Highway tunnel upper step steel arch

Abstract

The utility model discloses a highway tunnel upper step steel arch, which relates to the technical field of tunnel steel arches and comprises a circular arc steel arch, inclined support legs are arranged on two outer sides of the circular arc steel arch, and the inclined support legs are connected with the circular arc steel arch through cross bars. According to the utility model, partial stress of the steel arch can be transmitted to the rock, the stress of the anchor rod is reduced, the safety reserve is larger, and even if the anchor rod goes wrong, as the steel arch feet are supported on the rock, the rock can be used as the final insurance. According to the utility model, the stress performance of the steel arch can be improved, and collapse and harm to safety during construction are prevented.

Description

Technical Field

[0001] The utility model relates to the technical field of tunnel steel arch frames, in particular to a steel arch frame for upper steps in a highway tunnel. Background Art

[0002] In the existing step method, the upper step steel arch frame is unit A, the lower step side wall steel arch frame is unit B, and the arch bottom is unit C and unit D. The steel arch frame units are distributed as follows: Figure 1 As shown, the unit description is used to distinguish different size structures. Corresponding joints are provided between each unit, and the joints generally adopt locking pin small tubes.

[0003] In the step method construction, after the upper step is excavated, the A unit is responsible for supporting the surrounding rock, bearing the downward pressure of the rock, and providing safety protection for the structure and construction. The A unit is supported on the rock by the bottom support feet and anchored in the rock by the locking foot anchor rod. The steel arch frame after the upper step is excavated is as follows: Figure 2 shown.

[0004] When excavating the lower step, before installing the B unit, the A unit steel arch frame will be in an empty state at the bottom for a period of time. After the lower step is excavated, the A unit foot is in an empty state. Figure 3 In this state, the steel arch frame of unit A is anchored to the surrounding rock only by anchor rods, and all forces are borne by the anchor rods. If there is a problem in the construction of the anchor rods or the pressure is too large and exceeds the bearing capacity of the anchor rods, the steel arch frame will inevitably collapse, causing a safety accident. Utility Model Content

[0005] The utility model provides a step steel arch frame for a highway tunnel, aiming to solve the technical problem in the background technology that when the bottom of the A unit steel arch frame falls, the anchor rod bears all the pressure and the safety risk is relatively large.

[0006] The utility model provides the following technical solutions to achieve the above purpose:

[0007] A steel arch frame for steps on a highway tunnel comprises an arc steel arch frame. Two outer sides of the arc steel arch frame are provided with oblique legs. The oblique legs and the arc steel arch frame are connected by a cross bar.

[0008] In the aforementioned steel arch frame for the upper steps of the highway tunnel, the arc steel arch frame, the oblique legs and the crossbar are welded into a whole using the same type of steel.

[0009] In the aforementioned steel arch frame of the upper step of the highway tunnel, the angle between the oblique support leg and the arc steel arch frame is 17°.

[0010] In the aforementioned steel arch frame of the upper step of the highway tunnel, the angle between the line connecting the lower end of the oblique support leg and the end of the arc steel arch frame and the horizontal line is 30°.

[0011] In the aforementioned steel arch frame for the upper step of the highway tunnel, the end of the arc steel arch frame 1 is connected to the locking anchor rod.

[0012] Beneficial Effects

[0013] Compared with the prior art, the utility model provides a steel arch frame for the upper step of a highway tunnel, which is suitable for tunnels with poor surrounding rock or tunnels that need to improve the initial support bearing capacity. Through the utility model, part of the force of the steel arch frame can be transferred to the rock, the force on the anchor rod is reduced, and the safety reserve is greater. Even if there is a problem with the anchor rod, the rock can be used as a last resort because the steel arch frame foot is supported on the rock. The utility model can improve the force-bearing performance of the steel arch frame and prevent collapse during construction, which endangers safety. Compared with the traditional mode, when excavating the lower step, the pressure on the locking foot anchor rod of the upper step arch frame is halved, and the safety factor is doubled.

[0014] In places where the surrounding rock is particularly poor, especially in V (five) grade surrounding rock, the existing support form may not guarantee safety. The minimum spacing of the steel arch frame is generally 60cm. If it is further increased, the number of steel arch frames will be large and the cost will be high. The support method of the utility model can greatly improve the bearing capacity, but the cost increase is not much. The implementation of the utility model is extremely cost-effective. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural diagram of the distribution of steel arch frame units;

[0016] Figure 2 This is a schematic diagram of the steel arch after the upper steps are excavated;

[0017] Figure 3 This is a schematic diagram of the bottom of Unit A being left empty after the lower steps are excavated;

[0018] Figure 4 To adapt to the upper step excavation profile of the utility model;

[0019] Figure 5 It is a schematic diagram of the structure of the utility model;

[0020] Figure 6 for Figure 5 Schematic diagram of force analysis in the middle circular area; the left part of the figure is the force transfer diagram from the upper part of the arc steel arch (the upper arc steel arch connected to the oblique leg) to the oblique leg and the lower part of the arc steel arch (the lower section of the arc steel arch connected to the oblique leg); the right part of the figure is a further force analysis diagram of the left part; the middle F is the pressure transmitted from the upper part of the arc steel arch, f1 and f2 are the forces of the two sections of the steel arch, f1 is the force on the oblique leg, and f2 is the force on the lower part of the arc steel arch.

[0021] Figure 7This is the force analysis diagram of f1 decomposed into F. In the diagram, the angle α= 17° / 2 = 8.5°; cosα=F / 2 / f1; f1=F / 2cosα=0.505F.

[0022] Figure numerals: 1-arc steel arch frame; 2-oblique supporting legs; 3-cross bar; 4-locking foot anchor rod. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0024] Embodiment: A steel arch frame for steps on a highway tunnel comprises a circular arc steel arch frame 1, oblique legs 2 are arranged on both outer sides of the circular arc steel arch frame 1, and the oblique legs 2 and the circular arc steel arch frame 1 are connected by a cross bar 3.

[0025] The arc steel arch frame 1, the oblique legs 2 and the crossbar 3 are welded into a whole by using the same type of steel.

[0026] The angle between the oblique support leg 2 and the arc steel arch 1 is 17°.

[0027] The angle between the line connecting the lower end of the oblique support leg 2 and the end of the arc steel arch frame 1 and the horizontal line is 30°.

[0028] The end of the arc steel arch frame 1 is connected to the foot locking anchor rod 4.

[0029] The above structure and layout reference Figure 5 shown.

[0030] In order to adapt to the above structure, when excavating the upper steps, an extra step is added to the side of the excavation contour for the placement of the oblique legs, and the steps need to be cleaned of surface gravel; then the normal construction is carried out, grouting anchor rods are installed, steel mesh is hung, 3-5cmC25 concrete is sprayed to seal the rock surface to prevent gravel from falling, and the steps are leveled to facilitate the placement of the end plate; then the steel arch frame is installed. Different from the conventional method, an oblique leg 2 is added to the side of the arc steel arch frame 1 to support the excavation step. The oblique leg 2 and the steel arch frame are horizontally connected with a crossbar 3 of the same type of steel, and the three are welded into a whole.

[0031] After the above scheme is implemented, the force F transmitted from above is jointly borne by two sections of steel arches at the step (f1 and f2). According to the parallelogram law of force, the forces on the inner and outer steel arches are the same, f1=f2, and the force reference is Figure 6-7 .

[0032] Afterwards, construction continued according to the step method and C25 shotcrete was constructed according to the drawings; the construction of the lower step of the tunnel began. After the lower step was excavated, part of the pressure transmitted from above was transferred to the rock at the step by the inclined support leg 2, and the inner steel arch frame transferred the force to the locking foot anchor 4. Compared with the traditional mode, the pressure on the locking foot anchor 4 was halved and the safety factor was doubled.

[0033] The above is only a preferred specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can make equivalent substitutions or changes according to the technical solution and concept of the present application within the technical scope disclosed in the present application, which should be covered by the protection scope of the present application.

Claims

1. A steel arch frame for upper steps of a highway tunnel, characterized in that: The circular arc steel arch frame (1) comprises oblique supporting legs (2) arranged on two outer sides of the circular arc steel arch frame (1), and the oblique supporting legs (2) and the circular arc steel arch frame (1) are connected via a cross bar (3).

2. The steel arch frame for upper steps of a highway tunnel according to claim 1, characterized in that: The arc steel arch frame (1), the oblique supporting legs (2) and the crossbar (3) are welded into a whole using the same type of steel.

3. The steel arch frame for upper steps of a highway tunnel according to claim 1, characterized in that: The included angle between the oblique supporting legs (2) and the circular arc steel arch frame (1) is 17°.

4. The steel arch frame for upper steps of a highway tunnel according to claim 1, characterized in that: The angle between the line connecting the lower end of the oblique support leg (2) and the end of the arc steel arch frame (1) and the horizontal line is 30°.

5. The steel arch frame for upper steps of a highway tunnel according to claim 1, characterized in that: The end of the circular arc steel arch frame 1 is connected to a foot locking anchor rod (4).

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