CN103758134B - A kind of construction method combining Double-row Piles Support system - Google Patents

Abstract

A construction method for a combined double-row pile support system, the support system includes a front row of piles, a front row of pile crown beams, a rear row of piles, a rear row of pile crown beams and a connecting beam, the front row The piles are a row of reinforced concrete piles set at parallel intervals, the rear row of piles is a steel cement-soil mixing pile wall, and the connecting beam is a double-leg connecting beam; the inserted steel in the steel cement-soil mixing pile wall is H shaped steel, and the upper end of the H-shaped steel is exposed above the top crown beam of the rear row of piles; there is also a shallow reinforced cement-soil pile between the front row of piles and the rear row of piles, and the shallow reinforced cement-soil pile and the shaped steel The cement-soil mixing pile wall is integrally lapped and connected together. This support system not only overcomes the defect of adding a water-stop curtain to the ordinary double-row pile support structure in the foundation pit project that needs water interception, but also overcomes the defect of low rigidity of the steel cement-soil mixing pile wall, and realizes the soil retaining structure of the support structure. The unity with the water barrier greatly reduces the cost of the support project.

Description

A construction method of combined double-row pile support system

technical field

The invention relates to a building foundation pit support system and a construction method thereof.

Background technique

Cantilever type steel-cement-soil mixing pile wall (also known as SMW construction method) and ordinary double-row pile support structure with reinforced concrete piles in the front and rear rows are more and more support forms used in foundation pit engineering in recent years.

The cantilever-type steel cement-soil mixing pile wall is mostly used in non-hard geological conditions such as soft soil, silt, and fine sand. It is a composite soil-retaining and water-proof structure formed by inserting H-shaped steel into the cement-soil mixing pile. It has the characteristics of high water interception, economy, low construction pollution, and small impact on the surrounding environment. After the basement construction is completed, the H-shaped steel in the steel-cement-soil mixing pile wall can be pulled out, and then recycled and reused, which can not only save It also prevents the enclosure from being permanently left underground after the construction of the basement and becoming an obstacle to other subsequent underground constructions. The disadvantage of the steel-cement-soil mixing pile wall is that the main anti-lateral force element of the steel-cement-soil mixing pile wall is steel, so the rigidity is low, and the anti-side movement stiffness is insufficient, which is not conducive to controlling deformation, and for deep foundation pits, The steel-cement-soil mixing pile wall also needs to be used in combination with internal supports or anchor rods (anchor cables), which is inconvenient for construction and low in efficiency.

The ordinary double-row pile support structure is composed of a front row of reinforced concrete piles, a rear row of reinforced concrete piles, a front and rear row of pile crown beams and a connecting beam. It has the characteristics of high anti-sway rigidity, and there is no need to set inner supports or anchor cables in the pit, so it greatly facilitates the construction and shortens the construction period. The disadvantage of the ordinary double-row pile support structure is that for the foundation pit project that needs water interception, since the front and rear rows of separated reinforced concrete piles cannot form a water-stop curtain, it is necessary to set up another water-stop curtain, thus increasing the construction process and project cost .

Contents of the invention

The purpose of the present invention is to provide a construction method for a combined double-row pile support system. It is necessary to solve the problem that in the foundation pit project that needs water interception, the cost of the ordinary double-row pile support structure is too high, and the use of cantilever type steel cement soil The mixing pile wall cannot meet the safety and deformation control requirements of the foundation pit engineering.

In order to achieve the above object, the present invention adopts the following technical scheme: a combined double-row pile support system, including a front row of piles, a front row of pile crown beams, a rear row of piles, a rear row of pile crown beams and a connecting beam, It is characterized in that: the front row of piles is a row of reinforced concrete piles arranged at parallel intervals, the rear row of piles is a steel cement-soil mixing pile wall, and the connecting beam is a double-leg connecting beam; the steel cement-soil mixing pile The inserted steel in the wall is H-shaped steel, and the upper end of the H-shaped steel is exposed above the crown beam of the rear row of piles; there is also a shallow reinforced cement-soil pile between the front row of piles and the rear row of piles, and The shallow reinforcement cement-soil pile is integrally lapped and connected with the steel-cement-soil mixing pile wall.

The shallow reinforced cement-soil piles can be composed of two rows of front row shallow reinforced cement-soil piles and rear shallow reinforced cement-soil piles, and the front row shallow reinforced cement-soil piles and the rear shallow reinforced cement-soil piles are integrated Lap joints are joined together.

The pile spacing of the shallow reinforced cement-soil piles can be the same as that of the front row of piles.

The spacing of the inserted section steel in the section steel cement-soil mixing pile wall can be one time, two times or three times of the pile spacing of the front row of piles.

The upper end of the H-section steel may be provided with a section steel lifting hole.

The net distance between the two limbs of the double-leg connecting beam can be the flange width of the H-shaped steel plus 60mm.

The exposed length of the upper end of the H-shaped steel above the crown beam may be no less than 500 mm.

The main reinforcement of the front row of piles in the front row of piles can be anchored into the crown beam of the front row of piles at the top of the pile, and the anchorage length is not less than 1.5 times the tensile anchorage length.

The longitudinal main reinforcement in the connecting beam can be anchored into the top crown beam of the front row of piles and the top crown beam of the rear row of piles, and the anchorage length is not less than 1.5 times the tensile anchorage length.

A construction method using a combined double-row pile support system, characterized in that the construction steps are as follows: Step 1, according to the hydrogeological conditions of the proposed site, the geometric parameters of the foundation pit engineering, the water resistance of the foundation pit engineering, and the anti-seepage stability According to the specific requirements, calculate the various technical parameters required for the construction of a combined double-row pile support system; Step 2, according to the proposed project site conditions and surrounding environmental conditions, select a specific location, and start construction with a three-axis cement-soil mixing pile machine A section of cement-soil mixing piles in the back row of piles and a section of shallow reinforced cement-soil piles. Before the cement-soil mixing piles of the back row of piles in this section are solidified and hardened, the three-axis cement-soil mixing pile machine is shifted to construct the next section of the back row When the cement-soil mixing pile is used for the pile, the construction process of inserting the steel into the cement-soil mixing pile is started. The construction process of inserting the steel into the cement-soil mixing pile is carried out within 30 minutes after the construction of the cement-soil mixing pile at the corresponding position is completed. The exposed height of the steel It is necessary to meet the requirements for the top crown beam of the back row of piles and pull out the reserved height; step 3, repeat step 2 until the construction of all the back row of piles, interpolated steel and shallow reinforced cement soil piles is completed according to the design requirements; Step 4: Construct the front row of piles, the front row of pile crown beams, the rear row of pile crown beams and the connecting beam; Step 5, when the rear row of piles meets the anti-seepage requirements, carry out the dewatering of the foundation pit, and wait for a combined double When all parts of the pile row support system meet the strength requirements, excavation of the foundation pit earthwork is carried out; step 6, after the foundation pit is excavated to the design depth, the construction of the underground structure begins; After the gap between the pit walls is backfilled and compacted, the inserted section steel is removed, and the gap left by the inserted section steel is grouted and sealed.

Compared with the prior art, the present invention has the following characteristics and beneficial effects: the present invention is a new type of foundation pit support structure that integrates soil retaining and water-proof functions, and is especially suitable for soft soil, silt, fine sand, etc. The deep foundation pit engineering requiring water isolation under geological conditions belongs to the field of foundation foundation.

The present invention consists of the front row of reinforced concrete piles and the front row of pile crown beams located in the front row, the rear row of shaped steel cement soil mixing pile walls and the rear row of pile wall crown beams located in the rear row (i.e. the rear row of pile crown beams) ), and the double-limb connecting beams between the front and rear rows of piles, it is a space gantry type support structure system, which can bear water and soil pressure loads, has the advantage of high rigidity against lateral movement, and can effectively control the side of the foundation pit. shift deformation.

The calculation and actual measurement results of the ordinary double-row pile support structure show that the front row of piles is under compression and the rear row of piles is under tension. As the front row of piles, the H-shaped steel with good tensile performance is used as the rear row of piles, which fully exerts the performance of the material.

The invention makes full use of the advantages of both the common double-row pile support structure and the shaped steel cement-soil mixing pile wall, which overcomes the defect that the common double-row pile support structure needs to be equipped with a water-stop curtain in foundation pit projects requiring water interception, and also It overcomes the defect of low rigidity of the steel cement soil mixing pile wall.

The invention replaces the rear row of reinforced concrete piles in the ordinary double-row pile support structure with the steel-cement-soil mixing pile wall. The steel-cement-soil mixing pile wall has the functions of water stop, water isolation and seepage prevention, so it solves the problem of foundation pit engineering The water problem overcomes the defect that ordinary double-row piles need to add a water-stop curtain, and realizes the unity of soil retaining and water-proofing of the support structure, so there is no need to set up another water-stop curtain, which greatly reduces the cost of the support project and reduces the construction cost. process, saving the construction period.

The H-shaped steel in the back-row steel-cement-soil mixing pile wall in the present invention can be pulled out and recycled after the ground is constructed in the underground structure, and the gap between the structure and the foundation pit is backfilled, which greatly reduces the cost of support engineering , which saves resources and avoids causing obstacles to the subsequent construction of other adjacent underground projects.

The invention also overcomes the defect of insufficient lateral displacement rigidity of the steel cement mixing pile wall. For general deep foundation pit engineering, there is no need to set internal supports or anchor rods (anchor cables) in the pit, which greatly facilitates the excavation of earthwork in the foundation pit and underground construction. Structural construction improves construction efficiency.

In the present invention, shallow reinforcement cement soil piles (shallow reinforcement cement soil mixing piles) are arranged between the front row of reinforced concrete piles and the rear row of shaped steel cement soil mixing pile walls. This design improves the synergy between the front row of piles and the rear row of pile walls. The working stiffness also improves the strength of the soil in the active area between the front row of piles and the rear row of piles, reduces the load acting on the support structure, and is beneficial to the stress and stability of the support structure.

The present invention replaces the reinforced concrete pile formed by ordinary borehole pouring with a steel cement-soil mixing pile wall on the side (that is, the back row) near the red line of the land, which can significantly reduce the impact on the surrounding environment of the foundation pit during the borehole construction. adverse effects. Specifically, a three-axis mixing pile machine is used to cut the soil mass on site during the construction of the section steel cement-soil mixing pile wall, and the soil mass and cement slurry are fully mixed to form cement-soil, which is replaced by low-pressure continuous injection of cement slurry in a flowing state. The cement-soil in the ground maintains the balance of the total amount of underground cement-soil, so there is no need to drill holes, and there is no hole collapse phenomenon during the construction of ordinary double-row piles, so it can reduce the disturbance to the surrounding soil and reduce the damage to the surrounding pipelines and underground structures. , effectively protect the surrounding environment.

In the present invention, the steel-cement-soil mixing pile wall close to the land use red line side (i.e. the back row) is constructed first, and then the reinforced concrete piles located in the front row are constructed. An isolation curtain is formed between the environmental media, which reduces the adverse effect of soil damage induced by the reinforced concrete pile hole-forming construction on the surrounding environmental media, and effectively protects the surrounding environment.

Description of drawings

The present invention will be described in further detail below in conjunction with the accompanying drawings.

Fig. 1 is a schematic diagram of the three-dimensional arrangement of the present invention.

Fig. 2 is a schematic diagram of the mechanical calculation model of double-row pile support of the present invention.

Fig. 3 is a schematic top view of the present invention.

Fig. 4 is a schematic top view of pile arrangement of the present invention.

Reference signs: 1-front row of piles, 2-front row of pile crown beams, 3-rear row of piles, 4-interpolated steel, 5-rear row of pile crown beams, 6-connecting beams, 7- Shallow reinforced cement-soil piles, 7.1-front shallow reinforced cement-soil piles, 7.2-rear shallow reinforced cement-soil piles, 8-shaped steel lifting holes.

Detailed ways

Referring to the embodiment shown in Figures 1-4, this combined double-row pile support system includes a front row of piles 1, a front row of pile crown beams 2, a rear row of piles 3, a rear row of pile crown beams 5 and Connection beam 6.

The front row of piles 1 is a row of reinforced concrete piles arranged at parallel intervals, the rear row of piles 3 is a shaped steel cement-soil mixing pile wall, and the connecting beam 6 is a double-leg connecting beam (to facilitate the formation of the shaped steel cement-soil mixing pile wall). removal of profiled steel in the wall).

The inserted section steel 4 in the section steel cement-soil mixing pile wall is an H-section steel, and the upper end of the H-section steel is exposed above the crown beam 5 of the rear row of piles. In this embodiment, the upper end of the H-shaped steel is also provided with a steel lifting hole 8, and the exposed length of the H-shaped steel on the crown beam of the pile top is not less than 500 mm.

Between the front row of piles 1 and the back row of piles 3, there is also a shallow reinforced cement-soil pile 7, and the shallow reinforced cement-soil pile 7 is integrally connected with the steel cement-soil mixing pile wall. The shallow reinforcement cement-soil pile 7 only needs to be arranged on the upper part of the support system.

The number of rows and the overlap width of the shallow reinforced cement-soil piles 7 can be determined according to the distance between the front and rear rows of piles. In the present embodiment, the shallow reinforcement cement soil pile 7 is made up of front row shallow reinforcement cement soil pile 7.1 and rear row shallow reinforcement cement soil pile 7.2 two rows of piles, and front row shallow reinforcement cement soil pile and back row shallow Layer-reinforced cement-soil piles 7.2 are integrally lapped and connected together. Of course, in other embodiments, the shallow reinforced cement-soil piles 7 may also have only one row of piles, or three or more rows of piles.

In this embodiment, the pile spacing between the shallow reinforced cement-soil piles 7 is the same as the pile spacing between the front row of piles 1. The pile spacing can also be different.

In this embodiment, the distance between the steel sections in the steel-cement-soil mixing pile wall is twice that of the front row of piles 1, that is, the distance between the steel sections in the steel-cement-soil mixing pile wall is the same as that of the front row of piles 1. In other embodiments, the spacing of the section steel in the section steel cement-soil mixing pile wall is twice or three times the pile spacing of the front row of piles 1 .

The net distance a between the two limbs of the double-leg connecting beam is the flange width b of the H-shaped steel plus about 60mm.

The main reinforcement of the front row of piles 1 is anchored into the top crown beam 2 of the front row of piles at the top of the pile, and the anchorage length is not less than 1.5 times the tensile anchorage length.

The longitudinal main reinforcement in the connecting beam 6 is anchored into the top crown beam 2 of the front row of piles and the crown beam 5 of the rear row of piles, and the anchorage length is not less than 1.5 times the tensile anchorage length.

When the present invention calculates the strength, stability and deformation, it consists of the front row of piles 1, the front row of pile crown beams 2, the section steel 4, the back row of section steel cement soil mixing pile wall top crown beams 5, and the double limb connecting beams 6. Calculate and obtain the double-row piles, and determine the diameter, reinforcement, embedding depth and horizontal spacing of the front row of piles according to the design requirements, as well as the type of steel in the steel-cement-soil mixing pile wall, and the double-leg continuous beam. Section size, concrete grade and reinforcement.

The length of the cement-soil pile in the section steel cement-soil mixing pile wall is determined by the length of the section steel and the foundation pit water stop and anti-seepage (the larger value determined by the section steel length and the foundation pit water stop and anti-seepage requirements), the section steel The pile body strength of the cement-soil pile in the cement-soil mixing pile wall must meet the requirements of water stop and strength calculation.

This construction method using a combined double-row pile support system has the following construction steps.

Step 1. According to the hydrogeological conditions of the proposed site, the geometric parameters of the foundation pit engineering, the water insulation and anti-seepage stability requirements of the foundation pit engineering, calculate the various technical parameters required for the construction of a combined double-row pile support system. Specifically, according to the hydrogeological conditions of the proposed site and the geometric parameters of the foundation pit engineering, the strength of the support structure, the stability of the support system and the deformation calculation are carried out to determine the diameter, concrete strength grade and section configuration of the front row of piles 1. Reinforcement, embedding depth and horizontal spacing, etc., type and length of section steel 4, section size of connecting beam 6, concrete grade and reinforcement, etc. Then, the length of the rear row of piles 3 is determined according to the water-resistance and anti-seepage stability requirements of the foundation pit engineering and the calculated length of the section steel 4. The pile body strength of the rear row of piles 3 should meet the calculation requirements, and the permeability coefficient should meet the water stop requirements.

Step 2. Select a specific location according to the site conditions of the project to be built and the surrounding environmental conditions, and use a three-axis cement-soil mixing pile machine to start construction of a section of cement-soil mixing piles for the rear row of piles 3 and a section of shallow reinforced cement-soil piles 7. Before the cement-soil mixing pile of the rear row of piles 3 that has been constructed is solidified and hardened, when the three-axis cement-soil mixing pile machine is shifted to construct the cement-soil mixing pile of the next rear row of piles 3, the interpolated steel 4 is inserted into the cement-soil mixing pile The construction process, the construction process of inserting section steel 4 into the cement-soil mixing pile shall be carried out within 30 minutes after the construction of the cement-soil mixing pile at the corresponding position is completed. Stay height required.

Step 3: Step 2 is repeated continuously until all rear row piles 3, interpolated section steel 4 and shallow reinforced cement-soil piles 7 are completed according to the design requirements.

Step 4, construct the front row of piles 1, the front row of pile crown beams 2, the back row of pile crown beams 5 and the connecting beam 6. Specifically, while constructing the front row of piles 1 (the reserved length of the main reinforcement of the pile top of the front row of piles 1 needs to meet the anchorage requirements), at the same time as the construction of the front row of piles, the crown beam 2 of the row of piles and the pile top of the rear row of piles are carried out step by step. The construction of crown beam 5 and connecting beam 6, the construction process of row pile top crown beam 2, back row pile top crown beam 5 and connection beam 6 is to bind the reinforcing bar of front row pile top crown beam earlier, and then The steel bars of the top crown beam of the row piles and the steel bars of the connecting beam are then poured into concrete as a whole.

Step 5: When the rear row of piles 3 meets the anti-seepage requirements, the foundation pit engineering dewatering is carried out, and when all parts of a combined double-row pile support system meet the strength requirements, the foundation pit excavation is carried out.

Step 6: After the foundation pit is excavated to the design depth, the underground structure construction starts.

Step 7: After the construction of the underground structure, the floor is removed, and the gap between the structure and the wall of the foundation pit is backfilled and compacted, and the inserted steel is removed (that is, the steel in the steel cement-soil mixing pile wall is recycled after use), and the inserted steel Fill the gap left by grouting.

The content described in the embodiments of this specification is only an enumeration of the implementation forms of the present invention, and the protection scope of the present invention should not be regarded as limited to the specific forms stated in the embodiments. Equivalent technical means that a person can think of based on the concept of the present invention.

Claims (9)

1. A construction method for a combined double-row pile support system, wherein the combined double-row pile support system includes a front row of piles (1), a front row of pile crown beams (2), a rear row of piles (3), The rear row of pile crown beams (5) and connecting beams (6), the front row of piles (1) are a row of reinforced concrete piles arranged in parallel intervals, and the rear row of piles (3) are shaped steel cement soil mixing In the pile wall, the connecting beam (6) is a double-leg connecting beam; the inserted section steel (4) in the section steel cement-soil mixing pile wall is H-shaped steel, and the upper end of the H-shaped steel is exposed on the back row of piles The top of the crown beam (5); between the front row of piles (1) and the rear row of piles (3), there is also a shallow reinforced cement-soil pile (7), and the shallow reinforced cement-soil pile (7) and The steel-cement-soil mixing pile wall is integrally lapped and connected together, which is characterized in that the construction steps are as follows: Step 1. According to the hydrogeological conditions of the proposed site, the geometric parameters of the foundation pit engineering, the water insulation of the foundation pit engineering, and the anti-seepage stability requirements, calculate the various technical parameters required for the construction of a combined double-row pile support system; Step 2. According to the site conditions of the proposed project and the surrounding environmental conditions, select a specific location, and use a three-axis cement-soil mixing pile machine to start construction of a section of cement-soil mixing piles for the rear row of piles (3) and a section of shallow reinforced cement-soil piles (7 ), before the cement-soil mixing piles of the rear row of piles (3) that have been constructed in this section are solidified and hardened, and when the three-axis cement-soil mixing pile machine is shifted to construct the cement-soil mixing piles of the next row of piles (3), the internal The construction process of inserting steel (4) into the cement-soil mixing pile, and the construction process of inserting the steel (4) into the cement-soil mixing pile shall be carried out within 30 minutes after the construction of the cement-soil mixing pile at the corresponding position. Requirements for the top crown beam (5) of the rear row of piles and the reserved height for pulling out; Step 3: Repeat Step 2 continuously until all the rear row of piles (3), interpolated section steel (4) and shallow reinforced cement-soil piles (7) are completed according to the design requirements; Step 4, constructing the front row of piles (1), the front row of pile crown beams (2), the back row of pile crown beams (5) and the connecting beams (6); Step 5. When the rear row of piles (3) meets the anti-seepage requirements, carry out the dewatering of the foundation pit engineering, and when all parts of a combined double-row pile support system meet the strength requirements, carry out the excavation of the foundation pit; Step 6: After the foundation pit is excavated to the design depth, the construction of the underground structure begins; Step 7: After the construction of the underground structure, the floor is removed, the gap between the structure and the wall of the foundation pit is backfilled and compacted, and the inserted section steel is removed, and the gap left by the inserted section steel is grouted and sealed. 2. The construction method of a combined double-row pile support system according to claim 1, characterized in that: the shallow reinforced cement-soil pile (7) consists of the front row of shallow reinforced cement-soil piles (7.1) and The back row of shallow reinforced cement soil piles (7.2) consists of two rows of piles, and the front row of shallow reinforced cement soil piles and the rear row of shallow reinforced cement soil piles (7.2) are integrally connected together. 3. The construction method of a combined double-row pile support system according to claim 1, characterized in that: the pile spacing of the shallow reinforced cement-soil piles (7) and the pile spacing of the front row of piles (1) same. 4. The construction method of a combined double-row pile support system according to claim 1, characterized in that: the distance between the interpolated steel (4) in the steel-cement-soil mixing pile wall is the same as that of the front row of piles (1 ) is one, two or three times the pile spacing. 5. The construction method of a combined double-row pile support system according to claim 1, characterized in that: the upper end of the H-shaped steel is provided with a steel lifting hole (8). 6. The construction method of a combined double-row pile support system according to claim 1, characterized in that: the clear distance (a) between the two limbs of the double-leg connecting beam is the flange of H-shaped steel Width (b) plus 60mm. 7. The construction method of a combined double-row pile support system according to claim 1, characterized in that: the exposed length of the upper end of the H-shaped steel above the crown beam is not less than 500mm. 8. The construction method of a combined double-row pile support system according to claim 1, characterized in that: the main reinforcement of the front row of piles in the front row of piles (1) is anchored into the front row of piles at the top of the pile In the crown beam (2), and the anchorage length is not less than 1.5 times the tensile anchorage length. 9. The construction method of a combined double-row pile support system according to claim 1, characterized in that: the longitudinal main reinforcement in the connecting beam (6) is anchored into the top crown beam (2 ) and the top crown beam (5) of the rear row of piles, and the anchorage length is not less than 1.5 times the tensile anchorage length.