CN115419056A - Reinforcing structure for resisting foundation expansion and contraction deformation and design method - Google Patents
Reinforcing structure for resisting foundation expansion and contraction deformation and design method Download PDFInfo
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- CN115419056A CN115419056A CN202211096696.3A CN202211096696A CN115419056A CN 115419056 A CN115419056 A CN 115419056A CN 202211096696 A CN202211096696 A CN 202211096696A CN 115419056 A CN115419056 A CN 115419056A
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- 230000008602 contraction Effects 0.000 title claims abstract description 24
- 230000003014 reinforcing effect Effects 0.000 title claims abstract description 21
- 238000000034 method Methods 0.000 title claims abstract description 15
- 238000013461 design Methods 0.000 title abstract description 6
- 239000002689 soil Substances 0.000 claims abstract description 24
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 22
- 230000002787 reinforcement Effects 0.000 claims abstract description 18
- 238000004364 calculation method Methods 0.000 claims description 26
- 230000009467 reduction Effects 0.000 claims description 8
- 239000011150 reinforced concrete Substances 0.000 claims description 7
- 239000000463 material Substances 0.000 claims description 6
- 230000006835 compression Effects 0.000 claims description 4
- 238000007906 compression Methods 0.000 claims description 4
- 229920001971 elastomer Polymers 0.000 claims description 4
- 239000000806 elastomer Substances 0.000 claims description 4
- 230000008569 process Effects 0.000 claims description 3
- 238000005086 pumping Methods 0.000 claims description 3
- 238000012360 testing method Methods 0.000 claims description 3
- 239000004567 concrete Substances 0.000 claims 1
- 230000000694 effects Effects 0.000 abstract description 3
- 239000003673 groundwater Substances 0.000 description 8
- 239000004746 geotextile Substances 0.000 description 3
- 238000010276 construction Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000008961 swelling Effects 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
- E02D5/22—Piles
- E02D5/48—Piles varying in construction along their length, i.e. along the body between head and shoe, e.g. made of different materials along their length
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D3/00—Improving or preserving soil or rock, e.g. preserving permafrost soil
- E02D3/02—Improving by compacting
- E02D3/10—Improving by compacting by watering, draining, de-aerating or blasting, e.g. by installing sand or wick drains
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
- E02D5/22—Piles
- E02D5/52—Piles composed of separable parts, e.g. telescopic tubes ; Piles composed of segments
- E02D5/523—Piles composed of separable parts, e.g. telescopic tubes ; Piles composed of segments composed of segments
- E02D5/526—Connection means between pile segments
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
- E02D5/72—Pile shoes
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/10—Geometric CAD
- G06F30/13—Architectural design, e.g. computer-aided architectural design [CAAD] related to design of buildings, bridges, landscapes, production plants or roads
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
- G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces
Abstract
The invention belongs to the technical field of geotechnical engineering foundation treatment, and particularly relates to a reinforcement structure for resisting foundation expansion and contraction deformation and a design method thereof. The reinforcing structure is a prefabricated concave-convex hollow pile, the prefabricated concave-convex hollow pile comprises a pile head, a pile tip and at least one pile body which are connected in a segmented mode, concave pile bodies are arranged on the pile body at intervals along the length direction of the pile body, and a plurality of water permeable holes are formed in the concave pile bodies along the circumferential direction; the circumference of the concave pile body is also provided with an expansion-reducing permeable layer. According to the reinforcing structure provided by the invention, the whole hollow pile is in a concave-convex structure by arranging the plurality of concave pile bodies, the concave pile bodies are provided with the plurality of water permeable holes, and the concave pile bodies are also provided with the circle of expansion-reducing water permeable layers; this subtract the permeable bed that expands can adapt to ground inflation or shrink, and the setting on the permeable bed that subtracts expands plays the effect of the all soil body of support pile on the one hand, has avoided the hole of collapsing, and on the other hand has reserved the deformation space for the inflation of ground again, plays the purpose that prevents the ground upwarp and warp.
Description
Technical Field
The invention belongs to the technical field of geotechnical engineering foundation treatment, and particularly relates to a reinforcement structure for resisting foundation expansion and contraction deformation and a design method thereof.
Background
Expansive soils are widely distributed worldwide, and more than 40 countries and regions have been found to have expansive soils. The expansive soil is most typically characterized by water absorption expansion, water loss shrinkage and repeated expansion and contraction deformation, which is a serious challenge for foundation treatment under the control of high-speed rail millimeter-scale deformation.
With the increase of the opening operation mileage and the operation time in China, structures such as high-speed rail roadbeds and tunnels in expansive soil areas gradually have the phenomenon of upwarp deformation, the upwarp deformation value exceeds the railway smoothness allowable range, and railway bureau engineering departments generally adopt modes such as large-machine tamping, track fine adjustment and the like for treatment, but can not fundamentally solve the problem, the normal operation of high-speed rails is seriously influenced, and the labor, material resources and financial resources required to be invested in maintenance work are large.
Disclosure of Invention
The invention aims to: aiming at the defects of the prior art that the foundation arching deformation is prevented and controlled by adopting modes such as large tamping or track fine adjustment, the temporary solution and the permanent solution are not eliminated, the structure and the design method can prevent the overlarge settlement of the roadbed while the arching deformation of structures such as the roadbed, the tunnel and the like in the expansive rock-soil area is prevented, and the structure and the design method are convenient and fast to construct, easy to control the quality and economic and reasonable in scheme.
In order to achieve the purpose, the invention adopts the technical scheme that:
a reinforcing structure for resisting foundation expansion and shrinkage deformation is a prefabricated concave-convex hollow pile, the prefabricated concave-convex hollow pile comprises a pile head, a pile tip and at least one pile body which are connected in a segmented mode, a cavity is formed in the prefabricated concave-convex hollow pile along the axis direction of the prefabricated concave-convex hollow pile, each pile body comprises a convex pile body and a concave pile body along the axis direction, the convex pile body is arranged between every two adjacent concave pile bodies, and the concave pile bodies are circumferentially provided with a plurality of water permeable holes; the concave pile body is also provided with an expansion-reducing permeable layer in the circumferential direction.
The invention provides a prefabricated concave-convex hollow pile structure capable of resisting foundation expansion and contraction deformation, which is integrally a segmented prefabricated structural member, wherein a convex pile body and a concave pile body are arranged at intervals to enable the whole hollow pile to be in a concave-convex structure; when the expansion-reducing permeable layer is expanded in the ground, the expansion-reducing permeable layer can elastically deform to adapt to the expansion and contraction deformation of the ground. The setting of the expansion-reducing permeable layer plays a role in supporting soil around the pile on one hand, avoids hole collapse, and reserves a deformation space for the expansion of the foundation on the other hand, thereby achieving the purpose of preventing the foundation from arching and deforming due to the expansion. Furthermore, groundwater accessible subtracts bloated permeable bed, in the hole gets into the hollow pile, takes the mode of drawing water to the hollow pile to reach the purpose of falling drainage groundwater, consequently, subtract bloated permeable bed still indirect effect of playing the drainage groundwater of falling.
The prefabricated concave-convex hollow pile comprises a pile head, a multi-section pile body in a concave-convex structure and a pile tip, and is manufactured separately, so that standardized and efficient production can be realized, and the transportation is convenient. The prefabricated concave-convex hollow pile can be spliced according to different reinforcing depths on site, and construction is more flexible and convenient. Groundwater in the ground can get into the cavity of prefabricated concave-convex type hollow pile through the hole of permeating water of pile body, carries out the pump drainage when necessary, reduces ground water level to reach the mesh that subtracts bloated.
Preferably, in the prefabricated concave-convex hollow pile, each section of the pile body comprises a first protruding part and a second protruding part, the first protruding part is positioned at the end part of the pile body, the second protruding part is positioned in the middle of the pile body, and a concave pile body is arranged between the first protruding part and the second protruding part.
In the preferred technical scheme of the invention, the adjacent two concave pile bodies are in a convex structure relative to the concave structure, and the convex pile body can be well contacted with the foundation to uniformly transfer the load of the upper part to the foundation so as to play a bearing role. A concave-convex pile body structure can not only play the role of resisting the expansion and contraction deformation of the foundation, but also can be used as the foundation for reinforcement and play the role of controlling the settlement.
Preferably, each pile body comprises at least two or more repeated calculation units, and the height of each calculation unit is H 0 The height of the second projecting part (the projecting pile body) is H 3 Each concave pile body has a height of H 4 And the relationship between the three accords with:
H 0 ＝H 3 +H 4 (a)；
wherein H 3 The range of (A) is 0.4 to 0.6m; h 4 The range of (2) is 0.4 to 0.6m.
Preferably, the height of the pile head is H 1 The height of the pile tip is H 2 ；H 1 The value range of (A) is 0.4-0.5m; h 2 The value range of (A) is 0.4-0.5 m. The length L of the prefabricated hollow pile is calculated according to the following formula:
L＝H 1 +H 2 +nH 0 (b)
as a preferable scheme of the invention, the expansion-reducing water-permeable layer is a flexible elastomer, and the expansion-reducing water-permeable layer is wrapped around the concave pile body; preferably, the expansion-reducing water-permeable layer is wrapped by the water-permeable geotextile to play a role in reverse filtration and drainage. The cross-sectional thickness of the expansion-reducing water-permeable layer is 0.2-0.8 m.
Preferably, the pile tip is solid round platform type structure, the pile body the pile head is cylindrical structure, the pile head the pile body all has seted up the cavity along its axis direction.
Preferably, the outer diameters of the pile head, the pile tip and the convex pile body are D, and the outer diameter of the concave pile body is D; the value range of D is 0.6-1.2 m; the value scheme of d is 0.3-0.6 m.
Preferably, one end of the drain pipe is connected to the bottom of the hollow cavity, and the other end of the drain pipe is connected to a pumping and drainage system on the ground. When the underground water level needs to be reduced, water can be pumped through the drainage pipe, and therefore the purpose of reducing the underground water level is achieved.
Preferably, the reinforced structure further comprises an expansion reducing buffer layer or a reinforcing layer, the reinforcing layer is arranged on the pile head of the prefabricated hollow pile, and the reinforcing layer is a reinforced concrete slab.
A method for designing a reinforcement structure for resisting foundation expansion and contraction deformation comprises the following steps:
step 1: designing a structure of the prefabricated hollow pile, and drawing up the structural parameters of the prefabricated hollow pile: respectively comprises a convex pile body outer diameter D, a concave pile body outer diameter D and a cavity inner diameter c, and the minimum repeating unit in a single pile body is specified as a calculation unit, wherein the height of each calculation unit is H 0 The height of the second projecting part is H 3 The height of the concave pile body is H 4 ；
And 2, step: checking the expansion and shrinkage deformation resistance of the prefabricated hollow pile by using the calculation unit, and determining the pile spacing S within a reasonable range;
and step 3: when the pile spacing S does not accord with the reasonable value range, readjusting the parameter value in the step 1 to calculate until the pile spacing S is determined;
and 4, step 4: determining the allowable bearing capacity P of the single pile according to the upper load of the prefabricated hollow pile and the pile spacing S;
and 5: checking and calculating the bearing capacity of a single pile and the depth L of an atmospheric influence layer according to the size parameters of the pile body of the prefabricated hollow pile 0 And comprehensively determining the final pile length L.
Preferably, the specific calculation process of the pile spacing S includes:
determining a compressible space M of a pile body:
determining and calculating the volume N of soil around the unit pile:
the prefabricated hollow pile needs to meet the requirement that M zeta is more than or equal to N alpha (e)
The formula (d) can obtain that the pile spacing S of the prefabricated hollow pile meets the following conditions:
and xi is the compression coefficient of the expansion-reducing water-permeable layer, and can be 0.3-0.8 according to the material property, and alpha is the volume expansion rate of the foundation (expansive soil) and is determined according to the geotechnical test.
Preferably, the calculation formula of the allowable bearing capacity [ P ] of the single pile is as follows:
wherein, U represents the perimeter of the convex pile body part;
q i indicating the allowable side resistance (kPa) of the convex pile body part pile Zhou Di i layer soil;
l i representing the total thickness of the convex pile body part in the pile Zhou Di i layers of soil;
a represents the vertical projection area of the pile tip;
Q p represents pile tip base layer allowable end resistance (kPa);
the allowable bearing capacity [ P ] of the single pile needs to satisfy the following formula, and the number n of the pile body sections is determined according to the allowable bearing capacity [ P ]:
[P]≥P (h)
wherein, P is the upper load to be borne by the single pile.
The pile length L satisfies the depth L of the atmospheric influence layer or more 0 ；
L≥L 0 (i)
And (e) when the pile length L obtained by calculation does not meet the requirements of the formulas (g) - (i), readjusting the parameter values to carry out checking calculation of the formulas (c) - (f).
The reinforced structure resisting the expansion and contraction deformation of the foundation is constructed according to the following method:
s1, prefabricating a concave-convex hollow pile;
s2, cleaning and leveling a field;
s3, positioning, mechanically guiding holes and sinking piles;
s4, arranging a drain pipe in the hollow pile;
s5, constructing an upper expansion reduction buffer layer;
s6, constructing a pile top reinforced concrete slab or a reinforced cushion layer;
and S7, constructing an upper roadbed or a structure.
In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:
the invention provides a prefabricated concave-convex hollow pile structure, which is a segmented prefabricated structural member, wherein a convex pile body and a concave pile body are arranged at intervals to enable the whole hollow pile to have a concave-convex structure; when the expansion-reducing water-permeable layer is expanded by a foundation, the expansion-reducing water-permeable layer can be compressed and thinned, so that the expansion-reducing water-permeable layer is suitable for the expansion of the foundation; when the foundation shrinks, the expansion-reducing water-permeable layer can restore the deformation of the self-compressed layer. The setting of the expansion-reducing permeable layer plays a role in supporting soil around the pile on one hand, avoids hole collapse, and reserves a deformation space for the expansion of the foundation on the other hand, thereby achieving the purpose of preventing the foundation from arching and deforming due to the expansion. Furthermore, groundwater accessible subtracts bloated permeable bed, in the hole gets into the hollow pile, takes the mode of drawing water to the hollow pile to reach the purpose of falling drainage groundwater, consequently, subtract bloated permeable bed still indirect effect of playing the drainage groundwater of falling.
The prefabricated structural part comprises the pile head, the multi-section concave-convex pile body and the pile tip, is manufactured separately, can realize standardized and efficient production, and is convenient to transport. The prefabricated hollow pile can be spliced according to different reinforcing depths on site, and construction is more flexible and convenient. Underground water in the foundation can be drained into the cavity of the prefabricated hollow pile through the water permeable holes of the pile body, and is pumped out when necessary, so that the water content of the soil layer of the foundation is reduced, and the purpose of reducing expansion is achieved.
According to the technical scheme, the two adjacent concave pile bodies are of a convex structure relative to the concave structure, and the convex pile bodies can be well contacted with the foundation to uniformly transfer the load of the upper part to the foundation so as to play a bearing role. A concave-convex pile body structure can not only play the role of resisting the expansion and contraction deformation of the foundation, but also can be used as the foundation for reinforcement and play the role of controlling the settlement.
The pile top is provided with the reinforced concrete plate, and the reinforced concrete plate, the concave-convex hollow pile and the expansion reduction layer form a reinforcement technology for resisting expansion and shrinkage deformation of the foundation together, and the reinforced concrete plate is particularly suitable for the foundation which is easy to expand and shrink deformation such as expansive soil. After the concave-convex hollow pile is used for reinforcing the foundation, the expansion and shrinkage deformation of the foundation can be overcome, the foundation is prevented from arching, the upper load can be borne, the foundation settlement is controlled, and the purpose of resisting the expansion and shrinkage deformation of the foundation is achieved.
Drawings
Fig. 1 is a schematic structural view of a prefabricated concavo-convex type hollow pile of the present invention;
FIG. 2 is a schematic cross-sectional view of a reinforcing structure of the present invention;
FIG. 3 is an enlarged view of a portion A of the reinforcement structure of the present invention;
FIG. 4 is a schematic size view of a single section of pile shaft of the present invention;
an icon: 1-pile head; 2-pile tip; 3, pile body; 4-a cavity; 5-reducing the swelling and water permeable layer; 31-concave pile body; 32-first bulge, 33-second bulge, 6-drain pipe, 7-permeable hole, 8-expansion reduction buffer layer, 9-reinforcing layer and 10-load.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
A reinforced structure for resisting foundation expansion and contraction deformation is shown in figures 1 and 2-3, and is a prefabricated concave-convex hollow pile, wherein the prefabricated concave-convex hollow pile comprises a pile head 1, a pile tip 2 and at least one pile body 3 which are connected in a segmented manner, and the pile head 1 and the pile body 3 are respectively provided with a through cavity 4 along the length direction; a concave pile body 31 is arranged at the middle section of each pile body 3, and a plurality of water permeable holes 7 are formed in the concave pile body 31 along the circumferential direction; the concave pile body 31 is also provided with an expansion-reducing permeable layer 5 in the circumferential direction. Specifically, the expansion-reducing water-permeable layer 5 is a flexible elastomer, and the expansion-reducing water-permeable layer 5 is wrapped around the concave pile body 31. More specifically, the cross-sectional thickness of the expansion-reducing water-permeable layer 5 is 0.2-0.8 m, the expansion-reducing water-permeable layer is composed of water-permeable geotextile and a drainage net core, the geotextile and the drainage net core are made of geotechnical materials and have good water permeability, and the net core is a low-strength elastomer. When the expansion reducing permeable layer 5 is expanded in the ground, the expansion reducing permeable layer can be compressed and thinned, and when the ground contracts, the expansion reducing permeable layer 5 can restore the deformation of the self compression, so that the deformation balance between the ground and the pile body is achieved, and the ground is prevented from being arched and deformed.
Specifically, in this embodiment, the structure of the single pile body is as shown in fig. 4: every section both ends of pile body 3 all are provided with the bulge, and the middle part interval is provided with the bulge, and wherein the bulge of tip is first bulge 32, and the bulge in middle part is second bulge 33, is concave type pile body 31 between first bulge 32 and the second bulge 33. Wherein the height of the first protrusion 32 is H 3 The height of the concave pile body is H 4 The height of the second projecting portion 33 is H 3 And 2, each pile body 3 comprises a plurality of repeated calculation units. The size of the individual calculation units corresponds to the following formula: h 0 ＝H 3 +H 4 (a)；
H 3 The range of (A) is 0.4 to 0.6m; h 4 The range of (A) is 0.4 to 0.6m.
The height of the pile head 1 is H 1 The height of the pile tip 2 is H 2 ；H 1 The value range of (A) is 0.4-0.5m; h 2 The value range of (A) is 0.4-0.5m; the outer diameter of the pile head 1 and the pile tip 2 is D, and the outer diameter of the concave pile body 31 is DThe outer diameter is d; the value range of D is 0.6-1.2 m; the value range of d is 0.3-0.6 m; the height L of the prefabricated concave-convex hollow pile is calculated according to the following formula:
L＝H 1 +H 2 +nH 0 (b)
in this embodiment, the prefabricated concave-convex hollow pile includes two prefabricated pile bodies 3, and each pile body 3 includes two repeated calculation units. The adjacent pile bodies 3 are connected through flanges.
A drain pipe 6 is arranged in the cavity 4, one end of the drain pipe 6 is connected to the bottom of the cavity 4, and the other end of the drain pipe 6 is connected to an above-ground pumping and drainage system. The pile head is characterized in that an expansion reduction buffer layer 8 is arranged at the position of the pile head 1, and the expansion reduction buffer layer 8 is made of geotechnical materials.
The top of the pile head 1 is also provided with a reinforcing layer 9, and the reinforcing layer 9 is a reinforced concrete layer; the reinforcing layer 9 and the prefabricated concave-convex hollow pile jointly form a foundation reinforcing structure, and bear the load 10 from an upper roadbed or a structure.
In the embodiment, the pile spacing, the pile body strength, the lengths and the outer diameters of the concave and convex pile body sections, the expansion and water permeable layer and the like of the concave and convex hollow pile are determined by comprehensive calculation according to the conditions of the strength, the expansion and contraction property, the upper load cutoff and the like of foundation soil.
Example 2
A method for designing a reinforcement structure for resisting foundation expansion and contraction deformation comprises the following steps:
step 1: designing the structure of the prefabricated hollow pile, and drawing up the structural parameters of the prefabricated hollow pile: respectively comprises a convex pile body outer diameter D, a concave pile body outer diameter D and a cavity inner diameter c, and the minimum repeated unit in a single pile body is specified as a calculation unit, wherein the height of each calculation unit is H 0 The height of the second projecting part is H 3 The height of the concave pile body is H 4 ；
Step 2: carrying out expansion and shrinkage deformation resistance checking calculation on the prefabricated hollow pile by using the calculating unit, and determining a pile spacing S in a reasonable range; wherein, the reasonable pile spacing S is preferably 3 to 5 times of the outer diameter D of the convex pile body part.
And step 3: when the pile spacing S does not accord with the reasonable value range, readjusting the parameter values in the step 1 to calculate until the pile spacing S is determined;
and 4, step 4: determining the allowable bearing capacity P of the single pile according to the upper load of the prefabricated hollow pile and the pile spacing S;
and 5: checking and calculating the bearing capacity of a single pile and the depth L of an atmospheric influence layer according to the size parameters of the pile body of the prefabricated hollow pile 0 And comprehensively determining the final pile length L.
Preferably, the specific calculation process of the pile spacing S includes:
determining the compressible space M of the pile body 3:
determining and calculating the volume N of soil around the unit pile:
the prefabricated hollow pile needs to meet the requirement that M zeta is more than or equal to N alpha (e) in resisting foundation expansion and contraction deformation
The formula (e) can obtain that the pile spacing S of the prefabricated hollow pile meets the following requirements:
wherein xi is the compression coefficient of the swelling reducing and water permeable layer, and can be 0.3-0.8 according to the material property,
alpha is the volume expansion rate of the expansive soil and is determined according to the geotechnical test.
Preferably, the calculation formula of the allowable bearing capacity [ P ] of the single pile is as follows:
wherein, U represents the perimeter of the convex pile body part;
q i indicating the allowable side resistance (kPa) of the convex pile body pile part Zhou Di i layer soil;
l i representing the total thickness of the convex pile body part in the pile Zhou Di i layers of soil;
a represents the vertical projection area of the pile toe;
Q p represents pile tip base layer allowable end resistance (kPa);
the allowable bearing capacity P of the single pile satisfies the following formula, and the pile body section number n is determined by the following formula:
[P]≥P (h)
the pile length L satisfies the depth L of the atmospheric influence layer or more 0 ：
L≥L 0 (i)。
And (d) when the pile length L obtained by calculation does not meet the requirements of the formulas (g) - (i), re-confirming the parameter values and carrying out checking calculation on the parameters (c) - (f).
The cavity is considered to have the function of a water collecting well, and the diameter c is preferably 0.15-0.25m.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. The reinforcing structure is characterized by being a prefabricated concave-convex hollow pile, the prefabricated concave-convex hollow pile comprises a pile head (1), a pile tip (2) and at least one pile body (3) which are connected in a segmented mode, a cavity (4) is formed in the prefabricated concave-convex hollow pile along the axis direction of the prefabricated concave-convex hollow pile, each pile body (3) respectively comprises a convex pile body and a concave pile body (31) along the axis direction, a convex pile body is arranged between every two adjacent concave pile bodies (31), and a plurality of water permeable holes (7) are formed in the concave pile bodies (31) in the circumferential direction; the concave pile body (31) is also provided with an expansion-reducing permeable layer (5) in the circumferential direction.
2. Reinforcement structure against foundation expansion and contraction according to claim 1, characterized in that in said prefabricated male-female hollow pile, said male shaft comprises a first protrusion (32) and a second protrusion (33), said first protrusion (32) being located at the end of said shaft (3), said second protrusion (33) being located in the middle of said shaft (3), between said first protrusion (32) and said second protrusion (33) being a female shaft (31).
3. Reinforcement structure against foundation expansion and contraction deformations according to claim 2, characterized in that each section of said pile (3) comprises at least two repeating units, each having a height H 0 The height of the second projection (33) is H 3 The height of the concave pile body (31) is H 4 And the relationship between the three accords with:
H 0 ＝H 3 +H 4 (a)；
wherein H 3 The range of (A) is 0.4 to 0.6m; h 4 The range of (A) is 0.4 to 0.6m.
4. Reinforcement structure against foundation expansion and contraction deformations according to claim 3, characterized in that said pile head (1) has a height H 1 The height of the pile tip (2) is H 2 ；H 1 The value range of (a) is 0.4-0.5m; h 2 The value range of (A) is 0.4-0.5m; the height L of the prefabricated concave-convex hollow pile is calculated according to the following formula:
L＝H 1 +H 2 +nH 0 (b)。
5. the reinforcement structure against foundation expansion and contraction deformation according to claim 1, wherein a drain pipe (6) is provided in the cavity (4), one end of the drain pipe (6) is connected to the bottom of the cavity (4), and the other end of the drain pipe (6) is connected to a pumping and drainage system on the ground.
6. The reinforcement structure against foundation expansion and contraction deformation according to claim 1, wherein the water-permeable expansion-reducing layer (5) is a flexible elastomer, and the water-permeable expansion-reducing layer (5) is wrapped around the concave pile body (31); the thickness of the section of the expansion-reducing water-permeable layer (5) is 0.2-0.8 m.
7. The reinforcement structure against foundation expansion and contraction deformation according to any one of claims 1 to 6, wherein the reinforcement structure further comprises an expansion reduction buffer layer (8) and a reinforcement layer (9), the reinforcement layer (9) is arranged on the pile head of the prefabricated concave-convex hollow pile, and the reinforcement layer (9) is a reinforced concrete slab; the expansion reduction buffer layer (8) is arranged below the reinforcing layer (9), and the expansion reduction buffer layer (8) is arranged between the pile heads (1).
8. A method of designing a reinforcing structure against foundation expansion and contraction deformation according to claim 7, comprising the steps of:
step 1: designing the structure of the prefabricated concave-convex hollow pile, and planning the structural parameters of the prefabricated concave-convex hollow pile to include: the external diameter D of the convex pile body, the external diameter D of the concave pile body and the internal diameter c of the cavity are specified to take the minimum repeating unit in a single pile body as a calculating unit, wherein the height of each repeating unit is H 0 The height of the second projecting part is H 3 The height of the concave pile body is H 4 ；
And 2, step: carrying out expansion and shrinkage deformation resistance checking calculation on the prefabricated concave-convex hollow pile by using the calculating unit, and determining a pile spacing S in a reasonable range;
and step 3: when the pile spacing S does not accord with the reasonable value range, readjusting the parameter value in the step 1 to calculate until the pile spacing S is determined;
and 4, step 4: determining the allowable bearing capacity P of the single pile according to the upper load of the prefabricated concave-convex hollow pile and the pile spacing S;
and 5: checking and calculating the bearing capacity of a single pile and the depth L of an atmospheric influence layer according to the size parameters of a pile body of the prefabricated concave-convex hollow pile 0 And comprehensively determining the pile length L.
9. The method for designing a reinforcing structure capable of resisting foundation expansion and contraction deformation according to claim 8, wherein the concrete calculation process of the pile spacing S comprises the following steps:
step 21: determining a compressible space M of a pile body:
step 22: determining and calculating the volume N of soil around the unit pile:
the expansion and shrinkage deformation of the foundation soil of the prefabricated concave-convex hollow pile meets the condition that M zeta is more than or equal to N alpha (e), and the pile spacing S of the prefabricated concave-convex hollow pile meets the following conditions:
wherein xi is the compression coefficient of the expansion-reducing drainage net core, and can be 0.3-0.8 according to the material property, and alpha is the volume expansion rate of the foundation (expansive soil) and is determined according to the geotechnical test.
10. The method for designing a reinforcing structure against foundation expansion and contraction deformation according to claim 8, wherein the allowable bearing capacity [ P ] of a single pile is calculated by the formula:
wherein, U represents the perimeter of the convex pile body part;
q i the allowable side resistance (kPa) of the convex pile body pile Zhou Di i layer soil is shown;
l i representing the total thickness of the convex pile body part in the pile Zhou Di i layers of soil;
a represents the vertical projection area of the pile tip;
Q p indicating pile tip floor allowable end resistance (kPa);
the single pile allows the bearing capacity P to satisfy the following formula: [ P ]]The number n of the pile body sections is determined according to the formula, wherein the formula is more than or equal to P (h); wherein, P is the upper load to be borne by the single pile; the pile length L satisfies the depth L of the atmospheric influence layer or more 0 ；
L≥L 0 (i)
When the pile length L obtained by calculation does not meet the requirements of the formulas (g) - (i), readjusting the parameter values to carry out checking calculation of the formulas (c) - (f);
the pile length L satisfies the depth L of the atmosphere influence layer 0 (ii) a And (e) when the pile length L obtained by calculation does not meet the requirements of the formulas (f) - (h), re-confirming the parameter values and carrying out checking calculation on the parameters (c) - (e).
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