Construction method and system of desert photovoltaic support enlarged foundation cast-in-place concrete pile

Abstract

The invention provides a construction method and system for a concrete cast-in-place pile of a desert photovoltaic support enlarged foundation. The construction method comprises the steps that a first pile casing is inserted into a sand body, the sand body in the first pile casing is removed, and first-time concrete pouring is conducted at the bottom in the first pile casing; the reinforcement cage, the second pile casing and the prefabricated part base plate are assembled and hoisted into the first pile casing before initial setting of concrete poured for the first time, and the second pile casing is separated from the prefabricated part base plate; second-time concrete pouring is conducted on the top of the prefabricated part chassis and between the first pile casing and the second pile casing; sand is filled between the first pile casing and the second pile casing, and the first pile casing is pulled out; the third time of concrete pouring is conducted in the second pile casing till the pile top elevation is above the pile top elevation; and the second pile casing is pulled out. The enlarged foundation cast-in-place pile is high in bearing capacity and pulling resistance, dry method hole forming is completely adopted, layered water injection and sand fixation are not needed, and the enlarged foundation cast-in-place pile is suitable for large-area mechanical flow construction of desert concrete cast-in-place piles.

Description

Technical Field

[0001] This invention relates to the field of cast-in-place pile construction technology, specifically to a construction method and system for cast-in-place concrete piles for enlarged foundations of desert photovoltaic supports. Background Technology

[0002] Photovoltaic desertification control refers to generating solar power through photovoltaic panels while sowing desert-loving plants beneath them, achieving the dual benefits of both producing new energy and controlling desertification. As an innovative desertification control model, photovoltaic desertification control has been widely promoted in various regions in recent years, achieving significant ecological and economic benefits.

[0003] Desert aeolian sand is loose and has poor self-stability, making the borehole walls prone to collapse during drilling. Using traditional drilling machinery presents multiple construction challenges, including borehole formation and concrete pouring. The commonly used construction methods and technical principles are as follows: 1. Water injection to fix sand and change the interparticle forces: By injecting water in layers (pressure 0.2-0.5MPa), the moisture content of the sand layer is increased to 12%-15%, the water film tension increases the capillary force between sand particles, and the shear strength is increased by 3 times.

[0004] 2. The dry drilling and grouting technology using casing is adopted. Rotary drilling rig is used in conjunction with hydraulic vibratory hammer. The casing is dug from the inside and driven from the outside. The casing wall thickness is ≥10mm. The hydraulic vibratory hammer is driven in sections (6m per section). The casing is circulated and driven in sections to form holes. The bottom end is embedded with a stable layer of ≥1m to form a continuous cylindrical support body. The pile is grouted in a waterless state of self-compacting concrete.

[0005] However, layered water injection for sand fixation requires a large amount of water, which is costly and difficult to guarantee a sufficient water supply in water-scarce desert areas. Furthermore, water injection only provides localized improvement and cannot completely solve the problem of borehole wall collapse during drilling. While dry-laying grouting with casing can achieve pile formation in a waterless state, it is only suitable for end-bearing piles that can provide high bearing capacity, and its pull-out resistance is generally poor (the casing is relatively smooth, resulting in insufficient lateral friction between the pile and the surrounding soil). Photovoltaic support foundations, however, have high pull-out resistance requirements, necessitating the use of friction piles or friction end-bearing piles. Therefore, neither of the above two construction methods is suitable for photovoltaic support foundations. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a construction method and system for enlarged foundation concrete cast-in-place piles for desert photovoltaic supports. This method utilizes two casings to solve the problem of borehole wall collapse during drilling, leverages the enlarged foundation to provide better bearing capacity, and exhibits greater lateral friction between the pile and the surrounding sand. Furthermore, the self-weight of the enlarged foundation and the weight of the sand above it provide additional pull-out resistance, effectively saving pile length and reducing construction difficulty. This construction method employs entirely dry drilling, eliminating the need for layered water injection for sand fixation, and is suitable for large-scale mechanized continuous-flow construction of desert concrete cast-in-place piles.

[0007] To address the aforementioned technical problems, this invention provides a construction method for enlarged foundation concrete cast-in-place piles for desert photovoltaic supports, comprising: Insert the first casing into the sand body, remove the sand body inside the first casing, and pour the first concrete at the bottom inside the first casing. Assemble the steel cage and the second casing with the precast chassis; Before the initial setting of the first concrete pour, the assembled steel cage, precast base plate, and second casing are hoisted into the first casing, the precast base plate is embedded into the first concrete pour, and the second casing is detached from the precast base plate. After the initial setting of the first concrete pour, a second concrete pour is carried out on the top of the precast component base and between the first and second casings. After the second concrete pour has initially set, sand is filled between the first and second casings, and the first casing is then removed. A third concrete pour is carried out inside the second casing, pouring it to a level above the top of the pile. After the second casing is removed, the third pour of concrete is cured after initial setting.

[0008] Furthermore, when the first casing is inserted into the sand body, the bottom elevation of the first casing is lower than the hole depth of the cast-in-place pile; after the sand body inside the first casing is removed, the elevation of the sand body inside the first casing is lower than the hole depth of the cast-in-place pile.

[0009] In some embodiments, the method of assembling the reinforcing cage and the second casing with the precast chassis includes: Insert the longitudinal main bars of the steel cage into the precast component base plate, and weld and fix the longitudinal main bars to the transverse steel bars in the precast component base plate; Insert the bottom of the second protective sleeve into the precast chassis, rotate and lift the second protective sleeve so that the hook of the second protective sleeve engages in the locking hole at the top of the precast chassis.

[0010] In some embodiments, the method of detaching the second casing from the precast chassis includes: Press down on the second protective sleeve so that the hook of the second protective sleeve disengages from the locking hole on the top of the precast chassis. Rotate the second protective sleeve so that the bottom of the second protective sleeve can be pulled out from the precast chassis at any time.

[0011] Furthermore, before removing the second casing, the second casing is vibrated to ensure that the sand on the outside of the second casing and the third pour of concrete are compacted.

[0012] Furthermore, the third concrete pouring uses a concrete guide pipe. During the process of pulling out the second casing, the concrete guide pipe is also pulled out simultaneously and the concrete is continuously poured through the concrete guide pipe to ensure that the top liquid level of the third concrete pour does not drop.

[0013] Furthermore, after the second casing is completely pulled out, a formwork is placed at the top of the pile, and concrete is poured using the grouting pipes pre-fixed to the reinforcing cage to ensure that the top liquid level of the third concrete pour does not drop.

[0014] On the other hand, the present invention provides a system for implementing the construction method of the enlarged foundation concrete cast-in-place pile of the desert photovoltaic support, comprising: The first casing is used to protect the wall during foundation construction. A precast chassis, which is used to fix the reinforcing cage of the cast-in-place pile; The second casing, with a diameter smaller than that of the first casing, is used for wall protection during the construction of the cast-in-place pile. The bottom of the second casing is detachably connected to the precast chassis, which is used to hoist the precast chassis into the bottom of the first casing.

[0015] In some embodiments, the precast chassis includes a hollow chassis body with multiple transverse steel bars fixedly disposed inside the chassis body for fixing a steel cage. A connecting portion is provided at the top of the chassis body, and the chassis body is detachably connected to a second protective sleeve through the connecting portion.

[0016] In some embodiments, the connecting part includes multiple sliding grooves and multiple locking holes formed on the top of the disk body. The multiple sliding grooves and multiple locking holes are arranged in a one-to-one correspondence. The locking holes are arranged at the tail of the corresponding sliding grooves. The bottom of the second protective tube is provided with a hook. The bottom of the second protective tube can be inserted into the disk body through the sliding grooves. The hook can be inserted upward into the corresponding locking hole.

[0017] The beneficial effects of this invention are as follows: 1. This invention uses a double-casing system for synergistic support. The first casing forms the cavity of the enlarged foundation, while the second casing protects the pile hole wall. The entire process is dry drilling, eliminating the need for layered water injection for sand fixation. This completely avoids the water resource dependence of traditional water injection for sand fixation and is suitable for large-area mechanized flow construction of desert concrete cast-in-place piles.

[0018] 2. The present invention uses a precast chassis + concrete structure to form an enlarged foundation, which increases the bearing area and enhances the end bearing capacity of the cast-in-place pile. In addition, the sand body above the enlarged foundation can provide additional pull-out resistance, which can effectively save pile length.

[0019] 3. This invention precisely controls the extraction time of the two casings and forms an enlarged foundation pile through three concrete pours. The first two concrete pours are used to form the enlarged foundation, and the last concrete pour is used to form the pile.

[0020] 4. In this invention, grouting is continuously injected during the removal of the second casing and after the second casing is completely removed, which solves the problem of concrete loss due to contact with sand, resulting in a drop in the top liquid level of the concrete.

[0021] 5. The prefabricated chassis and the second protective casing of the present invention are detachably connected by hooks and holes, which enables rapid assembly and precise disassembly of the prefabricated chassis and the second protective casing, improves hoisting efficiency and ensures chassis positioning accuracy. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the first casing after it has been inserted into the sand body according to the present invention; Figure 2 This is a schematic diagram illustrating the process of removing sand from the first casing according to the present invention. Figure 3 This is a schematic diagram illustrating the first concrete pouring for this invention. Figure 4 This is a schematic diagram of the precast chassis embedded in the first concrete body according to the present invention. Figure 5 This is a top view of the prefabricated chassis of the present invention; Figure 6 This is a top view of the second protective sleeve of the present invention; Figure 7 This is a schematic diagram of the structure when the bottom of the second protective sleeve of the present invention is inserted into the prefabricated chassis; Figure 8 This is a schematic diagram of the structure of the second protective sleeve of the present invention when the hook is inserted into the card hole; Figure 9 This is a schematic diagram illustrating the second concrete pouring process of this invention. Figure 10 This is a schematic diagram of the present invention filling sand between the first and second casings; Figure 11 This is a schematic diagram showing the first protective sleeve completely removed after the present invention has been fully removed; Figure 12 This is a schematic diagram illustrating the third concrete pouring in this invention. Figure 13 This is a schematic diagram of the second protective sleeve being pulled out according to the present invention; Figure 14 This is a schematic diagram of placing a template at the top of the pile after the second casing of the present invention has been completely pulled out; Figure 15 This is a schematic diagram of the cutting grouting conduit of the present invention.

[0023] Reference numerals: First casing 1; tip 11; second casing 2; hook 21; auger 3; first concrete body 4; precast base 5; disc 51; transverse reinforcement 52; chute 53; locating hole 54; central hole 55; anchoring reinforcement 56; reinforcement cage 6; longitudinal main reinforcement 61; stirrup 62; concrete guide pipe 7; grouting guide pipe 8; second concrete body 9; formwork 10. Detailed Implementation

[0024] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0025] like Figure 1 As shown, this invention provides a construction method for a concrete cast-in-place pile for an enlarged foundation of a desert photovoltaic support, comprising: S1. Insert the first casing 1 into the sand body, remove the sand body inside the first casing 1, and pour the first concrete at the bottom inside the first casing 1.

[0026] Step S1 specifically includes: like Figure 1 As shown, the first casing 1 is inserted into the sand body by hammering or static pressure, aligned with the center of the pile position. The first casing 1 is a smooth steel cylinder with a thickness of more than 20mm. The bottom of the first casing 1 is machined with a pointed tip 11 to facilitate the insertion of the first casing 1 into the sand body. The length of the first casing 1 is greater than the hole depth of the pile. After the first casing 1 is inserted into the hole, the pointed tip 11 is lower than the hole depth of the pile. like Figure 2 As shown, the auger drill 3 is used to remove the sand from the first casing 1. The auger drill 3 should penetrate deeper than the hole depth of the cast-in-place pile. like Figure 3 As shown, the first concrete is poured at the bottom of the first casing 1 to form the first concrete body 4. The depth of the first concrete pour should be such that after the precast base plate 5 is embedded, the anchoring steel bars 56 of the precast base plate 5 are completely submerged in the first concrete body 4.

[0027] S2. Assemble the steel cage 6 and the second casing 2 with the precast chassis 5. This step can be performed simultaneously with step S1.

[0028] like Figures 4 to 6As shown, the diameter of the second protective cylinder 2 is smaller than that of the first protective cylinder 1. The second protective cylinder 2 is made of smooth steel cylinder with a thickness of more than 10mm. Multiple hooks 21 are fixedly provided at the bottom of the second protective cylinder 2. The hooks 21 can be welded to the second protective cylinder 2. The cross section of the hooks 21 is U-shaped. The precast chassis 5 includes a hollow cylindrical chassis 51. Anchor steel bars 56 are welded to the sides of the chassis 51 and roughened to ensure the bonding strength between the chassis 51 and the first concrete body 4. Transverse steel bars 52 are welded inside the chassis 51 for connecting the steel cage 6. A central hole 55 is opened at the top center of the chassis 51, through which the steel cage 6 can be inserted into the chassis 51. A groove 53 is opened on the wall of the central hole 55. The groove 53 includes a wider front section and a narrower rear section. Multiple locking holes 54 are also opened on the top of the chassis 51. The multiple locking holes 54 are evenly arranged around the hollow and correspond to the rear section of the groove 53.

[0029] It is understandable that, such as Figure 7 , 8 As shown, due to the wider width of the front section of the slide groove 53, the hook 21 of the second protective cylinder 2 can be inserted into the disc body 51 through the front section of the slide groove 53. As the second protective cylinder 2 rotates, the connection between the hook 21 and the second protective cylinder 2 slides into the rear section of the slide groove 53. At this time, when the second protective cylinder 2 is lifted, the hook 21 can be engaged in the locking hole 54 (as shown). Figure 8 As shown in the figure, this achieves a detachable connection between the second protective sleeve 2 and the disc body 51. The length of the hook 21 should be more than twice the thickness of the top surface of the disc body 51, and the size of the end of the hook 21 should match (slightly smaller than) the size of the locking hole 54.

[0030] Step S2 specifically includes: The steel cage 6 of the cast-in-place pile is tied. The steel cage 6 includes multiple longitudinal main bars 61 and multiple stirrups 62. The grouting pipe 8 is tied to the longitudinal main bars 61 of the steel cage 6. The longitudinal main bars 61 of the steel cage 6 are inserted into the precast base plate 5 through the central hole 55. The longitudinal main bars 61 are welded and fixed to the transverse steel bars 52 in the precast base plate 5. Insert the hook 21 of the second protective sleeve 2 completely into the precast chassis 5, rotate and lift the second protective sleeve 2 so that the hook 21 of the second protective sleeve 2 is engaged in the locking hole 54 at the top of the precast chassis 5.

[0031] S3. Before the initial setting of the first poured concrete, the assembled steel cage 6, precast base plate 5, and second casing 2 are hoisted into the first casing 1, the precast base plate 5 is embedded into the first poured concrete, and the second casing 2 is separated from the precast base plate 5.

[0032] Step S3 specifically includes: like Figure 4As shown, before the initial setting of the first poured concrete, the assembled steel cage 6, precast base plate 5, and second casing 2 are hoisted into the first casing 1. The anchoring steel bars 56 of the precast base plate 5 are completely submerged in the first poured concrete. The second casing 2 is pressed down and rotated so that the hook 21 of the second casing 2 disengages from the locking hole 54 of the precast base plate 5. The hook 21 of the second casing 2 can be pulled out from the precast base plate 5 at any time.

[0033] S4. After the initial setting of the first concrete pour, a second concrete pour is carried out between the top of the precast base plate 5 and the first casing 1 and the second casing 2; as follows: Figure 9 As shown, the second concrete is poured to form a second concrete body 9, which is evenly laid on the top of the precast base plate 5, and its thickness is not less than 300mm.

[0034] S5, such as Figure 10 , 11 As shown, after the second concrete pour has initially set, sand is filled between the first casing 1 and the second casing 2. The first casing 1 is then pulled out. The sand filling between the first casing 1 and the second casing 2 can be the sand removed in step S1. After the first casing 1 is pulled out, the sand automatically fills the space between the first casing 1 and the second casing 2 and comes into close contact with the second casing 2.

[0035] S6, such as Figure 12 As shown, a concrete guide pipe 7 is used to pour concrete into the second casing 2 for the third time, pouring it to a height above the top of the pile. The concrete poured in the third time will form a cast-in-place pile. After the third concrete pour is completed, the second casing 2 is vibrated using a vibrating rod or other device to compact the sand body outside the second casing 2 and the concrete poured in the third time. At the same time, a plate vibratory rammer is used to compact the sand body.

[0036] S7. Pull out the second casing 2, and cure the concrete poured for the third time after it has initially set.

[0037] Step S7 specifically includes: like Figure 13 As shown, the second casing 2 is slowly pulled out before the third concrete pour initially sets. During the process of pulling out the second casing 2, the concrete guide pipe 7 is also pulled out simultaneously. The concrete will be lost due to contact with the sand. Therefore, the concrete guide pipe 7 should continue to pour concrete to ensure that the top liquid level of the third concrete pour does not drop.

[0038] like Figure 14 As shown, after the second casing 2 is completely pulled out, the formwork 10 is placed at the top of the pile, and the concrete is poured using the grouting pipe 8 pre-fixed on the reinforcing cage 6 (the grouting pipe 8 continuously injects grout at a pressure of more than 0.8 MPa) to ensure that the top liquid level of the third concrete pour does not drop.

[0039] After the third pour of concrete has initially set, cover the top surface with a curing membrane, and simultaneously place straw checkerboard mats for sand control and curing. Remove the formwork, cut and seal the grouting conduit 8, as shown. Figure 15 As shown.

[0040] The present invention will now be compared with a traditional cast-in-place pile, assuming a pile diameter of 300mm, a precast base plate 5 diameter of 500mm, and a first casing 1 diameter of 600mm; compared with a traditional cast-in-place pile with a pile diameter of 300mm: 1. The bottom cross-sectional area of ​​a 300mm diameter cast-in-place concrete pile is 0.283m². 2 The cross-sectional area of ​​the concrete base at the bottom of the foundation was increased by 1.131m². 2 The bottom cross-sectional area has increased threefold, and the expanded foundation can provide greater vertical bearing capacity. 2. The two types of piles have the same side surface area in contact with the sand body, and the vertical pull-out force provided by the calculated lateral friction is basically the same. However, the temporary steel casing used in this invention can effectively solve the problem of easy collapse of the hole wall during drilling. 3. Increasing the self-weight of the concrete foundation at the bottom of the foundation can provide greater pull-out resistance. At the same time, increasing the weight of the sand body above the foundation (based on a preliminary calculation of a 2m pile length, the volume of the upper sand body is about 1.696m³, the dry density of natural sand is 1400kg / m³, and the weight of the upper sand body is about 2375kg) can also provide additional pull-out resistance (23.275kN), which can effectively save pile length.

[0041] 4. The construction method of this invention adopts dry drilling without the need for layered water injection for sand fixation, and is suitable for large-area mechanized flow construction of concrete cast-in-place piles for desert photovoltaic support foundations.

[0042] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A construction method for a concrete cast-in-place pile for an enlarged foundation of a desert photovoltaic support system, characterized in that, include: Insert the first casing (1) into the sand body, remove the sand body inside the first casing (1), and pour the first concrete at the bottom inside the first casing (1); Assemble the steel cage (6) and the second casing (2) with the precast chassis (5); Before the initial setting of the first concrete pour, the assembled steel cage (6), precast base plate (5), and second casing (2) are hoisted into the first casing (1), the precast base plate (5) is embedded into the first concrete pour, and the second casing (2) is separated from the precast base plate (5). After the initial setting of the first concrete pour, a second concrete pour is carried out between the top of the precast base plate (5), the first casing (1), and the second casing (2); After the concrete poured in the second pour has set, sand is filled between the first casing (1) and the second casing (2), and the first casing (1) is pulled out. A third concrete pour is carried out into the second casing (2) until it reaches above the top elevation of the pile. Remove the second casing (2), and cure the concrete poured for the third time after it has initially set.

2. The construction method of the enlarged foundation concrete cast-in-place pile for desert photovoltaic support according to claim 1, characterized in that, When the first casing (1) is inserted into the sand body, the bottom elevation of the first casing (1) is lower than the hole depth of the cast-in-place pile; after the sand body inside the first casing (1) is removed, the elevation of the sand body inside the first casing (1) is lower than the hole depth of the cast-in-place pile.

3. The construction method of the enlarged foundation concrete cast-in-place pile for desert photovoltaic support according to claim 1, characterized in that, The method of assembling the reinforcing cage (6) and the second casing (2) with the precast chassis (5) includes: Insert the longitudinal main bars (61) of the steel cage (6) into the precast base plate (5), and weld the longitudinal main bars (61) to the transverse steel bars (52) in the precast base plate (5); Insert the bottom of the second protective sleeve (2) into the precast chassis (5), rotate and lift the second protective sleeve (2) so that the hook (21) of the second protective sleeve (2) is engaged in the locking hole (54) at the top of the precast chassis (5).

4. The construction method of the enlarged foundation concrete cast-in-place pile for desert photovoltaic support according to claim 1, characterized in that, Methods for detaching the second casing (2) from the precast chassis (5) include: Press down the second protective sleeve (2) so that the hook (21) of the second protective sleeve (2) disengages from the locking hole (54) at the top of the precast chassis (5). Rotate the second protective sleeve (2) so that the bottom of the second protective sleeve (2) can be pulled out from the precast chassis (5) at any time.

5. The construction method of the enlarged foundation concrete cast-in-place pile for desert photovoltaic support according to claim 1, characterized in that, Before pulling out the second casing (2), vibrate the second casing (2) to make the sand on the outside of the second casing (2) and the concrete poured for the third time compacted.

6. The construction method of the enlarged foundation concrete cast-in-place piles for desert photovoltaic support according to any one of claims 1 to 5, characterized in that, The third concrete pouring uses a concrete guide pipe (7). During the process of pulling out the second casing (2), the concrete guide pipe (7) is also pulled out simultaneously and the concrete is continuously poured by the concrete guide pipe (7) to ensure that the top liquid level of the third concrete pour does not drop.

7. The construction method of the enlarged foundation concrete cast-in-place pile of the desert photovoltaic support according to claim 6, characterized in that, After the second casing (2) is completely pulled out, a template (10) is placed at the top of the pile, and concrete is poured using the grouting pipe (8) that is pre-fixed on the steel cage (6) to ensure that the top liquid level of the third concrete pour does not drop.

8. A system for implementing the construction method of the enlarged foundation concrete cast-in-place piles for desert photovoltaic supports as described in any one of claims 1 to 7, characterized in that, include: The first casing (1) is used to protect the wall during foundation construction; Precast chassis (5), the precast chassis (5) is used to fix the steel cage (6) of the cast-in-place pile; The second casing (2) has a smaller diameter than the first casing (1) and is used for wall protection during the construction of the cast-in-place pile. The bottom of the second casing (2) is detachably connected to the precast chassis (5) and is used to hoist the precast chassis (5) into the bottom of the first casing (1).

9. The system according to claim 8, characterized in that, The precast chassis (5) includes a hollow chassis (51), with multiple transverse steel bars (52) fixedly installed inside the chassis (51). The transverse steel bars (52) are used to fix the steel cage (6). A connecting part is provided on the top of the chassis (51), and the chassis (51) is detachably connected to the second protective sleeve (2) through the connecting part.

10. The system according to claim 8, characterized in that, The connecting part includes multiple sliding grooves (53) and multiple locking holes (54) on the top of the disc body (51). The multiple sliding grooves (53) and multiple locking holes (54) are arranged in a one-to-one correspondence. The locking holes (54) are arranged at the tail of the corresponding sliding grooves (53). The bottom of the second protective tube (2) is provided with a hook (21). The bottom of the second protective tube (2) can be inserted into the disc body (51) through the sliding grooves (53). The hook (21) can be inserted upward into the corresponding locking holes (54).

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