A vertical support structure and method for open top construction of a nuclear island basement

Abstract

The present application relates to nuclear power construction technical field, disclose a kind of vertical support structure and method for open top method construction nuclear island basement, including support pile, along the excavation sideline outside arrangement, support pile outside is provided with several water-stop mixing pile;Plane closed frame, be located at support pile top elevation and be connected with support pile, plane closed frame includes crown beam, crown beam is arranged along support pile center line and is connected with support pile, crown beam outside is connected with outer ring beam, and the bottom of outer ring beam is connected with several obliquely arranged uplift pile;Can give full play to the advantage that plane closed frame is resistant to lateral stiffness and uplift pile bearing capacity is high, the huge lateral water and soil pressure caused by excavation is transmitted to stable deep soil, the deformation degree of no inner support foundation pit is greatly reduced, the long-term stability of no inner support foundation pit is greatly improved, solve the problem that traditional pile anchor type support structure long-term deformation is larger, cannot meet the safety requirement of nuclear power engineering.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nuclear power construction, in particular to a vertical support structure and method for constructing a nuclear island basement by open top method. BACKGROUND

[0002] In order to greatly improve the equipment installation efficiency and shorten the installation time, the open top method is used to construct the nuclear island basement of the third generation nuclear power unit: that is, the walls of each layer are constructed first, and the floor slab can be poured and closed only after the equipment installation in the room is completed. When the open top method is used for construction, any horizontal internal support structure is not allowed to be arranged inside the foundation pit to prevent the conflict between the hoisted equipment and the internal support structure in space and affect the normal installation of the equipment, so that the foundation pit support scheme without internal support structure must be used: slope excavation or pile-anchor type support.

[0003] The slope excavation scheme has low technical difficulty and simple construction, and is the preferred scheme for the nuclear island foundation pit design at home and abroad, but it occupies a large area and has a huge amount of excavation and backfilling. Especially for the soft soil site with poor soil properties, in order to ensure the stability of the slope, the slope gradient will be greatly reduced, which will cause the amount of excavation and backfilling to increase sharply, resulting in a large increase in the engineering quantity and cost. Since the nuclear island and the surrounding auxiliary plant room are very close, the use of the slope excavation scheme will cause the auxiliary plant room to wait until the nuclear island foundation pit is completely backfilled before starting construction, thereby delaying the operation time of the auxiliary plant room and greatly increasing the total construction period.

[0004] The pile-anchor type support structure transmits the water and soil pressure borne by the row piles to the stable stratum through the anchor cable, and has the characteristics of small occupied area and small amount of excavation and backfilling. However, since the anchor cable is a flexible structure, its axial interface stiffness in the soft soil foundation is very small, and stress relaxation is prone to occur at the anchor cable-soil interface, so the horizontal lateral stiffness provided by the anchor cable is much smaller than that of the internal support structure, resulting in large long-term deformation of the support structure under the action of water and soil pressure, which often cannot meet the safety requirements of nuclear power engineering. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a vertical support structure and method for constructing a nuclear island basement by open top method, which not only overcomes the shortcomings of the slope excavation scheme, such as large occupied area, large amount of excavation and backfilling, and influence on the construction of surrounding auxiliary plant rooms, but also solves the problems of small horizontal lateral stiffness and large long-term deformation of the pile-anchor type support system.

[0006] In order to achieve the above-mentioned purpose, the present application is realized by the following technical scheme:

[0007] In the first aspect, a vertical support structure for constructing a nuclear island basement by open top method comprises:

[0008] Support piles are arranged along the outer side of the excavation line of the foundation pit, and a plurality of water-stopping mixing piles are arranged outside the support piles;

[0009] A planar closed frame is arranged at the top of the support piles and connected with the support piles, and the planar closed frame comprises a crown beam arranged along the center line of the support piles and connected with the support piles, and the crown beam is connected with an outer ring beam outside the crown beam, and the bottom of the outer ring beam is connected with a plurality of tilt arranged anti-pulling piles.

[0010] As a further implementation manner, the crown beam and the outer ring beam have the same shape as the shape surrounded by the support piles.

[0011] As a further implementation manner, the crown beam and the outer ring beam have the same height, and the crown beam is connected with the outer ring beam through web bars, and a reinforcing rib is arranged between adjacent web bars.

[0012] As a further implementation manner, a reinforcing plate is arranged between the corners of the crown beam and the outer ring beam, the reinforcing plate is arranged at the top of the web bar, and the reinforcing rib of the reinforcing plate is anchored into the crown beam, the web bar and the outer ring beam.

[0013] As a further implementation manner, the spacing between the crown beam and the outer ring beam is 1 / 10-1 / 5 of the length of the foundation pit.

[0014] As a further implementation manner, the water-stopping mixing piles are sequentially overlapped to form a vertical water-stopping curtain.

[0015] As a further implementation manner, the angle between the anti-pulling pile and the vertical direction is 20-30°.

[0016] As a further implementation manner, the support piles and the anti-pulling piles are both bored piles.

[0017] In a second aspect, a construction method for constructing a vertical support structure of a nuclear island basement by the top-opening method, comprising the following steps:

[0018] The water-stopping mixing piles are positioned and constructed outside the required construction support piles and are mutually overlapped and engaged;

[0019] The holes are formed in the vertical direction at the positions of the support piles and in the inclined direction at the positions of the anti-pulling piles, the steel cages are inserted after the holes are formed, and finally the concrete is poured;

[0020] The components of the planar closed frame are positioned and constructed outside the foundation pit;

[0021] The earthwork is excavated, the internal earthwork of the foundation pit is excavated along the inner side of the support piles, and the excavation is stopped until the designed base elevation is reached, thereby forming the support structure as described in any of the above.

[0022] The nuclear island basement is constructed.

[0023] As a further implementation mode, when the plane closed frame is constructed, the steel bars of each component are first bound, wherein the longitudinal main bars of the supporting piles and the uplift resisting piles should be anchored into the components at the corresponding positions of the plane closed frame; after the binding is completed, the concrete of each component of the plane closed frame is poured, and the one-time pouring forming process should be adopted; when the earthwork is excavated, the excavation should be performed according to the principles of stratification, block and symmetry, until the excavation reaches the design base elevation.

[0024] The beneficial effects of the present application are as follows:

[0025] 1. By arranging the plane closed frame outside the foundation pit, the plane closed frame is connected with the supporting piles at the bottom, the large lateral stiffness of the plane frame can be fully utilized, the huge water and soil pressure borne by the supporting piles is converted into the internal force of the closed frame, the lateral stiffness comparable to the internal support can be provided, and the horizontal deformation degree of the foundation pit without internal support is greatly reduced.

[0026] 2. The uplift resisting piles can utilize the characteristics of large oblique uplift resisting stiffness and high uplift resisting bearing capacity, a large part of the load borne by the supporting piles is transmitted to the stable deep soil, the long-term stability of the foundation pit without internal support is greatly improved, and the problem that the long-term deformation of the traditional pile anchor type supporting structure is large and cannot meet the safety requirements of the nuclear power engineering is solved.

[0027] 3. The plane closed frame and the uplift resisting piles are arranged outside the foundation pit, and no supporting component is arranged inside the foundation pit, the strict requirement for the internal clearance when the open top method is used for the construction of the nuclear island basement structure can be met, a good working space is provided for the structural construction and equipment installation, the construction period of the procedures such as support replacement and support reversal is greatly saved, and the construction and installation speed of the nuclear island underground structure is greatly accelerated.

[0028] 4. The slope of the foundation pit after excavation is a vertical slope, compared with the conventional large batter excavation scheme in the current nuclear power foundation pit, the occupied area, excavation and backfill volume are greatly reduced, the construction period is shortened, the cost is greatly saved, and the influence of the backfill of the nuclear island foundation pit on the delivery and operation of the surrounding auxiliary plant is greatly alleviated. BRIEF DESCRIPTION OF DRAWINGS

[0029] The drawings accompanying the specification of the present application form a part thereof, serve to provide further understanding of the present application, and together with the description of the exemplary embodiments of the present application and the explanation thereof, explain the present application, and do not constitute an improper limitation of the present application.

[0030] Figure 1 is a plan view of the supporting structure in the embodiment of the present application;

[0031] Figure 2 is Figure 1 the A-A sectional view in

[0032] Figure 3 is Figure 1Fig. 2 is a sectional view of B-B in Fig. 1;

[0033] Figure 4 Fig. 3 is an enlarged view of the structure at C in Fig. 1; Figure 1 Fig. 4 is an enlarged view of the structure at D in Fig. 1.

[0034] Figure 5 Fig. 5 is an enlarged view of the structure at E in Fig. 1. Figure 1 Fig. 6 is an enlarged view of the structure at F in Fig. 1.

[0035] In the drawings, the mutual distances or dimensions are exaggerated for showing the positions of the parts, and the schematic views are only for illustration.

[0036] In the drawings, 1 is a nuclear island basement, 2 is a plane closed frame, 21 is a crown beam, 22 is a web beam, 23 is an outer ring beam, and 24 is a reinforcing plate, 3 is a support pile, 4 is a waterproof mixing pile, and 5 is an anti-pulling pile. DETAILED DESCRIPTION

[0037] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0038] Example 1

[0039] In a typical embodiment of the present application, referring to Fig. 1, a vertical support structure for building a nuclear island basement by the top-opening method includes support piles 3, waterproof mixing piles 4, anti-pulling piles 5, and a plane closed frame 2, and the vertical support structure is suitable for a nuclear island foundation pit with a depth of not more than 20 m. Figures 1-5 As shown in Fig. 2, the support piles 3 are arranged along the outside of the foundation pit excavation line, forming a rectangle, and a plurality of waterproof mixing piles 4 are arranged outside the support piles 3, abutting the support piles 3 and overlapping each other to form a continuous vertical waterproof curtain, and the waterproof mixing piles 4 are used for waterproofing when the underground water level is higher than the foundation level. The support piles 3 are arranged to bear the huge lateral pressure generated by the soil outside the foundation pit after excavation.

[0040] Figure 1 As shown in Fig. 3, a plane closed frame 2 is arranged on the horizontal plane outside the foundation pit, including a crown beam 21, a web beam 22, an outer ring beam 23, and a reinforcing plate 24 at the corners.

[0041] In order to increase the constraint of the top of the support pile 3 and ensure that the horizontal force of the top of the support pile 3 can be well transmitted to the outside of the foundation pit, the plane closed frame 2 is arranged at the top of the support pile 3 and connected with the support pile, the crown beam 21 and the outer ring beam 23 have the same shape as the shape enclosed by the support piles 3, both are rectangles, and the size of the crown beam 21 is smaller than the size of the outer ring beam 23.

[0042] In order to increase the constraint of the top of the support pile 3 and ensure that the horizontal force of the top of the support pile 3 can be well transmitted to the outside of the foundation pit, the plane closed frame 2 is arranged at the top of the support pile 3 and connected with the support pile, the crown beam 21 and the outer ring beam 23 have the same shape as the shape enclosed by the support piles 3, both are rectangles, and the size of the crown beam 21 is smaller than the size of the outer ring beam 23. ​

[0043] The crown beam 21 is arranged along the center line of the support pile 3 and connected with the support pile 3. The outer side of the crown beam 21 is connected with the outer ring beam 23. The crown beam 21 and the outer ring beam 23 have the same height. The center line of the outer ring beam 23 is parallel to the center line of the crown beam 21. The distance between the crown beam 21 and the outer ring beam 23 is determined by the required rigidity of the plane closed frame 2 and is generally 1 / 10-1 / 5 of the length of the pit side.

[0044] The crown beam 21 is connected with the outer ring beam 23 through a plurality of web members 22. A reinforcing rib is arranged between adjacent web members 22. One end of the web member is connected with the crown beam 21 and the other end is connected with the outer ring beam 23. The bottom of the outer ring beam 23 is connected with a plurality of inclined uplift piles 5. The uplift piles 5 have an angle of 20-30° with the vertical direction. The uplift piles 5 are used to transmit the huge horizontal force transmitted by the plane closed frame 2 to the deep stable stratum.

[0045] A reinforcing plate 24 is arranged between the crown beam and the outer ring beam at the corner of the plane closed frame 2. The reinforcing plate 24 is arranged at the top of the web member 22. When the reinforcing plate 24 is arranged, the reinforcing rib of the reinforcing plate 24 is anchored into the crown beam 21, the web member 22 and the outer ring beam 23 to improve the rigidity of the corner of the plane closed frame 2 and reduce the stress concentration of the corner.

[0046] The support pile 3 and the inclined uplift pile 5 are both cast-in-situ piles with circular cross sections. The diameter of the support pile 3 is 1000-1500 mm. The diameter of the inclined uplift pile 5 is 800-1000 mm. The crown beam 21, the web member 22 and the outer ring beam 23 are all made of reinforced concrete and have rectangular cross sections. The thickness of the corner horizontal reinforcing plate 24 is 150-200 mm. The thickness of the corner horizontal reinforcing plate 24 is determined by the required rigidity and strength of the corner.

[0047] The support structure of the embodiment has no any supporting member inside the pit and can meet the strict requirement for the internal clearance when the open-top method is used to construct the nuclear island basement structure of the third generation nuclear power unit. The support structure provides a good working space for the structural construction and equipment installation and greatly saves the construction period of the procedures such as replacing the support and inverting the support and greatly accelerates the construction and installation speed.

[0048] The support structure of the embodiment can fully utilize the advantages of the large lateral rigidity of the horizontal closed frame and the high bearing capacity of the uplift pile, transmit the huge lateral water and soil pressure caused by excavation to the stable deep soil body, greatly reduce the deformation degree of the pit without internal support and greatly improve the long-term stability of the pit without internal support and solve the problem that the long-term deformation of the traditional pile-anchor type support structure is large and cannot meet the safety requirement of the nuclear power project.

[0049] Embodiment two

[0050] A construction method of a vertical support structure for constructing a nuclear island basement by using the open-top method, comprising the following steps:

[0051] S1, vertical water stop curtain construction: according to the design drawing, the water stop mixing pile 4 is positioned and constructed on the outside of the supporting pile 3 to form a continuous vertical water stop curtain on the outside of the nuclear island foundation pit. Figures 1-3

[0052] S2, supporting pile 3 and inclined uplift pile 5 construction: according to the design drawing, holes are formed at the designed pile positions, wherein the holes are formed vertically at the supporting pile positions and are formed obliquely at the inclined uplift pile positions; after the holes are formed, the steel reinforcement cage is inserted, and finally the concrete is poured;

[0053] S3, plane closed frame 2 construction: after the concrete of the supporting pile 3 and the uplift pile 5 forms strength, the over-poured concrete at the pile head is broken to expose the longitudinal main reinforcement; then the components of the plane closed frame 2, including the crown beam 21, the web 22, the outer ring beam 23 and the corner horizontal reinforcement plate 24, are positioned and constructed on the outside of the foundation pit. During construction, the steel reinforcement of each component is bound, wherein the longitudinal main reinforcement of the supporting pile 3 and the inclined uplift pile 5 should be anchored into the corresponding components of the plane closed frame 2; after the binding is completed, the concrete of each component of the plane closed frame 2 is poured, and one-time pouring forming process should be used to ensure good integrity;

[0054] S4, earthwork excavation: after the concrete strength of each component of the plane closed frame 2 reaches the design requirement, the internal earthwork of the foundation pit is excavated along the inside of the supporting pile 3, and the excavation should be carried out according to the principles of stratification, block and symmetry until the excavation reaches the design base elevation.

[0055] S5, nuclear island basement 1 construction: after excavation to the base, the nuclear island basement 1 is constructed from bottom to top, and after all the equipment in the basement is installed, the foundation pit trench should be backfilled in time until the nuclear island basement 1 is partially completed.

[0056] By setting a closed horizontal support structure on the outside of the foundation pit, the characteristics of large in-plane lateral stiffness of the frame structure are used to solve the problem that the internal support type support structure cannot meet the internal clearance requirement of the nuclear island open-top construction, to solve the problems of large occupied area, large excavation and backfill volume, long construction period and influence on the construction of surrounding auxiliary plant of the benching excavation scheme, and to solve the problem that the traditional pile-anchor type support system has small horizontal lateral stiffness and large long-term horizontal deformation, which cannot meet the safety requirements of nuclear power engineering.

[0057] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.​

Claims

1. A vertical support structure for constructing a nuclear island basement using the open-top method, characterized in that, include: Support piles are arranged along the outer side of the excavation edge of the foundation pit. Holes are drilled vertically at the support pile locations, and several water-stopping and mixing piles are installed on the outer side of the support piles. A planar closed frame is set at the top elevation of the support piles and connected to the support piles. The planar closed frame includes a capping beam, which is arranged along the center line of the support piles and connected to the support piles. An outer ring beam is connected to the outside of the capping beam, and several inclined tension piles are connected to the bottom of the outer ring beam. The shape of the cap beam and the outer ring beam is the same as the shape formed by the support piles, and the size of the cap beam is smaller than that of the outer ring beam; the cap beam is connected to the outer ring beam through the web members; a reinforcing plate is provided between the corners of the cap beam and the outer ring beam, the reinforcing plate is located at the top of the web members, and the steel bars of the reinforcing plate are anchored into the cap beam, the web members, and the outer ring beam; The distance between the cap beam and the outer ring beam is 1 / 10 to 1 / 5 of the length of the foundation pit.

2. A vertical support structure for constructing a nuclear island basement using the open-top method according to claim 1, characterized in that, The crown beam and the outer ring beam are at the same height, and reinforcing ribs are provided between adjacent web members.

3. A vertical support structure for constructing a nuclear island basement using the open-top method according to claim 1, characterized in that, The water-stopping mixing piles are stacked in sequence to form a vertical water-stopping curtain.

4. A vertical support structure for constructing a nuclear island basement using the open-top method according to claim 1, characterized in that, The angle between the tension pile and the vertical direction is 20-30°.

5. A vertical support structure for constructing a nuclear island basement using the open-top method according to claim 1, characterized in that, The support piles and tension piles are all bored cast-in-place piles.

6. A construction method for a vertical support structure used in the open-top construction of a nuclear island basement, characterized in that, Includes the following steps: Lay out and position the interlocking water-stop mixing piles on the outside of the required support piles. Drill holes vertically at the support pile locations and diagonally at the pull-out pile locations. After drilling, insert the reinforcing cage and finally pour concrete. Lay out the construction plan and enclose the frame components on the outside of the foundation pit; Earthwork excavation: Excavate the soil inside the foundation pit along the inner side of the support piles until the design foundation elevation is reached, forming the support structure as described in any one of claims 1-5. Construction of the nuclear island basement.

7. A construction method for a vertical support structure for an open-top nuclear island basement as described in claim 6, characterized in that, During the construction of the planar closed frame, the steel bars of each component are tied first. The longitudinal main bars of the support piles and tension piles should be anchored into the components at the corresponding positions of the planar closed frame. After the binding is completed, concrete should be poured for each component of the planar closed frame, and a one-time casting process should be adopted; when excavating the earthwork, the excavation should be carried out in accordance with the principles of layering, segmenting and symmetry, until the design foundation elevation is reached.

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