Calculation method and device for pile foundation lateral friction and exertion coefficient considering interface shape

Abstract

The present invention relates to the technical field of pile foundation lateral friction calculation technology, and specifically to a method and device for calculating pile foundation lateral friction and its utilization coefficient, taking into account interface shape. The method for calculating pile foundation lateral friction taking into account interface shape includes: obtaining a hole shape diagram of a borehole wall and extracting a hole wall curve corresponding to the hole shape diagram; classifying the interface shapes of the hole wall curve and calculating the length proportion of each type of interface shape in the hole wall curve; performing a shear test corresponding to each type of interface shape to obtain the shear strength corresponding to each type of interface shape; and calculating the pile foundation lateral friction f of the bored pile based on the length proportion and shear strength of each type of interface shape. The present invention can obtain relatively accurate lateral friction and lateral friction utilization coefficient.

Description

Technical Field

[0001] This invention relates to the field of pile foundation side skin friction calculation technology, and specifically to a method and apparatus for calculating pile foundation side skin friction and utilization factor considering interface shape. Background Technology

[0002] The side skin friction utilization factor is one of the important parameters in the design of rock-socketed piles. When calculating the characteristic value of the axial compressive bearing capacity of a single pile, the side skin friction utilization factor is needed to calculate the pile's side bearing capacity. The relationship between side skin friction and the utilization factor is: f = c²f rk Where c2 is the side skin friction utilization coefficient, and f is the side skin friction of the pile in the rock-socketed section of the pile foundation, i.e., the shear strength of the pile-rock interface. rk The saturated uniaxial compressive strength of the rock along the pile, i.e., the side skin friction utilization coefficient c2, is the ratio of the pile-rock interface shear strength to the saturated uniaxial compressive strength of the rock. The pile-rock interface shear strength can be obtained through direct shear tests.

[0003] In relevant standards, the value range for the side skin friction utilization coefficient is 0.03 to 0.05, which is a method for determining the value of relatively homogeneous terrigenous rocks. However, for heterogeneous rock strata, such as reef limestone, which is a major component of marine island and reef geology, reef limestone, being formed by marine biological cementation and sedimentation, has uneven porosity within the rock mass. Brittleness, porosity, and heterogeneity are the most typical characteristics of reef limestone and one of the biggest differences from terrigenous rocks. When drilling pile foundations in heterogeneous rock strata, the borehole walls are also non-uniform and irregular, resulting in a significant difference between the pile foundation and the rock strata interface after grouting and that in homogeneous rock strata. This leads to a considerable difference in the value of the side skin friction utilization coefficient, making the calculation of side skin friction based on the standard values ​​inaccurate. Therefore, a method is needed to determine the side skin friction and utilization coefficient of cast-in-place piles in heterogeneous rock strata, thereby optimizing pile foundation design methods, enhancing pile foundation safety, and saving costs. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a method and apparatus for calculating the side friction resistance and utilization coefficient of pile foundations, taking into account the interface shape, which can yield more accurate side friction resistance and side friction resistance utilization coefficient.

[0005] To address the aforementioned technical problems, this invention provides a method for calculating the side skin friction of pile foundations considering interface shape, comprising:

[0006] Obtain the borehole shape diagram of the borehole wall and extract the corresponding borehole wall curve;

[0007] The interface shapes of the orifice wall curves are classified, and the length proportion of each interface shape in the orifice wall curves is statistically analyzed.

[0008] Perform shear tests for each type of interface shape to obtain the shear strength for each type of interface shape.

[0009] The pile foundation side friction f is calculated based on the length ratio of various interface shapes and shear strength.

[0010] Furthermore, the method for obtaining the borehole shape diagram of the borehole wall and extracting the corresponding borehole wall curve includes: using an ultrasonic borehole quality tester to measure the borehole shape diagram along the x and y directions, wherein the x direction is perpendicular to the y direction, and the plane containing the x and y directions is perpendicular to the borehole axis; and extracting two borehole wall curves characterizing the borehole wall morphology from each borehole shape diagram.

[0011] Furthermore, the interface shape includes seven types: smooth planar surface, beveled serration, stepped serration, outer arc serration, outer V-serration, inner arc serration, and inner V-serration.

[0012] The orifice wall curves are classified according to the seven interface shapes mentioned above, and the length ratio of each interface shape in the orifice wall curves is statistically analyzed.

[0013] Furthermore, the methods for classifying the orifice wall curves according to the aforementioned seven interface shapes include:

[0014] The hole wall curve is segmented into multiple hole wall segment curves with a unit length of b. These multiple hole wall segment curves are then input into a preset network model, and the interface shape corresponding to each hole wall segment curve is output.

[0015] Furthermore, the method for calculating the length proportion of various interface shapes in the borehole wall curve includes: calculating the length proportion of each interface shape in each borehole wall curve, summing the length proportions of the same interface shape in all borehole wall curves and calculating the average value, which is the length proportion of various interface shapes corresponding to the borehole.

[0016] Furthermore, the shear test includes:

[0017] Core sampling is performed to prepare n shear specimens, where n is the number of interface shapes included in the borehole wall curve, n≤7. The shear specimen includes an upper part and a lower part. The upper part is a heterogeneous rock sample and the lower part is a concrete sample. The interface shape between the two is prepared according to the various interface shapes corresponding to the borehole wall curve. The interface filling form between the upper and lower parts of the shear specimen is set according to the type of pile foundation.

[0018] Shear tests were conducted on the shear specimens to obtain the shear strengths f1, f2, ..., f1 corresponding to various interface shapes. n .

[0019] Furthermore, the interface filling methods between the upper and lower halves of the shear specimen include casting, post-grouting, no filling, and mud surface filling.

[0020] Furthermore, the methods for preparing shear specimens for interface filling methods such as casting, post-grouting, no filling, and mud surface filling are as follows:

[0021] Casting: The heterogeneous rock sample is placed on the undried concrete sample and cured to obtain the shear test specimen.

[0022] Post-grouting: After the heterogeneous rock sample is bonded to the dried concrete sample, cement grout is injected into the gap between the two. After curing, a shear test specimen is obtained.

[0023] Unfilled: The heterogeneous rock sample is directly bonded to the dried concrete sample to obtain the shear test specimen;

[0024] Mud Surface Filling: Cement slurry is applied to the surface of the heterogeneous rock sample and pressed tightly against the dried concrete sample. After curing, a shear test specimen is obtained.

[0025] Furthermore, the pile foundation side friction resistance f = f1×a1 + f2×a2 + ... + f n ×a n , where a n This represents the length percentage of the nth type of interface shape.

[0026] Secondly, the present invention provides a method for calculating the utilization coefficient of pile foundation side skin friction considering interface shape, including:

[0027] Saturated uniaxial compression tests were conducted on rock samples to obtain the saturated uniaxial compressive strength f of the rock along the pile. rk ;

[0028] Calculate the side friction coefficient c2 = f / f rk .

[0029] Thirdly, the present invention provides a non-transitory computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the pile foundation side friction calculation method considering interface shape and the steps of the utilization coefficient calculation method.

[0030] Fourthly, the present invention provides a computer program product, including a computer program / instruction that, when executed by a processor, implements the steps of the pile foundation side friction calculation method considering interface shape and the steps of the utilization coefficient calculation method.

[0031] The beneficial effects of this invention are as follows:

[0032] 1. This invention divides the interface shape into seven types and designs shear tests according to different cross-sectional shapes to calculate the side friction resistance of pile foundations in heterogeneous rock strata, thereby obtaining a more accurate side friction resistance utilization coefficient, which can solve the problem that the side friction resistance utilization coefficient in the specification is not accurate enough.

[0033] 2. This invention, by accurately calculating the side friction coefficient, can guide the optimization of pile foundation design, enhance the safety of pile foundations, and save costs. Attached Figure Description

[0034] Figure 1 The hole wall curves are extracted from the hole shape diagrams along the x and y directions in Embodiment 1 of the present invention.

[0035] Figure 2 The diagram shows the shear specimen model for the seven interface shapes of this invention.

[0036] Figure 3 These are experimental diagrams of shear specimens with seven interface shapes according to the present invention. Detailed Implementation

[0037] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0038] Example 1

[0039] This embodiment provides a method for calculating the side skin friction of pile foundations considering the interface shape, including:

[0040] Step 1: Obtain the borehole shape diagram of the borehole wall and extract the corresponding borehole wall curve. According to Articles 4.1 and 4.3.3 of the "Technical Specification for Testing Piles in Highway Engineering", it is generally assumed that the pile hole is a standard circle and the deviation caused by irregularity in the diameter of the hole is ignored. The borehole shape is characterized by ultrasonic drilling diagrams in two orthogonal directions.

[0041] Step one specifically includes:

[0042] An ultrasonic borehole quality testing instrument was used to measure the borehole shape along the x and y directions, where the x-direction is perpendicular to the y-direction, and the plane containing the x and y directions is perpendicular to the borehole axis. Two borehole wall curves characterizing the borehole wall morphology were extracted from each borehole shape image. Data preprocessing was performed, including noise removal and data smoothing, to obtain the following results: Figure 1 The hole wall curve is shown.

[0043] Step 2: Classify the interface shapes of the orifice wall curves and calculate the length proportion of each type of interface shape in the orifice wall curves; Step 2 specifically includes:

[0044] Seven interface shapes are defined: smooth plane, beveled serration, stepped serration, outer arc serration, outer V-serration, inner arc serration, and inner V-serration. Figure 2 As shown;

[0045] Each borehole wall curve is segmented into multiple segmented borehole wall curves with a unit length of b = 1m. These multiple segmented borehole wall curves are input into a preset network model, and the interface shape corresponding to each segmented borehole wall curve is output. In this embodiment, all segmented borehole wall curves can be divided into seven types. The length ratio of the seven interface shapes corresponding to the four borehole wall curves is calculated. The length ratio of the same interface shape in the four borehole wall curves is summed and the average value is calculated to obtain the length ratio of the seven interface shapes corresponding to the borehole. The length ratio of the seven interface shapes is shown in Table 1.

[0046] Table 1

[0047]

[0048]

[0049] In this embodiment, the network model adopts the SVM split network model, and the method for establishing this network model includes:

[0050] Collect historical data: Collect enough borehole wall curves (e.g., 1000);

[0051] Data segmentation: The collected borehole wall curves are segmented along the pile depth direction in units of 1m to form borehole shape data with a unit length of 1m;

[0052] Data normalization: Normalize the hole shape data with a unit length of 1m. Among them, X e X represents the original eigenvalues. min To select the eigenvalue with the smallest value within this unit length, X max To select the eigenvalue with the largest value within this unit length, These are the normalized values ​​of the eigenvalues.

[0053] Labeling: Classify and label historical data, dividing it into 7 interface shapes: smooth plane, serrated bevel, stepped serrated, outer arc serrated, outer V serrated, inner arc serrated, and inner V serrated, forming a historical dataset.

[0054] Deep learning network, establishing an SVM network model: An SVM splitting network model is established using historical datasets for training and testing. The establishment of this SVM splitting network model is a current technology.

[0055] Step 3: Conduct shear tests for each type of interface shape to obtain the shear strength corresponding to each type of interface shape; Step 3 specifically includes:

[0056] Core samples were taken from the rock strata at the project site, and seven shear test specimens were prepared, such as... Figure 2 , 3 As shown, the shear specimen consists of an upper part and a lower part. The upper part is a heterogeneous rock sample, and the lower part is a concrete sample. The interface shape between the two is made according to various interface shapes corresponding to the pore wall curve.

[0057] The interface filling method between the upper and lower halves of the shear test specimen is set according to the type of pile foundation. The interface filling methods include casting, post-grouting, no filling, and mud surface filling. Among them, the interface filling method corresponding to the integral grouting after drilling with clear water is casting; the interface filling method corresponding to the direct driving of the pile and subsequent cement grouting is post-grouting; the interface filling method corresponding to the direct driving of the pile is no filling; and the interface filling method corresponding to the mud-walled bored pile is mud surface filling.

[0058] The methods for preparing shear specimens for interface filling methods such as casting, post-grouting, no filling, and mud surface filling are as follows:

[0059] Casting: The heterogeneous rock sample is placed on the undried concrete sample and cured to obtain the shear test specimen.

[0060] Post-grouting: After the heterogeneous rock sample is bonded to the dried concrete sample, cement grout is injected into the gap between the two. After curing, a shear test specimen is obtained.

[0061] Unfilled: The heterogeneous rock sample is directly bonded to the dried concrete sample to obtain the shear test specimen;

[0062] Mud Surface Filling: Cement slurry is applied to the surface of the heterogeneous rock sample and pressed tightly against the dried concrete sample. After curing, a shear test specimen is obtained.

[0063] In this embodiment, the pile foundation is a bored cast-in-place pile, and the interface filling method is casting.

[0064] Shear tests were conducted on the shear specimens to obtain the shear strengths f1, f2, ..., f1 corresponding to various interface shapes. n The specific details are shown in Table 2.

[0065] Table 2

[0066]

[0067]

[0068] Step 4: Based on the length ratio of various interface shapes and shear strength, calculate the pile foundation side friction f = f1×a1 + f2×a2 + ... + f n ×a n , where a n This represents the length percentage of the nth type of interface shape.

[0069] f=17%×3.0+13%×2.7+12%×3.2+16%×2.3+14%×2.0+15%×1.4+13%×2.9=2.48MPa.

[0070] Example 2

[0071] This embodiment provides a method for calculating the pile foundation side friction coefficient considering the interface shape, based on Embodiment 1. The method includes step five: conducting a saturated uniaxial compression test on a rock sample to obtain the saturated uniaxial compressive strength f of the rock along the pile. rk =6.2MPa, calculate the side friction resistance utilization coefficient c2 = f / f rk =0.4.

[0072] In Article 6.3.7 of the "Code for Design of Highway Bridge and Culvert Foundations", the value range of the side friction coefficient c2 for relatively homogeneous terrigenous rocks is 0.03 to 0.05. However, for heterogeneous rock strata (such as reef limestone), the side friction coefficient obtained by test is 0.4, which is ten times the value specified in the code. Therefore, the value of the side friction coefficient has a great impact on the design of pile foundation bearing capacity. The side friction coefficient calculated according to the method of this invention can guide the optimization of pile foundation design.

[0073] Example 3

[0074] This embodiment provides a non-transitory computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the pile foundation side friction calculation method considering interface shape in Embodiment 1 and the steps of the utilization coefficient calculation method in Embodiment 2.

[0075] Example 4

[0076] This embodiment provides a computer program product, including a computer program / instruction. When executed by a processor, the computer program / instruction implements the steps of the pile foundation side friction calculation method considering interface shape in Embodiment 1, and the steps of the utilization coefficient calculation method in Embodiment 2.

[0077] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for calculating the side skin friction of pile foundations considering interface shape, characterized in that: include: Obtain the borehole shape diagram of the borehole wall and extract the corresponding borehole wall curve; The interface shapes of the orifice wall curves are classified, and the length proportion of each interface shape in the orifice wall curves is statistically analyzed. Perform shear tests for each type of interface shape to obtain the shear strength for each type of interface shape. Based on the length proportions of various interface shapes and shear strength, calculate the pile foundation side friction f = f1×a1 + f2×a2 + ... + f n ×a n , where a n f represents the length percentage of the nth type of interface shape. n This represents the shear strength obtained from a shear test for the nth type of interface shape.

2. The method for calculating the side skin friction of pile foundations considering interface shape according to claim 1, characterized in that: The method for obtaining borehole shape diagrams and extracting corresponding borehole wall curves includes: using an ultrasonic borehole quality testing instrument to measure borehole shape diagrams along the x and y directions, wherein the x direction is perpendicular to the y direction, and the plane containing the x and y directions is perpendicular to the borehole axis; and extracting two borehole wall curves characterizing the borehole wall morphology from each borehole shape diagram.

3. The method for calculating the side skin friction of pile foundations considering interface shape according to claim 1, characterized in that: The interface shapes include seven types: smooth planar surface, beveled serrated surface, stepped serrated surface, outer arc serrated surface, outer V-serrated surface, inner arc serrated surface, and inner V-serrated surface. The orifice wall curves are classified according to the seven interface shapes mentioned above, and the length ratio of each interface shape in the orifice wall curves is statistically analyzed.

4. The method for calculating the side skin friction of pile foundations considering interface shape according to claim 3, characterized in that: The methods for classifying orifice wall curves according to the seven interface shapes mentioned above include: The hole wall curve is segmented into multiple hole wall segment curves with a unit length of b. These multiple hole wall segment curves are then input into a preset network model, and the interface shape corresponding to each hole wall segment curve is output.

5. The method for calculating the side skin friction of pile foundations considering interface shape according to claim 4, characterized in that: The method for calculating the length proportion of various interface shapes in the borehole wall curve includes: calculating the length proportion of each interface shape in each borehole wall curve, summing the length proportions of the same interface shape in all borehole wall curves and calculating the average value, which is the length proportion of various interface shapes corresponding to the borehole.

6. The method for calculating the side skin friction of pile foundations considering interface shape according to claim 1, characterized in that: Shear tests include: Core sampling is performed to prepare n shear specimens, where n is the number of interface shapes included in the borehole wall curve, n≤7. The shear specimen includes an upper part and a lower part. The upper part is a heterogeneous rock sample and the lower part is a concrete sample. The interface shape between the two is prepared according to the various interface shapes corresponding to the borehole wall curve. The interface filling form between the upper and lower parts of the shear specimen is set according to the type of pile foundation. Shear tests were conducted on the shear specimens to obtain the shear strengths f1, f2, ..., f1 corresponding to various interface shapes. n .

7. The method for calculating the side skin friction of pile foundations considering interface shape according to claim 6, characterized in that: The interface filling methods between the upper and lower halves of the shear specimen include casting, post-grouting, no filling, and mud surface filling.

8. The method for calculating the side skin friction of pile foundations considering interface shape according to claim 7, characterized in that: The methods for preparing shear specimens for interface filling methods such as casting, post-grouting, no filling, and mud surface filling are as follows: Casting: The heterogeneous rock sample is placed on the undried concrete sample and cured to obtain the shear test specimen. Post-grouting: After the heterogeneous rock sample is bonded to the dried concrete sample, cement grout is injected into the gap between the two. After curing, a shear test specimen is obtained. Unfilled: The heterogeneous rock sample is directly bonded to the dried concrete sample to obtain the shear test specimen; Mud filling: Cement slurry is applied to the surface of the heterogeneous rock sample and pressed tightly against the dried concrete sample. After curing, a shear test specimen is obtained.

9. A method for calculating the utilization factor of a pile foundation side skin friction calculation method considering interface shape according to any one of claims 1 to 8, characterized in that: include: Saturated uniaxial compression tests were conducted on rock samples to obtain the saturated uniaxial compressive strength f of the rock along the pile. rk ; Calculate the side friction coefficient c2 = f / f rk .

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by the processor, it implements the steps of the pile foundation side friction calculation method considering interface shape as described in any one of claims 1 to 8, and the steps of the utilization coefficient calculation method as described in claim 9.

11. A computer program product, comprising a computer program / instructions, characterized in that: When executed by a processor, the computer program / instruction implements the steps of the pile foundation side friction calculation method considering interface shape as described in any one of claims 1 to 8, and the steps of the utilization coefficient calculation method as described in claim 9.

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