A design method of road subsidence support steel pipe pile based on compression bar stability theory

Abstract

The application provides a design method of a road subsidence support steel pipe pile based on a pressure rod stability theory, comprising: a data measurement step, which obtains the following road data by measurement: road width, weight, road surface uniform load of a subsidence road, thickness of a silty clay layer, outer diameter and inner diameter of the steel pipe pile, and determines the width of the subsidence road which needs to be reinforced and supported; a first stress analysis step, which performs stress analysis on the subsidence road, establishes a vertical balance force equation of the subsidence road and a bending moment balance equation of the subsidence road; a second stress analysis step, which performs stress analysis on a single steel pipe pile anchor body, establishes a vertical force balance equation of the steel pipe pile, and obtains a critical vertical pressure value of the steel pipe pile; and according to the vertical balance force equation of the subsidence road, the bending moment balance equation of the subsidence road, the vertical force balance equation of the steel pipe pile, and the critical vertical pressure value of the steel pipe pile, the minimum arrangement number of the steel pipe pile is calculated, the liquefied land can be locally reinforced, and the overall stability of the liquefied land is improved.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical design, specifically relating to a design method for road surface settlement support steel pipe piles based on the compression bar stability theory. Background Technology

[0002] To meet the needs of rapid socio-economic development, various regions are vigorously carrying out highway infrastructure construction. In southwestern my country, with its complex geological conditions and abundant rainfall, the stability of roadbeds faces significant challenges. Roadbeds, exposed to the natural environment for extended periods, are subject to uneven deformation due to soil weight, vehicle loads, and rainwater infiltration, affecting driving quality and safety. In severe cases, road subsidence can occur, damaging the road surface and disrupting traffic. Road subsidence caused by soil liquefaction and softening presents even greater challenges for foundation treatment. Traditional reinforcement methods, such as large-scale replacement, grouting, dynamic compaction, granular material piles, and rigid piles, are often difficult to implement, require substantial investment in machinery, materials, and manpower, and are costly, making them unsuitable for emergency support and repair of sudden, localized road subsidence. Summary of the Invention

[0003] The purpose of this invention is to provide a design method for road settlement support steel pipe piles based on the compression bar stability theory. For road settlement caused by roadbed soil liquefaction, steel pipe piles are arranged at the settlement end. Grouting is carried out through drilling at the top of the road to make the steel pipe piles rigidly and effectively connected to the road, thereby transferring the road load to the deep stable rock bearing layer. Furthermore, the liquefied soil can be locally reinforced by grouting through the reserved holes in the steel pipes, thereby improving the overall stability of the liquefied soil.

[0004] To address the aforementioned problems, this invention provides a design method for steel pipe piles supporting road subsidence based on the stability theory of compression members. The method includes: a data measurement step, where the following road data is measured: road width L, weight G, and uniformly distributed load q on the road surface of the subsided road; further measurement of soil data is performed, including the thickness l of the silty clay layer; the outer diameter d1 and inner diameter d2 of the steel pipe pile are obtained; and the required width m of the subsided road to be reinforced is determined. A first stress analysis step involves performing stress analysis on the subsided road, establishing the vertical equilibrium force equation and the bending moment equilibrium equation for the subsided road. A second stress analysis step involves performing stress analysis on the anchor body of a single steel pipe pile, establishing the vertical force equilibrium equation for the steel pipe pile, and deriving the critical vertical pressure value F of the steel pipe pile. cr Based on the vertical equilibrium force equation, the bending moment equilibrium equation, and the vertical force equilibrium equation of the subsided road, as well as the critical vertical pressure value of the steel pipe pile, the minimum number of steel pipe piles to be arranged is calculated.

[0005] Furthermore, the minimum number of steel pipe piles required for the pavement settlement support steel pipe pile design method based on the above-mentioned compression bar stability theory is:

[0006] Where L2 is the length of the distribution range of silty clay.

[0007] Furthermore, the vertical equilibrium force equation for the subsided road in the above-mentioned design method for road surface settlement support steel pipe piles based on the compression bar stability theory is as follows:

[0008] f s +N=G+qL

[0009] The moment equilibrium equation for a subsided road is as follows:

[0010]

[0011] Among them, f s The resultant force of all the steel pipe pile anchorage friction forces acting vertically upwards on the subsided road, and f s = f × n, where f is the frictional force of a single steel pipe pile anchor body on the concrete road, and n is the number of steel pipe piles arranged.

[0012] Furthermore, the vertical force balance equation of the steel pipe pile in the above-mentioned design method for road settlement support steel pipe piles based on the compression bar stability theory is as follows:

[0013] In this case, f′ and f are action and reaction forces, i.e., |f′|=|f|, F′ cr For the steel pipe pile to be subjected to the vertically upward frictional force of the steel pipe pile, F cr With F′ cr Action and reaction forces, |F′ cr |=|F cr |

[0014] Furthermore, the critical vertical pressure value of the steel pipe pile in the above-mentioned design method for road settlement support steel pipe piles based on the compression bar stability theory is as follows:

[0015]

[0016] Where C0 is a calculation constant and E is the elastic modulus.

[0017] Furthermore, the calculation formula for the outer diameter d1 of the steel pipe pile in the above-mentioned design method for road surface settlement support steel pipe piles based on the compression bar stability theory is as follows:

[0018]

[0019] Where K is the safety factor for the pull-out resistance of the anchor body, and N ak N represents the vertical pressure applied to the steel pipe pile. ak =F cr H is the embedment length of the steel pipe pile, l a l is the anchorage length of the steel pipe pile. a =H; d2 is the inner diameter of the steel pipe pile, fb This is the design value for the bond strength between the steel pipe and the anchoring mortar.

[0020] Furthermore, the calculation formula for the borehole diameter D of the steel pipe pile in the above-mentioned design method for road surface settlement support steel pipe piles based on the compression bar stability theory is as follows:

[0021]

[0022] Where K is the safety factor for the pull-out resistance of the anchor body; N ak N represents the vertical pressure applied to the steel pipe pile. ak =F cr ;l a d1 is the anchorage length of the steel pipe pile; d2 is the outer diameter of the steel pipe pile; f is the outer diameter of the steel pipe pile. rbk This is the standard value of the ultimate bond strength between the concrete road and the anchor body.

[0023] To address road subsidence caused by subgrade soil liquefaction, steel pipe piles are installed at the subsidence end. Grouting is then performed through drilling at the top of the road to achieve a rigid and effective connection between the steel pipe piles and the road, thereby transferring the road load to the deep, stable rock bearing layer. Furthermore, pre-drilled holes in the steel pipes allow for localized grouting reinforcement of the liquefied soil, improving its overall stability. Calculations can determine the minimum number of steel pipe piles required, ensuring the quality of the reinforcement and support project while also saving on project costs. Attached Figure Description

[0024] Figure 1 Schematic diagram of steel pipe pile support reinforcement for subsided roads in this embodiment of the invention;

[0025] Figure 2 Stress analysis diagram of the subsided road in this embodiment of the invention;

[0026] Figure 3 This is a stress analysis diagram of a single steel pipe pile anchor body in an embodiment of the present invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the present invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the present invention. In the description of the present invention, it should be noted that the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0028] Roadbeds are exposed to the natural environment for extended periods. Factors such as soil weight, traffic loads, and rainwater infiltration cause uneven deformation. Furthermore, the shear strength of sandy or silty soil in the foundation depends primarily on the skeletal interaction between soil particles. When saturated sandy or silty soil is subjected to vibration, pore water pressure increases, effective stress decreases, and shear strength declines. At a certain level of vibration, soil particles become suspended, effective stress completely disappears, and shear strength becomes zero. The foundation soil then becomes a flowable water-soil mixture, a phenomenon known as foundation soil liquefaction. Foundation soil liquefaction can lead to ground subsidence, especially on pavements constructed from silty clay, where this phenomenon is highly likely to occur.

[0029] refer to Figure 1 There is a highway that is constructed with concrete. According to the survey data, the bearing layer of the roadbed is a soil-rock mixture, which includes two types: silty clay and moderately weathered sandstone. Surface water infiltration and road vibration loads cause the silty clay to liquefy, resulting in the loss of soil mechanical strength, which in turn induces the overturning and subsidence of the front end of the road.

[0030] The top of the steel pipe is embedded into the concrete road through drilling and grouting. After penetrating the concrete road, it continues to penetrate the silty clay layer. Finally, the bottom is drilled and grouted to embed it into the moderately weathered sandstone. The embedding length is half the thickness of the silty clay layer. However, the number of steel pipes needs to be calculated to determine the minimum value to ensure the stability of the road reinforcement and support.

[0031] First, the following road surface data were obtained through measurement: road width L, thickness H, weight G, and uniformly distributed load q. Then, the following soil data were obtained through measurement: distribution range length L1 of moderately weathered sandstone, distribution range length L2 of silty clay, and thickness l of silty clay layer. Next, the embedment length H of steel pipe, borehole diameter D, and outer diameter d1 and inner diameter d2 of steel pipe pile were obtained.

[0032] refer to Figure 2 A stress analysis was performed on the subsided road. Vertically downward, it is subjected to gravity G and road surface load qL; vertically upward, it is subjected to the resultant force of frictional forces from all the steel pipe pile anchors, which is f. s Given that the supporting force of the medium-graded sandstone subgrade is N, the vertical force equilibrium equation and the bending moment equilibrium equation at point o at the rear end of the road are established as follows:

[0033] f s +N=G+qL (1)

[0034]

[0035] Among them, f s = f × n, where f is the frictional force of a single steel pipe pile anchor body on the concrete road, and n is the number of steel pipe piles arranged.

[0036] Next, refer to Figure 3A force analysis is performed on the anchor body of a single steel pipe pile. Vertically downward, it is subjected to the frictional force f′ of the concrete road, where f′ and f are action and reaction forces. Vertically upward, it is subjected to the frictional force F′ of the steel pipe pile. cr F cr With F′ cr The vertical force equilibrium equations are established based on the interaction of action and reaction forces:

[0037] f′=F′ cr (3)

[0038] Where, |f′|=|f|;|F′ cr |=|F cr |,F cr The maximum vertical pressure that a steel pipe pile can withstand can be derived from the relevant physical and mechanical parameters of the steel pipe pile.

[0039] Because the silty clay subgrade liquefies, resulting in a loss of mechanical strength, the steel pipe piles embedded in the liquefied silty clay will not be constrained by the surrounding soil. This can be simplified to the top being subject to a lateral constraint force F from the road. R The stability mechanics problem of a compression column with a cantilever segment length l, and the existence of a critical vertical pressure value F. cr This causes the steel pipe pile to be in a critical stable state under compression, which is the maximum vertical pressure value that the steel pipe pile can withstand. This value can be obtained from the relevant physical and mechanical parameters of the compression member, as shown in the following formula:

[0040]

[0041] Where C0 is a calculation constant and E is the elastic modulus;

[0042] Determine the outer diameter d1 and inner diameter d2 of the steel pipe pile to satisfy the formula for verifying the bond strength between the anchor body and the steel pipe pile, as shown in the following formula:

[0043]

[0044] Where K is the safety factor for the pull-out resistance of the anchor body; N ak N represents the vertical pressure applied to the steel pipe pile. ak =F cr ;l a l is the anchorage length of the steel pipe pile. a =H; d2 is the inner diameter of the steel pipe pile; f b This is the design value for the bond strength between the steel pipe and the anchoring mortar.

[0045] Based on the formula for verifying the bond strength between the anchor body and the borehole wall concrete, the length of the steel pipe pile anchor body, i.e., the borehole diameter D, is calculated as follows:

[0046]

[0047] Where K is the safety factor for the pull-out resistance of the anchor body; N ak N represents the vertical pressure applied to the steel pipe pile. ak =F cr ;l a d1 is the anchorage length of the steel pipe pile; d2 is the outer diameter of the steel pipe pile; f is the outer diameter of the steel pipe pile. rbk This refers to the standard value of the ultimate bond strength between the concrete road surface and the anchor body;

[0048] By combining equations (1), (2), (3), and (4), the number of steel pipe piles, n, can be calculated as follows:

[0049]

[0050] Therefore, the minimum number of steel pipe piles required is:

[0051]

[0052] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A design method for road surface settlement support steel pipe piles based on the compression bar stability theory, characterized in that, include: The data measurement steps yielded the following road surface data: road width. ,weight The road surface of the subsided road is uniformly distributed with load. Further measurements yielded the following soil data: thickness of the silty clay layer. Obtain the outer diameter of the steel pipe pile and inner diameter Determine the width of the subsided road that requires reinforcement. ; The first stress analysis step involves performing a stress analysis on the subsided road and establishing the vertical equilibrium force equation and the bending moment equilibrium equation of the subsided road. The second stress analysis step involves performing a stress analysis on the anchorage of a single steel pipe pile, establishing the vertical force equilibrium equation for the steel pipe pile, and deriving the critical vertical pressure value of the steel pipe pile. ; Based on the vertical equilibrium force equation of the subsided road, the bending moment equilibrium equation of the subsided road, the vertical force equilibrium equation of the steel pipe pile, and the critical vertical pressure value of the steel pipe pile, the minimum number of steel pipe piles to be arranged is calculated. The minimum number of steel pipe piles to be arranged is: ; in, The length of the distribution range of silty clay. To calculate constants, It is the elastic modulus.

2. The design method for road surface settlement support steel pipe piles based on the compression bar stability theory according to claim 1, characterized in that: The vertical equilibrium force equation for the subsided road is as follows: ， in, For the support of the medium-differentiated sandstone subgrade; The moment balance equation for the subsided road is as follows: ， in, The resultant force of all the steel pipe pile anchor body friction forces acting vertically upward on the subsided road, and , The frictional force between the anchor body of a single steel pipe pile and the concrete road surface. The number of steel pipe piles to be arranged. This represents the length of the distribution range of moderately weathered sandstone.

3. The design method for road surface settlement support steel pipe piles based on the compression bar stability theory according to claim 1, characterized in that: The vertical force balance equation of the steel pipe pile is: ， in, The frictional force between the anchor body of a single steel pipe pile and the concrete road surface. To account for the frictional force of the concrete road, a force analysis is performed on the anchor body of a single steel pipe pile, which is subjected to the vertically downward frictional force of the concrete road. and Action and reaction forces, i.e. , The steel pipe pile is subjected to a vertically upward frictional force. and Action and reaction forces are mutually exclusive. .

4. The design method for road surface settlement support steel pipe piles based on the compression bar stability theory according to claim 3, characterized in that: The critical vertical pressure value of the steel pipe pile is as follows: 。 5. The design method for road surface settlement support steel pipe piles based on the compression bar stability theory according to claim 1, characterized in that: The outer diameter of the steel pipe pile The calculation formula is as follows: ， in, This refers to the standard value of the ultimate bond strength between the concrete road surface and the anchor body. The safety factor for the pull-out resistance of the anchor body. The embedment length of the steel pipe pile is given. This refers to the anchorage length of the steel pipe pile. ; This is the design value for the bond strength between the steel pipe and the anchoring mortar.

6. The design method for road surface settlement support steel pipe piles based on the compression bar stability theory according to claim 1, characterized in that: The borehole diameter of the steel pipe pile The calculation formula is as follows: ， in, The embedment length of the steel pipe pile is given. The safety factor for the pull-out resistance of the anchor body; This represents the vertical pressure applied to the steel pipe pile. ; This refers to the anchorage length of the steel pipe pile; This is the standard value of the ultimate bond strength between the concrete road and the anchor body.

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