentric pressure on the left and right sides of the tunnel, an asymmetric method can be used to install negative Poisson's ratio anchor cables.

[0051] Step 5: Repeatedly debug the support scheme in the model, complete the process optimization design, and on this basis, design the optimal parameters to determine the best combined support scheme.

[0052] Step 6: Implement the optimal scheme of the negative Poisson's ratio anchor cable and truss combined support method obtained by numerical simulation on site. This can effectively control the deformation of key parts of the tunnel and achieve the goal of uniformly strengthening the tunnel.

[0053] This invention employs a combined support method of negative Poisson's ratio anchor cables and trusses to control the large plastic deformation of jointed surrounding rock. The support target is jointed tunnel surrounding rock with small clearance. The plastic zone is divided according to the degree of large plastic deformation of the surrounding rock. Taking a typical engineering section with large plastic deformation as an example, a PFC-FLAC coupled model of the combined support method of negative Poisson's ratio anchor cables and trusses is constructed. After repeated debugging to obtain the optimal combined support scheme, the scheme is implemented on site in order to achieve the effect of controlling the large plastic flow deformation of jointed surrounding rock.

[0054] Example

[0055] The following section, using the Tabaiyi Tunnel as an example, details each step of the method in this embodiment:

[0056] Step 1: Based on the survey and design data and on-site conditions, it is known that under the influence of regional tectonic activity and weathering, three sets of dominant structural planes, including foliation planes, have formed in the rock mass. Under the cutting action of these structural planes, the argillaceous slate rock mass is highly fragmented, with 40–60 joints per unit volume per m. 3 Therefore, the surrounding rock of the Tabaiyi Tunnel is jointed soft rock. Furthermore, due to the influence of key engineering projects such as the Honghe Bridge and the Tabaiyi Bridge at the tunnel's entrance and exit locations, as well as the terrain, the Tabaiyi Tunnel adopts a small clearance design. In conclusion, the Tabaiyi Tunnel can be determined to be a tunnel with small clearance jointed surrounding rock.

[0057] Step 2: Based on the third-party settlement and the degree of plastic deformation of the surrounding rock during the excavation of the pilot tunnel, the tunnel is divided into zones with different damage characteristics, such as ordinary deformation zone, fault fracture zone, fault fracture zone, and water-rich fault fracture zone.

[0058] Step 3: Taking a typical jointed rock type I large deformation area as an example, conduct a plastic failure analysis of the surrounding rock.

[0059] Step 4: Construct a numerical simulation model of negative Poisson's ratio anchor cable and truss combined support. The truss support system uses two layers of I25b I-beams as the frame, connected radially by I20a and laterally by T-beams. C30 concrete is sprayed between the trusses. In the numerical model, 528,633 particle elements are constructed to simulate the fractured structure of deep rock mass. The truss elements are simulated using beam elements in FLAC3D software. The truss model diagram is constructed using Rhino software, and then the truss point information is edited using the FILE language, and parameters are assigned to the strength and stiffness of the connecting plate elements. The C30 concrete elements are simulated using zone elements.

[0060] Step 5: Based on the on-site in-situ stress test, the right side of the tunnel exhibits severe bias pressure. Therefore, negative Poisson's ratio anchor cables are asymmetrically arranged, and a reinforced support scheme is adopted on the right abutment of the tunnel. Finally, the in-situ stress is simulated by assigning a servo control system to the wall element using the FILE language to recreate the actual in-situ stress conditions. The calculation results are as follows: Figure 2 As shown. Figure 2 The data shows that under the NPR anchor cable and truss coupling support conditions, the large deformation of the tunnel surrounding rock is controlled at the millimeter level, and the original eccentric stress state of the surrounding rock in the shallow area also tends to be homogenized. Among them, the settlement of the right arch shoulder is reduced from 1m to 35mm, the convergence deformation of the left and right sidewalls is 40mm, and the upward deformation of the invert arch is 50mm.

[0061] Step 6: The optimal solution obtained through numerical simulation was implemented during construction. It can be seen that from the start of excavation at the tunnel face until the surrounding rock deformation stabilized, the process lasted nearly 45 days, effectively controlling the surrounding rock deformation within 250mm. Figure 3As shown, negative Poisson's ratio anchor cables are used for dense support at the most critical points, combining the thin slate layer on the right side of the tunnel into a thick slate layer, forming a "composite beam" in the anchor cable support theory. This effectively controls the deformation of critical parts and avoids the instability and failure of the surrounding rock.

[0062] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for controlling large plastic deformation of physicochemically treated surrounding rock with small clear distance joints, characterized in that, include: Typical jointed rock areas were selected for tunnels with small clearance jointed rock. The typical jointed surrounding rock regions selected include: Obtain the preset characteristics of the jointed surrounding rock region of the small-clearance jointed surrounding rock tunnel; Based on the preset characteristics of the jointed surrounding rock region, the typical jointed surrounding rock region is selected; The pre-defined characteristic jointed surrounding rock region includes: Ordinary deformation zone, fault fracture zone affected zone, fault fracture zone and water-rich fault fracture zone; Based on the preset characteristics of the jointed surrounding rock region, the typical jointed surrounding rock regions selected include: In the preset jointed surrounding rock region, the region that can reflect the large deformation of plastic flow in jointed soft rock or the region of large deformation of flexural compression of mudstone slab structure driven by engineering force is selected as the typical jointed surrounding rock region; based on the typical jointed surrounding rock region, a numerical simulation model of negative Poisson's ratio anchor cable and truss combined support is constructed. The numerical simulation model for the combined support of negative Poisson's ratio anchor cables and trusses includes: Construct a numerical simulation model of the tunnel surrounding rock foundation; Based on the load loading methods and principles, a deviatoric stress load model is constructed. Based on the numerical simulation model and the deviatoric stress load model, a combined support system of negative Poisson's ratio anchor cable and truss is implemented. Based on the numerical simulation model, the optimal deformation control scheme is obtained; The optimal deformation control scheme described above is implemented to control the deformation of key parts of the tunnel.

2. The method for controlling large plastic deformation of physicochemically treated surrounding rock with small clear distances according to claim 1, characterized in that, Before selecting typical jointed rock regions for tunnels with small clearance jointed rock, the following steps are also included: Determine whether the tunnel is a tunnel with small clearance joints and physicochemical surrounding rock.

3. The method for controlling large plastic deformation of physicochemically treated surrounding rock with small clear distances according to claim 2, characterized in that, Determining whether a tunnel is a small-clearance joint physicochemical surrounding rock tunnel includes: Determine whether the number of joints in the jointed surrounding rock has reached the preset number of joints; If the preset number of joints is reached, it is a small-clearance jointed surrounding rock tunnel; Otherwise, it is not a tunnel with small clearance joints and physicochemical surrounding rock.

4. The method for controlling large plastic deformation of physicochemically treated surrounding rock with small clear distances according to claim 1, characterized in that, Obtaining the optimal deformation control scheme includes: The numerical simulation model was debugged and optimized, and the optimal parameters were designed to obtain the best combined support scheme. Based on the optimal combined support scheme, the optimal deformation control scheme is obtained through numerical simulation calculation.

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