An adjustable self-indicating auxiliary support device for prestressed anchor tensioning and its test method

Abstract

This invention provides an adjustable self-indicating auxiliary support device and test method for prestressed anchor bolt tensioning. The device, by incorporating an anti-slip support base, increases the contact area between the device and the anchoring platform or working rock surface, preventing stress concentration damage and eccentric tensioning of the anchor bolt caused by eccentric compression. By designing the telescopic connecting rod as a sliding and extendable structure, it can be adjusted according to actual operational requirements, while simultaneously increasing the lateral stiffness of the device, preventing damage under pressure, and improving device stability. The self-indicating auxiliary support device involved in this invention can adaptively adjust according to engineering conditions, and easily replace damaged components. The force measurement self-indication method of this invention can correct tension loads, overcoming the poor applicability of traditional tensioning pre-tests; it can also reflect changes in prestress loss of the anchor bolt, accurately determining the prestressed anchor bolt anchoring force with higher precision than traditional tensioning jack force control.

Description

Technical Field

[0001] This invention relates to the technical field of prestressed anchor tensioning construction equipment, and more specifically, to an adjustable self-adjusting auxiliary support device and test method for prestressed anchor tensioning. Background Technology

[0002] Prestressed anchor systems are active support structures with high tensile strength, commonly used for tunnel rock face and foundation pit slope support. One end of the anchor head is tightly bonded to the soil and rock under the action of anchor mortar, while the free end can be tensioned. This actively reinforces weak interlayers and sliding surfaces in the soil and rock mass. After grouting, once the grout strength meets the tensioning conditions, prestressing tensioning and anchoring of the anchor are performed to ensure the support structure meets design strength requirements. The tensioning and anchoring process is a crucial step in prestressed anchor construction. Currently, hydraulic jacks are commonly used as prestressing tensioning equipment. To facilitate tensioning and anchoring, support components need to be installed between the hydraulic jack and the working rock face or anchoring platform to provide the necessary working space for anchoring operations.

[0003] Hydraulic jacks vary greatly in model and size, and anchor rod diameters and matching anchor nuts are diverse. Existing support components are mostly fixed radially and cannot be adjusted. When using large-volume jacks or large-diameter anchor rods, it is difficult to provide sufficient space for tensioning and anchoring operations, limiting their applicability. Furthermore, the units of the hydraulic jack's pressurization parameters and the anchor rod tensioning prestressing design parameters are not consistent. In actual on-site construction, preliminary tests are required to establish empirical conversion formulas. During on-site tensioning, conversion based on the anchor rod diameter is necessary, affecting construction progress and making it difficult to guarantee operational accuracy.

[0004] The prior art CN205154202U discloses an anchor bolt tensioning mechanism, including a support, legs, and a through-hole hydraulic cylinder capable of applying tension to the anchor bolt. There are at least three legs arranged longitudinally on the support. A through hole for the anchor bolt to pass through is opened in the middle of the support. The through-hole hydraulic cylinder is located above the support. At least three connecting holes are arranged at intervals around the through hole on the support. The outer periphery of the legs has external threads and is able to move up and down in the corresponding connecting holes. Each leg is threaded with a nut that can limit the position of the leg. In use, the support is placed on the rock slope by the outriggers. The anchor rod passes through the through hole in the support. After adjusting the vertical position of the outriggers relative to the support so that the support surface is perpendicular to the anchor rod axis, it is fixed with a nut. The through-hole hydraulic cylinder is placed on the anchor rod protrusion above the support. After the through-hole hydraulic cylinder performs work, it applies tension to the anchor rod with the reaction force of the support, thus applying prestress to the anchor rod. The support can be leveled quickly and accurately, which facilitates the tensioning of the anchor rod. However, this patent lacks a radial adjustment device, which cannot meet the actual construction needs, the structural stability cannot be guaranteed, and it is not a detachable structure, so force measurement is not possible.

[0005] Therefore, it is necessary to design an adjustable self-monitoring auxiliary support device and test method for prestressed anchor bolt tensioning. This device can be adjusted to adapt to various working conditions for anchor bolt tensioning construction, and provide sufficient operating space between the jack and the working rock surface or anchoring platform for anchoring operations. It can also monitor the application of prestress in the anchor bolt in real time, providing convenient and accurate assistance for prestressed anchor bolt tensioning construction. Summary of the Invention

[0006] This invention addresses the technical problems existing in the prior art by providing an adjustable self-monitoring auxiliary support device and testing method for prestressed anchor bolt tensioning. This solves the current technical problem that the lack of a matching adjustable self-monitoring auxiliary support device and testing method for anchor bolt tensioning and anchoring construction, which can monitor the tension force, severely affects the quality of anchor bolt tensioning and construction speed.

[0007] According to a first aspect of the present invention, a prestressed anchor bolt tension adjustable self-indicating auxiliary support device is provided, comprising: a circular bearing plate, multiple support rods, and a telescopic connecting rod connected to the support rods;

[0008] The circular bearing plate is provided with multiple radial support rod adjustment slots; each support rod adjustment slot is provided with four levels of adjustment holes for support rod limiting; the center of the same level adjustment hole is connected to form an equilateral triangle, the center of the equilateral triangle coincides with the center of the circular bearing plate; concentric prestressed anchor rod limiting holes are provided at the center of the circular bearing plate 1.

[0009] After the support rod passes through the support rod adjustment groove, the circular pressure plate is restricted by adjusting the fastening nut;

[0010] The telescopic connecting rod is equipped with a threaded telescopic rod, and the horizontal distance between the support rods can be adjusted by rotating the threaded telescopic rod.

[0011] Based on the above technical solution, the present invention can also be improved as follows.

[0012] Optionally, the included angle between any two radial support rod adjustment slots is 120°.

[0013] Optionally, the support rod is divided into a threaded section, a force sensor section, and a round rod section. The threaded section is engaged with the adjusting fastening nut, the force sensor section is connected to an external force measuring device, and the lower end of the round rod section is connected to the anti-slip support base.

[0014] Optionally, the force measuring device includes a strain measuring device, a temperature compensation device, and an external display device. The external display device can monitor the entire tensioning process in real time and reflect the anchor bolt holding force.

[0015] Optionally, the anti-slip support base is a hollow frustum shape.

[0016] Optionally, the round section of the support rod is connected using a telescopic connecting rod.

[0017] According to a second aspect of the present invention, a method is provided for use in an adjustable self-indicating auxiliary support device for prestressed anchor tensioning, the test method comprising the following steps:

[0018] Test preparation: Before the construction of prestressed anchor rods, the anchor rods are assembled, including the anchor head and anchor rod reinforcement. The assembled anchor rods are installed into the cleaned anchor rod holes. The required cement mortar is prepared according to the design, and the anchor rods are grouted for reinforcement and the anchoring platform is poured. Pre-tensioning is performed to ensure that all components of the mechanism are in close contact, and the readings of the force gauge and the dial gauge of the auxiliary support device are checked.

[0019] Anchor bolt tensioning and anchoring construction: Based on the maximum load design value of the anchor bolt, the load is applied in multiple stages. After each stage of loading is completed, the readings of the jack dial and the force gauge of the auxiliary support device are recorded, and the anchor bolt is tightened with the anchor bolt nuts. Depending on the rock strata conditions, the changes in the force gauge readings are observed during the process. After the last stage of loading is completed, the anchor bolt nuts are tightened and locked, the readings of the external force gauges are read, the anchor bolt anchoring force is determined, and the deformation of the anchor bolt is calculated.

[0020] Optionally, the deformation of the anchor bolt can be calculated using the following formula:

[0021]

[0022] In the formula, A s —Cross-sectional area of ​​a single support rod (m²) 2 E s — Elastic modulus of the support rod (MPa), K — Sensitivity of the resistance strain gauge, k — Stiffness coefficient of the anchor rod (N / m), U0 — Bridge output voltage (V), U1 — Bridge input voltage (V).

[0023] Optionally, the grading is selected as 5 to 8 levels of progressive loading.

[0024] Optionally, during the loading process, the loading rate can be selected as 50kN / min to 100kN / min, and the holding time for each load stage can be 5 to 10 minutes.

[0025] The technical effects and advantages of this invention are as follows:

[0026] This invention designs an adjustable self-monitoring auxiliary support device and test method for prestressed anchor bolt tensioning. The device can adjust the width and height of the operating space, making it suitable for prestressed anchor bolt construction under various working conditions. It can also monitor the prestressing process of the anchor bolt in real time through a force sensor. It has the advantages of convenience, accuracy, and high stability, and has good prospects for widespread application.

[0027] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0028] Figure 1 An elevation view of the working state of the adjustable prestressed anchor tensioning auxiliary support device provided in an embodiment of the present invention;

[0029] Figure 2 This is an elevation view of the prestressed anchor bolt tension adjustable self-illuminating auxiliary support device provided in an embodiment of the present invention;

[0030] Figure 3 This is a structural diagram of a circular pressure plate provided in an embodiment of the present invention;

[0031] Figure 4 A structural diagram of the support rod provided in an embodiment of the present invention;

[0032] Figure 5 This is a structural diagram of the telescopic connecting rod provided in an embodiment of the present invention;

[0033] Figure 6 This is a schematic diagram of the cross-sectional structure of the anti-slip support base provided in an embodiment of the present invention;

[0034] Figure 7 The test method and test flowchart for the adjustable self-indicating auxiliary support device for prestressed anchor tensioning provided in the embodiments of the present invention;

[0035] Figure 8 This is a schematic diagram illustrating the working principle of the force sensor provided in an embodiment of the present invention.

[0036] Figure descriptions: 1-Circular bearing plate; 11-Support rod adjustment groove; 12-Prestressed anchor rod limiting hole; 2-Support rod; 21-Threaded section of support rod; 22-Force sensor section; 23-Round rod section; 3-Adjusting fastening nut; 4-Telescopic connecting rod; 41-Threaded telescopic rod; 5-Anti-slip support base; 6-Prestressed anchor rod; 7-Jack; 8-Anchoring nut; 9-Bearing gasket; 10-Prestressed fastening nut. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. 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. It is understood that, based on the deficiencies in the background art, the embodiments of the present invention propose a prestressed anchor bolt tensioning adjustable self-adjusting auxiliary support device, as detailed in the attached drawings. Figure 1 As shown, the auxiliary support device includes a circular pressure plate 1, a support rod 2, and a telescopic connecting rod 4; wherein,

[0038] The circular pressure plate 1 is provided with three radial support rod adjustment grooves 11. Each support rod adjustment groove 11 is provided with four levels of adjustment holes for limiting the support rod 2. The center line of the same level of adjustment hole can form an equilateral triangle. The center of the equilateral triangle coincides with the center of the circular pressure plate 1. Concentric prestressed anchor rod limiting holes 12 are provided at the center of the circular pressure plate 1.

[0039] The support rod 2 is divided into a threaded section 21, a force sensor section 22, and a round rod section 23. The adjusting fastening nut 3 is used in conjunction with the threaded section 21 of the support rod 2. The force sensor section 22 is connected to an external display screen. The lower end of the round rod section 23 is connected to the anti-slip support base 5.

[0040] Preferably, the anti-slip support base 5 is a hollow frustum shape, which can increase the contact area between the support rod and the working rock surface or anchoring platform, and prevent the equipment from moving during the tensioning process.

[0041] Specifically, the support rod 2 passes through the concave hole of the radial support rod adjustment groove 11 via the upper threaded section 21, and is constrained by the circular bearing plate 1 by the adjusting fastening nuts 3 on both the upper and lower sides, providing a working platform for the jack 7. The prestress loading during the anchor tensioning process can be monitored in real time through the external display screen of the force sensor section 22. The circular rod section 23 of the support rod 2 is connected by a telescopic connecting rod 4, the middle of which is a threaded telescopic rod 41. The end of the circular rod section 23 of the support rod 2 is connected to the anti-slip support base 5. In use, the prestressed anchor rod passes through the anchor rod limiting hole of the circular bearing plate, and the tensioning jack passes through the prestressed anchor rod and is in close contact with the circular bearing plate. The upper part of the tensioning jack is fixed with an anchoring nut, and a pressure-bearing pad is placed between the prestressed anchor rod and the working rock surface or anchoring platform. After tensioning is completed, the prestressed anchoring nut is used to fix and lock the prestressed anchor rod.

[0042] The force measuring device includes a strain measuring device, a temperature compensation device, and an external display device, which can monitor the entire tensioning process in real time and reflect the anchor bolt bearing force.

[0043] Preferably, the support rod 2 can adjust the tensioning construction space and the parallel relationship between the equipment and the prestressed anchor rod by adjusting the upper threaded section. The support rod 2 can monitor the prestress loading of the anchor rod by connecting an external display panel to a force sensor.

[0044] The telescopic connecting rod 4 is provided with a threaded telescopic rod 41. By rotating the threaded telescopic rod 41, the horizontal distance between the support rods 2 can be adjusted, and the contact friction resistance between the round rod section 23 of the support rod 2 and the telescopic connecting rod 4 can be provided.

[0045] Preferably, the telescopic connecting rod 4 can adjust the horizontal distance between the support rods via a central threaded telescopic rod, thereby improving the lateral stability of the support rods. In this embodiment, the telescopic connecting rod 4 has a sliding and extendable structure, which can be adjusted according to actual operational requirements, increasing the lateral stiffness of the device, preventing damage under pressure, and improving the stability of the device.

[0046] Preferred solutions such as Figure 2 In this design, the circular bearing plate 1 is made of a circular steel plate with a thickness of 40-60mm and a diameter of 50cm. An anchor rod limiting hole 12 with a diameter of 80mm is provided at the center of the plate. Three multi-level support rod adjustment grooves 11 are evenly distributed in the circumferential direction. The adjustment holes of the same level can ensure that the resultant force of the axial force of the support rod coincides with the axial force of the anchor rod, thus avoiding the auxiliary support equipment being eccentrically compressed.

[0047] Preferred solutions such as Figure 3 In this design, the circular pressure plate 1 is provided with three radial support rod adjustment grooves 11. By adjusting the fixed position of the support rods, it can accommodate different types of tensioning jacks. The centers of the adjustment recesses of the same level of support rods form an equilateral triangle, the centroid of which coincides with the center of the prestressed anchor rod limiting hole. The circular pressure plate 1 is provided with radial support rod adjustment grooves 11 and prestressed anchor rod limiting holes 12; the included angle between any two radial support rod adjustment grooves 11 is 120°, and concentric prestressed anchor rod limiting holes 12 are provided at the center of the circular pressure plate 1.

[0048] Preferred solutions such as Figure 4In this structure, the support rod 2 is divided into a threaded section 21, a force sensor section 22, and a round rod section 23. The support rod 2 can adjust the tensioning construction space and the parallel relationship between the equipment and the prestressed anchor rod by adjusting the upper threaded section 21. The support rod can monitor the prestress loading of the anchor rod through an external display panel connected to the force sensor section 22. The support rod 2 is made of 28mm diameter steel bars. The three support rods have good compressive strength, ensuring the overall stability of the structure and meeting the usage conditions for tensioning various types of anchor rods. The tensioning construction space and the parallel relationship between the equipment and the prestressed anchor rod can be adjusted by adjusting the upper threaded section 21. Furthermore, the support rod 2 can monitor the prestress loading of the anchor rod through an external display panel connected to the force sensor 22, which is a pressure sensor used in conjunction with an external display screen.

[0049] Preferred solutions such as Figure 5 In this process, the telescopic connecting rod 4 can be adjusted in spacing via the threaded telescopic rod 41 to provide lateral constraint for the support rod 2 and prevent the support rod 2 from bending.

[0050] Preferred solutions such as Figure 6 In this embodiment, the anti-slip support base 5 is a hollow frustum shape, which increases the contact area between the support rod 2 and the working rock surface or anchoring platform, preventing the equipment from moving during tensioning. The advantage of using the anti-slip support base 5 in this embodiment is that it expands the direct contact area between the device and the anchoring platform (which is inclined) or the working rock surface (which is uneven), preventing stress concentration damage and eccentric tensioning of the anchor rod caused by eccentric pressure on the device.

[0051] It should be noted that when using the auxiliary support device described in this embodiment of the invention, first, the telescopic connecting rod 4 is fitted onto the round section of the support rod 2, and the three support rods are combined through the threaded telescopic rod 41. The threaded telescopic rod 41 is tightened appropriately to fix the telescopic connecting rod at the same horizontal height as the support rod 2. The anti-slip support base 5 is installed at the bottom of the round section of the support rod 2. The lower adjusting fastening nut 3 is installed to the threaded section of the support rod 2, and the threaded section of the support rod passes through the radial adjusting groove. According to the model, volume, and prestressed anchor diameter of the tensioning jack, a suitable adjusting hole is selected, and the horizontal distance between the support rods is adjusted through the threaded telescopic rod 41. The upper and lower adjusting fastening nuts of the circular bearing plate 1 are adjusted. 3. Fix the support rod 2 to the adjustment hole, pass the prestressed anchor rod 6 through the anchor rod limiting hole on the circular bearing plate 1, and fine-tune the upper and lower fastening nuts 3 to ensure that the prestressed anchor rod 6 is parallel to the support rod 2; pass the hydraulic jack 7 through the prestressed anchor rod 6, and fix the hydraulic jack 7 to the auxiliary support device through the anchoring nut 8; after completing the assembly of the tensioning mechanism, connect the external display screen to the force sensor 22, and then the staged tensioning of the prestressed anchor rod can begin; during the tensioning process, the staged loading of the hydraulic jack can be monitored through the external display screen of the force sensor 22; after the tensioning is completed, carry out the anchoring operation of the fastening nut 10 in the space between the auxiliary support device and the working rock surface or anchoring platform.

[0052] It should be noted that the auxiliary support device described in this invention is applicable to anchor bolt tensioning construction under various working conditions. Specifically, the auxiliary support device is suitable for retaining works using anchor bolt support systems in tunnels, foundation pit slopes, and other engineering projects. Its purpose is to provide a working platform for anchor bolt tensioning, provide construction space for anchor bolt anchoring, and monitor the loading status of the tensioning equipment in real time during construction.

[0053] It should be noted that the auxiliary support device can be adjusted horizontally and vertically to accommodate various types of jacks and anchor bolts of different diameters for prestressing tensioning construction.

[0054] In summary, the auxiliary support device of this invention can adjust the lateral width and vertical height between the circular bearing plate and the working rock surface or anchoring platform through the adjustment groove of the circular bearing plate and the adjusting fastening nuts on the upper and lower sides, providing sufficient operating space for the tightening operation of the anchoring nuts; the radial distance of the three parallel support rod sections can be adjusted by the telescopic connecting rod, which is applicable to the tensioning construction of jacks of various models and volumes and anchor bars of different diameters; the force sensor on the support rod and the external display screen can monitor the prestress loading of the anchor bar in real time during the tensioning process, facilitating safe and precise construction; the length adjustment of the threaded section of the support rod can ensure that the auxiliary support device is parallel to the anchor bar, and in conjunction with the telescopic connecting rod and the anti-slip support base, it can improve the overall stability of the equipment structure, avoid eccentric tensioning, and increase the stress area of ​​the structure; all parts of this invention are detachable, which facilitates equipment transportation and replacement of damaged parts; to improve the service life of materials, the equipment material can be made of stainless steel or coated with anti-rust paint.

[0055] The auxiliary support device described in this invention can be adaptively adjusted according to the engineering situation, and the assembled parts can be easily replaced after damage.

[0056] Furthermore, this embodiment of the invention also provides a test method for the above-mentioned adjustable self-indicating auxiliary support device for prestressed anchor tensioning, the test procedure being as follows: Figure 7 As shown, the specific experimental procedure is as follows:

[0057] ① Test preparation work: S1. Before the construction of prestressed anchor rods, assemble the anchor rods, including the anchor head and anchor rod reinforcement. Install the assembled anchor rods into the cleaned anchor rod holes. Prepare the required cement mortar according to the design and grout the anchor rods for reinforcement.

[0058] It should be noted that before the prestressed anchor bolts are installed, the anchor bolts, including the anchor head and anchor bolt reinforcement, need to be assembled using welding or threaded connections, depending on the length of the anchor bolt. A suitable anchor bolt hole diameter should be designed based on the selected anchor bolt, and the anchor bolt hole should be constructed using a hydraulic or electric anchor bolt drilling rig. The assembled anchor bolts should be installed into the cleaned anchor bolt holes, and the required cement mortar should be prepared according to the design for grouting reinforcement. Afterwards, the anchor bolt anchor platform can be poured. The next stage of construction can only proceed when the concrete strength meets the tensioning requirements. Auxiliary support equipment should be assembled. The lateral clearance of the support rods and the vertical space between the circular bearing plate and the working rock surface or anchoring platform should be adjusted according to the jack model and anchor bolt diameter. The upper and lower adjusting nuts of the circular bearing plate should be adjusted to ensure that the circular bearing plate is perpendicular to the anchor bolt, preventing eccentric tension on the anchor bolt during loading. An external display device for the force gauge should be installed to monitor the loading during the tensioning process. The tensioning jack should be inserted through the anchor bolt and installed on the circular bearing plate, and the jack should be fixed using anchoring nuts. The jack loading and pre-tensioning process ensures close contact between the various parts of the mechanism, and the readings of the jack dial and the force gauge of the auxiliary support device are checked.

[0059] After the preliminary preparations are completed, the anchor bolt tensioning test can be carried out. Details are as follows:

[0060] ② Conduct anchor bolt tensioning tests. Based on the maximum design load value of the anchor bolt, apply the load in 5 to 8 stages, with an application rate of 50 kN / min to 100 kN / min. After each stage of loading, read the gauges on the jack and the force gauges on the auxiliary support device, and record the data. Then, tighten the anchor bolt nuts to secure it. Depending on the rock strata, hold the load for 5 to 10 minutes for each stage, and observe the changes in the force gauge readings during this process. After the final stage of loading, tighten the nuts to lock the bolt in place.

[0061] After the anchor tensioning test is completed, the following are also included:

[0062] ③ Unloading and equipment removal: After the anchor bolt fastening nuts are locked, the jacks are unloaded in stages. The unloading speed is greater than the loading speed, which is generally 100kN / min to 200kN / min. After unloading, first remove the anchor nuts on the top of the jacks, and then remove the jacks and auxiliary support devices in sequence.

[0063] In this embodiment of the invention, the working principle of the tensioning mechanism is as follows: After the tensioning mechanism, including the anchor rod, auxiliary support device, and jack, is assembled, the anchor rod tension force is provided through the jack and external hydraulic device. The forces at both ends of the jack are balanced by the entire tensioning mechanism. The force at the upper part of the jack is transmitted to the anchor rod reinforcement through the anchor nut, and finally acts on the anchoring end of the anchor rod and the surrounding rock and soil. The force at the lower part of the jack is transmitted to the three support rods through the circular bearing plate of the auxiliary support device, and finally acts on the working rock surface or anchoring platform. That is, the tension force applied by the jack to the anchor rod is equal to the resultant force of the three support rods of the auxiliary support device. The change of the axial force of the anchor rod during the tensioning process can be monitored in real time by the force gauge on the support rod.

[0064] ② Working principle of the force sensor in the auxiliary support device: The force sensor uses a strain gauge to measure the compressive strain of the support rod under pressure during prestressing loading. The change in strain reflects the change in axial force of the support rod. The strain sensor uses a full-bridge circuit connection, with four strain gauges evenly distributed on the outer circumference of the force sensor. An insulating protective sleeve is installed on the outside, and the circuit leads are connected to an external data acquisition device. A schematic diagram of its working principle is shown below. Figure 8 As shown in the figure, U0—bridge output voltage (V); U1—bridge input voltage (V); R 12 ,R 23 ,R 34 ,R 41 —Bridge strain gauge resistance (Ω); where R 12 =R 23 =R 34 =R 41 .

[0065] The four strain gauges shown in the figure can measure the strain change of the support rod under compression. The change in the electric field of the external circuit is converted into axial force data of the support rod, reflecting the loading status of the tensioning equipment. The full-bridge circuit resistance strain gauges have temperature compensation, which can eliminate the interference of external ambient temperature changes on the measurement data. The calculation formula is as follows:

[0066] When the device is unloaded, the strain gauge change is 0, and the output voltage is U0 = 0, meaning the bridge circuit is balanced. Typically, R is taken as... 12 =R 23 =R 34 =R 41 .

[0067] If the input voltage U1 remains constant during the operation of the bridge circuit, then the output voltage U0 can be expressed by the following formula:

[0068]

[0069] In the formula, ΔR 12 ,ΔR 23 ,ΔR34 ,ΔR 41 Representing the bridge strain gauge R 12 ,R 23 ,R 34 ,R 41 The change in Ω;

[0070] The change in resistance in the bridge circuit can be expressed as:

[0071] ΔR=ξ·Δε (2)

[0072] The output voltage U0 can then be expressed in terms of strain as follows:

[0073]

[0074] Since taking R 12 =R 23 =R 34 =R 41 Then the above formula can be transformed into

[0075]

[0076] K=ξ·R (5)

[0077] The strain of the support rod measured by this force gauge is:

[0078]

[0079] The total pressure on the three support rods, i.e., the tensioning force of the jack, can be calculated using the following formula.

[0080]

[0081] Where: ξ—resistance strain coefficient; Δε 12 ,Δε 23 ,Δε 34 ,Δε 41 —Bridge strain change; K—Strain gauge sensitivity; F—Total pressure (kN) on the three support rods; A s —Cross-sectional area of ​​a single support rod (m²) 2 ); E s — Elastic modulus of the support rod (MPa); Δε — Average strain of the support rod.

[0082] ③ Formula for calculating anchor prestress:

[0083] The tension applied by the jack is transmitted to the anchor rod through the upper anchor nut, and finally acts on the anchoring end of the anchor rod.

[0084] Calculation of stress distribution at the anchorage end:

[0085] The composite elastic modulus of the anchorage end can be calculated using the following formula:

[0086]

[0087] The stiffness coefficient of the elastic support of the anchor bolt can be calculated by the following formula:

[0088]

[0089] The prestress of the anchor bolt can be calculated using the following formula:

[0090] F y =k·ΔL (10)

[0091] Since the force of the jack is completely transferred to the anchor rod, it can be seen from formulas (7)-(10) that when the anchor rod is tensioned in stages to the design value of the anchor rod prestress (without considering the creep and relaxation of the anchor rod reinforcement), the deformation of the anchor rod can be calculated by the following formula:

[0092]

[0093] Where: E0—composite elastic modulus of the anchor bolt body (MPa); E1—elastic modulus of the anchor bolt reinforcement (MPa); E2—elastic modulus of the grouting reinforcement (MPa); A—cross-sectional area of ​​the anchor bolt hole (m²) 2 A1—Cross-sectional area of ​​anchor reinforcement (m²) 2 b—calculated width of retaining structure (m); L—design length of anchor bolt (m); l—design length of anchor bolt anchoring end (m); s—horizontal spacing of anchor bolts (m); ΔL—length variation of anchor bolt (m); k—stiffness coefficient of anchor bolt (N / m).

[0094] In summary, the force measurement self-indication device in the embodiments of the present invention has the following beneficial effects:

[0095] (1) It can correct the tension load. The traditional tension pre-experimentation relies on empirical formulas from the pre-experimentation to determine the tension force, which has poor applicability.

[0096] (2) It can reflect the changes in prestress loss of anchor bolts and accurately determine the anchoring force of prestressed anchor bolts;

[0097] (3) The accuracy is much higher than that of traditional tension jack tension control.

[0098] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A prestressed anchor bolt tensioning adjustable self-indicating auxiliary support device, characterized in that, include: A circular bearing plate (1), multiple support rods (2), and a telescopic connecting rod (4) connected to the support rods (2); wherein, The circular pressure plate (1) is provided with multiple radial support rod adjustment grooves (11). Each support rod adjustment groove (11) is provided with four levels of adjustment holes for limiting the support rod (2). The center lines of the same level of adjustment holes form an equilateral triangle. The center of the equilateral triangle coincides with the center of the circular pressure plate (1). Concentric prestressed anchor rod limiting holes (12) are provided at the center of the circular pressure plate (1). After the support rod (2) passes through the support rod adjustment groove (11), the circular pressure plate (1) is restricted by adjusting the fastening nut (3). The support rod (2) is divided into a threaded section (21), a force sensor section (22), and a round rod section (23). The threaded section (21) is fitted with the adjusting fastening nut (3). The force sensor section (22) is connected to an external force measuring device, which includes a strain measuring device, a temperature compensation device, and an external display device. The external display device can monitor the entire tensioning process in real time and reflect the anchor rod's holding force. The lower end of the round rod section (23) is connected to the anti-slip support base (5). The round rod segment (23) is connected by a telescopic connecting rod (4), which is provided with a threaded telescopic rod (41), and the horizontal distance between the support rods (2) is adjusted by rotating the threaded telescopic rod (41).

2. The prestressed anchor bolt tensioning adjustable self-indicating auxiliary support device according to claim 1, characterized in that, The included angle between any two radial support rod adjustment grooves (11) is 120°.

3. The prestressed anchor bolt tensioning adjustable self-indicating auxiliary support device according to claim 1, characterized in that, The anti-slip support base (5) is a hollow frustum shape.

4. A test method for an adjustable self-indicating auxiliary support device for prestressed anchor tensioning as described in any one of claims 1 to 3, characterized in that, The experimental method includes the following steps: Test preparation: Before the construction of prestressed anchor rods, the anchor rods are assembled, including the anchor head and anchor rod reinforcement. The assembled anchor rods are installed into the cleaned anchor rod holes. The required cement mortar is prepared according to the design. The anchor rods are grouted for reinforcement, the anchoring platform is poured, and the pretensioning is performed to ensure that all components of the mechanism are in close contact. The readings of the force gauge of the auxiliary support device and the dial reading of the jack are checked. Anchor bolt tensioning and anchoring construction: Based on the maximum load design value of the anchor bolt, the load is applied in multiple stages. After each stage of loading is completed, the readings of the jack dial and the force gauge of the auxiliary support device are recorded, and the anchor bolt is tightened with the anchor bolt nuts. During each stage of loading, the changes in the force gauge readings are observed. After the last stage of loading is completed, the anchor bolt nuts are tightened and locked, the readings of the external force gauges are read, the anchor bolt anchoring force is determined, and the deformation of the anchor bolt is calculated.

5. The test method for an adjustable self-indicating auxiliary support device for prestressed anchor tensioning according to claim 4, characterized in that, The deformation of the anchor bolt is calculated using the following formula: In the formula, Expressed as the cross-sectional area of ​​a single support rod. ; Expressed as the elastic modulus of the support rod. ; Expressed as the sensitivity of the resistance strain gauge; This is expressed as the stiffness coefficient of the anchor bolt. ; This is represented as the bridge output voltage. ; Represented as bridge input voltage, .

6. The test method for an adjustable self-indicating auxiliary support device for prestressed anchor tensioning according to claim 4, characterized in that, The multi-level progressive loading is selected as 5 to 8 levels.

7. The test method for an adjustable self-indicating auxiliary support device for prestressed anchor bolt tensioning according to claim 4, characterized in that, During the loading process, the loading rate is selected to be 50kN / min to 100kN / min, and the holding time for each load stage is 5 to 10 minutes.

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