CN204326119U - A kind of pile-raft foundation float Structure - Google Patents

Abstract

The utility model relates to a pile-raft foundation anti-floating structure, in which the side wall of the basement is connected with the supporting piles through horizontal connecting steel bars; bored piles are drilled under the basement floor; gravel pads are arranged under the basement floor from top to bottom. layer, backfill lime soil layer, reinforced concrete water-repelling board, weak soil layer, and relative bearing layer; the position of the reinforced concrete water-repelling board is close to the bottom of the water-stop curtain, and a closed waterproof space is formed between the reinforced concrete water-baffle board and the water-stop curtain The reinforced concrete water baffle and the support pile are connected by connecting steel bars, and the reinforced concrete water baffle is arranged with holes at intervals, and anti-floating anchor rods are interspersed through the holes in the relative bearing layer. The structure involved in the utility model has good load-bearing and anti-floating performance, little damage to the joints of the raft and the pile-raft, the bottom plate is not easy to leak, the construction speed is fast, the cost is low, and the technical and economic benefits are good.

Description

Anti-floating structure of piled raft foundation

technical field

The utility model relates to an anti-floating structure and a construction method of a pile raft foundation, which has fast construction, low cost and anti-floating ability, and belongs to the field of construction engineering.

Background technique

For the purpose of expanding the use of functions and developing underground space, high-rise buildings are generally designed with basements with larger plan dimensions and depths. However, in the coastal cities where the underground soil is rich in water, the buoyancy of the groundwater causes the superstructures such as buildings and structures to tilt and collapse frequently, which makes the problem of anti-floating of the basement increasingly prominent.

Pile-raft foundation is an organic combination of pile foundation and raft foundation, and has the characteristics of both pile foundation and raft foundation: large overall rigidity, high bearing capacity, strong deformation resistance, and good seismic performance, which can effectively avoid uneven settlement of the structure , has been widely used in high-rise or super high-rise buildings, and can also be used in foundation treatment projects of airport ports and large logistics yards.

There are three commonly used anti-floating measures for existing large-scale piled raft structures: one is ballast anti-floating technology, that is, adding counterweight to the basement floor or increasing the thickness of the floor to offset the buoyancy of groundwater on the raft, increasing the thickness of the floor The anti-floating of underground structures is very effective, but the buried depth of the foundation will inevitably increase, and the buoyancy of groundwater will also increase accordingly. Therefore, the anti-floating design is more difficult, and the construction effect is difficult to meet the design requirements; Its own tensile strength pulls the basement structure as a whole and the rock layer or hard soil layer. Under the raft foundation, uplift anchors are usually arranged all over the house, so the use of uplift anchors is large, which is easy to cause waste of building materials; because of long-term contact with groundwater , so the anti-corrosion requirements of the anti-uplift anchor are very high, and the anti-uplift anchor cannot bear the downward load; the third is the anti-floating pile technology, the anti-floating pile uses the pile body's own weight and pile side friction to provide anti-buoyancy, because the pile Connected with the column, the distance between the anti-floating piles is too large, and a thick bottom plate is needed to resist the additional bending moment and shear force generated by the buoyancy. Therefore, the cost of the pile is high and the cost of the bottom plate is also high.

To sum up, although the existing pile-raft foundation anti-floating structure has achieved remarkable results in anti-floating performance and anti-seepage performance, and has reduced the damage caused by the continuous change of groundwater level to the basement side wall and floor, there are still some problems. The areas that can be improved are mainly reflected in the relatively high construction difficulty and high construction cost. In areas with a high groundwater level, as the depth of the basement increases, higher requirements are put forward for the anti-floating and anti-seepage of pile foundations and rafts.

In view of this, there is an urgent need to invent a pile-raft foundation anti-floating structure with reliable construction quality, fast construction speed and relatively low cost.

Utility model content

The purpose of the utility model is to provide a pile-raft foundation anti-floating structure and construction method with good load-bearing and anti-floating performance, which can effectively reduce the damage to the connection between piles and raft slabs caused by groundwater level changes.

In order to achieve the above-mentioned technical purpose, the utility model adopts the following technical solutions:

An anti-floating structure of a piled raft foundation, the side wall of the basement and the support pile are connected by horizontal connecting steel bars; bored piles are drilled under the basement floor; the gap between the side wall of the basement and the basement floor is filled with self-compacting waterproof concrete ;

Below the basement floor, from top to bottom, there are crushed stone cushion, backfill lime soil layer, reinforced concrete water barrier, weak soil layer, and relative bearing layer;

The reinforced concrete baffle is more than 1m higher than the lower end of the water-stop curtain, and a closed waterproof space is formed between the reinforced concrete baffle and the water-stop curtain;

Reinforced concrete baffles and support piles are connected by connecting steel bars, and active material water barriers are set at the joints between reinforced concrete baffles and support piles;

Holes are arranged at intervals on the concrete water baffle, and anti-floating anchor rods are inserted through the holes to the relative bearing layer. Water-swelling water-stop strips are arranged at the connection between the reinforced concrete water baffle and the bored pile.

The connecting steel bars connecting the side walls of the basement and the supporting piles are arranged at equal intervals along the supporting piles, and the connecting steel bars are welded to the reinforcing bars in the side walls of the basement;

The thickness of the crushed stone cushion is 300~500mm. A water level detector and a drainage pipe are pre-buried in the crushed stone cushion. One end of the drainage pipe extends to the sump.

The utility model has the following characteristics and beneficial effects:

(1) The anti-floating structure of the piled raft foundation shall be provided with continuous reinforced concrete water barriers, and the reinforced concrete water barriers shall be poured within the layout range of the water-stop curtain to form a closed water barrier to prevent groundwater below the reinforced concrete water barriers from entering the backfill In the lime soil layer, the impact of groundwater level changes on pile rafts is reduced.

(2) Backfilling the lime soil layer enables the building to settle evenly, resists the buoyancy of groundwater, greatly reduces the use of anti-floating anchors, and saves construction costs.

(3) A layer of crushed stone cushion is set on the top of the basement floor, and drainage pipes and water level detectors are installed in the crushed stone cushion. When the groundwater level leaks, it is easy to be found, and drainage measures can be taken in time.

(4) A rubber waterstop is installed at the connection between the bored pile and the reinforced concrete water barrier, and the rubber waterstop expands when exposed to water to prevent groundwater from rising and leaking from the junction gap to the backfill lime soil layer.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of the anti-floating structure of the piled raft foundation of the present invention;

In the figure: 1. Weak soil layer; 2. Supporting pile; 3. Water-stop curtain; 4. Bored pile; 5. Reinforced concrete water barrier; 6. Rubber waterstop; 7. Anti-floating anchor rod; 8. Lime soil layer; 9. Gravel cushion; 10. Drainage pipe; 11. Connecting steel bar; 12. Basement side wall; 13. Basement floor; 14. Self-compacting waterproof concrete; 15. Active material water-proof body; 16. Relative Bearing layer; 17. Bolt grouting body.

Detailed ways

In this embodiment, the construction technology of support piles and bored cast-in-place piles, the construction of leading holes for connecting steel bars, the construction technology of anti-floating anchor rods, the construction technology of reinforced concrete water barriers and the pouring construction technology of basement bottom slabs will not be included in this embodiment. Recite, emphatically set forth the embodiment that the utility model relates to structure.

Fig. 1 is the schematic diagram of the anti-floating structure of the pile cutting foundation of the present invention. With reference to shown in Fig. 1, the anti-floating structure of the piling foundation of the utility model is mainly composed of a water-stop curtain 3, a support pile 2, a reinforced concrete water barrier 5, a bored pile 4, a crushed stone cushion 9 and an anti-floating anchor rod. 7 composition.

Set up a row of supporting piles 2 around the foundation pit. The supporting piles 2 are deep mixing piles with a pile diameter of 600mm, a pile spacing of 450mm, and a pile length of 9m. 3 Continuous cement mixing piles are adopted, the pile diameter is 250mm, the pile top is 3.5m away from the ground surface, and the bottom of the pile is located below the groundwater level.

The bored cast-in-place pile 4 is circular, the diameter of the pile body is 600mm, and the distance between the piles is 3m. The pile body passes through the soft soil layer 1 and extends into the relative bearing layer 16 for more than 1m; 500mm, set 12 Ф16mm, strength grade HRB335 longitudinal threaded steel bars, spiral stirrups use Ф8mm, strength grade HPB300 smooth steel bars. The concrete strength grade of the bored pile 4 is C35, and 42.5# ordinary Portland cement is used. The construction of bored pile 4 meets the requirements of "Technical Specifications for Building Pile Foundations" (JGJ94-2008).

Reinforced concrete water baffle 5 is poured with anti-seepage concrete. The cement is ordinary Portland cement with a strength of not less than 32.5Mpa. The 7-day hydration heat index of the cement is not higher than 275kJ/kg. Early-strength cement and cement are not allowed. The alkali content of the cement must meet the total alkali content of cement per cubic meter of concrete is not more than 2.25kg, the grade of the added fly ash is not lower than grade II, high calcium fly ash is not allowed, and the coarse aggregate is 5~31.5mm grade Mix uniform crushed stone, the mud content shall not be greater than 1%, the fine aggregate shall be medium-coarse sand, and the fineness modulus shall be 2.5~3.0. The mud content of the sand shall not exceed 3%. The admixture is added to the concrete, and the admixture should be admixture with low alkali and low heat of hydration, and the admixture should not exceed 5% of the cement mass.

Reinforced concrete water barrier 5 and support pile 2 are arranged perpendicular to each other, and the two are connected by connecting steel bar 11. The connecting steel bar 11 adopts the aperture of steel bar planting bar to be 20mm, and the active material water barrier 15 of outsourcing geotechnical cloth bag is laid at the joint, and the active material The material water barrier 15 is a polymer resin active waterproof material. The bored cast-in-place pile 4 runs through the reinforced concrete water barrier 5, and a rubber waterstop 6 is set between the reinforced concrete water barrier 5 and the bored cast-in-place pile 4. Strength ≥ 3.5Mpa.

After the reinforced concrete water baffle 5 reaches a certain strength, drill a hole on the reinforced concrete water baffle 5, and install an anti-floating anchor rod 7 in the hole. Processing, the anti-floating anchor 7 is grouted to form an anchor grouting body 17 .

After the installation of the anti-floating anchor 7 is completed, the lime soil layer 8 is backfilled on the reinforced concrete water barrier 5, and the crushed stone cushion layer 9 is arranged on the top of the lime soil layer 8. 20mm. A water level sensor is arranged in the gravel cushion 9, and a drain pipe 10 is pre-buried, and the drain pipe 10 adopts a concrete pipe with an inner diameter of 100-200mm.

Carry out the construction of basement bottom plate 13 and basement side wall 12 then, the reinforcing bar of basement bottom plate 13 and basement side wall 12 adopts diameter to be 16mm, strength grade is the threaded steel bar of HRB335, thickness is 400mm, concrete strength grade is C30, wherein, basement side The wall 12 and the support pile 2 are connected by connecting steel bars 11 with a diameter of 20 mm and a strength grade of HRB335. The gap between the basement side wall 12 and the support pile 2 is filled with self-compacting waterproof concrete 14, and the viscosity of the self-compacting waterproof concrete 14 is expressed by the degree of expansion of the concrete, which is required to be within the range of 500-700mm.

The utility model also provides a construction method for the anti-floating structure of the piled raft foundation, which mainly includes the following steps:

1) Construction of bored piles: After the foundation pit is excavated to the design elevation, the bored piles 4 are drilled, and the bored piles 4 are poured and then maintained for 28 days to make the bored piles 4 reach the design strength;

2) Excavate the original soil layer: continue to dig the foundation pit for 3~6m, and the elevation of the bottom of the foundation pit is 1m higher than the bottom of the water-stop curtain 3;

3) Pour reinforced concrete water barrier 5 at the bottom of the foundation pit: before constructing reinforced concrete water barrier 5, smooth the part of bored pile 4 close to the foundation pit with grout, and outsource rubber waterstop 6. Bore holes are drilled at the positions connected to the reinforced concrete water barrier 5 on the support pile 2 and the connecting steel bars 11 are arranged. Do the preparation work well, lay the reinforced mesh of the reinforced concrete water barrier 5, weld the surrounding reinforced mesh with the connecting steel bars 11 arranged on the support pile 2, form the waterproof concrete after the reinforced mesh is installed, and wait for the concrete strength to reach After the requirement, an active material water barrier 15 is set at the joint between the support pile 2 and the reinforced concrete water barrier 5 .

4) Install anti-floating anchor rod 7: After the concrete strength of reinforced concrete water baffle 5 meets the requirements, drill holes on reinforced concrete water baffle 5 and insert the prefabricated anti-floating anchor 7 to 1m below the relative bearing layer 16 Above, then grouting into the anti-floating anchor 7 to form the anchor grouting body 17, the grouting method adopts secondary grouting, the first grouting pressure is 0.5-1.0MPa, grouting from the bottom of the hole through the grouting pipe, Inject grout until the orifice does not emit grout; the second grouting pressure is 1.5-3.0MPa. The interval between two grouting before and after is 12h;

5) Backfill lime soil layer 8: backfill lime soil layer 8 layer by layer, each layer of lime soil layer 8 needs to be compacted, and backfill construction to the basement floor elevation;

6) Laying gravel cushion 9: After the lime soil layer 8 is laid, a 300-500mm gravel cushion 9 is laid. Water level detectors and drainage pipes 10 are pre-buried in the gravel cushion 9. The drainage pipes are evenly laid out, and one end extends to In the sump around the basement;

7) Pouring of basement floor 13 and basement side wall 12: Before construction of basement side wall 12, first insert connecting steel bar 11 into the guide hole on support pile 2, and then lay reinforcement for basement floor 13 and basement side wall 12, basement side wall The 12 steel bars are welded with the connecting steel bars 11, and finally the basement floor 13 and the basement side wall 12 are poured into concrete. Finally, the self-compacting waterproof concrete 14 is filled in the gap between the basement side wall 12 and the support pile 2 .

Claims (6)

1. a pile-raft foundation float Structure, is characterized in that basement side wall is connected by horizontal connecting reinforcement with soldier pile; Bored pile has been set under basement bottom board;

Be followed successively by hardcore bed below basement bottom board from top to bottom, backfill grey soil layer, steel concrete water-stop sheet, soft layer, relatively bearing stratum;

The position of steel concrete water-stop sheet, close to water-stop curtain bottom, is formed between steel concrete water-stop sheet and water-stop curtain and closes volume protected from water;

Steel concrete water-stop sheet is connected by connecting reinforcement with soldier pile, cloth hole in interval on steel concrete water-stop sheet, is interspersed with anti-float anchor rod in relative bearing stratum through this hole.

2. pile-raft foundation float Structure according to claim 1, is characterized in that self-compacting water proof concrete is filled in the gap between basement side wall and basement bottom board.

3. pile-raft foundation float Structure according to claim 1, is characterized in that steel concrete water-stop sheet and soldier pile junction arrange active material water proof body.

4. pile-raft foundation float Structure according to claim 1, is characterized in that steel concrete water-stop sheet and bored pile junction are provided with water expandable waterstop.

5. pile-raft foundation float Structure according to claim 1, is characterized in that the connecting reinforcement connecting basement side wall and soldier pile is equidistantly arranged along soldier pile, and the reinforcement welding in this connecting reinforcement and basement side wall.

6. pile-raft foundation float Structure according to claim 1, it is characterized in that hardcore bed thickness is 300 ~ 500mm, in hardcore bed, pre-plugged has water level detector and gutter, and one end of gutter extends to the catch basin of basement.