An intelligent response self-adaptive anchor rod supporting structure for an expansive soil slope and a construction method thereof

Abstract

This invention relates to the field of geotechnical engineering slope protection technology, and particularly to an intelligent response adaptive anchor support structure and construction method for expansive soil slopes. The structure includes support anchors and a slope protection structure. The slope protection structure, from the inside out, consists of an intelligent response water-sealing layer laid on the slope surface and a slope protection drainage layer covering it. The support anchors sequentially include an anchor head, an anchor pressure-relieving device, an anchor free section, and an anchoring section, with the anchor free section and anchoring section being an integrally formed rod. In this solution, a distributed humidity control system composed of a water-swellable rubber sleeve and a rubber ring is used to dynamically track and regulate the humidity of the slope soil. Furthermore, by integrating a constant resistance pressure-relieving device, an intelligent working cycle of rigid locking, flexible pressure relief, and automatic reset of the support system is achieved. This allows for precise control of prestress and safe release of excessive deformation energy, significantly improving the safety and durability of the support system under repeated expansion and contraction loads.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering slope support technology, and in particular to an intelligent response adaptive anchor support structure and construction method for expansive soil slopes. Background Technology

[0002] Expansive soils are rich in highly hydrophilic clay minerals such as montmorillonite and illite, exhibiting significant water absorption and expansion, followed by shrinkage and cracking upon water loss. This repeated expansion and contraction poses a serious safety hazard to engineering construction, especially slope stability. During rainfall, water infiltration causes soil expansion, generating enormous expansive stress; conversely, during droughts, water evaporation causes soil shrinkage, forming a network of tensile cracks. This wet-dry cycle not only significantly weakens the soil but also creates a vicious cycle: shrinkage cracks provide a convenient pathway for the next rainfall to infiltrate deeper, leading to more severe deep expansion and deformation, ultimately causing shallow slope collapses and deep slippage, resulting in instability and failure.

[0003] As a common slope protection measure, anchor bolts are embedded in stable soil and rock through anchor sections. The slope surface is then reinforced with measures such as shotcrete mesh, frame beams, and concrete panels to achieve surface protection and deep reinforcement. However, for expansive soil slopes protected by traditional anchor bolts, the expansive soil absorbs water and expands during the rainy season. The anchor bolts constrain this deformation, causing a surge in stress on the bolts. This expansion and deformation can generate shear forces on the bolts, potentially pulling out the grout in the anchor section or causing pull-out failure of the bolt itself, leading to anchor bolt failure and slope damage. During droughts, the expansive soil shrinks as it loses water, creating voids between the soil and the grout in the anchor section. This results in a loss of anchor resistance that is irrecoverable, reducing the anchoring force and affecting the slope's stability safety factor, increasing the risk of landslides. Furthermore, the shrinkage of the expansive soil after water loss creates tension cracks, providing channels for rainwater infiltration and exacerbating the damage to the anchor structure caused by the expansion and deformation of the expansive soil. In summary, traditional anchor bolt protection measures for expansive soil slopes are prone to anchor bolt failure under the influence of external wet and dry cycles, leading to slope instability and damage.

[0004] Therefore, this invention proposes an intelligent response adaptive anchor support structure and construction method for expansive soil slopes. By incorporating a distributed humidity regulation system consisting of water-swellable rubber sleeves and rubber rings into the anchor rods, dynamic tracking and control of slope soil humidity are achieved. During the rainy season, water absorption reduces soil infiltration, while during the dry season, water release compensates for soil shrinkage and inhibits drying shrinkage cracks, thus breaking the vicious cycle of "dry shrinkage-water seepage-wet swelling" that leads to slope instability. Secondly, by integrating a constant resistance pressure relief device, an intelligent working cycle of "rigid locking-flexible pressure relief-automatic reset" is achieved in the support system. This allows for precise control of prestress and safe release of excessive deformation energy, significantly improving the safety and durability of the support system under repeated expansion and contraction loads. Summary of the Invention

[0005] Technical problem to be solved: Traditional anchor bolt protection measures are prone to failure under the action of dry and wet cycles in the external environment, which can lead to slope instability and damage.

[0006] To address the shortcomings of existing technologies, this invention provides an intelligent response adaptive anchor support structure and construction method for expansive soil slopes, thereby solving the technical problems mentioned in the background section.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A smart response adaptive anchor support structure for expansive soil slopes includes support anchors and a slope protection structure. The slope protection structure consists of, from the inside out, a smart response water-sealing layer laid on the slope surface and a slope protection drainage layer covering it. The support anchors consist of, in sequence, an anchor head, an anchor pressure relief device, an anchor free section, and an anchoring section, wherein the anchor free section and the anchoring section are integrally formed rods.

[0009] The anchor head and the rod body are connected by an anchor pressure relief device.

[0010] In one possible implementation, the smart responsive sealing layer is made of a mixture of SAP particles, bentonite, and sand, and the slope protection drainage layer is assembled from EPS modules with tongue and groove structures.

[0011] In one possible implementation, the free section of the anchor bolt is wrapped with a water-swellable rubber sleeve.

[0012] In one possible implementation, the anchor bolt anchoring section is provided with multiple water-swellable rubber rings at equal intervals, thereby dividing the anchor bolt anchoring section into multiple segmented anchoring units.

[0013] In one possible implementation, the anchor head includes a locking nut, an anchor plate, and an upper anchor, wherein the anchor plate is a galvanized steel plate with anti-slip teeth on the bottom.

[0014] In one possible implementation, the anchor bolt pressure relief device includes a cylindrical connecting sleeve, with an axial force transmission rod slidably connected inside the connecting sleeve. One end of the axial force transmission rod passes through the connecting sleeve and is threadedly connected to the upper anchor bolt, while the other end is fixedly connected to a conical plug. A friction assembly consisting of three arc-shaped friction blocks arranged in a ring is provided between the conical plug and the connecting sleeve.

[0015] In one possible implementation, a ring-shaped cone plug pusher is fixedly connected to the outside of the axial force transmission rod. The cone plug pusher integrates a preload adjustment mechanism consisting of multiple preload screws. Preload springs are respectively provided between the cone plug pusher and the three friction blocks, and a return spring is provided on the outside of the axial force transmission rod.

[0016] In one possible implementation, a construction method for an intelligent response adaptive anchor support structure for expansive soil slopes, as described above, is applied. The method includes the following steps:

[0017] S1. Intelligent response water sealing layer for construction: Dry mix SAP particles, bentonite and medium-coarse sand evenly according to the design ratio, add water and mix wet, then spread in layers on the slope and compact.

[0018] S2. Assemble the slope protection and drainage layer: Assemble the EPS modules with tenons and grooves onto the intelligent response water sealing layer;

[0019] S3. Drilling and cleaning the hole;

[0020] S4. Rod installation: Install the support anchor rod with water-swellable rubber sleeve and water-swellable rubber rings spaced apart into the borehole.

[0021] S5. Segmented Pressure Grouting: Through the grouting pipe at the bottom of the anchor bolt and the segmented grouting valve, each segmented anchoring unit is subjected to graded pressure grouting from bottom to top, as detailed below:

[0022] The graded pressurization method first sets the initial pressure, and then gradually increases the pressure to the target pressure according to the set pressure value. When the grouting rate is less than the threshold at the target pressure, the grouting work is completed after stabilizing the pressure.

[0023] S6. Install the anchor bolt relief device and anchor bolt head, and perform tensioning and locking, as follows:

[0024] Pre-installation: The reset spring, cone plug push plate, cone plug, friction assembly, preload spring, and preload adjustment mechanism are assembled in the connecting sleeve at the factory. The preload spring is adjusted and locked by the preload adjustment mechanism to ensure that the pressure relief threshold of each anchor bolt is strictly consistent with the design value. After calibration, the connecting sleeve is sealed to form an independent anchor bolt pressure relief device.

[0025] Anchor bolt pressure relief device installation: The middle anchor bolt is threaded to the connecting sleeve, the anchor plate is placed at the wellhead, the upper anchor bolt is threaded through the through hole of the anchor plate and threaded to the axial force transmission rod, and the locking nut is rotated to squeeze the anchor plate;

[0026] Pressure locking: Connect the tensioning equipment to the upper anchor rod, tension in stages, stabilize for ~ minutes after each stage of tensioning, and finally lock by tightening the lock nut.

[0027] Beneficial effects compared to existing technologies:

[0028] 1. In this scheme, the water-swellable rubber material installed in the free section and anchoring section of the anchor bolt constitutes a distributed humidity regulation system. The water-swellable rubber sleeve absorbs water and expands during the rainy season, reducing the infiltration of water. At the same time, the radial pressure generated by it effectively counteracts the squeezing effect of soil expansion on the rod body, significantly reducing the abnormal increase of anchor bolt stress. During the dry season, it slowly releases water, effectively compensating for soil water loss, significantly inhibiting the generation and development of drying shrinkage cracks, and fundamentally cutting off the vicious cycle of drying shrinkage cracking, rainwater infiltration, and wet expansion damage.

[0029] 2. In this scheme, a static friction threshold is preset by the preload spring. When the axial force of the anchor rod is lower than this threshold, the device is in a rigid locked state to ensure effective transmission of the preload. When the soil expansion causes the axial force to exceed the limit, the conical friction pair breaks through the static friction and enters a controllable sliding state, continuously releasing pressure with constant dynamic friction, and orderly releasing the accumulated deformation energy to prevent the rod from being pulled apart or the support system from brittle failure. When the load decreases, the reset spring drive system automatically resets. This process realizes the intelligent cycle of the support system from rigid bearing to flexible pressure release and then to automatic recovery, which significantly improves the safety and durability of the support structure.

[0030] 3. In this scheme, the water-swellable rubber ring-shaped segmented anchoring unit and the segmented high-pressure grouting technology used in the anchoring section allow the grout to split and penetrate into the surrounding soil fissures under pressure, forming root-like grout veins. This improves the mechanical interlocking force between the anchoring section and the surrounding soil, upgrading the anchoring mechanism from simple friction anchoring to a composite anchoring that combines friction and mechanical embedding, greatly improving the scale and reliability of the anchoring force. Attached Figure Description

[0031] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0032] Figure 1 This is a schematic diagram of the structure for reinforcing expansive soil and rock slopes according to the present invention;

[0033] Figure 2 This is a schematic diagram of the EPS block tenon and groove structure of the present invention;

[0034] Figure 3 This is a schematic diagram of the anchor rod of the present invention;

[0035] Figure 4 This is a schematic diagram of the state of the anchor bolt pressure relief device of the present invention;

[0036] Figure 5 This is a schematic diagram showing the installation relationship of the conical plug and friction assembly of the present invention;

[0037] Figure 6This is a flowchart of the method steps of the present invention.

[0038] Legend: 1. Anchor head; 101. Locking nut; 102. Anchor plate; 103. Upper anchor; 2. Anchor pressure relief device; 201. Connecting sleeve; 202. Axial force transmission rod; 203. Conical plug; 204. Conical plug push plate; 205. Return spring; 206. Friction assembly; 207. Preload spring; 208. Preload adjustment mechanism; 209. Friction block; 3. Anchor free section; 301. Middle anchor; 302. Water-swellable rubber sleeve; 4. Anchor anchoring section; 401. Lower anchor; 402. Segmented anchoring unit; 403. Water-swellable rubber ring; 5. Slope protection drainage layer; 6. Intelligent response water sealing layer. Detailed Implementation

[0039] To more clearly illustrate the overall concept of the present invention, a detailed description is provided below with reference to the accompanying drawings and examples.

[0040] In the description of this invention, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential" 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 this 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 this invention.

[0041] 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 technical features indicated. 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" means two or more, unless otherwise explicitly specified.

[0042] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0043] In this invention, unless otherwise expressly specified and limited, the first feature "on" or "below" the second feature may be in direct contact with the first and second features, or indirect contact through an intermediate medium. In the description of this specification, references to terms such as "an embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0044] Please refer to Figures 1 to 5 As shown in the figure, this embodiment introduces an intelligent response adaptive anchor support structure for expansive soil slopes. The support structure includes support anchors and slope protection structure. The support anchors include an anchor head 1, an anchor pressure relief device 2, an anchor free section 3, and an anchor anchoring section 4. The slope protection structure consists of an intelligent response water sealing layer 6 and a slope protection drainage layer 5 from the inside out.

[0045] like Figure 1 As shown, the intelligent responsive water-sealing layer 6 has a thickness of 200mm-300mm and is composed of SAP particles, bentonite, and sand. The SAP material is a polyacrylate superabsorbent resin with a particle size of 20-40 mesh and a water absorption ratio ≥300 times. The bentonite is sodium-based bentonite. The sand is clean medium-coarse sand with a mud content <3%. The dry weight percentages of each component are: SAP 0.8%-1.5%, bentonite 10%-15%, and the remainder is sand. The mixture is first dry-mixed, then water is added and compacted. When the slope encounters water, the rapid expansion of the SAP and the slow hydration of the bentonite work synergistically to form a dense gel that fills the pores in the surrounding sand skeleton, creating a dense hydrogel barrier layer. The permeability coefficient of this layer is ≤1×10⁻⁶. -8 The speed of the SAP (soil spray) is m / s, which enables rapid water sealing to prevent rainwater from seeping into the expansive soil. During dry periods, the SAP can slowly release water, slowing down the drying and cracking process of the expansive soil in the slope and preventing the formation of a large number of cracks in the expansive soil.

[0046] like Figure 2 As shown, the slope protection drainage layer 5 is assembled from EPS modules with mortise and tenon joints, with a density of 30 kg / m³. 3 The compressive strength is ≥150kPa. The EPS module size is 1000mm×2000mm, and the thickness is 50mm~100mm. The surface layer of the EPS block is set on the intelligent response water sealing layer 6 to realize the rapid drainage and leveling of the slope, and protect the intelligent response water sealing layer 6 from rainwater erosion. The EPS block is lightweight and has a low elastic modulus. It can absorb energy through its own small compression deformation to buffer the expansion deformation of the slope soil.

[0047] like Figure 3 As shown, the free section 3 and the anchoring section 4 of the anchor bolt are two functional zones of an integral structural rod body. The integral structural rod body is composed of the middle anchor bolt 301 of the free section 3 and the lower anchor bolt 401 of the anchoring section 4. The entire rod body is made of fully threaded glass fiber reinforced polymer rod or hot-dip galvanized fully threaded steel bar to increase the bonding strength.

[0048] The free section 3 of the anchor rod is located on the side of the rod body close to the slope surface and within the potential slip surface of the slope. It includes a middle anchor rod 301 and a water-swellable rubber sleeve 302 wrapped around the outside of the middle anchor rod 301. The water-swellable rubber sleeve 302 is firmly bonded to the rod body by epoxy resin adhesive to ensure that it will not slip or fall off during service.

[0049] The water-swellable rubber sleeve 302 is preferably made of high-strength water-swellable rubber with chloroprene rubber as the base material, with a volume expansion rate of not less than 150% and an expansion pressure of not less than 0.5MPa. Its initial outer diameter should be 10mm-20mm smaller than the designed borehole diameter to ensure that the rod can be smoothly installed to the bottom of the hole. When the expansive soil in the free section 3 of the anchor rod seeps water and expands, the water-swellable rubber in the free section also absorbs water and expands simultaneously, relieving the pressure of the expansive soil on the free section support anchor rod and reducing the shear expansion force of the expansive soil on the support anchor rod. When the expansive soil loses water, the water-swellable rubber slowly releases water to regulate the humidity of the expansive soil in the free section 3 of the anchor rod, and avoids the expansive soil from drying and shrinking too quickly, which can cause cracks and form rainwater infiltration channels.

[0050] Anchor bolt anchoring section 4 is the side of the bolt body that extends into the slope. It passes through the slip surface and is anchored to the stable soil and rock layer. As the core part of the final anchoring force of the support anchor bolt system, a water-swellable rubber ring 403 is set at intervals of 1.5m to 2m along the length of the bolt body to divide the anchor bolt anchoring section 4 into a series of segmented anchoring units 402. The specific number of segmented anchoring units 402 is determined according to the anchoring force determined by the earth pressure calculation.

[0051] The water-swellable rubber ring 403 has the same material and performance as the free section 3 sleeve of the anchor rod, with a volume expansion rate ≥150%. The axial length of the rubber ring should be 30cm to 50cm, and the initial outer diameter should be 10mm to 20mm smaller than the borehole diameter. During the grouting process, the water-swellable rubber ring 403 absorbs water and expands to form several independent pressure units, which greatly increases the grouting pressure. The grout squeezes and splits in the original cracks and shrinkage cracks of the expansive soil, forming root-like grout veins, which improves the mechanical interlocking force between the anchor rod anchoring section 4 and the surrounding soil. When the expansive soil in the anchor rod anchoring section 4 expands due to water seepage, the water-swellable rubber ring 403 in the anchor rod anchoring section 4 absorbs water and expands to apply a huge radial pressure to the borehole wall, generating additional frictional resistance on the rod body, thereby improving the anchoring force of the anchor rod anchoring section 4 and achieving the adaptive effect of "expansion to control expansion".

[0052] A primary grouting pipe and segmented grouting valve are pre-embedded inside the rod to ensure that each segmented anchoring unit 402 can be subjected to controllable pressure grouting.

[0053] like Figure 4 As shown, the anchor head 1 includes a locking nut 101 for transmitting the pre-tightening force of the support anchor, an anchor plate 102, and an upper anchor 103. The upper anchor 103 is a threaded design and is threadedly connected to the locking nut 101. The anchor plate 102 is a galvanized steel plate with dimensions of 300mm×300mm×20mm. Several Φ10 anti-slip teeth with a length of 20mm are welded to its bottom to enhance the anti-slip ability on the slope protection drainage layer 5, realize the effective diffusion of the support anchor stress, and prevent stress concentration from damaging the slope EPS board.

[0054] like Figure 4 , Figure 5 As shown, the anchor bolt pressure relief device 2 is an independent, pre-installable and calibrable functional module located between the anchor bolt head 1 and the anchor bolt free section 3; it includes a cylindrical connecting sleeve 201, with an axial force transmission rod 202 slidably connected inside the connecting sleeve 201. The axial force transmission rod 202 passes through the connecting sleeve 201 on the side near the anchor bolt head 1 and extends out of the connecting sleeve 201 to be threadedly connected to the upper anchor bolt 103;

[0055] A conical plug 203 is fixedly connected to the end of the axial force transmission rod 202 away from the upper anchor rod 103. The axial force transmission rod 202 transmits the tension from the upper anchor rod 103 to the conical plug 203. A friction assembly 206 is provided between the conical plug 203 and the connecting sleeve 201. The friction assembly 206 consists of three independent arc-shaped friction blocks 209 evenly distributed on the circumference. The inner conical surface of the friction block 209 and the outer conical surface of the conical plug 203 form a conical sliding pair. The outer surface and the inner wall of the connecting sleeve 201 form a variable friction pair. The conical plug 203 mainly converts the axial tension transmitted by the axial force transmission rod 202 into a huge radial expansion force on the friction assembly 206 through its conical surface. The taper ratio is essentially the amplification efficiency of the axial force to radial force conversion. The larger the taper, the higher the conversion efficiency, and the more sensitive the pressure threshold.

[0056] The anchor bolt pressure relief device 2 is designed as a fully sealed structure to prevent external mud and water from entering. The connecting sleeve 201 is made of seamless steel pipe, which has high strength, high toughness and excellent wear resistance. The hardness of the inner wall reaches HRC50 or above and the surface roughness is controlled between Ra0.4μm and 0.8μm, ensuring a stable and controllable coefficient of friction with the outer surface of the friction component 206. The conical plug 203 is made of high-strength wear-resistant alloy steel, and its outer conical surface taper ratio is 1:12 to 1:8 and the half-cone angle α≈4.8°~7.1°.

[0057] The friction block 209 base is made of high-quality alloy spring steel to ensure that it has sufficient elastic deformation capacity and fatigue strength under huge radial pressure; the outer surface is provided with a friction pad with high friction coefficient and high wear resistance. The pad is in close contact with the inner wall of the connecting sleeve 201, which has been hardened and finely ground. The design friction coefficient between the pad and the inner wall of the connecting sleeve 201 should be stable between 0.4 and 0.6; in a preferred embodiment of the present invention, the friction pad is preferably made of copper-based powder metallurgy pad.

[0058] The axial force transmission rod 202 is fixedly connected to a conical plug push plate 204 with an annular design at one end near the conical plug 203. The conical plug push plate 204 integrates a preload adjustment mechanism 208. The preload adjustment mechanism 208 uses multiple circumferentially distributed preload screws. These screws are screwed into the threaded holes of the conical plug push plate 204, and their ends directly press against the preload spring 207. By tightening the nut of the preload adjustment mechanism 208 with a torque wrench, the screwing depth of these screws can be precisely controlled, and a precise preload can be applied to the preload spring 207.

[0059] The preload spring 207 provides initial positive pressure to the friction assembly 206. By adjusting the preload of the preload spring 207, the initial static friction force between the friction assembly 206 and the inner wall of the sleeve can be precisely preset, realizing the pressure relief threshold of the pressure relief device. The preload spring 207 is pre-compressed between the preload adjustment mechanism 208 and the friction assembly 206, and a small cylindrical helical compression spring is evenly distributed circumferentially. To achieve high stability and long service life of the preload spring 207 under long-term operation, in a preferred embodiment of the present invention, the preload spring 207 is made of chromium vanadium steel or silicon manganese spring steel. After the spring is formed, it is subjected to shot peening and standing treatment in sequence.

[0060] A return spring 205 is provided at one end of the axial force transmission rod 202 near the upper anchor rod 103. One end of the return spring 205 is fixedly connected to the inside of the connecting sleeve 201, and the other end abuts against the cone plug push plate 204. It is a high-rigidity, fatigue-resistant cylindrical helical compression spring made of silicon manganese spring steel. When pressure relief occurs, the spring is further compressed. When the axial force decreases, the elastic potential energy stored in the spring is released, pushing the cone plug push plate 204 and the entire friction assembly 206 to reset.

[0061] The end of the connecting sleeve 201 away from the anchor head 1 is connected to the middle anchor 301 by a thread, thereby realizing the connection between the anchor pressure relief device 2 and the rod body;

[0062] In summary, the working process of the anchor bolt pressure relief device 2 is as follows:

[0063] Locking stage: When the support anchor is under tension, the axial force of the support anchor acts on the conical plug 203 through the upper anchor 103, causing the conical plug 203 to have an axial movement tendency; the conical surface of the conical plug 203 interacts with the inner conical surface of the friction block 209, causing the friction block 209 to press tightly against the inner wall of the connecting sleeve 201, generating static friction force; when the axial force of the support anchor is less than the pressure relief threshold generated by the preload spring 207, the friction pair is in a static friction state, and there is no relative movement between the friction component 206 and the connecting sleeve 201, realizing the rigid force transmission of the system.

[0064] Pressure relief stage: When the expansive soil expands and deforms, it is constrained by the support anchor rod. The expansive soil will generate expansion stress on the support anchor rod, increasing the axial force of the support anchor rod. When the axial force of the support anchor rod reaches the threshold, the friction pair breaks through the static friction force and enters the dynamic friction state. Relative sliding occurs between the friction component 206 and the connecting sleeve 201. At this time, the conical plug 203 moves relative to the friction component 206, but due to the design of the preload spring 207, its clamping force on the friction component 206 remains constant. Therefore, the dynamic friction force also remains constant, achieving constant resistance pressure relief.

[0065] Reset phase: When the expansive soil shrinks and deforms, the load on the support anchor decreases, and the axial force of the support anchor decreases synchronously. Under the action of the reset spring 205, the cone plug pusher 204 is pushed to move towards the middle anchor 301, which in turn drives the cone plug 203 to slide in the opposite direction along the cone surface of the friction component 206. The system returns to the initial geometric state, the friction pair returns to the static friction state, and the initial state is automatically restored.

[0066] like Figure 6 As shown, based on the above-mentioned support structure, this embodiment also provides a construction method for an intelligent response adaptive anchor support structure for expansive soil slopes, specifically including the following steps:

[0067] S1, Intelligent Response Water Sealing Layer 6 Construction: After the slope is excavated and trimmed, SAP granular bentonite and medium-coarse sand are dry-mixed according to the design ratio to ensure uniformity. Then, water is sprinkled to near the optimum moisture content for wet mixing. The mixture is transported to the slope surface and spread in layers with a loose thickness of no more than 150mm per layer. Flat plate vibration compaction is used to ensure that the compaction degree is not less than 90%, and finally an intelligent response water sealing layer 6 with a thickness of 200mm to 300mm is formed.

[0068] S2. Construction of slope protection and drainage layer 5: Assemble EPS modules with tenons and grooves, ensure that the tenons and grooves between the modules are tightly interlocked, form an integral slope protection and drainage layer 5, and implement drainage measures such as slope bottom ditches.

[0069] S3. Drilling construction: Drill holes on the slope according to the designed hole diameter (75mm~100mm), spacing (such as a 3m×3m square arrangement), angle (15°~20° downward angle) and hole depth. After drilling is completed, clean the hole thoroughly with high-pressure air.

[0070] S4. Anchor rod installation: Install the anchor rod with water-swellable rubber sleeve 302 on the free section 3 and several water-swellable rubber rings 403 spaced apart on the anchor rod anchoring section 4. The outer diameter of the water-swellable rubber sleeve 302 and the water-swellable rubber rings 403 is 10-20mm smaller than the borehole diameter. Before installing the anchor rod, it is advisable to insert a temporary sleeve into the borehole. After the anchor rod is installed in place, the sleeve should be pulled out before grouting to prevent the water-swellable rubber rings 403 from being scratched by the borehole wall during the installation process.

[0071] S5. Grouting Construction: Grouting is carried out from the grouting pipe at the bottom of the anchor rod to the bottommost segmented anchoring unit 402 through the primary grouting pipe and segmented grouting valves pre-embedded inside the rod body. The target grouting pressure is controlled between 1.5MPa and 3MPa. The grouting is carried out using a graded pressurization method, with the initial pressure at 0.5MPa, and then gradually increased to the target pressure in increments of 0.5MPa. The pressure is stabilized for 2 to 3 minutes at each pressure level, and the pressure change and grouting volume are observed.

[0072] When the grouting rate of the bottommost segmented anchoring unit 402 is less than 1L / min under the target grouting pressure and the pressure is maintained for at least 5 minutes, the grouting of the unit can be judged as qualified. After the grout has initially set and has a certain strength, the segmented grouting valve serving the previous unit is opened by hydraulic or mechanical means, and the graded pressurized grouting process is repeated. Grouting is carried out on each segmented anchoring unit 402 above it from bottom to top until the grouting construction of the entire anchoring section is completed.

[0073] S6. Installation and construction of anchor bolt pressure relief device 2:

[0074] In the factory, the reset spring 205, cone plug push plate 204, cone plug 203, friction assembly 206, preload spring 207, and preload adjustment mechanism 208 are assembled in the connecting sleeve 201. The preload adjustment mechanism 208 is used to adjust and lock the preload spring 207 to ensure that the pressure relief threshold of each anchor rod is strictly consistent with the design value. After calibration, the connecting sleeve 201 is sealed to form an independent anchor rod pressure relief device 2.

[0075] The middle anchor rod 301 is threadedly connected to the connecting sleeve 201. The anchor plate 102 is placed at the wellhead. The through hole of the anchor plate 102 is aligned with the axial force transmission rod 202. The upper anchor rod 103 is threadedly connected between the through hole of the anchor plate 102 and the axial force transmission rod 202. The locking nut 101 is rotated to press the anchor plate 102, thereby pressing the anti-slip teeth at the bottom of the anchor plate 102 tightly into the EPS board.

[0076] Connect the tensioning equipment to the upper anchor rod 103. The upper anchor rod 103 is tensioned in stages by the tensioning equipment. After each stage of tensioning, it is stabilized for 5 to 10 minutes. After the last stage of tensioning reaches the design preload, it is locked by locking nut 101, and then the overall construction is completed.

[0077] Specific implementation examples are as follows:

[0078] A certain expansive soil slope has a height of 8m and a designed slope ratio of 1:1.5. The slope soil is Quaternary residual (Q4el) clay, with an atmospheric influence depth of 3m and a free swelling rate of approximately 45%. The engineering properties of the slope soil are: bond strength C = 22kPa, internal friction angle φ = 16°, and soil weight γ = 19kN / m³. 3 The potential slip surface is buried at a depth of 3-4m, and the stable soil and rock layer is buried at a depth of about 4.5m. The slope is reinforced with anchor frame beams, but due to the large expansion deformation and shrinkage deformation, traditional anchors may face excessive prestress loss or failure due to the surge in anchor stress caused by soil expansion deformation. Therefore, an intelligent response adaptive anchor support structure for expansive soil slopes is adopted for slope protection.

[0079] The anchor spacing is designed to be 2.0m × 2.0m, with an anchor inclination angle θ = 20°. The anchor rods are made of HRB400 hot-dip galvanized fully threaded steel bars. Earth pressure calculations show that a single anchor rod can withstand an earth pressure of 127.8kN. The design load for a single anchor rod in this design is P = 150kN. The anchor rod diameter is d = 32mm, the borehole diameter is D = 100mm, and the preload coefficient is 0.6. The calculated free section length La = 7m. High-pressure splitting grouting combined with water-swellable rubber reinforcement is used. The bond strength of the anchoring section is taken as f. rb =220kPa, and the theoretical anchorage length calculated based on the anchor design load is 2.17m. After considering a safety factor of 1.8, the total length of the segmented anchorage unit 402 is 3.91m.

[0080] Three segmented anchoring units 402 are selected, each 1.5m long, with 0.5m intervals for water-swellable rubber rings 403. The actual anchoring section length Lb = 5.5m, and the total anchoring length L is: L = La + Lb = 12.5m. The design yield threshold is 0.6 times the anchor's yield strength, and not greater than 1.2 times the anchor's design load. Therefore, the design yield threshold P1 is: P1 = 0.6 × 3.14 × 16 2 ×360=173kN, and P1<1.2P=180kN;

[0081] To achieve the designed pressure threshold, the conical plug 203 is made of high-strength wear-resistant alloy steel, with a large end diameter of φ94mm, a small end diameter of φ64mm, and a conical surface length of 150mm. Its taper ratio is 1:10 (half-cone angle α=5.71°). The friction assembly 206 uses three friction blocks 209 made of high-strength alloy spring steel. The friction block 209 has an arc angle of 120°, a height of 70mm, and a chord length of 90mm. The friction pad is made of copper-based powder metallurgy and is bonded to the base of the friction assembly 206. The friction coefficient μ=0.5. Ignoring conical surface friction, the radial expansion force Fx of the conical plug 203 when the anchor rod is at the pressure relief threshold is: Fx = 173 × tan(α) = 17.3 kN. Then the radial positive pressure N1 of the conical plug 203 on a single friction block 209 is: N1 = 173 × tan(α) / 3 = 5.77 kN. When the anchor rod is at the critical state of the pressure relief threshold, the positive pressure N2 required by a single friction block 209 is: N2 = P1 / μ / 3 = 173 / 0.5 / 3 = 115.33 kN.

[0082] The preload spring 207 is made of three chromium vanadium spring steels, which are evenly distributed circumferentially in conjunction with the friction block 209. The spring stiffness Kp=400N / mm, the preload spring 207 has an outer diameter of 25mm, a wire diameter of 3mm, and a free length of 60mm. When the preload spring 207 is initially preloaded, the elastic force of the preload spring 207 acts on the friction block 209 through the cone plug push plate 204, generating an additional lever effect. Considering the initial preload mechanism of the preload spring 207, the preload static load coefficient C1≈1.5 is adopted for simplified calculation. The three friction blocks 209 of the friction assembly 206 act independently to form multi-point contact. The arc design makes the contact force more uniform and improves the effective friction coefficient. Considering the gain effect of the structural characteristics of the friction block 209, the multi-body structure gain coefficient C2≈1.6 is adopted for simplified calculation. Then, the preload force Fs that each preload spring 207 needs to provide is: Fs=(N2-N1)×tan(α) / (C1×C2)=(115.33-5.77)×0.1 / (1.5×1.6)=4.56kN. The total preload force Ft that the preload spring 207 needs to provide is: Ft=3×Fs=13.7kN. The compression amount of a single preload spring 207 is δ = 4.57 / 0.4 = 11.4 mm. When the anchor bolt pressure relief device 2 is processed in the factory, the preload spring 207 is compressed to 11.4 mm by turning the nut of the preload adjustment mechanism 208, so as to accurately achieve the set anchor bolt pressure relief threshold.

[0083] The return spring 205 is made of silicon manganese spring steel. The stiffness of the return spring 205 is Kp=500N / mm. The outer diameter of the return spring 205 is 55mm and the wire diameter is 8mm. The return load of the return spring 205 is calculated as 15% of the anchor rod pressure threshold. Then the return pressure Fr of the return spring 205 is: Fr=0.15×173=25.95kN. The corresponding pressure relief stroke S is: S=Fr / Kp=25.95×1000 / 500=51.9mm. The free length of the return spring 205 is 110mm and the pressure relief working length is 58mm (compression 52mm).

[0084] The axial force transmission rod 202 is made of alloy steel with a diameter of φ45mm and a total length of 320mm. The upper end is connected to the upper anchor rod 103 with an M42×2 fine thread, and the lower end is welded to the conical plug 203. The conical plug push plate 204 has an outer diameter of φ98mm and an inner diameter of φ50mm, and is clearance-fitted with the axial force transmission rod 202. Limiting devices are set at both ends and move together with the axial force transmission rod 202. The connecting sleeve 201 is made of No. 45 steel with an outer diameter of φ120mm, an inner diameter of φ100mm, a wall thickness of 10mm, and a total length of 220mm. The lower end is connected to the middle anchor rod 301 with an M60×3 fine thread.

[0085] The above components are precision machined and installed in the factory. After installation, verification tests are conducted on the pressure relief threshold, pressure relief stroke, and reset function. After passing the test, the two ends of the connecting sleeve 201 are sealed and then transported to the site for installation. After the overall on-site construction of the anchor rod is completed, tensioning is carried out with a preload of 90kN. Tensioning is carried out in stages, with each stage having a tension force of 30kN and a stabilization time of 5-10 minutes per stage.

[0086] After the expansive soil slope was protected using an intelligent response adaptive anchor support structure, the landslide soil pressure on the slope was 127.8 kN under normal use, which was less than the anchor design load of 150 kN. The preload spring 207 maintained an initial compression of 11.4 mm, and the friction pair was in a static friction state, with the system rigidly transmitting force. When the expansive soil pressure reached the design yield threshold of 173 kN, the friction pair broke through the static friction force and entered dynamic friction. The return spring 205 was compressed by 52 mm, achieving constant resistance yield and absorbing the soil pressure generated by the expansion deformation. When the expansive soil contracted, the axial force of the anchor decreased, and the return spring 205 released energy, pushing the system to reset, and the friction pair returned to the static friction state.

[0087] Finally, it should be noted that the above embodiments are merely examples for clearly illustrating the present invention and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A construction method for an intelligent response adaptive anchor support structure for expansive soil slopes, comprising support anchors and slope protection structures; The slope protection structure consists of an intelligent response water sealing layer (6) laid on the slope surface and a slope protection drainage layer (5) covering it from the inside out. The intelligent response water sealing layer (6) is made of SAP particles, bentonite and sand mixed and compacted. The slope protection drainage layer (5) is assembled from EPS modules with mortise and tenon structure. The support anchor bolt includes, in sequence, the anchor bolt head (1), the anchor bolt pressure relief device (2), the anchor bolt free section (3) and the anchor bolt anchoring section (4), and the anchor bolt free section (3) and the anchor bolt anchoring section (4) are integrally formed rod bodies; The anchor head (1) is connected to the rod body through the anchor pressure relief device (2). The anchor pressure relief device (2) includes a cylindrical connecting sleeve (201). An axial force transmission rod (202) is slidably connected inside the connecting sleeve (201). One end of the axial force transmission rod (202) passes through the connecting sleeve (201) and is threadedly connected to the upper anchor (103). The other end is fixedly connected to a conical plug (203). A friction assembly (206) consisting of three arc-shaped friction blocks (209) arranged in a ring is provided between the conical plug (203) and the connecting sleeve (201). The axial force transmission rod (202) is externally fixedly connected to a conical plug push plate (204) with an annular design. The conical plug push plate (204) integrates a preload adjustment mechanism (208) composed of multiple preload screws. A preload spring (207) is provided between the conical plug push plate (204) and three friction blocks (209). A return spring (205) is provided on the outside of the axial force transmission rod (202). The free section (3) of the anchor bolt is wrapped with a water-swellable rubber sleeve (302). The anchor bolt anchoring section (4) is provided with multiple water-swellable rubber rings (403) at equal intervals, thereby dividing the anchor bolt anchoring section (4) into multiple segmented anchoring units (402). The anchor head (1) includes a locking nut (101), an anchor plate (102) and an upper anchor (103). The anchor plate (102) is a galvanized steel plate with anti-slip teeth on the bottom. characterized in that The construction method of the intelligent response adaptive anchor support structure for expansive soil slopes includes the following steps: S1, Construction Intelligent Response Water Sealing Layer (6): Dry mix SAP particles, bentonite and medium-coarse sand in the design ratio, add water and mix, then spread in layers on the slope and compact. S2, Assemble the slope protection and drainage layer (5): Assemble the EPS module with tenon groove on the intelligent response water sealing layer (6); S3. Drilling and cleaning the hole; S4. Rod installation: Install the support anchor rod with water-expandable rubber sleeve (302) and water-expandable rubber ring (403) spaced out into the borehole; S5. Segmented Pressure Grouting: Through the grouting pipe at the bottom of the anchor rod and the segmented grouting valve, each segmented anchoring unit (402) is subjected to graded pressure grouting from bottom to top, as follows: The graded pressurization method first sets the initial pressure, and then gradually increases the pressure to the target pressure according to the set pressure value. When the grouting rate is less than the threshold at the target pressure, the grouting work is completed after stabilizing the pressure. S6. Install the anchor bolt pressure relief device (2) and the anchor bolt head (1), and perform tensioning and locking as follows: Pre-installation: At the factory, the return spring (205), cone plug push plate (204), cone plug (203), friction assembly (206), preload spring (207), and preload adjustment mechanism (208) are assembled in the connecting sleeve (201). The preload spring (207) is adjusted and locked by the preload adjustment mechanism (208) to ensure that the pressure relief threshold of each anchor rod is strictly consistent with the design value. After calibration, the connecting sleeve (201) is sealed to form an independent anchor rod pressure relief device (2). Anchor bolt pressure relief device (2) installation: The middle anchor bolt (301) is threadedly connected to the connecting sleeve (201), the anchor plate (102) is placed at the wellhead, the upper anchor bolt (103) is threadedly connected between the through hole of the anchor plate (102) and the axial force transmission rod (202), and the locking nut (101) is rotated to squeeze the anchor plate (102). Pressure locking: Connect the tensioning equipment to the upper anchor rod (103), tension in stages, stabilize for 5-10 minutes after each stage of tensioning, and finally lock by tightening the lock nut (101).

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