An easy-to-construct and multifunctional integrated anchor cable and its construction and testing method

Abstract

This invention discloses an easy-to-construct and multifunctional integrated anchor cable, a pressure-dispersing anchor cable for slope, foundation pit, and mountain reinforcement. The front end of the steel strand bundle of the anchor cable is equipped with a rolling guide cap, and it is lowered into the duct primarily through rolling friction. The steel strands and inner anchors of each unit anchor are tightly bonded to the rock mass by injected high-strength cement grout to form an anchor body. This anchor body is formed in the lower middle part of the anchoring section, providing sufficient preset straightening force. Each inner anchor has a force sensor connected to an external signal at its bottom. The steel strand bundle outside the anchor body is only spaced apart along its length by several external centering supports. When the steel strand bundle is straightened, the free section is injected with high-strength cement grout or a grout that provides weak constraint to the steel strand bundle. This invention completely eliminates steel strand bending, turning, and strong constraints, significantly reducing tension friction with optimized straightness; it achieves full life-cycle digitalization and traceability from production, construction, operation and maintenance to recycling.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical anchoring engineering technology, specifically relating to a pressure-dispersing anchor cable for slope, foundation pit, and mountain reinforcement, and particularly to a fully digital anchor cable and its construction and testing method that integrates multiple functions such as significantly reducing free section friction, smooth lowering, and measurable force at the bottom of the anchoring section. Background Technology

[0002] Anchor cables are a fundamental tool used in soil and rock anchoring, bridge and foundation pit construction, and are currently used on a considerable scale in many infrastructure projects in major cities. However, with the continuous expansion and deepening of engineering applications, traditional pressure-distributing anchor cables have revealed many long-standing and difficult-to-solve technical problems, which are described and summarized below.

[0003] First, drilling is required to create channels for anchor cable installation. Since these channels are usually drilled at an angle downwards, they inevitably experience some degree of deflection as the drilling equipment deepens due to its own weight. Furthermore, traditional anchor cables have multiple internal supports within the free section, making the steel strands of the embedded anchor cables prone to bending and numerous turns in the high proportion of the free section. This increases frictional resistance and affects the actual feedback length of the prestress. Moreover, the lowering action, which relies primarily on sliding friction, results in high anchor cable resistance, a high risk of jamming, and significant construction difficulty.

[0004] Secondly, the use of high-strength cement grouting throughout the hole results in strong constraint on the steel strands in the free section of the anchor cable, which can even cause severe seizing and significant prestress loss.

[0005] Furthermore, anchoring force monitoring can only be performed at the anchor head, and the actual force at the bottom of the anchoring section cannot be obtained. As a result, the construction management cannot accurately grasp the actual prestress of the anchor cables in each duct.

[0006] In addition, the verification of anchor cable length and hole depth relies on manual measurement and on-site supervision, which is prone to human error and disputes; permanent anchorage and hot-melt temporary anchorage structures are not interchangeable, and internal anchorages are not interchangeable, resulting in high production and construction costs. Summary of the Invention

[0007] To address the aforementioned pain points of traditional anchor cable technology, this invention aims to provide an easy-to-construct and multifunctional integrated anchor cable and its construction and testing method.

[0008] The solution of the present invention to achieve the above-mentioned objective is: an easy-to-construct and multifunctional integrated anchor cable, which is a pressure-dispersing anchor cable used for slope, foundation pit, and mountain reinforcement. The front end of the steel strand bundle of the anchor cable is equipped with a rolling guide cap, and it is lowered into the channel mainly by rolling friction. The steel strands and inner anchors of each unit anchor of the anchor cable are tightly bonded to the rock mass by the injected high-strength cement grout to form an anchor body. The anchor body is formed in the middle and lower part of the anchoring section, which can provide a sufficient preset straightening force. Each inner anchor is equipped with a force sensor connected to the external signal at the bottom. The steel strand bundle outside the anchor body is only sleeved with several external centering brackets at intervals along the length direction. In the straightening state of the steel strand bundle, the free section and part of the anchoring section are injected with high-strength cement grout or grout that provides weak constraint to the steel strand bundle.

[0009] Furthermore, the rolling guide cap is integrally fixed to the steel strand bundle along the same central axis, and the end of the rolling guide cap is spherical and has distributed embedded balls, as well as the outer centering bracket.

[0010] Furthermore, the rolling guide cap is axially eccentrically connected to the steel strand bundle and can rotate freely in the radial direction. The rolling guide cap has balls embedded in the outer wall region near the eccentric position of the steel strand bundle that are in contact with the channel.

[0011] Furthermore, the radially outer side of the outer centering bracket is formed into an arc surface or is provided with rollers that have a rolling contact hole wall.

[0012] Furthermore, the inner anchorage of the anchor cable in the anchorage section is a permanent anchorage type, a heat-melt recyclable type, or a combination of both.

[0013] Furthermore, the steel strand is provided with a PE sheath, and within a preset length range near the orifice, the surface of the PE sheath is provided with laser-engraved and permanently retained markings. The markings are scale lines distributed every 1cm along the length of the steel strand, and indicate the length value of the corresponding anchor cable and the boundary position of each unit anchor.

[0014] Furthermore, the outer anchor of the anchor cable is equipped with a dedicated grouting hole and a standardized servo control interface. The dedicated grouting hole is connected to the channel where the free section is located, and the servo control interface is used for an external force-displacement dual closed-loop control system.

[0015] Furthermore, the depths of the unit anchors in the anchor cable are misaligned, and a force measuring device is provided at the outer anchor end of the anchor cable. The frictional resistance of the anchor cable in the duct is equal to the difference in tension between the force sensor and the force measuring device.

[0016] The solution of the present invention to achieve another objective mentioned above is as follows: The construction and inspection method of the anchor cable includes the following steps: S1, on the basis of a pre-set duct, first insert the front end of the anchor cable into the duct and guide it into the duct to a pre-set depth using a rolling guide cap; S2, inject high-strength cement grout into the bottom of the anchoring section and cure it to a pre-set strength to form an anchor body based on the rock mass; S3, based on the outer anchor of the anchor cable, apply pre-tension stress to the steel strand bundle to eliminate sagging and bending of the steel strand bundle and achieve the maximum straightness; S4, while maintaining the pre-tensioned and straightened state, inject grout that provides weak constraint to the steel strand bundle into the duct where the free section and part of the anchoring section are located through the special grouting hole provided by the outer anchor; S5, after the grout injected in S4 has solidified, perform formal tensioning and locking of the anchor cable.

[0017] Furthermore, the total number of anchor cables used in a project reaches hundreds, and some of the anchor cables are equipped with force sensors at the bottom and force measuring devices at the outer anchor ends as test anchors for fully digital force measurement. The remaining anchor cables are improved anchors that only adjust the frictional resistance of the free section. The improved anchors are evenly distributed throughout the construction area, and the test anchors are distributed and interspersed among the improved anchors.

[0018] The anchor cable product and its construction and testing method of this invention have outstanding substantive features. The technical effects reflected in its application include: 1) Rolling external centering supports and rolling guide caps are set at different positions of the anchor cable, which mainly reduces the lowering resistance of the anchor cable by rolling friction, and can be smoothly placed in place by its own weight; there is no internal support at the free end of the steel strand, and the free section is grouted with weak constraint, which completely eliminates the bending, turning and strong constraint of the steel strand, and greatly reduces the tension friction with the optimized straightness to the greatest extent.

[0019] 2) Force is measured directly at the bottom of the anchorage section, and the monitoring data is accurate and reliable. A force measuring device is installed at the outer anchor end, and the actual frictional resistance of the pipeline in the duct can be directly obtained by measuring the force difference between the two ends. The outer anchor is pre-set with a dedicated grouting hole or servo control interface, which is conducive to achieving smooth and dense grouting without interfering with the condition of the steel strand. It also creates the necessary conditions for future intelligent construction and robotic construction without increasing the current cost.

[0020] 3) Both permanent and temporary hot-melt anchors share the same anchor cable body, namely a low-friction, bottom force measuring and laser scale system, which enables free selection and combination and covers all application scenarios.

[0021] 4) In engineering applications, a batch model of 2% test anchors with force measurement at both ends and 98% improved anchors without force measurement is adopted, which takes into account both testing accuracy and engineering economy. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the easy-to-construct and multifunctional integrated anchor cable of the present invention.

[0023] Figure 2 yes Figure 1 A close-up structural diagram of the anchoring section of the anchor cable shown.

[0024] Figure 3 yes Figure 1 A close-up structural diagram of the free section of the anchor cable shown.

[0025] Figure 4 yes Figure 1 A close-up structural diagram of the anchorage other than the anchor cable shown.

[0026] Figure 5 This is a flowchart of the construction process for the anchor cable of this invention. Detailed Implementation

[0027] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, so as to make the technical solution of the present invention easier to understand and master, and thus to make a clearer definition of the scope of protection of the present invention.

[0028] like Figures 1 to 3 As shown in the technical overview, this invention is an easy-to-construct and multifunctional integrated anchor cable, widely used in slope 1, foundation pit, and mountain reinforcement as a pressure-dispersing anchor cable. In the construction application of this anchor cable 3, the drilled duct is roughly divided in half along its length into an anchoring section P and a free section Q. The anchor cable forms an outer anchor end R outside the hole where it penetrates the slope. The anchoring section and the free section are completely separated in structure, grouting material, and function. The main body of the anchor cable's steel strand bundle is fitted with several external centering supports at intervals along its length to constrain it and prevent expansion and bending. A rolling guide cap 5 is attached to the front end of the steel strand bundle, and it is lowered into the duct primarily through rolling friction. In the anchoring section, the steel strands and inner anchors of each unit anchor are tightly bonded to the rock mass by the injected high-strength cement grout 6a to form an anchor body. This anchor body is formed in a section P1 near the bottom of the duct in the anchoring section, providing sufficient preset straightening force. Each inner anchor has an externally connected force sensor 33 at its bottom. When the steel strand bundle is in a straightened state, the free section and part of the anchorage section P2 are filled with grout 6b, which provides weak constraint to the steel strand bundle, to maintain the linearity of the steel strand bundle and to ensure low frictional resistance in the free section range if additional tensioning is required after long-term use. Of course, if no additional tensioning is required after long-term use, high-strength cement grout 6a can be directly injected for sealing.

[0029] Therefore, in order to overcome the inconveniences of traditional anchor cables being lowered into non-perfectly linear ducts, which are mainly based on sliding friction and prone to bending, turning, and getting stuck, this invention innovates the two main structures of the anchor cable entering the hole. This changes the insertion action from being mainly based on sliding friction to being mainly based on rolling friction. Furthermore, the high-strength consolidation of the anchoring section is adapted to the deflection shape at the end of the duct, and the linear straightening of the steel strand in the free section and the weak constraint grouting reduce the frictional resistance, thereby significantly reducing the loss of prestress along the length of the steel strand.

[0030] More specifically, such as Figure 2 The anchor cable shown has a first unit anchor 31a, a second unit anchor 31b, and a third unit anchor 31c, which are staggered according to depth. The illustration is only a cross-sectional view; the actual number of unit anchors is much greater. It can be understood that the anchoring section is composed of multiple unbonded steel strands of each unit anchor, and an inner centering bracket 7 is provided between the steel strands to ensure that each steel strand is centered and evenly distributed. After the anchoring section reaches the preset depth, high-strength cement grout (a common standard practice in the industry, details omitted) needs to be injected to form an anchor body that is tightly bonded to the rock mass, providing the main anchoring force. As shown in the illustration, a rolling guide cap is provided at the end of the first unit anchor at the bottom (i.e., the steel strand located at the center of the steel strand bundle based on the inner centering). In a preferred embodiment, the end of the rolling guide cap 5 is spherical and is axially eccentrically connected to the steel strand of the first unit anchor and can rotate freely radially. The rolling guide cap has three ball bearings 51 embedded in the outer wall area near the eccentric position of the steel strand (i.e., the bottom surface area that touches the duct wall). Because the eccentric position is relatively low, regardless of whether the steel strand bundle rotates as a whole during lowering, it rotates relative to each other within the rolling guide cap. The weight of the steel strand bundle ensures that the bottom area of ​​the rolling guide cap, containing only the ball bearings, always faces and contacts the borehole wall. This allows the anchor cable to achieve guidance and smoothly enter the borehole through rolling friction, while maintaining a relatively low cost for the ball bearings. Simultaneously, the first unit anchor 31 has a force sensor 33 installed at the bottom of its support body 32, which can directly collect the actual anchoring force at the bottom of the anchoring section, achieving precise monitoring from the anchoring source. When the first unit anchor has only a single steel strand, its axial eccentricity after contacting the rolling guide cap is as follows... Figure 2 As shown in the EE section on the lower right side, when the first unit anchor is a set of two steel strands, its axial eccentricity after contact with the rolling guide cap is as follows. Figure 2 The EE cross-section is shown in the lower right corner on the left.

[0031] As an alternative implementation, the rolling guide cap can also be integrally fixed to the steel strand bundle along its central axis, with the end of the rolling guide cap being spherical and having distributed embedded balls. In this way, even if the rolling guide cap rolls radially with the steel strand bundle as a whole, a portion of the balls will always remain in contact with the channel wall in the direction of gravity, thereby achieving the aforementioned guiding and rolling friction-based travel mode.

[0032] like Figure 3 As shown, the steel strands of each unit anchor in the free section of the anchor cable are arranged in parallel linearly. No internal partition supports are installed, and only outer centering supports 4 are spaced out along the length direction. These supports serve only a centering function and do not clamp or bind the steel strand bundles. The spacing is sufficient to prevent the steel strands from diverging and deforming. The outer diameter of the outer centering support 4 is basically adapted to the inner diameter of the channel, and its surface is formed into an arc, allowing for sliding friction with the channel wall and avoiding most obstructions for smooth passage. Simultaneously, rollers 41 can be installed on the outer wall of the outer centering support 4, enabling rolling contact with the channel wall for even smoother passage. After the outer centering support is fitted onto the steel strand bundle, its axial direction is basically locked by the steel strand bundle. Therefore, the axial direction of the outer centering support is basically perpendicular to the radial plane of the channel, and the rollers 41 on its periphery can reliably contact the channel wall for smooth rolling. The free section is filled with low-strength, low-modulus, weakly constrained grout 6b, preferably foamed concrete or low-strength mortar, which does not bind the steel strands and can significantly reduce tension friction.

[0033] Furthermore, considering the anchorage section P, the anchor cable uses a universal internal anchorage mounting base. One type of internal anchorage is a permanent anchorage, used for permanent anchorage applications and not recyclable; the other is a heat-fused recyclable internal anchorage, used for temporary anchorage applications and recyclable. Both types of internal anchorages share the same anchor cable body and are interchangeable, allowing a single body to cover all application scenarios.

[0034] From the outer anchor end R, the outer anchor 34 is equipped with a dedicated grouting hole 341, which is connected to the free section duct. This allows for the injection of weakly constrained grout while the steel strand is pre-tensioned and straightened. The grouting process does not interfere with the straightened state of the steel strand, ensuring dense grouting and convenient construction. Typically, the steel strand is fitted with a PE sheath. Within approximately 2 meters of the anchor cable near the duct opening, a permanent scale line is laser-engraved every 1cm on the outer wall of the PE sheath, marking the corresponding length value and the boundary position of each unit anchor. This laser scale allows direct reading of the anchor cable length and insertion depth, eliminating the need for manual measurement and on-site supervision. Furthermore, the scale is permanent, does not fade, and does not shift. After removing the anchor, the sheath can be flipped open to accurately identify the position of each unit anchor, enabling full life-cycle remeasurement and re-tensioning.

[0035] Furthermore, the outer anchor end R has a reserved standardized servo control interface 342 on the outer anchor 34, which can be used for an external force-displacement dual closed-loop control system for active deformation control and prestress regulation in high-precision, high-safety engineering projects. However, due to the high cost of high-precision servo control systems, they are difficult to widely implement in conventional projects. Therefore, this servo control interface is reserved, making the high-precision servo control system an optional configuration. Conventional projects can omit its installation without affecting the main functions, balancing economic efficiency and future intelligent upgrades.

[0036] The anchor depths of each unit anchor in the anchor cable are staggered. The force sensor is located at the bottom of the lowest unit anchorage and transmits data outwards via a signal wire. A force measuring device is also provided at the outer anchor end of the anchor cable. The actual frictional resistance of the anchor cable in the duct is derived from the tension difference between the force sensor and the force measuring device. Typically, a project uses hundreds of anchor cables in total. Here, a portion of the anchor cables can utilize fully digital force-measuring test anchors, i.e., a force sensor is installed at the bottom of the anchorage section, and a force measuring device is installed at the outer anchor end; while the remaining anchor cables are selected as improved anchors (i.e., without digital force measurement) to reduce the frictional resistance of the free section. From a usage perspective, because test anchors are more expensive and the number of force measurement points is limited and relatively dispersed, only a small number of test anchors combined with a large number of improved anchors are needed to meet construction requirements. For example, 2% of the test anchors can be used in conjunction with 98% of the improved anchors. Regarding the distribution of the two types of anchor cables on the specific construction slope, the test anchors are set at large intervals, either evenly or non-evenly, covering all required force measurement points. The improved anchors are distributed around each test anchor as the center, and are relatively evenly distributed throughout the entire construction area.

[0037] like Figure 5 The diagram shows the construction process flow chart of the anchor cable of the present invention. It includes the following steps: S1. Based on a pre-set duct, insert the anchor cable with the front end facing downwards into the duct, and guide it into the duct to a pre-set depth using a rolling guide cap; S2. Inject high-strength cement grout into the bottom of the anchoring section and cure it to a pre-set strength to form an anchor body based on the rock mass; S3. Based on the outer anchor of the anchor cable, apply pre-tension stress to the steel strand bundle to eliminate sagging and bending and achieve maximum straightness; S4. Maintaining the pre-tensioned and straightened state, inject grout that provides weak constraint to the steel strand bundle into the duct containing the free section and part of the anchoring section through the dedicated grouting hole provided by the outer anchor; S5. After the grout injected in S4 has solidified, perform the formal tensioning and locking of the anchor cable.

[0038] As can be seen from the detailed description of the embodiments of the easy-to-construct and multifunctional integrated anchor cable and its construction and testing method of the present invention, this solution has outstanding substantive features and significant progress after its application, which are explained from multiple aspects as follows.

[0039] 1) Rolling external centering supports and rolling guide caps are set at different positions of the anchor cable. Rolling friction is the main way to reduce the lowering resistance of the anchor cable, which can be smoothly lowered by its own weight. There are no internal supports at the free end of the steel strand, and the free section is grouted with weak constraint, which completely eliminates the bending, turning and strong constraint of the steel strand, and greatly reduces the tension friction with the optimized straightness.

[0040] 2) Force is measured directly at the bottom of the anchorage section, and the monitoring data is accurate and reliable. A force measuring device is installed at the outer anchor end, and the actual frictional resistance of the pipeline in the duct can be directly obtained by measuring the force difference between the two ends. The outer anchor is pre-set with a dedicated grouting hole or servo control interface, which is conducive to achieving smooth and dense grouting without interfering with the condition of the steel strand. It also creates the necessary conditions for future intelligent construction and robotic construction without increasing the current cost.

[0041] 3) Both permanent and temporary hot-melt anchors share the same anchor cable body, namely a low-friction, bottom force measuring and laser scale system, which enables free selection and combination and covers all application scenarios.

[0042] 4) In engineering applications, a batch model of 2% test anchors with force measurement at both ends and 98% improved anchors without force measurement is adopted, which takes into account both testing accuracy and engineering economy.

[0043] In summary, this invention integrates low-friction guidance, rolling lowering, a weakly constrained free section, force measurement at the bottom of the anchoring section, permanent laser scale at the tail, interchangeable internal anchorages, a reserved servo control interface, and a digital detection scheme, achieving digital management and control throughout the entire lifecycle from construction to operation and maintenance. Besides the above embodiments, this invention may have other implementations. All technical solutions formed by equivalent substitutions or transformations fall within the scope of protection claimed by this invention.

Claims

1. An easy-to-construct and multifunctional integrated anchor cable, a pressure-dispersing anchor cable used in slope, foundation pit, and mountain reinforcement, characterized in that: The front end of the steel strand bundle of the anchor cable is equipped with a rolling guide cap, and it is lowered into the duct mainly by rolling friction. The steel strands and inner anchors of each unit anchor of the anchor cable are tightly bonded to the rock mass by the injected high-strength cement grout to form an anchor body. The anchor body is formed in the middle and lower part of the anchoring section, which can provide a sufficient preset straightening force. Each inner anchor is equipped with a force sensor connected to the outside of the signal at the bottom. The steel strand bundle outside the anchor body is only sleeved with several external centering brackets along the length direction. In the straightening state of the steel strand bundle, the free section and part of the anchoring section are injected with high-strength cement grout or grout that provides weak constraint to the steel strand bundle.

2. The easy-to-construct and multifunctional integrated anchor cable according to claim 1, characterized in that: The rolling guide cap is integrally fixed to the steel strand bundle along the same central axis. The end of the rolling guide cap is spherical and has distributed embedded balls. The outer centering bracket.

3. The easy-to-construct and multifunctional integrated anchor cable according to claim 1, characterized in that: The rolling guide cap is axially eccentrically connected to the steel strand bundle and can rotate freely radially. The rolling guide cap has balls embedded in the outer wall area near the eccentric position of the steel strand bundle that are in contact with the channel.

4. The easy-to-construct and multifunctional integrated anchor cable according to claim 1, characterized in that: The radial outer side of the outer centering bracket is formed into an arc surface or is equipped with rollers that have a rolling contact hole wall.

5. The easy-to-construct and multifunctional integrated anchor cable according to claim 1, characterized in that: The inner anchorage of the anchor cable in the anchorage section is a permanent anchorage type, a heat-melt recyclable type, or a combination of both.

6. The easy-to-construct and multifunctional integrated anchor cable according to claim 1, characterized in that: The steel strand is equipped with a PE sheath, and within a preset length range near the orifice, the surface of the PE sheath is provided with laser-engraved and permanently retained markings. The markings are scale lines distributed every 1cm along the length of the steel strand, and indicate the length value of the corresponding anchor cable and the boundary position of each unit anchor.

7. The easy-to-construct and multifunctional integrated anchor cable according to claim 1, characterized in that: The outer anchor of the anchor cable is equipped with a dedicated grouting hole and a standardized servo control interface. The dedicated grouting hole is connected to the channel where the free section is located, and the servo control interface is used for an external force-displacement dual closed-loop control system.

8. The easy-to-construct and multifunctional integrated anchor cable according to claim 1, characterized in that: The depths of the anchor units in the anchor cable are misaligned, and the outer anchor end of the anchor cable is equipped with a force measuring device. The frictional resistance of the anchor cable in the duct is equal to the difference in tension between the force sensor and the force measuring device.

9. The construction inspection method for the anchor cable according to any one of claims 1 to 8, characterized in that... Including the following steps: S1. Based on the preset duct, first insert the front end of the anchor cable into the opening, and use the rolling guide cap to guide it into the duct to the preset depth; S2. High-strength cement grout is injected into the bottom of the anchoring section and cured to the preset strength to form an anchor body based on the rock mass; S3. Based on the external anchor of the anchor cable, apply pre-tension stress to the steel strand bundle to eliminate sagging and bending and achieve the maximum straightness of the steel strand bundle. S4. While maintaining the pre-tensioned and straightened state, inject grout that provides weak constraint to the steel strand bundle into the ducts where the free section and part of the anchorage section are located through the special grouting holes provided by the external anchorage. S5. After the grout injected in S4 has solidified, the anchor cable will be formally tensioned and locked.

10. The construction testing method according to claim 9, characterized in that: The total number of anchor cables used in a project reaches hundreds, and some of the anchor cables are equipped with force sensors at the bottom and force measuring devices at the outer anchor ends as test anchors for fully digital force measurement. The remaining anchor cables are improved anchors that only adjust the frictional resistance of the free section. The improved anchors are evenly distributed throughout the construction area, and the test anchors are distributed and interspersed among the improved anchors.

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