CN115419056B - Reinforcing structure for resisting expansion and shrinkage deformation of foundation and design method - Google Patents
Reinforcing structure for resisting expansion and shrinkage deformation of foundation and design method Download PDFInfo
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- CN115419056B CN115419056B CN202211096696.3A CN202211096696A CN115419056B CN 115419056 B CN115419056 B CN 115419056B CN 202211096696 A CN202211096696 A CN 202211096696A CN 115419056 B CN115419056 B CN 115419056B
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- 230000003014 reinforcing effect Effects 0.000 title claims abstract description 25
- 238000000034 method Methods 0.000 title claims abstract description 20
- 238000013461 design Methods 0.000 title abstract description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 24
- 239000002689 soil Substances 0.000 claims abstract description 22
- 230000008602 contraction Effects 0.000 claims abstract description 16
- 230000008961 swelling Effects 0.000 claims abstract description 10
- 238000004364 calculation method Methods 0.000 claims description 28
- 230000002787 reinforcement Effects 0.000 claims description 12
- 239000000463 material Substances 0.000 claims description 6
- 239000011150 reinforced concrete Substances 0.000 claims description 6
- 238000005086 pumping Methods 0.000 claims description 5
- 238000010276 construction Methods 0.000 claims description 4
- 229920001971 elastomer Polymers 0.000 claims description 4
- 239000000806 elastomer Substances 0.000 claims description 4
- 230000006835 compression Effects 0.000 claims description 3
- 238000007906 compression Methods 0.000 claims description 3
- 239000004567 concrete Substances 0.000 claims description 3
- 230000008569 process Effects 0.000 claims description 3
- 238000012360 testing method Methods 0.000 claims description 3
- 239000011800 void material Substances 0.000 claims 1
- 239000003673 groundwater Substances 0.000 description 11
- 239000004746 geotextile Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000004062 sedimentation Methods 0.000 description 2
- 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
- 239000012466 permeate Substances 0.000 description 1
- 238000003908 quality control method Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 208000024891 symptom Diseases 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 reinforcing structure for resisting swelling deformation of a foundation and a design method. 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, the pile bodies are provided with concave pile bodies at intervals along the length direction of the pile bodies, 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 of 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 positions of the concave pile bodies are also provided with a circle of expansion-reducing water permeable layer; the expansion-reducing permeable layer can adapt to the expansion or contraction of the foundation, and the expansion-reducing permeable layer plays a role in supporting the soil body around the piles on one hand, so that the holes are prevented from collapsing, and on the other hand, a deformation space is reserved for the expansion of the foundation, so that the purpose of preventing the foundation from being deformed by arching is achieved.
Description
Technical Field
The invention belongs to the technical field of geotechnical engineering foundation treatment, and particularly relates to a reinforcing structure for resisting swelling deformation of a foundation and a design method.
Background
Expansive soil is widely distributed worldwide, and more than about 40 countries and regions having expansive soil have been found. The most typical characteristics of expansive soil are water-absorbing expansion, water-loss shrinkage, repeated expansion and contraction deformation, which is a serious challenge for foundation treatment under high-speed railway millimeter-grade deformation control.
With the increase of the open operation mileage and operation time in China, structures such as high-speed railway beds and tunnels in the expansive soil areas gradually generate the phenomenon of arch deformation, the arch deformation value is beyond the allowable range of railway smoothness, railway office work departments usually adopt the manners of tamping by a large machine, fine adjustment of the track and the like to treat the structures, but the problems can not be fundamentally solved, the normal operation of the high-speed railway is seriously influenced, and the manpower, material resources and financial resources required to be input by maintenance work are large.
Disclosure of Invention
The invention aims at: aiming at the defect that the prior art adopts the modes of tamping by a large machine or fine adjustment of a track and the like to prevent the foundation from arching deformation and cure the symptoms and the root causes, the invention provides a structure and a design method which can prevent the occurrence of excessive settlement of the subgrade while preventing the occurrence of arching deformation of the subgrade, tunnels and other structures in the expansive rock-soil area, and has the advantages of convenient construction, easy quality control and economic and reasonable scheme.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
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 section of 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 pile body, each section of pile body comprises a convex pile body and a concave pile body along the axis direction, a convex pile body is arranged between every two adjacent concave pile bodies, and a plurality of water permeable holes are formed in the concave pile body along the circumferential direction; the concave pile body circumference is also provided with an expansion-reducing permeable layer.
The invention provides a prefabricated concave-convex hollow pile structure for resisting the expansion and contraction deformation of a foundation, 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 of a concave-convex structure, a plurality of water permeable holes are formed in the concave pile body, and a circle of expansion-reducing water permeable layer is wrapped outside the concave pile body in the circumferential direction; when the expansion-reducing permeable layer expands with the foundation, the expansion-reducing permeable layer can elastically deform to adapt to the expansion deformation of the foundation. The setting of the expansion-reducing permeable layer plays a role in supporting the soil body around the pile on one hand, avoids hole collapse, reserves a deformation space for the expansion of the foundation on the other hand, and plays a role in preventing the foundation from being deformed due to the upward arch caused by the expansion. Furthermore, the groundwater can enter the hollow pile through the expansion-reducing permeable layer and the permeable holes, and the hollow pile is pumped, so that the purpose of draining groundwater is achieved, and the expansion-reducing permeable layer also indirectly plays a role in draining groundwater.
The prefabricated concave-convex hollow pile comprises a pile head, a pile body and a pile tip, wherein the pile body and the pile tip are of concave-convex structures, and the pile head, the pile body and the pile tip are manufactured separately, so that standardized and efficient production can be realized, and the pile is convenient to transport. The prefabricated concave-convex hollow pile can be spliced according to different reinforcement depths on site, and construction is more flexible and convenient. Groundwater in the foundation can enter the cavity of the prefabricated concave-convex hollow pile through the water permeable holes of the pile body, pumping is performed when necessary, and the groundwater level is reduced, so that the purpose of expansion reduction is achieved.
Preferably, in the prefabricated concave-convex hollow pile, each pile body comprises a first protruding portion and a second protruding portion, the first protruding portion is located at the end of the pile body, the second protruding portion is located at the middle of the pile body, and the concave pile body is arranged between the first protruding portion and the second protruding portion.
In the preferred technical scheme of the invention, the two adjacent concave pile bodies are of a convex structure relative to the concave pile bodies, and the convex pile bodies can be well contacted with the foundation, so that the load born on the upper parts is uniformly transferred to the foundation, and the bearing effect is realized. A concave-convex pile body structure not only can play a role in resisting the swelling deformation of the foundation, but also can serve as foundation reinforcement and play a role in controlling sedimentation.
Preferably, each pile body comprises at least two or more repeated computing units, and the height of each computing unit is H 0 The height of the second protruding part (the convex pile body) is H 3 The height of each concave pile body is H 4 The relation among the three accords with:
H 0 ＝H 3 +H 4 (a)；
wherein H is 3 The range of (2) is 0.4-0.6 m; h 4 The range of (2) is 0.4-0.6 m.
Preferably, the pile head has a height H 1 The height of the pile tip is H 2 ；H 1 The value range of (2) is 0.4-0.5m; h 2 The range of the value of (2) 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 permeable layer is a flexible elastomer and is wrapped around the concave pile body; preferably, the expansion-reducing water permeable layer is wrapped with water permeable geotextile to play a role in reverse filtration and drainage. The section thickness of the expansion-reducing permeable layer is between 0.2 and 0.8m.
Preferably, the pile tip is of a solid truncated cone-shaped structure, the pile body and the pile head are of cylindrical structures, and the pile head and the pile body are provided with cavities along the axial direction of the pile head and the pile head.
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; d has a value range of 0.6-1.2 m; d has a value of 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 water pumping and draining system on the ground. When the groundwater level needs to be reduced, water can be pumped through the drain pipe, so that the purpose of reducing the groundwater level is achieved.
Preferably, the reinforcement structure further comprises an expansion buffer layer or a reinforcement layer, the reinforcement layer is arranged on the pile head of the prefabricated hollow pile, and the reinforcement layer is a reinforced concrete slab.
A method for designing a reinforced structure for resisting foundation expansion and contraction deformation comprises the following steps:
step 1: designing the structure of a prefabricated hollow pile, and drawing structural parameters of the prefabricated hollow pile: respectively comprise a convex partThe outer diameter D of the pile body, the outer diameter D of the concave pile body and the inner diameter c of the cavity define that the minimum repeated unit in a single pile body is taken as a calculation unit, wherein the height of each calculation unit is H 0 The height of the second protruding part is H 3 The height of the concave pile body is H 4 ；
Step 2: carrying out expansion and contraction deformation resistance checking calculation on the prefabricated hollow pile by using the calculation unit, and determining a pile spacing S in a reasonable range;
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;
step 4: determining a single pile allowable bearing capacity P according to the upper load of the prefabricated hollow pile and the pile spacing S;
step 5: according to pile body dimension parameters of the prefabricated hollow pile, single pile bearing capacity checking calculation and atmosphere influence layer depth L 0 And comprehensively determining the final pile length L.
Preferably, the concrete calculation process of the pile spacing S includes:
determining a pile body compressible space M:
determining the volume N of the surrounding soil of the calculation unit pile:
the prefabricated hollow pile can resist the expansion and contraction deformation of the foundation and can meet the requirement that Mζ is more than or equal to Nα (e)
The pile spacing S of the prefabricated hollow piles can be obtained according to the formula (d):
wherein, xi is the compression coefficient of the expansion-reducing permeable layer, can take a value of 0.3-0.8 according to the material property,
alpha is the volume expansion rate of the foundation (expansive soil) and is determined according to a geotechnical test.
Preferably, the calculation formula of the allowable bearing capacity [ P ] of the single pile is as follows:
wherein U represents the circumference of the convex pile body part;
q i representing allowable side resistance (kPa) of the i-th layer soil around the pile body portion;
l i representing the total thickness of the convex pile body part in the ith layer of soil around the pile;
a represents the vertical projection area of the pile tip;
Q p represents pile tip bottom allowable end resistance (kPa);
the allowable bearing capacity [ P ] of the single pile is required to meet the following formula, so that the pile body node number n is determined:
[P]≥P (h)
wherein P is the upper load which the single pile needs to bear.
The pile length L is greater than or equal to the depth L of the atmosphere influence layer 0 ；
L≥L 0 (i)
And (3) when the calculated pile length L 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 reinforcing structure for resisting the expansion and contraction deformation of the foundation is constructed according to the following method:
s1, prefabricating concave-convex hollow piles;
s2, cleaning and leveling the field;
s3, positioning, mechanical hole guiding and pile sinking;
s4, arranging a drain pipe in the hollow pile;
s5, applying an upper expansion reducing buffer layer;
s6, constructing a pile top reinforced concrete slab or a reinforced cushion layer;
s7, performing upper roadbed or structure.
In summary, due to the adoption of the technical scheme, the beneficial effects of the invention are as follows:
the invention provides a prefabricated concave-convex hollow pile structure, which is a segmented prefabricated structural member as a whole, wherein convex pile bodies and concave pile bodies are arranged at intervals to enable the whole hollow pile to be of a concave-convex structure, a plurality of water permeable holes are formed in the concave pile bodies, and a circle of expansion-reducing water permeable layer is wrapped on the concave pile bodies in the circumferential direction; when the expansion-reducing permeable layer expands with the foundation, the expansion-reducing permeable layer can be compressed and thinned, so that the expansion-reducing permeable layer adapts to the expansion of the foundation; when the foundation contracts, the water permeable layer with reduced expansion can recover the deformation of itself compressed. The setting of the expansion-reducing permeable layer plays a role in supporting the soil body around the pile on one hand, avoids hole collapse, reserves a deformation space for the expansion of the foundation on the other hand, and plays a role in preventing the foundation from being deformed due to the upward arch caused by the expansion. Furthermore, the groundwater can enter the hollow pile through the expansion-reducing permeable layer and the permeable holes, and the hollow pile is pumped, so that the purpose of draining groundwater is achieved, and the expansion-reducing permeable layer also indirectly plays a role in draining groundwater.
The prefabricated structural member comprises the pile head, the multi-section concave-convex pile body and the pile tip, and can be manufactured separately, so that standardized and efficient production can be realized, and the prefabricated structural member is convenient to transport. The prefabricated hollow pile can be spliced according to different reinforcement depths on site, and the construction is more flexible and convenient. Groundwater in the foundation can be discharged into the cavity of the prefabricated hollow pile through the water permeable holes of the pile body, pumping is performed if necessary, and the water content of the foundation layer is reduced, so that the purpose of expansion reduction is achieved.
In the technical scheme of the invention, the two adjacent concave pile bodies are of a convex structure relative to the concave pile bodies, and the convex pile bodies can be well contacted with the foundation, so that the load born on the upper parts is uniformly transferred to the foundation, and the bearing effect is realized. A concave-convex pile body structure not only can play a role in resisting the swelling deformation of the foundation, but also can serve as foundation reinforcement and play a role in controlling sedimentation.
The reinforced concrete plate is arranged at the pile top, and forms a reinforcement technology for resisting the expansion and contraction deformation of the foundation together with the concave-convex hollow pile and the expansion reducing layer, so that the reinforced concrete plate is particularly suitable for the foundation which is easy to generate expansion and contraction deformation, such as expansive soil. After the concave-convex hollow pile is used for reinforcing the foundation, the expansion and contraction deformation of the foundation can be overcome, the foundation is prevented from arching up, the upper load can be borne, the foundation settlement is controlled, and the purpose of resisting the expansion and contraction deformation of the foundation is achieved.
Drawings
FIG. 1 is a schematic structural view of a prefabricated concave-convex hollow pile according to 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 the reinforcement structure A of the present invention;
FIG. 4 is a schematic dimensional view of a single pile body according to the present invention;
icon: 1-pile head; 2-pile tip; 3-pile body; 4-cavity; 5-an expansion-reducing permeable layer; 31-concave pile body; 32-first bulge, 33-second bulge, 6-drain pipe, 7-hole that permeates water, 8-buffer layer that subtracts swell, 9-reinforcement layer, 10-load.
Detailed Description
The present invention will be described in detail with reference to the accompanying drawings.
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Example 1
As shown in fig. 1 and 2-3, the reinforcement structure is 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 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 in 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 circumference of the concave pile body 31 is also provided with an expansion-reducing permeable layer 5. Specifically, the expansion-reducing permeable layer 5 is a flexible elastomer, and the expansion-reducing permeable layer 5 is wrapped around the concave pile body 31. More specifically, the section thickness of the expansion-reducing permeable layer 5 is between 0.2 and 0.8m, the expansion-reducing permeable layer is composed of permeable geotextile and a drainage net core, the expansion-reducing permeable layer is made of geotextile materials, the expansion-reducing permeable layer has good permeability, and the net core is a low-strength elastomer. When the expansion-reducing permeable layer 5 expands with the foundation, the expansion-reducing permeable layer 5 can be compressed and thinned, and when the foundation contracts, the expansion-reducing permeable layer 5 can recover the compressed deformation of the expansion-reducing permeable layer, so that the deformation balance between the foundation and the pile body is achieved, and the foundation is prevented from arching and deforming.
Specifically, in this embodiment, the structure of the single pile body is shown in fig. 4: each section of pile body 3 is provided with a protruding part at two ends, protruding parts are arranged at intervals in the middle, the protruding parts of the end parts are first protruding parts 32, the protruding parts of the middle are second protruding parts 33, and a concave pile body 31 is arranged between the first protruding parts 32 and the second protruding parts 33. Wherein the height of the first protrusion 32 is H 3 2, the height of the concave pile body is H 4 The height of the second protrusion 33 is H 3 And 2, each pile section 3 comprises a plurality of repeated calculation units. The size of the individual computing units corresponds to the following formula: h 0 ＝H 3 +H 4 (a)；
H 3 The range of (2) is 0.4-0.6 m; h 4 The range of (2) is 0.4-0.6 m.
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 (2) is 0.4-0.5m; h 2 The value range of (2) 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 D; d has a value range of 0.6-1.2 m; d has a value range of 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. 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 a water pumping and draining system on the ground. The pile head 1 is provided with an expansion buffer layer 8, and the expansion 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 piles together form a foundation reinforcing structure, and bear load 10 from an upper roadbed or a structure.
In the embodiment, the pile spacing, pile body strength, length and outer diameter of concave and convex pile body sections, an expansion-reducing permeable layer and the like of the concave-convex hollow pile are comprehensively calculated and determined according to the conditions of the strength, the expansion and shrinkage of foundation soil, upper load interception and the like.
Example 2
A method for designing a reinforced structure for resisting foundation expansion and contraction deformation comprises the following steps:
step 1: designing the structure of a prefabricated hollow pile, and drawing structural parameters of the prefabricated hollow pile: the method comprises the steps of respectively comprising a convex pile body outer diameter D, a concave pile body outer diameter D and a cavity inner diameter c, and defining a minimum repeated unit in a single pile body as a calculation unit, wherein the height of each calculation unit is H 0 The height of the second protruding part is H 3 The height of the concave pile body is H 4 ；
Step 2: carrying out expansion and contraction deformation resistance checking calculation on the prefabricated hollow pile by using the calculation unit, and determining a pile spacing S in a reasonable range; wherein, the reasonable pile spacing S is preferably 3-5 times of the outer diameter D of the convex pile body part.
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;
step 4: determining a single pile allowable bearing capacity P according to the upper load of the prefabricated hollow pile and the pile spacing S;
step 5: according to pile body dimension parameters of the prefabricated hollow pile, single pile bearing capacity checking calculation and atmosphere influence layer depth L 0 And comprehensively determining the final pile length L.
Preferably, the concrete calculation process of the pile spacing S includes:
determining the compressible space M of the pile body 3:
determining the volume N of the surrounding soil of the calculation unit pile:
the prefabricated hollow pile can resist the expansion and contraction deformation of the foundation and can meet the requirement that Mζ is more than or equal to Nα (e)
The pile spacing S of the prefabricated hollow piles can be obtained according to the formula (e):
wherein, xi is the compression coefficient of the expansion-reducing permeable layer, can take a value of 0.3-0.8 according to the material property,
alpha is the expansion rate of the expansion soil volume and is determined according to a geotechnical test.
Preferably, the calculation formula of the allowable bearing capacity [ P ] of the single pile is as follows:
wherein U represents the circumference of the convex pile body part;
q i representing allowable side resistance (kPa) of the i-th layer soil around the pile portion of the male pile body;
l i representing the total thickness of the convex pile body part in the ith layer of soil around the pile;
a represents the vertical projection area of the pile tip;
Q p represents pile tip bottom allowable end resistance (kPa);
the allowable bearing capacity P of the single pile meets the following formula, so that the pile body node number n is determined:
[P]≥P (h)
the pile length L is greater than or equal to the depth L of the atmosphere influence layer 0 ：
L≥L 0 (i)。
And (3) when the calculated pile length L does not meet the requirements of the formulas (g) - (i), reconfirming the parameter values to carry out checking calculation of the formulas (c) - (f).
The cavity is preferably 0.15-0.25m in diameter c, considering the function of the water collection well.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.
Claims (7)
1. A method for designing a reinforcing structure for resisting expansion and contraction deformation of a foundation is characterized by comprising the following steps:
step 1: the method comprises the steps of designing a structure of 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 mode, a cavity (4) is formed in the prefabricated concave-convex hollow pile along the axial direction of the prefabricated concave-convex hollow pile, each pile body (3) comprises a convex pile body and a concave pile body (31) along the axial 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) along the circumferential direction; the circumference of the concave pile body (31) is also provided with an expansion-reducing water-permeable layer (5); the expansion-reducing permeable layer (5) is a flexible elastomer, and the expansion-reducing permeable layer (5) is wrapped around the concave pile body (31); the expansion-reducing water permeable layer (5) comprises an expansion-reducing drainage net core,
in the prefabricated concave-convex hollow pile, the convex pile body comprises a first protruding part (32) and a second protruding part (33), the first protruding part (32) is positioned at the end part of the pile body (3), the second protruding part (33) is positioned at the middle part of the pile body (3), and a concave pile body (31) is arranged between the first protruding part (32) and the second protruding part (33);
the construction parameters of the prefabricated concave-convex hollow pile are planned to include: the outer diameter D of the convex pile body, the outer diameter D of the concave pile body and the inner diameter c of the cavity define that the minimum repeating unit in a single pile body is taken as a calculating unit, wherein the height of each repeating unit is H 0 The height of the second protruding part is H 3 The height of the concave pile body is H 4 ；
Step 2: carrying out expansion and contraction deformation resistance checking calculation on the prefabricated concave-convex hollow pile by using the calculation unit, and determining a pile spacing S in a reasonable range; the concrete calculation process of the pile spacing S comprises the following steps:
step 21: determining the compressible void of a pile bodyM:
step 22: determining the volume N of the surrounding soil of the calculation unit pile:
the swelling deformation of the prefabricated concave-convex hollow pile for resisting foundation soil is enabled to meet that Mζ is larger than or equal to Nα (e), and the pile spacing S of the prefabricated concave-convex hollow pile is met:
wherein, xi is the compression coefficient of the expansion-reducing drainage net core, the value is 0.3-0.8 according to the material property, alpha is the volume expansion rate of the foundation, and is determined according to a geotechnical test;
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;
step 4: determining the allowable bearing capacity P of a single pile according to the upper load of the prefabricated concave-convex hollow pile and the pile spacing S;
step 5: according to pile body dimension parameters of prefabricated concave-convex hollow pile, single pile bearing capacity checking calculation and atmosphere influence layer depth L 0 And comprehensively determining the pile length L.
2. The method for designing a reinforcement structure against foundation dilatation deformation according to claim 1, wherein the calculation formula of the allowable bearing capacity [ P ] of a single pile is:
wherein U represents the circumference of the convex pile body part;
q i the allowable side resistance of the ith layer of soil around the pile body of the convex pile is expressed in kPa;
l i representing the total thickness of the convex pile body part in the ith layer of soil around the pile;
a represents the vertical projection area of the pile tip;
Q p the allowable end resistance of the pile tip bottom layer is expressed in units of kPa;
the mono-pile allowable bearing capacity P satisfies the following formula: [ P ]]More than or equal to P (h), thereby determining the pile section number n; wherein P is the upper load to be borne by the single pile; the pile length L is greater than or equal to the depth L of the atmosphere influence layer 0 ；
L≥L 0 (i)
When the calculated pile length L does not meet the requirements of the formulas (g) - (i), readjusting the parameter values to carry out checking calculation of the formulas (c) - (f);
and (3) when the calculated pile length L does not meet the requirements of the formulas (f) - (h), reconfirming the parameter values to carry out the checking calculation of the formulas (c) - (e).
3. A method of designing a reinforcing structure resistant to dilatation and deformation of the foundation according to claim 1, characterized in that each pile (3) comprises at least two repeating units, each of height H 0 The height of the second protruding part (33) is H 3 The height of the concave pile body (31) is H 4 The relation among the three accords with:
H 0 ＝H 3 +H 4 (a)；
wherein H is 3 The range of (2) is 0.4-0.6 m; h 4 The range of (2) is 0.4-0.6 m.
4. A method of designing a reinforcing structure resistant to dilatation and deformation of the foundation according to claim 3, characterized in that the pile head (1) has a height H 1 The height of the pile tip (2) is H 2 ；H 1 The value range of (2) is 0.4-0.5m; h 2 The value range of (2) 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)；
wherein n represents the number of pile body (3) joints.
5. The method for designing a reinforcing structure for resisting swelling deformation of foundation according to claim 1, wherein 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 a water pumping and draining system on the ground.
6. The method for designing a reinforcing structure resistant to swelling deformation of foundation according to claim 1, wherein the section thickness of the swelling water permeable layer (5) is 0.2-0.8 m.
7. The method for designing a reinforcing structure for resisting swelling deformation of a foundation according to any one of claims 1 to 6, wherein the reinforcing structure further comprises a swelling buffer layer (8) and a reinforcing layer (9), the reinforcing layer (9) is arranged above the pile head of the prefabricated concave-convex hollow pile, and the reinforcing layer (9) is a reinforced concrete slab; the expansion reducing buffer layer (8) is arranged below the reinforcing layer (9), and the expansion reducing buffer layer (8) is arranged between the pile heads (1).
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