Detachable anchor rod applied to tunnel in-situ extension and supporting method of detachable anchor rod

Abstract

The detachable anchor rod comprises a detachable section anchor rod body and an anchoring section anchor rod body, the anchoring section anchor rod body is provided with a first umbrella framework fixedly connected and a second umbrella framework movably connected, the first umbrella framework is fixedly supported at a first anchoring point, and the second umbrella framework is fixedly supported at a second anchoring point. The second umbrella framework is fixedly supported at a second anchoring point, the first umbrella framework can provide end anchoring force for the anchor rod, prestress can be conveniently and rapidly applied to the anchor rod, and the second umbrella framework can effectively control springback of the anchor rod and reduce prestress loss of the anchoring section of the anchor rod after the detachable section rod body and the base plate are detached. Meanwhile, the first umbrella framework and the second umbrella framework are embedded into the surrounding rock in the opposite opening directions to form a force matrix, deformation of surrounding rock soil caused by factors such as humidity changes can be effectively resisted, the detachable section of the anchor rod can be detached and reused before tunnel expanding excavation, and the construction cost is reduced. The construction cost is reduced, and the economic cost is saved.

Description

Technical Field

[0001] The invention relates to the field of tunnel engineering, in particular to a detachable anchor rod used for in-situ expansion of a tunnel and a supporting method thereof. Background Art

[0002] With the increasing number of cars, many existing roads can no longer meet the growing traffic demand, so it is necessary to widen existing roads and expand tunnels. When expanding tunnels in situ, the traditional method is to "backfill first, then excavate", but this method has prominent problems such as poor economic effect and long construction period; anchor support, as a major rock and soil reinforcement technology, can improve the bearing capacity of rock and soil, give full play to the self-bearing capacity of rock and soil, and is widely used in geotechnical engineering, tunnel engineering, slope engineering and other projects. With the development of society, the construction of rock and soil in some engineering construction has shown diversity and complexity, and it is necessary to construct the rock and soil in sections and stages. In order to cooperate with the construction of rock and soil, detachable anchors are born. Existing detachable anchors mostly establish the interaction between the surrounding rock and the anchor through grouting, and then achieve the support effect. However, the existing grouting materials usually have problems such as long setting time and easy aging. On the one hand, they cannot provide support in time after the excavation of the rock and soil, resulting in aggravated deterioration of the surrounding rock. On the other hand, the resulting durability problems have a great impact on the structure that requires the anchor to serve for a long time. If anchor rods are used for prestressed active support, after the detachable section of the detachable anchor rod is removed, the problem of prestress loss in the remaining part becomes prominent. Summary of the invention

[0003] The present invention provides a detachable anchor rod and a supporting method thereof for in-situ expansion of a tunnel. Firstly, the detachable anchor rod comprises an anchoring section and a detachable section. During construction, an anchor rod hole is drilled on the lining of the original tunnel toward the depth of the surrounding rock of the expanded tunnel, the anchoring section of the anchor rod is pushed and placed at an anchoring point deep in the surrounding rock of the expanded tunnel, and the junction of the anchoring section and the detachable section is placed on the excavation contour line of the expanded tunnel. After the anchor rod is tensioned and a pad and a nut are stably installed at the tail end of the detachable section of the anchor rod, the surrounding rock and the tunnel lining between the contour of the newly-built tunnel and the existing tunnel are excavated step by step, and the detachable section is removed for grouting, and then the pad and the nut are fixed to the bottom end of the anchoring section to support the outer wall of the surrounding rock of the excavated tunnel, and then the lining structure of the expanded tunnel is constructed, so that the tunnel expansion construction can be completed. In the entire construction process, the tunnel expansion is avoided by adopting the construction method of "backfilling first and then excavating", which not only controls the economic cost but also shortens the construction period.

[0004] Secondly, compared with traditional detachable anchor rods, the anchoring section of the anchor rod of the invention is provided with a first umbrella frame and a second umbrella frame. After the first umbrella frame and the second umbrella frame are placed at the first anchor point and the second anchor point respectively, prestress is applied step by step through cyclic tensioning and rebound, so that the first umbrella frame opens downward and the umbrella tip of the first umbrella frame drills into the surrounding rock of the anchor hole channel, and the umbrella ribs of the second umbrella frame open upward and the umbrella tip of the second umbrella frame drills into the surrounding rock of the anchor hole channel, so as to fix the anchor rod in the surrounding rock anchor hole of the expanded tunnel, thereby achieving timely support effect after the expansion and excavation of the surrounding rock soil, and avoiding the aggravation of surrounding rock deterioration.

[0005] At the same time, the first umbrella frame and the second umbrella frame are firmly connected with the anchor rod and the surrounding rock. The second umbrella frame is firmly fixed at the second anchor point under the joint action of the sawtooth structure and the anchor rod prestress. The anchor rod body can only move unidirectionally in the direction of the existing tunnel contour under the restriction of the second sleeve, the second umbrella frame and the sawtooth structure, which can effectively control the rebound of the anchor rod and reduce the loss of prestress of the anchor rod anchoring section caused by the loss of the restraining effect of the tail end pad of the detachable section of the anchor rod when the detachable section of the anchor rod is removed, so that the prestress of the anchor rod anchoring section can be maintained throughout the construction process, the supporting effect of the prestress on the peripheral rock of the expanded tunnel is relatively stable, and the self-stabilizing ability and self-bearing capacity of the peripheral rock of the expanded tunnel are improved; and the anchor rod anchoring section can be tensioned for the second time after the tunnel is expanded to compensate for the prestress loss caused during the expansion process, thereby ensuring the stability and supporting capacity of the anchor rod; furthermore, the first umbrella frame and the second umbrella frame are both made of metal materials and wrapped with grouting materials, so that they are not easy to age and can be used for a long time, which can meet the durability requirements of the support structure of the long-term service tunnel.

[0006] In addition, the first umbrella frame opens downward under the action of tension, and the second umbrella frame opens upward. The reverse forces generated by the opening of the two umbrella frames can interact with each other to jointly resist the pull-out force of the anchor rod, reducing the risk of instability caused by external loads or geological changes; at the same time, the interaction between the first umbrella frame and the second umbrella frame forms a symmetrical load dispersion structure. When external forces or surrounding rock deformations occur, this dispersion mechanism allows the forces to act on the surrounding rock in different directions, reducing the peak stress directly borne by the anchor rod. The advantage of this design is that the disturbance to the anchor rod is reduced during the process of tunnel expansion, which can ensure that the anchor rod always remains in an effective anchoring state and provide stable support capabilities for the surrounding rock tunnel.

[0007] In a first aspect, the present application provides a detachable anchor rod for in-situ tunnel expansion, comprising an anchor rod, the anchor rod comprising an anchoring section and a detachable section, the anchoring section and the detachable section being threadedly connected, the anchoring section being located in an anchor hole channel above the excavation contour line of the expansion tunnel, and the detachable section being located in the anchor hole channel below the excavation contour line of the expansion tunnel;

[0008] The anchoring section is provided with a first umbrella frame, a buckle and a second umbrella frame in sequence, and the second umbrella frame is located inside the opening of the anchor hole channel above the excavation contour line of the expansion tunnel;

[0009] The first umbrella frame is fixedly connected to the top of the anchoring section, and the first umbrella frame is in a closed state under the restriction of the anchor hole channel. When the first umbrella frame reaches the first anchoring point and applies tension to the anchor rod, the first umbrella frame opens with the opening downward and penetrates into the surrounding rock where the anchor hole channel is located;

[0010] The buckle is fixedly connected to the middle section of the anchoring section and is buckled with the second umbrella frame. When a tensioning force is applied to the anchor rod, the buckle is deformed to release the second umbrella frame.

[0011] The second umbrella frame is movably connected to the anchoring section and is in a closed state when the buckle is buckled. When the buckle is deformed to loosen the second umbrella frame, the second umbrella frame opens with the opening facing upward and penetrates into the surrounding rock of the second anchoring point in the anchor hole channel.

[0012] As a further solution of the present invention, the first umbrella frame is fixedly connected to the end of the top end of the anchoring section through the first sleeve, and the second umbrella frame is movably connected to the anchoring section through the second sleeve.

[0013] As a further solution of the present invention, the anchoring section is also provided with a sawtooth structure with the tooth tip facing upward. The anchoring section and the sawtooth structure are an integrally formed structure. A second sleeve is sleeved on the sawtooth structure. The second sleeve can only move in one direction toward the top of the anchoring section under the restriction of the sawtooth structure.

[0014] As a further solution of the present invention, the first umbrella frame includes a first umbrella rod, a second umbrella rod, a first spring and a slider;

[0015] The slider is slidably connected to the middle section of the outer wall of the first sleeve and is hinged to one end of the first umbrella rod. The other end of the first umbrella rod is hinged to the middle part of the second umbrella rod. One end of the second umbrella rod is hinged to the top of the outer wall of the first sleeve. The other end of the second umbrella rod is a pointed cone structure.

[0016] A first spring is fixedly connected between the first umbrella rod and the outer wall of the first sleeve.

[0017] As a further solution of the present invention, the second umbrella frame includes a third umbrella rod, a fourth umbrella rod, a second spring and a fifth umbrella rod;

[0018] One end of the third umbrella rod is hinged to the middle part of the outer wall of the second sleeve, and the other end of the third umbrella rod is hinged to one end of the fourth umbrella rod, and the other end of the fourth umbrella rod is hinged to the middle part of the fifth umbrella rod, one end of the fifth umbrella rod is hinged to the bottom of the outer wall of the second sleeve, and the other end of the fifth umbrella rod is a pointed cone structure;

[0019] The second spring is fixedly connected between the third umbrella rod and the fourth umbrella rod.

[0020] As a further solution of the present invention, at least two first umbrella frames are arranged around the first sleeve, and at least two second umbrella frames are arranged around the second sleeve.

[0021] As a further solution of the present invention, the buckle includes a pull rod, a buckle fixing block and a buckle sliding block;

[0022] The buckle fixing block is provided with a groove, the buckle fixing block is fixed on the anchoring section, and the buckle sliding block is slidably connected in the groove;

[0023] One end of the pull rod is fixedly connected to the anchoring section, and the other end is fixedly connected to the buckle sliding block, so as to control the buckle sliding block to be limited to slide in the groove.

[0024] As a further solution of the present invention, the detachable section includes a plurality of anchor rod detachable sections, and each anchor rod detachable section is connected by threads;

[0025] In the detachable section, the thread tightening direction of the anchor rod detaching section directly connected to the anchoring section is opposite to the thread tightening direction between the remaining anchor rod detaching sections.

[0026] As a further solution of the present invention, the anchor rod further comprises a nut and a washer, and the nut and the washer are sleeved on the tail ends of the anchoring section and the detachable section.

[0027] In the second aspect, the present application example also provides a support method for in-situ expansion of a tunnel based on the above-mentioned detachable anchor rod, which comprises the following steps:

[0028] S1: According to the design parameters of the anchor bolts for the expanded tunnel, anchor bolt holes are drilled on the lining of the original tunnel towards the depth of the surrounding rock of the expanded tunnel;

[0029] S2: closing the first umbrella frame and the second umbrella frame, pushing the second umbrella frame to the buckle to buckle, and pushing the anchor rod to a designated position in the anchor hole;

[0030] S3: Install nuts and gaskets at the tail end of the removable section;

[0031] S4: The anchor rod is tensioned, unloaded, and tensioned again, with loading and unloading cycles, and tension force is applied step by step to slowly increase the prestress value of the anchor rod until the designed prestress value is reached; the first umbrella frame is opened under the tension load to drive the tip of the second umbrella rod to penetrate into the surrounding rock; the restrictive effect of the buckle on the second umbrella frame gradually disappears under the tension load until the second umbrella frame is separated from the buckle and opens; in the unloading stage, the second umbrella frame is affected by the rebound deformation of the anchor section, and drives the tip of the fifth umbrella rod to penetrate into the surrounding rock of the second anchor point;

[0032] S5: After the surrounding rock and anchor bolts are stabilized, remove the removable segments, nuts and pads, and excavate the surrounding rock and tunnel lining between the expanded tunnel outline and the existing tunnel;

[0033] S6: tension the anchoring section again to compensate for the prestress loss caused during the excavation process, and perform grouting after tensioning is completed;

[0034] S7: Install the pad and nut to the end of the anchoring section, then construct the expanded tunnel lining structure to complete the construction.

[0035] In summary, the present invention has the following beneficial effects compared with the prior art:

[0036] (1) The anchor rod of the present invention is a detachable anchor rod. During the construction process, an anchor hole can be directly drilled in the existing tunnel to the depth of the surrounding rock of the expanded tunnel. The detachable anchor rod is placed in the anchor hole to provide support for the tunnel surrounding rock. After the detachable section of the anchor rod is removed step by step and the corresponding part of the rock and soil is excavated, grouting is performed and the pad and nut are installed. Finally, the tunnel lining structure is constructed. The entire construction process avoids the use of the "backfill first, then excavation" construction method to expand the tunnel, which not only controls the economic cost but also shortens the construction period.

[0037] (2) The anchoring section of the anchor rod of the present invention is provided with a first umbrella frame and a second umbrella frame. After the anchoring section is placed deep in the surrounding rock of the expanded tunnel, prestress is applied step by step through cyclic tensioning and unloading, so that the umbrella ribs of the first umbrella frame and the second umbrella frame are opened and drilled into the surrounding rock soil layer, so as to fix the anchor rod in the surrounding rock anchor hole of the expanded tunnel to provide support, thereby achieving timely support effect after the rock and soil body is excavated, avoiding the aggravation of the surrounding rock deterioration.

[0038] (3) After the second umbrella frame is embedded in the surrounding rock, the anchor rod can only move in one direction toward the existing tunnel contour under the restriction of the second umbrella frame and the sawtooth structure, which can effectively control the rebound of the anchor rod and reduce the loss of prestress in the anchor rod anchoring section caused by the loss of the restraining effect of the rear end pad of the detachable section when the detachable section of the anchor rod is removed. The prestress of the anchor rod anchoring section can be maintained throughout the construction process, and the support effect of the prestress on the surrounding rock of the expanded tunnel is relatively stable, thereby improving the self-stabilizing ability and self-bearing capacity of the surrounding rock of the expanded tunnel.

[0039] (4) The anchoring section of the anchor bolt can only move in the direction of the existing tunnel contour under the restriction of the second umbrella frame and the sawtooth structure. After the tunnel is expanded and before the anchor bolt is grouted, the anchoring section of the anchor bolt can be tensioned for the second time to compensate for the prestress loss caused by the expansion process, thereby ensuring the stability and support capacity of the anchor bolt.

[0040] (5) The opening directions of the first umbrella frame and the second umbrella frame of the anchor rod of the present invention are opposite, so that the supporting directions are opposite. The conventional anchor rods with the same opening directions of the umbrella frames lack the supporting force to constrain the surrounding rock in the opposite direction. When the surrounding rock is subjected to an external force opposite to the supporting direction of the anchor rod, the surrounding rock is prone to deformation and instability. The anchor rod of the present invention can withstand the external force of the surrounding rock in the opposite direction. The first umbrella frame and the second umbrella frame are embedded in their respective positions with opposite opening directions so that the two form a force matrix. The existence of the first umbrella frame can effectively resist the sinking phenomenon of the surrounding rock soil caused by factors such as humidity changes. The existence of the second umbrella frame can effectively withstand and disperse the rock and soil pressure from above the surrounding rock, avoiding uneven deformation caused by upper and lower loads.

[0041] (6) Both the first umbrella frame and the second umbrella frame are made of metal materials and are wrapped with grouting materials, so that they are not easy to age and can be used for a long time, and can meet the durability requirements of the support structure of long-term service tunnels. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0043] Figure 1 is a schematic diagram of the structure of a detachable anchor rod;

[0044] Figure 2 is a schematic structural diagram of a first umbrella frame;

[0045] Figure 3 is a schematic diagram of the structure of the second umbrella frame and buckle;

[0046] Figure 4 It is a schematic diagram of the structure of the buckle fixing block and the buckle sliding block;

[0047] Figure 5 This is a schematic diagram of the anchor rod being placed into the anchor hole;

[0048] Figure 6 This is a schematic diagram after the anchor bolt is installed;

[0049] Figure 7 This is a schematic diagram of the detachable section of the anchor bolt after removal;

[0050] Figure 8 This is a schematic diagram showing the excavation of the tunnel soil to be excavated and the completion of the anchor grouting construction;

[0051] Fig. 9 Schematic diagram of the construction process of removable anchor rods in the in-situ expansion of the tunnel.

[0052] The accompanying drawings are marked as follows:

[0053] 1-anchoring section; 2-detachable section; 3-first umbrella frame; 4-second umbrella frame; 5-buckle; 6-first sleeve; 7-second sleeve; 8-serrated structure; 9-first umbrella rod; 10-second umbrella rod; 11-first spring; 12-slider; 13-third umbrella rod; 14-fourth umbrella rod; 15-second spring; 16-fifth umbrella rod; 17-pull rod; 18-buckle fixing block; 19-buckle sliding block; 20-nut; 21-pad. DETAILED DESCRIPTION

[0054] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0055] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0056] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0057] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0058] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0059] In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of the present invention.

[0060] In the following description, suffixes such as "module", "component", "assembly" or "unit" are used only to facilitate the description of the present invention and have no specific meanings. Therefore, they can be used in combination.

[0061] The present invention will be further described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0062] According to one embodiment of the invention, Figures 1 to 8 As shown, a detachable anchor rod used for in-situ expansion of a tunnel comprises:

[0063] An anchor rod, the anchor rod comprising an anchoring section 1 and a detachable section 2, the anchoring section 1 and the detachable section 2 being threadedly connected, the anchoring section 1 being located in an anchor hole channel above the excavation contour line of the expansion tunnel, and the detachable section 2 being located in an anchor hole channel below the excavation contour line of the expansion tunnel;

[0064] The anchoring section 1 is provided with a first umbrella frame 3, a buckle 5 and a second umbrella frame 4 in sequence, and the second umbrella frame 4 is located inside the opening of the anchor hole channel above the excavation contour line of the expansion tunnel;

[0065] The first umbrella frame 3 is fixedly connected to the top of the anchoring section 1. The first umbrella frame 3 is in a closed state under the restriction of the anchor hole channel. When the first umbrella frame 3 reaches the first anchoring point and applies a tensioning force to the anchor rod, the first umbrella frame 3 opens with the opening facing downward and penetrates into the surrounding rock where the anchor hole channel is located.

[0066] The buckle 5 is fixedly connected to the middle section of the anchoring section 1 and is buckled with the second umbrella frame 4. When a tensioning force is applied to the anchor rod, the buckle 5 is deformed to release the second umbrella frame 4.

[0067] The second umbrella frame 4 is movably connected to the anchoring section 1 and is in a closed state when the buckle 5 is engaged. When the buckle 5 is deformed to release the second umbrella frame 4, the second umbrella frame 4 opens with its opening facing upward and penetrates into the surrounding rock of the second anchoring point in the anchor hole channel.

[0068] In traditional in-situ tunnel expansion, the idea of ​​"backfill first, then excavate" is often adopted. In this method, the existing tunnel is backfilled before expansion, and the backfill soil is excavated during construction. The preparation, transportation and construction of the backfill soil cause poor economic benefits and long construction period. The emergence of detachable anchor rods makes it possible to get rid of the idea of ​​"backfill first, then excavate" and use "external anchors" instead of "internal supports" as a new in-situ expansion idea. Most of the existing traditional anchor rods do not have an umbrella skeleton structure to support the anchoring. The anchor end is usually fixed by grouting. The anchor rod can only play a supporting effect or apply prestress after the slurry solidifies, resulting in it being unable to provide support in time after the rock and soil are excavated to prevent the surrounding rock from deteriorating. After some of the improved anchor rods, although the anchor rods There are umbrella skeleton structures or claw structures for supporting anchoring, but they are mostly set at the end of the anchor rod to quickly provide end anchor force for the anchor rod. When the detachable anchor rod and pad are removed for tunnel expansion, the anchor rod support effect is weakened and the prestress loss problem is prominent; although a small number of anchor rods use umbrella skeleton structures or claw structures to replace the restraining effect of the pad, their skeleton structures or claw structures are relatively large, usually set at the exposed end of the anchor rod, and are mostly used in coal mining and small clearance tunnel construction to reinforce rock pillars, rock walls, partition walls, and coal pillars; in addition, the umbrella skeleton structure supporting anchoring on the existing anchor rod has a single supporting direction and lacks the supporting force to reversely restrain the surrounding rock. When the surrounding rock is subjected to external force in the opposite direction of the anchor rod support, the surrounding rock is prone to deformation and instability.

[0069] The inventor of the present application provides a detachable anchor rod for in-situ expansion of tunnels. During construction, anchor rod holes are drilled on the lining of the original tunnel toward the depth of the surrounding rock of the expanded tunnel, and the anchoring section 1 of the anchor rod is pushed to the anchoring point deep in the surrounding rock of the expanded tunnel, and the junction of the anchoring section 1 and the detachable section 2 is placed on the excavation contour line of the expanded tunnel. After the anchor rod is tensioned, the pad 21 and the nut 20 are stably installed at the tail end of the detachable section 2 of the anchor rod, the detachable section 2 of the anchor rod is dismantled step by step and the surrounding rock and tunnel lining between the corresponding part of the new tunnel contour and the existing tunnel are excavated, and then the anchoring section 1 is grouting, and then the pad 21 and the nut 20 are fixed to the bottom end of the anchoring section to support the outer wall of the surrounding rock of the excavated tunnel, and then the lining structure of the expanded tunnel is constructed to complete the tunnel expansion construction. In the entire construction process, the tunnel expansion is avoided by adopting the construction method of "backfilling first and then excavating", which not only controls the economic cost but also shortens the construction period.

[0070] The inventors of the present application have found that the detachable anchor rod with the opening direction of the supporting skeleton is stronger in supporting capacity and better in supporting effect than the ordinary detachable anchor rod or the existing detachable anchor rod with a single supporting skeleton, and can be better applied to the in-situ expansion project of the tunnel; the ordinary detachable anchor rod adopts grouting to fix the end, and provides the end anchoring force for the anchor rod after the slurry solidifies, and cannot provide support in time after the rock and soil mass is excavated. For tunnels with poor rock mass, it is impossible to effectively prevent the aggravation of the surrounding rock deterioration, and after the rod body and the pad of the detachable section anchor rod are removed, the end constraint of the anchor section is released, and the anchor section is not affected by the deformation of the surrounding rock. The limiting capacity is weakened, and after the pad is removed, the rebound of the anchor rod causes the prestress loss problem to be prominent, and the prestress of the anchor rod body is difficult to effectively diffuse into the rock mass, and the supporting capacity for the surrounding rock is weakened; there are few detachable anchor rods with umbrella frame structure or claw structure, and the only few detachable anchor rods with umbrella frame structure or claw structure, detachable refers to the umbrella frame structure or claw structure, which is obviously different from the detachable structure and use mentioned in this application, and is mostly used in coal mining and small clearance tunnel construction to reinforce rock pillars, rock walls, partition walls, and coal pillars, and the application purposes are also different.

[0071] The inventor innovatively designed a detachable anchor rod with the support direction opposite to that of the supporting skeleton. During the anchoring construction stage, the anchor rod is cyclically tensioned and unloaded. When the prestress is applied step by step, the first umbrella skeleton 3 is rapidly opened downward under the tensioning force, directly embedded in and anchored in the surrounding rock, fixing the top of the anchoring section 1 and effectively diffusing the tensioning load; the buckle 5 releases the second umbrella skeleton 4 under the tensioning load, and the second umbrella skeleton 4 is opened upward and embedded in the surrounding rock under the action of the rod body rebounding during the unloading stage, locking the prestress of the anchor rod of the anchoring section and effectively diffusing it to the surrounding rock above. The prestress of the anchoring section 1 is locked by the second umbrella skeleton 4, and the The prestress of the disassembly section 2 is locked by the nut 20 and the pad 21 at its tail end; during the disassembly stage of the detachable section 2, the rod body loses the restraining effect of the nut 20 and the pad 21, and rebounds and deforms under the action of prestress, and the second umbrella frame 4 can effectively restrain the rebound deformation of the anchor rod under the restriction of the unidirectional sliding of the sawtooth structure 8, thereby reducing the problem of prestress loss after the dismantling of the detachable section 2, so that the prestress of the anchoring section of the anchor rod can be maintained throughout the entire construction process, the supporting effect of the prestress on the outer rock of the expansion tunnel is relatively stable, the self-stabilizing ability and self-bearing capacity of the outer rock of the expansion tunnel are improved, and the safety of the expansion construction is guaranteed. In addition, the first umbrella frame 3 and the second umbrella frame 4 are embedded in their respective positions with opposite opening directions so that the two form a force matrix. The first umbrella frame 3 is fixedly connected to the top of the anchoring section 1 through the first sleeve 6, which can effectively resist the sinking of the surrounding rock soil due to factors such as humidity changes. The sawtooth structure 8 fixes the second sleeve 7, thereby firmly fixing the second umbrella frame 4 at the second anchoring point to prevent the second umbrella frame 4 from sliding toward the detachable section 2, so that the second umbrella frame 4 can effectively withstand and disperse the rock and soil pressure from above the surrounding rock, avoiding uneven deformation caused by the upper load. Therefore, during the tunnel expansion process, whether it is the up and down movement of the stratum or the pressure change caused by the external load, it will be timely and effectively anchored and resisted by the bidirectional anchoring of the anchor rod, which can more effectively resist the up and down movement of the surrounding rock.

[0072] At the same time, the first umbrella frame 3 can significantly improve the pull-out resistance of the anchor rod through mechanical engagement with the rock mass, and can quickly apply prestress before grouting. The function of the second umbrella frame 4 is also to limit the movement of the anchor section 1 rod body only in the direction of the existing tunnel contour. After the tunnel is expanded and before the anchor rod is grouting, the anchor section 1 of the anchor rod can be tensioned for the second time to compensate for the prestress loss caused during the expansion process.

[0073] In addition, in the present embodiment, the second umbrella frame 4 can only slide on the anchor rod in one direction toward the buckle 5. The function of the buckle 5 is to fix the second umbrella frame 4 when the anchor rod has not reached the preset position during the pushing process of the anchor rod, so as to prevent the second umbrella frame 5 from automatically opening and penetrating into the surrounding rock when the anchor rod has not reached the preset position. At the same time, after the anchor hole is grouted, the buckle 5 is fixed in the anchor agent and can also play a certain anchoring role.

[0074] As a further embodiment of the present invention, Figure 1 As shown, the first umbrella frame 3 is fixedly connected to the end of the top end of the anchoring section 1 through a first sleeve 6, and the second umbrella frame 4 is movably connected to the anchoring section 1 through a second sleeve 7.

[0075] In this embodiment, the first sleeve 6 fixedly connects the first umbrella frame 3 and the top end of the anchoring section 1. The advantage of this is that when the anchor rod is tensioned, the top of the anchoring section 1 can stably withstand the tension, ensuring the firmness and reliability of the anchor rod; at the same time, the second sleeve 7 enables the second umbrella frame 4 to be movably connected to the anchoring section. Before the anchor rod is placed into the anchor hole channel, the second sleeve 7 can be pushed to drive the second umbrella frame 4 to move upward to the buckle 5 for buckling, ensuring that the second umbrella frame 4 maintains a stable closed state when the anchor rod is pushed.

[0076] As a further embodiment of the present invention, Figure 1 As shown, the anchoring section 1 is further provided with a sawtooth structure 8 with the tooth tip facing upwards, the anchoring section 1 and the sawtooth structure 8 are an integrally formed structure, and the second sleeve 7 is sleeved on the sawtooth structure 8 .

[0077] In this embodiment, the sawtooth structure 8 is preferably designed to have multiple rows of unidirectional sawtooth bars arranged circumferentially along the anchoring section 1 with the tooth tips facing upward, and the multiple rows of unidirectional sawtooth bars are arranged along the axial gap of the anchor rod. The inner wall of the second sleeve 7 is provided with tooth groove bars connected to the multiple rows of unidirectional sawtooth bars as a reference, and the second umbrella frame 4 is pushed to the buckle 5 for buckling by applying a thrust; or, in a geological environment with a slightly soft soil structure, the sawtooth structure 8 can also be designed to have multiple rows of unidirectional sawtooth rings arranged circumferentially along the anchoring section 1 with the tooth tips facing upward, and each sawtooth The rings are arranged at intervals along the circumference of the anchor rod, and the inner wall of the second sleeve 7 is provided with a tooth groove ring that is connected with multiple unidirectional sawtooth rings as a reference. The second umbrella frame 4 is pushed to the buckle 5 for buckling by applying a thrust. Since the ring-shaped sawtooth structure 8 has more tooth tips than the strip-shaped sawtooth structure 8, it has more support points and more support force, which can provide a stronger support force for the second sleeve 7. In a geological environment with a soft soil structure, the force borne by the anchor rod is dispersed by increasing the support points, and the stable support of the anchor rod is improved in this way;

[0078] Before placing the anchor rod into the anchor hole, the second sleeve 7 needs to be pushed to the buckle 5 for buckling. The one-way tooth design of the sawtooth structure 8 allows the second sleeve 7 to slide only in the direction of the buckle 5, ensuring that the second umbrella frame 4 will not suddenly open and hinder the delivery of the rod before the anchor rod is sent into the anchor hole channel and does not reach the designated position; at the same time, the one-way concave-convex tooth groove design of the sawtooth structure 8 can effectively maintain the overall structural stability of the second umbrella frame 4, so that after the second sleeve 7 reaches the designated position, even if the buckle 5 releases the second sleeve 7, the second sleeve 7 can be fixed in the tooth groove and cannot continue to move when maintained at the current designated position, thereby allowing the second umbrella frame 4 to be stably anchored at the second anchor point.

[0079] As a further embodiment of the present invention, Figure 2 As shown, the first umbrella frame 3 includes a first umbrella rod 9, a second umbrella rod 10, a first spring 11 and a slider 12;

[0080] The slider 12 is slidably connected to the middle section of the outer wall of the first sleeve 6 and is hinged to one end of the first umbrella rod 9. The other end of the first umbrella rod 9 is hinged to the middle part of the second umbrella rod 10. One end of the second umbrella rod 10 is hinged to the top of the outer wall of the first sleeve 6. The other end of the second umbrella rod 10 is a pointed cone structure.

[0081] The first spring 11 is fixedly connected between the first umbrella rod 9 and the outer wall of the first sleeve 6 .

[0082] In this embodiment, the slider 12 is arranged in the slide groove of the first sleeve 6, the fixed end of the second umbrella rod 10 is hinged to the hinge seat of the first sleeve 6, and the first umbrella rod 9 serves as the hinged component of the slider 12 and the second umbrella rod 10. Such a design allows the second umbrella rod 10 to rotate freely relative to the first sleeve 6 during the construction process. During the construction process, the deformation of the surrounding rock is unpredictable. The sliding connection between the slider 12 and the first sleeve combined with the hinge connection of the slider 12 and the second umbrella rod 10 can allow the first umbrella frame 3 to be properly adjusted according to the actual changes of the surrounding rock. By applying a suitable tensioning force, the second umbrella rod 10 is adjusted to insert the surrounding rock in a suitable opening direction and opening angle; furthermore, the hinged connection between the second umbrella rod 10 and the first umbrella rod 9 and the first sleeve 6 forms a multi-point support structure, which can flexibly disperse stress when subjected to force, thereby improving the stability and durability of the entire structure in the process of supporting the surrounding rock; at the same time, through the elastic compressive stress of the first spring 11 and the tensioning force applied to the anchor rod, the first umbrella frame 3 can be properly adjusted according to the actual changes of the surrounding rock. The second umbrella rod 10 automatically opens and inserts into the confining pressure to provide support force for the surrounding rock; at the same time, the elastic tensile stress of the first spring 11 cooperates with the first umbrella rod 9 to limit the opening angle of the second umbrella rod 10 from being too large, and thus failing to provide support effect; in addition, if the soil of the original tunnel is relatively hard, the first spring 11 in this embodiment can be arranged above the first umbrella rod 9, one end of which is fixed to the outer wall of the first sleeve 6 and the other end is fixed to the rod body of the second umbrella rod 10. By increasing the elastic force, the tension of the second umbrella rod 10 in the surrounding rock anchor hole channel is increased and it is easier to open, so as to drive the pointed cone of the second umbrella rod 10 to drill into the surrounding rock with harder soil more easily.

[0083] As a further embodiment of the present invention, Figure 3 As shown, the second umbrella frame 4 includes a third umbrella rod 13, a fourth umbrella rod 14, a second spring 15 and a fifth umbrella rod 16;

[0084] One end of the third umbrella rod 13 is hinged to the middle part of the outer wall of the second sleeve 7, and the other end thereof is hinged to one end of the fourth umbrella rod 14. The other end of the fourth umbrella rod 14 is hinged to the middle part of the fifth umbrella rod 16. One end of the fifth umbrella rod 16 is hinged to the bottom of the outer wall of the second sleeve 7, and the other end of the fifth umbrella rod 16 is a pointed cone structure.

[0085] The second spring 15 is fixedly connected between the third umbrella rod 13 and the fourth umbrella rod 14 .

[0086] In this embodiment, the fifth umbrella rod 16 is hinged on the hinge seat of the second sleeve 7, and the third umbrella rod 13 and the fourth umbrella rod 14 serve as the hinge parts of the two, so that during the construction process, the fifth umbrella rod 16 can rotate freely relative to the second sleeve 7 to facilitate insertion into the surrounding rock for support; furthermore, the surrounding rock of the tunnel usually has unevenness and displacement, and the combination of the second spring 15 and the third umbrella rod 13 and the fourth umbrella rod 14 can automatically adjust the rotation direction and rotation angle of the fifth umbrella rod 16. When the surrounding rock undergoes a slight displacement or deformation, the second spring can help the second umbrella frame to adjust the opening angle and insertion depth of the surrounding rock by the restoring force provided by its elastic stress to maintain a stable state; at the same time, the composite support structure formed by the first umbrella frame 3 and the second umbrella frame 4 can use the combination of different umbrella rods to freely distribute and transfer the loads applied to different parts when the surrounding rock is loaded, thereby reducing stress concentration and enhancing the overall safety of the tunnel. In addition, if the soil of the original tunnel is relatively hard, the second spring 15 in this embodiment can be arranged above the third umbrella pole 13 and the fourth umbrella pole 14, with one end thereof connected to the second sleeve 8, and the other end connected to the rod body of the fifth umbrella pole 16. By increasing the elastic force, the tension of the fifth umbrella pole 16 in the surrounding rock anchor hole channel is increased and it is easier to open, thereby driving the pointed cone of the fifth umbrella pole 16 to drill into the surrounding rock with harder soil more easily.

[0087] As a further embodiment of the present invention, Figure 1 As shown, at least two first umbrella frames 3 are arranged around the first sleeve 6 , and at least two second umbrella frames 4 are arranged around the second sleeve 7 .

[0088] In this embodiment, the number of the first umbrella skeletons 3 is preferably three, and the three first umbrella skeletons 3 are arranged in sequence along the circumference of the first sleeve 6. The number of the second umbrella skeletons 4 is preferably three, and the three second umbrella skeletons 4 are arranged in sequence along the circumference of the second sleeve 7. By arranging three umbrella skeletons around the first sleeve 6 and the second sleeve 7, a relatively dense support system can be formed. The three umbrella skeletons can effectively disperse the load applied to the surrounding rock and reduce the pressure borne by each umbrella skeleton alone, thereby improving the stability and bearing capacity of the overall structure. In addition, when the surrounding rock of the tunnel with hard soil can be stable itself, the first umbrella skeleton 3 and the second umbrella skeleton 4 can be used as the support system. The number of second umbrella frames 4 can be reduced to two, and the two first umbrella frames 3 are symmetrically arranged along the axis of the anchor rod, and the two second umbrella frames 4 are symmetrically arranged along the axis of the anchor rod. While providing support for the surrounding rock tunnel, it also saves materials for manufacturing umbrella frames and improves economic benefits. In the tunnel surrounding rock with soft and loose soil, the number of first umbrella frames 3 and second umbrella frames 4 arranged in sequence along the circumference of the first sleeve 6 and the second sleeve 7 can be four. By adding more umbrella frames, the load applied to the surrounding rock can be further effectively dispersed, and the pressure borne by each umbrella frame alone can be reduced, thereby improving the stability and bearing capacity of the overall structure.

[0089] As a further embodiment of the present invention, Figure 3 and Figure 4 As shown, the buckle 5 includes a pull rod 17, a buckle fixing block 18 and a buckle sliding block 19;

[0090] The buckle fixing block 18 is provided with a groove, the buckle fixing block 18 is fixed on the anchoring section 1, and the buckle sliding block 19 is slidably connected in the groove;

[0091] One end of the pull rod 17 is fixedly connected to the anchoring section 1 , and the other end is fixedly connected to the buckle sliding block 19 , so as to control the buckle sliding block 19 to be limited to slide in the groove.

[0092] In this embodiment, the snap-on sliding block 19 can slide freely in the groove of the snap-on fixing block 18, and by applying tension to the anchor rod, the end of the pull rod 17 is further driven to rotate relative to each other, so as to control the sliding of the snap-on sliding block 19, thereby facilitating the release of the second umbrella frame 4; in addition, the snap-on fixing block 18 is directly fixedly connected to the anchoring section 1 to form a stable base, and when the anchoring agent injected into the anchor rod solidifies, the snap-on fixing block 18 can also play a supporting and fixing role.

[0093] As a further embodiment of the present invention, Figure 1 As shown, the detachable section 2 comprises a plurality of anchor rod detachable sections, and each of the anchor rod detachable sections is connected by threads;

[0094] In the detachable section 2, the thread tightening direction of the anchor rod detachment section directly connected to the anchoring section 1 is opposite to the thread tightening direction between the remaining anchor rod detachment sections.

[0095] In this embodiment, the thread tightening direction of the anchor rod disassembly section directly connected to the anchoring section 1 is opposite to the thread tightening direction between the remaining anchor rod disassembly sections. The purpose of this design is to be able to combine a plurality of disassembly sections into a removable section 2 of any length, which has good adaptability to tunnels with irregular cross-sectional shapes and tunnels with uneven distances between the contour lines of the expanded tunnel and the existing tunnel. The opposite thread tightening directions facilitate the disassembly of the removable section 2 and the anchoring section 1. In addition, the disassembly section can be reused, which greatly reduces the project cost and saves economic costs. In addition, the thread width and depth between multiple disassembly sections can be designed and adjusted according to project requirements, so as to adapt to projects with special construction requirements. For example, the torque required for disassembly of the disassembly section from the outside to the inside is gradually increased by designing and adjusting, and the disassembly section can be gradually disassembled from the outside to the inside by controlling the torque, which has good applicability to projects with layered and step-by-step excavation of surrounding rock.

[0096] As a further embodiment of the present invention, Figure 6 and Figure 8As shown, the anchor rod further includes a nut 20 and a gasket 21 , and the nut 20 and the gasket 21 are sleeved on the tail ends of the anchoring section 1 and the detachable section 2 .

[0097] In this embodiment, when the anchor rod is initially installed, the nut 20 and the pad 21 are installed at the tail end of the detachable section 2, and their function is to constrain the tail end of the detachable section 2 and lock the prestress of the detachable section 2 of the anchor rod; after the detachable section 2 is removed, the nut 20 and the pad 21 are installed at the tail end of the anchoring section 1, and their function is to serve as one of the components for the secondary tensioning of the anchoring section 1, and together with the second umbrella frame 4, lock the prestress of the anchoring section 1 to improve the structural stability and reliability. In addition, the pad 21 serves as the boundary of the grouting body, and plays a limiting role on the grouting body when it is not solidified.

[0098] Please refer to Figures 5 to 9 The second embodiment of the present invention is based on the implementation of the above-mentioned detachable anchor rod embodiment, and provides a support method for applying the above-mentioned detachable anchor rod to in-situ expansion of a tunnel, which comprises the following steps:

[0099] S1: According to the design parameters of the anchor bolts for the expanded tunnel, anchor bolt holes are drilled on the lining of the original tunnel towards the depth of the surrounding rock of the expanded tunnel;

[0100] S2: closing the first umbrella frame 3 and the second umbrella frame 4, pushing the second umbrella frame 4 to the buckle 5 for buckling, and pushing the anchor rod to a designated position in the anchor hole;

[0101] S3: Install the nut 20 and the pad 21 at the rear end of the detachable section 2;

[0102] S4: the anchor rod is tensioned, unloaded, and tensioned again, and the tension force is applied step by step to slowly increase the anchor rod prestress value until the designed prestress value is reached; the first umbrella frame 3 is opened under the tension load to drive the tip of the second umbrella rod 10 to penetrate into the surrounding rock; the restrictive effect of the buckle 5 on the second umbrella frame 4 gradually disappears under the tension load until the second umbrella frame 4 is separated from the buckle 5 and then opened; in the unloading stage, the second umbrella frame 4 is affected by the rebound deformation of the anchor section 1, and drives the tip of the fifth umbrella rod 16 to penetrate into the surrounding rock of the second anchor point;

[0103] S5: After the surrounding rock and the anchor are stabilized, the detachable section 2, the nut 20 and the pad 21 are removed, and the surrounding rock and tunnel lining between the contour of the expanded tunnel and the existing tunnel are removed;

[0104] S6: tensioning the anchoring section 1 again to compensate for the prestress loss caused during the excavation process, and grouting is performed after tensioning is completed;

[0105] S7: Install the pad 21 and the nut 20 to the tail end of the anchoring section 1, and then construct the tunnel lining structure to complete the construction.

[0106] When this embodiment is implemented, during the construction process, closing the first umbrella frame 3 and the second umbrella frame 4 can make the anchor rod reach the designated position smoothly and quickly; the first anchoring point is the top of the anchor hole channel above the excavation contour line of the expansion tunnel, and when the first umbrella frame 3 reaches the first anchoring point, a preset tensioning force is applied, so that the first umbrella frame is quickly opened and inserted into the surrounding rock around the anchor hole, ensuring that the anchor rod can be firmly fixed in the anchor hole, providing end anchor force for the rod body; different from traditional anchor rods, the detachable anchor rod can quickly apply prestress, effectively preventing instability caused by loosening during construction.By applying prestress through cyclic loading and unloading, and cooperating with the design of the buckle 5, the second umbrella frame 4 can be effectively penetrated into the surrounding rock at the second anchor point, providing further support for the tunnel, and reducing the prestress loss of the anchoring section 1 of the anchor rod caused by the anchor rod losing the restraining effect of the tail end pad 21 of the detachable section 2 when the detachable section 2 of the anchor rod is removed. In addition, the first umbrella frame 3 and the second umbrella frame 4 are embedded in their respective positions with opposite opening directions so that the two form a force matrix. The existence of the first umbrella frame 3 can effectively resist the sinking phenomenon of the surrounding rock soil caused by factors such as humidity changes, and the existence of the second umbrella frame 4 can effectively withstand and disperse the surrounding The rock and soil pressure above the rock can be reduced to avoid uneven deformation caused by the upper load; the nut 20 and the pad 21 can ensure effective contact between the anchor rod and the surrounding rock, constrain the tail end of the detachable section 2 in the initial installation stage of the anchor rod, lock the prestress of the detachable section 2 of the anchor rod, and after the detachable section 2 is removed, it can be used together with the second umbrella frame 4 to lock the prestress of the anchor section 1 to improve the stability and reliability of the structure; after the surrounding rock is excavated, the purpose of tensioning the anchor section 1 again is to adjust the depth of the first umbrella frame 3 and the second umbrella frame 4 into the surrounding rock to compensate for the prestress loss caused by the removal of the detachable section 2; compared with the traditional way of tunnel expansion During the entire construction process, this method avoids the use of the "backfill first, then excavation" construction method to expand the tunnel, which not only controls the economic cost but also shortens the construction period; at the same time, during the construction process, this method innovatively introduces umbrella-type anchor rods with opposite opening directions, and through cyclic loading and unloading, the umbrella ribs of the first umbrella frame 3 of the anchor rod are opened downward and penetrated into the surrounding rock of the anchor hole channel, and at the same time, the umbrella ribs of the second umbrella frame 4 of the anchor rod are opened upward and penetrated into the surrounding rock of the anchor hole channel, so as to fix the anchor rod in the surrounding rock anchor hole of the expanded tunnel, thereby achieving timely support effect after the expansion and excavation of the surrounding rock soil body, and avoiding the aggravation of surrounding rock deterioration; The first umbrella frame 3 and the second umbrella frame 4 are driven into the surrounding rock in opposite opening directions. Therefore, during the tunnel expansion process, whether it is the up and down movement of the stratum or the pressure change caused by external load, it will be timely and effectively anchored and resisted by the bidirectional anchoring of the anchor rod, which can more effectively control the deformation of the surrounding rock. In addition, the first umbrella frame 3 and the third umbrella frame 4 are fixed to the anchor rod by a combination of hinged and elastic connections. When the surrounding rock is deformed, the first umbrella frame 3 and the third umbrella frame 4 can adaptively adjust the opening angle and the depth of penetration into the surrounding rock by a combination of shear stress and elastic stress, which can effectively avoid instability caused by deformation of the surrounding rock.

[0107] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A detachable anchor rod used for in-situ tunnel expansion, characterized in that The invention comprises an anchor rod, wherein the anchor rod comprises an anchoring section (1) and a detachable section (2), wherein the anchoring section (1) and the detachable section (2) are threadedly connected, wherein the anchoring section (1) is located in an anchor hole channel above the excavation contour line of the expansion tunnel, and the detachable section (2) is located in the anchor hole channel below the excavation contour line of the expansion tunnel; The anchoring section (1) is provided with a first umbrella frame (3), a buckle (5) and a second umbrella frame (4) in sequence, and the second umbrella frame (4) is located inside the opening of the anchor hole channel above the excavation contour line of the expansion tunnel; The first umbrella frame (3) is fixedly connected to the top of the anchoring section (1), and the first umbrella frame (3) is in a closed state under the restriction of the anchor hole channel. When the first umbrella frame (3) reaches the first anchoring point and applies a tensioning force to the anchor rod, the first umbrella frame (3) opens with the opening facing downward and penetrates into the surrounding rock where the anchor hole channel is located; The buckle (5) is fixedly connected to the middle section of the anchoring section (1) and is buckled with the second umbrella frame (4); when a tensioning force is applied to the anchor rod, the buckle (5) is deformed to release the second umbrella frame (4); The second umbrella frame (4) is movably connected to the anchoring section (1) and is in a closed state when the buckle (5) is engaged. When the buckle (5) is deformed to release the second umbrella frame (4), the second umbrella frame (4) opens with its opening facing upward and penetrates into the surrounding rock of the second anchoring point in the anchor hole channel.

2. A detachable anchor rod for in-situ tunnel expansion according to claim 1, characterized in that: The first umbrella frame (3) is fixedly connected to the end of the top end of the anchoring section (1) via a first sleeve (6), and the second umbrella frame (4) is movably connected to the anchoring section (1) via a second sleeve (7).

3. A detachable anchor rod for in-situ tunnel expansion according to claim 2, characterized in that: The anchoring section (1) is also provided with a sawtooth structure (8) with the tooth tip facing upwards; the anchoring section (1) and the sawtooth structure (8) are an integrally formed structure; the second sleeve (7) is sleeved on the sawtooth structure (8); and the second sleeve (7) can only move in one direction toward the top end of the anchoring section (1) under the restriction of the sawtooth structure (8).

4. The detachable anchor rod used for in-situ tunnel expansion according to claim 2 is characterized in that: The first umbrella frame (3) comprises a first umbrella rod (9), a second umbrella rod (10), a first spring (11) and a slider (12); The slider (12) is slidably connected to the middle section of the outer wall of the first sleeve (6) and is hinged to one end of the first umbrella rod (9); the other end of the first umbrella rod (9) is hinged to the middle part of the second umbrella rod (10); one end of the second umbrella rod (10) is hinged to the top of the outer wall of the first sleeve (6); the other end of the second umbrella rod (10) is a pointed cone structure; The first spring (11) is fixedly connected between the first umbrella rod (9) and the outer wall of the first sleeve (6).

5. The detachable anchor rod used for in-situ tunnel expansion according to claim 2, characterized in that: The second umbrella frame (4) comprises a third umbrella rod (13), a fourth umbrella rod (14), a second spring (15) and a fifth umbrella rod (16); One end of the third umbrella rod (13) is hinged to the middle part of the outer wall of the second sleeve (7), and the other end is hinged to one end of the fourth umbrella rod (14). The other end of the fourth umbrella rod (14) is hinged to the middle part of the fifth umbrella rod (16). One end of the fifth umbrella rod (16) is hinged to the bottom of the outer wall of the second sleeve (7), and the other end of the fifth umbrella rod (16) is a pointed cone structure. The second spring (15) is fixedly connected between the third umbrella rod (13) and the fourth umbrella rod (14).

6. A detachable anchor rod for in-situ tunnel expansion according to claim 2, characterized in that: At least two of the first umbrella frames (3) are arranged around the first sleeve (6), and at least two of the second umbrella frames (4) are arranged around the second sleeve (7).

7. The detachable anchor rod used for in-situ tunnel expansion according to claim 1, characterized in that: The buckle (5) comprises a pull rod (17), a buckle fixing block (18) and a buckle sliding block (19); The buckle fixing block (18) is provided with a groove, the buckle fixing block (18) is fixed on the anchoring section (1), and the buckle sliding block (19) is slidably connected in the groove; One end of the pull rod (17) is fixedly connected to the anchoring section (1), and the other end is fixedly connected to the buckle sliding block (19), so as to control the buckle sliding block (19) to be limited to slide in the groove.

8. The detachable anchor rod used for in-situ tunnel expansion according to claim 1, characterized in that: The detachable section (2) comprises a plurality of anchor rod detachable sections, and each of the anchor rod detachable sections is connected by threads; In the detachable section (2), the thread tightening direction of the anchor rod detachment section directly connected to the anchoring section (1) is opposite to the thread tightening direction between the remaining anchor rod detachment sections.

9. The detachable anchor rod used for in-situ tunnel expansion according to claim 1, characterized in that: The anchor rod further comprises a nut (20) and a pad (21), wherein the nut (20) and the pad (21) are sleeved on the tail ends of the anchoring section (1) and the detachable section (2).

10. A support method in in-situ tunnel expansion, based on the detachable anchor rod according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1: According to the design parameters of the anchor bolts for the expanded tunnel, anchor bolt holes are drilled on the lining of the original tunnel towards the depth of the surrounding rock of the expanded tunnel; S2: closing the first umbrella frame (3) and the second umbrella frame (4), pushing the second umbrella frame (4) to the buckle (5) for locking, and pushing the anchor rod to a designated position in the anchor hole; S3: Installing the nut (20) and the gasket (21) at the rear end of the detachable section (2); S4: the anchor rod is tensioned, unloaded, and tensioned again, and the tension force is applied step by step to slowly increase the anchor rod prestress value until the designed prestress value is reached; the first umbrella frame (3) is opened under the tension load to drive the tip of the second umbrella rod (10) to penetrate into the surrounding rock; the restrictive effect of the buckle (5) on the second umbrella frame (4) gradually disappears under the tension load until the second umbrella frame (4) is separated from the buckle (5) and then opened; in the unloading stage, the second umbrella frame (4) is affected by the rebound deformation of the anchor section (1) to drive the tip of the fifth umbrella rod (16) to penetrate into the surrounding rock of the second anchor point; S5: After the surrounding rock and the anchor rod are stabilized, the detachable section (2), the nut (20) and the pad (21) are removed, and the surrounding rock and tunnel lining between the contour of the expanded tunnel and the existing tunnel are removed; S6: tensioning the anchoring section (1) again to compensate for the prestress loss caused during the excavation process, and grouting after tensioning is completed; S7: Install the pad (21) and the nut (20) to the rear end of the anchoring section (1), and then construct the tunnel lining structure to complete the construction.

Images