A self-buried barbed anchor head foot locking anchoring method and anchor pipe structure suitable for soft rock tunnels

Abstract

This invention discloses a self-grown barbed anchor head locking and anchoring method and anchor pipe structure suitable for soft rock tunnels. The steps are: 1. Pre-fabricate a locking anchor pipe with a self-grown barbed anchor head; 2. During the construction of the soft rock tunnel, at the beginning of the rock and soil excavation, embed the pre-fabricated anchor pipe into the surrounding rock mass; 3. The non-rock-embedded end of the anchor pipe is firmly connected to the steel frame; 4. The anchor pipe end forms a self-grown barbed anchor head under the grouting expansion force and pull-out force. The invention also relates to a structure in which the anchor pipe body is connected to the barbed anchor head, the grout-stopping section (non-drilled section) on the anchor pipe body is connected to the grouting-drilled section, a non-rock-embedded end is installed at the end of the grout-stopping section (non-drilled section) of the anchor pipe body, the pointed end of the barbed anchor head is connected to the stacked pipe ring section, and the stacked pipe ring section is connected to the stacked pipe interval sections. The method is easy to implement and simple to operate, solving the problems existing in the current technology. It can safely and efficiently assist in construction, reduce the number of anchor pipes, shorten the length of anchor pipes, and effectively improve the safety of tunnel structure and the stability of the tunnel.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical and underground engineering technology, and more specifically relates to a self-grown barbed anchor head locking and anchoring method suitable for soft rock tunnels, and also relates to a self-grown barbed anchor head anchor pipe structure suitable for soft rock tunnels. Background Technology

[0002] With economic and social development, the construction of underground tunnels is increasing, including transportation tunnels, water diversion tunnels, and municipal facilities. Tunnel construction is increasingly involving sections with increasingly complex and difficult geological conditions, making the initial support of these tunnels a challenging problem for engineers and designers. In recent years, based on a deeper understanding of the New Austrian Tunneling Method (NATM) and the continuous accumulation of engineering experience, tunnel support structures have evolved from single passive load-bearing structures to support systems where the surrounding rock and the support structure share the load. Anchor bolts, steel arches, steel mesh, and shotcrete composite lining are commonly used support structure systems. These systems can form a reinforced ring around the tunnel, inhibiting deformation and collapse of the surrounding rock, and forming a load-bearing body together with the initial tunnel support before the surrounding rock deforms and collapses. Achieving near-self-sustaining performance of the surrounding rock is the optimal effect and a goal pursued by the industry.

[0003] Anchor pipe (or anchor rod) support is a newly developed technology in composite lining support systems in recent years. Generally, in tunnel construction in soft strata, anchor pipes are installed at the arch feet after the steel arch frame is erected to enhance the load-bearing capacity of the steel frame. The anchor pipes firmly lock the steel frame feet to the surrounding rock, reinforcing the support structure and the surrounding rock strata into a unified whole through tangential and axial anchoring forces acting on the surrounding rock. This reduces initial support settlement in the upper step caused by foundation weakening and initial support settlement in the lower step caused by suspension. The installation of anchor pipes is an effective measure to control the settlement of the support structure, especially in conditions of weak strata, high water content, or water accumulation at the arch foot. The addition of anchor pipes has a significant effect on controlling arch crown and ground settlement. Because anchor pipe construction is easy, economical, and effective, it greatly improves construction efficiency and safety, eliminates the need for other auxiliary construction measures, and saves manpower and resources. It has been widely used in tunnel construction both domestically and internationally.

[0004] However, the use of anchor pipes also revealed many shortcomings, such as:

[0005] (1) It is generally believed that the longer the length, the better. However, when it reaches a certain length, it will not only be inconvenient to construct, but will also delay the best time for locking the feet.

[0006] (2) It is generally believed that the thicker the rod, the better. However, increasing the pipe diameter (rod diameter) requires drilling with a special drilling machine, which is not only inconvenient for construction, but also delays the best time for locking the feet.

[0007] (3) When there is relative slippage between the anchor pipe and the surrounding rock mass, the anchoring effect will be greatly weakened or even rendered ineffective. Summary of the Invention

[0008] The purpose of this invention is to provide a self-grown barbed anchor head locking anchoring method and anchor pipe structure suitable for soft rock tunnels. The method is easy to implement and simple to operate. This method and the self-grown barbed anchor head locking anchor pipe effectively solve the problems existing in the prior art. It can not only safely and efficiently assist construction, but also reduce the number of anchor pipes, shorten the length of the anchor pipes, and save construction costs.

[0009] Another objective of this invention is to provide a self-growing barbed anchor head and anchor pipe structure suitable for soft rock tunnels. The structure is simple and easy to use. Under the action of the self-growing barbed anchor head, the initial support with the steel frame as the skeleton can form a tight whole with the surrounding rock, effectively improving the safety of the tunnel structure and the stability of the tunnel chamber.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A self-grown barbed anchor head locking and anchoring method suitable for soft rock tunnels, the steps of which are as follows:

[0012] (1) Prefabricate a locking foot anchor pipe with a self-growing barbed anchor head. The anchor pipe includes the anchor pipe body and the barbed anchor head. The anchor pipe body includes a grout-stopping section and a grouting and drilling section. The self-growing barbed anchor head includes a pointed end section, a stacked pipe ring section, a stacked pipe partition section, a reinforcement ring A, and a reinforcement ring B.

[0013] (2) During the construction of soft rock tunnels, at the beginning of the excavation of the rock and soil, when the steel arch frame of each step or section is erected, the prefabricated anchor pipe is embedded into the surrounding rock, and the grouting drilling section is completely embedded into the surrounding rock.

[0014] (3) The non-rock-embedded end of the anchor pipe is firmly connected to the steel frame;

[0015] (4) Under the combined action of grouting expansion force and pull-out force, the anchor pipe end forms a self-grown barbed anchor head. Grouting through the anchor pipe allows the grout to diffuse into the surrounding rock and the pipe head. While reinforcing the surrounding rock, the self-grown barbs of the anchor head spread out, with the pointed end being conical and the tail barbs tightly gripping the surrounding rock and forming an integral anchor head with the grout-reinforced surrounding rock. When the initial support steel frame is subjected to the pressure of the surrounding rock, it retracts inward (or has a tendency to retract inward). The direct force generated by the displacement of the steel frame and the deformation of the surrounding rock pulls on the anchor pipe. The anchor head, as the load-bearing end point, directly bears the force and causes the barbs to further spread, forming a tighter anchor head structure.

[0016] Using the self-grown barbed anchor head locking anchoring method, the initial support steel frame of the tunnel is firmly erected under the action of the self-grown barbed anchor head locking anchor pipe.

[0017] Of the above steps, step 4 is the most crucial. After the self-growing barbed anchor head is formed, the anchor head end of the locking anchor pipe is anchored in the surrounding rock mass, while the other end is tightly fastened to the steel arch frame, similar to a link or connecting bridge, forming an integral load-bearing structure between the tunnel's initial support structure (mainly the steel arch frame) and the surrounding rock mass behind the initial support. Step 4 (formation of the self-growing barbed anchor head) effectively solves a common practical problem in tunnel construction—due to the weak surrounding rock, it is necessary to increase the scale of the initial support, especially the use of steel arch frames, during construction. Some tunnel construction sites have used double-layer steel arch frames, but the deformation of the initial support still cannot be controlled. At the same time, this deformation is caused by the pressure of the surrounding rock behind the structure, and once deformation occurs, it will have the consequences and risks of rapid deterioration, difficulty in control, and even collapse. The self-growing barbed anchor head of this invention can form an effective load-bearing integral structure between the initial support (especially the skeleton steel arch frame) and the surrounding rock before the initial support structure deforms. The structure is stable, and the expected effect is obvious. Through multiple experiments, it has saved at least 25% of the construction cost.

[0018] A self-grown barbed anchor head and anchor pipe structure suitable for soft rock tunnels, comprising an anchor pipe body and a barbed anchor head. The anchor pipe body includes a grout-stopping section (non-drilled) and a grouting-drilled section. The self-grown barbed anchor head includes an end tip, a stacked pipe ring section, stacked pipe partition sections, auxiliary reinforcing steel ring A, and auxiliary reinforcing steel ring B. The anchor pipe body is connected to the barbed anchor head; the grout-stopping section (non-drilled) on the anchor pipe body is connected to the grouting-drilled section; a non-rock-embedded end is installed at the end of the grout-stopping section (non-drilled) on the anchor pipe body; and the barbs... The pointed end of the anchor head is connected to the entire ring section of the stacked pipe, and the entire ring section of the stacked pipe is connected to the segmented sections of the stacked pipe. Auxiliary reinforcing bar rings A and B are respectively installed on the grouting bore section of the anchor pipe body. The front section of the barbed segment is welded to the tail of the pointed end of the anchor pipe body to form the entire ring section of the stacked pipe. The rear section of the barbed segment is welded to the auxiliary reinforcing bar rings A and B to form the segmented sections of the stacked pipe. The opening angle between the barbs and the pipe body can be adjusted by adjusting the diameter and position of the auxiliary reinforcing bar rings A and B.

[0019] Compared with the prior art, the present invention has the following advantages and effects:

[0020] The core of this method is the anchor pipe with a self-growing barbed anchor head. The anchor pipe and anchor head can be made from locally available materials: ordinary hot-rolled seamless steel pipes can be used based on the existing materials on site; ordinary steel pipes (with a size larger than the pipe body section) can also be used for the pointed end stacked pipes; ordinary steel bars are used for the auxiliary reinforcing rings; the steel pipes and reinforcing bars are connected by welding; cement grout can be used preferentially for grouting the anchor pipe, and under the action of grouting pressure, it is injected into the pipe body and diffuses to the surrounding rock and the pipe head.

[0021] The self-grown barbed anchor head locking anchoring method proposed in this invention is easy to implement, and after construction, it can effectively connect the initial support steel frame of the tunnel and the surrounding rock mass to form a whole load-bearing arch, effectively reducing the load borne by the support structure and significantly improving the structural safety of the tunnel during construction and operation.

[0022] Compared with the conventional anchor pipe solution, the present invention can save about 30% of the project investment while achieving the same structural safety. In contrast, the conventional anchor pipe solution fails to achieve structural safety, leading to tunnel support failure and tunnel defects, which requires an additional 20% of the project investment and extends the tunnel construction period.

[0023] This invention is applicable to tunnels with weak surrounding rock conditions, and its application can be further expanded to unfavorable geological sections such as shallow burial sites and fault fracture zones, making it highly practical and worthy of promotion. Attached Figure Description

[0024] To more clearly illustrate the technical solution of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A schematic diagram of the barbed anchor head locking anchor pipe structure, which is a self-grown barbed anchor head locking anchoring method applicable to soft rock tunnels;

[0026] Figure 2 A longitudinal section view of the barbed anchor head structure at the front end of the anchor pipe for a self-grown barbed anchor head locking anchoring method applicable to soft rock tunnels;

[0027] Figure 3 A cross-sectional view of the entire ring structure of a self-grown barbed anchor head locking and anchoring method suitable for soft rock tunnels;

[0028] Figure 4 This is a cross-sectional view of a self-grown barbed anchor head locking and anchoring method suitable for soft rock tunnels, showing a segmented structure of a barbed anchor head stacked pipe.

[0029] Wherein: 1-anchor pipe body, 2-barbed anchor head, 3-grout-stopping section without drilling, 4-grouting drilling section, 5-grouting hole, 6-end tip section, 7-stacked pipe ring section, 8-stacked pipe partition section, 9-assistive reinforcing bar ring A, 10-assistive reinforcing bar ring B, 11-non-rock-embedded end, 12-barbed pipe segment. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the embodiments.

[0031] Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in the field or according to the product manual. Where the manufacturer of the products used is not specified, they are all conventional products that can be obtained by purchase.

[0032] Example 1:

[0033] like Figure 1-4 As shown, a self-grown barbed anchor head locking and anchoring method suitable for soft rock tunnels includes the following steps:

[0034] 1. Pre-fabricate a locking anchor pipe with a self-growing barbed anchor head, 3.5m in length. The anchor pipe includes the pipe body 1 and the barbed anchor head 2. The pipe body 1 is made of ordinary hot-rolled seamless steel pipe with an outer diameter of 38mm and a wall thickness of 3.5mm. It includes a 1.0m long non-drilled section 3 for stopping grouting and a 2.5m long drilled section 4 for grouting. The drilled section 4 has approximately 46 grouting holes 5. The self-growing barbed anchor head 2 is made of ordinary hot-rolled seamless steel pipe with an outer diameter of 51mm and a wall thickness of 3.5mm. Six segments of seamless rolled steel pipe, cut into sections, and auxiliary reinforcing steel rings are welded to the front end of the pipe body to form a structure including a 0.15m long end-point section 6, a 0.15m long stacked pipe ring section 7, a 0.35m long stacked pipe segment 8, an 8mm diameter auxiliary reinforcing steel ring A9, and a 16mm diameter auxiliary reinforcing steel ring B10. Prefabricating the anchor pipes before tunnel construction can improve construction efficiency, not affect the tunnel excavation construction organization, and allow for refined manufacturing to ensure the quality of the anchor pipes.

[0035] 2. During the construction of soft rock tunnels, at the beginning of the excavation of the soil and rock mass, when the steel arch frames of each step or section are erected, the prefabricated anchor pipes are embedded into the surrounding rock mass, and the grouting drilling section 4 is completely embedded into the surrounding rock, which plays the role of positioning the steel frame and reinforcing the surrounding rock.

[0036] 3. The non-rock-embedded end 11 of the anchor pipe is firmly connected to the steel frame. This is the basic guarantee for forming an integral whole between the anchor pipe and the surrounding rock mass. The two ends of the anchor pipe (one end embedded in the surrounding rock mass and the other end connected to the steel frame) are two crucial nodes that connect the steel frame and the surrounding rock mass through the anchor pipe.

[0037] 4. Under the combined action of grouting expansion force and pull-out force, the end of the anchor pipe forms a self-grown barbed anchor head 2. Grouting is carried out through the grouting hole 5 of the anchor pipe to allow the grout to diffuse into the surrounding rock and the pipe head. While reinforcing the surrounding rock, the self-grown barbs 12 of the anchor head spread out. The angle between the barbs and the pipe body is 3°. The pointed end is conical, and the tail barbs are tightly stuck in the surrounding rock and form an integral anchor head with the grout-reinforced surrounding rock. When the initial support steel frame is subjected to the pressure of the surrounding rock, it retracts (or has a tendency to retract). The direct force generated by the displacement of the steel frame and the deformation of the surrounding rock pulls on the anchor pipe. The anchor head, as the load-bearing end point, directly bears the force and causes the barbs to further spread, forming a tighter anchor head structure. The angle between the barbs and the pipe body is greater than 3°.

[0038] In step 4, the grouting of the anchor pipe is focused on the tip of the rock-embedded end to form a barbed rigid anchor head.

[0039] Using the self-grown barbed anchor head locking anchoring method, the initial support steel frame of the tunnel is firmly erected under the action of the self-grown barbed anchor head locking anchor pipe.

[0040] Example 2:

[0041] A self-grown barbed anchor head and anchor pipe structure suitable for soft rock tunnels, comprising an anchor pipe body 1, a barbed anchor head 2, a grout-stopping section (non-drilled) 3, a grouting drilled section 4, grouting holes 5, an end tip section 6, a stacked pipe ring section 7, a stacked pipe partition section 8, a reinforcing steel ring A9, a reinforcing steel ring B10, a non-embedded end 11, and barbed segments 12. The anchor pipe body 1 is connected to the barbed anchor head 2; the grout-stopping section (non-drilled) 3 on the anchor pipe body 1 is connected to the grouting drilled section 4; grouting holes 5 are provided on the grouting drilled section 4, with the number of grouting holes being 46 or 60 or more; and a non-embedded end 11 is installed at the end of the grout-stopping section (non-drilled) 3 of the anchor pipe body 1. The pointed end section 6 on the barbed anchor head 2 is connected to the stacked pipe ring section 7, and the stacked pipe ring section 7 is connected to the stacked pipe partition section 8. Auxiliary reinforcing bar rings A9 and B10 are respectively installed on the grouting drilling section 4 of the anchor pipe body 1. The front section of the barbed pipe segment 12 is welded to the tail of the pointed end section 6 of the anchor pipe body to form the stacked pipe ring section 7. The rear section of the barbed pipe segment 12 is welded to the auxiliary reinforcing bar rings A9 and B10 to form the stacked pipe partition section 8. Welding the 8mm diameter auxiliary reinforcing bar ring A9 to a distance of 0.13m from the tail of the stacked pipe ring section and the 16mm diameter auxiliary reinforcing bar ring B10 to a distance of 0.25m from the tail of the stacked pipe ring section can achieve a 3° angle between the barbs and the pipe body.

[0042] The core of the self-grown barbed anchor head locking anchoring method proposed in this invention is the locking anchor pipe of the self-grown barbed anchor head. The anchor pipe and anchor head can be made from locally sourced materials, using ordinary hot-rolled seamless steel pipes and ordinary steel bars welded together, resulting in very low construction costs and a very simple manufacturing process.

[0043] After the self-grown barbed anchor head is formed, the anchor head end of the locking anchor pipe is anchored in the surrounding rock mass, and the other end is tightly fastened to the steel arch frame, similar to a link or connecting bridge. This forms an integral load-bearing structure with the tunnel initial support structure (mainly steel arch frame) and the surrounding rock mass behind the initial support. The load borne by the initial support structure is effectively reduced, and the structural safety of the tunnel during construction and operation is significantly improved.

[0044] The self-growing barbed anchor head effectively solves a common practical problem in tunnel construction: due to the weak surrounding rock, it is necessary to increase the scale of initial support, especially the use of steel arch frames, during construction. Some tunnel construction sites have used double-layer steel arch frames, but the deformation of the initial support still cannot be controlled. At the same time, this deformation is caused by the pressure of the surrounding rock behind the structure, and once the deformation occurs, it will have the consequences and risks of rapid deterioration, difficulty in control, and even collapse. The self-growing barbed anchor head of this invention can form an effective load-bearing integral structure between the initial support (especially the skeleton steel arch frame) and the surrounding rock before the initial support structure deforms, which can save at least 25% of the construction cost.

[0045] Compared with the conventional anchor pipe solution, the present invention can save about 30% of the project investment while achieving the same structural safety. In contrast, the conventional anchor pipe solution fails to achieve structural safety, leading to tunnel support failure and tunnel defects, which requires an additional 20% of the project investment and extends the tunnel construction period.

[0046] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A self-grown barbed anchor head locking and anchoring method suitable for soft rock tunnels, applicable to tunnels with weak surrounding rock conditions, and also suitable for shallow burial and fault fracture zones and other adverse geological sections; it can form an effective load-bearing integral structure between the skeleton steel arch frame and the surrounding rock before the initial support structure deforms, characterized in that... The steps are as follows: (1) Prefabricate a locking anchor pipe with a self-growing barbed anchor head. The anchor pipe includes the anchor pipe body and the barbed anchor head. The anchor pipe body includes a grout-stopping section and a grouting section. The self-growing barbed anchor head includes a pointed end section, a stacked pipe ring section, a stacked pipe partition section, a reinforcing bar ring A, and a reinforcing bar ring B. The anchor pipe and anchor head can be made from locally sourced materials, using ordinary hot-rolled seamless steel pipes and ordinary reinforcing bars welded together. The construction cost is very low and the manufacturing process is very simple. (2) During the construction of soft rock tunnels, at the beginning of the excavation of the rock and soil, when the steel arch frame of each step or section is erected, the prefabricated anchor pipe is embedded into the surrounding rock, and the grouting drilling section is completely embedded into the surrounding rock. (3) The non-rock-embedded end of the anchor pipe is firmly connected to the steel frame. The two ends of the anchor pipe, namely the end embedded in the surrounding rock and the end connected to the steel frame, are two crucial nodes that connect the steel frame and the surrounding rock through the anchor pipe. (4) Under the combined action of grouting expansion force and pull-out force, the anchor pipe end forms a self-grown barbed anchor head. Grouting through the anchor pipe allows the grout to spread to the surrounding rock and the pipe head. While reinforcing the surrounding rock, the self-grown barbs of the anchor head spread out. The barbs have an angle of 3° with the pipe body. The pointed end is conical, and the tail barbs are tightly stuck in the surrounding rock and form an integral anchor head with the grout-reinforced surrounding rock. When the initial support steel frame is subjected to the pressure of the surrounding rock, it retracts inward. The direct force generated by the displacement of the steel frame and the deformation of the surrounding rock pulls on the anchor pipe. The anchor head, as the load-bearing end point, directly bears the force and causes the barbs to spread further to form a tighter anchor head structure. The angle between the barbs and the pipe body is greater than 3°. The grouting of the locking foot anchor pipe is focused on the tip of the rock-embedded end, forming a barbed rigid anchor head. Among them, the anchor pipe with self-grown barbed anchor head includes an anchor pipe body (1) and a barbed anchor head (2). The anchor pipe body (1) is connected to the barbed anchor head (2). The grout-stopping section (3) on the anchor pipe body (1) is connected to the grouting drilling section (4). A non-rock-embedded end (11) is installed at the end of the grout-stopping section (3) of the anchor pipe body (1). The tip section (6) on the barbed anchor head (2) is connected to the stacked pipe ring section (7). The stacked pipe ring section (7) is connected to the stacked pipe partition section (8). Auxiliary reinforcing bars are installed on the grouting drilling section (4) of the anchor pipe body (1). Ring A (9), auxiliary reinforcing bar ring B (10), the front section of the barbed tube segment (12) is welded to the end of the pointed section (6) of the anchor pipe body to form a stacked pipe ring segment (7), the rear section of the barbed tube segment (12) is welded to the auxiliary reinforcing bar ring A (9) and the auxiliary reinforcing bar ring B (10) to form a stacked pipe partition segment (8); the auxiliary reinforcing bar ring A (9) is welded to the auxiliary reinforcing bar ring B (10) 0.13m from the end of the stacked pipe ring segment, and the auxiliary reinforcing bar ring B (10) is welded to the end of the stacked pipe ring segment 0.25m from the end of the stacked pipe ring segment to achieve a 3° angle between the barbs and the pipe body; the grouting drilling section (4) is provided with grouting holes (5).

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