CN112252355A - Prefabricated expanded packing key type digging foundation for power transmission line and construction method thereof - Google Patents

Abstract

The invention discloses a prefabricated expanded packing key type digging foundation for a power transmission line and a construction method thereof, wherein the foundation comprises a concrete assembly, prestressed reinforcements and prefabricated root keys; the concrete assembly is a disc expanding component, and the middle part of the concrete assembly is of a hollow structure; the concrete assembly is provided with a plurality of penetrating reserved prestressed holes along the height direction, and a plurality of root key reserved holes along the bottom surface direction; the plurality of concrete assemblies are sequentially stacked in the foundation pit, and the prestressed reinforcement penetrates through corresponding reserved prestressed holes in the plurality of concrete assemblies to assemble the concrete assemblies to form a foundation main body; and the prefabricated root key penetrates through the root key preformed hole and is inserted into the side wall of the foundation pit. The prefabricated expanded packing key type digging foundation provided by the invention can obviously save the construction period, fully play the synergistic effect of the foundation and the soil body, improve the horizontal load resistance and the overturning resistance of the foundation, and reduce the construction safety risk and the construction cost.

Description

Prefabricated expanded packing key type digging foundation for power transmission line and construction method thereof

Technical Field

The invention relates to the technical field of power transmission line iron tower foundations, in particular to a prefabricated expanded packing key type digging foundation for a power transmission line and a construction method thereof.

Background

More and more power transmission lines pass through mountain areas such as high mountains and high mountains, and face the difficulties of complex service environments such as saline soil and frozen soil and lack of building materials. The prefabricated assembly type foundation is applied to engineering practice gradually in the advantages of rapid construction, easy quality control, good durability and concentrated transportation of building materials, and the excavated foundation is high in bearing capacity and less in earthwork operation due to the characteristic of original soil, so that large-area damage to terrain and environment caused by excavation of foundation types such as plate type foundations and pile group foundations is avoided, and the prefabricated assembly type foundation is widely applied to power transmission lines in mountainous areas and tower positions with high requirements on environmental protection. The assembled foundation and the digging type foundation are combined together to form the assembled digging type foundation which has the advantages of wide application range, short construction period, good durability, high bearing capacity, easy quality control, less terrain damage and environmental protection.

On the other hand, with the enlargement of the scale of the power grid, the safe operation of the power grid is increasingly threatened by extreme severe weather and sudden disasters, which easily causes the damage of the power grid. In the foundation rush-repair process, the assembly type digging foundation can save the concrete pouring and maintaining time with larger volume, and accelerate the rush-repair speed of the transmission line tower foundation, especially the rush-repair speed under the complex mountain terrain.

However, at present, the research and application of the assembly type digging type foundation are few, the assembly type foundation is mainly a plate column type foundation or a step type foundation, the existing undisturbed soil assembly foundation type is mainly a steel pipe pile or a concrete pipe pile, but due to the limitation of field conditions, the anchoring force between the pipe pile and the foundation soil is difficult to control due to the pipe sinking process adopted in the power transmission line, the reliability of the uplift bearing capacity is poor, and the practical application is few. The main type of the emergency repair foundation is a steel reinforced concrete digging type foundation, besides a steel bar truss is used for replacing steel bars, a large amount of concrete still needs to be poured on site, the limitation of the concrete curing age on the emergency repair construction period is not obviously changed, and the following problems exist in the application: 1) the large-volume concrete pouring and maintenance can restrict the rush repair or construction period. 2) In areas where building materials are scarce, cement, gravel and water transportation are problematic. 3) In, the tower position of strong corruption need adopt and carry out anticorrosive design, and the concrete that adopts high grade number must use compulsory mixer to mix, adopts outer protection such as anticorrosive paint to need multichannel process operation, can make the difficult degree of salvage construction and construction cycle greatly increased. 4) When rush-repair is carried out in winter, the concrete needs to adopt winter construction measures, and if the concrete meets rain and snow weather, the operation difficulty and the workload can be greatly improved.

For solving the above-mentioned problem, improve the bearing performance that the assembled was drawn and is dug type basis and salvage and draw and dig type basis, the construction is convenient fast and the suitability under the multiclass environment, needs a prefabricated packing key formula that expands that is used for transmission line to draw and dig type basis.

Disclosure of Invention

Aiming at the defect of poor reliability of the pulling resistance bearing capacity of the foundation in the prior art, the invention aims to provide a prefabricated expanded packing key type digging foundation for a power transmission line and a construction method thereof, and the prefabricated expanded packing key type digging foundation has the advantages of being fast in construction, high in foundation reliability, strong in applicability, environment-friendly and the like.

In order to achieve the purpose, the invention adopts the following technical scheme:

a prefabricated expanded packing key type digging foundation for a power transmission line comprises a concrete assembly, prestressed reinforcements and prefabricated root keys; the concrete assembly is a disc expanding component, and the middle part of the concrete assembly is of a hollow structure; the concrete assembly is provided with a plurality of penetrating reserved prestressed holes along the height direction, and a plurality of root key reserved holes along the bottom surface direction;

the plurality of concrete assemblies are sequentially stacked in the foundation pit, and the prestressed reinforcement penetrates through corresponding reserved prestressed holes in the plurality of concrete assemblies to assemble the concrete assemblies to form a foundation main body;

the prefabricated root key penetrates through the root key preformed hole and is inserted into the side wall of the foundation pit; cement paste is filled in a gap between the concrete composite member and the foundation pit; and filling and digging residual soil for foundation pit construction by the hollow structure.

As a further improvement of the invention, the concrete assembly is one or more of a circular truncated cone assembly and an equal-diameter assembly; the concrete assembly is a right circular truncated cone or an inverted circular truncated cone.

As a further improvement of the invention, the concrete assembly at the top is embedded with anchor bolts.

As a further improvement of the invention, the concrete composite member is prefabricated and molded by adopting lightweight aggregate concrete, fiber concrete or self-compacting concrete, and the surface of the concrete composite member is coated with anticorrosive paint.

As a further improvement of the invention, the hollow structure is a cylinder or a circular truncated cone.

As a further improvement of the invention, the concrete assembly height should not be less than its average diameter; the strength of the concrete assembly is not lower than C30.

As a further improvement of the invention, the prefabricated root key adopts a prefabricated concrete root key, a prefabricated steel reinforced concrete root key or a metal root key; prefabricated root key one end is sharp portion, and the other end is provided with pre-buried steel sheet, and hole for connection is left at pre-buried steel sheet center.

As a further improvement of the invention, the prefabricated root keys are circularly and symmetrically distributed vertically or are arranged on the concrete assembly in a staggered way by adopting an upper layer and a lower layer; the inner side of the concrete assembly is provided with a root key jacking equipment slideway.

A construction method for a prefabricated expanded packing key type digging foundation of a power transmission line comprises the following steps:

the prefabricated concrete composite member and the prefabricated root key;

digging a foundation pit in undisturbed soil to a preset depth; sequentially stacking, positioning and arranging the concrete composite member, and perforating prestressed reinforcements to assemble the concrete composite member into a foundation main body;

pushing the prefabricated root key layer by layer to enable the prefabricated root key to penetrate through the root key preformed hole and be inserted into the side wall of the foundation pit;

grouting cement slurry into the gap between the concrete assembly and the foundation pit; and burying construction residual soil into the hollow structure of the concrete assembly.

As a further improvement of the invention, the cement slurry is poured from the bottom of the foundation pit through the grouting guide pipe to gradually fill the gaps on the periphery of the foundation pit.

The invention has the following beneficial effects:

the invention adopts the mode of stacking a plurality of sections of concrete assemblies to replace the traditional on-site pouring foundation, eliminates the procedures of binding and placing a reinforcement cage on site, pouring and maintaining concrete, and only needs to pour a small amount of early-strength quick-setting mortar or fine aggregate concrete between the foundation and the foundation soil, thereby shortening the construction period. The spliced root key type excavation foundation mainly bears the load by the root key and foundation soil, under the condition of emergency repair or short construction period, mortar and fine aggregate concrete can not be filled in the design through checking calculation, and the foundation can be immediately borne after foundation pit excavation, foundation placement and foundation pit backfilling are completed due to the absence of the working procedure of mortar and concrete on-site pouring, so that the construction period is obviously saved. When the construction period is not short, the side friction resistance of the foundation and the foundation can be exerted after the strength of mortar or fine stone concrete is formed, and the side friction resistance and the foundation can act together with a root key to further enhance the reliability. The procedures of manufacturing and binding reinforcing steel bars on site and pouring and curing foundation concrete are omitted, and the construction period is shortened; different assemblies can be flexibly combined according to actual requirements and used for different geological conditions; the root key type structure enhances the synergistic effect between the soil body and the foundation, fully exerts the bearing effect of the soil body and improves the vertical bearing capacity and the stability; the residual soil for construction can be filled into the hollow part of the foundation, so that the damage to the landform and the environment in the mountainous area is reduced. The prefabricated expanded packing key type digging foundation provided by the invention can obviously save the construction period, fully play the synergistic effect of the foundation and the soil body, improve the horizontal load resistance and the overturning resistance of the foundation, reduce the construction safety risk and the engineering cost, reduce the construction waste and the environmental damage, improve the concrete quality and the foundation durability, and achieve the purposes of saving the cost and protecting the environment.

Furthermore, more equal-diameter assemblies can be adopted for bedrock geology, and more circular truncated cone assemblies can be adopted for loess, silt and other geology; different assemblies can be flexibly adopted according to different geological conditions, so that the applicability is strong;

furthermore, a bionic structure is formed by adopting the root keys, the horizontal root keys are uniformly distributed in all soil layers, and the function of bearing the original soil is fully exerted by utilizing the bond stress and the tight embedding effect of the soil body on the periphery of the foundation to the root keys. The arrangement of the multilayer root keys can flexibly arrange the multilayer root keys from top to bottom, and compared with the traditional bottom-expanded excavation type foundation, the foundation can be moved to bear foundation soil in a larger range by only arranging the expanded head at the bottom of the foundation, so that the bearing capacity is higher, the size and the burial depth of the foundation can be reduced, and the manufacturing cost is saved;

furthermore, the foundation pit is in the operation of equal-diameter pore-forming, and the reaming operation of the traditional excavation type foundation at the bottommost part of the foundation pit is cancelled, so that one of main hazard sources of construction accidents of the traditional excavation type foundation is eliminated, and meanwhile, the bottommost layer root key in the multilayer root keys can replace the bottom reaming to improve the bearing capacity.

Furthermore, the multi-section sectional type spliced component has smaller volume and weight of a single component, and can avoid the adoption of large transport vehicles and construction machines in the sections with poor traffic and field conditions, thereby reducing the construction difficulty and the construction cost;

furthermore, the construction residual soil of the excavated foundation can be placed in the hollow part of the foundation, so that the treatment capacity of the residual soil on site is reduced, and the environment protection is facilitated;

furthermore, the assembly is prefabricated indoors, new materials and technologies such as lightweight aggregate concrete, fiber concrete and the like can be adopted, the problems of poor field manufacturing conditions and the like are avoided, and the popularization of the new materials and the new technologies is facilitated.

Drawings

FIG. 1 is a schematic structural view of a prefabricated hollow digging foundation of a circular truncated cone;

FIG. 2 is a schematic view of a structure of an inverted circular truncated cone prefabricated hollow digging foundation;

FIG. 3 is a schematic view of a right circular table assembly;

FIG. 4 is a schematic view of an inverted frustum assembly;

FIG. 5 is a schematic view of an isometric assembly;

FIG. 6 is a front view of a precast concrete root key;

FIG. 7 is a side view of a precast concrete root key;

wherein: the method comprises the following steps of 1-a circular truncated cone assembly, 2-an equal-diameter assembly, 3-a prefabricated root key, 4-a prestressed reinforcement, 5-a foundation bolt, 6-an embedded steel plate and 7-a reserved prestressed hole.

Detailed Description

In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, and not all embodiments. 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, shall fall within the scope of protection of the present invention.

It will be understood that when an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may be present. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for illustrative purposes only and do not represent the only embodiments.

Unless defined otherwise, 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 invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

As shown in fig. 1 and 2, the prefabricated hollow excavation foundation for the power transmission line comprises a circular truncated cone assembly 1, an equal-diameter assembly 2, a prefabricated root key 3 and prestressed reinforcements 4.

The circular truncated cone assembly 1 and the equal-diameter assembly 2 can be combined in different ways according to actual requirements, the circular truncated cone assembly 1 and the equal-diameter assembly 2 are combined and connected through the prestressed reinforcement 4, and the root key 3 extends outwards for a certain length from the inside of the circular truncated cone assembly 1. The outer side of the foundation is vertically connected with a plurality of root keys, and the root keys extend out of each assembly for a certain length. The gravity centers of all the assemblies are on the same plumb line, and the reserved holes are communicated up and down.

As shown in fig. 3 to 5, the circular truncated cone assembly 1 adopts a hollow type, and the middle hollow part can adopt a cylindrical or circular truncated cone type; the side, close to the larger diameter, of the circular truncated cone assembly 1 is provided with a prefabricated root key 3, and a root key pushing hole needs to be reserved in advance; bolt connecting holes need to be reserved on two sides of the root key reserved hole; the constant diameter assembly 2 is of a cylindrical type and the internal hollow portion is also of a cylindrical type.

The circular truncated cone assembly 1 can adopt a right circular truncated cone or an inverted circular truncated cone. The middle of the circular truncated cone assembly 1 is a hollow part, and the shape of the hollow part can adopt a cylindrical shape or a circular truncated cone shape. 4 holes of prestressed reinforcement are reserved symmetrically in the circular truncated cone assembly 1; an anchor bolt 5 is embedded in the top circular truncated cone assembly 1.

The round table assembly 1 is provided with root key pushing holes in the part with larger diameter in the round table variable cross section, and the reserved holes are uniformly distributed along the circumferential direction and have the size slightly larger than that of the root keys; bolt connecting holes are reserved on two sides of the root key reserved hole.

The prefabricated root key 3 can adopt a prefabricated concrete root key, a prefabricated steel reinforced concrete root key or a metal root key. The root keys 3 are circularly and symmetrically distributed vertically or are arranged outside the combined foundation in a staggered manner by adopting an upper layer and a lower layer.

The composite concrete can be made of light aggregate concrete, fiber concrete, self-compacting concrete and other new materials.

Further, after the foundation is assembled, filling the gap between the foundation and the soil on the periphery by adopting early-strength quick-setting mortar or fine aggregate concrete; if the field condition or the construction period is limited, the resistance of the root key meets the requirement of the foundation bearing capacity through calculation, mortar or fine aggregate concrete can not be filled, and the construction is convenient and rapid.

Furthermore, root key pushing holes are reserved in the part, with the larger diameter, of the variable cross section of the circular truncated cone assembly 1, and the size of each root key pushing hole is slightly larger than that of each root key. Bolt connecting holes are reserved on two sides of a key preformed hole of the round table assembly 1.

The circular truncated cone assembly 1 is required to be provided with longitudinal stress ribs, circumferential stress ribs and horizontal stress ribs. The maximum diameter of the circular truncated cone assembly 1 is not less than 0.8 m; the height of the circular truncated cone assembly 1 should not be less than its average diameter.

The round table assembly 1 is provided with root key pushing holes which are uniformly distributed along the circumferential direction. The composite concrete can adopt new materials such as light aggregate concrete, fiber concrete, self-compacting concrete and the like.

The prefabricated root key 3 is a prefabricated reinforced concrete member, a steel reinforced concrete member or a metal member with a tip. The bottom surfaces of the root keys are required to be pre-embedded with steel plates 6, and the steel plates are symmetrically arranged on two sides of the root keys; the center of the steel plate is provided with a connecting hole.

Optionally, the prefabricated root key 3 is a prefabricated reinforced concrete member formed by pouring concrete on a steel reinforcement framework, and the steel reinforcement framework is a steel mesh structure formed by longitudinal main reinforcements and stirrups; the strength grade of concrete used for prefabricating the root key 3 is not lower than C30, and the strength of the steel bar framework is not lower than HRB 400.

As shown in fig. 6 and 7, the precast root key 3 may be a precast concrete root key, a precast steel concrete root key, or a metal root key, and only the precast concrete root key will be described here. The precast concrete root key is manufactured according to the given size, the reinforcing steel bars are arranged after the templates are supported, then the concrete is poured, and the precast concrete root key is maintained to the strength required by the design; the main reinforcement strength is not lower than HRB400, and the concrete strength grade is not lower than C30. The two sides of the bottom of the prefabricated root key 3 extend out of a part and are pre-embedded steel plates 6, and connecting holes are reserved in the centers of the pre-embedded steel plates 6.

Optionally, the prefabricated root key 3 is a section steel concrete member formed by welding section steel and reinforcing steel bars and pouring concrete, and the strength grade of the concrete is not lower than C30.

Optionally, the prefabricated root key 3 is a cross-shaped metal member formed by welding strip-shaped steel.

Further, the root keys are symmetrically and vertically distributed or are arranged on the outer side of the combined foundation in a staggered mode by adopting an upper layer and a lower layer.

Furthermore, the root keys are uniformly distributed in the assembly in the annular direction, and the number of the root keys in each assembly is not less than four.

Optionally, the mortar can adopt early-strength quick-setting mortar, and the strength is not lower than M10; or early-strength quick-setting fine aggregate concrete with the strength not lower than C30 is adopted.

The construction process of the prefabricated hollow digging foundation is as follows:

1. the first scheme is as follows: mortar and fine aggregate concrete were not applied between the outer side of the foundation and the foundation:

as shown in fig. 1, precast concrete composite member and root key; measuring and positioning according to a construction drawing, and excavating a foundation pit in undisturbed soil to a preset depth by adopting manpower or machinery; carrying out final hole inspection and cleaning holes; positioning and arranging the bottom assembly; the hole punching of the prestressed reinforcement 4 is carried out, so that the other end is ensured to be reliably installed; assembling the assemblies in sections according to requirements, and sequentially penetrating through the prestressed reinforcement 4 until the assembly at the top end is installed; applying a prestress; prefabricating the root key in advance, and jacking the prefabricated root key 3 in layers; connecting the root key and the circular truncated cone assembly 1; the residual construction soil is buried in the hollow part of the foundation.

2. Scheme II: carrying out mortar and fine aggregate concrete between the outer side surface of the foundation and the foundation:

as shown in fig. 2, precast concrete composite member and root key; measuring and positioning according to a construction drawing, and excavating a foundation pit in undisturbed soil to a preset depth by adopting manpower or machinery; carrying out final hole inspection and cleaning holes; positioning and arranging the bottom assembly; the hole punching of the prestressed reinforcement 4 is carried out, so that the other end is ensured to be reliably installed; assembling the assemblies in sections according to requirements, and sequentially penetrating through the prestressed reinforcement 4 until the assembly at the top end is installed; applying a prestress; prefabricating the root key in advance, and jacking the prefabricated root key 3 in layers; connecting the root key and the circular truncated cone assembly 1; pouring early-strength quick-setting mortar or fine aggregate concrete into the periphery of the foundation and the gaps of the prestressed reinforcements 4 to enable the early-strength quick-setting mortar or the fine aggregate concrete to be tightly combined; burying the residual construction soil into the hollow part of the foundation; and maintaining the mortar or the fine aggregate concrete to the designed strength.

The pushing method of the prefabricated root key comprises the following steps:

the inner side of the combined foundation is provided with a root key jacking equipment slideway; the root key is prefabricated on site or indoors in advance, so that the root key is used during construction;

the common prefabricated root key 3 jacking equipment comprises: the jack is suitable for jacking the prefabricated root keys 3 of the foundation with the pile diameter larger than 0.8m and not larger than 2.0m, the prefabricated root keys 3 which are symmetrically arranged in an even number are utilized in the jacking process, and two root keys are simultaneously jacked in the front and back directions, so that the construction time can be saved; the root key pushing equipment with the positioning support consists of three parts, namely a reaction frame, a jack and a conical pressing piece, and is suitable for pushing in a prefabricated root key 3 of a foundation with the diameter ranging from 2.0m to 3.0 m.

The prefabricated root key 3 positioning and pushing method comprises the following steps:

preparing various preparation works before jacking the prefabricated root key 3, if the lengths of the two opposite prefabricated root keys 3 plus the length of a jack are greater than the pile diameter, opening a hole outwards at the position of the prefabricated root key 3, reserving a length space or jacking a single root key by using the inner wall of a prefabricated concrete assembly as a counter-force support;

hoisting the prefabricated root key 3 into the pile hole by using a crane or manpower, and adjusting the line shapes among the jack, the prefabricated root key 3 and the preformed hole of the prefabricated root key 3 to enable the prefabricated root key 3, the prefabricated root key and the preformed hole to be positioned on the same axis;

and opening the jack to jack in the prefabricated root key 3. During the jacking construction process of the prefabricated root key 3, attention needs to be paid to the changes of the axes of the jack, the prefabricated root key 3 and the preformed hole, the jacking is stopped immediately after the axis deviation of the three exceeds a certain degree, and the alignment is adjusted to continue the construction.

Prefabricated root key 3 pushes away the assurance measure:

the pushing device is positioned by adopting a fixed support, so that the prefabricated root key 3 is accurately positioned;

when the prefabricated root key 3 is used for pushing, monitoring oil pressure data is noticed, and when the oil pressure is abnormal, pushing construction is stopped immediately;

when the pressure reading of the oil meter is stable and the oil quantity is not reduced any more, the prefabricated root key 3 is pushed into position.

After the foundation is combined, a scheme of carrying out mortar and fine aggregate concrete between the outer side surface of the foundation and the foundation is selected, cement paste is preferably injected from the bottom through a grouting guide pipe to fill gaps on the periphery of the foundation, and the side wall of the main structure of the foundation and the foundation soil body are reinforced.

The prefabricated expanded packing key type digging type foundation for the power transmission line can obviously save the construction period, fully play the synergistic effect of the foundation and the soil body, improve the horizontal load resistance and the overturning resistance of the foundation, reduce the construction safety risk and the engineering cost, reduce the construction waste and the environmental damage, improve the concrete quality and the foundation durability, and is beneficial to environmental protection.

Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can make modifications and equivalents to the specific embodiments of the present invention without departing from the spirit and scope of the present invention, which is set forth in the following claims.

Claims (10)

1. The utility model provides a prefabricated packing key formula of expanding for transmission line is drawn and is dug a type basis which characterized in that: comprises a concrete composite member, a prestressed reinforcement (4) and a prefabricated root key (3); the concrete assembly is a disc expanding component, and the middle part of the concrete assembly is of a hollow structure; the concrete assembly is provided with a plurality of penetrating reserved prestressed holes (7) along the height direction, and a plurality of root key reserved holes along the bottom surface direction;

the plurality of concrete assemblies are sequentially stacked in the foundation pit, and the prestressed reinforcement (4) penetrates through corresponding pre-stressed holes (7) on the plurality of concrete assemblies to assemble the concrete assemblies into a foundation main body;

the prefabricated root key (3) penetrates through the root key preformed hole and is inserted into the side wall of the foundation pit; cement paste is filled in a gap between the concrete composite member and the foundation pit; and filling and digging residual soil for foundation pit construction by the hollow structure.

2. The prefabricated expanded packing key type digging foundation for the power transmission line according to claim 1, characterized in that: the concrete assembly is one or a combination of a circular truncated cone assembly (1) and an equal-diameter assembly (2); the concrete assembly is a right circular truncated cone or an inverted circular truncated cone.

3. The prefabricated expanded packing key type digging foundation for the power transmission line according to claim 1, characterized in that: and foundation bolts (5) are embedded in the concrete assembly at the top.

4. The prefabricated expanded packing key type digging foundation for the power transmission line according to claim 1, characterized in that: the concrete composite member is prefabricated and formed by adopting light aggregate concrete, fiber concrete or self-compacting concrete, and the surface of the concrete composite member is coated with anticorrosive paint.

5. The prefabricated expanded packing key type digging foundation for the power transmission line according to claim 1, characterized in that: the hollow structure is a cylinder or a round table.

6. The prefabricated expanded packing key type digging foundation for the power transmission line according to claim 1, characterized in that: the concrete assembly height should not be less than its average diameter; the strength of the concrete assembly is not lower than C30.

7. The prefabricated expanded packing key type digging foundation for the power transmission line according to any one of claims 1 to 6, characterized in that: the prefabricated root key (3) adopts a prefabricated concrete root key, a prefabricated steel reinforced concrete root key or a metal root key; one end of the prefabricated root key (3) is a sharp part, the other end of the prefabricated root key is provided with an embedded steel plate (6), and a connecting hole is reserved in the center of the embedded steel plate (6).

8. The prefabricated expanded packing key type digging foundation for the power transmission line according to any one of claims 1 to 6, characterized in that: the prefabricated root keys (3) are annularly, symmetrically and vertically distributed or are arranged on the concrete assembly in a staggered manner by adopting an upper layer and a lower layer; the inner side of the concrete assembly is provided with a root key jacking equipment slideway.

9. The construction method of the prefabricated expanded packing key type excavation foundation for the power transmission line as claimed in any one of claims 1 to 8, characterized by comprising the following steps:

the prefabricated concrete composite member and the prefabricated root key (3);

digging a foundation pit in undisturbed soil to a preset depth; sequentially stacking, positioning and arranging the concrete composite member, and perforating the prestressed reinforcement (4) to assemble the concrete composite member into a foundation main body;

pushing the prefabricated root key (3) in a layered manner, so that the prefabricated root key (3) penetrates through the root key preformed hole and is inserted into the side wall of the foundation pit;

grouting cement slurry into the gap between the concrete assembly and the foundation pit; and burying construction residual soil into the hollow structure of the concrete assembly.

10. The construction method of the prefabricated expanded packing key type excavation foundation for the power transmission line as claimed in claim 9, wherein cement slurry is poured from the bottom of the foundation pit through a grouting guide pipe, and gaps on the periphery of the foundation are gradually filled.

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