阅读说明：本技术 一种高韧性功能梯度材料抗滑桩及施工方法 (High-toughness functionally-graded material slide-resistant pile and construction method ) 是由 姜清辉 刘乳燕 杨刚 位伟 吕庆 郑俊 于 2021-08-26 设计创作，主要内容包括：本发明公开了一种高韧性功能梯度材料抗滑桩,该抗滑桩包括：PVA-ECC材料保护层、受拉区小粒径粗骨料混凝土、受压区大粒径粗骨料混凝土层；其中PVA-ECC材料保护层、受拉区小粒径粗骨料混凝土层、受压区大粒径粗骨料混凝土层沿滑坡推力方向由内向外依次设置且上述不同分区同时进行浇筑。本发明根据抗滑桩截面不同受力特性进行功能分区,按照梯度结构进行不同的材料设计,本发明制备的功能梯度材料抗滑桩具有高韧性、更优的变形延性、以及抗弯与抗剪承载力。由于受拉区的钢绞线和小粒径粗骨料混凝土能够保持变形协调,同时承受滑坡推力部位设置有优异延性变形的PVA-ECC保护层,减少开裂破坏,提升了整个桩体的韧性和抗弯能力。(The invention discloses a high-toughness functionally-graded material slide-resistant pile, which comprises: the PVA-ECC material protective layer, the small-particle-size coarse aggregate concrete in the tension area and the large-particle-size coarse aggregate concrete layer in the compression area; the PVA-ECC material protective layer, the small-particle-size coarse aggregate concrete layer in the tension area and the large-particle-size coarse aggregate concrete layer in the pressure area are sequentially arranged from inside to outside along the thrust direction of the landslide, and the different subareas are poured simultaneously. The function partition is carried out according to different stress characteristics of the cross section of the slide-resistant pile, different material designs are carried out according to the gradient structure, and the slide-resistant pile made of the functional gradient material has high toughness, better deformation ductility and bending and shearing resistance bearing capacity. Because the steel strands in the tension area and the small-grain-size coarse aggregate concrete can keep deformation coordination, and meanwhile, a PVA-ECC protective layer with excellent ductile deformation is arranged at the part bearing the landslide thrust, cracking damage is reduced, and the toughness and the bending resistance of the whole pile body are improved.)

1. A high-toughness functionally graded material slide-resistant pile, comprising: the PVA-ECC material protective layer, the small-particle-size coarse aggregate concrete in the tension area and the large-particle-size coarse aggregate concrete layer in the compression area;

the PVA-ECC material protective layer, the small-particle-size coarse aggregate concrete layer in the tension area and the large-particle-size coarse aggregate concrete layer in the compression area are sequentially arranged from inside to outside along the thrust direction of the landslide, and the different subareas are poured simultaneously.

2. The high-toughness functionally graded material anti-slide pile according to claim 1, wherein longitudinal steel strand wires in the tension area are arranged in the small-grain-size coarse aggregate concrete layer in the tension area, vertical ribs are arranged in the vertical direction, tie bars are arranged between the vertical ribs, two ends of each tie bar are respectively connected with the vertical ribs, and the longitudinal steel strand wires in the tension area are bound on the tie bars.

3. The slide-resistant pile made of high-toughness functionally graded material according to claim 1, wherein vertical frame ribs are vertically arranged in the large-particle-size coarse aggregate concrete layer of the compression region, tie bars are arranged between the frame ribs, both ends of the tie bars are respectively connected with the frame ribs, and stirrups are arranged outside the tie bars.

4. The high-toughness functionally-graded material slide-resistant pile according to claim 2, wherein the two ends of the longitudinal bars of the steel strands in the tension zone are arranged in a bending way.

5. A high-toughness functionally-graded material slide-resistant pile according to claim 1, wherein the coarse aggregate particle size of the large-particle-size coarse aggregate concrete layer in the compressive region is preferably 30-50 mm, the strength of the small-particle-size coarse aggregate concrete layer in the tensile region is the same as that of the concrete in the compressive region, and the particle size of the coarse aggregate is preferably 10-20 mm.

6. The high-toughness functionally graded material slide pile according to claim 1, wherein the thickness of the protective layer is greater than 50mm, and the actual ductility of the protective layer after a tension test is performed reaches more than 1%.

7. The construction method of the high-toughness functionally graded material slide-resistant pile according to any one of claims 1 to 6, characterized by comprising the following steps:

a. after the pile hole is dug, placing a reinforcement cage and arranging a tension area steel strand longitudinal bar, a reinforcement longitudinal bar, a stirrup, a tie bar and a erection bar, and locking the bottom of the tension area steel strand longitudinal bar;

b. trial-preparing a PVA-ECC material of the protective layer, and performing a tension experiment to ensure that the actual ductility of the PVA-ECC material reaches more than 1%;

c. for the functional partition, partition construction is carried out by using partition air bags, the air bags are filled with air before construction, the air bags are positioned at the interface positions of different partitions, and meanwhile, PVA-ECC materials, small-particle-size coarse aggregate concrete and large-particle-size coarse aggregate concrete are poured into the different partitions;

d. and after the pouring and vibrating are finished, deflating and drawing out the air bag to finish the construction of different functional partitions, performing the construction of the next stage by the same process, after the designed pile body height is reached and the design strength of the concrete is 75 percent, tensioning the steel strand to apply prestress, and sealing the anchor at the upper end by tensioning the prestress.

Technical Field

The invention belongs to the technical field of landslide reinforcement, and particularly relates to a high-toughness functionally-graded material slide-resistant pile and a construction method thereof.

Background

The anti-slide pile is used as an effective landslide retaining component, can effectively improve the anti-slide capability of a slide body, improves the stability of the landslide, achieves the aim of treating the landslide, and is an effective measure widely used at present for treating the landslide. However, the ultimate tensile strain of the concrete is low, the ductility of the steel bar is poor, and brittle failure is easy to occur, so that the anti-slide pile is easy to generate local concentrated cracks in large deformation of a landslide, and further the structural failure of the anti-slide pile is caused, so that the toughness of the anti-slide pile is improved, and the deformation of the anti-slide pile resisting large deflection can well slow down the structural failure of the anti-slide pile.

At present, in the prior art, a post-tensioning pile body prestressed slide-resistant pile and a construction method and a prefabricated box type prestressed slide-resistant pile are mainly used for improving the large-deflection deformation resistance of the slide-resistant pile by adding a steel strand anchor cable in a traditional slide-resistant pile reinforcement cage. However, the flexible prestressed steel strands replace steel bars, and under the action of landslide load, the strain of the steel strands in the anti-slide pile greatly exceeds the ultimate tensile strain of concrete, so that the problem of inconsistent deformation of the concrete and the steel strands in a tensile area occurs. The brittle concrete can cause structural failure after cracking, and the steel strand cannot exert the advantages of high strength and good relaxation performance. Moreover, the cracking and the breaking of the brittle concrete can expose the steel bars and the steel strands to the air to cause the steel bars and the steel strands to be rusted, and the advantage that the steel strands can resist large deformation cannot be fully exerted, so the effect is not ideal.

Disclosure of Invention

Aiming at the problems, the invention provides a high-toughness functionally-graded material slide-resistant pile and a construction method thereof. The functionally graded material is adopted, and the corresponding functional material is arranged in different stress areas, so that the slide-resistant pile with the graded structure can exert the maximum effect to resist the deformation of the slide body.

In order to achieve the purpose, the invention provides the following scheme:

a high toughness functionally graded material friction pile, comprising: the PVA-ECC material protective layer, the small-particle-size coarse aggregate concrete in the tension area and the large-particle-size coarse aggregate concrete layer in the compression area;

the PVA-ECC material protective layer, the small-particle-size coarse aggregate concrete layer in the tension area and the large-particle-size coarse aggregate concrete layer in the compression area are sequentially arranged from inside to outside along the thrust direction of the landslide, and the different subareas are poured simultaneously.

Furthermore, the tension area small-grain-size coarse aggregate concrete layer is internally provided with tension area steel strand longitudinal bars, vertical bars are arranged in the vertical direction, the tension bars are arranged between the vertical bars, two ends of each tension bar are respectively connected with the vertical bars, and the tension area steel strand longitudinal bars are bound on the tension bars.

Furthermore, vertical ribs are arranged in the compression area in the large-particle-size coarse aggregate concrete layer in the vertical direction, tie bars are arranged between the vertical ribs, two ends of each tie bar are respectively connected with the vertical ribs, and stirrups are arranged on the outer sides of the tie bars.

Furthermore, two ends of the longitudinal bar of the steel strand in the tension area are arranged in a bending mode.

Furthermore, the coarse aggregate particle size of the large-particle-size coarse aggregate concrete layer in the pressure area is preferably 30-50 mm, the strength of the small-particle-size coarse aggregate concrete layer in the tension area is the same as that of the concrete in the pressure area, and the particle size of the coarse aggregate is preferably 10-20 mm.

Further, the thickness of the protective layer is more than 50mm, and after a tension test is carried out, the actual ductility of the protective layer reaches more than 1%.

The invention also provides a construction method of the high-toughness functionally-graded material slide-resistant pile, which comprises the following steps:

a. after the pile hole is dug, placing a reinforcement cage and arranging a tension area steel strand longitudinal bar, a reinforcement longitudinal bar, a stirrup, a tie bar and a erection bar, and locking the bottom of the tension area steel strand longitudinal bar;

b. trial-preparing a PVA-ECC material of the protective layer, and performing a tension experiment to ensure that the actual ductility of the PVA-ECC material reaches more than 1%;

c. for the functional partition, partition construction is carried out by using partition air bags, the air bags are filled with air before construction, the air bags are positioned at the interface positions of different partitions, and meanwhile, PVA-ECC materials, small-particle-size coarse aggregate concrete and large-particle-size coarse aggregate concrete are poured into the different partitions;

d. and after the pouring and vibrating are finished, deflating and drawing out the air bag to finish the construction of different functional partitions, performing the construction of the next stage by the same process, after the designed pile body height is reached and the design strength of the concrete is 75 percent, tensioning the steel strand to apply prestress, and sealing the anchor at the upper end by tensioning the prestress.

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

1. because the steel strands in the tension area and the small-grain-size coarse aggregate concrete can keep deformation coordination, and meanwhile, a PVA-ECC protective layer with high toughness and excellent ductile deformation is arranged at a part bearing landslide thrust, the local cracking damage is reduced, the toughness and the bending resistance of the whole pile body are improved, and meanwhile, the steel bars and the steel strands inside the pile body can be better protected from corrosion. In addition, the PVA-ECC has good bonding effect with common concrete, and the problems of layering, connection interface performance reduction and the like do not exist.

2. In a tension area of the slide-resistant pile, the steel strand and the small-grain-size coarse aggregate concrete are cooperatively deformed, so that the performance of the steel strand can be fully exerted, and the brittle failure of the structure under large deformation or sudden conditions is effectively prevented. Coarse aggregate in concrete of a compression area of the slide-resistant pile is basalt broken stone with large particle size, and can also be deformed and coordinated with reinforcing steel bars arranged in the compression area to jointly bear landslide load.

3. The majority of the anti-slide pile construction is in a form of cast-in-place concrete, and different materials are adopted for pouring different subareas, so that the partition air bags are adopted for partitioning different subareas and pouring simultaneously, air bags can be discharged after pouring, the air bags can be recycled, the partition air bags can effectively isolate the mutual permeation among different materials, and the difficulty in the construction of the anti-slide pile made of the high-toughness functionally-graded material is well solved.

Drawings

FIG. 1 is a schematic view of a friction pile on a landslide body according to an embodiment of the invention;

fig. 2 is a transverse sectional view of a slide pile structure according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a functionally graded slide-resistant pile structure and construction according to an embodiment of the invention;

FIG. 4 is a comparison graph of the experimental load displacement curves of the anti-slide pile structure of the embodiment of the invention and the traditional anti-slide pile structure;

in the figure: the concrete comprises 1-PVA-ECC material, 2-a tension area small-particle-size coarse aggregate concrete layer, 3-a compression area large-particle-size coarse aggregate concrete layer, 4-tension area steel strand longitudinal bars, 5-steel bar longitudinal bars, 6-stirrups, 7-tie bars, 8-erection bars and 9-partition airbags.

Detailed Description

The technical solution and the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

Referring to fig. 1-4, the high-toughness functionally graded material slide-resistant pile and the construction technology provided by the invention comprise a PVA-ECC material protective layer 1, a small-grain-size coarse aggregate concrete layer 2 in a tension area, a large-grain-size coarse aggregate concrete layer 3 in a compression area, steel strand longitudinal bars 4 in the tension area, steel bar longitudinal bars 5, stirrups 6, tie bars 7, erection bars 8 and partition airbags 9.

The slide-resistant pile of the embodiment is considered as a flexural member, and reinforcement calculation is performed according to the concrete structure design specification (GB 50010-2010).

The erection reinforcement 8 of this embodiment is a ribbed reinforcement, and the diameter should be greater than 20 mm. The longitudinal stressed steel bars are mainly butt-welded or screwed.

The steel strand of this embodiment is a plain round steel strand. The steel strand is a stranded steel cable consisting of a plurality of high-strength steel wires and is stabilized, and the ultimate tensile strength standard value f_ptk＝1860MPa。

The stirrup 6 of this embodiment is preferably closed. The number of branches should not be more than 4, the diameter should be 10-16 mm, and the distance should be less than 500 mm.

The tie bars 6 of the present embodiment may be hot rolled ribbed steel bars. The length of the lacing wire is determined according to calculation. The arrangement of the lacing wires is in accordance with the construction requirements.

The coarse aggregate particle size of the common concrete in the geometric neutral axis compression zone in the embodiment is preferably 30-50 mm basalt broken stone.

The strength of the concrete in the steel strand laying area is the same as that of the concrete in the compression area, and the coarse aggregate of the concrete is preferably basalt macadam with small grain size of 10-20 mm.

The concrete protective layer of the steel reinforcement cage of this embodiment is 50 mm.

The design process of the concrete mix proportion of the embodiment is as follows:

(1) firstly, selecting cement according to the concrete strength requirement, and determining the prepared strength f according to the actual strength of the cement and the statistical standard deviation of the concrete strength_cu,0. Then according to the formulation strength f_cu,0W/B ratio of cement to water and cement and actual strength f of cement_bThe water-cement ratio is determined according to the relationship, and the calculation formula of the water-cement ratio is as follows:

in the formula, alpha_aAnd alpha_bAs a regression coefficient, α_a＝0.53，α_b＝0.20。

(2) After the water-cement ratio is preliminarily determined, the sand rate and the water consumption are determined according to the requirement of workability, and the calculated mixing ratio is obtained.

(3) On the basis of calculating the mixing proportion, the final construction mixing proportion is obtained by adjusting and calculating the mixing proportion through tests and combining the conditions of a construction site.

The design process of the PVA-ECC mix ratio of the present example is as follows:

adjusting the water-cement ratio, the ratio of fly ash to cement, the sand-cement ratio and the dosage of a water reducing agent, wherein the doping amount of PVA fiber is generally not more than 2%, and when the doping amount exceeds the value, the fiber is difficult to disperse in a matrix, and the fiber is easy to agglomerate, continuously adjusting the ratio, selecting the optimal mixing ratio to replace the material of the pile body tensile area protective layer in the actual engineering, and vibrating in time in the same pouring process.

Before pouring, the position of the partition air bag is fixed, the air bag is filled with air, the 3 materials are poured simultaneously, air is released after pouring is finished, and the air bag is pulled out.

The prestressed construction is mainly characterized in that when the concrete reaches the design strength of 75%, the anchoring end at the lower end is locked by an anchorage device, the upper end is tensioned, and grouting and anchor sealing are carried out within 48 hours after tensioning.

Maintenance in this embodiment: after the concrete construction is finished, timely watering and curing are carried out.

Through an indoor structure test of the novel slide-resistant pile, the ultimate bending moment is improved by about 79 percent compared with that of the traditional reinforced concrete slide-resistant pile; the shear resistance bearing capacity is improved by about 90%, the bending toughness/energy absorption capacity of the novel slide-resistant pile is obviously superior to that of the traditional slide-resistant pile, meanwhile, under the limit state of normal use, the deformation capacity of the novel pile relative to the traditional slide-resistant pile is improved by 211% through experimental data, and under the limit state of bearing capacity, the deformation capacity is improved by 10%. The tests prove that the novel slide-resistant pile has great improvement on the strength and the deformation, and is worthy of further application and popularization.

As shown in fig. 4, which is a comparison graph of the structure test load displacement curve of the slide-resistant pile and the conventional slide-resistant pile, it can be seen that the novel slide-resistant pile is superior to the conventional slide-resistant pile in terms of both bearing capacity and ductility.

The foregoing examples are provided for illustration and description of the invention only and are not intended to limit the invention to the scope of the described examples. Furthermore, it will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that many variations and modifications may be made in accordance with the teachings of the present invention, all of which fall within the scope of the invention as claimed.