CN110777570A

CN110777570A - Expansive soil large-deformation anti-upwarp foundation structure and construction method of foundation structure

Info

Publication number: CN110777570A
Application number: CN201910954604.2A
Authority: CN
Inventors: 陈远洪; 曾长贤; 刘国; 廖进星; 郭建湖; 孟祥龙; 袁丛军; 骆斌; 黄红华; 顾成权; 李巍; 范瑞祥
Original assignee: China Railway Siyuan Survey and Design Group Co Ltd
Current assignee: China Railway Siyuan Survey and Design Group Co Ltd
Priority date: 2019-10-09
Filing date: 2019-10-09
Publication date: 2020-02-11

Abstract

The invention discloses a foundation structure for preventing expansive soil from being deformed greatly and arching and a construction method of the foundation structure, wherein the foundation structure comprises a reinforcing pile and a void structure, the reinforcing pile partially extends into foundation soil, and the void structure is used for bearing a roadbed structure; the void structure is connected at the top of the reinforcing pile, and an accommodating space with a preset depth is formed between the void structure and the top surface of the foundation soil. Through setting up reinforcing pile, void structure to set up accommodation space between the top surface of void structure and foundation soil, not only effectively guaranteed to bear and subside the control effect, still effectively eliminated the risk of encircleing to the road bed.

Description

Expansive soil large-deformation anti-upwarp foundation structure and construction method of foundation structure

Technical Field

The invention relates to the technical field of foundation treatment, in particular to a foundation structure for preventing expansive soil from being deformed upwards and a construction method of the foundation structure.

Background

The expansive soil has the characteristics of strong shrinkage after water loss and strong expansion after water absorption, and if the foundation soil expands due to water absorption, a roadbed structure on a foundation structure generates an upwarp disease, so that the normal operation of a high-speed railway is influenced.

For low embankments and excavation cuts, foundation structures of high speed railways with expansive soils are typically treated by: the foundation bed is filled with qualified fillers, the foundation structure is processed by combining CFG (Cement Fly-ash Gravel) piles and pile caps with a broken stone cushion layer clamping and paving geogrid structure, the method has good effect of preventing the subgrade structure from settling, the cost is low, but expansive soil among the CFG piles is easy to expand and deform when meeting water, so that the cushion layer, the filling soil and the subgrade structure are subjected to expansion to generate upwarp diseases, and the upwarp prevention requirement of the subgrade structure under the condition of strong expansion cannot be met. Therefore, although the settlement prevention effect of the roadbed structure is good, the anti-arching capacity is insufficient, and the measures are weak.

Disclosure of Invention

In order to solve the technical problems, the embodiment of the invention provides a foundation structure with expansive soil large deformation and upward arching prevention and a construction method of the foundation structure.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

the embodiment of the invention discloses a foundation structure for preventing expansive soil from being deformed upwards, which comprises a reinforcing pile and a void structure, wherein the reinforcing pile partially extends into foundation soil with the expansive soil, and the void structure is used for bearing a roadbed structure;

the void structure is connected at the top of the reinforcing pile, and an accommodating space with a preset depth is formed between the void structure and the top surface of the foundation soil.

In the above scheme, the foundation structure further comprises a support structure, and the support structure is connected to the top of the reinforcing pile and connected to the void structure.

In the above scheme, the support structure includes a first support member and a second support member, one end of the first support member is inserted into the reinforcing pile, and the other end of the first support member is inserted into the void structure;

the second supporting piece is arranged on the peripheral side of the first supporting piece and extends out of the reinforcing pile;

the void-free structure is supported on the second support.

In the above scheme, one end of the first support member connected to the reinforcing pile is in a tapered shape with an inner diameter gradually decreasing from top to bottom, and one end of the first support member connected to the void structure is in a frustum shape with an inner diameter gradually decreasing from top to bottom.

In the above scheme, the support structure is made of steel.

In the above scheme, the first support piece is a steel reinforcement cage, and the second support piece is a steel bar.

In the above scheme, the second supporting member is welded to the first supporting member.

In the above scheme, the reinforcing piles are CFG piles; and/or

The foundation structure further comprises a water drainage hole and a side ditch, the side ditch is located on one side of the void structure, and the water drainage hole is communicated with the accommodating space and the side ditch so as to guide water in the accommodating space into the side ditch.

In the above scheme, the void structure comprises a bottom die and a raft, the bottom die is arranged on the support structure, and the raft is poured on the bottom die.

In the above scheme, the raft is of a reinforced concrete structure.

The embodiment of the invention also provides a construction method of the roadbed structure, which comprises the following steps:

removing the foundation soil until the top surface of the foundation soil is positioned below the pile top of the reinforcing pile;

and a void structure is arranged at the top of the reinforcing pile, and an accommodating space with a preset depth is formed between the void structure and the top surface of the foundation soil.

In the above scheme, the construction method further comprises: and arranging a running water slope on the top surface of the foundation soil.

In the above scheme, the construction method further comprises: and firstly, arranging a supporting structure at the top of the reinforcing pile, and then arranging the void structure on the supporting structure.

In the above scheme, the construction method further comprises:

inserting one end of a first support member of the support structure into the reinforcing pile before the reinforcing pile is solidified;

and inserting the pile top of the reinforcing pile and the other end of the first support piece into the void structure, and reserving a second support piece extending out of the reinforcing pile on the peripheral side of the first support piece.

In the above scheme, the construction method further comprises:

arranging a bottom die of the void structure on the second support;

binding reinforcing steel bars on the bottom die, and pouring concrete to form a raft plate of the void structure; the pile top of the reinforcing pile and the other end of the first supporting piece are inserted into the raft plate.

The invention provides a foundation structure for preventing expansive soil from being deformed and arching and a construction method of the foundation structure. An accommodating space provided for foundation soil expansion is arranged between the void structure and the top surface of the foundation soil, and the void structure has the function of resisting the foundation soil expansion and arching. According to the foundation structure provided by the embodiment of the invention, the reinforcing piles and the void structures are arranged, and the accommodating space is arranged between the void structures and the top surfaces of the foundation soil, so that the bearing and settlement control effects are effectively ensured, and the arching risk to the roadbed structure is effectively eliminated.

Drawings

Fig. 1 is a schematic view of a foundation structure and a roadbed structure according to an embodiment of the present invention;

fig. 2 is a partially enlarged view of a portion a in fig. 1.

Reference numerals:

a reinforcing pile 10; a void-free structure 20; a bottom die 21; a raft 22; a support structure 30; the first support 31; a second support member 32; a top surface 40 of the foundation soil; an accommodating space 50; a drain hole 60; a side groove 70; a side mold 80; a roadbed structure 90; a slope 91 of the subgrade; a flow slope 92 on the subgrade; a ground line 93.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the drawings of the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention, belong to the scope of protection of the invention.

In the description of the present invention, it is to be understood that the terms "upper", "lower", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in fig. 1.

The embodiment of the invention provides a foundation structure for preventing expansive soil from being deformed upwards, which comprises a reinforcing pile 10 and a void structure 20, wherein the reinforcing pile 10 partially extends into foundation soil with the expansive soil, and the void structure 20 is used for bearing a roadbed structure 90; the void structure 20 is connected to the top of the reinforcing piles 10, and an accommodation space 50 of a predetermined depth is formed between the void structure 20 and the top surface 40 of the foundation soil.

As shown in fig. 1, the foundation soil is reinforced by the reinforcing piles 10, the roadbed structure 90 is arranged on the void structure 20, and the load from the roadbed structure 90 is transmitted to the foundation soil by the void structure 20 through the reinforcing piles 10, so that the bearing effect of the foundation structure is effectively ensured, and the settlement control effect on the foundation soil is improved. The gap is arranged between the void structure 20 and the top surface 40 of the foundation soil to form an accommodating space 50, the accommodating space 50 can accommodate the upwarp deformation of the foundation soil, the effect of resisting the upwarp of the foundation soil is improved, and the upwarp risk to the roadbed structure 90 is effectively eliminated.

The preset depth of the receiving space 50 may be adjusted according to the deformation of the foundation soil and the requirement of the roadbed structure 90. For example: the preset depth is 0.3-0.5 m.

The "large deformation" in the embodiment of the present invention refers to a case where the amount of upward arching deformation of the roadbed structure 90 caused by the expansion of the expansive soil is greater than 0.1 m. The foundation structure of the embodiment of the invention can meet the corresponding requirement of the roadbed structure because the high-speed railway has strict requirement on the deformation of the roadbed structure.

In some embodiments of the present invention, the foundation structure further includes a drainage hole 60 and a lateral ditch 70, the lateral ditch 70 is located at one side of the evacuation structure 20, and the drainage hole 60 communicates the accommodating space 50 and the lateral ditch 70 to guide water in the accommodating space 50 into the lateral ditch 70. For better drainage, the top surface 40 of the foundation soil is also provided with a running water slope, and the gradient coefficient of the running water slope is preferably not less than 0.2%. Accumulated water in the accommodating space 50 can be discharged into the side ditch 70 through the water discharge holes 60 in time, so that the influence of the foundation soil on the change of the water environment is reduced, and the upper arch of the expansive soil is favorably reduced.

Further, the foundation structure further includes a support structure 30, and the support structure 30 is connected to the top of the reinforcing piles 10 and is connected to the void structure 20.

The support structure 30 serves to connect the reinforcing piles 10 and the void structure 20, improving the mechanical properties of the foundation structure. The reinforcing piles 10, the void structures 20 and the supporting structures 30 form an integral bending-resistant and compression-resistant structure, so that the dead weight of the void structures 20, the roadbed filling and the rail train load effects are effectively resisted, and the bearing and settlement control effects of the foundation structure under the load and the foundation expansive soil water loss shrinkage effects are further improved.

In some embodiments of the present invention, the supporting structure 30 includes a first supporting member 31 and a second supporting member 32, one end of the first supporting member 31 is inserted into the reinforcing pile 10, and the other end of the first supporting member 31 is inserted into the void structure 20; the second support member 32 is disposed on the periphery of the first support member 31 and extends outside the reinforcing pile 10; the disengaging structure 20 is supported on a second support 32.

The insertion of the first support 31 into the reinforcing piles 10 at one end and into the hollow structure 20 at the other end ensures the integrity of the reinforcing piles 10, the support structure 30 and the reinforcing piles 10. The second support member 32 is used as a support point, and the hollow structure 20 is arranged on the second support member 32, so that the construction of the hollow structure 20 is facilitated, and the connection strength between the hollow structure 20 and the support structure 30 is further improved.

To better ensure the strength and integrity of the foundation structure, the support structure 30 is preferably steel.

It is understood that other alloys may be used for the support structure 30, or materials that may be substituted for steel reinforcement in future technologies. For example: the support structure 30 may be selected from fiberglass, carbon fiber, and the like.

Without limitation, for example: the first supporting member 31 is a reinforcement cage made of steel bars, and the second supporting member 32 is made of steel bars. Generally cylindrical. Compared with the length of the reinforcing pile 10, the length of the reinforcement cage is shorter, about 2-5 m.

At least two second supporting members 32 may be uniformly disposed on the peripheral side of each first supporting member 31, the first supporting members 31 are disposed in the vertical direction, the second supporting members 32 are disposed in the horizontal direction, and both are disposed vertically.

Preferably, the second support 32 is welded to the first support 31. For example: adopt the welded mode to set up 3 ~ 6 rust-resistant billet of zinc-plating on the steel reinforcement cage, billet thickness 5mm, wide 20mm, long 100mm, the billet is evenly arranged around reinforcing pile 10.

Without limitation, the end of the first support 31 connected to the reinforcing pile 10 is tapered with an inner diameter gradually decreasing from top to bottom, and the end of the first support 31 connected to the void structure 20 is frustum-shaped with an inner diameter gradually decreasing from top to bottom. As shown in fig. 1, the tapered bottom portion is more easily inserted into the reinforcing pile 10 for construction, and the head portion has a large upper portion and a small lower portion, and is flared upward to be better anchored into the hollow structure 20.

In some embodiments of the invention, the reinforcing piles are reinforced concrete bored piles and the void structures are plate girder structures.

In other preferred embodiments of the present invention, the reinforcing piles 10 may be CFG piles. Compared with a reinforced concrete bored pile, the CFG pile has smaller space, reduces the using amount of reinforcing steel bars, is cheaper, and reduces the cost. Without limitation, the CFG piles, the supporting structure 30 and the void structure 20 bear bending moment together, the length of the CFG piles is generally 10-25 m, and the thickness of the raft 22 is 0.4-0.6 m.

Further, the void structure 20 includes a bottom mold 21 and rafts 22, the bottom mold 21 is disposed on the reinforcing piles 10, and the rafts 22 are cast on the bottom mold 21. Without limitation, the bottom form 21 may be a relatively inexpensive wooden form, and as shown in fig. 2, the raft 22 is disposed on the wooden form after the wooden form is disposed on the second support structure 30.

Rafts 22 are preferably of reinforced concrete construction. Specifically, during construction, the reinforcing steel bars of the raft 22 are bound on the bottom mold 21, and meanwhile, the reinforcing steel bars of the raft 22 are also connected with the reinforcing steel bars of the first support members 31 on the reinforcing piles 10, and then concrete is poured to form the raft 22. The integrity of the reinforcing piles 10, the hollow structures 20 and the support structures 30 is further improved, and the bending resistance and the compression resistance of the integral structure formed by the reinforcing piles 10, the hollow structures 20 and the support structures 30 are ensured.

The embodiment of the invention also provides a construction method of the foundation structure, which is used for constructing and forming any one of the foundation structures. The construction method comprises the following steps:

removing the foundation soil until the top surface 40 of the foundation soil is positioned below the pile top of the reinforcing pile 10;

a void structure 20 is provided at the top of the reinforcing piles 10, and a receiving space 50 of a predetermined depth is formed between the void structure 20 and the top surface 40 of the foundation soil.

Taking the construction of the CFG pile as an example, the process of removing the foundation soil to form the reinforcing pile 10 includes: and (4) carrying out field measurement and setting out, determining the positioning and elevation of each point of the CFG pile and the void structure 20 and the like, and preliminarily excavating foundation soil to a position which is about 0.15m below the designed pile top elevation. And (3) adopting a long spiral drilling machine to form holes, wherein the hole diameter is 0.4-0.6 m, the pile spacing is 1.5-2.0 m, the pile length is generally 10-25 m, the square or regular triangle is arranged, and pouring CFG pile hole concrete.

When the foundation structure comprises the above-mentioned support structure 30, the support structure 30 is first provided on top of the reinforcing piles 10, and then the void structure 20 is provided on the support structure 30.

Further, the construction method further comprises the following steps: before the reinforcing pile 10 is solidified, inserting one end of the first support 31 into the reinforcing pile 10; the pile top of the reinforcing pile 10 and the other end of the first support 31 are inserted into the hollow structure 20, and a second support 32 extending out of the reinforcing pile 10 is reserved on the peripheral side of the first support 31.

Specifically, a steel bar cage (i.e., a first support member 31) is inserted into the top of the CFG pile in a post-reinforcement-inserting manner before the poured CFG pile hole concrete is initially set, wherein the conical bottom of the steel bar cage is inserted into the CFG pile, a steel bar (i.e., a second support member 32) capable of extending out of the CFG pile is welded and reserved at the pile head position of the steel bar cage, and the steel bar is positioned about 0.15m below the pile top elevation, i.e., flush with the excavated ground. And further, vibrating and compacting the loose concrete at the head part of the CFG pile by adopting a vibrating rod, removing the concrete which exceeds the elevation of the CFG pile top and leveling the pile head, and curing the concrete until the short reinforcement cage is solidified and hardened with the pile body into a whole.

Further, when the void structure 20 of the foundation structure includes the bottom formwork 21 and the rafts 22 in any one of the above embodiments, the construction method further includes: the bottom die 21 is arranged first, and then the raft 22 is arranged.

Specifically, temporary field mound brought out when the CFG pile is drilled is cleaned and transported outwards, foundation soil between the piles is cleaned and excavated again to a preset depth below the top of the CFG pile, and the preset depth is about 0.3-0.5 m.

Preferably, a running water slope is provided on the top surface 40 of the foundation soil. Specifically, the flowing water slope extends from the middle of the top surface 40 of the foundation soil to both sides, and the gradient coefficient of the flowing water slope is preferably not less than 0.2%. Subsequently, the bottom mold 21 of the disengaging structure 20 is set on the second support 32. Specifically, an overhanging steel bar is reserved in the CFG pile to serve as a supporting point, a bottom mold 21 is arranged on the CFG pile, the bottom mold 21 preferably adopts a cheap wood template, the thickness of the wood template is about 0.05m, and the CFG pile does not need to be dismantled subsequently.

After the bottom die 21 is arranged, erecting raft 22 steel bars and pouring raft 22 concrete. Specifically, steel bars are bound on the bottom die 21, concrete is poured, and a raft 22 of the void structure 20 is formed; the top of the reinforcing pile 10 and the other end of the first support 31 are inserted into the raft 22.

The specific operation process comprises the following steps: and (3) binding reinforcing steel bars of the raft 22 on the bottom die 21, arranging detachable side dies 80 on the periphery by adopting supports, and pouring concrete of the raft 22, wherein the thickness of the raft 22 is preferably 0.4-0.6 m. When the concrete is cast in place, the top of the CFG pile is about 0.1m, and the frustum-shaped head steel bars of the first supporting piece 31 are anchored into the raft 22 to form an integral structure.

After the rafts 22 are formed, roadbed filling may be filled, and side ditches 70 and drainage holes 60 are provided, as shown in fig. 1, with a ground line 93 formed above the rafts 22.

Specifically, as shown in fig. 1, a roadbed structure 90 is provided, the roadbed filling is in a trapezoidal shape, and the slope 91 of the slopes on both sides of the trapezoidal roadbed filling is preferably 1: 1.5. The roadbed filling is filled according to the high-speed railway standard, firstly, the roadbed bottom filling is filled according to the standard compaction of the roadbed bottom, roadbed flowing water slopes are arranged on the top surface of the roadbed bottom towards two sides, and the preferable gradient coefficient of the roadbed flowing water slope 92 is 4%. And then, filling the bedding bottom filler according to the bedding surface layer compaction standard, wherein the shape of the roadbed surface is set according to the high-speed railway track type.

The process of constructing the lateral ditches 70 and the drainage holes 60 includes: the method comprises the steps of vertically excavating foundation pits with side ditches 70 on two sides, binding steel bars of the side ditches 70, arranging a detachable inner mold by using the vertical soil molds on the two sides and adopting a support, pouring concrete of the side ditches 70, arranging a water drainage hole 60 at the bottom of a containing space 50 on the inner side of each side ditch 70, wherein the optimal diameter of the water drainage hole 60 is 0.1m, the distance between the water drainage hole 60 and the bottom surface of each side ditch 70 is not less than 0.2m, and every 1-2 m of the water drainage hole 60 is vertical, so that water accumulated at a void part can be timely removed, and the influence.

The features disclosed in the several construction method or foundation structure embodiments provided in the present application may be combined arbitrarily without conflict, resulting in a new construction method embodiment or foundation structure embodiment.

Other structures and operations of the foundation structure according to the embodiments of the present invention will be understood and readily implemented by those skilled in the art, and thus will not be described in detail.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention.

Claims

1. The foundation structure is characterized by comprising reinforcing piles and a void structure, wherein the reinforcing piles partially extend into foundation soil with the expansive soil, and the void structure is used for bearing a roadbed structure;

2. A foundation structure according to claim 1, further comprising a support structure connected to the top of the reinforcing piles and connected to the void structure.

3. A foundation structure according to claim 2, wherein said supporting structure comprises a first support and a second support, one end of said first support being inserted into said reinforcing piles and the other end of said first support being inserted into said hollowed structure;

the void-free structure is supported on the second support.

4. A foundation structure according to claim 3, wherein the end of the first supporting member connected to the reinforcing piles is tapered such that the inner diameter thereof is gradually reduced from top to bottom, and the end of the first supporting member connected to the void structure is frustum-shaped such that the inner diameter thereof is gradually reduced from top to bottom.

5. A foundation structure according to claim 3, wherein said support structure is steel.

6. A foundation structure according to claim 5, wherein said first support member is a reinforcement cage and said second support member is a steel bar.

7. A foundation structure according to claim 6, wherein the second support is welded to the first support.

8. A foundation structure according to claim 1, wherein said reinforcing piles are CFG piles; and/or

9. A foundation structure according to any one of claims 2 to 8, wherein the void structure comprises a bottom form and rafts, the bottom form being provided on the support structure and the rafts being cast on the bottom form.

10. A foundation structure according to claim 9, wherein the rafts are of reinforced concrete construction.

11. A construction method of a roadbed structure is characterized by comprising the following steps:

12. The construction method according to claim 11, further comprising: and arranging a running water slope on the top surface of the foundation soil.

13. The construction method according to claim 11, further comprising: and firstly, arranging a supporting structure at the top of the reinforcing pile, and then arranging the void structure on the supporting structure.

14. The construction method according to claim 13, further comprising:

15. The construction method according to claim 14, further comprising:

arranging a bottom die of the void structure on the second support;