CN219909030U - Mattress layer of composite foundation - Google Patents
Mattress layer of composite foundation Download PDFInfo
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- CN219909030U CN219909030U CN202320629891.1U CN202320629891U CN219909030U CN 219909030 U CN219909030 U CN 219909030U CN 202320629891 U CN202320629891 U CN 202320629891U CN 219909030 U CN219909030 U CN 219909030U
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- 239000002131 composite material Substances 0.000 title claims abstract description 75
- 239000002689 soil Substances 0.000 claims abstract description 24
- 230000000149 penetrating effect Effects 0.000 claims abstract description 12
- 238000000034 method Methods 0.000 claims abstract description 4
- 239000004576 sand Substances 0.000 claims description 17
- 239000004575 stone Substances 0.000 claims description 5
- 238000013461 design Methods 0.000 abstract description 13
- 238000010561 standard procedure Methods 0.000 abstract description 8
- 230000007547 defect Effects 0.000 abstract description 4
- 239000010410 layer Substances 0.000 description 88
- 230000000694 effects Effects 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 3
- 238000004364 calculation method Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- 230000002349 favourable effect Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000035515 penetration Effects 0.000 description 2
- 238000011002 quantification Methods 0.000 description 2
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 1
- 235000011941 Tilia x europaea Nutrition 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 239000004571 lime Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 239000011345 viscous material Substances 0.000 description 1
- 239000011800 void material Substances 0.000 description 1
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- Piles And Underground Anchors (AREA)
Abstract
The utility model discloses a mattress layer of a composite foundation, which comprises a foundation, a pile body positioned in the foundation, wherein the mattress layer is positioned at the upper part of the composite foundation and is positioned below the foundation borne by the composite foundation; the thickness d of the mattress layer is greater than the depth s of the pile body penetrating into the mattress layer upwards; compared with the existing standard method, the method considers the important position of the mattress layer in the composite foundation forming condition, calculates the thickness of the mattress layer according to deformation on the basis, avoids the empirical defect of the standard method, realizes quantitative design of the thickness and rigidity of the mattress layer, can ensure that piles and soil between piles form the composite foundation, and avoids the consequence that the piles penetrate through the mattress layer to directly jack the foundation so as to lead the foundation to be empty from the natural ground.
Description
Technical Field
The utility model relates to the technical field of foundation treatment, in particular to a mattress layer of a composite foundation.
Background
In recent years, composite foundation technology is widely applied in China, but the theoretical research of the current composite foundation technology is behind engineering practice, wherein the most outstanding problem is that the research on the formation condition of the composite foundation is not deep enough, so that some engineering problems occur, for example, the problem that the foundation and the natural mud surface are empty after a bead triangle small and medium-sized hydraulic building is treated by adopting a rigid pile composite foundation, the main reason is that the deformation of pile soil is inconsistent, the rigid pile upwards pierces a mattress cushion layer due to the fact that the foundation settlement is larger than the deformation of the rigid pile, the foundation is directly jacked, finally, the rigid pile bears all upper load, the soil and the foundation are empty, the soil between piles does not bear upper load any more, the ideally designed composite foundation becomes an actual traditional pile foundation, at the moment, the bearing capacity of the composite foundation calculated by utilizing the composite foundation design theory is larger, the calculated settlement is smaller than the actual settlement, and the engineering is unsafe.
The pile body (rigid pile or flexible pile) and the soil between piles in the composite foundation can directly bear load under the action of upper load, which is the essential characteristic of the composite foundation and is the difference between the composite foundation and the traditional pile foundation. Only in the design of the composite foundation, the pile body and the soil between piles are guaranteed to directly bear load under the load effect, and the composite foundation can be really formed. A large number of researches show that the mattress layer arranged on the upper part of the composite foundation and below the foundation plays a very important role in coordinating the pile, the soil load sharing proportion and the deformation coordination, and is a key point of effectively forming the composite foundation by the pile body and soil between the piles. Neglecting the design of mattress layer inevitably causes the problems of engineering adopting composite foundation, such as the problem of void between the foundation and the natural mud surface.
Currently, the technical specifications for composite foundations often specify the placement of mattress layers empirically, as specified by the composite foundation specifications (GB/T50783-2012): for a discrete material pile composite foundation, such as a sand pile composite foundation, the thickness of the mattress layer is 300-500 mm of the broken stone layer; for a viscous material pile composite foundation, such as a deep mixing pile composite foundation, the thickness of the mattress layer can be 150-300 mm, the material can be middle sand, coarse sand, graded sand stone and the like, and the maximum grain diameter is not more than 20mm; for the rigid pile composite foundation, the thickness of the mattress layer is preferably 100-300 mm, the material is preferably medium sand, coarse sand, well graded sand or broken stone, lime and the like, and the maximum sand particle diameter is not more than 30 mm. Other specifications such as rigid-flexible pile composite foundation technical specifications (JGJ/T210-2010) and building foundation treatment technical specifications (JGJ 79-2012) are also about the same empirical specifications for the arrangement of mattress layers. The conventional standard method is more empirical for mattress layer design of a composite foundation, so that on one hand, the operability of standard execution is not strong, and a designer is required to have quite abundant geotechnical experience for subjective judgment; on the other hand, different mattress layer settings will necessarily cause different load sharing ratios of pile bodies and soil between piles in the composite foundation, but according to the above specifications, different mattress layer settings will obtain the same calculation result, which obviously does not accord with engineering practice, sometimes even causes potential safety hazards.
The utility model provides a mattress layer of a composite foundation, which has important practical significance for promoting the deep development of the composite foundation technology.
Disclosure of Invention
The utility model aims to provide a mattress layer of a composite foundation, which solves the empirical problem of the arrangement of the mattress layer of the composite foundation in the current specification, realizes quantification of the design thickness of the mattress layer through deformation calculation, avoids the subjectivity defect of a specification method, and ensures that a pile body and soil between piles form the composite foundation.
In order to achieve the above purpose, the technical scheme of the utility model is as follows:
a mattress layer of the composite foundation, the composite foundation comprising a foundation, a pile body positioned in the foundation, the mattress layer positioned on the upper part of the foundation, and the mattress layer positioned below the foundation borne by the composite foundation; the thickness d of the mattress layer is larger than the depth s of the pile body penetrating into the mattress layer upwards, namely d > s;
wherein ,
pi is 3.14; E. v is the deformation modulus (MPa) and poisson's ratio of the mattress layer, respectively; r is the radius (m) of the pile body; sigma is pile top stress (kPa).
Further, the foundation borne by the composite foundation is a rigid foundation, the mattress layer positioned below the rigid foundation and at the upper part of the foundation is a flexible mattress layer, and the flexible mattress layer is middle sand or coarse sand or graded sand.
Further, the foundation borne by the composite foundation is a flexible foundation, the mattress layer positioned below the flexible foundation and at the upper part of the foundation is a semi-rigid mattress layer, and the semi-rigid mattress layer is a gray soil mattress layer or a geogrid reinforced broken stone mattress layer.
The beneficial effects of the utility model are as follows:
1. compared with the existing standard method, the method considers the important position of the mattress layer in the composite foundation forming condition, and the depth of the pile body penetrating the mattress layer upwards is calculated through deformation on the basis, so that the thickness of the mattress layer can be quantitatively determined, the empirical defect of the standard method is avoided, the quantification of the thickness of the mattress layer is realized, the composite foundation can be formed by the pile body and the soil between the piles, and the consequence that the pile body penetrates through the mattress layer to directly jack the foundation to enable the foundation to be separated from the natural ground is avoided.
2. The existing standard method is fuzzy in design of the thickness of the mattress layer, and in practical engineering, the thickness of the mattress layer meeting engineering safety can be larger than the existing standard value or smaller than the standard value; the thickness of the mattress layer can be quantitatively determined through the utility model, and the utility model provides favorable guarantee for engineering safety adopting the composite foundation.
Drawings
FIG. 1 is a schematic view of pile penetration into a mattress pad.
Wherein: a foundation 1; a pile body 2; a mattress layer 3; a foundation 4; and a composite foundation 5.
Detailed Description
The present utility model will be further described with reference to the accompanying drawings for the purpose of making the objects, technical solutions and advantages of the present utility model more apparent.
The composite foundation 5 includes a foundation 1, a pile body 2 located in the foundation, and a mattress layer 3 located at an upper portion of the foundation 1, and the mattress layer 3 is located below a foundation 4 borne by the composite foundation.
For a rigid foundation such as a composite foundation under a sluice gate chamber concrete bottom plate, in order to increase the proportion of the soil bearing load among piles, the bearing potential of the soil among piles is fully utilized, the bearing capacity of the composite foundation is improved, and a flexible mattress layer is arranged below the rigid foundation and on the upper part of the composite foundation and adopts middle sand, coarse sand, graded sand and the like.
For a flexible foundation such as a filled embankment and a composite foundation under a flexible surface layer pile field, in order to prevent a pile body 2 from penetrating through a mattress pad layer 3 upwards to penetrate into the flexible foundation, the pile-soil stress ratio is increased, the bearing potential of the pile body is fully exerted, the bearing capacity of the composite foundation is improved, the settlement of the composite foundation is reduced, a mattress pad layer with better rigidity, namely a semi-rigid mattress pad layer, is arranged below the flexible foundation and on the upper part of the composite foundation, and the semi-rigid mattress pad layer is made of a lime-soil pad layer, a geogrid reinforced gravel pad layer and the like.
When the design thickness of the mattress layer 3 is thinner or the rigidity is smaller, the pile body 2 possibly pierces into the mattress layer 3 upwards, once the pile body 2 passes through the mattress layer 3 to directly jack the foundation 4, the upper load is borne by the pile body 2, the soil between piles does not bear the upper load, the composite foundation is degenerated to be the pile foundation, the composite foundation is not formed, and the soil between piles does not participate in the action any more, so that the result obtained by utilizing the calculation formula of the composite foundation is dangerous, and the engineering is unsafe; according to the above analysis, the condition that the pile body 2 and the soil between piles form a composite foundation is that the pile body 2 cannot pass through the mattress layer 3, i.e., the depth of the pile body 2 penetrating up into the mattress layer 3 cannot exceed the thickness of the mattress layer 3.
For a single pile type composite foundation, the depth s of the pile body 2 penetrating into the mattress layer 3 is calculated by the following formula:
wherein: pi is 3.14; E. v is the deformation modulus (MPa) and poisson's ratio of the mattress layer, respectively; r is the radius (m) of the pile body; sigma is pile top stress (kPa).
The deformation modulus E (MPa) and Poisson's ratio v of the mattress layer can be determined by indoor tests or experience.
Pile top stress sigma can generally adopt a minimum value between the bearing capacity of the pile body and the bearing capacity provided by the pile periphery and pile end soil body.
The thickness d of the mattress layer is not smaller than the depth s of the pile body penetrating upwards into the mattress layer, namely d > s, obtained according to the formula (1); in practical engineering application, the thickness d of the mattress layer is larger than the depth s of the pile body penetrating into the mattress layer upwards.
For a multi-pile composite foundation, such as a rigid-flexible pile composite foundation, under the same condition, the depth of the flexible pile penetrating into the cushion layer is smaller than the depth of the rigid pile penetrating into the cushion layer, so that the rigid pile, the flexible pile and soil among the piles directly bear upper load together to form the composite foundation, and the depth s of the rigid pile penetrating into the cushion layer upwards is only required to be ensured not to exceed the thickness d of the cushion layer.
Because the pile body pierces the mattress pad layer, foundation soil in a certain range below the mattress pad layer can generate a downward pulling force effect, namely a negative friction resistance effect, on the pile at the periphery of the pile, so that the depth of the pile top piercing the mattress pad layer is reduced, and the design thickness of the mattress pad layer can be correspondingly reduced during design. Since this value is small in number and has a suppressing effect on the penetration depth of the rigid piles into the mattress layer to or beyond the thickness of the mattress layer, the influence thereof may not be taken into consideration from the viewpoint of the design safety of the mattress layer thickness.
And in a certain sluice project, the site foundation is mucky soil, and the foundation treatment is carried out by adopting a precast pile composite foundation. The rubble mattress layer is arranged under the bottom plate of the lock chamber, the deformation modulus of the mattress layer is about 15MPa, the Poisson ratio is 0.2, the pile radius is 0.25m, the pile top stress is 8MPa, and the thickness of the mattress layer is calculated. According to formula (1), s=201 mm can be found, and in order to ensure that the piles do not pierce the mattress layer, the mattress layer thickness is required to be not less than 201mm. If the thickness of the mattress pad is smaller than 201mm, the pile can directly pierce the mattress pad to prop up the bottom plate, so that the bottom plate and the natural mud surface are separated, and the prefabricated pile composite foundation cannot be formed.
Further, the other conditions in the above examples are not changed, and when the deformation modulus of the mattress layer is 8MPa, s=377 mm can be obtained according to the formula (1), and in order to ensure that the piles do not pierce the mattress layer, the thickness of the mattress layer is required to be not less than 377mm. According to the composite foundation technical specification (GB/T50783-2012) it is specified that: for the rigid pile composite foundation, the thickness of the mattress layer is preferably 100-300 mm, the thickness requirement of the mattress layer is not less than 377mm and exceeds the standard range, and the analysis shows that the coordinated design of the thickness and the rigidity of the mattress layer can be realized according to deformation coordination, so that the empirical defect of a standard method is avoided; the analysis simultaneously shows that the standard method is fuzzy in design of mattress layer thickness, and in practical engineering, the thickness of the mattress layer meeting engineering safety may be larger than the existing standard value or smaller than the standard value; the thickness of the mattress layer can be quantitatively determined through the utility model, and the utility model provides favorable guarantee for engineering safety adopting the composite foundation. Finally, it should be noted that: the foregoing description is only a preferred embodiment of the present utility model and is not intended to limit the utility model, but rather the present utility model is described in detail with reference to the foregoing embodiments, and modifications and equivalents of some of the technical features described in the foregoing embodiments may be readily apparent to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present utility model should be included in the protection scope of the present utility model.
Claims (3)
1. The mattress layer of the composite foundation (5) comprises a foundation (1), a pile body (2) positioned in the foundation (1), the mattress layer (3) is positioned at the upper part of the foundation (1), and the mattress layer (3) is positioned below a foundation (4) borne by the composite foundation (5); the method is characterized in that: the thickness d of the mattress layer (3) is larger than the depth s of the pile body (2) penetrating into the mattress layer (3) upwards, namely d > s;
wherein ,
pi is 3.14; E. v is the deformation modulus (MPa) and poisson's ratio of the mattress layer, respectively; r is the radius (m) of the pile body; sigma is pile top stress (kPa).
2. The mattress layer of a composite foundation of claim 1, wherein: the foundation (4) borne by the composite foundation (5) is a rigid foundation, the mattress layer (3) positioned below the rigid foundation and on the upper part of the foundation (1) is a flexible mattress layer, and the flexible mattress layer is middle sand or coarse sand or graded sand.
3. The mattress layer of a composite foundation of claim 1, wherein: the foundation (4) borne by the composite foundation (5) is a flexible foundation, the mattress layer (3) positioned below the flexible foundation and at the upper part of the foundation (1) is a semi-rigid mattress layer, and the semi-rigid mattress layer is a gray soil layer or a geogrid reinforced broken stone layer.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202320629891.1U CN219909030U (en) | 2023-03-27 | 2023-03-27 | Mattress layer of composite foundation |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202320629891.1U CN219909030U (en) | 2023-03-27 | 2023-03-27 | Mattress layer of composite foundation |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN219909030U true CN219909030U (en) | 2023-10-27 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202320629891.1U Active CN219909030U (en) | 2023-03-27 | 2023-03-27 | Mattress layer of composite foundation |
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| Country | Link |
|---|---|
| CN (1) | CN219909030U (en) |
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- 2023-03-27 CN CN202320629891.1U patent/CN219909030U/en active Active
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