A soft soil layer small clear distance shield end reinforcement system and its design method

Abstract

The invention relates to a small-clearance shield end reinforcement system for soft soil strata and a design method thereof, comprising an end reinforcement zone and an extended reinforcement zone, wherein the end reinforcement zone is arranged within a certain range outside an end well, an end reinforcement body is inserted into the end reinforcement zone, and the end reinforcement body is arranged between two shield tunnels; the extended reinforcement zone is arranged outside the end reinforcement zone, an extended reinforcement body is arranged in the extended reinforcement zone, the extended reinforcement body is arranged between the two shield tunnels, and part of the extended reinforcement body enters the range of the end reinforcement zone as a transition section. The advantages of the invention are: reducing the structural clear distance of parallel constructed shield tunnels at the end well position; compressing the line spacing under the premise of ensuring the safety of the project, reducing the land area occupied in the urban built-up area during construction, shortening the station length and saving the project construction cost; and minimizing the disturbance of the surrounding strata caused by the parallel shield construction, isolating the strong influence area of ​​the adjacent tunnels.

Description

Technical Field

[0001] The invention relates to the technical field of shield tunnel engineering, in particular to a small-clearance shield end reinforcement system for soft soil strata and a design method thereof. Background Art

[0002] With the gradual development of urban modernization, more and more cities choose to develop underground space to solve urban traffic problems. The construction of underground tunnel projects in urban traffic-intensive areas has become a necessary solution. With the advancement of tunnel engineering technology and the increase in traffic capacity requirements, tunnel sections are getting larger and larger, and the application scope of large and super-large shields is becoming more and more extensive, especially for high-speed railways, intercity railways, urban railways, and high-speed rail transit, which usually use two large-diameter shields for parallel construction. When constructing in urban built-up areas, they will directly face the contradiction between the large area of ​​land required for engineering construction and the cramped available space in the city. For example, in the construction of underground rail transit, the line spacing required for the start or reception of the shield at the end of the side station is usually greater than the line spacing at the station platform position. Therefore, it is necessary to extend the length of the station until the minimum clearance requirement for the safe start or reception of the shield is met. Extending the length of the station will not only increase the scale of engineering construction, leading to an increase in investment, but also increase the area of ​​land used for engineering construction, leading to an increase in urban traffic pressure. Therefore, in order to meet the needs of urban construction, it is particularly important to use new engineering and technical solutions to reduce the minimum safe clearance required for the start or reception of the shield. Summary of the invention

[0003] The purpose of the present invention is to provide a shield end reinforcement system with small clearance in soft soil strata and a design method thereof in accordance with the above-mentioned deficiencies of the prior art. The system inserts an end reinforcement body into the end reinforcement area to enhance the structural deformation resistance stiffness of the strata between the shields, locally extends the end reinforcement range in the small line spacing section, and adopts the method of extending the reinforcement body isolation in the extended reinforcement area to isolate the strong mutual influence zone caused by the parallel construction of the shields with small clearance, so as to prevent the influence zones of two adjacent tunnels from overlapping each other when the line spacing is too small, thereby further expanding the strong influence zone of the tunnel and producing adverse effects on surrounding buildings and structures, thereby ultimately ensuring the safety of the shield construction.

[0004] The purpose of the present invention is achieved by the following technical solutions:

[0005] A shield end reinforcement system with small clearance in soft soil strata, used for reinforcement between a shield tunnel structure and an end well, wherein the shield tunnel structure includes two shield tunnels, and is characterized in that: the reinforcement system includes an end reinforcement zone and an extended reinforcement zone, wherein the end reinforcement zone is arranged within a certain range outside the end well, an end reinforcement body is inserted into the end reinforcement zone, and the end reinforcement body is arranged at a position between the two shield tunnels; the extended reinforcement zone is arranged outside the end reinforcement zone, an extended reinforcement body is arranged in the extended reinforcement zone, the extended reinforcement body is arranged at a position between the two shield tunnels, and a part of the extended reinforcement body enters the range of the end reinforcement zone as a transition section.

[0006] The end reinforcement bodies and the extension reinforcement bodies respectively adopt a multi-row structure; the end reinforcement bodies in each row are connected to form a whole through a crown beam, and the extension reinforcement bodies in each row are connected to form a whole through a crown beam.

[0007] The end reinforcement body and the extended reinforcement body are connected to form a whole through a connecting beam.

[0008] The end reinforcement body is an H-shaped steel, the end reinforcement area is a cement-soil mixing pile reinforcement area, and the H-shaped steel is inserted into the cement-soil mixing pile reinforcement area.

[0009] The extended reinforcement body is a double-row pile, and the inter-pile reinforcement soil layer is between the double-row piles.

[0010] The reinforcement system also includes a high-pressure rotary jet pile wall seam water-stopping body, and the high-pressure rotary jet pile wall seam water-stopping body is arranged between the end well and the end reinforcement area.

[0011] A design method for the above-mentioned soft soil layer small clearance shield end reinforcement system, characterized in that the design method comprises the following steps:

[0012] The reinforced soil layer between two parallel shield tunnels is equivalent to a component that is subjected to integral force and integral bending; the bending stiffness of the reinforced soil layer between the two shield tunnels is calculated; the thickness of the reinforced soil layer between the two shield tunnels after the end reinforcement body is inserted into the reinforced soil body is calculated; finally, the thickness of the reinforced soil layer after reducing the shield clear distance is checked to ensure that the thickness of the reinforced soil layer meets the space for the construction of the end reinforcement body.

[0013] When the distance between the two shield tunnels outside the end well reinforcement area is less than 0.6D, an extended reinforcement area and an extended reinforcement body are set between the two shield tunnels for isolation, and the reinforcement range of the extended reinforcement area and the extended reinforcement body is up to the position where the distance between the two shield tunnels is greater than or equal to 0.6D; wherein D is the outer diameter of the shield tunnel.

[0014] The advantages of the present invention are as follows: the small clear distance shield end reinforcement method for soft soil strata can reduce the structural clear distance of the parallel constructed shield tunnels at the end well position. Under the premise of ensuring the safety of the project, the line spacing is compressed, the land area occupied in the urban built-up area during construction is reduced, the length of the station is shortened, and the construction cost is saved. It also minimizes the disturbance of the surrounding strata caused by the parallel shield construction, isolates the strong influence area of ​​the adjacent tunnels, solves the problem of further increasing the influence range after the shield influence areas are superimposed on each other, and provides maximum protection for the surrounding buildings and structures; different types of shield isolation methods are used inside and outside the end reinforcement area, and engineering measures are selected according to local conditions to facilitate construction; H-shaped steel is used as an isolation body in the reinforcement body, which can be recycled after the construction is completed, saving engineering materials, and the gap after the steel is removed can provide a penetration path for grouting, which is convenient for controlling the scope of action of the grouting measures. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a plan view of the present invention;

[0016] Figure 2 It is a longitudinal sectional view of the present invention;

[0017] Figure 3 is a cross-sectional view of a medium steel reinforcement section of the present invention;

[0018] Figure 4 It is a cross-sectional view of the double-row pile isolation section in the present invention. DETAILED DESCRIPTION

[0019] The features of the present invention and other related features are further described in detail below through embodiments in conjunction with the accompanying drawings to facilitate understanding by those skilled in the art:

[0020] like Figure 1-4 As shown, marks 1-10 in the figure respectively represent: shield tunnel 1, end well 2, end reinforcement area 3, high-pressure rotary jet pile wall joint water stopping body 4, H-shaped steel 5, double row piles 6, connecting beam 7, inter-pile reinforcement body 8, crown beam 9, end weak reinforcement area 10.

[0021] Example: Figure 1-4 As shown, the soft soil stratum small clear distance shield end reinforcement system in this embodiment is set between two shield tunnels 1 and their starting or receiving end shafts 2 to reinforce the shield tunnels 1 and between the shield tunnels 1 and the end shafts 2.

[0022] Combination Figure 1 and Figure 3As shown, the reinforcement system in this embodiment includes a terminal reinforcement area 3 set outside the terminal well 2, and the gap between the terminal well 2 and the terminal reinforcement area 3 is filled with a high-pressure rotary jet pile wall seam water stop body 4 to isolate the two. The high-pressure rotary jet pile wall water stop body 4 partially wraps the terminal reinforcement area 3 and the terminal well 2 outside the scope of the terminal reinforcement area to ensure that there is no danger of water seepage, sand gushing and collapse during the start or reception process of the shield tunnel 1. Above the terminal reinforcement area 3 is set a terminal weak reinforcement area 10.

[0023] H-shaped steel 5 as the end reinforcement body is inserted into the reinforcement body between the shield tunnels 1 within the end reinforcement area 3. The H-shaped steel 5 adopts a multi-row structure with the same spacing array, and each row of H-shaped steel 5 is within the end reinforcement area 3 and extends outward from the end well 2. Crown beams 9 are arranged between each row of H-shaped steel 5 along its longitudinal extension direction, so that each row of H-shaped steel 5 is connected to form a whole, thereby improving the overall stiffness of the H-shaped steel 5 as the end reinforcement body, thereby coordinating the horizontal deformation of the H-shaped steel 5 at different positions, and further improving the reinforcement effect of the end reinforcement area 3.

[0024] In this embodiment, the end reinforcement area 3 can be reinforced with cement soil mixing piles, and the end reinforcement area 3 and the H-shaped steel 5 are combined to form SMW construction piles to effectively control the deformation of the stratum for reinforcement. The use of SMW construction piles in the end reinforcement area 3 utilizes the existing cement soil mixing piles, and the H-shaped steel 5 used can also be pulled out, the construction process is simple and the use cost is low.

[0025] Combination Figure 1 and Figure 4 As shown, an extended reinforcement zone is set in the soil layer between the shield tunnels 1 outside the end reinforcement zone 3, and the extended reinforcement zone is adjacent to the end reinforcement zone 3. Double-row piles 6 are set in the extended reinforcement zone as extended reinforcement bodies, and the soil layer between the double-row piles 6 is an inter-pile reinforcement body 8. The inter-pile reinforcement body 8 is formed by reinforcing the soil layer between the double-row piles 6, and the reinforcement method can be grouting reinforcement, etc.; the range of the inter-pile reinforcement body 8 is long and narrow, and a certain distance is left between it and the shield tunnels 1 on both sides to ensure that the inter-pile reinforcement body 8 does not invade the shield excavation range, and avoid the excavation condition of uneven hardness and softness of the strata on the left and right sides of the shield. The double-row piles 6 are also connected to form a whole by setting a crown beam 9 along their longitudinal extension direction, thereby improving the overall stiffness of the double-row piles 6 as extended reinforcement bodies, thereby coordinating the horizontal deformation of the double-row piles 6 at different positions, and further improving the reinforcement effect of the extended reinforcement zone.

[0026] In this embodiment, the pile bodies of the double-row piles 6 can be reinforced concrete bored piles. By using the support form of double-row piles 6 between the two shield tunnels 1 as an extended reinforcement area, reinforced concrete bored piles, crown beams 9, connecting beams 7 and inter-pile reinforcement bodies 8 are used for reinforcement to form an over-statically indeterminate spatial portal structure support system, which can greatly increase the lateral bending stiffness and effectively control the horizontal deformation of the shield tunnel 1.

[0027] Combination Figure 1 and Figure 2 As shown, connecting beams 7 are arranged on the top of the double-row piles 6 and the H-shaped steel 5. The connecting beams 7 connect the double-row piles 6 and the H-shaped steel 5 to form an integral structure, thereby improving the overall rigidity of the isolation measures.

[0028] In this embodiment, the connecting beam 7 adopts a grid structure, which effectively reduces the load of the connecting beam 7 while ensuring its connectivity.

[0029] like Figure 1 As shown, H-shaped steel 5 and double-row piles 6 are used as isolation and reinforcement measures for the soil layer between the shield tunnels 1. The double-row piles 6 partially enter the end reinforcement area 3. This section is used as a stiffness transition section. The stiffness of the H-shaped steel 5 and the double-row piles 6 is effectively coordinated under the connection of the connecting beam 7 to ensure the connection between the end reinforcement area 3 and the extended reinforcement area, further improving the reinforcement effect of the reinforcement system.

[0030] The soft soil layer small clearance shield end reinforcement system in this embodiment adopts the following design method:

[0031] 1) The reinforced soil layer between the parallel shield tunnels 1 is equivalent to an integrally stressed component. The reinforced soil layer between the shield tunnels 1 bears the load during the shield tunneling construction and operation, and can transfer the load to the adjacent shield tunnel. The stress of the soil layer between the parallel shield tunnels 1 can also be equivalent to an integrally bent component. According to the principle of equivalent bending stiffness, it can be concluded that inserting H-shaped steel 5 into the reinforced soil layer can increase the overall stiffness of the reinforced soil, and can reduce the thickness of the soil layer between the shields while ensuring that the overall stiffness remains unchanged.

[0032] 2) The minimum clear distance d0 of the parallel tunnel in the working shaft section of the shield method should not be less than 0.6D, that is, d0 ≥ 0.6D. At this time, the bending stiffness E0I0 of the soil layer between the shields can be determined by the elastic modulus and width of the reinforced soil.

[0033]

[0034]

[0035] The longitudinal thickness of the shield tunnel is taken as unit length 1m, b=1m, and we can get.

[0036]

[0037] In the above formula: D is the outer diameter of the shield, d0 is the minimum clear distance between shield tunnels 1, I0 is the moment of inertia of the reinforced soil, b is the equivalent bending member width, h is the equivalent bending member height, and E0 is the elastic modulus of the reinforced soil.

[0038] 3) After inserting H-shaped steel 5 into the soil of the reinforcement area, the stiffness of the reinforced soil layer between the shield tunnels 1 can be enhanced. When the following requirements are met, the thickness of the soil layer between the shields can be reduced.

[0039]

[0040]

[0041] In the above formula, In order to reduce the moment of inertia of the reinforced soil after the shield tunnel clearance, E s is the elastic modulus of H-beam 5, I s is the steel moment of inertia of H-shaped steel 5, and d is the thickness of the reinforced soil layer after reducing the clear distance of the shield tunnel.

[0042] Among them, the steel moment of inertia of the H-shaped steel 5 is related to its position and quantity, and satisfies the following formula:

[0043]

[0044] In the above formula, I s is the total inertia moment of the H-beam, n is the number of inserted H-beams 5, I si is the moment of inertia of the i-th H-beam 5; A si is the cross-sectional area of ​​the i-th H-beam 5, y si is the distance between the i-th H-beam 5 and the symmetry axis.

[0045] After the steel is inserted into the final reinforcement body, the thickness of the shield reinforcement body can be reduced to the value d:

[0046]

[0047]

[0048]

[0049]

[0050] 4) Finally check that the soil thickness after reducing the shield clearance is sufficient to meet the construction space H of H-beam 5.

[0051]

[0052]

[0053] In the above formula, h s is the height of the steel section, and t is the error of the steel section inserted into the cement soil.

[0054] The above design method utilizes the principle that the overall bending stiffness of the inserted steel in the soil layer of the reinforced area is equivalent to the bending stiffness of the reinforcement body between shields under the condition of minimum safe clearance. It effectively solves the problem of calculating the minimum line spacing of shields after the soil stiffness is enhanced by inserting steel in the reinforcement area of ​​the end well, and provides theoretical support for the construction of small clearance shield end reinforcement system in soft soil strata.

[0055] 5) When the spacing between parallel shield tunnels outside the end well reinforcement area does not meet 0.6D, double-row piles 6 are used to isolate the shield tunnels 1, and the soil layer between the double-row piles is reinforced. After the shield construction is completed, the parallel tunnels with small clearance often produce deformation in the horizontal direction of the adjacent tunnels. The H-shaped steel near the deformed tunnel side can be gradually pulled out, and the gaps generated during the pulling out process can be used for stratum grouting. During the grouting process, the grouting pressure will be applied to the adjacent shield segments and the unremoved steel isolation bodies as the grout is pressed into the soil. Under the blocking effect of the isolation body, the slurry will directionally reinforce the soil layer beside the tunnel, and as the slurry diffuses in the soil layer, the horizontal deformation of the shield tunnel will gradually decrease.

[0056] The above design method is applied to a certain actual project, and has the following design calculation process:

[0057] The outer diameter of the shield is D = 9.0m, E0 = 500MPa, and three rows of H-shaped steel 5 with a cross-sectional area of ​​A are inserted. s =187.21cm 2 , the moment of inertia of the steel section is I s =114350cm 4 , the center distance between adjacent rows of steel sections is y s =0.8m,

[0058]

[0059]

[0060]

[0061]

[0062]

[0063]

[0064] Finally, it is obtained that the soil thickness d≥3m after reducing the shield clearance, and the construction space requirement of H-shaped steel 5 is met. Compared with the 5.4m shield structure clearance required without isolation measures, it is reduced by 2.4m. Therefore, the design method in this embodiment can reduce the minimum safe structure clearance of the shield by 44.4%.

[0065] When the clear distance between the parallel shield tunnels 1 outside the end reinforcement area 3 does not meet 5.4m, double-row piles 6 are used for line isolation, and the soil layer between the double-row piles 6 is reinforced to form an inter-pile reinforcement body 8. When the clear distance between the parallel shield tunnels 1 is greater than 5.4m, the isolation measures can be cancelled. After the shield construction is completed, the parallel shield tunnels 1 with small clear distances often produce deformation in the horizontal direction of the adjacent tunnels. At this time, the H-shaped steel 5 close to the deformed tunnel side can be gradually pulled out, and the middle row and the H-shaped steel 5 on the farther side can be temporarily retained. The grouting holes formed by the gaps generated during the steel pulling process are used for stratum grouting. During the grouting process, the grouting pressure will be applied to the adjacent shield tunnels and the unremoved steel isolation bodies as the slurry is pressed into the soil. Therefore, the slurry will directionally reinforce the soil layer beside the tunnel, and as the slurry diffuses in the soil layer, the horizontal deformation of the shield tunnel will gradually decrease.

[0066] In the specific implementation of this embodiment: the H-shaped steel 5 inserted in the end reinforcement area 3 exposed to the ground needs to be reserved for removal conditions, the insertion depth of the H-shaped steel 5 needs to reach the bottom of the end reinforcement area 3, and the top of the H-shaped steel 5 and the double-row piles 6 needs to be provided with a cap beam 9 near the ground surface. The connecting beam 7 is rigidly connected to the top of the double-row piles 6, which can coordinate the deformation of the two rows of pile foundations and distribute the internal force, and strengthen the connection between the double-row piles 6 and the connecting beam 7 as much as possible, which can adjust the deformation and internal force characteristics of the double-row piles 6, reduce the structural displacement, and adjust the distribution of positive and negative bending moments.

[0067] In addition to the H-shaped steel 5 in this embodiment, the end reinforcement body inserted into the end reinforcement area 3 can also be, for example, an I-shaped steel, a steel sheet pile, etc.

[0068] Although the above embodiments have described in detail the concepts and embodiments of the present invention with reference to the accompanying drawings, ordinary technicians in this field can recognize that various improvements and changes can still be made to the present invention without departing from the scope of the claims, so they are not described one by one here.

Claims

1. A shield end reinforcement system with small clearance in soft soil, used for reinforcement between a shield tunnel structure and an end well, wherein the shield tunnel structure comprises two shield tunnels, and is characterized in that: The reinforcement system includes an end reinforcement area and an extended reinforcement area, wherein the end reinforcement area is arranged within a certain range outside the end well, an end reinforcement body is inserted into the end reinforcement area, and the end reinforcement body is arranged at a position between the two shield tunnels; the extended reinforcement area is arranged outside the end reinforcement area, an extended reinforcement body is arranged in the extended reinforcement area, and the extended reinforcement body is arranged at a position between the two shield tunnels, and a part of the extended reinforcement body enters the range of the end reinforcement area as a transition section; The end reinforcement bodies and the extension reinforcement bodies are respectively in a multi-row structure; the end reinforcement bodies in each row are connected to form a whole through a crown beam, and the extension reinforcement bodies in each row are connected to form a whole through a crown beam; The end reinforcement body and the extended reinforcement body are connected to form a whole through a connecting beam; The end reinforcement body is an H-shaped steel, the end reinforcement area is a cement-soil mixing pile reinforcement area, and the H-shaped steel is inserted into the cement-soil mixing pile reinforcement area; The extended reinforcement body is a double-row pile, and the inter-pile reinforcement soil layer is between the double-row piles.

2. The soft soil layer small clearance shield end reinforcement system according to claim 1 is characterized by: The reinforcement system also includes a high-pressure rotary jet pile wall seam water-stopping body, and the high-pressure rotary jet pile wall seam water-stopping body is arranged between the end well and the end reinforcement area.

3. A design method for a small clearance shield end reinforcement system in soft soil as claimed in any one of claims 1 to 2, characterized in that: The design method comprises the following steps: The reinforced soil layer between two parallel shield tunnels is equivalent to a component that is subjected to integral force and integral bending; the bending stiffness of the reinforced soil layer between the two shield tunnels is calculated; the thickness of the reinforced soil layer between the two shield tunnels after the end reinforcement body is inserted into the reinforced soil layer is calculated; finally, the thickness of the reinforced soil layer after reducing the clear distance of the shield is checked to ensure that the thickness of the reinforced soil layer meets the space for the construction of the end reinforcement body.

4. The design method of a small clearance shield end reinforcement system for soft soil strata according to claim 3 is characterized by: When the distance between the two shield tunnels outside the end reinforcement area is less than 0.6D, an extended reinforcement area and an extended reinforcement body are set between the two shield tunnels for isolation, and the reinforcement range of the extended reinforcement area and the extended reinforcement body is up to the position where the distance between the two shield tunnels is greater than or equal to 0.6D; wherein D is the outer diameter of the shield tunnel.

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