CN112575794A - Deep silt geological foundation pit support structure and construction method thereof - Google Patents

Abstract

The invention discloses a deep sludge geological foundation pit support structure and a construction method thereof. The deep silt geological foundation pit support structure provided by the invention adopts a form of combining the prestressed pipe piles and the cement mixing pile grid walls, so that the construction is convenient, the cost is low, the construction period is shortened, the water pressure and the soil pressure generated by excavation unloading of the foundation pit are well born, the pressure is transmitted to the support, and the foundation pit is stabilized.

Description

Deep silt geological foundation pit support structure and construction method thereof

Technical Field

The invention relates to the technical field of foundation pit excavation enclosure, in particular to a deep silt geological foundation pit enclosure structure and a construction method thereof.

Background

At present, for excavation engineering of large foundation pits (more than 10000 square meters) in deep silt stratums, higher requirements on foundation pit enclosure safety are provided due to large thickness and poor soil quality of mucky soil layers in the construction process, and adverse effects such as foundation pit collapse, damage to pipelines around the site and roads and the like are easily caused by carelessness. In recent years, prestressed pipe piles are applied in a large amount in soft soil areas due to high pile body strength and low construction cost, but have poor shearing resistance and low bending strength, cannot bear large horizontal thrust, and are easily pushed by external horizontal load to generate crack deflection and even pile breakage.

The above drawbacks are to be improved.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a deep silt geological foundation pit support structure and a construction method thereof.

The technical scheme of the invention is as follows:

in a first aspect, the invention provides a deep sludge geological foundation pit support structure which comprises a support pile, wherein a first cement-soil grid wall is arranged on the outer side of the support pile, a second cement-soil grid wall is arranged on the inner side of the support pile, and the support pile comprises a prestressed pipe pile protection wall and a row of mutually meshed first cement mixing piles arranged on the outer side of the prestressed pipe pile protection wall.

According to the invention of the scheme, the prestressed pipe pile retaining wall comprises a row of prestressed pipe piles arranged at intervals and crown beams arranged at the tops of the row of prestressed pipe piles.

Further, the pile length of the prestressed pipe pile is the same as that of the first cement stirring pile.

Furthermore, the pile length of the prestressed pipe pile and the pile length of the first cement stirring pile are both 12 m-15 m.

Further, the diameter of prestressing force tubular pile is 400mm, adjacent two the stake core interval of prestressing force tubular pile is 800mm, the size of hat roof beam is 0.5m 0.4m, the diameter of first cement stirring stake is 600mm, adjacent two the stake core interval of first cement stirring stake is 450 mm.

Further, the prestressed pipe pile is filled with C30 fine-stone concrete, and the concrete grade of the crown beam is C30.

According to the invention of the above scheme, the first cement-soil grid wall comprises a plurality of second cement mixing piles distributed in a grid shape, and two adjacent second cement mixing piles are meshed with each other;

the second cement soil grid wall comprises a plurality of third cement mixing piles distributed in a grid shape, and every two adjacent third cement mixing piles are meshed with each other.

Furthermore, the diameter of second cement stirring stake with third cement stirring stake is 600mm, and adjacent two the stake core interval of second cement stirring stake is 450mm, and adjacent two the stake core interval of third cement stirring stake is 450 mm.

Further, the pile length of the second cement mixing pile is 12 m-15 m, and the pile length of the third cement mixing pile is 5 m-7 m.

In another aspect, the invention provides a construction method of the deep silt geological foundation pit support structure, which comprises the following steps

S1, measurement lofting: leveling a site on a construction site, and performing measurement lofting according to a design drawing;

s2, dewatering and draining: arranging water collecting pits on two sides of the foundation pit or on the periphery of the foundation pit, and controlling the underground water level in the construction area;

s3, setting the support piles: arranging a supporting pile on a foundation pit excavation boundary line;

s4, arranging a first cement-soil grid wall: arranging a first cement-soil grid wall outside the support pile;

s5, setting a second cement-soil grid wall: arranging a first cement-soil grid wall on the inner side of the support pile;

s6, setting the crown beam: arranging a crown beam at the top of the support pile;

s7, excavating a foundation pit: and after the building enclosure structure reaches the design strength, excavating the foundation pit to the bottom elevation of the bottom plate of the main structure in layers.

Compared with the prior art, the invention has the beneficial effects that:

1. the deep silt geological foundation pit support structure provided by the invention adopts a form of combining the prestressed pipe pile and the cement mixing pile grid wall, so that the construction is convenient, the cost is low, the construction period is shortened, the water pressure and the soil pressure generated by excavation unloading of the foundation pit are well born, and the pressure is transmitted to the support to stabilize the foundation pit;

2. according to the invention, a row of meshed cement mixing piles are arranged outside the prestressed pipe pile retaining wall, so that the waterproof performance of the supporting pile can be well ensured;

3. the pile length of the prestressed pipe pile in the supporting pile is the same as that of the first cement stirring pile, so that the stress strength and the waterproof performance of the supporting pile are better ensured;

4. the prestressed pipe pile is filled with fine stone concrete, and the concrete grade of the crown beam is C30, so that the stress performance of the support pile is further ensured.

Drawings

FIG. 1 is a schematic structural diagram of an embodiment of the present invention;

FIG. 2 is a schematic structural view of a support pile according to an embodiment of the present invention;

FIG. 3 is a schematic structural view of a first soil cement grid wall according to one embodiment of the present invention;

fig. 4 is a schematic structural view of a second cemented soil lattice wall according to an embodiment of the present invention.

In the context of the figures, it is,

1. supporting piles; 101. a first cement mixing pile; 102. pre-stressing pipe piles; 103. a crown beam;

2. a first cemented soil grid wall; 201. a second cement mixing pile;

3. a second cemented soil grid wall; 301. and a third cement mixing pile.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

It should be noted that the terms "mounted," "disposed," "connected," "fixed," and the like are to be understood broadly, and may be, for example, fixedly connected, detachably connected, or integrated; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The terms "upper", "lower", "top", "bottom", "inner", "side", and the like indicate orientations or positions based on the orientations or positions shown in the drawings, and are for convenience of description only and should not be construed as limiting the technical solution. The terms "first", "second" and "first" are used merely for descriptive purposes and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features. The meaning of "plurality" is two or more unless specifically limited otherwise.

Referring to fig. 1 and 2, the invention provides a deep silt geological foundation pit support structure, which is mainly applied to a foundation pit with an area exceeding 10000 square meters and in a soft soil stratum such as a deep silt stratum. The deep silt geological foundation pit support structure comprises a support pile 1, wherein a first cement grid wall 2 is arranged on the outer side of the support pile 1, a second cement grid wall 3 is arranged on the inner side of the support pile 1, and the support pile 1 comprises a prestressed pipe pile protection wall and a row of first cement mixing piles 101 which are mutually meshed and arranged on the outer side of the prestressed pipe pile protection wall. The prestressed pipe pile retaining wall comprises a row of prestressed pipe piles 102 arranged at intervals and a crown beam 103 arranged at the pile tops of the row of prestressed pipe piles 102, and the row of prestressed pipe piles 102 are connected into a whole through the crown beam 103. The first cement grid wall 2 comprises a plurality of second cement mixing piles 201 distributed in a grid shape, and two adjacent second cement mixing piles 201 are mutually meshed. The second soil cement grid wall 3 includes a plurality of third cement mixing piles distributed in a grid shape, and two adjacent third cement mixing piles 301 are engaged with each other.

The prestressed pipe pile 102 is high in pile body strength and low in engineering cost; the cement mixing pile grid wall is convenient to construct and low in construction cost, the surrounding water and soil pressure is resisted by the rigidity of the cement mixing pile grid wall, supporting and anchor pulling are not needed, the space in a foundation pit is spacious, the construction of a main structure is greatly facilitated, and the construction progress is accelerated; meanwhile, the cement soil has good water-resisting performance, so that the silt soil is effectively prevented from flowing laterally, and the defects that the prestressed pipe pile 102 cannot bear large horizontal thrust and is easily pushed by external horizontal load to generate crack deviation or even pile breakage are overcome.

Therefore, the foundation pit support structure adopts a form of combining the prestressed pipe piles 102 and the cement mixing pile grid walls, so that the construction is convenient, the cost is low, the construction period is shortened, and the foundation pit support structure well plays a role in bearing water pressure and soil pressure generated by excavation unloading of the foundation pit, transmitting the pressure to the support and stabilizing the foundation pit; simultaneously, the waterproof performance of a support pile 1 can be well guaranteed by a row of cement mixing piles meshed with each other outside the prestressed pipe pile retaining wall.

In a preferred embodiment, the pile length of the prestressed pipe pile 102 is the same as that of the first cement mixing pile 101, so as to better ensure the stress strength and the waterproof performance of the support pile 1.

In a preferred embodiment, the pile length of the prestressed pipe pile 102 and the pile length of the first cement mixing pile 101 are both 12 m-15 m, the diameter of the prestressed pipe pile 102 is 400mm, the distance between the pile cores of two adjacent prestressed pipe piles 102 is 800mm, the size of the crown beam 103 is 0.5m × 0.4m, the diameter of the first cement mixing pile 101 is 600mm, and the distance between the pile cores of two adjacent first cement mixing piles 101 is 450 mm. Through the prestressed pipe pile 102, the first cement mixing pile 101 and the crown beam 103, the supporting pile 1 can be guaranteed to play a role in enclosing in foundation pits with the areas exceeding 10000 square meters in soft soil stratums such as deep silt stratums.

Furthermore, the prestressed pipe pile 102 is filled with C30 fine-stone concrete, and the concrete grade of the crown beam 103 is C30, so that the stress performance of the support pile 1 is further ensured.

Further, the diameters of the second cement mixing pile 201 and the third cement mixing pile 301 are both 600mm, the distance between the pile cores of the two adjacent second cement mixing piles 201 is 450mm, and the distance between the pile cores of the two adjacent third cement mixing piles 301 is 450 mm. The pile length of the second cement mixing pile 201 is 12 m-15 m, and the pile length of the third cement mixing pile 301 is 5 m-7 m. Through the second cement mixing pile 201 and the third cement mixing pile 301 which are arranged, water pressure and soil pressure generated by a foundation pit with the area exceeding 10000 square meters on a soft soil stratum such as a deep silt stratum can be effectively borne, the pressure is transmitted to a support, and the foundation pit is stabilized.

On the other hand, the invention provides a construction method of a deep silt geological foundation pit support structure, which comprises the following steps:

step S1, measurement lofting: and leveling the site on the construction site, and performing measurement lofting according to a design drawing.

Step S2, dewatering and draining: and water collecting pits are arranged on two sides of the foundation pit or on the periphery of the foundation pit, so that the underground water level in the construction area is controlled, and the safe and smooth operation of excavation and subsequent related construction procedures is ensured.

Specifically, every layer of foundation ditch sets up and cuts (arranges) the ditch, and the foundation ditch is inside to cut (arrange) the ditch and draw water to the upper drainage ditch through the suction pump successive layer, and the sump pit of the superiors is connected with tertiary grit chamber through cutting (arranging) the ditch, filters and reaches the emission requirement after, emits into the municipal pipe network. Meanwhile, in order to ensure smooth drainage, the water interception (drainage) ditch needs to be cleared in time to prevent blockage.

Step S3, the support pile 1 is set: and arranging a supporting pile 1 on the boundary line of the foundation pit excavation. Constructing a prestressed pipe pile 102 in the support pile 1 in a static pressure pile mode, and filling C30 fine-stone concrete into the prestressed pipe pile; a four-stirring four-spraying construction process is adopted for a first cement stirring pile 101 in a support pile 1, 42.5R ordinary portland cement or 32.5R composite portland cement is adopted for cement paste, the cement mixing ratio is 14%, the slurry water cement ratio is 0.55, the slurry feeding pressure is 0.5 MPa-1 MPa, a field is leveled (controlled according to elevation) and compacted before stirring pile construction, and then stirring pile construction is carried out.

The construction process of 'four-stirring four-spraying' comprises the following steps:

1) positioning a drilling machine: a standard and remarkable depth marking ruler is arranged on a derrick of the drilling machine. When the drilling machine is in place, the drilling machine is leveled, the level of the stirring machine is measured by using a leveling ruler, and the verticality of the derrick of the drilling machine is measured by using a theodolite so as to ensure the verticality of the formed pile.

2) Drilling: starting a motor of the stirrer, loosening a steel wire rope of the crane, and enabling the stirrer to stir, cut soil and sink along the guide frame, wherein the sinking speed is monitored and controlled by the current of the motor, and the working current is not larger than 70A.

3) Preparing cement paste: when the mixer sinks to the designed depth, the cement paste is mixed according to the mixing ratio determined by the design, and the cement paste is poured into the aggregate before grouting.

4) Lifting, spraying and stirring: after the mixer sinks to the design degree of depth, open mortar pump and impress grout in the ground, spout the thick liquid while rotatory, promote the mixer according to 0.5m/min strictly simultaneously. The slurry supply can not be interrupted midway during the slurry spraying so as to ensure the pile length. If the slurry spraying is interrupted due to power failure or mechanical failure, the drilling machine is drilled downwards to a position which is not less than 0.5m below the slurry interruption point, and the slurry spraying is lifted again when the slurry supply is recovered. And if the interruption exceeds six hours, pile repair is carried out again.

5) Four stirring and four spraying: and repeating the steps until the requirement of four stirring and four spraying is met.

6) The pile machine is displaced.

Step S4, setting the first cement grid wall 2: and arranging a first cement-soil grid wall 2 outside the support pile 1. Since the construction process of the first soil cement grid wall 2 is similar to that of the first cement mixing pile 101 described above, it will not be described redundantly here.

Step S5, setting the second cement soil grid wall 3: and arranging a first cement-soil grid wall 2 on the inner side of the support pile 1. Since the construction process of the second soil cement grid wall 3 is similar to that of the first cement mixing pile 101 described above, it will not be described redundantly here.

Step S6, the crown beam 103 sets: the top of the support pile 1 is provided with a crown beam 103, the crown beam 103 adopts a wood formwork for supporting, reinforcing steel bars are bound on site, concrete of the crown beam is cast in place manually, the crown beam is put into a bin in a chute mode, an insertion type vibrator is vibrated to be compact, and the crown beam is covered and maintained by water spraying to ensure that the crown beam and the concrete are connected into a whole.

Specifically, the crown beam 103 steel bars are bound on site, and the main bars are lengthened by adopting single-side lap welding. The length of the welding seam is not less than 10d, and the joint with the same section cannot exceed 50%. And each section of the crown beam 103 steel bar reserves the lap joint length for the lower section construction, and is staggered by not less than 1 m. The steel bar joint of the crown beam 103 should avoid the steel pipe supporting position and the construction joint.

The side template of the crown beam 103 adopts a wood mould, the inner keel of the supporting system adopts 100mm multiplied by 100mm square wood, the distance is 300mm, the outer keel adopts phi 48 bidirectional double-layer steel pipe and is fixed by adopting a counter-pull rod, and the template is coated with a release agent before installation.

The concrete of the crown beam 103 is poured in layers by adopting C30 concrete, and is vibrated by an insertion vibrator. When the concrete is vibrated, the vibrating rod is vertically inserted into the concrete and is inserted into a lower layer which is not yet in an initial setting layer by 50-100 mm so as to promote the mutual combination of the upper layer and the lower layer, the distance between each inserting point is not more than 1.5 times of the acting radius of the inserting point, when the vibrating rod is used, the vibrating main point of 'fast inserting and slow pulling' is realized, the vibrating time of each inserting point is preferably 20-30 s, and the concrete surface begins to be slurry and does not bubble.

The concrete of the crown beam 103 is sprayed with water and covered for maintenance immediately after being solidified, and the maintenance time is not less than 14 days. And (3) curing within 12-18 hours after the concrete pouring is finished, and if the concrete is poured in hot or dry seasons, the curing time is advanced to 8-14 hours.

Step S7, excavation of a foundation pit: and after the building enclosure structure reaches the design strength, excavating the foundation pit to the bottom elevation of the bottom plate of the main structure in layers.

Specifically, before the foundation pit is excavated, a technician, an operator, a safety worker and the like must be subjected to detailed safety technology bottom-crossing, the content of the bottom-crossing comprises the section of the foundation pit, the soil piling position, the condition of the existing underground structure, construction requirements and the like, the elevation and the width of the foundation are measured in time, and overexcavation or underexcavation is prevented.

Excavation in the foundation pit needs to be carried out by layering and subsection slope setting, and the excavation depth of each layer is 1m from top to bottom. The better earth stone side of texture is dug out to the foundation ditch adopts dump truck to transport to the temporary storage place of high-voltage line below for the soft soil layer replacement during the foundation ditch excavation increases the bearing capacity, satisfies the requirement that equipment goes out to slag or pile.

The excavation space and the excavation rate of the foundation pit soil body need to be coordinated and matched with each other, and the excavation depth of each working layer is preferably between 1 m. The support of the excavated side slope is not delayed for 6-12 h, and the length of the longitudinal section is not longer than 50 m. And (4) after the foundation pit is excavated to the pit bottom elevation, timely checking and accepting the foundation pit, immediately constructing a bottom plate cushion layer after the foundation pit is qualified, and sealing the foundation pit.

It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.

The invention is described above with reference to the accompanying drawings, which are illustrative, and it is obvious that the implementation of the invention is not limited in the above manner, and it is within the scope of the invention to adopt various modifications of the inventive method concept and technical solution, or to apply the inventive concept and technical solution to other fields without modification.

Claims (10)

1. The utility model provides a deep silt geology foundation ditch retaining structure, a serial communication port, including a fender pile, the fender pile outside is provided with first soil cement grid wall, a fender pile inboard is provided with second soil cement grid wall, a fender pile includes the prestressing force tubular pile dado and sets up the first cement mixing pile of the mutual interlock of a row in the prestressing force tubular pile dado outside.

2. The deep sludge geological foundation pit support structure of claim 1, wherein the prestressed pipe pile retaining wall comprises a row of prestressed pipe piles arranged at intervals and a crown beam arranged at the top of the row of prestressed pipe pile piles.

3. The deep sludge geological foundation pit support structure of claim 2, wherein the pile length of the pre-stressed pipe pile is the same as the pile length of the first cement mixing pile.

4. The deep sludge geological foundation pit support structure of claim 3, wherein the pile length of the prestressed pipe pile and the pile length of the first cement mixing pile are both 12-15 m.

5. The deep sludge geological foundation pit support structure of claim 2, wherein the diameter of the prestressed pipe piles is 400mm, the distance between the cores of two adjacent prestressed pipe piles is 800mm, the size of the crown beam is 0.5m x 0.4m, the diameter of the first cement stirring pile is 600mm, and the distance between the cores of two adjacent first cement stirring piles is 450 mm.

6. The deep sludge geological foundation pit support structure of claim 2, wherein the prestressed pipe piles are filled with C30 fine-stone concrete, and the concrete grade of the crown beam is C30.

7. The deep sludge geological foundation pit enclosure structure of claim 1, wherein the first cemented soil grid wall comprises a plurality of second cement mixing piles distributed in a grid-like manner, and two adjacent second cement mixing piles are meshed with each other;

the second cement soil grid wall comprises a plurality of third cement mixing piles distributed in a grid shape, and every two adjacent third cement mixing piles are meshed with each other.

8. The deep sludge geological foundation pit support structure of claim 7, wherein the diameters of the second cement mixing pile and the third cement mixing pile are both 600mm, the distance between the cores of two adjacent second cement mixing piles is 450mm, and the distance between the cores of two adjacent third cement mixing piles is 450 mm.

9. The deep sludge geological foundation pit support structure of claim 7, wherein the second cement mixing pile has a pile length of 12-15 m, and the third cement mixing pile has a pile length of 5-7 m.

10. A method of constructing a deep sludge geological foundation pit envelope as claimed in any one of claims 1 to 9, comprising

S1, measurement lofting: leveling a site on a construction site, and performing measurement lofting according to a design drawing;

s2, dewatering and draining: arranging water collecting pits on two sides of the foundation pit or on the periphery of the foundation pit, and controlling the underground water level in the construction area;

s3, setting the support piles: arranging a supporting pile on a foundation pit excavation boundary line;

s4, arranging a first cement-soil grid wall: arranging a first cement-soil grid wall outside the support pile;

s5, setting a second cement-soil grid wall: arranging a first cement-soil grid wall on the inner side of the support pile;

s6, setting the crown beam: arranging a crown beam at the top of the support pile;

s7, excavating a foundation pit: and after the building enclosure structure reaches the design strength, excavating the foundation pit to the bottom elevation of the bottom plate of the main structure in layers.

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