CN112982432A - Prestressed concrete foundation pit supporting structure and construction method - Google Patents
Prestressed concrete foundation pit supporting structure and construction method Download PDFInfo
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- CN112982432A CN112982432A CN202110185034.2A CN202110185034A CN112982432A CN 112982432 A CN112982432 A CN 112982432A CN 202110185034 A CN202110185034 A CN 202110185034A CN 112982432 A CN112982432 A CN 112982432A
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D17/00—Excavations; Bordering of excavations; Making embankments
- E02D17/02—Foundation pits
- E02D17/04—Bordering surfacing or stiffening the sides of foundation pits
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Abstract
The invention relates to a prestressed concrete foundation pit supporting structure and a construction method, wherein the prestressed concrete foundation pit supporting structure comprises the following components: retaining structure device, it sets up around the foundation ditch, retaining structure device's first end is fixed in the foundation ditch bottom, retaining structure device's second end forms retaining structure at the foundation ditch top, for example: supporting piles or underground continuous walls; and one or more prestressed concrete beams traversing at least part of the retaining structure means in a horizontal direction and configured to create a tendency of deformation towards the outside of the foundation pit. The foundation pit supporting structure of this application can set up one or more prestressing force crossbeam on the foundation ditch horizontal direction to can reduce supporting structure's structure internal force, reduce structural deformation, improve retaining structure's the curved and shear bearing capacity that receives, can adapt to the support demand of deeper foundation pit.
Description
Technical Field
The invention relates to the field of geotechnical engineering, in particular to a prestressed concrete foundation pit supporting structure and a construction method.
Background
The foundation pit is a space excavated at the design position of the foundation according to the elevation of the foundation and the size of the plane of the foundation. Before excavation, an excavation scheme is determined according to geological and hydrological data and the conditions of buildings nearby the site, and waterproof drainage work is performed. The soil slope is stabilized by digging deep and using a method of slope placing or soil nailing walls, and the gradient size is determined according to relevant construction engineering regulations. When the excavation exceeds a certain depth, extra measures are needed for supporting. In the prior art, in order to reduce the structural internal force and structural deformation of the slope protection pile, a measure of additionally arranging an anchor rod or an inner support is adopted. An anchor-pulling supporting system or an inner supporting system is formed, and the anchor-pulling supporting system or the inner supporting system is also the most common supporting form in the current foundation pit engineering. However, in practical engineering projects, the application of the anchor rod and the inner support is often limited in various ways. For example, limited by land resources and red lines of construction land, the required range of the anchor rod is large and is bound to exceed the red lines, so that the problem of encroaching on the use right of adjacent land is caused, the adverse effect on subsequent development of adjacent underground space is caused, and some domestic cities have been continuously issued with government administrative laws and regulations that do not allow the supporting structure to exceed the red lines of buildings. In addition, if there is a building or a multi-story basement around the perimeter, the anchor cannot be implemented. Although the inner support supporting system does not occupy the use right of adjacent land, the inner support arranged in the foundation pit seriously influences the normal construction of a main structure, the comprehensive cost is generally high, and developers and contractors cannot accept the form of the inner support supporting structure in many areas (such as Beijing). Accordingly, there is a pressing need in the art for a new excavation supporting structure.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention provides a prestressed concrete foundation pit supporting structure, which comprises: the retaining structure device is arranged around the foundation pit, a first end of the retaining structure device is fixed at the bottom of the foundation pit, and a second end of the retaining structure device is arranged at the top of the foundation pit to form a retaining structure; and one or more prestressed concrete beams traversing at least a portion of the soil retaining structure means in a horizontal direction and configured to create a tendency to deform towards the exterior of the excavation.
The prestressed concrete foundation pit supporting construction as set forth above, wherein said soil retaining structure means comprises a plurality of slope protecting piles.
The prestressed concrete foundation pit supporting construction as set forth above, wherein said soil retaining structure means comprises an underground diaphragm wall.
The prestressed concrete foundation pit supporting structure as described above, wherein the cross-beams form a closed structure or an open structure to restrain the soil guard structure means.
The prestressed concrete foundation pit supporting structure as described above, wherein the number of the beams is plural, and the heights of the plural beams are different to restrain the soil retaining structure means at different positions.
The prestressed concrete foundation pit supporting construction as set forth above, wherein the cross-beam comprises a crown beam provided at or near the second end of the soil retaining structure means.
The prestressed concrete foundation pit supporting structure as set forth above, wherein the cross-beam includes a first wale disposed between the first end and the second end of the soil guard structure means.
The prestressed concrete foundation pit supporting structure as described above, wherein the cross beam includes a plurality of first wales, adjacent first wales are fixedly connected to each other by a connecting device, and an operating space is reserved outside the connecting device in the foundation pit.
The prestressed concrete foundation pit supporting construction as set forth above, wherein the cross-beam includes a second wale disposed between the first end and the second end of the soil guard structure means.
The prestressed concrete foundation pit supporting structure comprises a beam, wherein the beam comprises one or more steel strands, the steel strands are eccentrically arranged at the inner side of the foundation pit relative to the central axis of the beam and are configured to provide prestress for the beam.
The prestressed concrete foundation pit supporting structure as described above, wherein the two ends of the steel strand are disposed on the upper surfaces of the two ends of the beam or the two end surfaces of the beam.
The prestressed concrete foundation pit supporting structure comprises a steel strand, wherein the steel strand is an unbonded steel strand or a bonded steel strand.
The prestressed concrete foundation pit supporting structure as described above, wherein the cross-section of the beam is the same cross-section or a variable cross-section.
The prestressed concrete foundation pit supporting structure as described above, wherein the cross-section of both ends of the cross-beam may be smaller than the cross-sectional area of the middle of the cross-beam.
The prestressed concrete foundation pit supporting structure as described above, further comprising: one or more anchor rods disposed at one or both ends of the cross beam; or one or more rows of anchors disposed on the beam configured to restrain the beam.
The prestressed concrete foundation pit supporting structure as described above, wherein the anchor rods are provided on the retaining structure device.
The prestressed concrete foundation pit supporting structure comprises one or more steel strands in the slope protection pile, wherein the steel strands are eccentrically arranged outside the foundation pit relative to the central axis of the slope protection pile and are configured to provide prestress for the slope protection pile.
According to another aspect of the present application, there is provided a method of constructing a prestressed concrete foundation pit supporting structure, including: constructing and arranging soil retaining structure devices around a foundation pit to be excavated; and at a predetermined depth, construction setting one or more beams traversing at least part of the soil retaining structure means in a horizontal direction and configured to create a tendency of deformation towards the outside of the foundation pit; and excavating the foundation pit to a preset foundation pit depth.
The construction method as described above, further comprising: one or more interconnected prestressed crown beams are constructed at or near the top end of the earth-retaining structure assembly.
The construction method as described above, further comprising: and excavating the foundation pit, and constructing and arranging one or more prestressed first waist beams at a first depth of the soil retaining structure device.
The construction method as described above, further comprising: and excavating the foundation pit, and constructing and arranging one or more second waist beams applying prestress at a second depth of the soil retaining structure device.
The construction method as described above, further comprising: the plurality of beams are interconnected to form a closed or an open structure to constrain the earth-retaining structure means.
The construction method as described above, further comprising: one or more anchor rods are provided outside the cross beam, connected to one or both ends of the cross beam, or one or more rows of anchor rods connected to the cross beam, configured to restrain the cross beam.
The utility model provides a foundation pit supporting construction, it can be in horizontal direction horizontal partial cantilever supporting construction, changes cantilever supporting construction's cantilever state into there is the confined state to can reduce cantilever supporting construction's structure internal force, reduce the structural deformation, can adapt to the needs of strutting of deeper foundation pit.
Drawings
Preferred embodiments of the present invention will now be described in further detail with reference to the accompanying drawings, in which:
fig. 1 is a schematic view of a foundation pit supporting structure according to an embodiment of the present application;
FIG. 2 is a top view of an excavation supporting system according to one embodiment of the present application;
FIG. 3 is a schematic view of a portion of an excavation supporting structure according to one embodiment of the present application;
FIG. 4 is a schematic view of a portion of an excavation supporting structure according to one embodiment of the present application;
FIG. 5 is a schematic view of a retaining structure for a foundation pit according to another embodiment of the present application;
fig. 6A and 6B are schematic views of stress calculations for a foundation pit supporting structure according to an embodiment of the present application;
figures 7A and 7B are structural variations of different excavation supporting structures according to one embodiment of the present application;
FIG. 8 is a flow chart of a construction process for a retaining and protecting structure of a foundation pit according to an embodiment of the present application; and
fig. 9 is a flow chart of the construction of an excavation supporting structure according to another embodiment of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
In the following detailed description, reference is made to the accompanying drawings that form a part hereof and in which is shown by way of illustration specific embodiments of the application. In the drawings, like numerals describe substantially similar components throughout the different views. Various specific embodiments of the present application are described in sufficient detail below to enable those skilled in the art to practice the teachings of the present application. It is to be understood that other embodiments may be utilized and structural and logical changes may be made to the embodiments of the present application.
The application provides a novel excavation supporting construction, it can be on the horizontal direction cross the partial fender soil constructional device, changes into the cantilever state that keeps off the soil constructional device to there is the confined state to can reduce cantilever supporting construction's structure internal force, reduce structural deformation, can adapt to the needs of strutting of deeper excavation. In some embodiments, the soil retaining structure means include, but are not limited to: slope protection piles, underground continuous walls and the like.
The technical solution of the present application is further explained by the following specific embodiments. It should be understood by those skilled in the art that the following descriptions are only provided for facilitating the understanding of the technical solutions of the present application, and should not be used to limit the scope of the present application.
Fig. 1 is a schematic view of a foundation pit supporting structure according to an embodiment of the present application. Figure 2 is a top view of an excavation supporting system according to one embodiment of the present application. Fig. 3 and 4 are partial schematic views of a foundation pit supporting structure according to an embodiment of the present application. As will be described below with reference to the example of a slope protection pile, other cantilever support structures (such as an underground continuous wall) can be applied to the present invention as will be understood by those skilled in the art.
As shown, a foundation pit supporting structure 100 (hereinafter referred to as a "supporting structure") includes a plurality of slope protection piles 110, which are disposed around a foundation pit, and have a first end fixed to the bottom of the foundation pit and a second end located at the top of the foundation pit, so as to form a cantilever supporting structure for supporting the periphery of the foundation pit. In some embodiments, the slope protection pile 110 includes one or more strands of steel strands 101 that may provide pre-stress to the slope protection pile for reducing deformation of the slope protection pile into the foundation pit, and may also strengthen the slope protection pile. In some embodiments, the steel strands are unbonded steel strands, which facilitates tensioning of the steel strands to provide prestress for the slope protection piles. In some embodiments, the steel strands may also be bonded steel strands. In some embodiments, the steel strand is arranged eccentrically outside the foundation pit relative to the central axis of the slope protection pile, so that the second end of the slope protection pile is beneficial to generating a bending deformation trend deviating to the outside of the foundation pit, and the structural deformation of the slope protection pile can be reduced.
In some embodiments, the supporting structure 100 may further include one or more beams, which traverse at least a part of the slope protection piles in the horizontal direction and may generate a deformation tendency toward the outside of the foundation pit, so as to facilitate the slope protection piles to resist the structural internal force and the structural deformation generated to the slope protection piles from the outside of the foundation pit.
In some embodiments, the cross beam comprises a crown beam 120 disposed at the second end of the plurality of slope piles 110 so that the top ends of the plurality of slope piles may be restrained. In some embodiments, a crown beam may be disposed proximate the second end of the pile. In some embodiments, the number of the crown beams 120 may be multiple, and the multiple crown beams are connected to each other to form a closed structure to restrain the slope protection pile. For example: each side around the foundation pit is provided with a crown beam 120 which can restrain a plurality of slope protection piles on each side of the foundation pit, the crown beams on the two adjacent sides are mutually fixed, and the advantage of large longitudinal rigidity of the adjacent crown beams is utilized to form restraint of the end part, so that the crown beam at the upper opening of the foundation pit is closed, the second end of the slope protection pile becomes a fixed point, the structural internal force of the slope protection pile can be reduced, and the structural deformation is reduced. In some embodiments, the crown beam may be a concrete beam. In some embodiments, the crown beams may be loosely coupled to each other, with the ends of the crown beams being restrained by other objects (e.g., anchors).
In some embodiments, the crown beam 120 may further include one or more bundles of steel strands 111, which may provide pre-stressing of the crown beam for reducing deformation of the fender pile into the foundation pit, and may also strengthen the crown beam. In some embodiments, the steel strands are unbonded steel strands, which facilitates tensioning the steel strands to provide prestress to the crown beam. In some embodiments, the steel strands may also be bonded steel strands. In some embodiments, the steel strand is eccentric in the inboard setting of foundation ditch for the crown beam axis, is favorable to the crown beam to produce the deformation tendency of partial deviation outside the foundation ditch to can resist the structure internal force and the structural deformation that the foundation ditch outside produced the slope protection stake. When the steel strands preset in the tensioned crown beam exert prestress on the crown beam, the crown beam is subjected to the action of eccentric load, and the crown beam tends to bend and deform towards the outer side of the foundation pit. Because the two ends of the crown beam are restrained by the crown beam which is intersected with the crown beam, the deformation of the crown beam which is deflected to the inner side of the foundation pit after the foundation pit is excavated can be obviously reduced. In some embodiments, the steel strands may be tensioned at one end, anchored at one end, or tensioned at both ends, depending on the length of the crown beam. In some embodiments, to meet the requirements of the steel strand tensioning operation space, a working pit can be dug outside the foundation pit at the end part of the crown beam.
In some embodiments, the cross-section of the crown beam may be rectangular. In some embodiments, the cross-section of the crown beam may be a variable cross-section. In some embodiments, the cross-sectional shape of the crown beam may also be polygonal. In some embodiments, the cross-section at both ends of the crown beam is smaller than the cross-sectional area in the middle of the crown beam. According to an embodiment of the present application, referring to fig. 3, the crown beam may be curved (e.g., fish belly, etc.), that is, a straight edge is near the outer side of the foundation pit, and a curved surface is near the inner side of the foundation pit, so that the cross section of the middle portion of the crown beam is maximized, and the cross section is gradually reduced from the middle portion to the two ends, which is beneficial to saving concrete, increasing the deformation tendency of the crown beam toward the outer side of the foundation pit under the action of prestress, and increasing the horizontal constraint on the slope protection pile on the premise of obtaining the same pre-bending moment (that is, the rise of the steel strand is the; on the premise of the same concrete consumption, the rise of the steel strand can be increased, the bending moment pre-applied to the crown beam is increased, the deformation tendency of the steel strand towards the outside of the foundation pit under the action of prestress can be increased, and the horizontal constraint on the slope protection pile is increased.
In some embodiments, after the foundation pit exceeds a certain depth, the beam may further include a wale 130 disposed between the crown beam 120 and the bottom of the foundation pit at a different height from the crown beam to restrain the slope protection piles at different positions. In some embodiments, the wale is fixedly connected with the plurality of slope protection piles. Referring to fig. 4, a plurality of transverse reinforcing bars may be implanted on the slope protection pile, and the plurality of transverse reinforcing bars are anchored in the wale 130, thereby achieving a fixed connection between the wale and the slope protection pile. As will be appreciated by those skilled in the art, the connection by steel bar anchoring is only one connection, and other connections in the art may be applied to the present invention. For example: welding pre-embedded steel plates in the slope protection piles, connecting bolts and the like.
In some embodiments, the cross-beam comprises only one wale disposed between the first end and the second end of the pile. In some embodiments, the cross beam includes a crown beam disposed at or near the second end of the slope protection pile and a wale disposed between the first end and the second end of the slope protection pile. In some embodiments, the beam may include a plurality of wales.
In some embodiments, the number of wales 130 per course may be multiple, for example: each side around the foundation pit is provided with a waist rail 130 which can restrain a plurality of slope protection piles on each side of the foundation pit, the waist rails on two adjacent sides are mutually fixed to form restraint on two ends of the waist rail, so that the waist rails become displacement restraint points for the piles, the structural internal force of the slope protection piles can be reduced, and the structural deformation can be reduced. In some embodiments, two adjacent wales can be fixed to each other by the corner brace 121, the two ends of the wale can be restrained by the rigidity of the corner brace in the axial direction, and an operation space can be reserved outside the corner brace, so that some operations can be performed on the wales. In some embodiments, the wales may be loosely coupled to each other, and the ends of the wales may be restrained by other means (e.g., anchors). In some embodiments, the wale may be a concrete beam. In some embodiments, the cross-section of the wale may be similar to that of the crown beam, and thus, the description thereof is omitted.
In some embodiments, the wale 130 may further include one or more bundles of steel strands 122, which may be used to provide prestress to the wale and may also strengthen the wale. In some embodiments, the steel strands are unbonded steel strands, which facilitates tensioning the steel strands to provide prestress to the wale. In some embodiments, the steel strands may also be bonded steel strands. In some embodiments, the steel strand is eccentric in the inboard setting of foundation ditch for waist rail axis, is favorable to the waist rail to produce the bending deformation trend of partial foundation ditch outside to can reduce the structure internal force and the structural deformation that the pressure of foundation ditch outside soil produced the slope protection stake. When the steel strands pre-arranged in the waist beam are tensioned and prestress is applied to the waist beam, the waist beam is subjected to the action of eccentric load, and the bending deformation trend towards the outer side of the foundation pit is generated. In some embodiments, the steel strands may be tensioned at one end, anchored at one end, or tensioned at both ends, depending on the length of the wale. In some embodiments, to meet the requirement of the steel strand tensioning operation space, the wale is arranged inside the foundation pit, one side of the wale is in contact with the slope protection pile, and two ends of the wale are connected with the adjacent wale through the angle braces. In some embodiments, both ends of the steel strand may be disposed on the upper surface of the wale, so that it may not be necessary to provide an operation space for tensioning the steel strand. Such as: brackets with inclined surfaces are manufactured on the upper surfaces of the two ends of the waist rail, and the steel stranded wires can penetrate through the inclined surfaces of the brackets, so that the steel stranded wires can be conveniently tensioned; or the upper surfaces of the two ends of the wale are made into inclined surfaces, and the steel strands can penetrate through the inclined surfaces, so that tension is facilitated.
Fig. 5 is a schematic view of a foundation pit supporting structure according to another embodiment of the present application. As shown, the foundation pit support structure 500 includes a plurality of slope piles 510, a crown beam 520, a wale 530, and one or more anchor rods 540. Wherein, the crown beam 520 is arranged at the second end of the plurality of slope protection piles 510, and the wale 530 is arranged between the crown beam and the bottom surface of the foundation pit. The pickets 510, crown beams 520, and wales 530 include one or more steel strands for providing a pre-stress, similar to the embodiment of fig. 1, and thus will not be described in detail. One or more anchor rods 540 are arranged at one end or two ends of the crown beam 520 and/or the wale 530, one end of each anchor rod is connected with the end of the crown beam 520 or the wale 530, the other end of each anchor rod is connected with the ground, the end of the crown beam 520 and/or the wale 530 which do not form a closed structure can be restrained, so that the crown beam 520 and/or the wale 530 become displacement restraint points for piles, and pre-applied prestress generates a bending deformation trend towards the outer side of the foundation pit so as to resist the structural internal force and the structural deformation of the slope protection piles caused by the pressure of soil on the outer side of the foundation pit.
According to another embodiment of the present application, the supporting structure of the foundation pit may further include one or more rows of anchor rods 540, and the one or more rows of anchor rods 540 may be disposed on the crown beam 510 or the wale 530, which may restrain the crown beam or the wale. In some embodiments, one or more rows of anchor rods may be disposed on the entire beam at equal or unequal intervals (i.e., at any location). In some embodiments, the one or more rows of anchor rods may be disposed in a portion of the cross beam (e.g., in the middle of the cross beam or at both ends of the cross beam) at equal or unequal intervals. In some embodiments, one or more rows of anchor rods may also be provided on the slope protection piles 520, which may restrain the slope protection piles. In some embodiments, one or more rows of anchor rods may be arranged on the whole pile at equal intervals or at unequal intervals (i.e. at any position). In some embodiments, the one or more rows of anchor rods may also be disposed at equal intervals or unequal intervals at parts of the slope protection pile (e.g., the middle part of the slope protection pile or both ends of the slope protection pile).
In some embodiments, the main design parameters of the foundation pit supporting structure include the diameter, the spacing, the embedding depth of the slope protection piles, the arrangement shape, the number and the pre-stress of the steel strands in the pile body, the arrangement position, the section size and the arrangement shape, the number and the pre-stress of the steel strands in the beam. Optimization combination is carried out according to foundation pit geotechnical engineering conditions, excavation depth and surrounding environment conditions, and the deformation and the internal force of the supporting structure are calculated by adopting a finite element method or other methods until the deformation and the internal force of the supporting structure meet design requirements and the manufacturing cost meets economic requirements. The supporting structure of the present application will be further described by specific examples:
fig. 6A and 6B are schematic diagrams of stress calculations for an excavation supporting structure according to an embodiment of the present application. Figures 7A-7B are structural variations of different excavation supporting structures according to one embodiment of the present application.
According to one embodiment of the application, the following calculation example is calculated by using the foundation pit support design commercial software RSD3.0 of foundation research institute of Chinese institute of architectural science. Wherein, the design parameters of the soil body are as follows: the volume weight is 20kN/m3, the cohesive force is 20kPa, the internal friction angle is 25 degrees, and the excavation depth of the foundation pit is 15 m. The pile diameter of the slope protection pile of the common supporting structure is 1200mm, the pile spacing is 1.8m, the embedding depth is 10m, and the concrete strength grade of the pile body is C40. Referring to fig. 6A, a slope protection pile 601 of the supporting structure of the present application is the same as a slope protection pile of a general supporting structure, and 11 bundles of steel strands 602 are disposed in the slope protection pile, each bundle of steel strands is configured with 5 steel strands, and a tension control stress of a prestress is 1000N/mm2. Referring to fig. 6B, in the supporting structure of the present application, a prestressed wale 603 may be further disposed at a position-6 m of the slope protection pile, the cross-sectional dimension of the wale is 1200mmx800mm, 10 bundles of steel strands 604 are provided, each bundle has 5 steel strands, and the tension control stress of the prestress is 1300N/mm2。
Referring to fig. 7A and 7B, the pile top displacement of the slope protection pile of the general supporting structure is 225.7mm, and the maximum bending moment of the pile body is 5742 kn.m. In the supporting structure, the steel strand is arranged in the slope protection pile, and when the waist beam is arranged on the slope protection pile, the pile top displacement of the slope protection pile is 41.1mm, and the maximum bending moment of the pile body is 2206 kN.m. Therefore, compared with the common supporting structure, the supporting structure has the advantages that the reduction range of the pile top displacement of the slope protection pile is 81.8%, and the reduction range of the bending moment of the pile body is 61.6%. Therefore, the foundation pit supporting structure can obtain better performance in the aspects of controlling deformation and internal force of the supporting structure, and is deeper in applicable depth. And the deformation of the foundation pit can be controlled within the range of the national relevant standard requirements, and the foundation pit supporting structure completely meets the design requirements.
Fig. 8 is a flowchart of a method for constructing a retaining structure of a foundation pit according to an embodiment of the present application, and in step 810, a retaining pile is constructed. In some embodiments, the slope protection piles are constructed according to the design of the foundation pit supporting structure. In some embodiments, one or more bundles of unbonded steel strands may be pre-embedded in the pile. As understood by those skilled in the art, how to construct the slope protection piles is not described herein in detail.
In step 820, a crown beam is constructed. And (3) constructing a crown beam at the top of the constructed slope protection pile or at a position close to the top, connecting the crown beam with the top of the slope protection pile and restraining the slope protection pile. In some embodiments, the step of constructing the crown beam may include formwork erecting, rebar tying, steel strand tying, concrete pouring, demolding, and the like. In some embodiments, the steel strands are embedded in the crown beam, so that the crown beam is favorable for generating prestress to generate a tendency of bending deformation towards the outside of the foundation pit, and the pressure of soil outside the foundation pit is favorably resisted. In some embodiments, the crown beams are sealingly connected to one another to facilitate constraining the crown beams to one another. In some embodiments, the crown beams are not sealingly connected to each other.
In step 830, the steel strands in the crown beam are tensioned to provide a pre-stress to the crown beam to create a tendency to bend and deform towards the exterior of the foundation pit, thereby facilitating resistance to the pressure of the soil outside the foundation pit. In some embodiments, the steel strands in the top beam are tensioned according to the design scheme of the foundation pit supporting structure to achieve the prestress required by the design. In some embodiments, the steel strands in the crown beam may also be tensioned in steps. For example, according to the depth of the excavated foundation pit, the steel strands in the crown beam are tensioned to resist the pressure of soil outside the foundation pit.
In step 840, the steel strands in the slope protection piles are tensioned to provide prestress for the slope protection piles. In some embodiments, the steel strands in the slope protection pile are tensioned according to the design scheme of the foundation pit supporting structure so as to achieve the prestress required by the design. In some embodiments, the steel strands in the slope protection pile can be tensioned step by step. And e.g. stretching the steel strand in the slope protection pile according to the depth of the excavated foundation pit.
In step 850, the excavation of the foundation pit is completed until the excavation depth reaches the base.
Fig. 9 is a flow chart of the construction of an excavation supporting structure according to another embodiment of the present application. Step 910-930 is similar to step 810-830, and will not be described again.
In step 940, it is determined whether a wale is disposed in the foundation pit. In some embodiments, when the excavation depth of the foundation pit exceeds a certain depth, one or more waist beams may be arranged between the top beam and the base to increase the strength of the slope protection pile and resist the pressure of soil outside the foundation pit to the structural internal force and structural deformation of the slope protection pile.
In step 950, when the wale is disposed in the foundation pit, the foundation pit is excavated to a position where the wale is needed, and the wale is constructed. In some embodiments, the wale construction steps are similar to the crown beam and are not repeated. In some embodiments, steel strands may also be embedded in the wale. In some embodiments, the wales are closely connected to each other so that the wales are restrained with respect to each other. In some embodiments, the wales are not closely connected to each other. In some embodiments, one or more anchors may be disposed outside the wale to restrain the wale. In some embodiments, after the wale is constructed, the process continues to return to step 940 to determine whether a wale is still disposed in the foundation pit, and if the wale still exists, the steps 950 and 940 are repeated.
In step 960, when the wale is not present in the foundation pit, the foundation pit is excavated directly to the substrate, and the excavation of the foundation pit is completed.
The above embodiments are provided only for illustrating the present invention and not for limiting the present invention, and those skilled in the art can make various changes and modifications without departing from the scope of the present invention, and therefore, all equivalent technical solutions should also fall within the scope of the present disclosure.
Claims (23)
1. A prestressed concrete foundation pit supporting construction comprising:
the retaining structure device is arranged around the foundation pit, a first end of the retaining structure device is fixed at the bottom of the foundation pit, and a second end of the retaining structure device is arranged at the top of the foundation pit to form a retaining structure; and
one or more prestressed concrete beams traversing at least part of the retaining structure means in a horizontal direction and configured to create a tendency of deformation towards the outside of the foundation pit.
2. The prestressed concrete foundation pit supporting structure of claim 1, wherein the soil retaining structure means comprises a plurality of slope protecting piles.
3. The prestressed concrete foundation pit supporting structure of claim 1, wherein said retaining structure means comprises an underground continuous wall.
4. The prestressed concrete foundation pit supporting structure of claim 1, wherein the cross-beams form a closed structure or an open structure to restrain the soil retaining structure means.
5. The prestressed concrete foundation pit supporting structure of claim 1, wherein the cross-beam is plural, and the plural cross-beams are different in height to restrain the soil retaining structure means at different positions.
6. The prestressed concrete foundation pit supporting structure of claim 1, wherein the cross-beam comprises a crown beam provided at or near the second end of the soil retaining structure means.
7. The prestressed concrete foundation pit supporting structure of claim 6, wherein said cross-beam comprises a first wale disposed between first and second ends of said retaining structure means.
8. The prestressed concrete foundation pit supporting structure of claim 7, wherein the cross-beam includes a plurality of first wales, adjacent first wales being fixedly connected to each other by a connecting means, and further comprising reserving an operation space outside the connecting means within the foundation pit.
9. The prestressed concrete foundation pit supporting construction of claim 7, wherein said cross-beam comprises a second wale disposed between first and second ends of said soil retaining structure means.
10. The prestressed concrete foundation pit supporting structure of claim 1, wherein the cross-beams include one or more bundles of steel strands therein, the steel strands being arranged eccentrically to the inside of the foundation pit with respect to a central axis of the cross-beams, configured to provide prestressing to the cross-beams.
11. The prestressed concrete foundation pit supporting structure of claim 10, wherein both ends of the steel strand are positioned on upper surfaces of both ends of the cross beam or both end surfaces of the cross beam.
12. The prestressed concrete foundation pit supporting structure of claim 10, wherein said steel strands are unbonded steel strands or bonded steel strands.
13. The prestressed concrete foundation pit supporting structure of claim 1, wherein the cross-section of the beam is the same cross-section or variable cross-section.
14. The prestressed concrete foundation pit supporting structure of claim 13, wherein a cross-section of both ends of the cross-beam may be smaller than a cross-sectional area of a middle of the cross-beam.
15. The prestressed concrete foundation pit supporting structure of claim 1, further comprising: one or more anchor rods disposed at one or both ends of the cross beam; or one or more rows of anchors disposed on the beam configured to restrain the beam.
16. The prestressed concrete foundation pit supporting structure of claim 15, wherein said anchor rods are provided on said soil retaining structure means.
17. The prestressed concrete foundation pit supporting structure of claim 2, wherein the slope protection pile includes therein one or more bundles of steel strands arranged eccentrically to the outside of the foundation pit with respect to a central axis of the slope protection pile, configured to provide prestress to the slope protection pile.
18. A construction method of a prestressed concrete foundation pit supporting structure comprises the following steps:
constructing and arranging soil retaining structure devices around a foundation pit to be excavated; and
at a predetermined depth, the construction provides for the provision of one or more beams traversing at least part of the soil retaining structure means in a horizontal direction and configured to generate a tendency of deformation towards the outside of the foundation pit; and
and excavating the foundation pit to a preset foundation pit depth.
19. The construction method according to claim 18, further comprising: one or more interconnected prestressed crown beams are provided at or near the top end of the earth-retaining structure assembly.
20. The construction method according to claim 18, further comprising: a foundation pit is excavated and at a first depth in the earth-retaining structure assembly, a first wale or wales is constructed to provide one or more pre-stressed.
21. The construction method according to claim 18, further comprising: and excavating the foundation pit, and constructing to provide one or more prestressed second waist rails at a second depth of the soil retaining structure device.
22. The construction method according to claim 18, further comprising: the plurality of beams are interconnected to form a closed or an open structure to constrain the earth-retaining structure means.
23. The construction method according to claim 18, further comprising: one or more anchor rods are provided outside the cross beam, connected to one or both ends of the cross beam, or one or more rows of anchor rods connected to the cross beam, configured to restrain the cross beam.
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