A tunnel arch structure and technology for reinforcing soft soil layers by setting locking feet in advance

Abstract

The present invention belongs to the technical field of tunnel construction, and specifically relates to a tunnel arch frame structure and process for reinforcing soft soil layers by installing locking feet in advance. By installing locking feet conduits in advance on the ground and installing locking feet conduits in advance on middle and lower steps in an upper step hole, the time for locking feet construction is saved, the time for soil exposure after each step excavation is shortened, and the anti-subsidence capacity of the steel arch frame connected thereto is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel construction, and in particular relates to a tunnel arch frame structure and process for reinforcing a soft soil layer by setting locking feet in advance. Background Art

[0002] During the construction of underground tunnels for railways, highways, municipal engineering, water conservancy, etc., especially during the construction of urban underground roads, when using the underground shallow buried tunnel method to build expressways under the ground roads that have been built and opened to traffic, if the geological conditions are soft soil layers, tunnel settlement control is particularly critical. Because there are many pipelines on the ground roads and the traffic volume on the ground roads is large, if the settlement cannot be controlled in time, it will cause: ground collapse, pipeline bursting, traffic interruption, and will have a greater adverse social impact. The tunnel excavation process will cause disturbances to the soil. Only by accelerating the closure of the face, reducing the exposure time of the soil, and allowing the initial support steel arch frame to be stressed as soon as possible, especially the arch frame foot is supported as soon as possible, can the settlement be minimized.

[0003] Because the excavation is carried out in the soft soil layer, the arch foot of the steel arch frame cannot be applied to the solid part of the soil layer. It is necessary to drive the locking foot conduit sideways to the soil body to lock the steel arch frame in time, and reduce the settlement of the arch frame by the force of the locking foot. In this way, the locking foot conduit needs to be driven in time to provide locking force to the steel arch frame as soon as possible. However, it takes a certain amount of time to drive the locking foot conduit. Generally, the length of the locking foot conduit is 3.5-4 meters, and it takes about 30-40 minutes to drive and grout the conduit in the soil layer. One arch foot is designed with 2-4 conduits, which takes a total of 2-3 hours. In addition, the driving process will cause secondary disturbance to the soil exposed by the excavation, delay the time of shotcrete support on the excavation surface, and further increase the settlement of the tunnel and the surface. How to shorten the time of face closure and increase the force of the locking foot conduit is the key to reducing the settlement of the tunnel in the soft soil layer. According to engineering practice, tunnel excavation is generally divided into three steps: upper, middle and lower. The locking feet at the arch feet at the nodes of the upper and middle steps and the locking feet at the middle and lower nodes are the key points for controlling settlement during the entire tunnel excavation process. Summary of the invention

[0004] In order to solve the deficiencies of the prior art, the present invention provides a tunnel arch frame structure and process for reinforcing a soft soil layer by setting locking feet in advance.

[0005] The present invention is achieved through the following technical solutions:

[0006] A tunnel arch structure with advance locking feet for reinforcing soft soil layers, wherein the locking foot conduit at the arch foot position of the upper step steel arch frame is a ground advance locking foot conduit, which is driven in advance from the ground, and is connected to the upper step steel arch frame; the locking foot conduit at the arch foot position of the middle step steel arch frame is a middle-lower step advance locking foot conduit, which is driven in advance from the upper step, and is connected to the middle step steel arch frame; the ground advance locking foot conduit and the middle-lower step advance locking foot conduit are both grouting.

[0007] The above-mentioned construction process of pre-installing locking feet to reinforce the tunnel arch structure in soft soil layer includes the following steps:

[0008] (I) Design the position and installation angle of the ground advance locking foot guide tube for ground advance installation;

[0009] (ii) Install the ground advanced locking foot guide tube according to the design;

[0010] (III) Ground advanced locking foot duct grouting;

[0011] (iv) Excavation of the upper step in the tunnel, connection of the upper step steel arch frame with the ground advanced locking foot guide tube;

[0012] (V) Installing the forward locking foot guide tube for the middle and lower steps when ascending the steps;

[0013] (VI) Grouting of the middle and lower steps with advanced locking foot guide tubes;

[0014] (VII) Excavation of the middle step in the tunnel, connection of the middle step steel arch frame and the middle and lower step advance locking foot guide tube;

[0015] (8) Excavate the lower step and complete the initial support to form a closed ring.

[0016] As a preferred option:

[0017] In the step (ii), the spacing of the ground advance locking foot guide tubes along the longitudinal direction of the tunnel is consistent with the designed spacing of the steel arch frames in the tunnel, and the hole layout area is set within the excavation and erection range of the steel arch frames.

[0018] In the step (ii), the angle between the ground advance locking foot guide and the vertical direction is 10-40°; in the step (v), the angle between the middle and lower steps advance locking foot guide and the vertical direction is 10-40°.

[0019] In the step (ii), if the ground road structure layer is relatively stable and the hole will not collapse after drilling, an empty hole can be left, and the ground advanced locking foot guide tube is actually laid only within the tunnel range.

[0020] In the steps (ii) and (v), the ground advance locking foot guide tube and the middle and lower step advance locking foot guide tube are driven downward beyond the arch foot position and the anchoring length is 4-6 meters.

[0021] In the step (iv), the excavation height of the upper step is controlled at 3-4 meters.

[0022] In the steps (iv) and (vii), the upper step steel arch frame is connected to the ground advance locking foot conduit, and the middle step steel arch frame is connected to the middle and lower step advance locking foot conduit by welding the annular clamp through the steel bar.

[0023] In the step (five), if the stratum is stable and there is no hole collapse after drilling, the hole is drilled directly using a drilling rig, and the middle and lower step advance locking foot guide tube is placed at the designed position of the middle and lower step arch angle; if the stratum is poor and there is hole collapse, full casing drilling is adopted, and after the hole is drilled, the middle and lower step advance locking foot guide tube is lowered to the designed position, and the casing is lifted out.

[0024] The ground advance locking foot guide tube and the middle and lower step advance locking foot guide tube are made of steel pipes with a diameter of 79mm or 108mm.

[0025] Through multiple process tests, the present invention proposes a scheme of driving the locking feet at the arch foot position at the node of the middle step steel arch frame in advance on the ground, and driving the locking feet at the middle and lower nodes in the upper step hole that has been closed and constructed. The present invention can drive the locking foot conduit in advance of the excavation mileage of the heading face and reinforce it with grouting according to the ground traffic and pipeline layout conditions. Because the operating space of the present invention is large and the operation time can be extended, the driving depth of the locking foot conduit can be lengthened, and the driving length can be lengthened to 4-6 meters; at the same time, the diameter of the locking foot conduit is increased, and a steel pipe with a diameter of 79mm or 108mm can be selected as the locking foot conduit of the tunnel support steel arch frame according to the stratum and the surrounding environment. In this way, the anchoring force between the locking foot conduit and the soil is increased in terms of length and diameter, and the anti-settling ability of the steel arch frame connected thereto is improved.

[0026] The scheme of the present invention is particularly effective in the construction of shallow buried and dark excavated large-span tunnels in cities, when the tunnel is in a soft soil layer and ground settlement is difficult to control. By setting up the ground advance locking foot conduit in advance on the ground and setting up the middle and lower step locking foot conduits in advance in the upper step hole, the time for locking foot construction is saved and the time for soil exposure after each step excavation is shortened. In the existing construction process, the locking foot conduit is installed synchronously with the steel arch frame, which takes a lot of time. It is unsafe if the exposure time is too long, and the pipe diameter is small, the contact area with the soil is small, and the anchoring force is small.

[0027] The present invention simultaneously reinforces the vault soil through ground advance locking foot conduit grouting, and can also play a role of advance support for the tunnel vault, reducing the lateral pressure of the tunnel vault; and simultaneously reinforces the invert soil through middle and lower step advance locking foot conduit grouting, which can effectively increase the foundation bearing capacity of the tunnel invert soil and reduce tunnel settlement.

[0028] The effective effects of the present invention are integrated together to play an obvious role in strengthening the tunnel as a whole and reducing the settlement. The present invention has simple steps, strong operability, saves construction space, and has significant economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of the present invention.

[0030] In the figure, 1 is the upper step, 2 is the middle step, 3 is the lower step, 4 is the ground advance locking foot guide, 5 is the middle and lower step advance locking foot guide, and 6 is the ground. DETAILED DESCRIPTION

[0031] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0032] A tunnel arch structure with advance locking feet for reinforcing soft soil layers, wherein the locking foot conduit at the arch foot position of the steel arch frame of the upper step 1 is a ground advance locking foot conduit 4, which is a locking foot conduit driven in advance from the ground 6, and is connected to the steel arch frame of the upper step 1; the locking foot conduit at the arch foot position of the steel arch frame of the middle step 2 is a middle-lower step advance locking foot conduit 5, which is a locking foot conduit driven in advance from the upper step 1, and is connected to the steel arch frame of the middle step 2; the ground advance locking foot conduit 4 and the middle-lower step advance locking foot conduit 5 are both grouting.

[0033] The above-mentioned construction process corresponding to the arch structure of the tunnel in soft soil layer reinforced by installing locking feet in advance comprises the following steps:

[0034] (I) Designing the position and installation angle of the ground advance locking foot guide tube 4

[0035] The position and installation angle of the ground advance locking foot guide tube 4 are designed according to the design drawings, the actual measured ground elevation, the distribution of ground pipelines and the underground tunnel excavation conditions.

[0036] (II) Installation of ground advance locking foot guide tube 4

[0037] According to the designed position and angle of the ground advance locking foot conduit 4, a hole is first drilled at the designed position, and then the ground advance locking foot conduit 4 is placed. The longitudinal spacing of the tunnel is consistent with the designed spacing of the steel arch frame in the tunnel, and the hole layout area is set within the excavation and erection range of the steel arch frame, so that the steel arch frame can be effectively connected with it after excavation.

[0038] Preferably, the angle between the ground advance locking foot guide tube 4 and the vertical direction is controlled at 10-40°, and the installation length is preferably 4-6 meters longer than the node of the steel arch frame of the upper and middle steps 2.

[0039] According to the distribution situation, if the geological structure of the ground road is hard, the empty hole can be left in the ground road structure layer because the structure is relatively stable and the hole will not collapse after drilling. The 4 ground advance locking foot guide tubes are actually laid only within the tunnel range.

[0040] As a preferred solution, since the tunnel burial depth is generally around 10 meters, plus the locking foot anchoring depth of 4-6 meters and the excavation depth of the upper step 1, and then minus the empty hole section, it is generally best to control the length of the ground advance locking foot guide tube 4 to be around 14-16 meters.

[0041] The number, diameter, length, etc. of the ground advance locking foot conduit 4 can be appropriately increased according to the stratum and surrounding environment. The ground advance locking foot conduit 4 can use a steel pipe with a diameter of 79mm or 108mm.

[0042] (III) Ground advance locking foot guide tube 4 grouting

[0043] After the ground advance locking foot conduit 4 is set up, cement single liquid slurry is injected. Grouting through the ground advance locking foot conduit 4 can simultaneously reinforce the vault soil, and can also play a role in advance support for the tunnel vault, reducing the lateral pressure on the tunnel vault.

[0044] (IV) Excavation of upper step 1 in the tunnel

[0045] The ground advanced locking foot guide tube 4 set on the ground 6 is mainly used to reinforce the steel arch frame of the upper step 1. In order to ensure construction safety, reduce settlement and facilitate locking foot construction, the excavation height of the tunnel upper step 1 is minimized as much as possible, and the excavation height of the upper step 1 is controlled to meet the normal construction work space. Preferably, the excavation height of the upper step 1 is controlled within 3-4 meters, which can meet the needs of manual operation with small drilling rigs, conventional excavation equipment construction, etc.

[0046] When the upper step 1 in the tunnel is excavated, the above-mentioned advance ground locking foot conduit 4 is exposed. According to the position of the ground advance locking foot conduit 4 and the set position of the steel arch frame, appropriate fine adjustments are made. The steel arch frame of the upper step 1 and the ground advance locking foot conduit 4 are effectively connected by welding with steel bar support bars through annular clamps to ensure that the steel arch frame is fixed by the ground advance locking foot conduit 4.

[0047] (V) Installing the mid-down step advance lock foot guide tube 5 during the upper step 1

[0048] After the upper step 1 is constructed for a certain length in the tunnel and the working surface is formed, the working space of the upper step 1 is used to advance the middle and lower step advance locking foot guide tube 5 at the middle and lower step node in the tunnel. The arch foot position of the middle and lower step node of the left and right steel arch frames bears the weight of the entire tunnel, which is particularly critical for controlling the overall settlement of the tunnel. The arrangement spacing, driving length and angle of the middle and lower step advance locking foot guide tube 5 at the arch foot position of the middle and lower step node steel arch frame are calculated according to the excavation height of the upper step 1 and the spacing of the steel arch frame.

[0049] When the locking feet of the middle and lower steps are advancedly drilled from the upper step 1, the remaining excavation height of the middle and lower steps is calculated according to the excavation height of the upper step 1. Within this height, if the stratum is relatively stable and there is no hole collapse after drilling, the middle and lower step advance locking foot guide tube 5 is placed at the designed position of the middle and lower step arch angle after drilling with a drilling rig directly; if the stratum is poor and there is a hole collapse phenomenon, full casing drilling is adopted, and after drilling, the middle and lower step advance locking foot guide tube 5 is lowered to the designed position after drilling, and the casing is pulled out.

[0050] Preferably, the angle between the middle and lower step advance locking foot guide tube 5 and the vertical direction is controlled at 10-40°.

[0051] Because the operating space is large, the operation time can be extended, and the driving depth of the middle and lower step advance locking foot catheter 5 can be lengthened. Preferably, the anchoring length of the middle and lower step advance locking foot catheter 5 is 4-6 meters.

[0052] According to the stratum and surrounding environment, the number, diameter, length, etc. of the middle and lower step advance locking foot guide tubes 5 can be appropriately increased, and steel pipes with a diameter of 79mm or 108mm can be selected as the advance locking foot guide tubes of the tunnel support steel arch frame.

[0053] In this way, the anchoring length and diameter of the advanced locking foot guide tube are increased, and the anti-settlement capacity of the steel arch frame connected thereto is improved.

[0054] (VI) Grouting of the middle and lower step forward locking foot guide tube 5

[0055] After the installation is completed, the middle and lower step advance locking foot pipe 5 is injected with cement single liquid slurry. The advance locking foot pipe grouting is used to reinforce the invert soil at the same time, which can effectively increase the foundation bearing capacity of the tunnel invert soil and reduce tunnel settlement.

[0056] (VII) Excavation of middle step 2 in the tunnel

[0057] When the middle step 2 in the tunnel is excavated, the above-mentioned advance locking foot conduit 5 for the middle and lower steps is exposed. According to the position of the advance locking foot conduit 5 for the middle and lower steps and the set position of the steel arch frame, appropriate fine adjustments are made. The middle step 2 steel arch frame and the middle and lower step advance locking foot conduit 5 are effectively connected by welding with steel bar support bars through annular clamps to ensure that the steel arch frame is fixed by the middle and lower step advance locking foot conduit 5.

[0058] (VIII) Excavate lower step 3 and complete the initial support closure to form a ring.

[0059] The embodiment described above is only one of the more preferred specific implementations of the present invention. Common changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A process for reinforcing a tunnel arch frame in a soft soil layer by installing locking feet in advance, characterized in that: It comprises a pre-installed locking foot reinforcement soft soil layer tunnel arch frame structure, the pre-installed locking foot reinforcement soft soil layer tunnel arch frame structure comprises a locking foot conduit at the arch foot position of the upper step (1) steel arch frame, which is a ground pre-installed locking foot conduit (4), the ground pre-installed locking foot conduit (4) is a locking foot conduit installed in advance from the ground (6), and the ground pre-installed locking foot conduit (4) is connected to the upper step (1) steel arch frame; The locking foot conduit at the arch foot position of the steel arch frame of the middle step (2) is a middle-lower step advance locking foot conduit (5), the middle-lower step advance locking foot conduit (5) is a locking foot conduit set in advance from the upper step (1), and the middle-lower step advance locking foot conduit (5) is connected to the steel arch frame of the middle step (2); the ground advance locking foot conduit (4) and the middle-lower step advance locking foot conduit (5) are both grouting; the advance locking foot setting process for strengthening the soft soil layer tunnel arch frame comprises the following steps: (i) Designing the position and installation angle of the ground advance locking foot guide tube (4) installed on the ground in advance; (ii) installing the ground advance locking foot guide tube (4) according to the design; (iii) Grouting of the ground advance locking foot guide tube (4); (iv) excavating the upper step (1) in the tunnel, connecting the steel arch frame of the upper step (1) and the advanced locking foot guide tube (4) on the ground; (5) installing the mid-lower step advance locking foot guide tube (5) while the upper step (1) is being performed; (vi) Grouting of the middle and lower step forward locking foot guide tube (5); (VII) excavating the middle step (2) in the tunnel, connecting the steel arch frame of the middle step (2) and the advanced locking foot guide tube (5) of the middle and lower steps; (VIII) Excavate the lower step (3) and complete the initial support and closure to form a ring.

2. The process for reinforcing a tunnel arch frame in soft soil by installing locking feet in advance according to claim 1 is characterized in that: In the step (ii), the ground advanced locking foot guide tubes (4) are placed at a spacing along the longitudinal direction of the tunnel that is consistent with the design spacing of the steel arch frame in the tunnel, and the hole arrangement area is set within the excavation and erection range of the steel arch frame.

3. The process for reinforcing a tunnel arch frame in soft soil by installing locking feet in advance according to claim 1 is characterized in that: In the step (ii), the ground advance locking foot guide tube (4) is set at an angle of 10-40° with the vertical direction; in the step (v), the middle and lower step advance locking foot guide tube (5) is set at an angle of 10-40° with the vertical direction.

4. The process for reinforcing a tunnel arch frame in soft soil by installing locking feet in advance according to claim 1 is characterized in that: In the step (ii), if the ground road structure layer is relatively stable and the hole will not collapse after drilling, an empty hole can be left, and the ground advanced locking foot guide tube (4) is actually laid only within the tunnel range.

5. The process for reinforcing a tunnel arch frame in soft soil by installing locking feet in advance according to claim 1 is characterized in that: In the steps (ii) and (v), the anchoring lengths of the ground advance locking foot guide tube (4) and the middle and lower step advance locking foot guide tube (5) are both 4-6 meters.

6. The process for reinforcing a tunnel arch frame in soft soil by installing locking feet in advance according to claim 1 is characterized in that: In the step (iv), the excavation height of the upper step (1) is controlled at 3-4 meters.

7. The process for reinforcing a tunnel arch frame in soft soil by installing locking feet in advance according to claim 1 is characterized in that: In the steps (iv) and (vii), the upper step (1) steel arch frame is connected to the ground advance locking foot conduit (4), and the middle step (2) steel arch frame is connected to the middle and lower step advance locking foot conduit (5) by welding the annular clamp through the steel bar.

8. The process for reinforcing a tunnel arch frame in soft soil by installing locking feet in advance according to claim 1 is characterized in that: In the step (v), if the stratum is stable and the hole collapse does not occur after the hole is formed, the hole is formed directly by using a hole forming drill, and the middle and lower step advance locking foot guide tube (5) is placed at the designed position of the middle and lower step arch angle; if the stratum is poor and the hole collapse occurs, full casing drilling is adopted, and after the hole is formed, the middle and lower step advance locking foot guide tube (5) is lowered to the designed position, and the casing is raised.

9. The process for reinforcing a tunnel arch frame in soft soil by installing locking feet in advance according to claim 1 is characterized in that: The ground advance locking foot guide tube (4) and the middle and lower step advance locking foot guide tube (5) are made of steel pipes with a diameter of 79 mm or 108 mm.

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