CN216360618U - Protection architecture suitable for ultra-shallow tunnel shield that buries wears existing highway subgrade down - Google Patents
Protection architecture suitable for ultra-shallow tunnel shield that buries wears existing highway subgrade down Download PDFInfo
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- CN216360618U CN216360618U CN202121956634.6U CN202121956634U CN216360618U CN 216360618 U CN216360618 U CN 216360618U CN 202121956634 U CN202121956634 U CN 202121956634U CN 216360618 U CN216360618 U CN 216360618U
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Abstract
The utility model provides a protection structure suitable for a shield of an ultra-shallow buried tunnel to penetrate through an existing highway subgrade. The method solves the floating problem of the ultra-shallow buried tunnel in the construction process while ensuring the normal operation of the highway, controls the deformation of the highway structure and lightens the influence of the load on the deformation of the lower tunnel structure in the highway operation period.
Description
Technical Field
The utility model relates to tunnel engineering and highway subgrade engineering, which is suitable for the condition that an ultra-shallow tunnel shield penetrates through an existing highway subgrade.
Background
When the existing expressway subgrade is worn down for shield construction, the following difficult problems exist:
1. in the tunnel shield construction process, the tunnel can receive larger buoyancy due to higher underground water level. Under the condition of ultra-shallow burying, the vertical pressure of upper covering soil is not enough to provide counter force, so that the tunnel floats upwards, the linear deviation design of the longitudinal section of the line is caused, and the highway subgrade is easy to deform greatly and even damage.
2. Because the tunnel buried depth is shallow, the shear strength of foundation soil is low, the soil body is disturbed during construction to reduce the strength, and the grouting slurry strength cannot be formed immediately, the soil body is easy to overexcavate and the like during the shield construction process, so that the highway subgrade is excessively settled to influence the normal use of the highway subgrade, and the traffic safety is damaged.
3. After the construction of the shield tunnel is completed, the transverse deformation of the tunnel structure is aggravated by the heavy earth covering on the tunnel and the load of the expressway in the operation period, so that the problems of segment cracking, water leakage and the like are caused, and the potential safety hazard is brought to subsequent train operation. Therefore, a protection structure capable of distributing the load above the tunnel and reducing the structural deformation is needed.
Aiming at the problem of tunnel floating, the current common practice is to install an uplift pile downwards from the tunnel, so that the uplift pile is anchored on the foundation below, and an anti-floating counter force is provided. But the anti-pulling pile is arranged, holes must be drilled or reserved on the pipe piece to fix the pile end, and the strength and the waterproof effect of the tunnel are adversely affected. Further, the above problems 2 and 3 cannot be solved by simply installing the uplift pile. Therefore, there is still a need for a structure capable of bi-directional load bearing, in which case the tunnel and the roadbed are protected.
SUMMERY OF THE UTILITY MODEL
Aiming at three difficult problems of the ultra-shallow shield tunnel passing through the highway subgrade, the utility model designs a protection structure which can simultaneously meet the requirements of bearing upper load and resisting floating.
Technical scheme
A protection structure suitable for an ultra-shallow shield tunnel to penetrate through an existing highway subgrade, wherein the existing highway subgrade comprises subgrade filling 1 and a replacement filling layer D, and a shield tunnel 3 is arranged in foundation soil 2;
the support system comprises an internal ramming pile A, a crown beam B and a cover plate C;
the inner ramming piles A take 3 transversely arranged piles as one group (taking two shield tunnels 3 as an example), separate the shield tunnels 3, and arrange a plurality of groups at intervals along the longitudinal direction of the tunnel;
the crown beam B extends longitudinally along the tunnel and connects a plurality of groups of internal ramming piles A;
the crown beam B fixes the inner ramming pile A and the shroud plate C at the top; the built-in rammed pile A in order stands in the forest and forms an isolation space for the shield tunnel (3), so that buoyancy is obtained in foundation soil (2) to maintain stress balance; the cover plate C is tightly attached to the replacement cushion layer D.
Specifically, the crown beam B is connected with the inner ramming pile A and the shroud plate C respectively in a mode of arranging a steel bar joint, and the steel bar joint is arranged. Thereby transferring the action borne by the sheathing C to the inside ramming pile a. And the filling replacing cushion layer D is positioned above the cover plate C and the crown beam B.
Specifically, the method comprises the following steps:
the inner rammed pile A adopts a pipe sinking rammed pile, namely the lower end of the pile is provided with an enlarged head formed by inner rammed expanded bottom. As an example, the internal tamper pile a is a round pile, containing an enlarged head portion a 2. The enlarged head portion a2 is a concrete structure; the pile upper part A1 is of a reinforced concrete structure and is provided with longitudinal bars and spiral stirrups.
The internal rammer pile A is a stressed core component. The axial main force is transmitted by the crown beam B, and the counter force is provided by the side friction resistance and the end force of the pile. The enlarged head of the inner ramming pile A plays a role in improving the pile end force and providing the pile end with pulling resistance.
The crown beam B is of a cast-in-place reinforced concrete structure. The crown beam B plays a role in weight pressing, pulling resistance and transmission. The crown beam B provides plate-side up or down counterforce to the plate C and transfers the counterforce to the internal ramming pile A.
The shroud plate C is of a cast-in-place or prefabricated reinforced concrete structure, and reinforcing bars are arranged according to the unidirectional plates. The shroud plate C is a component for directly bearing roadbed load or tunnel floating load, and transmits the load to the inner ramming pile A through the crown beam B.
The filling pad layer D adopts filler with good grain diameter and grading to reduce the settlement of the roadbed structure in the operation period. The grading is not an inventive task of the present technical solution.
Drawings
FIG. 1 shows the structure of the embodiment perpendicular to the extending direction of the tunnelTransverse sectionAnd (7) a surface diagram.
FIG. 2 shows the structure of the embodiment along the extending direction of the tunnelLongitudinal sectionAnd (7) a surface diagram.
Fig. 3 is a force analysis diagram of the upper part of the arch of the structure of the utility model.
Fig. 4 is a force analysis diagram of the lower part of the arch of the structure of the utility model.
Reference numerals:
1, filling soil in a roadbed; 2 is foundation soil; 3, a shield tunnel; a1 and A2 are internal ramming piles (the whole is marked as A, the pile upper part A1 and the enlarged head part A2); b is a crown beam; c is a shroud plate; d is the replacement of the filling cushion layer.
Detailed Description
The protective structure is used for proper operation so that it functions as intended and minimizes the adverse effects of construction on highway vehicle traffic.
In the field, the foundation soil 2 is a soil body below an original roadbed structure, is saturated soil below an underground water level, and is a solid-liquid two-phase system. Wherein, the water in the soil generates buoyancy to the shield tunnel 3, and the solid particles in the soil transmit the buoyancy received by the shield segment of the shield tunnel 3 to the shroud plate C, and provide frictional resistance at the side of the inner ramming pile A, thereby having multiple functions.
Examples
Take the shield tunnel design with two tunnels as an example.
The protection structure consists of an internal ramming pile A, a crown beam B and a cover plate C. The internal ramming piles A are arranged in groups of 3 transversely arranged piles at intervals along the longitudinal direction of the tunnel. The crown beams B and the skin panels C extend longitudinally along the tunnel.
The structure should be implemented according to the following steps:
1. and (4) closed excavation: and a half road in the underpass range of the tunnel is closed, and a transition section with enough length is reserved, so that the traffic safety is ensured. And excavating a closed half road to the bottom surface elevation of the design covering plate C.
2. Piling: placing a prefabricated pile tip, sinking the pipe to a preset depth, pouring concrete at the pile end, expanding the bottom by using a static pressure method to form an expanded head, placing a steel reinforcement cage, and pouring concrete at the pile body. The pile top is above the ground to reach the designed position, and a steel bar joint extending into the crown beam B is reserved. The piling operation is symmetrically carried out.
3. Building a covering plate: and (5) placing a steel reinforcement cage of the shroud plate C, reserving a steel reinforcement joint penetrating into the crown beam B, and pouring concrete. Prefabricated one-way plates can also be used, but care is taken to reserve the rebar junctions during prefabrication.
4. Building a capping beam: and placing a steel reinforcement cage of the crown beam B at a design position, welding the steel reinforcement cage with the steel reinforcement joints of the uplift pile A and the sheathing board C, and pouring concrete to enable the crown beam B, the uplift pile A and the sheathing board C to form a rigid frame.
5. Laying a filling layer and compacting.
6. Restoring a half-width pavement: and (4) paving a roadbed underlayer 2 on the covering plate C again, rebuilding a roadbed 1, compacting and paving a pavement structure again.
7. And constructing the other half of the pavement lower structure.
The dimensions of the components should not only meet the requirements of the intended load distribution and pull-out resistance, but also the requirements of the strength of the components themselves and the constructional requirements at the edges and joints. During design, the size of each component, the burial depth of the internal ramming pile A, the horizontal pile distance and the longitudinal pile distance can be assumed according to construction requirements and related engineering experience, checking calculation is carried out according to requirements, and the internal force of the structure is obtained after the checking calculation.
And (3) carrying out stress analysis on the protection structure according to the uplift pile under the working condition of tunnel floating, and respectively analyzing and calculating the structures above and below the arch waist of the tunnel by using a cross-section method according to the characteristic of ultimate damage of the uplift pile. Side friction R of limit pileskThe ratio of the pile side reaction force R to the calculated pile side reaction force is taken as a pulling-resistant safety factor K, namely
The anti-pulling safety coefficient K should meet the corresponding requirements.
And (3) calculating the pile side reaction force R according to the stress balance of the structure with the arch waist as follows:
R＝Fn-WAX
in the formula: wAXThe gravity of each internal ramming pile A in the lower isolated body; fnThe axial force of the uplift pile on the arch waist section is calculated according to the stress balance of the structure above the arch waist and the following formula:
in the formula: fFTotal floating force of shield tunnel for every meter；W1Filling the roadbed with 1 gravity per linear meter; wDChanging the gravity of the filling layer D for each linear meter; w2The gravity of foundation soil 2 in the upper isolation body per linear meter; w3The gravity of the shield tunnel 3 per linear meter; wASThe gravity of each internal ramming pile A in the upper isolated body; wBIs the gravity of the crown beam B between two piles; wCThe weight of the sheathing C between two sets of piles.
When the uplift pile with the expanded head is damaged in a limiting way, the diameter of the lower pile body (5D above the pile bottom) is equivalent to the diameter D of the expanded head, and the limit frictional resistance of the pile side is calculated according to the diameter. Considering negative friction pile group effect, limit pile side friction R of each uplift pile AskCalculated as follows:
Rsk＝ηn·∑λiqsikuili
in the formula: lambda [ alpha ]iTaking a value according to the soil property type for the uplift coefficient; q. q.ssikTaking a value of a standard value of the compressive limit side resistance of the ith layer of soil on the pile side according to the soil quality type and the state; u. ofiIn order to destroy the perimeter of the surface, pi D or pi D is taken according to the distance from the pile bottom; liThe thickness of the ith layer of soil on the pile side; etanThe pile group effect coefficient is calculated according to the following formula:
in the formula: sax、sayThe center distance of the transverse pile and the longitudinal pile is used;
the weighted average value of the standard values of the resistance of the pile side limit sides of all soil layers of the lower isolation body is obtained; gamma's'mThe weighted average value of the effective gravities of all soil layers of the lower isolated body is obtained.
Claims (4)
1. A protection structure suitable for an ultra-shallow buried tunnel shield to penetrate through an existing highway subgrade, wherein the existing highway subgrade comprises subgrade filling soil (1) and a replacement filling cushion layer (D), and a shield tunnel (3) is arranged in foundation soil (2), and the protection structure is characterized in that the protection structure is a support system, is constructed in the foundation soil (2), is arranged at the periphery of the shield tunnel (3), and is combined with the shield tunnel (3) to obtain stress balance in the foundation soil (2);
the support system comprises an internal ramming pile (A), a crown beam (B) and a shroud plate (C);
the inner ramming piles (A) take 3 transversely arranged piles as a group, separate two shield tunnels (3), and arrange a plurality of groups at intervals along the longitudinal direction of the tunnels;
the crown beam (B) extends longitudinally along the tunnel and connects a plurality of groups of internal ramming piles (A);
the top of the crown beam (B) fixes the inner ramming pile (A) and the shroud plate (C); the inner ramming pile (A) in order standing forms an isolation space for the shield tunnel (3), so that buoyancy is obtained in the foundation soil (2) to maintain stress balance; the cover plate (C) is tightly attached to the filling pad layer (D).
2. The protection structure suitable for the ultra-shallow tunnel shield to penetrate the roadbed of the existing expressway according to claim 1, wherein the crown beam (B) is respectively connected with the inner ramming pile (A) and the cover plate (C) by arranging a steel bar joint and is provided with a steel bar joint; thereby transmitting the action born by the shroud plate (C) to the internal ramming pile (A); the filling replacing cushion layer (D) is positioned above the cover plate (C) and the crown beam (B).
3. The protection structure for the ultra-shallow tunnel shield tunneling through the roadbed of the existing expressway as claimed in claim 1 or 2, wherein the inner ramming pile (A) is a pipe sinking rammed pile, i.e. the lower end of the pile is provided with an enlarged head formed by an inner ramming enlarged base.
4. The protection structure for the shield tunneling of an ultra-shallow tunnel penetrating an existing highway subgrade according to claim 3, wherein the inner ramming pile (A) is a circular pile having an enlarged head part (A2); the enlarged head part (A2) is of a concrete structure; the pile upper part (A1) is of a reinforced concrete structure and is provided with longitudinal bars and spiral stirrups.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
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| CN202121070868 | 2021-05-19 | ||
| CN2021210708680 | 2021-05-19 |
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| CN216360618U true CN216360618U (en) | 2022-04-22 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116791422A (en) * | 2023-08-28 | 2023-09-22 | 创辉达设计股份有限公司 | Expressway roadbed structure suitable for soft soil stratum and construction method thereof |
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2021
- 2021-08-19 CN CN202121956634.6U patent/CN216360618U/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116791422A (en) * | 2023-08-28 | 2023-09-22 | 创辉达设计股份有限公司 | Expressway roadbed structure suitable for soft soil stratum and construction method thereof |
| CN116791422B (en) * | 2023-08-28 | 2023-11-07 | 创辉达设计股份有限公司 | Expressway roadbed structure suitable for soft soil stratum and construction method thereof |
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