A self-adaptive rigidity anchor rod supporting device, a design method and an active regulation method

Abstract

This invention discloses a stiffness-adaptive anchor bolt support device, its design method, and an active control method, relating to the field of geotechnical engineering support technology. The anchor bolt support device includes a rod body, a compression tube, a restraining ring, a tray, and fasteners. The compression tube is sleeved on the rod body, with a variable diameter section on its outer wall along the axial direction. The restraining ring is sleeved outside the compression tube, and the two are interference-fitted. Fasteners are installed at one end of the rod body to apply axial clamping force to the compression tube. The rod body passes through the compression tube, and the fasteners press the compression tube against the restraining ring. Under the pull of the rod body, the compression tube can undergo axial displacement within the restraining ring. As the axial displacement increases, the change in the outer diameter of the variable diameter section gradually increases the interference fit resistance, achieving adaptive increase in support stiffness and buffering absorption of surrounding rock deformation energy, thus improving the safety and adaptability of the anchor bolt support.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering support technology, specifically to a stiffness adaptive anchor bolt support device, its design method, and its active control method. Background Technology

[0002] Rock bolt support is one of the main methods for controlling surrounding rock in underground engineering. In tunnels, mine roadways, slopes, and other projects, the surrounding rock often deforms to varying degrees after excavation, requiring rock bolts to provide support resistance and maintain its stability.

[0003] In existing rock bolt support structures, the bolts are mostly rigid members, and their support stiffness is fixed after installation, unable to adapt in real time to the dynamic process of surrounding rock deformation. In the early stages of underground engineering excavation, the surrounding rock often undergoes high-rate deformation and generates loads. Rock bolts with fixed stiffness are prone to overload fracture under these loads and lack effective buffering and energy absorption mechanisms to dissipate energy. In the later stages of deformation, the surrounding rock requires continuous restraint to control residual deformation, but fixed-stiffness rock bolts cannot provide matching support force according to the development of surrounding rock deformation, resulting in a difficulty in accurately matching the support effect with the actual needs on site.

[0004] Therefore, how to enable the anchor support structure to provide support resistance that increases with deformation through adaptive stiffness increase during the deformation process of the surrounding rock, and to effectively buffer the load and dissipate energy through the gradual resistance mechanism, so as to match the nonlinear deformation law of the surrounding rock, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a stiffness-adaptive anchor bolt support device, design method, and active control method to solve the technical problems of traditional anchor bolt support with fixed stiffness, inability to dynamically adapt to surrounding rock deformation, resulting in easy overload fracture under deformation load and insufficient constraint in the later stage of deformation. The invention achieves adaptive increase of support stiffness with surrounding rock deformation, gradual buffering and dissipation of energy, and significantly improves the safety of anchor bolt support and the stability of surrounding rock.

[0006] To achieve the above objectives, the present invention provides the following solution: A stiffness-adaptive anchor bolt support device, comprising: The rod is used for anchoring into the surrounding rock; A compression tube, which is hollow in shape, is sleeved on the rod body. The outer wall of the compression tube is provided with a variable diameter section along the axial direction, and the outer diameter of the variable diameter section changes along the axial direction. A constraint ring is fitted over the compression tube, and the compression tube and the constraint ring are in an interference fit. A tray, used to adhere tightly to the surrounding rock surface; and Fasteners, installed at one end of the rod, are used to apply axial clamping force to the compression tube; One end of the rod passes through the compression tube, and the fastener presses the compression tube against the constraint ring through the rod. The compression tube can undergo axial displacement within the constraint ring under the pull of the rod. As the axial displacement increases, the change in the outer diameter of the variable diameter section causes the interference fit resistance to gradually increase, thereby achieving an adaptive increase in support stiffness.

[0007] Furthermore, the outer diameter of the variable diameter section changes non-linearly along the axial direction, and the slope α(u) of the compression pipe satisfies the following relationship: Where α(u) is the slope of the compression pipe as a function of the surrounding rock deformation u, K(u) is the anchor bolt support stiffness requirement curve, μ is the friction coefficient between the compression pipe and the constraint ring, P is the interference fit preload, D is the initial outer diameter of the compression pipe, λ is the slope nonlinear enhancement coefficient, and u is the current surrounding rock deformation. max This represents the maximum allowable deformation of the surrounding rock.

[0008] Furthermore, both the compression tube and the constraint ring are made of 20 steel and have an anti-corrosion layer on their surfaces.

[0009] Furthermore, the fastener is a nut, and one end of the rod is provided with an external thread, the nut being screwed onto the external thread.

[0010] Furthermore, the fastener is an active adjustment device, which is used to adjust the interference fit between the compression tube and the constraint ring according to the adjustment command.

[0011] Furthermore, the active control device is an electric adjusting nut, a hydraulic clamping device, or an electric clamping device.

[0012] Furthermore, it also includes: Monitoring devices, deployed in the surrounding rock and on the rod, are used to collect real-time data on the deformation of the surrounding rock, the deformation rate, and the stress data of the rod; and The controller is connected to both the monitoring device and the active control device, and is used to send control commands to the active control device based on the feedback data from the monitoring device.

[0013] The present invention also provides a design method for a stiffness-adaptive anchor bolt support device, which employs the above-described anchor bolt support device and includes the following steps performed in sequence: Step 1: Obtain the basic geological parameters of the engineering site; Step 2: Based on the aforementioned basic geological parameters, determine the surrounding rock deformation control standard, which includes the maximum allowable deformation u of the surrounding rock. maxand the maximum allowable deformation rate v max ; Step 3: Based on the surrounding rock deformation control standard and the basic geological parameters, establish the anchor bolt support stiffness requirement curve K(u), where the anchor bolt support stiffness requirement curve K(u) represents the required stiffness of the anchor bolt as the surrounding rock deformation amount u varies. Step 4: Based on the anchor support stiffness requirement curve K(u), establish a quantitative conversion relationship between support stiffness and compression pipe slope based on the interference fit elastoplastic friction mechanical model, calculate the distribution law of the slope α(u) of the compression pipe, and process the compression pipe accordingly. Step 5: Process the compression pipe according to the distribution law of the slope α(u) of the compression pipe obtained in Step 4, and complete the assembly and installation of the device.

[0014] Furthermore, in step three, the anchor bolt support stiffness requirement curve K(u) is obtained through the following iterative method: The initial deformation of the surrounding rock u0 and the initial stiffness K0=0 are set at the time of anchor bolt installation. The stiffness K0 is then progressively calculated using the displacement increment Δu as the step size. k The required support force increment Δp for the current step k Compared with the previous stiffness K k-1 According to the formula The calculation shows that the deformation continues until it reaches the maximum allowable deformation u. max Connect all data points to obtain K(u); where the required support force increment for the current step is determined based on the surrounding rock characteristic curve; Furthermore, in step four, the distribution pattern of the slope α(u) of the compression pipe is calculated according to the following formula: Where μ is the friction coefficient between the compression tube and the constraint ring, P is the interference fit preload, D is the initial outer diameter of the compression tube, and λ is the slope nonlinear enhancement coefficient.

[0015] This invention also provides an active control method for a stiffness-adaptive anchor bolt support device, which uses the above-described anchor bolt support device and includes the following steps: The monitoring device collects real-time data on the deformation of the surrounding rock, the deformation rate, and the stress data of the rod. The collected real-time monitoring data is compared and analyzed with the surrounding rock deformation control standards to determine whether the warning threshold is exceeded. If the warning threshold is exceeded, the controller will control the active adjustment device to adjust the interference fit between the compression tube and the constraint ring, thereby changing the support stiffness; if the warning threshold is not exceeded, the current support stiffness will be maintained and monitoring will continue. The monitoring device confirms whether the adjusted support stiffness has reached the target value. If it has not, the adjustment continues, forming a closed-loop feedback. After the adjustment is completed, return to the step of collecting the deformation amount, deformation rate and stress data of the surrounding rock and the rod in real time through the monitoring device, and continue the monitoring and control cycle.

[0016] The present invention achieves the following technical effects compared to the prior art: The anchor bolt support device provided by this invention has an axially variable diameter section on the outer wall of the compression pipe, the outer diameter of which varies axially, and the compression pipe and the constraint ring are interference-fitted. When the surrounding rock deforms, the bolt body is subjected to tensile force, which pulls the compression pipe to undergo axial displacement within the constraint ring. As the axial displacement of the compression pipe increases, the change in the outer diameter of the variable diameter section causes the interference fit resistance between the compression pipe and the constraint ring to gradually increase. This mechanism enables the anchor bolt support stiffness to automatically increase with the increase of surrounding rock deformation, achieving real-time adaptation of support stiffness to surrounding rock deformation.

[0017] Meanwhile, during the initial stage of surrounding rock excavation, when high-rate deformation and load generation occur, the interference fit between the compression pipe and the constraint ring converts kinetic energy into plastic deformation energy through the radial contraction and axial displacement of the compression pipe. Furthermore, the resistance increases gradually with displacement rather than through a sudden, rigid collision, effectively buffering the load and preventing overload fracture caused by the instantaneous transfer of load to the rod. This buffering energy absorption mechanism solves the problem of overload fracture in traditional fixed-stiffness anchors under surrounding rock loads. Simultaneously, in the later stages of deformation, it provides continuous constraint force through increasing stiffness to control residual deformation of the surrounding rock, effectively improving the safety of anchor support and the stability of the surrounding rock. Moreover, both the constraint ring and the compression pipe are externally installed, resulting in a simple structure and low cost. Attached Figure Description

[0018] 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 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 these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the overall structure of the anchor bolt support device in an embodiment of the present invention; Figure 2 This is a schematic diagram of the design method of the stiffness adaptive anchor bolt support device of the present invention; Figure 3 This is a schematic diagram of the active control method of the stiffness adaptive anchor bolt support device of the present invention; The components are: 1. rod; 2. tray; 3. constraint ring; 4. compression tube; 5. fastener. Detailed Implementation

[0020] 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.

[0021] The purpose of this invention is to provide a stiffness-adaptive anchor bolt support device, design method, and active control method to solve the technical problems of traditional anchor bolt support with fixed stiffness, inability to dynamically adapt to surrounding rock deformation, resulting in easy overload fracture under load and insufficient constraint in the later stage of deformation. It achieves the effect of adaptively increasing support stiffness with surrounding rock deformation, gradual buffering and dissipation of energy, and significantly improving the safety of anchor bolt support and the stability of surrounding rock.

[0022] 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.

[0023] like Figure 1 As shown in the figure, an embodiment of the present invention provides a stiffness adaptive anchor bolt support device, including a rod body 1, a compression tube 4, a constraint ring 3, a tray 2, and fasteners 5.

[0024] Rod 1 is a slender rod made of high-strength steel bars. One end is anchored into the surrounding rock, and the other end extends out of the rock surface. The function of rod 1 is to transfer the tensile force and load generated by the deformation of the surrounding rock to the compression pipe 4, providing basic support for the anchor rod.

[0025] The compression tube 4 is a hollow tube fitted onto the rod 1 and can undergo radial shrinkage deformation. The outer wall of the compression tube 4 has a variable diameter section along the axial direction, with the outer diameter of the variable diameter section changing axially. Specifically, the outer diameter of the compression tube 4 is not a constant value in the axial direction, but changes with the axial position. The end of the compression tube 4 facing the fastener 5 has an annular end face. As a preferred embodiment, the outer wall of the compression tube 4 can adopt a tapered structure, i.e., the outer diameter gradually increases along the axial direction; or it can adopt a curved structure, i.e., the outer diameter changes along the axial direction according to a specific curved pattern.

[0026] The constraint ring 3 is a cylindrical ring structure, fitted over the compression tube 4. The compression tube 4 and the constraint ring 3 are interference-fitted, and a certain radial pressure is generated after they are assembled.

[0027] The tray 2 is set close to the surface of the surrounding rock to evenly transfer the support force of the anchor bolt to the surface of the surrounding rock.

[0028] Fastener 5 is installed at the end of rod 1 that extends out of the surrounding rock surface and is used to apply axial clamping force to compression tube 4. The end of rod 1 that extends out of the surrounding rock surface passes through compression tube 4, and fastener 5 presses compression tube 4 against constraint ring 3.

[0029] The working principle of the anchor bolt support device is as follows: After the anchor bolt is installed, the fastener 5 applies axial clamping force to the compression tube 4 through the rod body 1, so that the compression tube 4 and the constraint ring 3 maintain an interference fit. The tray 2 is in close contact with the surrounding rock surface, transferring the support force of the anchor bolt to the surrounding rock.

[0030] When the surrounding rock deforms, it exerts a compressive force on the pallet 2. This compressive force is transmitted through the pallet 2 to the constraint ring 3, then through the constraint ring 3 to the compression tube 4, and finally to the rod 1. The rod 1 is subjected to tensile force, which pulls the compression tube 4 to undergo axial displacement within the constraint ring 3. At the same time, the compression tube 4 undergoes radial contraction deformation under the radial constraint of the constraint ring 3.

[0031] As the axial displacement of the compression pipe 4 within the constraint ring 3 gradually increases, the variable-diameter section of the outer wall of the compression pipe 4 gradually enters the constraint ring 3. Since the outer diameter of the variable-diameter section changes axially, the interference fit between the variable-diameter section and the constraint ring 3 changes accordingly. When the section with the larger outer diameter enters the constraint ring 3, the interference fit increases, the radial pressure on the compression pipe 4 increases, and the friction between the compression pipe 4 and the constraint ring 3 increases accordingly. This friction constitutes an important component of the anchor bolt support stiffness; therefore, the anchor bolt support stiffness gradually increases with the increase of the axial displacement of the compression pipe 4.

[0032] In other words, when the surrounding rock deformation is small, the axial displacement of the compression pipe 4 is small, the section with the smaller outer diameter in the variable diameter section is within the constraint ring 3, the interference fit resistance is small, and the anchor provides relatively flexible support; when the surrounding rock deformation increases, the axial displacement of the compression pipe 4 increases, the section with the larger outer diameter in the variable diameter section enters the constraint ring 3, the interference fit resistance increases, and the anchor provides greater support resistance.

[0033] Therefore, the anchor bolt support stiffness can automatically increase as the surrounding rock deformation increases, realizing real-time adaptation between support stiffness and surrounding rock deformation.

[0034] Simultaneously, during the initial stage of surrounding rock excavation, when high-rate deformation and load generation occur, the axial displacement and radial contraction of the compression pipe 4 within the constraint ring 3 convert kinetic energy into plastic deformation energy. Furthermore, due to the gradual change in the outer diameter of the variable diameter section, the interference fit resistance increases gradually with the axial displacement of the compression pipe 4, rather than undergoing a rigid collision-like instantaneous change. This effectively buffers the load, preventing it from being instantly transferred to the rod 1 and causing it to break due to overload. As the axial displacement of the compression pipe 4 continues to increase, the interference fit resistance gradually increases, and the support stiffness of the anchor increases synchronously. While achieving energy buffering and dissipation, it continuously provides support resistance to the surrounding rock that increases with deformation.

[0035] As an implementable example, the outer diameter of the variable-diameter section changes non-linearly along the axial direction. Specifically, the slope α(u) of the compression pipe 4 characterizes the rate of change of the outer diameter of the variable-diameter section along the axial direction. During the deformation of the surrounding rock, the axial displacement of the compression pipe 4 is equal to the deformation u of the surrounding rock (ignoring the elastic deformation of the rod 1), therefore the slope α(u) of the compression pipe 4 is a function of the deformation u of the surrounding rock.

[0036] Where α(u) is the slope of the compression pipe 4 as a function of the surrounding rock deformation u; K(u) is the anchor bolt support stiffness requirement curve, representing the required support stiffness of the anchor bolt when the surrounding rock deformation is u; μ is the friction coefficient between the compression pipe 4 and the constraint ring 3; P is the interference fit preload, i.e., the radial pressure generated when the compression pipe 4 and the constraint ring 3 are initially assembled; D is the initial outer diameter of the compression pipe 4; λ is the slope nonlinear enhancement coefficient, used to control the magnitude of the slope increase with the surrounding rock deformation; u is the current surrounding rock deformation; u max This represents the maximum allowable deformation of the surrounding rock.

[0037] The above formula is based on the elastoplastic tribomechanical model of interference fits. The calculation of the indentation force and friction force of cylindrical interference fits is common knowledge in mechanical design; see national standard GB / T 5371—2004 "Limits and Fits: Calculation and Selection of Interference Fits". This invention creatively applies this calculation method to the specific scenario of anchor bolt compression pipe 4 slope design, establishing a quantitative conversion relationship from surrounding rock deformation requirements to the structural parameters of compression pipe 4.

[0038] Using this formula, the slope distribution law α(u) of the variable diameter section of the compression pipe 4 along the axial direction can be calculated according to the deformation control requirements of the surrounding rock and geological conditions, thereby realizing the accurate design of the compression pipe 4.

[0039] As a feasible example, both the compression tube 4 and the restraining ring 3 are made of 20 steel and have an anti-corrosion coating on their surfaces. 20 steel possesses good plasticity and toughness, enabling it to undergo stable plastic deformation when the compression tube 4 experiences radial contraction and axial displacement, thereby stably absorbing the deformation energy of the surrounding rock. The surface anti-corrosion coating (such as a galvanized layer or epoxy resin coating) effectively prevents the compression tube 4 and the restraining ring 3 from corroding in long-term underground engineering environments, ensuring the long-term stability of the friction coefficient of the interference fit surfaces.

[0040] As an example of implementation, fastener 5 is a nut, and one end of rod 1 is provided with external thread, on which the nut is screwed. Rod 1 passes through the hollow inner hole of compression tube 4, and the end of compression tube 4 facing the nut has an annular end face.

[0041] During anchor bolt installation, screw the nut into the external thread of the bolt body 1. To ensure effective transmission of the axial clamping force of the nut on the compression tube 4, the following method can be used: When the outer diameter of the nut is larger than the inner diameter of the compression tube 4, the nut directly abuts against the annular end face of the compression tube 4. When the nut is tightened, the nut directly pushes the compression tube 4 towards the constraint ring 3, so that the compression tube 4 and the constraint ring 3 maintain an interference fit, while the tray 2 is pressed tightly against the surrounding rock surface.

[0042] When the outer diameter of the nut is less than or equal to the inner diameter of the compression tube 4, an annular washer is placed between the nut and the annular end face of the compression tube 4. The outer diameter of the washer is greater than the inner diameter of the compression tube 4, so that it can overlap the annular end face; the inner diameter of the washer is greater than the outer diameter of the rod 1, so that the rod 1 can pass through. When the nut is tightened, the nut pushes the washer, and the washer then evenly transmits the axial clamping force to the annular end face of the compression tube 4.

[0043] When the deformation of the surrounding rock exceeds u max At this time, the axial displacement of the compression tube 4 is greater than its axial length, and the compression tube 4 is completely inserted into the constraint ring 3. The nut or washer directly abuts against the end face of the constraint ring 3, and the constraint ring 3 is jammed and no longer deforms. After that, the tension of the rod 1 continues to increase until it reaches the ultimate breaking force of the rod 1, and the rod 1 breaks, which is the last line of defense for the anchor rod.

[0044] After the anchor bolt is installed, when the surrounding rock deforms and the compression pipe 4 undergoes axial displacement within the constraint ring 3, the nut moves together with the rod body 1, continuously applying axial clamping force to the compression pipe 4.

[0045] As an example of implementation, fastener 5 itself is an active adjustment device. In other words, fastener 5 not only has the function of locking the anchor bolt during initial installation, but also has the function of actively adjusting the interference fit between the compression tube 4 and the constraint ring 3 according to the adjustment command during the service of the anchor bolt.

[0046] Specifically, fastener 5 is an active adjustment device, which is used to adjust the interference fit between compression tube 4 and constraint ring 3 according to the adjustment command.

[0047] The active control device can be an electric adjusting nut, a hydraulic clamping device, or an electric clamping device, which can precisely adjust the interference fit between the compression tube 4 and the constraint ring 3 to increase or decrease the stiffness of the anchor bolt. The specific driving principle and internal structure of the electric adjusting nut, the hydraulic clamping device, or the electric clamping device are conventional technical means in this field and will not be described in detail here.

[0048] As an example of an implementable solution, the bolt support system also includes monitoring devices and controllers.

[0049] The monitoring device is deployed in the surrounding rock and on rod 1 to collect real-time data on the deformation, deformation rate, and stress on rod 1. Specifically, the monitoring device may include a displacement gauge (deployed on or inside the surrounding rock to measure deformation), a strain gauge or stress gauge (attached to the surface of rod 1 to measure stress on rod 1), and a pressure sensor (placed between tray 2 and the surrounding rock to measure the rock pressure borne by tray 2). The specific selection and deployment of the monitoring device are conventional techniques in this field. Those skilled in the art can select appropriate sensor models and deploy them according to actual engineering needs, and will not be elaborated upon here.

[0050] The controller connects to both the monitoring device and the active control device, and sends control commands to the active control device based on feedback data from the monitoring device. The controller can be a standalone control unit (such as a PLC controller or a microcontroller system) or integrated into the overall control system at the engineering site. The specific selection of the controller and the programming control logic are standard techniques in this field and will not be elaborated upon here.

[0051] In practical operation, the monitoring device collects real-time data on the deformation of the surrounding rock, the deformation rate, and the stress on the anchor rod 1, and transmits the data to the controller. The controller compares and analyzes the received monitoring data with preset surrounding rock deformation control standards. When the deformation or deformation rate of the surrounding rock exceeds the warning threshold, the controller sends a control command to the active control device. The active control device responds to this command by adjusting the interference fit between the compression pipe 4 and the constraint ring 3, thereby changing the support stiffness of the anchor rod. After adjustment, the monitoring device continues to collect data and feeds it back to the controller. The controller confirms whether the adjusted support stiffness has reached the target value. If not, it continues to adjust, forming a closed-loop feedback. The controller's comparative analysis of monitoring data and threshold judgment logic are conventional techniques in this field and will not be elaborated here.

[0052] This invention also provides a design method for a stiffness-adaptive anchor bolt support device, which includes the following sequential steps: Step 1: Obtain the basic geological parameters of the engineering site.

[0053] The physical and mechanical parameters and hydrogeological conditions of the soil and rock mass in the engineering site are obtained through methods such as borehole sampling and in-situ testing. Basic geological parameters include, but are not limited to: the elastic modulus E of the surrounding rock, Poisson's ratio ν, cohesion c, and angle of internal friction. Density γ and original rock stress σ. These parameters are the basis for subsequent anchor bolt design.

[0054] Specifically, the elastic modulus E reflects the deformation stiffness of the surrounding rock and can be obtained through indoor rock mechanics tests (such as uniaxial compression tests); Poisson's ratio ν can be obtained by the ratio of transverse strain to longitudinal strain in a uniaxial compression test; cohesion c and internal friction angle... The shear strength characteristics of the surrounding rock are reflected by direct shear tests or triaxial compression tests; the original rock stress σ reflects the initial stress state of the surrounding rock and can be obtained through field testing using hydraulic fracturing or stress relief methods. The methods for obtaining these parameters are conventional techniques in this field, and specific experimental and testing procedures will not be elaborated upon here.

[0055] Step 2: Determine the deformation control standards for the surrounding rock based on the basic geological parameters.

[0056] The engineering analogy method was used to determine the surrounding rock deformation control standard: A comprehensive comparison was made between the geological conditions and project scale (tunnel diameter, burial depth, etc.) of this project and similar existing surrounding rock projects. The maximum allowable deformation and deformation rate control values ​​of existing projects were referenced to determine the surrounding rock deformation control standard. The surrounding rock deformation control standard includes the maximum allowable deformation u. max and the maximum allowable deformation rate v max The engineering analogy method is a conventional design method in this field. Those skilled in the art can determine the deformation control standard applicable to this project based on existing similar engineering cases. The specific analogy process and the basis for the values ​​will not be elaborated here.

[0057] For example, in soft rock tunnel engineering, if the surrounding rock grade is IV or V, based on experience from similar projects, the maximum allowable deformation u of the surrounding rock is... max It can be set to 100mm, and the maximum allowable deformation rate v max It can be set to 2mm / d.

[0058] Step 3: Based on the surrounding rock deformation control standards and basic geological parameters, establish the anchor bolt support stiffness requirement curve K(u).

[0059] The anchor bolt support stiffness requirement curve K(u) represents the required anchor bolt stiffness as the surrounding rock deformation u varies. This curve is established based on the theory of rock-anchor bolt cooperative bearing, which establishes a nonlinear relationship between anchor bolt stiffness and surrounding rock deformation and rock mass physical parameters.

[0060] Specifically, by substituting different surrounding rock deformation amounts u (0~u max ), combined with the initial original rock stress P0, cohesion c, and internal friction angle of the surrounding rock. Based on parameters such as these, the anchor support stiffness requirement curve K(u) matching the nonlinear deformation of the surrounding rock is calculated.

[0061] The anchor bolt support stiffness requirement curve K(u) is calculated using the following iterative method: Assuming the rock mass obeys the Mohr-Coulomb yield criterion and the unassociated flow law, the total deformation of the tunnel wall is... u With the radius of the plastic zone R p The following nonlinear relationship exists (formation response curve equation): Rock mass physical parameters: The meanings of the parameters in the formation response curve equation are as follows: P0 is the initial in-situ stress of the surrounding rock, and c is the cohesion of the surrounding rock. R0 is the internal friction angle of the surrounding rock; R0 is the equivalent excavation radius of the tunnel; u is the radial deformation of the tunnel wall; P i The radial support resistance provided to the support system; the shear modulus G is calculated from the elastic modulus E and Poisson's ratio ν according to G=E / [2(1+ν)]. max U is the maximum allowable deformation of the surrounding rock, and u0 is the initial deformation of the surrounding rock that has occurred when the anchor bolt is installed with a lag.

[0062] Among them, R p The radius of the plastic zone can be calculated using the following formula: Determine the initial deformation u0 of the surrounding rock during anchor bolt installation based on the spatial effect at the working face or the timing of construction. Select a sufficiently small radial displacement increment Δu as the iteration step size. Set the initial step k=0: u0 is known, and the initial support force p is... req,0 =0 (i.e., radial support force requirement in step 0), initial stiffness K0.

[0063] Then calculate the support force requirement of the surrounding rock in the current step. Proceed to the k-th calculation step, the current deformation is updated as follows: will u k Substituting the equation of the formation response curve, the radial support force p required by the surrounding rock under this deformation is calculated. req,k Therefore, the required increase in support force for the current step is obtained: The increment of support force provided by the support system within the Δu deformation range is equal to the average of the initial and final stiffnesses multiplied by the deformation increment: Due to Δp k Δu and the stiffness K from the previous step k-1 Given that all terms are known, the transient stiffness requirement that the anchor bolt must possess in the k-th step can be solved directly by rearranging the terms: Repeat the above steps, recursively calculating k=1,2,3… until the deformation u(k) reaches the maximum allowable deformation u. max . All steps (u k ,K k Connecting the data points yields an accurate adaptive stiffness demand curve K(u) for the entire process.

[0064] Step 4: Based on the anchor support stiffness requirement curve K(u), establish the quantitative conversion relationship between support stiffness and the slope of compression pipe 4 based on the interference fit elastoplastic friction mechanical model, calculate the distribution law of the slope α(u) of compression pipe 4, and process compression pipe 4 accordingly.

[0065] The distribution pattern of the slope α(u) of compression pipe 4 is calculated according to the following formula: Based on elastoplastic friction mechanics and nonlinear evolution constitutive models, a differential integral relationship between axial support stiffness and normal contact force is established. Assume that the anchor bolt undergoes axial displacement... u At that time, the total pull-out resistance provided to the surrounding rock is F (u). This resistance is mainly caused by the Coulomb friction force F between the compression tube 4 and the constraint ring 3. f (u) and the axial component F of the work done by the radial extrusion of the reducing pipe. w (u) Composition. Since the slope α(u) of the reducing pipe is relatively small in actual engineering, to simplify the system nonlinearity, the total axial resistance is equivalent to the frictional resistance dominated by the dynamic normal force: Where N(u) is the total radial interference contact pressure between the compression pipe 4 and the constraint ring 3 when the displacement is u. According to the definition of anchor support stiffness (i.e., the derivative of pull-out resistance with respect to displacement), the equivalent stiffness K(u) of the system can be expressed as: As rod 1 undergoes a displacement increment du under the influence of the surrounding rock, due to the slope α(u) of the outer wall of compression pipe 4, its outer diameter is forcibly squeezed into constraint ring 3, resulting in a unilateral radial displacement (i.e., interference increment) dr. The geometric relationship is as follows: Under the current deformation state, the dynamic radial compressive stiffness of the coupling system between constraint ring 3 and compression tube 4 is K. r (u). The newly added normal contact force increment dN(u) is: Dividing both sides by du, we obtain the evolution rate of normal pressure with respect to displacement: Substituting this equation into the stiffness formula, we obtain the bridging equation between the macroscopic equivalent stiffness K(u) and the microscopic geometric slope α(u): After rearranging the terms, we can obtain the basic formula for calculating the slope: In practical interference fit systems, as the extruded volume increases, the constraint ring 3 and the compression tube 4 themselves will undergo elastoplastic yielding. This means that the radial compressive stiffness of the system is not a constant value, but rather evolves nonlinearly with the increase of deformation u.

[0066] Define the initial characteristic radial stiffness of the system when it is undeformed (u=0) as: Where P is the preload of the interference fit, u max / D is a dimensionless geometric coefficient characterizing the tube-loop interaction. A nonlinear enhancement coefficient is introduced. Damage / Evolution Factors The dynamic radial stiffness of the system Represented as: Mechanical interpretation: When u→u max At that time, K r (u) approaches 0 (material yields or the pressure space is exhausted). At this point, in order to meet the resistance K(u) required by the surrounding rock, the resistance must be forcibly increased by drastically increasing the outer wall slope α of the compression pipe 4, thereby achieving the "hardening lock-up" function at the end of the deformation period.

[0067] Dynamic radial stiffness K r (u) Substitute into the basic formula for calculating the slope: Reorganize and simplify the right side of the equation using fractions: Taking the arctangent function of both sides of the equation yields the final geometric governing equation for CNC machining or mold outer wall design: The methods for determining the preload P and the nonlinear enhancement coefficient λ in the above geometric control equations are as follows.

[0068] 1. Method for determining preload P P represents the displacement before deformation occurred. At that time, the initial normal contact stress generated between the outer wall of the compression pipe 4 and the inner wall of the constraint ring 3 due to the initial dimensional interference (interference) determines the "starting resistance" of the anchor bolt's adaptive pressure relief.

[0069] The value of P can be precisely defined using Lamé's formula in mechanical design.

[0070] Let the initial state have an outer radius of r for the compression tube 4 and an inner radius of r for the constraint ring 3, with a design value of Δr for the unilateral radial interference between them. According to the elasticity solution of a thick-walled cylinder, the formula for calculating the preload P is: Where Δr is the radial interference during design and processing, r is the initial outer radius of the compression tube 4 (i.e., D / 2), R1 is the inner radius of the compression tube 4, R2 is the outer radius of the constraint ring 3, E1 and ν1 are the elastic modulus and Poisson's ratio of the material of the compression tube 4, and E2 and ν2 are the elastic modulus and Poisson's ratio of the material of the constraint ring 3.

[0071] Technicians can pre-set the initial starting resistance (initial constant resistance) required for the anchor bolt, calculate the required preload P, and then derive the required dimensional interference Δr between the compression tube 4 and the constraint ring 3 during factory processing.

[0072] 2. Method for determining the nonlinear enhancement coefficient λ λ is a dimensionless control parameter that determines the deformation as it approaches the maximum allowable deformation u. max At that time, the degree of "hardening and locking" of the anchor rod stiffness (curvature).

[0073] If λ is small (e.g., 0.5 < λ < 1), the stiffness increases relatively slowly, which is suitable for soft rocks with creep deformation as the main process; if λ is large (e.g., λ ≥ 2), the stiffness increases exponentially and rapidly at the end of the deformation period, which is suitable for brittle rock masses with high ground stress and a tendency for sudden large deformation or rockburst.

[0074] The control system or technicians obtain the characteristic curve (i.e., the K(u) demand curve) of the current surrounding rock based on on-site sampling. Determining λ is essentially a least-squares curve fitting process. The target stiffness demand curve is set as K... target (u), the actual stiffness curve provided by the device is K. actual (u,λ). By finding a value that makes both equal throughout the entire deformation interval [0,u] max The value of λ that minimizes the sum of squared internal errors: To facilitate application by construction personnel, deformation can be used to reach a certain key node (such as the inflection point where the plastic zone rapidly expands, denoted as u). c The required ultimate stiffness K at this time c To deduce λ from the known point (u) c， K c Substituting into the previously derived formula, we get: Among them, u c K represents the critical deformation required for accelerated rheological yielding of the surrounding rock. c The required resistance stiffness of the surrounding rock at this critical point. α c For this node, the compression pipe 4 is constrained to the limit of the machining slope (the maximum slope limited by the machine tool process).

[0075] The slope nonlinear enhancement coefficient λ is not a fixed constant, but a dynamic parameter generated by the control terminal through an optimization fitting algorithm based on the pre-acquired surrounding rock strain softening characteristic curve, with the goal of minimizing the stiffness error between the actual support stiffness and the theoretical requirement. Under normal operating conditions, the value of λ is defined as between 1.2 and 3.5 to ensure that the device has reliable self-locking anti-erosion capability at the end of the pressure relief period.

[0076] After determining the preload P and the nonlinear enhancement coefficient λ, the distribution law of the slope α(u) of the compression pipe 4 can be calculated according to the above geometric control equation: First, input the support stiffness demand curve K(u) obtained in step three; then input the parameters μ, P, D, and λ; calculate the slope α(u) of the compression pipe 4 corresponding to each deformation u point by point; draw the slope curve to obtain the nonlinear slope distribution law of the variable diameter section of the compression pipe 4.

[0077] Step 5: Process the compression pipe 4 according to the distribution law of the slope α(u) of the compression pipe 4 obtained in Step 4, and complete the assembly and installation of the anchor bolt support device.

[0078] According to the calculated slope distribution law α(u), the outer wall of the compression pipe 4 is machined to form a variable diameter section. Then, the compression pipe 4 is sleeved on the rod body 1, the constraint ring 3 is sleeved on the outside of the compression pipe 4, the tray 2 and fasteners 5 are installed, and the assembly and on-site installation of the anchor bolt support device are completed.

[0079] This invention also provides an active control method for a stiffness-adaptive anchor bolt support device, employing the aforementioned anchor bolt support device including a monitoring device and a controller, comprising the following steps: Step 1: Collect monitoring data in real time.

[0080] The monitoring device collects real-time data on the deformation of the surrounding rock, the deformation rate, and the stress on rod 1. The monitoring data is continuously collected at a certain sampling frequency (such as once per second or once per minute) and uploaded to the controller in real time.

[0081] Step 2: Data analysis and early warning determination.

[0082] The controller compares and analyzes the collected real-time monitoring data with the surrounding rock deformation control standards to determine whether the warning threshold has been exceeded. The warning threshold can be set to the maximum allowable deformation u of the surrounding rock. max A certain percentage (e.g., 80%) can also be set according to the deformation rate (e.g., if the deformation rate continuously exceeds v). max If the current support stiffness is not exceeded, the current support stiffness will be maintained and monitoring will continue.

[0083] Step 3: Trigger proactive regulation.

[0084] If the monitoring data exceeds the warning threshold, the controller will control the active control device to adjust the interference fit between the compression pipe 4 and the constraint ring 3, thereby changing the support stiffness.

[0085] Specifically, the controller calculates the required stiffness adjustment based on the difference between the current surrounding rock deformation and the design stiffness requirement curve K(u), and then sends an adjustment command to the active control device. The active control device (such as an electric adjusting nut, hydraulic clamping device, or electric clamping device) responds to this command by driving the fastener 5 to rotate or move axially, changing the axial clamping force on the compression tube 4, thereby adjusting the interference fit between the compression tube 4 and the constraint ring 3.

[0086] Step 4: Closed-loop feedback confirmation.

[0087] The monitoring device confirms whether the adjusted support stiffness has reached the target value. Specifically, the monitoring device continues to collect data on surrounding rock deformation and the stress data of rod 1. The controller calculates the actual support stiffness achieved based on the feedback data and compares it with the target stiffness. If the target value is not reached, adjustments continue, forming a closed-loop feedback. This closed-loop feedback process can be repeated multiple times until the support stiffness reaches the target value or the deviation is within the allowable range.

[0088] Step 5: Continuous monitoring and cyclical regulation.

[0089] After the adjustment is completed, return to step one and continue the monitoring and control cycle.

[0090] Through the above steps, a fully closed-loop active control system of "monitoring → judgment → regulation → feedback → re-monitoring" is formed, which ensures that the stiffness of the anchor bolt support is always precisely matched with the nonlinear law of the surrounding rock deformation.

[0091] The structures, connections, or operation methods not described in detail in this invention can be superimposed on each other without interference, and these adaptive changes all fall within the protection scope of this invention.

[0092] It should be noted that, for those skilled in the art, it is obvious that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0093] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A stiffness-adaptive anchor bolt support device, characterized in that, include: The rod is used for anchoring into the surrounding rock; A compression tube, which is hollow in shape, is sleeved on the rod body. The outer wall of the compression tube is provided with a variable diameter section along the axial direction, and the outer diameter of the variable diameter section changes along the axial direction. A constraint ring is fitted over the compression tube, and the compression tube and the constraint ring are in an interference fit. A tray is used to adhere tightly to the surface of the surrounding rock. as well as Fasteners, installed at one end of the rod, are used to apply axial clamping force to the compression tube; One end of the rod passes through the compression tube, and the fastener presses the compression tube against the constraint ring through the rod. The compression tube can undergo axial displacement within the constraint ring under the pull of the rod. As the axial displacement increases, the change in the outer diameter of the variable diameter section causes the interference fit resistance to gradually increase, thereby achieving an adaptive increase in support stiffness.

2. The anchor bolt support device according to claim 1, characterized in that, The outer diameter of the variable diameter section changes non-linearly along the axial direction, and the slope α(u) of the compression pipe satisfies the following relationship: Where α(u) is the slope of the compression pipe as a function of the surrounding rock deformation u, K(u) is the anchor bolt support stiffness requirement curve, μ is the friction coefficient between the compression pipe and the constraint ring, P is the interference fit preload, D is the initial outer diameter of the compression pipe, λ is the slope nonlinear enhancement coefficient, and u is the current surrounding rock deformation. max This represents the maximum allowable deformation of the surrounding rock.

3. The anchor bolt support device according to claim 1, characterized in that, Both the compression tube and the constraint ring are made of 20 steel and have an anti-corrosion layer on their surface.

4. The anchor bolt support device according to claim 1, characterized in that, The fastener is a nut, and one end of the rod is provided with an external thread, and the nut is screwed onto the external thread.

5. The anchor bolt support device according to claim 1, characterized in that, The fastener is an active adjustment device, which is used to adjust the interference fit between the compression tube and the constraint ring according to the adjustment command.

6. The anchor bolt support device according to claim 5, characterized in that, The active control device is an electric adjusting nut, a hydraulic clamping device, or an electric clamping device.

7. The anchor bolt support device according to claim 5, characterized in that, Also includes: A monitoring device is installed in the surrounding rock and on the rod to collect real-time data on the deformation of the surrounding rock, the deformation rate, and the force data of the rod. as well as The controller is connected to both the monitoring device and the active control device, and is used to send control commands to the active control device based on the feedback data from the monitoring device.

8. A design method for a stiffness-adaptive anchor bolt support device, characterized in that, The anchor bolt support device according to any one of claims 1 to 4 comprises the following steps performed in sequence: Step 1: Obtain the basic geological parameters of the engineering site; Step 2: Based on the aforementioned basic geological parameters, determine the surrounding rock deformation control standard, which includes the maximum allowable deformation u of the surrounding rock. max and the maximum allowable deformation rate v max ; Step 3: Based on the surrounding rock deformation control standard and the basic geological parameters, establish the anchor bolt support stiffness requirement curve K(u), where the anchor bolt support stiffness requirement curve K(u) represents the required stiffness of the anchor bolt as the surrounding rock deformation amount u varies. Step 4: Based on the anchor support stiffness requirement curve K(u), establish a quantitative conversion relationship between support stiffness and compression pipe slope based on the interference fit elastoplastic friction mechanical model, calculate the distribution law of the slope α(u) of the compression pipe, and process the compression pipe accordingly. Step 5: Process the compression pipe according to the distribution law of the slope α(u) of the compression pipe obtained in Step 4, and complete the assembly and installation of the device.

9. The design method according to claim 8, characterized in that, In step three, the anchor bolt support stiffness requirement curve K(u) is obtained through the following iterative method: The initial deformation of the surrounding rock, u0, and the initial stiffness K0 = 0 are set at the time of anchor bolt installation. The stiffness K0 is then iteratively calculated step by step with the displacement increment Δu as the step size. k The required support force increment Δp for the current step k Compared with the previous stiffness K k-1 According to the formula The calculation shows that the deformation continues until it reaches the maximum allowable deformation u. max Connect all data points to obtain K(u); where the required support force increment for the current step is determined based on the surrounding rock characteristic curve; Furthermore, in step four, the distribution pattern of the slope α(u) of the compression pipe is calculated according to the following formula: Where μ is the friction coefficient between the compression tube and the constraint ring, P is the interference fit preload, D is the initial outer diameter of the compression tube, λ is the slope nonlinear enhancement coefficient, and u is the current surrounding rock deformation.

10. An active control method for a stiffness-adaptive anchor bolt support device, characterized in that, The use of the anchor bolt support device according to claim 7 includes the following steps: The monitoring device collects real-time data on the deformation of the surrounding rock, the deformation rate, and the stress data of the rod. The collected real-time monitoring data is compared and analyzed with the surrounding rock deformation control standards to determine whether the warning threshold is exceeded. If the warning threshold is exceeded, the controller will control the active adjustment device to adjust the interference fit between the compression tube and the constraint ring, thereby changing the support stiffness; if the warning threshold is not exceeded, the current support stiffness will be maintained and monitoring will continue. The monitoring device confirms whether the adjusted support stiffness has reached the target value. If it has not, the adjustment continues, forming a closed-loop feedback. After the adjustment is completed, return to the step of collecting the deformation amount, deformation rate and stress data of the surrounding rock and the rod in real time through the monitoring device, and continue the monitoring and control cycle.

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