Isolation structure and method for reducing displacement of railway pile foundation caused by shield construction

Abstract

The application discloses an isolation structure and method for reducing displacement of a railway pile foundation caused by shield construction, and the isolation structure comprises underpinning beams and 2N columns of inclined piles, and N is greater than or equal to 2; the underpinning beams are located below an existing railway subgrade; each column of inclined piles comprises a plurality of inclined piles with the same inclination direction and inclination angle; the 2N columns of inclined piles are divided into two groups; the pile bottoms of one group of the inclined piles are located on one side of a to-be-constructed shield tunnel, and the pile bottoms of the other group of the inclined piles are located on the other side of the to-be-constructed shield tunnel; two adjacent columns of inclined piles in the same group are arranged in an X-shaped cross mode; the pile tops of the two groups of the inclined piles are connected with the underpinning beams and form a portal type support structure; the to-be-constructed shield tunnel passes through the portal frame surrounded by the inclined piles and the underpinning beams; and the two groups of the inclined piles are located between original railway pile foundations and the to-be-constructed shield tunnel. The application can resist the horizontal deformation of the original railway pile foundations caused by the shield tunnel construction, reduce the settlement of the railway subgrade, and effectively protect the normal operation of the railway.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of underground engineering and tunnel engineering, and particularly relates to an isolation structure and method for reducing displacement of a railway pile foundation caused by shield construction. BACKGROUND

[0002] At present, with the continuous development of the size of cities in China and the continuous increase of urban population, the ground traffic has been unable to meet the daily traffic demand, and a large number of subways need to be newly built. Since the planning of the newly built subway is relatively late, the proposed subway line will pass through a large number of structures, especially the built railway. Due to the construction of the tunnel, the soil around the tunnel will be deformed, which will cause additional displacement and additional stress of the adjacent railway pile foundation, and further affect the safety and stability of the upper structure, and seriously threaten the safety of railway operation.

[0003] There are many reinforcement methods for shield tunnel side-penetrating existing railway pile foundations, which can be summarized into two categories. One is to take protective measures for the railway pile foundation affected by shield subway construction, such as soil reinforcement around the pile foundation, or underpinning the railway pile foundation, and adding a railway pile foundation around the shield tunnel construction. The second is to set an isolation structure, including an isolation pile or an isolation wall, between the shield tunnel and the railway pile foundation to prevent the transmission of deformation.

[0004] These above-mentioned measures have a good effect on protecting the railway pile foundation. For the protection method of isolating the railway pile foundation, a straight pile is usually used to form an isolation wall between the railway pile foundation and the shield tunnel. This construction method is mainly suitable for the isolation construction of bridge pile foundations, and is not suitable for the isolation construction of railway tunnels, otherwise it will cause damage to the surface railway. In view of this, the present application proposes to punch an inclined pile. This method can punch an isolation inclined pile without affecting the railway, and achieve the isolation effect. SUMMARY

[0005] The present application provides an isolation structure and method for reducing displacement of a railway pile foundation caused by shield construction to solve the technical problems in the prior art.

[0006] The technical scheme adopted by the present application to solve the technical problems existing in the prior art is: an isolation structure for reducing displacement of a railway pile foundation caused by shield construction, the isolation structure comprising a underpinning beam and 2N columns of inclined piles, N>=2; the underpinning beam is located below an existing railway subgrade; each column of inclined piles comprises a plurality of inclined piles with the same inclination direction and inclination angle; the 2N columns of inclined piles are divided into two groups, the pile bottoms of one group of the inclined piles are located on one side of a to-be-constructed shield tunnel, and the pile bottoms of the other group of the inclined piles are located on the other side of the to-be-constructed shield tunnel; two adjacent columns of inclined piles located in the same group are arranged in an X-shaped cross manner; the pile tops of the two groups of inclined piles are connected with the underpinning beam and form a portal type support structure; the to-be-constructed shield tunnel passes through the portal frame enclosed by the inclined piles and the underpinning beam; and the two groups of inclined piles are located between the original railway pile foundation and the to-be-constructed shield tunnel.

[0007] Further, the inclination angle of the inclined piles is 20-30°.

[0008] Further, the isolation structure further comprises a grouting reinforcement body surrounding the to-be-constructed shield tunnel, and the inclined piles extend into the grouting reinforcement body.

[0009] Further, the inclined piles located on both sides of the to-be-constructed shield tunnel are symmetrically arranged about the axis of the to-be-constructed shield tunnel.

[0010] Further, the inclined piles are hollow precast piles.

[0011] Further, the pile tops of the inclined piles extend into the underpinning beam, and a plurality of steel bars are reserved at the pile tops of the inclined piles to be connected with the steel bars of the underpinning beam as a whole.

[0012] The present application further provides an isolation method for reducing displacement of a railway pile foundation caused by shield construction, the method comprising the following steps:

[0013] Step 1: precasting hollow inclined piles and reserving steel bars at the pile tops;

[0014] Step 2: performing grouting reinforcement in a to-be-constructed shield tunnel and the surrounding area below a railway subgrade;

[0015] Step 3: dividing the inclined piles into two groups and arranging them on both sides of the to-be-constructed shield tunnel, each group comprising 2-4 columns, each column comprising 4-8 inclined piles, and using a static pressure method to sink the inclined piles into the grouting reinforcement area through a pile driver; and arranging two adjacent columns of inclined piles located in the same group in an X-shaped cross manner;

[0016] Step 4: after excavating earthwork to a designed bottom elevation of the underpinning beam, applying a cushion at the bottom elevation of the underpinning beam, connecting the steel bars at the pile tops of the inclined piles with the steel bars of the underpinning beam as a whole, and pouring concrete;

[0017] Step 5: backfilling earthwork.

[0018] Further, in step 2, the size of the grouting reinforcement area is positively correlated with the groundwater pressure, the length, width and height of the grouting reinforcement area are 2-6 times of the diameter of the tunnel excavation, a plurality of grouting holes are uniformly arranged in the grouting reinforcement area, so that the grouting diffusion radius of the grouting holes covers the area of the shield tunnel; during grouting, the grouting holes are drilled first, then the steel pipes are placed in the grouting holes, and finally the grouting is carried out through the steel pipes; the grouting pressure is 1-1.5 MPa higher than the hydrostatic pressure at the grouting position.

[0019] The application has the advantages and positive effects that: the application adopts two groups of inclined piles arranged on the two sides of the shield tunnel, the pile tops of the two groups of inclined piles are connected with the underpinning beams to form a whole under common stress and constitute a gantry support structure; the shield tunnel passes through the gantry frame enclosed by the inclined piles and the underpinning beams, a plurality of inclined piles are driven into the space between the original railway pile foundation and the shield tunnel to form a partition wall, which can effectively block the influence of the shield tunnel construction on the railway. The construction method can complete the construction of the partition wall without affecting the operation of the railway. The application can isolate the influence of the soil deformation caused by the lower tunnel construction. When the shield tunnel side-penetrates the railway pile foundation, the inclined piles can be combined with the grouting reinforcement area to enhance the bearing capacity of the foundation and efficiently resist the lateral deformation of the railway pile foundation and the settlement of the railway roadbed caused by the shield tunnel construction. The application can resist the horizontal deformation of the original railway pile caused by the shield tunnel construction and reduce the settlement of the railway roadbed to effectively protect the normal operation of the railway. BRIEF DESCRIPTION OF DRAWINGS

[0020] Fig. 1 It is a perspective view of the application.

[0021] Fig. 2 It is a front view of the application.

[0022] Fig. 3 It is a top view of the application.

[0023] In the figure: 1, original railway pile; 2, railway roadbed; 3, underpinning beam; 4, inclined pile; 5, shield tunnel; 6, grouting reinforcement body. h, distance between the bottom surface of the grouting reinforcement body and the bottom surface of the shield tunnel. DETAILED DESCRIPTION

[0024] In order to facilitate the understanding of the application, the application will be described more fully below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the application is not limited to the following specific embodiments. It should be noted that the embodiments in the application and the features in the embodiments can be combined with each other without conflict.

[0025] Unless otherwise defined, all terms used in the following, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. The following description of the application uses specific terminology merely to describe certain embodiments including the best mode contemplated. No limitation of the scope of the application is intended. "An" or "one" or similar referents include one or more of whatever is being described. "Connected" or "coupled" or similar referents are not limited to direct connection, but can be indirect through other intermediate connections. "Above" or "below" or "upper" or "lower" or similar phrases do not imply any absolute position, but refer to the relative position of the described objects.

[0026] Referring to Figs. 1-3 The isolation structure for reducing displacement of railway pile foundation caused by shield construction comprises a underpinning beam 3 and 2N columns of inclined piles, N≥2. The underpinning beam 3 is located below the existing railway subgrade 2. Each column of inclined piles comprises a plurality of inclined piles 4 with the same inclination direction and inclination angle. The 2N columns of inclined piles are divided into two groups. The pile bottom of one group of inclined piles is located on one side of the to-be-constructed shield tunnel 5, and the pile bottom of the other group of inclined piles is located on the other side of the to-be-constructed shield tunnel 5. Adjacent two columns of inclined piles in the same group are arranged in an X-shaped cross manner. The pile top of the two groups of inclined piles is connected with the underpinning beam 3 and forms a portal frame support structure. The to-be-constructed shield tunnel 5 passes through the portal frame formed by the inclined piles 4 and the underpinning beam 3. The two groups of inclined piles are located between the original railway pile foundation 1 and the to-be-constructed shield tunnel 5.

[0027] Preferably, the inclination angle of the inclined pile 4 can be 20°-30°.

[0028] Preferably, the isolation structure further comprises a grouting reinforced body 6 surrounding the to-be-constructed shield tunnel 5, and the inclined pile 4 extends into the grouting reinforced body 6. According to the soil condition around the to-be-constructed shield tunnel 5, a grouting reinforced area can be arranged for grouting reinforcement. After the grouting in the grouting reinforced area is completed, the grouting reinforced body 6 is formed.

[0029] Preferably, referring to Fig. 2 The bottom surface of the grouting reinforced body 6 is lower than the bottom surface of the to-be-constructed shield tunnel 5, and the distance between the bottom surface of the grouting reinforced body and the bottom surface of the to-be-constructed shield tunnel is h.

[0030] Preferably, the inclined piles 4 located on both sides of the to-be-constructed shield tunnel 5 can be symmetrically arranged with the axis of the to-be-constructed shield tunnel 5 as the center.

[0031] Preferably, the inclined pile 4 can be a hollow precast pile.

[0032] Preferably, the top of the inclined pile 4 extends into the underpinning beam 3, and a plurality of steel bars are reserved at the top of the inclined pile 4 to be connected with the steel bars of the underpinning beam 3 as a whole.

[0033] The application further provides an isolation method for reducing displacement of railway pile foundation caused by shield construction, which comprises the following steps:

[0034] Step 1: prefabricate the hollow inclined pile 4 and reserve the steel bars at the top of the pile.

[0035] Step 2: grout and reinforce the area below the railway subgrade 2 and around the shield tunnel 5 to be constructed.

[0036] Step 3: divide the inclined piles 4 into two groups, which are arranged on the two sides of the shield tunnel 5 to be constructed, each group includes 2 to 4 rows, and each row includes 4 to 8 inclined piles 4, the inclined piles 4 are inclined and driven into the grout-reinforced area by using the static pressure method, and the adjacent two rows of inclined piles in the same group are arranged in an X-shaped cross.

[0037] Step 4: after the earthwork is excavated to the bottom elevation of the underpinning beam 3, a cushion is constructed at the bottom elevation of the underpinning beam 3, the reserved steel bars at the top of the inclined pile 4 are connected with the steel bars of the underpinning beam 3 as a whole, and the concrete is poured.

[0038] Step 5: backfill the earthwork.

[0039] Preferably, in step 2, the size of the grout-reinforced area is positively correlated with the groundwater pressure, and the length, width and height of the grout-reinforced area are 2 to 6 times the diameter of the tunnel excavation, that is, the length of the grout-reinforced area can be 2 to 6 times the diameter of the tunnel excavation, the width of the grout-reinforced area can be 2 to 6 times the diameter of the tunnel excavation, and the height of the grout-reinforced area can be 2 to 6 times the diameter of the tunnel excavation.

[0040] A plurality of grouting holes can be uniformly arranged in the grout-reinforced area, so that the grouting diffusion radius of the grouting holes covers the area of the shield tunnel 5 to be constructed; during grouting, the grouting holes can be drilled first, then a steel pipe is placed in the grouting hole, and finally grouting is performed on the surrounding rock through the steel pipe; the grouting pressure can be 1 to 1.5 MPa higher than the hydrostatic pressure at the grouting position.

[0041] The working principle of the present application is as follows:

[0042] When the shield tunnel 5 passes through the railway pile foundation, the isolation structure and method for reducing the displacement of the railway pile foundation caused by shield construction are used to reduce the adverse effects of shield tunnel 5 construction on the railway. A plurality of inclined piles 4 are driven into the space between the original railway pile foundation 1 and the shield tunnel 5 to form an isolation wall, which can effectively block the influence of shield tunnel 5 construction on the railway. The construction method can complete the construction of the isolation wall without affecting the operation of the railway.

[0043] The construction sequence of the isolation structure and method for reducing the displacement of the railway pile foundation caused by shield construction provided by the present application is as follows: grouting and reinforcement, inclined pile construction, underpinning beam steel bar binding, formwork construction, underpinning beam pouring, and soil backfilling.

[0044] Before the construction of the inclined pile 4, the flatness of the construction site should be ensured, and the bearing capacity of the foundation should meet the requirements of the pile sinking machinery, transportation and construction. The pile position line, the soil entering line and the alignment line should be calculated according to the design inclination angle, the pile sinking depth and the equipment height. After the pile position is checked and no error is found, the construction can be carried out in sequence.

[0045] The inclined pile 4 is sunk by the static pressure method. Before the construction, the positioning axis should be determined according to the positioning control point, and the pile position line of the inclined pile 4 should be laid out. Protective measures should be taken at the pile position line. The construction section should be divided and the pile sinking sequence should be arranged according to the design and the actual situation on site. The inclination angle of the pile should be measured and the quality of the pile body should be checked. After the check is passed, the construction can be carried out. During the pile sinking process, whether the inclination angle of the pile body meets the design requirements should be checked.

[0046] The inclined pile 4 is pressed into the grouting reinforcement body 6 by the pile presser. The upper part of the inclined pile 4 is connected with the underpinning beam 3 to form a whole body for isolation, which is subjected to force together, to isolate the influence of the shield tunnel 5 construction on the railway pile foundation.

[0047] The inclined pile is a prefabricated pile with a size of 500mm x 375mm and a hollow diameter of 210mm. The pile is pressed in advance according to the design point.

[0048] The inclined pile is constructed by the foundation pit without support prefabricated inclined pile middle inclined pile pile presser. The equipment can swing forward and backward within the range of ±30° inclination to adjust the pile pressing angle of the inclined pile 4. This construction method will not produce a large noise and vibration, and will not affect the railway. When the inclined pile structure is constructed, the pile presser must be laid on a thick steel plate or brick slag (30mm). The pile presser should be completely on the bearing steel plate to supplement the insufficient bearing capacity of the foundation and keep the pile presser stable. The hydraulic supports in front of and behind the pile presser should be supported on the bearing steel plate to prevent the pile presser from pitching forward and backward and to reduce the inclination rate during pile sinking. Before the pile position is laid, the pre-advance of the sample pile is calculated according to the distance from the top of the inclined pile to the ground and the direction of the inclined pile, and then the pile position is laid.

[0049] Before the pile sinking, the design angle of the pile should be measured and the quality of the pile head should be checked. After the check is passed, the construction can be carried out. During the pile sinking process, whether the inclination angle of the pile body meets the design requirements should be checked.

[0050] The pile should be fed by a special steel pile feeder. The engineering pile should not be used as a pile feeder. After the gantry is returned to the correct position, the pile should be fed. The pile should not be fed when the gantry is inclined.

[0051] The pile should be pressed to the correct position. The clamp holds the supporting pile tightly. The equipment is leveled. The verticality and inclination angle of the pile body are adjusted to meet the design requirements before being pressed in.

[0052] After the inclined pile 4 is completed by the pile pressing construction, the construction of the underpinning beam 3 is carried out. The length of the anchoring of the top of the inclined pile 4 into the underpinning beam 3 should meet the design requirements. After the earthwork is excavated to the bottom elevation of the underpinning beam 3, a cushion should be constructed at the bottom elevation of the underpinning beam 3, and the width of the cushion is preferably 100mm wider than the width of the underpinning beam 3 on each side. When the reinforcement of the underpinning beam 3 is installed, the stirrups on both sides of the pile body and the stirrups in the gap between the straight and inclined piles should meet the design requirements. The pile body part anchored into the underpinning beam 3 should be cleaned to ensure good adhesion between the pile body and the concrete of the underpinning beam 3. After the reinforcement of the underpinning beam 3 is bound, the formwork is constructed and the concrete is poured.

[0053] Before the earthwork is backfilled, the compaction machine should be selected according to the engineering characteristics, the nature of the soil, the design compaction coefficient, the construction conditions and other factors, and the construction parameters such as the water content control range of the backfill soil, the soil thickness and the compaction times should be determined.

[0054] The isolation structure is combined with the directional deep hole grouting reinforcement body 6 to enhance the overall stability of the structure. That is, a grouting reinforcement area is set in the soil around the tunnel to be constructed.

[0055] The deep hole grouting reinforcement area is set, and the directional deep hole grouting technology is used, that is, various organic or inorganic chemical slurry is injected into the soil by using air pressure or hydraulic pressure to solidify the foundation of the grouting reinforcement area, form the grouting reinforcement body 6, and improve the strength of the foundation soil, eliminate the collapsibility and prevent seepage and leakage. The gantry support structure formed by the inclined pile 4 and the underpinning beam 3 is combined with the grouting reinforcement body 6 to form an isolation structure between the railway pile foundation and the shield tunnel 5 to be constructed, which greatly reduces the deformation and settlement of the adjacent railway pile foundation and ensures the safe operation of the railway.

[0056] The grouting reinforcement body 6 is set to extend upward, downward, left and right respectively with the crown reference line of the shield tunnel 5 to be constructed as the baseline, and extend a certain distance upward and downward from the tunnel crown respectively.

[0057] The deep hole grouting reinforcement process of the present application has the following characteristics:

[0058] (1) Grouting range:

[0059] The grouting range is determined comprehensively according to the geological conditions, the size of the underground water pressure and the tunnel construction method and other factors. Generally speaking, the construction radius of the grouting reinforcement body 6 should be 2-3 times the radius of the tunnel excavation, and when the underground water pressure is too large or when the construction is carried out underwater, it should be 4-6 times the radius of the tunnel excavation.

[0060] (2) Grouting hole layout:

[0061] The grouting diffusion radius of a single grouting hole and the overall excavation parameters of the tunnel to be constructed are combined to arrange the grouting holes, and along the axis of the shield tunnel 5, several grouting holes are uniformly arranged until the grouting diffusion radius of each grouting hole can completely cover the range of the tunnel to be constructed; the diffusion radius of a single grouting hole can be determined according to a grouting test, and the parameters such as grouting pressure, injection capacity and grouting time can be understood through a field test; and the hole arrangement of the grouting hole is determined according to these parameters. When grouting, the grouting hole is drilled first, then the steel pipe is placed in the grouting hole, and finally the surrounding rock is grouted through the steel pipe.

[0062] (3) Grouting pressure:

[0063] The grouting pressure is the energy given to the slurry to penetrate, diffuse, split and compact in the soil layer, and the size determines the good and bad of the grouting effect and the cost. The grouting pressure can be 1-1.5 MPa on the basis of the hydrostatic pressure at the grouting position. The grouting pressure, slurry ratio, grouting speed and other construction technical parameters in actual construction should be determined according to the depth and geological conditions through a field test.

[0064] It should be noted that: in the construction process of the present application, the construction of grouting reinforcement needs to be completed first, then the pile pressing of the inclined pile 4 is carried out, and finally the construction of the underpinning beam 3 and the earthwork backfill is carried out.

[0065] The above-described embodiments are only used to illustrate the technical ideas and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and cannot be limited to the patent range of the present application only by the present embodiment, that is, any equivalent changes or modifications made according to the spirit disclosed by the present application still fall within the patent range of the present application.

Claims

1. An isolation structure for reducing railway pile foundation displacement caused by shield tunneling, characterized in that, The isolation structure includes a support beam and 2N rows of inclined piles, where N≥2. The support beam is located below the existing railway subgrade. Each row of inclined piles includes several inclined piles with the same inclination direction and angle. The 2N rows of inclined piles are divided into two groups. The bottom of one group of inclined piles is located on one side of the tunnel to be tunneled, and the bottom of the other group of inclined piles is located on the other side of the tunnel to be tunneled. Adjacent rows of inclined piles in the same group are arranged in an X-shape. The tops of the piles in both groups are connected to the support beam and form a gantry-type support structure. The tunnel to be tunneled passes through the gantry frame enclosed by the inclined piles and the support beam. Both groups of inclined piles are located between the original railway subgrade piles and the tunnel to be tunneled.

2. The isolation structure for reducing railway pile foundation displacement caused by shield tunneling construction according to claim 1, characterized in that, The inclination angle of the inclined pile is 20 to 30°.

3. The isolation structure for reducing railway pile foundation displacement caused by shield tunneling construction according to claim 1, characterized in that, The isolation structure also includes a grouting body surrounding the tunnel to be tunneled, with inclined piles extending into the grouting body.

4. The isolation structure for reducing railway pile foundation displacement caused by shield tunneling construction according to claim 1, characterized in that, The inclined piles located on both sides of the tunnel to be tunneled are symmetrically arranged with the axis of the tunnel as the center.

5. The isolation structure for reducing railway pile foundation displacement caused by shield tunneling construction according to claim 1, characterized in that, The inclined piles are hollow precast piles.

6. The isolation structure for reducing railway pile foundation displacement caused by shield tunneling construction according to claim 1, characterized in that, The top of the inclined pile extends into the supporting beam, and several steel bars are reserved at the top of the inclined pile to be connected to the steel bars of the supporting beam as a whole.

7. An isolation method for reducing railway pile foundation displacement caused by shield tunneling, characterized in that, The method includes the following steps: Step 1: Precast hollow inclined piles and reserve reinforcing bars at the top of the piles; Step 2: Grouting reinforcement is carried out on the tunnel to be tunneled under the railway subgrade and its surrounding area; Step 3: Divide the inclined piles into two groups and set them on both sides of the tunnel to be tunneled. Each group includes 2 to 4 rows, and each row includes 4 to 8 inclined piles. The static pressure method is used to drive the piles into the grouting reinforcement area at an angle using a pile driver. The adjacent rows of inclined piles in the same group are arranged in an X-shape. Step 4: After the earthwork is excavated to the designed bottom elevation of the replacement beam, a cushion layer is constructed at the bottom elevation of the replacement beam. The reserved steel bars at the top of the inclined pile are connected to the steel bars of the replacement beam as a whole and concrete is poured. Step 5: Backfilling.

8. The isolation method for reducing railway pile foundation displacement caused by shield tunneling construction according to claim 7, characterized in that, In step 2, the size of the grouting reinforcement zone is positively correlated with the groundwater pressure. The length, width, and height of the grouting reinforcement zone are 2 to 6 times the tunnel excavation diameter. Several grouting holes are evenly distributed in the grouting reinforcement zone so that the grouting diffusion radius of the grouting holes covers the area of ​​the tunnel to be tunneled. During grouting, grouting holes are drilled first, then steel pipes are placed in the grouting holes, and finally grout is injected into the surrounding rock through the steel pipes. The grouting pressure is 1 to 1.5 MPa higher than the hydrostatic pressure at the grouting point.

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