CN115506186B

CN115506186B - SAP pile rib composite structure for controlling uneven settlement of embankment and construction method thereof

Info

Publication number: CN115506186B
Application number: CN202211184187.6A
Authority: CN
Inventors: 丁鲁强; 肖成志; 叶云雪; 张学元
Original assignee: Hebei University of Technology
Current assignee: Hebei University of Technology
Priority date: 2022-09-27
Filing date: 2022-09-27
Publication date: 2023-05-26
Anticipated expiration: 2042-09-27
Also published as: CN115506186A

Abstract

The invention discloses an SAP pile rib composite structure for controlling uneven settlement of a embankment and a construction method thereof. The composite structure comprises a miniature pile, a CFG pile, a recycled aggregate crushed stone cushion layer, a steel-plastic geogrid, high-strength foam light soil and a beam grid system. The invention inherits the design concept of both hardness and softness, changes the original single pile type system into a micro pile-CFG pile mixed pile system, and improves the self-maintenance function of pile body concrete and the bearing capacity of the pile body, reduces the total settlement of pile foundation and improves the durability, the seepage resistance and the corrosion resistance of the pile body material by adding the self-developed SAP mixture; the integral working performance of the pile foundation is enhanced through the connecting beam, and the bottom effect of the steel-plastic geogrid and the load-reducing effect of the high-strength foam light soil are added to realize the heavy distribution of the dead weight load and the traffic dynamic load of the overlying structure and relieve the uneven settlement of the service embankment.

Description

SAP pile rib composite structure for controlling uneven settlement of embankment and construction method thereof

Technical Field

The invention belongs to the field of pile-supported reinforced embankments, and particularly relates to an SAP pile-rib composite structure for controlling uneven settlement of an embankment and a construction method thereof, which are suitable for engineering construction of highway embankments in soft soil areas.

Background

Saturated soft clay such as silt and silt soft soil is distributed in a large amount in eastern coastal areas of China, and the soil has engineering characteristics of high water content, high compressibility and low strength, so far, the engineering problem which needs to be solved in the highway industry of China is still urgent. The pile-supported reinforced embankment takes the broken stone reinforced cushion layer as a horizontal reinforcement body and rigid piles as vertical reinforcement bodies, can comprehensively exert the dual effects of horizontal reinforced transverse constraint soil mass and vertical pile peripheral soil mass compaction, and is widely applied to highway engineering construction in soft soil areas.

Pile foundation main body of Pile-supported reinforced embankment adopts Cement-Fly ash-Gravel (CFG) Pile with diameter of 350-600 mm and Pile spacing of 1.5-2.5 m, belonging to low-strength concrete Pile. The CFG piles and the inter-pile soil and mattress layers together form the CFG pile composite foundation. At present, the following disadvantages exist:

(1) Due to the limitation of pile body bearing capacity and zero connectivity among piles, the embankment is extremely easy to generate uneven settlement under the action of heavy traffic load;

(2) The hydration reaction inside the cast-in-situ CFG pile is not uniform, and local weakening of the section strength of the pile body is easy to cause;

(3) The groundwater in coastal areas contains a large amount of salt substances, so that certain corrosiveness is generated on CFG piles during working, and the quality of the piles is easy to lose;

(4) The larger pile diameter and smaller pile spacing can cause the increase of the material consumption of the pile body and the construction cost, and simultaneously, the disturbance to the surrounding soil body during the construction of the pile body is also intangibly increased, which is not beneficial to the exertion of the bearing capacity of the soil body around the pile body.

The patent document with application number 201010533647.2 discloses a method for treating soft soil roadbed by using a novel pile-supported reinforcement technology, which solves the problems of overlarge lateral displacement, sedimentation and uneven sedimentation of roadbed and embankment by using a mode of fixing geosynthetic materials and pile caps, but does not make any improvement on a pile body, and the pile body is a main contributor bearing an overlying static load and a vehicle dynamic load, and the aim of controlling the uneven sedimentation of the soft soil roadbed can not be achieved by simply adding reinforcement materials.

Therefore, it is necessary to provide a novel pile-supporting reinforcement structure to achieve: (1) the load capacity and the connection performance of the CFG pile are improved, (2) the uniformity of hydration reaction in the pile is promoted, (3) the durability and the corrosion resistance of the pile body are improved, (4) the pile distribution distance is reduced, and the construction cost is saved.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide an SAP pile rib composite structure for controlling uneven settlement of an embankment and a construction method thereof.

The technical scheme for solving the technical problem of the composite structure is that the SAP pile rib composite structure for controlling the uneven settlement of the embankment is provided, and is characterized by comprising micro piles, CFG piles, recycled aggregate crushed stone cushions, steel-plastic geogrids, high-strength foam lightweight soil and a beam grid system;

arranging the micro piles and the CFG piles according to triangles; the pile body of the miniature pile is arranged in the soft soil foundation, the pile end is arranged in the bearing layer under the expansion, and the overground pile section is positioned above the surface of the soft soil foundation; pile bodies of the CFG piles are arranged in the soft soil foundation, and overground pile sections are positioned above the surface of the soft soil foundation; pile tops of the micro pile and the CFG pile are positioned on the same horizontal plane; pile bodies of the micro pile and the CFG pile are formed by pouring a reinforcement cage and an SAP mixture;

a regenerated aggregate broken stone cushion layer is paved at a non-pile foundation position on the surface of the soft soil foundation, and the upper surface of the regenerated aggregate broken stone cushion layer is flush with pile tops of the micro piles and the CFG piles; a steel-plastic geogrid is paved above the mini-type piles, the CFG piles and the recycled aggregate broken stone cushion layer; the steel skeleton of the connecting beam is built above the steel-plastic geogrid, and the steel skeleton at the tops of the micro piles and the CFG piles penetrate through meshes of the steel-plastic geogrid and are connected with the steel skeleton of the connecting beam; the poured connecting beams form a beam grid system; high-strength foam light soil is poured in gaps among connecting beams in the beam grid system, and the upper surface of the high-strength foam light soil is flush with the top surface of the beam grid system; and a steel-plastic geogrid is paved above the beam grid system and the high-strength foam lightweight soil in the beam grid system.

The technical scheme for solving the technical problem of the method is that the invention provides a construction method of an SAP pile rib composite structure for controlling uneven settlement of a embankment, which is characterized by comprising the following steps:

step 1, according to engineering geological survey data, respectively determining pile length, pile diameter, pile spacing and pile position information of each of the micro pile and the CFG pile so as to meet the bearing capacity requirements of an overlying structure on a soft soil foundation under the action of dead load and traffic dynamic load, and respectively determining components of SAP (super-absorbent polymer) mixtures of the micro pile and the CFG pile;

step 2, performing surface cleaning and leveling work on the site of the planned road embankment to finish the approach preparation work of related materials, equipment and personnel;

step 3, positioning, drilling and clearing holes at the position where the CFG pile is arranged, and building a pile body template above the surface of the soft soil foundation for pouring the overground pile section; preparing an SAP mixture according to design requirements, and pumping the SAP mixture into pile holes of the CFG piles; after the actual feeding amount is not less than the designed feeding amount, inserting a steel reinforcement framework of the CFG pile to the designed depth at the center position of the top of the CFG pile, pouring SAP mixture into the pile body template to be filled, and reserving the steel reinforcement framework of part of the CFG pile for being connected with the steel reinforcement framework of the connecting beam; or positioning, drilling and clearing holes at the position where the CFG pile is arranged, and building a pile body template above the surface of the soft soil foundation for pouring the overground pile section; then inserting a steel reinforcement framework penetrating through the pile body of the whole CFG pile at the central position of the CFG pile, preparing an SAP mixture according to design requirements, pumping the SAP mixture into a pile hole of the CFG pile until the pile body template is filled, and reserving the steel reinforcement framework of part of the CFG pile for being connected with the steel reinforcement framework of the connecting beam;

positioning, drilling, reaming and cleaning the pile ends at the position where the miniature pile is arranged, and building a pile body template above the surface of the soft soil foundation for pouring the overground pile section; then inserting a reinforcement cage of the micro pile at the center of the micro pile, preparing an SAP mixture according to design requirements, pumping the SAP mixture into pile holes of the micro pile until the pile body template is filled, and reserving a part of reinforcement cage of the micro pile for connecting with the reinforcement cage of the connecting beam;

after the outer surfaces of the overground pile sections of the CFG piles and the mini piles meet the conditions, removing pile body templates, and curing to form the CFG piles and the mini piles;

step 4, paving recycled aggregate at a non-pile foundation position of the soft soil foundation until the recycled aggregate is flush with pile tops of the micro piles and the CFG piles, and forming a recycled aggregate broken stone cushion layer; the particle size of the recycled aggregate meets the particle size requirement of the crushed stone cushion layer;

step 5, paving steel-plastic geogrids above the micro piles, the CFG piles and the recycled aggregate broken stone cushion layer;

step 6, building a reinforcement cage of the connecting beam above the steel-plastic geogrid, wherein the reinforcement cage at the tops of the micro piles and the CFG piles penetrate through meshes of the steel-plastic geogrid and are bound and connected with the reinforcement cage of the connecting beam; then building a connecting beam template, pouring lightweight aggregate concrete and curing to form a beam grid system;

step 7, dismantling the connecting beam templates, pouring high-strength foam lightweight soil in gaps among connecting beams in the beam grid system until the upper surface of the high-strength foam lightweight soil is flush with the top surface of the beam grid system, and curing according to requirements;

and 8, paving a steel-plastic geogrid above the beam grid system and the high-strength foam light soil in the beam grid system to obtain the SAP pile rib composite structure.

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

(1) The invention inherits the design concept of both hardness and softness, changes the original single pile type system into a micro pile-CFG pile mixed pile system, and improves the self-maintenance function of pile body concrete and the bearing capacity of the pile body, reduces the total settlement of pile foundation and improves the durability, the seepage resistance and the corrosion resistance of the pile body material by adding the self-developed SAP mixture; the integral working performance of the pile foundation is enhanced through the connecting beam, and the bottom effect of the steel-plastic geogrid and the load-reducing effect of the high-strength foam light soil are added to realize the heavy distribution of the dead weight load and the traffic dynamic load of the overlying structure and relieve the uneven settlement of the service embankment.

(2) The invention is provided with two pile types of the micro pile and the CFG pile and adopts triangular arrangement, and by improving the pile type, the inter-pile distance and the layout thereof, the advantages of low construction cost, environmental friendliness, high bearing capacity of the micro pile, strong soil adaptability, easy construction, small disturbance and the like of the CFG pile can be comprehensively exerted, and the aim of saving the construction cost is achieved.

(3) Compared with the conventional SAP, the novel SAP mixture has stronger water absorbability, higher corrosion resistance and weather resistance. The novel SAP mixture is added into the micro pile and CFG pile filler, so that uniformity of humidity state of a pile body can be improved, uniformity of hydration reaction of concrete is promoted, self-curing function of the concrete is realized, and internal strength, load performance, durability and corrosion resistance of the concrete can be improved.

(4) The pile end bearing capacity of the miniature pile can be improved by the bottom expanding structure of the miniature pile, the pile spacing of the CFG pile can be increased by at least 0.5 times by the pile arrangement, and meanwhile, the consumption of pile body materials in unit area is reduced by 15% -25%, so that the construction cost is obviously reduced.

(5) The miniature piles and the CFG piles are tied through wide and flat lightweight aggregate concrete tie beams to form a beam grid system, steel-plastic geogrids are paved on the upper surface and the lower surface of the beam grid system, and high-strength foam lightweight soil is filled in the gaps of the beam grid. The structure system has the advantages of good integrity and uniform sedimentation, can exert the advantages of light weight of lightweight aggregate concrete and foam lightweight soil and the advantages of high tensile strength and low manufacturing cost of the steel-plastic geogrid, remarkably reduces the dead weight of the structure, and realizes the load shedding in the vertical direction and the interlocking constraint in the horizontal direction.

(6) The laying of the basalt fiber concrete layer can exert the advantages of high strength, corrosion resistance and high temperature resistance of basalt fibers, can improve the tensile strength, the shock resistance and the alkali resistance of the concrete protective layer, and is beneficial to the transmission and the durability of the load of the pavement structural layer.

Drawings

FIG. 1 is a construction flow chart of the SAP pile rib composite structure of the present invention;

FIG. 2 is a construction flow chart of the road engineering with SAP pile rib composite structure according to the present invention;

FIG. 3 is a schematic elevation view of a road engineering of the SAP pile composite structure of the present invention;

FIG. 4 is a schematic elevation view of a road engineering incorporating the SAP pile composite structure of the present invention incorporating a sleeved pre-formed micro pile;

FIG. 5 is a schematic cross-sectional view of a road engineering of the SAP pile composite structure of the present invention;

FIG. 6 is an internal reinforcement view of the micropile of the present invention;

FIG. 7 is an internal reinforcement view of the CFG pile of the present invention;

FIG. 8 is a schematic view of the internal reinforcement of the tie beam of the present invention;

FIG. 9 is a schematic view of a micro pile and tie beam node connection and reinforcement according to the present invention;

fig. 10 is a schematic view of the CFG pile and tie beam node connection and reinforcement of the present invention.

In the figure, a soft soil foundation 1, a bearing layer 2, micro piles 3, pile end expanded bottoms 4, CFG piles 5, a recycled aggregate broken stone cushion layer 6, a steel-plastic geogrid 7, a connecting beam 8, a common foam lightweight soil layer 9, a basalt fiber concrete layer 10, a pavement structure layer 11, drainage ditches 12 and prefabricated micro piles 13;

the pile comprises a micro pile stirrup 3-1, a micro pile longitudinal bar 3-2, a CFG pile stirrup 5-1, a CFG pile longitudinal bar 5-2, a connecting beam stirrup 8-1 and a connecting beam longitudinal bar 8-2.

Detailed Description

Specific examples of the present invention are given below. The specific examples are provided only for further details of the present invention and do not limit the scope of the claims.

The invention provides an SAP pile rib composite structure (composite structure for short) for controlling uneven settlement of a embankment, which is characterized by comprising a mini pile 3, a CFG pile 5, a recycled aggregate broken stone cushion layer 6, a steel-plastic geogrid 7, high-strength foam light soil and a beam grid system;

the micro piles 3 and the CFG piles 5 are distributed according to triangles; the pile body of the miniature pile 3 is arranged in the soft soil foundation 1, the pile end expanded bottom 4 is arranged in the bearing layer 2, and the overground pile section is positioned above the surface of the soft soil foundation 1; the pile body of the CFG pile 5 is arranged in the soft soil foundation 1, and the overground pile section is positioned above the surface of the soft soil foundation 1; the tops of the micro pile 3 and the CFG pile 5 are positioned on the same horizontal plane; pile bodies of the mini piles 3 and the CFG piles 5 are formed by pouring a mixture of a reinforcement cage and SAP (Super Absorbent Polymer, super absorbent resin);

a regenerated aggregate broken stone cushion layer 6 is paved at a non-pile foundation position on the surface of the soft soil foundation 1, and the upper surface of the regenerated aggregate broken stone cushion layer 6 is flush with pile tops of the micro pile 3 and the CFG pile 5; a layer of steel-plastic geogrid 7 is paved above the mini pile 3, the CFG pile 5 and the recycled aggregate broken stone cushion layer 6; the steel reinforcement framework of the connecting beam 8 is built above the steel-plastic geogrid 7, and the steel reinforcement frameworks at the tops of the micro piles 3 and the CFG piles 5 penetrate through meshes of the steel-plastic geogrid 7 and are connected with the steel reinforcement framework of the connecting beam 8; the poured connecting beams 8 form a beam grid system; high-strength foam light soil is poured in gaps among connecting beams 8 in the beam grid system, and the upper surface of the high-strength foam light soil is flush with the top surface of the beam grid system; a layer of steel-plastic geogrid 7 is paved above the beam grid system and the high-strength foam lightweight soil in the beam grid system.

Preferably, the SAP mixture is fine aggregate concrete with the mixing amount of SAP being 0.3-0.5 wt% of the mixing amount of cement; the SAP is prepared by uniformly mixing 20 to 25 weight percent of bentonite, 0.2 to 0.4 weight percent of acrylic acid, 0.04 to 0.07 weight percent of sodium hydroxide solution with the concentration of 30 to 40 weight percent, 8 to 9 weight percent of hydroxyethyl methacrylate, 0.3 to 0.35 weight percent of cross-linking agent N, N-methylene bisacrylamide and 0.2 to 0.35 weight percent of initiator potassium persulfate.

Preferably, the distance between adjacent micro piles 3 and CFG piles 5 is 1.8 to 2.8m, the distance between adjacent two micro piles 3 is 2.5 to 4.0m, and the distance between adjacent two CFG piles 5 is 2.5 to 4.0m.

Preferably, the micro pile 3 is a cast-in-situ reinforced concrete pile; the pile end of the bottom part is enlarged to form a pile end expanded bottom 4 and extends to the bearing layer 2; the steel reinforcement framework positioned at the center position penetrates through the whole pile body.

Preferably, the CFG pile 5 is a slurry retaining wall drilling hole, the pile diameter is 600-800 mm, and the steel reinforcement framework at the center position penetrates through the pile body of the whole CFG pile 5 or is arranged in the range of 1/2-1/3 pile length at the upper part of the pile top.

Preferably, the connecting beam 8 is a lightweight aggregate concrete beam, and the connecting beam 8 can be cast in situ according to construction period requirements.

Preferably, the pile length of the CFG pile 5 can be adjusted according to the actual engineering situation, and the CFG pile 5 is shorter than the micro pile 3 and does not extend into the bearing layer 2; or arranging a prefabricated micro pile 13 at the bottom pile end of the CFG pile 5, and inserting the pile top of the prefabricated micro pile 13 into the bottom pile end of the CFG pile 5; the pile diameter of the prefabricated micro pile 13 is the same as that of the micro pile 3, and the bottom pile end enters the bearing layer 2 and is positioned on the same horizontal plane with the bottom pile end of the micro pile 3; the pile body of the precast micro pile 13 is formed by pouring SAP mixture.

Preferably, the steel reinforcement framework of the micro pile 3 is a round steel reinforcement framework formed by binding and connecting the micro pile stirrups 3-1 and the micro pile longitudinal ribs 3-2;

preferably, the steel reinforcement framework of the CFG pile 5 is a square steel reinforcement framework formed by binding and connecting CFG pile stirrups 5-1 and CFG pile longitudinal ribs 5-2;

preferably, the steel reinforcement framework of the connecting beam 8 is a square steel reinforcement framework formed by binding and connecting beam hoops 8-1 and connecting beam longitudinal ribs 8-2.

The invention also provides a construction method (short for method) of the SAP pile rib composite structure for controlling the uneven settlement of the embankment, which is characterized by comprising the following steps:

step 1, according to engineering geological survey data, respectively determining pile length, pile diameter, pile spacing and pile position information of each of the micro pile 3 and the CFG pile 5 so as to meet the bearing capacity requirements of an overlying structure on the soft soil foundation 1 under the action of dead load and traffic dynamic load, and respectively determining components of SAP (super-absorbent polymer) mixtures of the micro pile 3 and the CFG pile 5;

step 3, positioning, drilling and clearing holes at the position where the CFG pile 5 is arranged, and building a pile body template above the surface of the soft soil foundation 1 for pouring the overground pile section; then preparing SAP mixture according to design requirements, pumping the SAP mixture into pile holes of the CFG piles 5 through grouting pipes, and pulling out the grouting pipes after the actual feeding amount is not less than the design feeding amount, wherein the pumping amount of the SAP mixture is matched with the pipe pulling speed; then inserting the steel reinforcement framework of the CFG pile 5 into the center position of the top of the CFG pile 5 to the designed depth, pouring SAP mixture into the pile body template to be filled, and reserving the steel reinforcement framework of part of the CFG pile 5 for connecting with the steel reinforcement framework of the connecting beam 8; or positioning, drilling and clearing holes at the position where the CFG pile 5 is arranged, and building a pile body template above the surface of the soft soil foundation 1 for pouring the overground pile section; then inserting a steel reinforcement framework penetrating through the pile body of the whole CFG pile 5 at the central position of the CFG pile 5, preparing an SAP mixture according to design requirements, pumping the SAP mixture into a pile hole of the CFG pile 5 through a grouting guide pipe until the pile body template is filled, and reserving the steel reinforcement framework of part of the CFG pile 5 for being connected with the steel reinforcement framework of the connecting beam 8;

positioning, drilling, reaming pile ends and clearing holes at the position where the micro pile 3 is arranged, and building a pile body template above the surface of the soft soil foundation 1 for pouring the overground pile section; then inserting a reinforcement cage of the micro pile 3 at the center of the micro pile 3, preparing an SAP mixture according to design requirements, pumping the SAP mixture into a pile hole of the micro pile 3 through a grouting conduit until the pile body template is filled, and reserving a part of reinforcement cage of the micro pile 3 for connecting with the reinforcement cage of the connecting beam 8;

after the outer surfaces of the overground pile sections of the CFG piles 5 and the micro piles 3 meet the condition of being not damaged by the form removal, removing the pile body template, and curing to form the CFG piles 5 and the micro piles 3;

preferably, in step 3, after the pile body strength of the CFG pile 5 meets the construction requirement of the mini pile 3 (generally after the construction of the CFG pile for 5-7 d), the construction of the mini pile 3 is performed or the construction of the CFG pile 5 and the mini pile 3 are performed simultaneously.

Preferably, in step 3, the pile body template height (i.e., the height of the above-ground pile section) of the CFG piles 5 and the micro piles 3 is 300 to 500mm.

Preferably, in step 3, the bottom end of the reinforcement cage of the CFG pile 5 extends into not less than 2m below the soft soil foundation 1.

Step 4, paving recycled aggregate at the non-pile foundation position of the soft soil foundation 1 until the recycled aggregate is flush with pile tops of the micro piles 3 and the CFG piles 5 to form a recycled aggregate broken stone cushion layer 6; the particle size of the recycled aggregate meets the particle size requirement of the crushed stone cushion layer;

preferably, in the step 4, the thickness of the recycled aggregate crushed stone cushion layer 6 is 300-500 mm which is the same as the height of the overground pile sections of the CFG piles 5 and the micro piles 3.

Step 5, paving a layer of steel-plastic geogrid 7 above the micro pile 3, the CFG pile 5 and the recycled aggregate broken stone cushion layer 6;

step 6, building a reinforcement cage of the connecting beam 8 above the steel-plastic geogrid 7, and binding and connecting the reinforcement cage at the tops of the micro piles 3 and the CFG piles 5 with the reinforcement cage of the connecting beam 8 by penetrating through meshes of the steel-plastic geogrid 7; then building a connecting beam template, pouring lightweight aggregate concrete and curing to form a beam grid system;

preferably, in step 6, the lightweight aggregate concrete has a strength grade of not less than grade C25.

In this embodiment, the width of the connecting beam 8 is 350 to 450mm and the height is 250 to 300mm. The bottom of the connecting beam 8 adopts a permanent template, and two side surfaces of the connecting beam 8 adopt detachable templates.

Step 7, dismantling the connecting beam templates, pouring high-strength foam light soil in gaps among connecting beams 8 in the beam grid system, embedding the high-strength foam light soil in the beam grid system, enabling the upper surface of the high-strength foam light soil to be level with the top surface of the beam grid system, and curing according to requirements;

preferably, in step 7, the unconfined compressive strength of the high strength foamed lightweight soil is not less than 4.0MPa, preferably 4.0 to 6.0MPa.

And 8, paving a layer of steel-plastic geogrid 7 above the beam grid system and the high-strength foam light soil in the beam grid system to obtain the SAP pile rib composite structure.

Preferably, in

steps

5 and 8, the tensile strength of the steel-plastic geogrid 7 is not lower than 100kN/m.

The invention also discloses a road engineering construction method based on the SAP pile rib composite structure, which comprises the following steps:

(1) Casting ordinary foam light soil with unconfined compressive strength not lower than 1.0MPa above the SAP pile rib composite structure, and curing according to requirements to form an ordinary foam light soil layer 9;

preferably, in the step (1), the common foam lightweight soil layer 9 should meet the relevant regulations of the technical regulations of the design and construction of cast-in-situ foam lightweight soil embankment (TJG F1001-2011), and ribs such as geogrids, geocells or reinforcing steel meshes can be arranged inside the common foam lightweight soil layer according to the load requirement to enhance the strength and rigidity of the common foam lightweight soil layer.

(2) Paving basalt fiber concrete above the common foam lightweight soil layer 9, and curing according to requirements to form a basalt fiber concrete layer 10 with the thickness of 70-100 mm; the laying of the basalt fiber concrete layer can exert the advantages of high strength, corrosion resistance and high temperature resistance of basalt fibers, can improve the tensile strength, the shock resistance and the alkali resistance of the concrete protective layer, and is beneficial to the transmission and the durability of the load of the pavement structural layer.

Preferably, in the step (2), the volume doping amount of the basalt fiber in the basalt fiber concrete layer 10 is 0.1-0.2%;

(3) A pavement structure layer 11 is paved above the basalt fiber concrete layer 10, and after maintenance is carried out according to requirements, a road engineering with an SAP pile-rib composite structure is formed, and uneven settlement in a long-term service process can be well controlled.

Preferably, in step (3), the pavement structure layer 11 comprises a macadam base layer, a base layer and an asphalt surface layer from bottom to top.

(4) The drainage ditches 12 are positioned at two sides of the embankment and 2-3m away from the slope toe, are paved or built by precast slabs or grout rubbles, are firstly measured and lofted according to design requirements before construction, are then excavated by foundation trenches and are paved by bottom mortar cushions, and finally are installed by precast slabs or built by grout rubbles.

The invention is applicable to the prior art where it is not described.

Claims

1. The SAP pile rib composite structure for controlling the uneven settlement of the embankment is characterized by comprising a miniature pile (3), a CFG pile (5), a recycled aggregate crushed stone cushion layer (6), a steel-plastic geogrid (7), high-strength foam light soil and a beam grid system;

the micro piles (3) and the CFG piles (5) are distributed according to triangles; the pile body of the miniature pile (3) is arranged in the soft soil foundation (1), the pile end bottom expansion (4) is arranged in the bearing layer (2), and the overground pile section is positioned above the surface of the soft soil foundation (1); the pile body of the CFG pile (5) is arranged in the soft soil foundation (1), and the overground pile section is positioned above the surface of the soft soil foundation (1); pile tops of the micro pile (3) and the CFG pile (5) are positioned on the same horizontal plane; pile bodies of the micro pile (3) and the CFG pile (5) are formed by pouring a reinforcement cage and an SAP mixture;

a regenerated aggregate broken stone cushion layer (6) is paved at a non-pile foundation position on the surface of the soft soil foundation (1), and the upper surface of the regenerated aggregate broken stone cushion layer (6) is flush with pile tops of the micro pile (3) and the CFG pile (5); a steel-plastic geogrid (7) is paved above the mini pile (3), the CFG pile (5) and the recycled aggregate broken stone cushion layer (6); the steel skeleton of the connecting beam (8) is built above the steel-plastic geogrid (7), and the steel skeletons at the tops of the micro piles (3) and the CFG piles (5) penetrate through meshes of the steel-plastic geogrid (7) and are connected with the steel skeleton of the connecting beam (8); the poured connecting beams (8) form a beam grid system; high-strength foam light soil is poured in gaps among connecting beams (8) in the beam grid system, and the upper surface of the high-strength foam light soil is flush with the top surface of the beam grid system; a steel-plastic geogrid (7) is paved above the beam grid system and the high-strength foam lightweight soil in the beam grid system.

2. The SAP pile rib composite structure for controlling uneven settlement of a embankment according to claim 1, wherein the SAP mixture is fine aggregate concrete with the mixing amount of SAP of 0.3-0.5wt% of the cement mixing amount; the SAP is prepared by uniformly mixing 20-25wt% of bentonite, 0.2-0.4wt% of acrylic acid, 0.04-0.07 wt% of sodium hydroxide solution with the concentration of 30-40%, 8-9wt% of hydroxyethyl methacrylate, 0.3-0.35wt% of cross-linking agent N, N-methylene bisacrylamide and 0.2-0.35wt% of initiator potassium persulfate.

3. The SAP pile rib composite structure for controlling uneven settlement of an embankment according to claim 1, wherein a distance between adjacent micro piles (3) and CFG piles (5) is 1.8-2.8 m, a distance between adjacent two micro piles (3) is 2.5-4.0 m, and a distance between adjacent two CFG piles (5) is 2.5-4.0 m.

4. The SAP pile rib composite structure for controlling uneven settlement of embankment according to claim 1, wherein the bottom pile end of the mini pile (3) is partially enlarged to form a pile end expanded bottom (4) and extends to the bearing layer (2), and the reinforcement cage at the central position penetrates through the whole pile body.

5. The SAP pile rib composite structure for controlling uneven settlement of a embankment according to claim 1, wherein the reinforcement cage at the center position penetrates through the pile body of the whole CFG pile (5) or is arranged in a 1/2-1/3 pile length range of the upper part of the pile top.

6. SAP pile rib composite structure for controlling non-uniform settlement of embankments according to claim 1, characterized in that the CFG piles (5) are shorter than the mini-piles (3) and do not extend into the bearing layer (2); or a prefabricated micro pile (13) is arranged at the bottom pile end of the CFG pile (5), and the pile top of the prefabricated micro pile (13) is inserted into the bottom pile end of the CFG pile (5); the pile diameter of the prefabricated micro pile (13) is the same as that of the micro pile (3), and the bottom pile end enters the bearing layer (2) and is positioned on the same horizontal plane with the bottom pile end of the micro pile (3); the pile body of the prefabricated mini pile (13) is formed by pouring SAP mixture.

7. The SAP pile rib composite structure for controlling uneven settlement of a embankment according to claim 1, wherein the steel reinforcement cage of the micro pile (3) is a round steel reinforcement cage formed by binding and connecting micro pile stirrups and micro pile longitudinal ribs;

the steel reinforcement framework of the CFG pile (5) is a square steel reinforcement framework formed by binding and connecting CFG pile stirrups and CFG pile longitudinal ribs;

the steel reinforcement framework of the connecting beam (8) is a square steel reinforcement framework formed by binding and connecting the connecting beam stirrups and connecting beam longitudinal ribs.

8. A method of constructing an SAP pile rib composite structure for controlling differential settlement of a embankment as claimed in any one of claims 1 to 7, the method comprising the steps of:

step 1, according to engineering geological survey data, respectively determining pile length, pile diameter, pile spacing and pile position information of each of the micro pile (3) and the CFG pile (5) so as to meet the bearing capacity requirements of an overlying structure on a soft soil foundation (1) under the action of dead load and traffic dynamic load, and simultaneously respectively determining components of SAP (super absorbent polymer) mixtures of the micro pile (3) and the CFG pile (5);

step 3, positioning, drilling and clearing holes at the position where the CFG pile (5) is arranged, and building a pile body template above the surface of the soft soil foundation (1) for pouring the overground pile section; preparing an SAP mixture according to design requirements, and pumping the SAP mixture into pile holes of the CFG piles (5); after the actual feeding amount is not less than the designed feeding amount, inserting a steel reinforcement framework of the CFG pile (5) into the designed depth at the top center position of the CFG pile (5), pouring SAP mixture into the pile body template to be filled, and reserving the steel reinforcement framework of part of the CFG pile (5) for being connected with the steel reinforcement framework of the connecting beam (8); or positioning, drilling and cleaning holes at the position where the CFG pile (5) is arranged, and building a pile body template above the surface of the soft soil foundation (1) for pouring the overground pile section; then inserting a steel reinforcement framework penetrating through the pile body of the whole CFG pile (5) at the central position of the CFG pile (5), preparing an SAP mixture according to design requirements, pumping the SAP mixture into pile holes of the CFG pile (5) until pile body templates are filled, and reserving the steel reinforcement framework of part of the CFG pile (5) for being connected with the steel reinforcement framework of the connecting beam (8);

positioning, drilling, reaming the pile ends and clearing holes at the position where the miniature pile (3) is arranged, and building a pile body template above the surface of the soft soil foundation (1) for pouring the overground pile section; then inserting a reinforcement cage of the micro pile (3) at the center of the micro pile (3), preparing an SAP mixture according to design requirements, pumping the SAP mixture into pile holes of the micro pile (3) until the pile body template is filled, and reserving a part of reinforcement cage of the micro pile (3) for connecting with the reinforcement cage of the connecting beam (8);

after the outer surfaces of the overground pile sections of the CFG piles (5) and the micro piles (3) meet the conditions, removing pile body templates, and curing to form the CFG piles (5) and the micro piles (3);

step 4, paving recycled aggregate at the non-pile foundation position of the soft soil foundation (1) until the recycled aggregate is flush with pile tops of the micro piles (3) and the CFG piles (5) to form a recycled aggregate broken stone cushion layer (6); the particle size of the recycled aggregate meets the particle size requirement of the crushed stone cushion layer;

step 5, paving a steel-plastic geogrid (7) above the micro pile (3), the CFG pile (5) and the recycled aggregate broken stone cushion layer (6);

step 6, building a reinforcement cage of the connecting beam (8) above the steel-plastic geogrid (7), wherein the reinforcement cage at the tops of the micro pile (3) and the CFG pile (5) penetrate through meshes of the steel-plastic geogrid (7) and are bound and connected with the reinforcement cage of the connecting beam (8); then building a connecting beam template, pouring lightweight aggregate concrete and curing to form a beam grid system;

step 7, dismantling the connecting beam templates, pouring high-strength foam light soil in gaps among connecting beams (8) in the beam grid system until the upper surface of the high-strength foam light soil is flush with the top surface of the beam grid system, and curing according to requirements;

and 8, paving a steel-plastic geogrid (7) above the beam grid system and the high-strength foam lightweight soil in the beam grid system to obtain the SAP pile rib composite structure.

9. The construction method of the SAP pile rib composite structure for controlling the differential settlement of the embankment according to claim 8, wherein in the step 3, the construction of the micro pile (3) or the construction of the CFG pile (5) and the micro pile (3) are simultaneously carried out after the pile body strength of the CFG pile (5) meets the construction requirement of the micro pile (3);

the pile body template heights of the CFG piles (5) and the micro piles (3) are 300-500 mm;

the bottom end of the steel reinforcement framework of the CFG pile (5) stretches into the position below the soft soil foundation (1) by not less than 2m.

10. The construction method of SAP pile rib composite structure for controlling uneven settlement of embankment according to claim 8, wherein in step 6, the strength grade of the lightweight aggregate concrete is not less than the C25 grade;

in the step 7, the unconfined compressive strength of the high-strength foam lightweight soil is not lower than 4.0MPa;

in the step 5 and the step 8, the tensile strength of the steel-plastic geogrid (7) is not lower than 100kN/m.