Anchorage anti-pulling and anti-pressure test method and system

Abstract

This invention discloses a method and system for testing the pull-out and compressive strength of anchor bolts, comprising: acquiring target test parameters and real-time acquisition of internal pressure data of a first expansion mechanism; acquiring pressure deviation values ​​based on the target test parameters and internal pressure data, generating pressure compensation commands based on the pressure deviation values, and performing pressure compensation on the first expansion mechanism based on the pressure compensation commands; extracting axial strain data and displacement data of the test anchor bolt after pressure compensation; calculating the axial force and side friction resistance of the test anchor bolt at different depths based on the axial strain data, and combining the side friction resistance with the displacement data to generate a load-bearing assessment result for the test anchor bolt. Compared with the prior art, this invention can achieve stable control of the confining pressure boundary during the test, improve the pressure control response speed, dynamically simulate geological deformation characteristics, and acquire side friction resistance data at different positions of the anchor bolt in real time.

Description

Technical Field

[0001] This invention relates to the field of mechanical testing and automated inspection technology, and more specifically, to a method and system for testing the pull-out and compressive strength of anchor bolts. Background Technology

[0002] In the field of mechanical testing for geotechnical and civil engineering, with the increasing demands for geological disaster prediction, tunnel support, and underground engineering safety, the in-situ or indoor model test characteristics of anchor bolts and pile foundations, as core tensile and compressive support components, have received considerable attention. By applying upward or downward compressive loads to test anchor bolts and accurately measuring their deformation, load transfer characteristics, and failure mechanisms during the loading process, crucial experimental references can be provided for the design and safety assessment of anchored foundations in practical engineering. In particular, indoor model tests, using standard sand and other simulated geological materials to reproduce foundation conditions in specific model trenches and acquiring anchor bolt stress characteristics using multi-point data acquisition systems, have become a mainstream and effective method for studying the pile-soil interaction mechanism.

[0003] In the prior art, Chinese invention patent document CN104198306B discloses a dynamic pull-out test device and method under impact active confining pressure. This method uses a mechanical lever mechanism or fluid pressure mechanism to apply active confining pressure to the sidewall of the specimen and performs load testing and evaluation on the components within the sample. However, the prior art still suffers from technical problems such as unstable test confining pressure, slow pressure control response, inability to dynamically simulate geological deformation characteristics, and inability to calculate the side friction resistance at various points on the anchor bolt in real time.

[0004] Therefore, how to provide a method and system for testing the pull-out and compressive strength of anchor bolts, which can achieve stable control of the confining pressure boundary during the test, improve the pressure control response speed, dynamically simulate geological deformation characteristics, and obtain side friction data of different positions of the anchor bolt in real time, has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for testing the pull-out and compressive strength of anchor bolts. This method enables stable control of the confining pressure boundary during the test, improves the pressure control response speed, dynamically simulates geological deformation characteristics, and acquires real-time data on the side friction resistance at different locations of the anchor bolt.

[0006] The first technical solution provided by this invention is as follows: This invention provides a method for testing the pull-out and compression resistance of an anchor bolt, comprising the following steps: S1 acquiring target test parameters and real-time collecting internal pressure data of the first expansion mechanism and axial strain data of the test anchor bolt; S2 acquiring pressure deviation values ​​based on the target test parameters and internal pressure data, generating pressure compensation commands based on the pressure deviation values, and performing pressure compensation on the first expansion mechanism based on the pressure compensation commands; S3 real-time monitoring of simulated geological deformation characteristics after pressure compensation, and controlling the second expansion mechanism in the corresponding orientation to perform pressure adjustment action when the simulated geological deformation characteristics meet the boundary weakening condition; S4 extracting axial strain data and displacement data of the test anchor bolt after the pressure adjustment action; S5 calculating the axial force and side friction resistance of the test anchor bolt at different depths based on the axial strain data, and combining the side friction resistance and the displacement data to generate a load-bearing assessment result of the test anchor bolt.

[0007] Furthermore, in a preferred embodiment of the present invention, when the simulated geological deformation characteristics satisfy the boundary weakening condition, the second expansion mechanism in the corresponding orientation is controlled to perform a pressure regulating action, including: The boundary weakening conditions include: loosening judgment threshold and compression judgment threshold; The simulated geological deformation characteristics are compared with the loosening and compression thresholds, respectively. When the simulated geological deformation characteristics meet the loosening judgment threshold, it is determined that local loosening has occurred, the target pressure regulating azimuth is obtained, and the second expansion mechanism corresponding to the target pressure regulating azimuth is controlled to perform pressure reduction action; When the simulated geological deformation characteristics meet the compression judgment threshold, it is determined that local compression has occurred, and the second expansion mechanism corresponding to the target pressure adjustment direction is controlled to perform a pressurization action.

[0008] Further, in a preferred embodiment of the present invention, pressure compensation of the first expansion mechanism according to the pressure compensation command includes: The tolerance range is extracted based on the target test parameters, and the tolerance range represents the critical limit of the pressure deviation of the first expansion mechanism; When the internal pressure data is lower than the lower limit of the tolerance range, the air pump is controlled to inject fluid into the first expansion mechanism. When the internal pressure data is higher than the upper limit of the tolerance range, the air pump is controlled to discharge fluid from the first expansion mechanism.

[0009] Furthermore, in a preferred embodiment of the present invention, the method further includes a feedforward control step for the first expansion mechanism, specifically comprising: Historical axial strain data is collected, and the time derivative at adjacent time nodes is calculated based on the historical axial strain data to obtain the strain mutation rate. When the absolute value of the strain mutation rate is greater than the preset critical strain rate for boundary damage, the positive and negative sign features of the strain mutation rate are extracted. If the strain mutation rate is negative, it is determined that the soil around the test anchor is undergoing shear expansion and compression, and the air pump is controlled to perform a pre-depressurization action. If the strain mutation rate is positive, it is determined that the soil around the test anchor is shearing and voiding, and the air pump is controlled to perform a pre-inflation action.

[0010] Furthermore, in a preferred embodiment of the present invention, obtaining the critical strain rate for boundary damage includes: Obtain stress-strain curves of similar simulated geological materials under standard shear tests; Taking the first derivative of the stress-strain curve yields the first-order slope function; When the first-order slope function first drops to a preset proportion of the initial maximum slope, the current position is determined as an inflection point; Extract the corresponding time node of the inflection point, and calculate the time derivative of the axial strain data at the corresponding time node to obtain the critical strain rate of boundary damage.

[0011] Furthermore, in a preferred embodiment of the present invention, the extraction of axial strain data and displacement data of the pressure-compensated test anchor includes: The ultimate bearing capacity of the test anchor is collected, and the ultimate bearing capacity is divided into several loading levels according to the ratio; The loading levels are applied in stages, and the displacement data of the test anchor is continuously monitored within the period of each loading level. When the change in displacement data per unit time is less than a preset stability threshold and the internal pressure data is within the tolerance range, it is determined that the current loading level has reached a stable state, and the current axial strain data and displacement data are obtained.

[0012] Further, in a preferred embodiment of the present invention, calculating the axial force and side friction of the test anchor at different depths based on the axial strain data includes: Obtain the elastic modulus and cross-sectional area of ​​the test anchor rod; Obtain the sampling point information along the axial direction on the test anchor rod, and obtain the corresponding axial strain data based on the sampling point information; The axial force of the cross section is calculated based on the elastic modulus, the test cross-sectional area, and the axial strain data, using the following formula: ; in, Indicates the first i Each sampling point corresponds to the axial strain data. EIndicates the elastic modulus. A This represents the area of ​​the test cross section. Indicates the first i Axial force at each sampling point; Obtain the diameter of the test anchor and the distance between adjacent sampling points, and calculate the side friction resistance based on the anchor diameter and the distance between adjacent sampling points, using the following formula: ; in, This indicates the side friction resistance. Indicates the adjacent spacing, This indicates the diameter of the anchor rod.

[0013] The present invention provides a second technical solution as follows: The present invention also provides an anchor bolt pull-out and compression test system, the system being used to perform the anchor bolt pull-out and compression test method described in any one of the above, comprising: Box; The bracket is disposed on the upper surface of the housing; The crossbeam has one end movably mounted on the bracket, and the other end is a free end for placing the load. Connectors are installed on the main body of the crossbeam; The test anchor rod is connected to the crossbeam via the connector, and the test anchor rod is located inside the box. The first expansion mechanism is located inside the box and covers the periphery of the simulated geological material. The top surface of the first expansion mechanism is provided with an air inlet and outlet pipe. The second expansion mechanism is installed on the inner wall of the box and is used to adjust the local boundary constraint state of the simulated geological material. An air pump, connected to the first expansion mechanism, is used to input or discharge fluid into the first expansion mechanism; A central controller, electrically connected to the air pump, is used to control the air pump to perform fluid input or discharge actions.

[0014] Furthermore, in a preferred embodiment of the present invention, it further includes: A pressure detection device is disposed on the first expansion mechanism and is used to detect the internal pressure of the first expansion mechanism; The pressure detection device is electrically connected to the central controller. Furthermore, in a preferred embodiment of the present invention, it further includes: The strain sensors are arranged at intervals along the axial direction, and the strain sensors located on the same cross section are symmetrically distributed circumferentially. The strain sensor is used to collect axial strain data of the test anchor rod when it is loaded at different depths and in different orientations. The strain sensor is electrically connected to the central controller.

[0015] The anchor bolt pull-out and compressive strength test method and system of the present invention have the following advantages over the prior art: (1) By collecting the internal pressure data of the first expansion mechanism in real time, and using the pressure deviation value between the target test parameters and the internal pressure data to generate a pressure compensation command in real time, the air pump is driven to inject or discharge fluid into the first expansion mechanism, so as to maintain the internal pressure of the first expansion mechanism within the tolerance range of the target parameters, prevent the pressure of the first expansion mechanism from rising or falling due to soil deformation, and ensure the constant lateral confining pressure.

[0016] (2) By introducing a command response based on the pressure deviation value into the pressure regulating circuit of the first expansion mechanism, the inflation and depressurization actions of the air pump are directly related to the changes in the confining pressure, which shortens the adjustment delay of the control valve to the pressure change in the test chamber, avoids the loosening of the surrounding soil caused by the pressure regulation lag, and improves the pressure stabilization speed in the high load stage.

[0017] (3) By monitoring the simulated geological deformation characteristics after pressure compensation in real time, and controlling the second expansion mechanism in the corresponding direction to perform pressure regulation when the boundary weakening condition is met, the local boundary constraint state of the simulated geological material is changed, and the dynamic simulation of simulated geological deformation characteristics such as local loosening or local compression is realized.

[0018] (4) By collecting axial strain data of the test anchor at different depths and orientations in real time, and calculating the corresponding cross-sectional axial force and side friction resistance in combination with the location of each sampling point, the deep mechanical data of the test anchor under load was obtained, and the real-time calculation and continuous monitoring of the side friction resistance at various points of the test anchor were realized. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A flowchart illustrating the steps of the anchor bolt pull-out and compression test method provided in this embodiment of the invention; Figure 2 This is a schematic diagram of the structure of the anchor pull-out and compression resistance test system provided in an embodiment of the present invention; Figure 3This is a cross-sectional view of the anchor bolt pull-out and compression test system provided in an embodiment of the present invention; Figure 4 A structural diagram of the first expansion mechanism provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the anchor pull-out and compression resistance test system provided in an embodiment of the present invention. Figure 6 The physical object of the anchor bolt pull-out and compression test system provided in the embodiments of the present invention. Figure 1 ; Figure 7 The physical object of the anchor bolt pull-out and compression test system provided in the embodiments of the present invention. Figure 2 ; Figure 8 A physical image of the test anchor provided in an embodiment of the present invention; Figure 9 This is a physical distribution diagram of the strain sensor provided in an embodiment of the present invention; Figure 10 A physical diagram of the test anchor installation and strain sensor wiring provided in an embodiment of the present invention; Figure 11 This is a field diagram showing the layout of measuring points and data acquisition for the test anchor provided in an embodiment of the present invention.

[0021] Reference numerals: 1. Box body; 2. Support frame; 3. Crossbeam; 4. Connector; 5. Test anchor; 51. Strain sensor; 6. Load; 7. First expansion mechanism; 71. Inlet and outlet pipes; 72. Pressure detection device; 8. Air pump; 9. Central controller; 10. Second expansion mechanism. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0023] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly set on the other component; when a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to the other component.

[0024] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "first", "second", "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. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" or "several" means two or more, unless otherwise explicitly specified.

[0026] It should be noted that the structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0027] like Figures 1 to 11 As shown, an embodiment of the present invention provides a method for testing the pull-out and compression resistance of an anchor bolt, comprising: S1 acquiring target test parameters and real-time collecting internal pressure data of the first expansion mechanism 7 and axial strain data of the test anchor bolt 5; S2 obtains the pressure deviation value based on the target test parameters and internal pressure data, generates a pressure compensation command based on the pressure deviation value, and performs pressure compensation on the first expansion mechanism 7 based on the pressure compensation command. S3 monitors the simulated geological deformation characteristics after pressure compensation in real time. When the simulated geological deformation characteristics meet the boundary weakening conditions, it controls the second expansion mechanism 10 in the corresponding orientation to perform pressure regulation. S4 extracts the axial strain data and displacement data of the test anchor 5 after the pressure adjustment action; S5 calculates the axial force and side friction of the test anchor 5 at different depths based on the axial strain data, and generates the load-bearing assessment results of the test anchor 5 by combining the side friction and displacement data.

[0028] In a specific embodiment of the present invention, the system first retrieves a preset test control target, namely the target test parameters, which include at least the standard confining pressure value that the first expansion mechanism 7 needs to maintain during the test. During the test operation, the system continuously detects the real-time fluid pressure inside the first expansion mechanism 7 at a preset sampling frequency to obtain real-time internal pressure data.

[0029] After acquiring the current internal pressure data, the system compares it with the target test parameters and calculates the change in value between the two to obtain the current pressure deviation value. This pressure deviation value objectively reflects the pressure disturbance caused to the first expansion mechanism 7 by the deformation (such as volume expansion or contraction) of the simulated geological material under load on the test anchor 5. Subsequently, the system generates a corresponding pressure compensation command based on the magnitude and direction of the pressure deviation value. This command drives the fluid to perform input or discharge actions, thereby achieving pressure compensation for the first expansion mechanism 7. Based on the calculation of the pressure deviation value and the fluid inflow and outflow actions, the system establishes a pressure closed-loop feedback, preventing the internal pressure of the first expansion mechanism 7 from rising or falling due to displacement, squeezing, or detachment of the test anchor 5 from the surrounding soil. This reduces pressure fluctuations during the test and achieves stable control of the confining pressure boundary during the test. At the same time, this compensation process enables the system to respond to pressure changes quickly, reducing the lag time of pressure adjustment and improving the pressure control response speed.

[0030] While performing pressure compensation on the first expansion mechanism 7, the system monitors the simulated geological deformation characteristics after pressure compensation in real time by collecting axial strain data. When the simulated geological deformation characteristics meet the preset boundary weakening conditions, the system identifies the specific orientation that needs to be adjusted based on the current deformation characteristics, and controls the second expansion mechanism 10 installed in the corresponding orientation to perform corresponding pressure adjustment actions such as pressurization or depressurization, thereby changing the local boundary constraint state of the simulated geological material and realizing the dynamic simulation of geological weakening or local deformation characteristics.

[0031] After the second expansion mechanism 10 completes the pressure adjustment action at a specific orientation, the system begins to extract the mechanical deformation response data of the test anchor 5 under the stable confining pressure boundary. The system reads and stores the current axial strain data and the real-time displacement data of the top of the test anchor 5.

[0032] By acquiring the position information of multiple preset sampling points along the axial direction on the test anchor 5, the system extracts the specific strain values ​​corresponding to each sampling point from the axial strain data, thereby obtaining the side friction resistance and displacement data. Finally, the system correlates and maps the calculated side friction resistance at each location with the displacement data extracted in step S3, analyzes the evolution law of the side friction resistance gradually increasing with the displacement, and then generates the load-bearing assessment result of the test anchor 5. By establishing the position correspondence of the sampling points and extracting the strain values ​​of the corresponding points, the system can directly calculate the side friction resistance data of the test anchor 5 at different depth positions, solving the problem that traditional static load tests cannot directly obtain the stress state at various positions in the middle of the rod, thus enabling real-time acquisition of side friction resistance data at different positions of the anchor.

[0033] Compared with the prior art, the present invention can achieve stable control of the confining pressure boundary during the test, improve the pressure control response speed, dynamically simulate geological deformation characteristics, and obtain side friction data of different positions of the anchor bolt in real time.

[0034] The following detailed explanation of the steps and procedures for the anchor bolt pull-out and compression test method, with reference to specific embodiments.

[0035] Specifically, in a specific embodiment of the present invention, when the simulated geological deformation characteristics meet the boundary weakening condition, the second expansion mechanism 10 in the corresponding orientation is controlled to perform a pressure regulating action, including: Boundary weakening conditions include: loosening judgment threshold and compression judgment threshold; The simulated geological deformation characteristics were compared with the loosening and compression thresholds, respectively. When the simulated geological deformation characteristics meet the loosening judgment threshold, it is determined that local loosening has occurred, the target pressure regulating azimuth is obtained, and the second expansion mechanism 10 corresponding to the target pressure regulating azimuth is controlled to perform pressure reduction action. When the simulated geological deformation characteristics meet the extrusion judgment threshold, it is determined that local extrusion has occurred, and the second expansion mechanism 10 corresponding to the target pressure adjustment direction is controlled to perform the pressurization action.

[0036] In a specific embodiment of the invention, the system memory pre-configures and stores boundary weakening conditions characterizing different degrees of geological deterioration, specifically including a loosening judgment threshold and a compression judgment threshold. After acquiring the simulated geological deformation characteristics monitored in real time, the system automatically compares the current value of the deformation characteristics with the preset loosening judgment threshold and compression judgment threshold, respectively.

[0037] When the comparison results show that the current simulated geological deformation characteristics meet the loosening judgment threshold, the system determines that a specific area of ​​the current simulated geological material has experienced local loosening. At this time, the central controller 9 analyzes the spatial distribution of the data from each measuring point to obtain the specific spatial orientation that caused the change, i.e., the target pressure regulating orientation. Subsequently, the central controller 9 sends a control command to the pressure regulating loop to control the second expansion mechanism 10 corresponding to the target pressure regulating orientation to perform a pressure reduction action, such as discharging some internal fluid, thereby reducing the local constraint pressure in that orientation and simulating the geological state of loosening and detachment of the surrounding rock.

[0038] When the comparison results show that the current simulated geological deformation characteristics meet the compression judgment threshold, the system determines that the current simulated geological material has undergone local compression. At this time, the central controller 9 also extracts the corresponding target pressure adjustment direction and controls the second expansion mechanism 10 corresponding to the target pressure adjustment direction to perform a pressurization action, such as injecting some fluid, thereby actively increasing the local constraint stress in that direction and simulating the geological state of soil shear dilation or compression; based on the above branch control, the identification and targeted pressure adjustment of different boundary weakening characteristics are realized.

[0039] It should be further explained that the central controller 9 analyzes the spatial distribution of data from each measuring point. Specifically, multiple independent strain sensors 51 are distributed on the outer surface of the test anchor 5 at different circumferential symmetrical positions on the same cross section. During the test operation, the central controller 9 receives and establishes a mapping matrix containing the spatial coordinates of each circumferential measuring point and the real-time axial strain data.

[0040] When the simulated geological deformation characteristics meet the threshold, the central controller 9 extracts the axial strain data of each symmetrical measuring point on the same cross section and performs difference calculation; when the simulated geological material around the test anchor 5 experiences local loosening or local compression, the test anchor 5 is subjected to force and bends, causing the strain sensor 51 in the symmetrical orientation to generate axial strain difference values; the central controller 9 compares the strain difference values ​​of each group of symmetrical measuring points in the cross section and selects the axis of the measuring point with the largest strain difference value or the largest strain change rate; subsequently, the central controller 9 determines the local loosening or local compression orientation that causes the anchor to be subjected to force based on the positive and negative sign characteristics of the positive and negative strain values ​​on the axis of the measuring point, combined with the circumferential arrangement orientation of the measuring point, thereby determining the target pressure adjustment orientation. The central controller 9 sends a control command to the corresponding second expansion mechanism 10 according to the locked target pressure adjustment orientation to execute the corresponding pressure adjustment action.

[0041] Specifically, in a specific embodiment of the present invention, pressure compensation is performed on the first expansion mechanism 7 according to the pressure compensation command, including: extracting a tolerance range based on the target test parameters, wherein the tolerance range represents the critical limit of the pressure deviation of the first expansion mechanism 7; when the internal pressure data is lower than the lower limit of the tolerance range, controlling the air pump 8 to inject fluid into the first expansion mechanism 7; and when the internal pressure data is higher than the upper limit of the tolerance range, controlling the air pump 8 to discharge fluid from the first expansion mechanism 7.

[0042] In a specific embodiment of the present invention, the process of extracting the tolerance range based on the target test parameters is as follows: the system obtains the standard confining pressure value from the target test parameters, and calculates the upper and lower limits of the tolerance range by multiplying the standard confining pressure value by a preset fluctuation coefficient. This tolerance range serves as a threshold for pressure regulation, quantifying the internal pressure fluctuation of the first expansion mechanism 7 into boundary constraints of the upper and lower limits. When the internal pressure of the first expansion mechanism 7 decreases below the lower limit due to external soil deformation, the system controls the air pump 8 to replenish fluid in a timely manner; when the internal pressure increases above the upper limit due to soil compression, the system controls the air pump 8 to discharge fluid in a timely manner.

[0043] By switching between inflation and deflation based on a tolerance range, the internal pressure of the first expansion mechanism 7 is maintained within the tolerance range. This range establishes a control dead zone for the system, avoiding frequent alternations between pumping and deflation when the internal pressure of the first expansion mechanism 7 fluctuates slightly, thus reducing hardware wear. When the internal pressure exceeds the boundary of this range, the system can directly trigger the air pump 8 to inflate and deflate, improving the system's pressure regulation response speed during the load-bearing phase.

[0044] It should be noted that the preset fluctuation coefficient is determined based on the range accuracy of the pressure sensor and the allowable error range for confining pressure fluctuation in the geotechnical testing standards, and its value range is usually 1% to 5%.

[0045] Specifically, in a specific embodiment of the present invention, the method further includes a feedforward control step for the first expansion mechanism 7, which specifically involves: collecting historical axial strain data and calculating the time derivative at adjacent time nodes based on the historical axial strain data to obtain the strain mutation rate; when the absolute value of the strain mutation rate is greater than the preset critical strain rate for boundary damage, extracting the positive and negative sign characteristics of the strain mutation rate; if the strain mutation rate is negative, determining that the soil around the test anchor 5 is undergoing shear expansion and compression, and controlling the air pump 8 to perform a pre-depressurization action; if the strain mutation rate is positive, determining that the soil around the test anchor 5 is undergoing shear contraction and voiding, and controlling the air pump 8 to perform a pre-inflation action.

[0046] In this embodiment of the invention, the system continuously records the historical axial strain data of the test anchor 5 during the test. The system calculates the difference between the axial strain value at the current time node and the axial strain value at the previous adjacent time node, and divides it by the sampling time interval between the two to obtain the strain mutation rate as the time derivative. The magnitude of this strain mutation rate directly reflects the severity of the internal deformation of the test anchor 5. The system compares the absolute value of this strain mutation rate with a preset critical strain rate for boundary damage. Once the absolute value exceeds the critical value, it indicates that the soil is about to undergo shear failure. At this time, the system extracts the sign of the strain mutation rate to identify the physical deformation trend of the soil.

[0047] When the strain mutation rate is negative, it indicates that the test anchor 5 is locally under pressure and tightening. This indicates that the soil around the test anchor 5 is undergoing shear expansion deformation and squeezing the first expansion mechanism 7. Before the pressure inside the first expansion mechanism 7 rises significantly, the system controls the air pump 8 to start pre-depressurization. When the strain mutation rate is positive, it indicates that the test anchor 5 is locally under tension and pulled apart. This indicates that the soil around the test anchor 5 is undergoing shear contraction deformation and detaching from the first expansion mechanism 7. Before the pressure inside the first expansion mechanism 7 drops significantly, the system controls the air pump 8 to start pre-inflation.

[0048] By utilizing the positive and negative characteristics of the strain mutation rate to predict the tendency of soil shear dilatation or shear contraction, the system performs pre-depressurization or pre-inflation operations before the first expansion mechanism 7 generates substantial pressure fluctuations. This process directly uses the deformation signal of the test anchor 5 to guide the pressure adjustment action, shortening the system's response delay to pressure changes within the test chamber, avoiding soil loosening caused by pressure adjustment lag, improving the pressure stabilization speed during high-load mutation stages, and ensuring stable control of confining pressure.

[0049] Specifically, in a specific embodiment of the present invention, obtaining the critical strain rate for boundary damage includes: obtaining the stress-strain curve of a similar simulated geological material under a standard shear test; performing a first-order derivative on the stress-strain curve to obtain a first-order slope function; determining the current position as an inflection point when the first-order slope function first drops to a preset proportion of the initial maximum slope; extracting the corresponding time node of the inflection point and calculating the time derivative of the axial strain data at the corresponding time node to obtain the critical strain rate for boundary damage.

[0050] In one embodiment of the present invention, the system retrieves the stress-strain curves of similar simulated geological materials obtained under standard shear tests before the test. In geotechnical engineering and mechanics of materials, the stress-strain curves of similar simulated geological materials under standard shear tests are physical characteristic curves used to describe the relationship between the magnitude of the force (stress) and the degree of deformation (strain) of soil or rock when subjected to shear force (kneading, pushing force).

[0051] The system performs first-order numerical differentiation on each data point of the stress-strain curve to calculate the first-order slope function reflecting the evolution of the material's shear stiffness. In the initial loading stage, this first-order slope function has an initial maximum slope; as the shear load increases, damage occurs within the material, and the first-order slope function begins to decrease. The system monitors the value of this first-order slope function in real time. When the first-order slope function first decreases to a preset percentage of the initial maximum slope (e.g., a preset percentage of 80%), the system determines that the data point is the critical inflection point where boundary damage occurs in the material.

[0052] Subsequently, the system reads the specific time point corresponding to this inflection point in the standard shear test. The system further retrieves the time derivative of the axial strain data of the tested anchor rod 5 at that time point. This time derivative is the true strain rate when the material enters the damage stage. The system directly stores this strain rate value and uses it as the boundary damage critical strain rate threshold to trigger feedforward control.

[0053] It should be further explained that the preset proportion at which the first-order slope function first drops to the initial maximum slope is determined by the following method: Multiple sets of original stress-strain curve data of similar simulated geological materials under standard shear tests are retrieved. In each set of standard shear tests, as the shear load is continuously applied, the microscopic volumetric changes within the material are monitored in real time using a displacement gauge or acoustic emission detector. When the rate of change of the material's volume (i.e., the rate of change of dilatation or contraction) first abruptly occurs, or when the cumulative energy release rate of the acoustic emission signal first sharply increases, the moment corresponding to this physical state is determined as the material's critical point of substantial mechanical damage. Subsequently, the system extracts the real-time slope value of the first-order slope function of the corresponding stress-strain curve at this critical point of substantial mechanical damage and calculates the ratio of this real-time slope value to the initial maximum slope to obtain the damage slope proportion under the current test group. The system performs an arithmetic average of the damage slope proportions under multiple sets of standard shear tests to determine this preset proportion.

[0054] It should be further explained that the loosening judgment threshold is the negative variation limit corresponding to the critical strain rate of boundary damage, used to characterize the instability critical point of the simulated geological material under shear contraction and voiding state; the extrusion judgment threshold is the positive variation limit corresponding to the critical strain rate of boundary damage, used to characterize the stress critical point of the simulated geological material under shear expansion and extrusion state.

[0055] Specifically, in this embodiment of the invention, extracting the axial strain data and displacement data of the pressure-compensated test anchor 5 includes: collecting the ultimate bearing capacity of the test anchor 5 and dividing the ultimate bearing capacity into several loading levels according to a ratio; applying the loading level level by level, and continuously monitoring the displacement data of the test anchor 5 within the cycle of each loading level; when the change in displacement data per unit time is less than a preset stability threshold and the internal pressure data is within the tolerance range, it is determined that the current loading level has reached a stable state, and the current axial strain data and displacement data are obtained.

[0056] In a specific embodiment of the invention, the ultimate bearing capacity value of the test anchor 5, obtained through prior field destructive testing or pre-set according to design specifications, is first retrieved. The system divides this ultimate bearing capacity into several progressively increasing loading levels according to a preset equal division ratio (e.g., increasing by 10% each time) or increment number. During the test operation, the loading device applies vertical loads to the test anchor 5 progressively according to the divided levels. Within the holding period of each loading level, the displacement sensor continuously collects the real-time deformation of the top of the test anchor 5, generating displacement data continuously distributed over time.

[0057] During the load holding process, the system calculates the difference in displacement data per unit time in real time within a preset time window. The system compares this difference with a preset stability threshold, and simultaneously compares the real-time collected internal pressure data of the first expansion mechanism 7 with the upper and lower limits of the aforementioned tolerance range. The preset stability threshold is determined based on the settlement stability standards for anchor bolt and pile foundation static load tests in current technical specifications, combined with the physical measurement resolution of the displacement sensor. When the displacement change per unit time is less than the preset stability threshold, it indicates that the soil creep deformation of the test anchor 5 under the current load has tended to terminate; simultaneously, when the internal pressure data falls entirely within the tolerance range, it indicates that the external first expansion mechanism 7 has completed its pressure compensation action, and the lateral confining pressure boundary has reached a stable equilibrium state. Only when both conditions are met simultaneously does the system determine the stable state reached at this loading level and formally read and store the axial strain data and displacement data corresponding to this stable state moment.

[0058] Specifically, in a specific embodiment of the present invention, the calculation of the axial force and side friction of the test anchor 5 at different depths based on the axial strain data includes: obtaining the elastic modulus and test cross-sectional area of ​​the test anchor 5; obtaining sampling point information along the axial direction on the test anchor 5, and obtaining the corresponding axial strain data based on the sampling point information; and calculating the cross-sectional axial force based on the elastic modulus, test cross-sectional area, and axial strain data, using the following formula: ; in, Indicates the first i Each sampling point corresponds to axial strain data. E Indicates the elastic modulus. A Indicates the cross-sectional area of ​​the test section. Indicates the first i The axial force at each sampling point was measured; the diameter of the test anchor 5 and the distance between adjacent sampling points were obtained, and the side friction was calculated based on the anchor diameter and the distance between adjacent sampling points, using the following formula: ; in, Indicates side friction resistance. Indicates the spacing between adjacent spaces. Indicates the diameter of the anchor bolt.

[0059] In a specific embodiment of the present invention, the system first retrieves the physical and mechanical property parameters of the test anchor rod 5 itself, namely the elastic modulus and the test cross-sectional area.

[0060] During the calculation process, the system retrieves the spatial topological coordinates of each sampling point pre-arranged on the test anchor 5, using these coordinates as an index to match the axial strain data collected and transmitted back in real time by sensors at each sampling point location. Then, the system substitutes the axial strain values, elastic modulus, and test cross-sectional area of ​​each sampling point into the formula for a forward point-to-point solution, thereby obtaining the axial strain data of the test anchor 5 at different depth positions online. i Axial force at each sampling point This step enables a continuous quantitative mapping of the internal stress of the rod in the spatial depth dimension.

[0061] After obtaining the axial force at each sampling point, the system further retrieves the preset anchor diameter of test anchor 5 and the physical measurement distance between two adjacent sampling points in the axial direction. The system calculates the axial force difference between two adjacent sampling points by dividing the outer surface area of ​​the rod body constructed by the adjacent distance and the anchor diameter using an algebraic analytical formula. i The sampling point and the first i Side friction resistance between +1 sampling points .

[0062] By substituting the extracted axial strain data into the above formula, the axial force of each sampling point is calculated, and the lateral friction resistance at the corresponding position is calculated using the difference in axial force and the spacing between adjacent sampling points. This process directly uses the deformation data inside the rod to calculate the lateral resistance value of each segment online, solving the problem that traditional static load tests can only obtain data from the top and bottom of the component and cannot know the true stress state at various positions in the middle of the rod. Thus, it achieves real-time and accurate acquisition of lateral friction resistance data at different depth positions of the test anchor rod 5.

[0063] This invention also provides a system for testing the pull-out and compressive strength of anchor bolts, such as... Figures 2 to 11 As shown, it includes: a box body 1; a support 2, which is disposed on the upper surface of the box body 1; and a crossbeam 3, one end of which is movably mounted on the support 2, and the other end is a free end for placing the load 6. Connector 4 is installed on the main body of crossbeam 3; test anchor 5 is connected to crossbeam 3 through connector 4 and is located inside box 1; first expansion mechanism 7 is set inside box 1 and covers the periphery of simulated geological material, and the top surface of first expansion mechanism 7 is provided with air inlet and outlet pipe 71; second expansion mechanism 10 is set on the inner wall of box 1 and is used to adjust the local boundary constraint state of simulated geological material; air pump 8 is connected to first expansion mechanism 7 and is used to input or discharge fluid into first expansion mechanism 7; central controller 9 is electrically connected to air pump and is used to control air pump 8 to perform fluid input or discharge actions.

[0064] In this embodiment of the invention, the overall frame is constructed from a box 1, a support 2, and a crossbeam 3. The box 1 serves as the main accommodating space for the experiment, and its interior is filled with simulated geological materials to simulate in-situ underground soil or rock strata.

[0065] On the top surface of the housing 1, the bracket 2, extending directly upwards, is bolted or welded to it. The crossbeam 3 is located above the housing 1, with one end hinged to the bracket 2 via a pivot or sliding rail mechanism, allowing the crossbeam 3 to be finely adjusted in angle or moved up and down in the vertical plane around the mounting point; the other end of the crossbeam 3 extends horizontally away from the bracket 2, forming a suspended free end, which is used to place a pre-set mass load 6, providing a basic mechanical load source for the system through leverage or direct gravity transmission.

[0066] The lower end of the connector 4 is rigidly connected to the top of the test anchor rod 5 by a fastening clamp or threaded pair; the rod of the test anchor rod 5 extends vertically downward from the opening at the top of the box 1 into the interior of the box 1 and is completely embedded in the simulated geological material.

[0067] The first expansion mechanism 7 is located inside the housing 1. The first expansion mechanism 7 has a cylindrical structure, and its outer wall covers the periphery of the simulated geological material. The first expansion mechanism 7 is composed of multiple arc-shaped longitudinal airbag units assembled along the circumference, and its internal space forms an interconnected internal cavity. An air inlet and outlet pipe 71 that communicates with the internal cavity is vertically fixed to the top surface of the first expansion mechanism 7. The air pump 8 is connected to the air inlet and outlet pipe 71 of the first expansion mechanism 7 through a fluid pipeline, and the air pump 8 is electrically connected to an external central controller 9.

[0068] On the inner wall of the housing 1, multiple independent second expansion mechanisms 10 are installed in different circumferential orientations. Each second expansion mechanism 10 is a long strip structure used to fit against the inner wall of the housing 1. Each second expansion mechanism 10 is also connected to an air pump 8 or an independent pressure regulating valve through a pipeline to make independent boundary constraint adjustments for local areas of the simulated geological material.

[0069] Specifically, in the embodiments of the present invention, it further includes: a pressure detection device 72, which is disposed on the first expansion mechanism 7 and is used to detect the internal pressure of the first expansion mechanism 7; the pressure detection device 72 is electrically connected to the central controller 9.

[0070] In a specific embodiment of the present invention, the pressure detection device 72 may be a high-precision pressure sensor or an electronic pressure gauge. The pressure detection device 72 is disposed on the inlet and outlet pipe 71 of the first expansion mechanism 7. Specifically, the detection probe of the pressure detection device 72 is fixed in series on the side wall of the inlet and outlet pipe 71 through a tee connector and extends into the internal fluid channel of the inlet and outlet pipe 71.

[0071] Since the intake and exhaust pipe 71 is directly connected to the internal cavity of the first expansion mechanism 7, the fluid pressure in the internal cavity is transmitted to the intake and exhaust pipe 71 in real time. Therefore, by setting the pressure detection device 72 on the intake and exhaust pipe 71, the internal pressure of the first expansion mechanism 7 can be detected directly and in real time, avoiding the need to directly open holes on the surface of the body of the first expansion mechanism 7 and thus affecting its overall mechanical uniformity.

[0072] The pressure detection device 72 is electrically connected to the central controller 9. During the test operation, the pressure detection device 72 continuously transmits the real-time internal pressure data collected to the central controller 9 through the signal line, providing the central controller 9 with the basic data input for calculating the pressure deviation value and generating pressure compensation commands, thereby achieving stable control of the confining pressure boundary during the test.

[0073] Specifically, in a specific embodiment of the present invention, the strain sensors 51 are arranged at intervals along the axial direction, and the strain sensors 51 located on the same cross section are symmetrically distributed in the circumferential direction; the strain sensors 51 are used to collect axial strain data of the test anchor 5 under load at different depths and in different orientations; the strain sensors 51 are electrically connected to the central controller 9.

[0074] In a specific embodiment of the present invention, the system further includes multiple strain sensors 51. These strain sensors 51 are arranged at intervals along the axial direction on the outer surface of the test anchor rod 5. Specifically, the test anchor rod 5 has multiple pre-defined measurement sections along its axial depth direction. At least two strain sensors 51 are provided on each measurement section, and the strain sensors 51 located on the same section are symmetrically distributed circumferentially along the test anchor rod 5.

[0075] During the test run, when the test anchor 5 undergoes mechanical deformation under load, each strain sensor 51 is used to collect real-time axial strain data of the test anchor 5 under load at different depths and orientations. Due to the circumferentially symmetrical arrangement on the same depth section, when the simulated geological material around the test anchor 5 experiences local loosening or local compression, causing the test anchor 5 to bend under force, the strain sensors 51 located at symmetrical orientations on the same section can respectively capture the tensile or compressive strain caused by bending, thereby generating axial strain data with numerical differences.

[0076] Each strain sensor 51 has its signal output terminal electrically connected to the central controller 9. During the test operation, the strain sensors 51 transmit the axial strain data collected at different depths and orientations to the central controller 9 in real time. The central controller 9 uses this axial strain data to perform difference calculations within the same cross section to determine the target pressure adjustment orientation for local deformation of the simulated geological material. Simultaneously, based on the axial strain data at each depth, the central controller 9 calculates the axial force and side friction of the test anchor 5 at different depths, realizing real-time calculation and monitoring of the side friction of the test anchor 5.

[0077] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for testing the pull-out and compressive strength of anchor bolts, characterized in that, The method includes: S1 acquires the target test parameters and collects the internal pressure data of the first expansion mechanism (7) and the axial strain data of the test anchor rod (5) in real time. S2 obtains the pressure deviation value based on the target test parameters and internal pressure data, generates a pressure compensation command based on the pressure deviation value, and performs pressure compensation on the first expansion mechanism (7) based on the pressure compensation command. S3 monitors the simulated geological deformation characteristics after pressure compensation in real time. When the simulated geological deformation characteristics meet the boundary weakening condition, it controls the second expansion mechanism (10) in the corresponding orientation to perform pressure regulation. S4 extracts the axial strain data and displacement data of the test anchor rod (5) after the pressure adjustment action; S5 calculates the axial force and side friction of the test anchor (5) at different depths based on the axial strain data, and generates the load-bearing evaluation result of the test anchor (5) by combining the side friction with the displacement data.

2. The anchor bolt pull-out and compressive strength test method according to claim 1, characterized in that, When the simulated geological deformation characteristics meet the boundary weakening condition, the second expansion mechanism (10) in the corresponding orientation is controlled to perform a pressure regulating action, including: The boundary weakening conditions include: loosening judgment threshold and compression judgment threshold; The simulated geological deformation characteristics are compared with the loosening and compression thresholds, respectively. When the simulated geological deformation characteristics meet the loosening judgment threshold, it is determined that local loosening has occurred, the target pressure regulating azimuth is obtained, and the second expansion mechanism (10) corresponding to the target pressure regulating azimuth is controlled to perform pressure reduction action; When the simulated geological deformation characteristics meet the compression judgment threshold, it is determined that local compression has occurred, and the second expansion mechanism (10) corresponding to the target pressure adjustment direction is controlled to perform a pressurization action.

3. The anchor bolt pull-out and compressive strength test method according to claim 1, characterized in that, According to the pressure compensation command, pressure compensation is performed on the first expansion mechanism (7), including: Based on the target test parameters, a tolerance range is extracted, and the tolerance range represents the critical limit of the pressure deviation of the first expansion mechanism (7). When the internal pressure data is lower than the lower limit of the tolerance range, the control air pump (8) injects fluid into the first expansion mechanism (7); When the internal pressure data is higher than the upper limit of the tolerance range, the air pump (8) is controlled to discharge fluid from the first expansion mechanism (7).

4. The anchor bolt pull-out and compression test method according to claim 1, characterized in that, It also includes a feedforward control step for the first expansion mechanism (7), specifically: Historical axial strain data is collected, and the time derivative at adjacent time nodes is calculated based on the historical axial strain data to obtain the strain mutation rate. When the absolute value of the strain mutation rate is greater than the preset critical strain rate for boundary damage, the positive and negative sign features of the strain mutation rate are extracted. If the strain mutation rate is negative, it is determined that the soil around the test anchor (5) is undergoing shear expansion and compression, and the air pump (8) is controlled to perform a pre-depressurization action; If the strain mutation rate is positive, it is determined that the soil around the test anchor (5) is shearing and voiding, and the air pump (8) is controlled to perform pre-inflation.

5. The anchor bolt pull-out and compression test method according to claim 4, characterized in that, Obtaining the critical strain rate for boundary damage includes: Obtain stress-strain curves of similar simulated geological materials under standard shear tests; Taking the first derivative of the stress-strain curve yields the first-order slope function; When the first-order slope function first drops to a preset proportion of the initial maximum slope, the current position is determined as an inflection point; Extract the corresponding time node of the inflection point, and calculate the time derivative of the axial strain data at the corresponding time node to obtain the critical strain rate of boundary damage.

6. The anchor bolt pull-out and compressive strength test method according to claim 1, characterized in that, Extract the axial strain data and displacement data of the pressure-compensated test anchor (5), including: Collect the ultimate bearing capacity of the test anchor (5), and divide the ultimate bearing capacity into several loading levels according to the proportion; The loading levels are applied in stages, and the displacement data of the test anchor (5) is continuously monitored during the period of each loading level. When the change in displacement data per unit time is less than a preset stability threshold and the internal pressure data is within the tolerance range, it is determined that the current loading level has reached a stable state, and the current axial strain data and displacement data are obtained.

7. The anchor bolt pull-out and compressive strength test method according to claim 1, characterized in that, Based on the axial strain data, the axial force and side friction of the test anchor (5) at different depths were calculated, including: Obtain the elastic modulus and test cross-sectional area of ​​the test anchor (5); Obtain the sampling point information along the axial direction on the test anchor rod (5), and obtain the corresponding axial strain data based on the sampling point information; The axial force of the cross section is calculated based on the elastic modulus, the test cross-sectional area, and the axial strain data, using the following formula: ； in, Indicates the first i Each sampling point corresponds to the axial strain data. E Represents the elastic modulus. A This represents the area of ​​the test cross section. Indicates the first i Axial force at each sampling point; Obtain the diameter of the test anchor (5) and the distance between adjacent sampling points, and calculate the side friction resistance based on the anchor diameter and the distance between adjacent sampling points, as follows: ； in, This indicates the side friction resistance. Indicates the adjacent spacing, This indicates the diameter of the anchor rod.

8. A test system for the pull-out and compression resistance of anchor bolts, characterized in that, The system is used to perform the anchor pull-out and compression test method according to any one of claims 1 to 7, including: Box (1); A bracket (2) is disposed on the upper surface of the housing (1); The crossbeam (3) has one end movably mounted on the bracket (2) and the other end is a free end for placing the load (6); The connector (4) is installed on the main body of the crossbeam (3); The test anchor rod (5) is connected to the crossbeam (3) through the connector (4), and the test anchor rod (5) is located inside the box (1); The first expansion mechanism (7) is located inside the box (1) and covers the periphery of the simulated geological material. The top surface of the first expansion mechanism (7) is provided with an air inlet and outlet pipe (71). The second expansion mechanism (10) is installed on the inner wall of the box (1) to adjust the local boundary constraint state of the simulated geological material; An air pump (8) is connected to the first expansion mechanism (7) and is used to input or discharge fluid into the first expansion mechanism (7); A central controller (9) is electrically connected to the air pump and is used to control the air pump (8) to perform fluid input or discharge actions.

9. The anchor bolt pull-out and compression test system according to claim 8, characterized in that, Also includes: Pressure detection device (72), which is disposed on the first expansion mechanism (7) and is used to detect the internal pressure of the first expansion mechanism (7); The pressure detection device (72) is electrically connected to the central controller (9).

10. The anchor bolt pull-out and compression test system according to claim 8, characterized in that, Also includes: Strain sensor (51) The strain sensors (51) are arranged at intervals along the axial direction, and the strain sensors 51 located on the same cross section are symmetrically distributed in the circumferential direction; The strain sensor (51) is used to collect axial strain data of the test anchor (5) under load at different depths and in different orientations; The strain sensor (51) is electrically connected to the central controller (9).

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