Steel pipe pile penetration depth and bearing capacity budget method

Abstract

The application discloses a novel steel pipe pile extension depth into soil layer and bearing capacity budget method, comprising: S1, obtaining the geotechnical parameters of each soil layer at a non-in-situ test pile; S2, setting the values of correction coefficient A and correction coefficient B, and calculating the vertical bearing capacity characteristic value R of the steel pipe pile by using formula 1 a and the preliminary pile length; S3, obtaining the actual value Ra' by the non-in-situ test pile, and when the actual value Ra' is less than the calculated value R a , performing S4; S4, obtaining the actual values of the pile foundation end resistance, the pile foundation shoe part side friction resistance, the pile foundation residual side friction resistance and the overall vertical bearing capacity by the static load test, and inversely calculating A and B; S5, obtaining the geotechnical parameters at the preset position of the actual pile foundation and the minimum vertical bearing capacity characteristic value to be reached, and obtaining the soil layer depth and the tensile load based on A and B and formula 1. The application has the beneficial effect of accurately predicting the bearing capacity and the depth into the soil layer of the pile foundation under different geological conditions.

Description

Technical Field

[0001] This invention relates to the field of marine engineering platform equipment. More specifically, this invention relates to a method for estimating the depth of steel pipe piles inserted into the soil and their bearing capacity. Background Technology

[0002] For pile foundation engineering, open-type steel pipe piles are commonly used both domestically and internationally for the foundations of offshore power transmission line towers. In some geologically challenging conditions, it is difficult to stop the hammer during the construction of open-type steel pipe piles, making it difficult to meet design requirements such as compressive bearing capacity. Furthermore, the actual pile length often differs significantly from the design length, leading to difficulties in ensuring construction quality. Based on past experience, existing technologies involve adding vane-type or fully enclosed pile shoes to the bottom of the open-type steel pipe piles to improve the pile tip bearing capacity and address the issues of difficulty in stopping the hammer and insufficient compressive bearing capacity during pile foundation construction. However, for pile foundations with high design requirements for both tensile and compressive bearing capacity, adding vane-type or fully enclosed pile shoes to the bottom of the open-type steel pipe piles is insufficient to meet the design requirements, and construction quality remains difficult to guarantee.

[0003] After designing and constructing pile foundations that can simultaneously meet the high requirements for both tensile and compressive bearing capacity, there is still the challenge of predicting the bearing capacity and depth of penetration into the soil under different geological conditions using traditional methods due to the difference in pile foundation structure from existing technologies. This ultimately increases the difficulty of construction operations. Summary of the Invention

[0004] One object of the present invention is to solve at least the above-mentioned problems and to provide at least the advantages that will be described later.

[0005] To achieve these objectives and other advantages according to the present invention, a method for estimating the depth of steel pipe pile penetration into the soil and its bearing capacity is provided, comprising the following steps:

[0006] S1. Geological exploration yields geotechnical parameters for each soil layer at the non-in-situ test pile location. These parameters include soil layer type, soil layer thickness, standard value of ultimate side friction resistance, and standard value of ultimate end resistance.

[0007] S2. Set the values ​​of the pile shoe ultimate side resistance correction coefficient A and the pile shoe ultimate end resistance correction coefficient B, and use Formula 1 to initially calculate the characteristic value of the vertical bearing capacity of the steel pipe pile. R a And calculate the preliminary pile length of the steel pipe pile;

[0008] Formula 1

[0009] in, K Indicates the safety factor. Q SK1This represents the standard value of the total ultimate lateral resistance of the non-pile shoe section. Q SK2 This represents the standard value of the total ultimate lateral resistance of the pile shoe segment. Q PK This represents the standard value of the total ultimate end resistance at the pile shoe. u This indicates the perimeter of the steel pipe pile. q sik Indicates the first steel pipe pile i Standard value of ultimate lateral resistance of soil layers l i Indicates the first steel pipe pile i The thickness of the soil layers, l c This indicates the thickness of the Y-shaped outer flange plate entering the bearing soil layer. u c This indicates the outer perimeter of the steel pipe pile body at the location where the Y-shaped outer flange plate is fixed. q c This represents the standard value of the ultimate lateral resistance of the Y-shaped outer flange plate entering the bearing soil layer. q pk This represents the standard value of the ultimate end resistance of the Y-shaped outer flange plate when it enters the bearing soil layer. A p This represents the area of ​​the outer contour of the pile tip;

[0010] S3. Based on the preliminary pile length obtained in step S2, determine the bearing stratum location and conduct off-site pile testing to obtain the actual value of the vertical bearing capacity of the off-site pile foundation. Ra ´, when the actual value Ra I is less than the value calculated in step S2 R a Then proceed to step S4;

[0011] S4. Obtain the actual values ​​of pile end resistance, pile shoe side friction, remaining pile side friction, and overall vertical bearing capacity through static load tests.

[0012] The actual values ​​of the pile shoe ultimate side resistance correction coefficient A and the pile shoe ultimate end resistance correction coefficient B are obtained by back calculation based on Formula 1.

[0013] S5. Geological exploration yields the geotechnical parameters of the soil layer at the actual pile foundation's preset location and the minimum vertical bearing capacity characteristic value required. Based on the actual values ​​of the pile shoe ultimate side resistance correction coefficient A and the pile shoe ultimate end resistance correction coefficient B, and Formula 1, the depth of the steel pipe pile extending into the soil layer at the actual pile foundation's preset location and the tensile load that satisfy the minimum vertical bearing capacity characteristic value are calculated.

[0014] Preferably, the safety factor K=2.

[0015] Preferably, a location with soil parameters similar to the preset location of the actual pile foundation is selected as the non-in-situ test pile location.

[0016] Preferably, the budgeting method is applicable to the budgeting of steel pipe piles with pile shoes installed, the structure of which includes:

[0017] A ring plate is circumferentially fixed to the inner wall of the steel pipe pile and is disposed near the bottom of the steel pipe pile;

[0018] Multiple bottom stiffening ribs are spaced apart at the bottom of the annular plate, and the sidewalls of the bottom stiffening ribs are fixed to the inner wall of the steel pipe pile.

[0019] Multiple Y-shaped outer flange plates are spaced apart on the outer wall of the steel pipe pile and are located near the bottom of the steel pipe pile.

[0020] Preferably, the bottom stiffening rib is trapezoidal in shape, wider at the top and narrower at the bottom, and its lower end is on the same plane as the bottom of the steel pipe pile;

[0021] The distance from the inner wall of the annular plate to its outer circumference is equal to the length of the upper end of the bottom stiffening rib;

[0022] The lower end of the Y-shaped outer flange plate is located on the same plane as the bottom of the steel pipe pile.

[0023] Preferably, the number of bottom stiffening ribs is 8, and they are evenly distributed along the circumference of the annular plate;

[0024] The number of Y-shaped outer flange plates is 4. Multiple Y-shaped outer flange plates are distributed at equal intervals along the circumference of the steel pipe pile, and each corresponds to one of the 4 bottom stiffening ribs located in the same radial direction.

[0025] Preferably, the length of the Y-shaped outer flange along the axial direction of the steel pipe pile is 5~7.5 m.

[0026] The present invention has at least the following beneficial effects:

[0027] First, a method for estimating the vertical bearing capacity of steel pipe piles was explored. This method can accurately, reliably, and quickly estimate the vertical bearing capacity, pull-out bearing capacity, and depth of penetration into the soil at the preset location of the pile foundation, thereby providing safer and more effective guidance for the design and construction of steel pipe pile lengths.

[0028] Secondly, the steel pipe pile disclosed in this invention effectively solves the compressive bearing capacity problem by setting an annular plate and bottom stiffening ribs, and effectively solves the pull-out bearing capacity problem by setting a Y-shaped outer flange plate, thus effectively ensuring construction quality and improving structural safety during the pile driving process.

[0029] Third, the budgeting method of the present invention is applicable to steel pipe pile construction on land or at sea, under special soft geological conditions, and has strong adaptability and wide applicability.

[0030] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0031] Figure 1 This is a schematic axial cross-sectional view of the steel pipe pile according to one of the technical solutions of the present invention;

[0032] Figure 2 This is a radial cross-sectional schematic diagram of the steel pipe pile according to one of the technical solutions of the present invention. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0034] It should be noted that, unless otherwise specified, the experimental methods described in the following embodiments are all conventional methods, and the reagents and materials described are all commercially available unless otherwise specified. In the description of this invention, the orientation or positional relationship indicated by the terms is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. It does not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0035] This invention provides a method for estimating the depth of steel pipe pile penetration into the soil and its bearing capacity, comprising the following steps:

[0036] S1. Geological exploration yields geotechnical parameters for each soil layer at the non-in-situ test pile location. These parameters include soil layer type, soil layer thickness, standard value of ultimate side friction resistance, and standard value of ultimate end resistance.

[0037] S2. Set the values ​​of the pile shoe ultimate side resistance correction coefficient A and the pile shoe ultimate end resistance correction coefficient B, and use Formula 1 to initially calculate the characteristic value of the vertical bearing capacity of the steel pipe pile. R a And calculate the preliminary pile length of the steel pipe pile;

[0038] Formula 1

[0039] in, K Indicates the safety factor. Q SK1 This represents the standard value of the total ultimate lateral resistance of the non-pile shoe section. Q SK2This represents the standard value of the total ultimate lateral resistance of the pile shoe segment. Q PK This represents the standard value of the total ultimate end resistance at the pile shoe. u This indicates the perimeter of the steel pipe pile. q sik Indicates the first steel pipe pile i Standard value of ultimate lateral resistance of soil layers l i Indicates the first steel pipe pile i The thickness of the soil layers, l c This indicates the thickness of the Y-shaped outer flange plate entering the bearing soil layer. u c This indicates the outer perimeter of the steel pipe pile body at the location where the Y-shaped outer flange plate is fixed. q c This represents the standard value of the ultimate lateral resistance of the Y-shaped outer flange plate entering the bearing soil layer. q pk This represents the standard value of the ultimate end resistance of the Y-shaped outer flange plate when it enters the bearing soil layer. A p This represents the area of ​​the outer contour of the pile tip;

[0040] S3. Based on the preliminary pile length obtained in step S2, determine the bearing stratum location and conduct off-site pile testing to obtain the actual value of the vertical bearing capacity of the off-site pile foundation. Ra ´, when the actual value Ra I is less than the value calculated in step S2 R a Then proceed to step S4;

[0041] S4. Obtain the actual values ​​of pile end resistance, pile shoe side friction, remaining pile side friction, and overall vertical bearing capacity through static load tests.

[0042] The actual values ​​of the pile shoe ultimate side resistance correction coefficient A and the pile shoe ultimate end resistance correction coefficient B are obtained by back calculation based on Formula 1.

[0043] S5. Geological exploration yields the geotechnical parameters of the soil layer at the actual pile foundation's preset location and the minimum vertical bearing capacity characteristic value required. Based on the actual values ​​of the pile shoe ultimate side resistance correction coefficient A and the pile shoe ultimate end resistance correction coefficient B, and Formula 1, the depth of the steel pipe pile extending into the soil layer at the actual pile foundation's preset location and the tensile load that satisfy the minimum vertical bearing capacity characteristic value are calculated.

[0044] like Figures 1-2 As shown in the attached drawings, the symbols in the instruction manual are as follows: 1. Steel pipe pile; 2. Ring plate; 3. Bottom stiffening rib; 4. Y-shaped outer flange plate; 5. Pile shoe 100.

[0045] like Figures 1-2As shown, the budgeting method of the present invention is applicable to the budgeting of steel pipe piles with pile shoes 100 installed, the structure of which includes:

[0046] The annular plate 2 is circumferentially fixed to the inner wall of the steel pipe pile 1 and is disposed near the bottom of the steel pipe pile 1;

[0047] Multiple bottom stiffening ribs 3 are spaced apart at the bottom of the annular plate 2, and the sidewalls of the bottom stiffening ribs 3 are fixed to the inner wall of the steel pipe pile 1.

[0048] Multiple Y-shaped outer flange plates 4 are spaced apart on the outer wall of the steel pipe pile 1 and are located near the bottom of the steel pipe pile 1.

[0049] The bottom stiffening rib 3 is trapezoidal in shape, with a larger upper part and a smaller lower part, and its lower end is located on the same plane as the bottom of the steel pipe pile 1. The bottom stiffening rib 3 is distributed at equal intervals along the circumference of the annular plate 2.

[0050] The distance from the inner wall of the annular plate 2 to its outer circumference is equal to the length of the upper end of the bottom stiffening rib 3;

[0051] The lower end of the Y-shaped outer flange plate 4 is located on the same plane as the bottom of the steel pipe pile 1. The Y-shaped outer flange plate 4 is distributed at equal intervals along the circumference of the steel pipe pile 1 and is located in the same radial direction as multiple bottom stiffening ribs 3. The length of the Y-shaped outer flange plate 4 along the axial direction of the steel pipe pile 1 is 5~7.5 m.

[0052] The combination of the annular plate 2 and the bottom stiffening rib 3 can effectively solve the soil plugging effect problem. Compared with the open steel pipe pile 1 and the steel pipe pile 1 with cross plate pile shoe, it significantly improves the compressive bearing capacity of the pile end. Compared with the fully enclosed pile shoe, it can save material usage and at the same time avoid the problem that the steel pipe pile 1 is difficult to sink to the design elevation during construction, so as to facilitate the sinking of the steel pipe pile 1 during the construction process.

[0053] Multiple Y-shaped outer flange plates 4 are used on the outer side of the steel pipe pile 1, which can effectively increase the contact area between the outer side of the steel pipe pile 1 and the soil, increase the side friction resistance of the steel pipe pile 1, and solve the problem of high pull-out bearing capacity in pile foundation design. At the same time, the uniform distribution of the Y-shaped outer flange plates 4, compared with the "I"-shaped plates or T-shaped plates, has a larger contact area with the soil and has a soil squeezing effect, which is more conducive to improving the side friction resistance of the steel pipe pile 1. Example

[0054] 1. Structure of steel pipe piles:

[0055] At a position 500 mm from the bottom of the steel pipe pile 1, an annular plate 2 is fixed, and eight bottom stiffening ribs 3 are evenly fixed on the annular plate 2. Four Y-shaped outer flange plates 4 are evenly fixed on the outer side of the steel pipe pile 1.

[0056] Among them, the outer diameter of the steel pipe pile 1 is 1100 mm and the wall thickness is 22 mm; the distance from the inner wall of the annular plate 2 to its outer circumference is 250 mm; the bottom stiffening rib 3 is a trapezoidal shape with a larger upper part and a smaller lower part, the length of the bottom stiffening rib 3 along the axial direction of the steel pipe pile 1 is 500 mm, and the lengths of the upper and lower ends of the bottom stiffening rib 3 along the radial direction of the steel pipe pile 1 are 50 mm and 250 mm, respectively; the included angle of the V-shaped side of the Y-shaped outer flange plate 4 is 90°, the length along the axial direction of the steel pipe pile 1 is 7 m, and the radial length is 400 mm. The radial length of the V-shaped side of the Y-shaped outer flange plate 4 along the radial direction of the steel pipe pile 1 is 1 / 2 of the radial length of the entire Y-shaped outer flange plate 4.

[0057] Based on the dimensions of steel pipe pile 1, the following calculations were performed:

[0058] At a conventional cross-section, the outer perimeter of the cross-section of steel pipe pile 1 u It is 3.454 m;

[0059] At the 100mm cross section of the pile shoe, the outer perimeter of the cross section of steel pipe pile 1 u c The cross-sectional area of ​​the pile foundation is 8.572 m. A p It is 1 square meter.

[0060] 2. Geological exploration

[0061] The soil layer information (geotechnical parameters of the soil layer) at the non-in-situ test pile location and the soil layer information (geotechnical parameters of the soil layer) at the proposed pile foundation location (actual preset pile foundation location) are shown in Table 1 and Table 2, respectively:

[0062] Table 1 Soil layer information at non-in-situ pile test sites

[0063]

[0064] Table 2 Soil layer information at the proposed pile foundation location

[0065]

[0066] Table 34 shows the working load information for pile foundations at non-in-situ test pile locations and the working load information for the proposed design pile foundation locations:

[0067] Table 3 Working Load Information

[0068]

[0069] 3. Calculate whether the length of steel pipe pile 1 meets the requirements of non-in-situ test pile (whether it can meet the working load of non-in-situ test pile foundation).

[0070] Based on the test pile load requirements, the initial setting of the non-in-situ test pile insertion length is 50 m. The values ​​of the correction coefficients A and B for the ultimate side resistance and ultimate end resistance of the pile shoe 100 are both 1, and the safety factor K is 2. Formula 1 is used to test the characteristic value of the design vertical bearing capacity at the non-in-situ test pile. R a ,

[0071] Formula 1

[0072] Substituting the specific values, we get:

[0073]

[0074] The characteristic value of its vertical bearing capacity is calculated. R a The vertical bearing capacity is greater than the design value of 12000 kN, and the length of the non-in-situ test pile meets the requirements for non-in-situ test piles.

[0075] 4. Static load test was conducted, and the pile end resistance was found to be 8500 kN, the side friction of the pile shoe 100 was 7500 kN, the remaining side friction of the pile was 9500 kN, and the overall vertical bearing capacity was 25500 kN.

[0076] 5. Back-calculate and determine the actual values ​​of the correction coefficient A for the ultimate side resistance of pile shoe 100 and the correction coefficient B for the ultimate end resistance of pile shoe 100:

[0077]

[0078]

[0079] 6. Calculate the design pile length at the proposed pile foundation location:

[0080] Calculated according to compressive load requirements:

[0081] ;

[0082] ;

[0083] ;

[0084] In addition to the 100mm pile shoe, the length of the steel pipe pile section entering the medium-coarse sand is: ;

[0085] Therefore, the length of the pile foundation penetrating the soil layer is calculated using compressive load: .

[0086] 7. Pull-out load check:

[0087] Characteristic values ​​of side skin resistance in pile foundation design calculations: ;

[0088] The tensile load of 8767 kN is greater than the tensile load requirement of 4000 kN, which meets the design requirements. Therefore, at the proposed pile foundation location, the depth of steel pipe pile 1 into the soil layer is 56.8 m, the compressive load is 26000 kN, and the tensile load is 8767 kN.

[0089] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for budgeting the penetration depth and bearing capacity of a steel pipe pile, characterized by, The method comprises the following steps: S1, obtaining soil parameters of each soil layer at a non-site test pile position through geological exploration, the soil parameters including soil layer type, soil layer thickness, standard value of ultimate side friction resistance of the soil layer, and standard value of ultimate end resistance of the soil layer; S2, set the value of the pile shoe limit side resistance correction coefficient A and the pile shoe limit end resistance correction coefficient B, and preliminarily calculate the vertical bearing capacity characteristic value of the steel pipe pile by using formula 1 R a , and calculate the preliminary pile length of the steel pipe pile; Formula 1 wherein, K represents a safety factor, Q SK1 represents a total ultimate side resistance standard value of a non-shoe section, Q SK2 represents a total ultimate side resistance standard value of a shoe section, Q PK represents a total ultimate tip resistance standard value at a shoe, u represents a circumference of a steel pipe pile body, q sik represents a total ultimate side resistance standard value of a first layer of soil, i l i represents a thickness of a first layer of soil, i l c represents a thickness of a Y-shaped outer flange plate into a bearing stratum of soil, u c represents an outer circumference of a steel pipe pile body where the Y-shaped outer flange plate is fixed, q c represents a total ultimate side resistance standard value of a Y-shaped outer flange plate into a bearing stratum of soil, q pk represents a total ultimate tip resistance standard value of a Y-shaped outer flange plate into a bearing stratum of soil, A p represents a pile tip outer contour area of a shoe pile tip,​​ S3, based on the preliminary pile length obtained in step S2, determine the position of the bearing stratum to perform non-situ test pile, and test to obtain the actual value of the vertical bearing capacity of the non-situ test pile Ra ´, when the actual value Ra ´ is less than the calculated value R a in step S2, step S4 is performed; S4, obtaining actual values of the end resistance of the pile foundation, the side friction resistance of the pile shoe part of the pile foundation, the residual side friction resistance of the pile foundation, and the overall vertical bearing capacity through a static load test; Based on formula 1, the actual values of the pile shoe ultimate side resistance correction coefficient A and the pile shoe ultimate end resistance correction coefficient B are obtained. S5, obtaining soil parameters of the soil layer at the actual pile foundation preset position and a minimum vertical bearing capacity characteristic value to be reached through geological exploration, and budgeting the soil layer depth and the tensile load of the steel pipe pile inserted into the actual pile foundation preset position to meet the minimum vertical bearing capacity characteristic value based on the actual values of the pile shoe ultimate side resistance correction coefficient A and the pile shoe ultimate end resistance correction coefficient B and formula 1. The budget method is suitable for budgeting of a steel pipe pile provided with a pile shoe, and the structure of the pile shoe comprises: a ring-shaped plate fixed to the inner wall of the steel pipe pile in the circumferential direction and arranged close to the bottom of the steel pipe pile; a plurality of bottom stiffening ribs arranged at intervals at the bottom of the ring-shaped plate, and the side wall of the bottom stiffening rib is fixed to the inner wall of the steel pipe pile; a plurality of Y-shaped outer flange plates arranged at intervals on the outer wall of the steel pipe pile and arranged close to the bottom of the steel pipe pile; the bottom stiffening rib is a trapezoidal shape with the upper part larger than the lower part, and the lower end is located in the same plane as the bottom of the steel pipe pile; the distance from the inner wall of the ring-shaped plate to the outer circumferential direction is equal to the length of the upper end of the bottom stiffening rib; the lower end of the Y-shaped outer flange plate is located in the same plane as the bottom of the steel pipe pile.

2. The steel pipe pile penetration depth and bearing capacity budgeting method according to claim 1, characterized by, The safety factor K is 2.

3. The steel pipe pile penetration depth and bearing capacity budgeting method according to claim 1, wherein, The position close to the actual pile foundation preset position is selected as the non-site test pile position.

4. The steel pipe pile penetration depth and bearing capacity budgeting method of claim 1, wherein, The number of bottom stiffening ribs is 8, and they are distributed at equal intervals along the circumferential direction of the ring-shaped plate; the number of Y-shaped outer flange plates is 4, and a plurality of Y-shaped outer flange plates are distributed at equal intervals along the circumferential direction of the steel pipe pile, and each corresponds to one of the four bottom stiffening ribs in the same radial direction.

5. The steel pipe pile penetration depth and bearing capacity budgeting method of claim 1, wherein, The length of the Y-shaped outer flange plate along the axial direction of the steel pipe pile is 5-7.5 m.

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