CN102330430A - Construction method for prefabricated building enclosure of deep foundation pit in low-temperature environment construction - Google Patents

Abstract

The present invention relates to the construction of the enclosure structure used for deep foundation pits, and in particular to a construction method for the prefabricated enclosure structure of deep foundation pits used in low temperature environment construction. The construction method adopts the following steps: firstly, the prefabricated enclosure structure Pile sections, followed by completion of the pile hole forming according to the design requirements, and then hoisting the enclosure pile sections section by section and connecting them on site to form a prefabricated enclosure pile retaining wall; after that, excavate the foundation pit and complete the prefabricated enclosure pile retaining wall at the same time The internal structure construction of the lateral support between the walls constitutes the prefabricated enclosure structure of the deep foundation pit. The advantage of the present invention is that: the foundation pit enclosure structure adopts factory prefabricated parts, which can avoid on-site binding of steel bars, pouring and curing of concrete under negative temperature conditions, which not only saves the cost of construction measures in winter, but also improves the working environment and work efficiency , shorten the on-site construction period, and at the same time ensure the quality of concrete pouring of the enclosure structure.

Description

Construction method of deep foundation pit prefabricated enclosure structure for construction in low temperature environment

the

technical field

The invention relates to the construction of an enclosure structure for deep foundation pits, in particular to a construction method for a prefabricated enclosure structure for deep foundation pits used for construction in a low-temperature environment.

Background technique

In the prior art, the types of enclosure structures and construction methods commonly used for deep foundation pits mainly include the following types:

1. For the underground diaphragm wall, use special trenching equipment to excavate a deep groove under the mud retaining wall, then hoist the steel cage and pour concrete to form a concrete wall underground. The advantages of the underground diaphragm wall as an enclosure structure are: high rigidity, good integrity, small deformation, water-retaining and anti-seepage effects, no precipitation outside the pit, and little impact on the surrounding environment. The disadvantages are: mud wall protection is required during construction, and the mud treatment is complicated; a large site is required, which has a certain impact on the environment; and the cost of the underground diaphragm wall is relatively high. In severe cold areas, this technology is generally not used because of the high cost of winter construction such as mud preparation, excavation into trenches, steel cage hoisting, concrete transportation and pouring.

2. Column-type bored piles, cast-in-place piles have a wide range of application to the stratum. According to the hydrogeological conditions of the project, construction methods such as mud wall drilling, impact drilling, long spiral drilling, and dry operation can be used. Cast-in-situ piles are easy to construct, do not require large machinery, occupy less land, have less environmental pollution, and have lower construction costs. The reinforced mesh sprayed concrete is used to protect the soil between the bored piles, and the water blocking ability is weak. In the section where the groundwater level is higher than the bottom of the excavation pit and where precipitation cannot occur, another water-stop curtain must be installed, and the cost is relatively high. In severe cold areas, due to the small height of construction machines and tools of cast-in-place piles and the small occupied space, greenhouses can be built to insulate construction machines, mud pools, building materials, and concrete maintenance. The construction cost is high, the working environment is poor, and the construction quality is uneven.

3. Drilled occlusal piles, which are row piles arranged in a plane, and adjacent single piles are occluded with each other (the piles are circumferentially embedded) to form a reinforced concrete "pile wall" that can retain soil and water. Drilled occlusal piles have strong geological adaptability, and are especially suitable for adverse geological conditions such as silt, quicksand, and abundant groundwater. The occlusal pile does not require mud wall protection, which saves the cost of mud production, use, and waste slurry treatment. The occlusal pile is a novel technology of the enveloping structure. Under the same conditions, it has incomparable advantages compared with other supporting structures. In the severe winter area, it is not necessary to set up mud pools and thermal insulation measures, which reduces the cost of the project, but it still needs to bind the steel bars, Concrete curing and other processes take winter measures.

To sum up, the currently commonly used deep foundation pit enclosure structures mainly include underground diaphragm walls, column-type bored piles, and bored occlusal piles. Although the construction techniques are different, the pile (wall) body is mainly made of cast-in-place concrete. In special environments such as severe cold regions or low-temperature environments, in-situ cast-in-place reinforced concrete enclosure structures for foundation pits are constructed in winter, and the environmental conditions for on-site steel bar binding, concrete pouring, and maintenance processes are harsh. In order to ensure the minimum temperature requirements for concrete maintenance, it is necessary to Take winter measures such as building greenhouses, heating building materials, and concrete insulation and maintenance. The project cost is high, the construction speed is slow, and the construction quality is relatively poor.

Contents of the invention

The purpose of the present invention is to provide a construction method for deep foundation pit prefabricated enclosure structure for construction in low temperature environment according to the deficiencies of the above-mentioned prior art. The prefabricated enclosure structure of the prefabricated foundation pit, after being transported to the construction site, is hoisted, connected, and erected in place, and immediately plays the role of the enclosure structure. Avoid the deficiency of concrete pouring and maintenance on site in the prior art.

The object of the present invention is realized by the following technical solutions:

A construction method for a prefabricated enclosure structure of a deep foundation pit for construction in a low-temperature environment, characterized in that the construction method adopts the following steps: firstly prefabricating the pile joints of the enclosure piles, and secondly completing the pile hole forming according to the design requirements, Then the retaining pile sections are hoisted section by section and connected into a whole on site to form the prefabricated retaining pile retaining wall; after that, the foundation pit is excavated, and the internal structure construction of the lateral support between the prefabricated retaining pile retaining walls is completed at the same time, thus forming the prefabricated retaining pile retaining wall Describe the prefabricated enclosure structure of deep foundation pit.

The construction of the prefabricated retaining piles sequentially includes on-site hoisting, pile segment connection, and grouting around the piles.

The pile sections of the prefabricated enclosure piles include head piles, foot piles and pile body piles, and the on-site hoisting refers to hoisting the head piles, at least one section of pile body piles and foot piles into the holes in sequence on site , the pile segment connection is performed at the same time.

The pile segment connection refers to the combined installation of adjacent pile segments hoisted into the hole to form a prefabricated enclosure pile.

The grouting around the pile refers to the fact that the prefabricated retaining piles have been hoisted on site and the pile segments are connected. After all the prefabricated retaining piles are hoisted in place, the grouting around the piles is performed to fill the prefabricated piles and piles. The gap between the surrounding soil is grouted through the grouting pipe pre-buried in the pile body.

The construction of the internal structure refers to the construction of horizontal steel supports between the prefabricated retaining pile retaining walls from top to bottom along with the excavation process of the foundation pit; After that, the middle plate structure, roof structure and side wall structure are constructed sequentially from bottom to top, and at the same time, after each structure reaches the design strength, the steel supports are removed in turn; finally, the foundation pit is backfilled to restore the road condition on the ground.

A steel purlin is fixedly installed on the surface of the retaining wall of the prefabricated retaining pile, and the steel purlin is arranged perpendicular to the retaining wall of the prefabricated retaining pile.

The transverse steel supports are fixed on the steel purlins.

The lateral supports include but not only steel supports, but also various internal and external support systems such as reinforced concrete supports and anchor cables.

The advantage of the present invention is that: the foundation pit enclosure structure adopts factory prefabricated parts, which can avoid on-site binding of steel bars, pouring and curing of concrete under negative temperature conditions, which not only saves the cost of construction measures in winter, but also improves the working environment and work efficiency , shorten the on-site construction period, and at the same time ensure the quality of concrete pouring of the enclosure structure. By adopting the prefabricated enclosure structure, foundation pit enclosure construction can also be carried out under extremely low temperature conditions of -15°C and below, realizing production without winter breaks throughout the year in severe cold areas, extending the construction period by two to three months, and achieving good and efficient construction. Fast engineering construction goals. In addition to severe cold areas, prefabricated enclosure structures can also be used when the construction period is short, which can realize the simultaneous process of factory prefabrication of enclosure structures and on-site hole (slot) formation, reduce concrete curing time, and speed up construction. The cost is relatively high.

Description of drawings

Fig. 1 is a schematic diagram of plane layout of deep foundation pit enclosure structure of the present invention;

Fig. 2 is a schematic cross-sectional view of a deep foundation pit enclosure structure of the present invention;

Fig. 3 is a schematic diagram of step 1 of the construction method of the present invention;

Fig. 4 is the second schematic diagram of the construction method of the present invention;

Fig. 5 is a schematic diagram of step three of the construction method of the present invention;

Fig. 6 is a schematic diagram of step four of the construction method of the present invention;

Fig. 7 is a schematic diagram of Step 5 of the construction method of the present invention;

Fig. 8 is a schematic diagram of Step 6 of the construction method of the present invention.

Detailed ways

The features of the present invention and other related features will be further described in detail below in conjunction with the accompanying drawings through embodiments, so as to facilitate the understanding of those skilled in the art:

As shown in Figure 1-8, the labels 1-18 respectively represent: prefabricated retaining pile retaining wall 1, steel support 2 (2.1, 2.2, 2.3), steel purlin 3, head pile 4, pile joint head 5, pile Body pile 6, foot pile 7, road surface 8, concrete retaining wall 9, crown beam 10, ground design elevation 11, top plate 12, middle plate 13, side wall 14, bottom plate 15, bottom plate structure waterproof layer 16, bottom plate cushion 17, Prefabricated retaining piles 18.

The following embodiment relates to a construction method of a prefabricated enclosure structure for deep foundation pits suitable for construction in severe cold regions or low-temperature environments. The structural form of the enclosure structure is mainly prefabricated piles, and the cross-sectional form can be square, circular, etc. shape. The construction of prefabricated enclosure structures for deep foundation pits mainly includes pile hole forming, pile joint prefabrication, on-site hoisting, segment connection, prestressed tensioning, and grouting around piles.

In order to reduce the requirements on prefabricated molds, transportation and hoisting capabilities, the prefabricated enclosure structure is mainly prefabricated piles, which are prefabricated in sections.

According to the hydrogeological conditions of the project, there are two types of hole forming at pile positions: mud retaining wall hole forming and dry method hole forming. In severe cold regions, prefabricated enclosure structures are more suitable for dry hole-forming projects, such as manual digging, long auger drilling, rotary drilling and other construction methods, which can avoid setting up large-scale mud pools and reduce winter construction costs and construction difficulties.

The pile section prefabrication can be completed in the component processing factory, and according to the design requirements for the material grade of the enclosure structure, pile diameter, steel cage style, etc., factory prefabrication is carried out in the workshop. The prefabrication process includes building material preparation, steel cage binding, mold entry, maintenance, demoulding, test and inspection and other processes. In order to avoid many types of molds and increase the cost of production equipment, the length of the pile section can establish a standardized modulus, such as 4, 6, 8m and other standard lengths; the nature of the pile section can also be divided into types such as head pile 4, pile body pile, and foot pile 8 , The pile body pile adopts standard joints, and the length of the head pile 4 or the foot pile 8 is adjusted to adapt to the design pile length.

After the prefabricated pile sections are manufactured, they are transported to the construction site, and the pile section combination is determined according to the design pile length. For each prefabricated enclosure pile, one section is selected for the head pile 4 and the foot pile 8, and the pile body depends on the engineering design. As required by the elevation, multiple sections can be installed, hoisted into the borehole in sections, and connected while hoisting until the design elevation. The connection of pile joints can be divided into flange connection, welding connection, mechanical meshing connection and other methods according to the form of the national building standard design atlas "Prestressed Concrete Pipe Pile" (10G409). However, because the force of the prefabricated enclosure structure in this embodiment is mainly bending and shearing, and the force is very large, the pile joint connection must ensure the integrity of the pile body.

For large-diameter (≥800mm) prefabricated enclosure structures, the load on the pile body is large, and post-tensioned prestressed steel bars can be arranged in the pile body to improve the force-bearing capacity of the pile body and enhance the integrity of the pile body.

In order to reduce the lifting weight of the pile, the prefabricated pile can adopt a hollow cylinder structure. At the same time, in order to strengthen the integrity of the prefabricated pile, in addition to the above-mentioned connection methods such as flanges, welding, and mechanical meshing, it can also be inserted into the hollow part of the pile body and poured. Low grade concrete for overall rigidity.

After all the pile sections are hoisted in place, grouting around the pile is required to fill the gap between the prefabricated pile and the soil around the pile and prevent excessive settlement of the ground surface. The grouting can be carried out through the grouting pipe pre-buried in the pile body.

The construction steps of this embodiment are as follows:

Step 1: Excavate a shallow foundation pit, construct a concrete retaining wall 9 , construct a prefabricated retaining pile retaining wall 1 and a crown beam 10 . Wherein the prefabricated enclosure pile 18 constituting the prefabricated enclosure pile retaining wall 1 is composed of head pile 4, pile body pile 6, and foot pile 7 sequentially assembled and connected, wherein each prefabricated enclosure pile 1 has a head pile 4, a Section foot pile 7 has pile body pile 6 some, and the quantity of pile body pile 6 depends on the concrete requirement of foundation pit depth. The connection method can choose the welding connection method.

Step 2: Continue to excavate until the design elevation of the bottom of the foundation pit. With the excavation, steel support 2 is sequentially installed from top to bottom, that is, 2.1, 2.2, and 2.3 are applied in sequence. The support of steel support 2 is fixed vertically on the The steel purlins 3 on the surface of the prefabricated retaining pile retaining wall 1 are fixedly connected. The way of fixed connection usually chooses bolt connection, or flange, supporting plate and other connection methods. In this embodiment, a total of three steel supports 2.1, 2.2, and 2.3 are implemented, which are usually excavated in the foundation pit to the steel support axis. At the distance of 0.5m, steel support 2 shall be applied.

The third step: laying the floor quick concrete cushion 17, laying the waterproof layer 16, constructing the structural floor 15 and part of the side wall 14 between the structural floor 15 and the third steel support 2.3.

Step 4: After the structural bottom plate 15 reaches the design strength, remove the third steel support 2.3, lay the waterproof layer of the side wall 14, and construct the part of the side wall 14 and the structural middle plate between the structural bottom plate 15 and the structural middle plate 13 13.

Step 5: After the side wall 14 and the structural middle plate 13 reach the design strength, remove the second steel support 2.2, lay the side wall waterproof layer, and construct the side wall 14 between the structural middle plate 13 and the structural roof 12 and Structural roof 12.

Step 6: After the side walls 14 and the structural roof 12 reach the design strength, remove the first steel support 2.1, lay the roof waterproof layer, backfill the foundation pit, restore the road surface 8, and finally construct the building structure above the foundation pit.

Claims (9)

1. A construction method for a deep foundation pit prefabricated enclosure structure for low-temperature environment construction, characterized in that, said construction method adopts the following steps: firstly prefabricating the pile joints of enclosure piles, and secondly completing pile position formation according to design requirements hole, then hoist the retaining pile sections section by section and connect them on site to form a prefabricated retaining pile retaining wall; then excavate the foundation pit, and complete the internal structure construction of the lateral support between the prefabricated retaining pile retaining walls at the same time. Constitute the prefabricated enclosure structure of the deep foundation pit. 2. a kind of construction method for the deep foundation pit prefabricated enclosure structure that is used for construction in low temperature environment according to claim 1, it is characterized in that described applying prefabricated enclosure pile successively comprises factory prefabrication, on-site hoisting, pile Segmental connection, grouting around the pile. 3. The construction method of a deep foundation pit prefabricated enclosure structure for low-temperature environment construction according to claim 2, wherein the pile sections of the prefabricated enclosure piles include head piles, foot piles and pile bodies pile, the on-site hoisting refers to the on-site hoisting of the head pile, at least one pile body pile and foot pile into the hole in sequence, and the pile segment connection is carried out at the same time. 4. The construction method of a deep foundation pit prefabricated enclosure structure for low temperature environment construction according to claim 2 or 3, characterized in that the pile segment connection refers to the adjacent piles that will be hoisted into the hole The combined installation of sections constitutes a prefabricated enclosure pile. 5. The construction method of a deep foundation pit prefabricated enclosure structure for construction in low temperature environment according to claim 2, characterized in that the grouting around the pile refers to the completion of the prefabricated enclosure pile On-site hoisting and pile segment connection, after all the prefabricated retaining piles are hoisted in place, grouting around the pile is performed to fill the gap between the prefabricated pile and the soil around the pile, and the grouting passes through the grouting pipe pre-buried in the pile body conduct. 6. the construction method of a kind of deep foundation pit prefabricated enclosure structure that is used for construction in low temperature environment according to claim 1, is characterized in that, described internal structure construction refers to with foundation pit excavation process, from top to bottom Lateral supports are constructed between the retaining walls of the prefabricated retaining piles in turn; after excavation to the ground floor, the floor structure and part of the side walls are constructed; then the middle plate structure, roof structure and side wall structures are constructed sequentially from bottom to top, and at the same time After each structure reaches the design strength, the steel supports are removed in sequence; finally, the foundation pit is backfilled to restore the road conditions on the ground. 7. the construction method of a kind of deep foundation pit prefabricated enclosure structure that is used for construction in low temperature environment according to claim 6, is characterized in that, steel enclosure purlin is fixedly installed on the surface of described prefabricated enclosure pile retaining wall, so The steel purlins are set perpendicular to the retaining wall of the prefabricated retaining piles. 8. A construction method for a prefabricated enclosure structure of a deep foundation pit for construction in a low-temperature environment according to claim 6, wherein the lateral support is fixed on the steel purlin. 9. The construction method of a deep foundation pit prefabricated enclosure structure for construction in a low temperature environment according to claim 6, wherein the lateral support is a steel support, or a reinforced concrete support, or an anchor search.

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