Micro-deformation control method for foundation pit of overpass subway

Abstract

The invention discloses a micro-deformation control method for a foundation pit of an overpass subway, which comprises the following steps of: driving a plurality of rows of fender posts in a to-be-constructed position of the foundation pit, and dividing the foundation pit into a plurality of foundation pit units, wherein the two first units are located at the tops of two shield intervals, the second unit is located between the two shield intervals, and the two third units are located on the outer sides of the two shield intervals; soil body reinforcement is conducted within the range of the two first units and within a certain broadened range outside the two first units; anti-uplift piles are driven into the second unit and the two third units; the two third units and the second unit are excavated, the portions, above the designed elevation, of the bottom of the corresponding foundation pit unit and the soil body are all excavated away during excavation, then a bottom plate is constructed at the bottom of the corresponding foundation pit unit, and the bottom plate and the remaining anti-uplift piles at the bottom are connected to form a portal frame for reinforcement; and the two first units are excavated. By means of the method, the construction efficiency and the soil body stability are improved.

Description

Technical Field

[0001] The invention relates to the technical field of building construction, and in particular to a method for controlling micro-deformation of a foundation pit that crosses a subway. Background Art

[0002] With the acceleration of urbanization, the pressure on the public transportation system is increasing. New underground passages often need to be constructed above existing subway lines, which creates a technical demand for foundation pit engineering across the existing shield section. The construction difficulties include: the excavation of the foundation pit of the underground passage will cause the shield section to rise; the foundation pit engineering across the existing shield section needs to be carried out without affecting the normal operation of the existing line, and the construction technology requirements are high. The construction of the foundation pit and the support structure must be precisely controlled, and deformation control is very important to avoid any damage to the existing subway line below. The traditional construction method ensures the stability of the subsequent soil excavation through pit excavation and soil reinforcement, but the control of the shield section rise is small, and it is also necessary to set ballast at the top of the shield section to reduce the shield section rise. In addition, the traditional construction method does not control the construction time in place, and it cannot be completed within 6 hours of the subway suspension. If it cannot be completed, it is necessary to backfill the foundation pit before the subway work, which affects the construction efficiency. Summary of the invention

[0003] The purpose of the present invention is to overcome the defects of the prior art and provide a method for controlling micro-deformation of a foundation pit above a subway. By setting anti-uplift piles, when the foundation pit is excavated directly above the section, a portal frame is formed by connecting with the bottom plate to reinforce the shield section to resist the uplift caused by the foundation pit excavation, thereby ensuring the structural stability.

[0004] To achieve the above object, the present invention provides a method for controlling micro-deformation of a foundation pit over a subway, comprising the steps of:

[0005] Step 1: driving multiple rows of retaining piles into the position to be constructed in the foundation pit, dividing the foundation pit into multiple foundation pit units, including two first units located at the top of two shield sections, a second unit located between the two shield sections, and two third units located outside the two shield sections;

[0006] Step 2: Perform soil reinforcement within the two first unit ranges and within a certain range outside the two first unit ranges;

[0007] Step 3: driving anti-uplift piles into the second unit and the two third units, so that the anti-uplift piles penetrate below the design elevation of the bottom of the corresponding foundation pit unit;

[0008] Step 4: excavate the two third units and the second unit, and during the excavation, remove all the anti-uplift piles and soil above the design elevation at the bottom of the corresponding foundation pit unit, and then construct a bottom plate at the bottom of the corresponding foundation pit unit, so that the bottom plate is connected to the remaining anti-uplift piles at the bottom to form a portal frame reinforcement;

[0009] Step 5: Excavate the two first units until the designed position and construct the internal structure.

[0010] A further improvement of the method for controlling micro-deformation of a foundation pit over a subway in the present invention is that, when executing the above step 2, the widened range is 3 m on both sides of the two first units.

[0011] A further improvement of the method for controlling micro-deformation of a foundation pit across a subway of the present invention is that, when executing the above step 2, when soil reinforcement is performed within the two first units, the reinforcement depth is made 0.8m away from the top of the shield segment, and when soil reinforcement is performed outside the two first units, the reinforcement depth is made to exceed the bottom of the shield segment and be at least one times the shield diameter away from the bottom of the shield segment.

[0012] A further improvement of the method for controlling micro-deformation of a foundation pit over a subway in the present invention is that, when executing the above step 4, the two third units are constructed first and then the second unit is constructed.

[0013] A further improvement of the method for controlling micro-deformation of a foundation pit over a subway in the present invention is that, when executing the above step 4, before constructing the base plate, the base plate reinforcement cage is prefabricated on the ground, and when constructing the base plate, the prefabricated base plate reinforcement cage is directly hoisted into the pit and directly poured.

[0014] A further improvement of the method for controlling micro-deformation of a foundation pit across a subway of the present invention is that, when executing the above step 1, two rows of retaining piles are respectively driven into the two first units along a length direction perpendicular to the subway to divide the first unit into three small foundation pits; and when executing the above step 5, the small foundation pit in the middle is excavated first and then the small foundation pits on both sides are excavated.

[0015] A further improvement of the method for controlling micro-deformation of a foundation pit over a subway in the present invention is that, when executing the above steps 4 and 5, a layered excavation method is used to excavate the corresponding foundation pit units.

[0016] Compared with the prior art, the advantages of the present invention are:

[0017] By setting up anti-uplift piles, when the foundation pit is excavated directly above the shield section, a portal frame reinforcement is formed by connecting with the bottom plate to resist the floating of the shield caused by the foundation pit excavation, thereby ensuring the stability of the structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 The diagram of the pit division of the method for controlling micro-deformation of a foundation pit over a subway according to the present invention.

[0020] Figure 2 It is a schematic diagram of the soil reinforcement range of the micro-deformation control method of the foundation pit over the subway of the present invention.

[0021] Figure 3 It is a schematic diagram of the soil reinforcement depth of the foundation pit micro-deformation control method over a subway according to the present invention.

[0022] Figure 4 It is a schematic diagram of the distribution of anti-uplift piles of the micro-deformation control method of the foundation pit over the subway of the present invention.

[0023] Figure 5 It is a schematic diagram of foundation pit excavation of the foundation pit micro-deformation control method for a subway station according to the present invention.

[0024] In the figure: 1. Shield section; 2. Retaining piles; 3. First unit; 4. Second unit; 5. Third unit; 6. Anti-uplift piles; 7. Shield segments; 8. Bottom plate. DETAILED DESCRIPTION

[0025] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0026] The micro-deformation control method for a foundation pit over a subway station of the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] See also Figure 1 to Figure 5 As shown, the method for controlling micro-deformation of a foundation pit over a subway station comprises the following steps:

[0028] Step 1: driving multiple rows of retaining piles 2 into the position to be constructed in the foundation pit, and dividing the foundation pit into multiple foundation pit units, including two first units 3 located at the top of two shield sections 1, a second unit 4 located between the two shield sections 1, and two third units 5 located outside the two shield sections 1;

[0029] Step 2: Reinforce the soil within the two first units 3 and a certain range outside the two first units 3;

[0030] Step 3: driving anti-uplift piles 6 into the second unit 4 and the two third units 5, so that the anti-uplift piles 6 penetrate below the design elevation of the bottom of the corresponding foundation pit unit;

[0031] Step 4: excavate the two third units 5 and the second unit 4, and during the excavation, remove all the anti-uplift piles 6 and soil above the design elevation at the bottom of the corresponding foundation pit unit, and then construct a bottom plate 8 at the bottom of the corresponding foundation pit unit, so that the bottom plate 8 is connected with the remaining anti-uplift piles 6 at the bottom to form a portal frame reinforcement;

[0032] Step 5: Excavate the two first units 3 until the designed position and construct the internal structure.

[0033] By providing the anti-uplift piles 6, when the foundation pit is excavated directly above the shield section 1, the anti-uplift piles 6 are connected with the bottom plate 8 to form a portal frame reinforcement, thereby resisting the uplift of the shield section 1 caused by the foundation pit excavation and ensuring the structural stability.

[0034] Specifically, the retaining piles 2 are SMW piles, with steel sections inserted at intervals.

[0035] Specifically, the soil reinforcement is tri-axial mixing pile reinforcement.

[0036] Preferably, when executing the above step 2, the widening range is 3 m on both sides of the two first units 3 .

[0037] Specifically, as shown in the attached manual Figure 2 As shown: the oblique shaded portion in the figure is the soil reinforcement range located within the first unit 3, and the blue portion in the figure is the soil reinforcement range located outside the first unit 3, including the entire second unit 4 and the two third units 5 relatively close to the two first units 3.

[0038] Preferably, when executing the above step 2, when the soil is reinforced inside the two first units 3, the reinforcement depth is 0.8m from the top of the shield segment 7, and when the soil is reinforced outside the two first units 3, the reinforcement depth is more than below the bottom of the shield segment 7 and at least one times the shield diameter away from the bottom of the shield segment 7.

[0039] Specifically, as shown in the attached manual Figure 3 As shown: By reinforcing the soil on both sides and the top of shield section 1, the soil stability is ensured and soil disturbance during subsequent soil excavation is avoided.

[0040] Preferably, when executing the above step 4, the two third units 5 are constructed first and then the second unit 4 is constructed.

[0041] By excavating the two third units 5 first and then the second unit 4, the stability of the soil is ensured.

[0042] Preferably, when executing the above step 4, before constructing the base plate 8, the base plate reinforcement cage is prefabricated on the ground, and when constructing the base plate 8, the prefabricated base plate reinforcement cage is directly hoisted into the pit and directly poured.

[0043] In order to save construction time, prefabricated bottom plate steel cage is used, which does not take up construction time and improves construction efficiency.

[0044] Preferably, when executing the above step 1, two rows of retaining piles 2 are respectively driven into the two first units 3 along a direction perpendicular to the length of the subway to divide the first unit 3 into three small foundation pits. When executing the above step 5, the small foundation pit in the middle is excavated first and then the small foundation pits on both sides.

[0045] Specifically, as shown in the attached manual Figure 1 As shown: the second units 4 are 3-1 to 3-6, and the two third units 5 are 1-1 to 1-6 and 2-1 to 2-6 respectively.

[0046] Specifically, when excavating the second unit 4 and the two third units 5, the excavation is also carried out in sections, first excavating the middle and then excavating the two sides.

[0047] Specifically, as shown in the attached manual Figure 1 As shown: the small foundation pit includes 4-1, 4-2, 5-1, 5-2, 6-1, 6-2, 7-1, 7-2, 8-1, 8-2, 9-1, and 9-2.

[0048] By further dividing the first unit 3 into three small foundation pits, the soil stability during the excavation of the first unit 3 is ensured, and the uplift of the shield section 1 is avoided.

[0049] Preferably, when executing the above steps 4 and 5, a layered excavation method is adopted to excavate the corresponding foundation pit units.

[0050] Specifically, as shown in the attached manual Figure 5 As shown: The green part is a schematic diagram of the two excavations. Due to the tight construction schedule, the excavation of the first unit 3 and the construction of the internal structure need to be completed within 6 hours of the subway suspension. The specific time control is as follows:

[0051] The first excavation shall be carried out within one hour before the subway stops operating, and the first excavation shall be carried out to the first design height, which shall not affect the normal operation of the subway;

[0052] The second excavation is carried out within 1.5 hours after the subway stops running, until the bottom of the pit is reached;

[0053] In the next 2.5 hours, the pile heads of the three-axis mixing piles for soil reinforcement were processed, the debris at the bottom of the pit was cleaned, and the prefabricated bottom plate reinforcement cage was hoisted;

[0054] During the last two hours, the bottom slab 8 is poured.

[0055] Specifically, it also includes an emergency plan: prepare bagged iron sand on site. If the uplift of shield section 1 exceeds the control value, use bagged iron sand for ballasting; if leakage is found at the bottom or side wall of the pit during soil excavation, grouting should be used to seal and backfill the foundation pit.

[0056] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change of the proportion relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. The change or adjustment of their relative relationship should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

[0057] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for controlling micro-deformation of a foundation pit over a subway, characterized in that: Includes steps: Step 1: driving multiple rows of retaining piles into the position to be constructed in the foundation pit, dividing the foundation pit into multiple foundation pit units, including two first units located at the top of two shield sections, a second unit located between the two shield sections, and two third units located outside the two shield sections; Step 2: Perform soil reinforcement within the two first unit ranges and within a certain range outside the two first unit ranges; Step 3: driving anti-uplift piles into the second unit and the two third units, so that the anti-uplift piles penetrate below the design elevation of the bottom of the corresponding foundation pit unit; Step 4: excavate the two third units and the second unit, and during the excavation, remove all the anti-uplift piles and soil above the design elevation at the bottom of the corresponding foundation pit unit, and then construct a bottom plate at the bottom of the corresponding foundation pit unit, so that the bottom plate is connected to the remaining anti-uplift piles at the bottom to form a portal frame reinforcement; Step 5: Excavate the two first units until the designed position and construct the internal structure.

2. The method for controlling micro-deformation of a foundation pit over a subway as claimed in claim 1, characterized in that: When executing the above step 2, the widened range is 3 m on both sides of the two first units.

3. The method for controlling micro-deformation of a foundation pit over a subway as claimed in claim 1, characterized in that: When executing the above step 2, when the soil is reinforced within the two first units, the reinforcement depth is 0.8m from the top of the shield segment; when the soil is reinforced outside the two first units, the reinforcement depth is more than the bottom of the shield segment and at least one times the shield diameter away from the bottom of the shield segment.

4. The method for controlling micro-deformation of a foundation pit over a subway as claimed in claim 1, characterized in that: When executing the above step 4, the two third units are constructed first and then the second unit is constructed.

5. The method for controlling micro-deformation of a foundation pit over a subway as claimed in claim 1, characterized in that: When executing the above step 4, before constructing the base plate, the base plate reinforcement cage is prefabricated on the ground. When constructing the base plate, the prefabricated base plate reinforcement cage is directly hoisted into the pit and directly poured.

6. The method for controlling micro-deformation of a foundation pit over a subway as claimed in claim 1, characterized in that: When executing the above step 1, two rows of retaining piles are driven into the two first units respectively along the length direction perpendicular to the subway to divide the first unit into three small foundation pits. When executing the above step 5, the small foundation pit in the middle is excavated first and then the small foundation pits on both sides.

7. The method for controlling micro-deformation of a foundation pit over a subway as claimed in claim 1, characterized in that: When executing the above steps 4 and 5, the corresponding foundation pit units are excavated using the layered excavation method.

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