Quantitative characterization method for pile side frictional resistance of socketed pile-rock interface

Abstract

The invention relates to a quantitative characterization method for pile side frictional resistance of a socketed pile-rock interface, which comprises the following steps: along the circumferential direction of a circular cross section of a socketed pile, taking a plurality of mark points on the circumference of the cross section; selecting side lines on the side surface of the pile body of the socketed pile, wherein the mark points are in one-to-one correspondence with the side lines; the hole wall of the rock drill hole is uneven, and the side line is also an uneven curve; constructing a geometric contour of the pile-rock interface based on the plurality of side lines corresponding to the plurality of mark points; dividing the side line into a plurality of micro-segments; in the pile length direction, the length of each micro-section is lambda i, and in the pile diameter direction, the height of each micro-section is hi; and laser scanning is conducted on the drilled hole of the rock wall, the actual contour of the hole wall is obtained, the distribution rule of lambda i and hi is determined, data values of lambda i and hi are generated randomly, and then the pile side friction resistance is determined.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering technology, specifically relating to a quantitative characterization method for the pile side friction of the rock-socketed pile interface. Background Technology

[0002] In pile foundation engineering, rock-socketed piles are driven into the rock strata and are in direct contact with the rock layer. The roughness of the pile-rock interface has a significant impact on pile side friction, pile end resistance, and overall bearing capacity. Existing methods for determining pile side friction mainly include qualitative description methods, statistical parametric methods, and experimental fitting methods. Qualitative description methods rely on engineer experience, are highly subjective, and lack unified standards. Statistical parametric methods require the use of the joint roughness coefficient (JRC), but this parameter was originally used for calculating the friction of joint surfaces and is not entirely applicable to pile-rock contact surfaces, which introduces certain errors. Experimental fitting methods indirectly reflect the interface friction characteristics through direct shear or interfacial shear tests, but these tests are costly, inefficient, and destructive, making them difficult to widely apply. Therefore, the field currently lacks a unified, quantifiable method for characterizing the roughness of pile-rock contact surfaces, as well as a method for determining pile side friction at the pile-rock interface. Summary of the Invention

[0003] To address the above problems, this invention provides a method for quantitatively characterizing the pile-rock interface friction of rock-socketed piles, including:

[0004] S1: Along the circumference of the circular cross-section of the rock-socketed pile, take several marking points on the circumference of the cross-section;

[0005] S2: Select side lines on the side of the rock-socketed pile, and mark the points one by one with the side lines; the side lines are uneven curves; construct the geometric outline of the pile-rock interface based on the side lines corresponding to the mark points.

[0006] S3: Divide the side line into several micro-segments, with the length of each micro-segment being λ along the pile length direction. i Along the pile diameter direction, the height of the micro-segment is h. i ;

[0007] S4: Perform laser scanning on the borehole in the rock wall to obtain the actual contour of the borehole wall and determine λ. i with h i The distribution pattern, randomly generated λ i with h i The data values ​​are used to determine the pile side friction resistance.

[0008] Optionally, the rock-socketed pile is cylindrical, with its cross-section parallel to the pile diameter direction and the pile diameter direction perpendicular to the pile length direction; both the top and bottom surfaces of the rock-socketed pile are parallel to the pile diameter direction; the intersection of the side line and the top surface of the rock-socketed pile is the vertex of the side line, and the intersection of the side line and the bottom surface of the rock-socketed pile is the bottom point of the side line; the line connecting the vertex and the bottom point of the side line is the side reference line, which is parallel to the pile length direction.

[0009] Alternatively, the borehole wall of the rock drill is uneven, and concrete is poured into the borehole. After solidification, it forms a rock-embedded pile. Therefore, the side of the rock-embedded pile is also uneven. The side line is a line on the pile-rock contact surface. The side line is an uneven curve and extends along both the pile length direction and the pile diameter direction.

[0010] Optionally, in step S1, the marking point is connected to the center of the corresponding cross-section to form a marking radius, and the angle between the marking radius and the radial vector of the cross-section is θ.

[0011] Optionally, in step S3, the length λ of the micro-segment is along the length direction of the side baseline. i The length of the projection of the micro-segment onto the side baseline; the height h of the micro-segment along the length direction of the mark radius. i It is the perpendicular distance between the point farthest from the side baseline of the micro-segment and the side baseline.

[0012] Optionally, in step S4, the values ​​of θ corresponding to the marker points at different positions on the circumference of the rock-socketed pile cross-section are determined according to the actual contour of the borehole wall.

[0013] Optionally, in step S4, λ is determined using statistical analysis methods, taking into account the actual contour of the hole wall. i with h i The random distribution characteristics of the side lines, λ is randomly generated. i and h i Numerical value.

[0014] Optionally, in step S4, the pile-rock contact surface friction of any micro-segment i of any side line is determined by the following formula:

[0015] ;

[0016] Where, τ i σ is the pile-rock contact surface skin friction, kPa; n0 ρ is the initial value of the normal stress at the pile-rock contact surface, kPa; K is the normal stiffness of the pile-rock contact surface, kPa / mm; s i λ represents the pile-rock relative displacement, in mm; i h is the length of the micro-segment, in mm. i The height of the micro-segment is in mm; b The basic friction angle of the pile-rock contact surface is given in degrees.

[0017] This method is applicable to different types of rock formations, such as intact rock masses, strongly weathered rock masses, and rock masses with well-developed joints and fissures. σ is adjusted according to the burial depth of different rock strata. n0 The values ​​are adjusted to suit different rock strata conditions.

[0018] Further, optionally, the normal stiffness K of the pile-rock contact surface is determined by the following formula:

[0019] ;

[0020] Among them, E r ρ is the elastic modulus of the rock, MPa; μ is the Poisson's ratio of the rock-socketed pile, dimensionless; r p denoted as the cross-sectional radius of the rock-socketed pile, in mm.

[0021] Optionally, when the pile-rock contact surface fails, the pile-rock contact surface frictional resistance is represented by the residual pile-rock contact surface frictional resistance, τ. i 'Determined by the following formula:'

[0022] ;

[0023] Where, τ i 'Residual pile side friction, kPa; s r Residual pile-rock relative displacement, mm; r The residual friction angle at the pile-rock contact surface is expressed in degrees.

[0024] Alternatively, in step S4, in addition to laser scanning, rock wall images can be obtained by combining three-dimensional geological modeling data, borehole television imaging, or high-resolution camera technology.

[0025] Depending on the actual needs of the project, the dimensions of the horizontal boreholes corresponding to the rock-socketed piles vary, ranging from 0.6 to 1.5 meters in diameter and 10 to 25 meters in length, with some even larger-scale boreholes. Existing laser scanners are handheld or portable and can enter the borehole to scan the inner wall. However, given the large borehole size, manually using a handheld laser scanner to inspect the inner wall is impractical and prone to significant errors.

[0026] The present invention also provides a support device for laser scanning borehole wall, including a fixed frame, a rotatable guide rail, a driving part and several support parts. The fixed frame includes a circular bracket, four telescopic support rods and a positioning part. The fixed frame is installed at the opening end of the borehole. The circular bracket is perpendicular to the central axis of the borehole. The positioning part is located at the center of the circular bracket. The four support rods are evenly distributed along the circumference of the circular bracket. The head of the support rod is connected to the positioning part, and the tail of the support rod is used to connect with the inner wall of the borehole to support the fixed frame.

[0027] The guide rail rod has a positioning part and a driving part rotatably connected at both ends, and the support parts are evenly arranged along the length of the guide rail rod. Several laser scanners are slidably connected on the guide rail rod. The driving part can drive the tail end of the guide rail rod to extend into the borehole. The support parts are used to support the guide rail rod. A laser scanner is set between two adjacent support parts.

[0028] This invention can determine the θ value corresponding to any marked point on the side of a rock-socketed pile, i.e., determine the specific location of the side line, and can also determine the pile side friction at any point (i.e., any micro-segment i) on the side line. Thus, it can determine the pile side friction at any location on the pile-rock contact surface. The method of this invention can also be combined with a finite element numerical simulation platform to convert randomly generated pile-rock interface parameters (λ...) i h i It can be directly imported as a boundary condition. This invention has the following advantages:

[0029] (1) A method for multi-scale quantitative characterization of pile-rock contact surface roughness is provided, avoiding human subjectivity. Based on random roughness, this invention makes the results more consistent with engineering practice by discretizing the cross section, generating geometric parameters by random functions and introducing mechanical parameters, thereby effectively improving the scientificity and accuracy of pile side friction prediction and design.

[0030] (2) The laser scanning results are applied to practical engineering projects, making them highly applicable to engineering applications;

[0031] (3) The prediction results can reflect the range of frictional resistance, which is closer to the actual situation and improves the accuracy of bearing capacity prediction;

[0032] (4) The quantitative characterization method described above can adjust K and K respectively in parameter sensitivity analysis. b and r The values ​​of these parameters are used to evaluate their influence on the prediction results of pile side friction. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a rock-socketed pile;

[0034] Figure 2 This is a schematic diagram of the cross-section of a rock-socketed pile;

[0035] Figure 3 This is a schematic diagram of the side line;

[0036] Figure 4 Pile side friction curve (I) (K = 770 kPa·mm) -1 σ n0 is 450 kPa);

[0037] Figure 5 Pile side friction curve (II) (K = 770 kPa·mm) -1 σ n0 is 900 kPa);

[0038] Figure 6 Pile side friction curve (III) (K is 1540 kPa·mm) -1 σ n0 is 450 kPa);

[0039] Figure 7 Pile side friction curve (IV) (K is 1540 kPa·mm) -1 σ n0 is 900 kPa);

[0040] Figure 8 Pile side friction curves when the side line is divided into different numbers of micro-segments;

[0041] Figure 9 This is a data comparison chart showing the use of the comprehensive discrimination method described in the embodiments and the use of no discrimination method.

[0042] Figure 10 A schematic diagram of the support device used for laser scanning of borehole walls;

[0043] Figure 11 This is a schematic diagram of the guide rail rod.

[0044] Among them, 1-marking point, 2-marking radius, 3-side baseline, 4-side line, 5-guide rail rod, 6-driving part, 7-support part, 8-circular bracket, 9-support rod, 10-positioning part, 11-laser scanner, 12-fixed rod, 13-spring, 14-connector, 15-first lifting device, 16-second lifting device, 17-sensor. Detailed Implementation

[0045] This embodiment provides a quantitative characterization method for the pile side friction of the rock-socketed pile interface, including:

[0046] S1: Along the circumference of the circular cross-section of the rock-socketed pile, take several marking points 1 on the circumference of the cross-section;

[0047] S2: Select side line 4 on the side of the rock-socketed pile, and mark the points one by one with the side line; the hole wall of the rock borehole is uneven, and the side line is also an uneven curve; based on the side lines corresponding to the mark points, construct the geometric outline of the pile-rock interface.

[0048] S3: Divide the side line into several micro-segments; the length of each micro-segment is λ along the pile length direction. i Along the pile diameter direction, the height of the micro-segment is h. i ;

[0049] S4: Perform laser scanning on the borehole in the rock wall to obtain the actual contour of the borehole wall and determine λ. i with h i The distribution pattern, randomly generated λ i with h i The data values ​​are used to determine the pile side friction resistance.

[0050] like Figure 1 As shown, the rock-socketed pile is cylindrical, with its cross-section parallel to the pile diameter direction and the pile diameter direction perpendicular to the pile length direction. The side line follows the pile length direction. The top and bottom surfaces of the rock-socketed pile are parallel to the pile diameter direction. The intersection of the side line and the top surface of the rock-socketed pile is the vertex of the side line, and the intersection of the side line and the bottom surface of the rock-socketed pile is the bottom point of the side line. The line connecting the vertex and the bottom point of the side line is the side reference line 3, which is parallel to the pile length direction.

[0051] The borehole wall of the rock is uneven. Concrete is poured into the borehole and solidifies to form a rock-embedded pile. Therefore, the side of the rock-embedded pile is also uneven. The side line is a line on the pile-rock contact surface. The side line is an uneven curve and extends along both the pile length and pile diameter directions.

[0052] like Figure 2 As shown, in step S1, the mark point is connected to the center of the corresponding cross-section to form a mark radius 2, and the angle between the mark radius and the radial vector of the cross-section is θ.

[0053] In step S2, the side line and the corresponding side baseline form an uneven two-dimensional plane. This two-dimensional plane extends along both the pile length direction and the pile diameter direction, and is parallel to the pile diameter direction.

[0054] If enough markers are obtained, all the side lines will form the pile-rock contact surface of the rock-socketed pile, thus constructing the geometric outline of the pile-rock interface.

[0055] like Figure 3 As shown, in step S3, the length λ of the micro-segment is along the length direction of the side baseline. iThe length of the projection of the micro-segment onto the side baseline; the height h of the micro-segment along the length direction of the mark radius. i is the perpendicular distance between the point on the micro-segment furthest from the side baseline and the side baseline. i indicates which micro-segment it is.

[0056] In step S4, based on the actual contour of the borehole wall, the values ​​of θ corresponding to the marker points at different positions on the circumference of the rock-socketed pile cross-section are determined.

[0057] Based on the actual contour of the borehole wall, the specific shape of each sideline as a curve can also be determined. However, because the rough surface of the borehole wall is a microstructure, laser scanning cannot precisely obtain the exact dimensions of every unevenness, i.e., it cannot determine λ. i and h i While the specific numerical value can be obtained, it can roughly describe the concave and convex shape of the side line and correspond the side line to its θ, thereby determining the specific position of the side line.

[0058] In step S4, λ is determined using statistical analysis methods, taking into account the actual contour of the hole wall. i with h i The random distribution characteristics of the side lines, λ is randomly generated. i and h i Numerical value.

[0059] In this example, the included angle θ corresponding to the selected marker point is 30°, the total length of the side line is 340 mm, the side line is randomly divided into 10 non-uniform micro-segments, and the λ of the randomly generated side line... i and h i The values ​​are shown in the table below.

[0060] Table 1 λ of the sideline i and h i Numerical statistics table

[0061] .

[0062] Table 2. λ of the lateral edge after pile-rock contact surface failure. i and h i Numerical statistics table

[0063] .

[0064] h in the table above i A negative value indicates that the corresponding sideline portion is to the right of the side baseline, h i A positive value indicates that the corresponding sideline portion is to the left of the sideline baseline.

[0065] In step S4, the pile-rock contact surface friction resistance of any micro-segment i of any side line is determined by the following formula:

[0066] (1)

[0067] Where, τ i σ is the pile-rock contact surface skin friction, kPa; n0 ρ is the initial value of the normal stress at the pile-rock contact surface, kPa; K is the normal stiffness of the pile-rock contact surface, kPa / mm; s i λ represents the pile-rock relative displacement, in mm; i h is the length of the micro-segment, in mm. i The height of the micro-segment is in mm; b The basic friction angle of the pile-rock contact surface is given in degrees.

[0068] The normal stiffness K of the pile-rock contact surface is determined by the following formula:

[0069] ;

[0070] Among them, E r r is the elastic modulus of the rock, in MPa; μ is the Poisson's ratio of the rock, dimensionless; p denoted as the cross-sectional radius of the rock-socketed pile, in mm.

[0071] When the pile-rock interface fails, the pile-rock contact surface friction is represented by the residual pile-rock contact surface friction, τ. i 'Determined by the following formula:'

[0072] (2)

[0073] Where, τ i 'Residual pile side friction, kPa; s r The residual pile-rock relative displacement (the pile-rock relative displacement when the pile-rock contact surface fails), in mm; r The residual friction angle at the pile-rock contact surface is expressed in degrees.

[0074] Table 3 Parameter List

[0075] .

[0076] Table 4 Test Conditions

[0077] .

[0078] This example provides two types of cross-sectional radii for rock-socketed piles, resulting in two normal stiffnesses K at the pile-rock contact surface: 770 kPa and 1540 kPa. Under different normal stiffnesses K, the initial normal stresses σ are investigated. n0 The side friction of the pile.

[0079] like Figures 4-7 As shown, the horizontal axis is s i and s r The vertical axis represents the pile side friction resistance. When s i When the frictional resistance of the pile increases to a certain extent, it will drop sharply, at which point the pile-rock contact surface will be damaged, and the use of s r To determine the residual pile side friction. For the same s i The value is substituted into different λ values ​​in turn. i and h i Numerical value, so the same s i The value corresponds to 10 pile side friction resistance values; similarly, the same s r The value corresponds to 10 residual pile side friction values.

[0080] The red curve in the figure represents the empirical parameter method, for each s i The value takes only one corresponding λ. i h i The numerical values ​​are used to determine the pile side friction curve. It can be seen that... Figures 4-7 In this example, the pile side friction curve obtained by the method in this example has a good overlap with the pile side friction curve obtained by the empirical parameter method, indicating that the method in this example can be applied to practical engineering.

[0081] This example also examines the use of the method provided by this invention when the side line is randomly divided into 5 and 15 uneven micro-segments. For example... Figure 8 As shown in the above parameter sensitivity analysis, with the increase of the number of micro-segments, the distribution of the calculation results gradually becomes denser, and its statistical characteristics are closer to the results of traditional methods, indicating that the method of the present invention can better approximate engineering reality under the condition of refined division.

[0082] The method of this invention can output the range of values ​​for (residual) pile side friction (i.e., through multiple sets of λ). i h i Numerical determination of multiple (remaining) pile side friction resistances forms a value range, which can cover the calculation results of traditional methods and characterize the randomness, variability and discreteness of actual (remaining) pile side friction resistance.

[0083] To ensure the geometric parameters of the randomly generated pile-rock contact surface (micro-segment length λ) i Micro-segment height h iIn terms of spatial morphology, it maintains consistency with the actual borehole wall contour obtained by laser scanning. Furthermore, this invention proposes a comprehensive discrimination method based on multi-scale spectral-fractal-alignment fusion. Through three levels—multi-scale energy spectrum analysis, fractal self-similarity assessment, and local structure alignment—it achieves a quantitative determination of the global similarity between randomly generated contact surface parameters and the measured contact surface, thereby ensuring that the model conforms to real geological conditions in terms of statistical characteristics and geometric structure. The comprehensive discrimination method includes:

[0084] S401: Signal Construction and Spatial Reference Unification:

[0085] The longitudinal direction of the central axis of the rock-socketed pile is the z-direction. Along the z-direction, the roughness of the pile-rock contact surface is determined by the following formula:

[0086] ;

[0087] Among them, t i (z) represents the inclination tangent of the local rough element along the z direction, reflecting the variation characteristics of the micro-unevenness of the contact surface;

[0088] For the randomly generated sample set t sim (z) and the actual curve t obtained by laser scanning scan (z), preferably, conventional resampling and interpolation are performed under the same spatial reference (i.e., the z-direction) to achieve noise reduction, so that the two have consistent spatial resolution and scale range, providing a unified basis for subsequent comparative analysis.

[0089] S402: Multiscale energy spectrum analysis:

[0090] Multiscale energy spectrum E(s) k It is determined by the following formula:

[0091] ;

[0092] Among them, W(s) k ,z) represents the scale s k The local wavelet coefficients at E(s) are dimensionless; k () represents a multiscale energy spectrum, which is dimensionless and represents the scale s. k The sum of the signal energy reflects the scale s k The strength of the concave-convex structure; k is the index of the scale, that is, the kth scale. If a total of K scales are selected, then k = 1, 2, ..., K; K is the number of scales, which is dimensionless, and preferably K = 6-12.

[0093] s ks is the scaling parameter in wavelet transform, controlling the scaling of the wavelet mother function. It is a mathematical analysis parameter used to describe the spatial hierarchy of a signal, with units of mm. Small scales correspond to high frequencies (i.e., fine structures) and large scales correspond to low frequencies (i.e., macroscopic fluctuations). In this method, s k The size of the spatial "observation window" describes the undulation of the roughness along the pile side; in the pile-rock contact problem, the wavelet transform is expanded along the z-direction, therefore s k The unit should be consistent with the z-axis; for example, if the sampling interval along the z-axis of the contact surface is 1 mm, then s k A scale several times larger than that spacing can be used.

[0094] The roughness is decomposed into multiple scales using the continuous wavelet transform method to obtain the scale s. k Local wavelet coefficients W(s) k ,z):

[0095] ;

[0096] Where z' is the integral variable; ψ is the mother wavelet function (Morlet or Mexican Hat wavelet is recommended); and * denotes complex conjugate.

[0097] The energy spectrum was normalized to make ;

[0098] E(s k The larger the value, the larger the scale s. k The more pronounced the roughness change, the better. (Normalized energy spectrum) This reflects the relative distribution characteristics of roughness energy across different scales.

[0099] S403: Hellinger distance metric:

[0100] To measure the difference in scale energy distribution between randomly generated contact surface parameters and measured contact surface parameters, the Hellinger distance is introduced as a measure of energy spectrum difference. The discrete form of the Hellinger distance is determined by the following formula:

[0101] ;

[0102] Where H(p,q) is the discrete Hellinger distance, dimensionless; p and q are normalized energy spectral vectors, p=p(p1,…, p) k Let q be the normalized energy spectrum vector of the randomly generated contact surface parameters, where q = q(q1, ..., q). k ) represents the normalized energy spectrum vector of the measured contact surface parameters, where p k and q k Represented as:

[0103] ;

[0104] ;

[0105] p k and q k Represents different scales s k The energy distribution ratio under the scale is a "probability vector" in a statistical sense. Its dimension is the number of scales K, not the spatial location. It is used to compare the similarity of energy distribution patterns at multiple scales. Therefore, H(p,q) measures the difference in spectral morphology, not the difference in spatial location.

[0106] In this invention, Hellinger distance measures the similarity of energy distribution morphology. It belongs to the multi-scale statistical layer. H(p,q) compares the energy distribution (statistical morphology) at each scale. The variable type is the energy spectrum probability vector, which has been normalized and is dimensionless, reflecting the overall roughness "spectral similarity".

[0107] Energy spectral vector p = p(p1,…, p) k The source is the wavelet energy spectrum normalization result, which means that the energy proportion of each scale is represented. The mathematical space is the scale domain and has no unit.

[0108] H(p,q)∈[0,1], and H=0 if and only if p=q, this distance satisfies the triangle inequality and is metric;

[0109] Since the square root of the probability density is taken first, the Hellinger distance is relevant to the multi-scale energy spectrum E(s). k The tail-end extrema and noise are robust; H(p,q) remains stable and effective when the energy at some scales approaches zero.

[0110] In numerical implementation, to prevent instability caused by floating-point underflow or zero terms, it is recommended to add a very small positive number ε=10 to each term in the energy spectrum vectors (p and q). -12 Then normalize; and cover several multiples of the scale with a logarithmically equidistant scale sequence (for example, take 3-6 times the scale, the larger the scale, the higher the accuracy and the higher the sensitivity) to take into account the three scale features of coarse, medium and fine.

[0111] Therefore, multi-scale energy spectrum difference index Represented by H(p,q):

[0112] ;

[0113] If H approaches 0, it indicates that the randomly generated contact surface and the contact surface measured by laser scanning are highly consistent in terms of multi-scale energy distribution; if H approaches 1, it indicates that the roughness spectrum morphology of the two is significantly different.

[0114] S404: Fractal Feature Fitting and Spectral Index Determination:

[0115] The energy spectrum of a rough surface follows a typical power-law relationship:

[0116] ;

[0117] Where β is the spectral index, which is dimensionless and reflects the rate of energy decay with scale, and has a clear fractal geometric meaning;

[0118] If β < 1, it indicates that the energy is concentrated in the small-scale structure, and the surface has strong subtle fluctuations; if β ≈ 1, it indicates that the roughness energy distribution is gentle and the surface is relatively smooth; if β > 2, it indicates that the energy is mainly concentrated in the large-scale structure, and the surface has significant undulations.

[0119] Taking the logarithm of the above relationship yields a linear form:

[0120] ;

[0121] The logE(s) was fitted using the least squares linear regression method. k ) and logs k The curve is used to obtain the spectral index β;

[0122] The fractal characteristic difference index is determined by the following formula:

[0123] ;

[0124] Where, β sim β is the spectral index of a random sample. scan ε0 represents the spectral index of the measured sample; ε0 represents the difference between the two spectral indices, reflecting the difference in self-similar structure and scale invariance of the contact surface between the random sample and the measured sample, ε = 10. -12 This is used to avoid the denominator being zero.

[0125] S405: Local structure alignment metric and attenuation coefficient κ:

[0126] To further measure the correspondence between the contact surfaces of random samples and measured samples in local spatial geometry, a local construction alignment metric is introduced. The roughness signal t is extracted using the finite difference method or signal extremum detection algorithms (such as peak-valley detection or the find_peaks algorithm). i The set of local extrema of (z) is:

[0127] ;

[0128] Where, p i simThe coordinates of the i-th peak of the simulated curve (randomly generated) are in mm; p j(i) scan To be with p i sim The coordinates of the most recent measured peak, in mm; L represents the distance difference between the two along the z-direction. Z The total length of the rock-socketed pile is in mm;

[0129] Determine the average normalized misalignment of the two:

[0130] ;

[0131] Where △pos is the proportion of average misalignment to total length, %; and P is the number of matching peaks.

[0132] △pos∈[0,1], the closer △pos is to 0, the more aligned the local peak and valley structures of the random sample with those of the measured sample are; for example, △pos =0.05 indicates that the average peak position shift is 5%.

[0133] p i sim and p j(i) scan This refers to the extreme locations of the spatial signal, representing the positions of local peaks or troughs in the roughness curve along the z-axis. The mathematical space is a spatial domain, and the unit is length (mm). In local structure alignment measurements, p is used... i sim and p j(i) scan The coordinates of the local peaks (or troughs) of the two roughness curves in the z-direction belong to the spatial domain. They represent the geometric feature points of the randomly generated contact surface and the laser-measured contact surface, respectively, used to determine the consistency of the spatial structure. Together, they constitute the multi-dimensional comprehensive discrimination system of this invention. △pos belongs to the spatial structure layer, comparing the correspondence between peak and trough spatial positions. The variable type is a set of peak coordinates, which has been length-normalized, reflecting the "spatial alignment" of the local structure. i sim and p j(i) scan It is the spatial peak position coordinate (geometric layer).

[0134] During the alignment process, it is necessary to establish a correspondence between the local extrema (peaks or valleys) of the two curves:

[0135] Simulated contact surface curve: peak set ;

[0136] Measured contact surface curve: peak set ;

[0137] However, the number of these two sets of extreme values ​​may differ, and their positions may not be entirely consistent. Therefore, it is necessary to define each p... i sim Find the closest peak p in the scan curve. j scan And denote its index as j(i), then p j(i) scan Let j(i) be the position of the scan peak that is closest to the i-th simulated peak. Thus, j(i) is a mapping function that represents "simulated peak i → corresponding scan peak number".

[0138] This invention addresses each local extreme point of the simulated curve. In the set of extreme values ​​of the scanning curve In the search, find the extreme point p that is closest to its location. j(i) scan Determine and normalize the axial distance difference between the two; then average over all i to obtain the average normalized misalignment Δpos.

[0139] Determine the local structural alignment A:

[0140] ;

[0141] Where A is the local structural alignment degree, dimensionless, 0<A≤1; κ is the attenuation coefficient, dimensionless, used to control the intensity of the influence of peak position shift on alignment degree (i.e., to control the sensitivity of A to the change of misalignment).

[0142] The function is exponentially decaying. When Δpos=0, A=1, indicating perfect alignment. As Δpos increases, A decays exponentially, rapidly decreasing from 1 to close to 0. The larger κ is, the faster the curve decays and the stricter the judgment. The smaller κ is, the slower the decay and the more misalignment is tolerated.

[0143] when When the value is 8-10, the exponential decay curve drops sharply, and even a slight misalignment can cause significant decay, which is considered a significant misalignment, and the judgment criteria are relatively strict.

[0144] when When the value is 3-5, the exponential decay curve is flat, allowing for a certain degree of local structural misalignment, with a high tolerance and lenient judgment.

[0145] Numerical characteristics and typical interval analysis of κ: In order to make the formula interpretable in engineering, its attenuation characteristics can be viewed mathematically. When Δpos=0.1 (i.e., the average misalignment is 10% of the pile length interval), the analysis is as follows.

[0146] Table 5. Analytical results under different κ and A values

[0147] .

[0148] Recommended value range and physical interpretation;

[0149] Based on the morphological characteristics of the pile-rock contact surface, the local offset introduced by rock surface scanning error and resampling is typically 3%-7%. In engineering practice, if it is desired that the randomly generated contact surface morphology closely matches the contact surface height measured by laser scanning, then A≈0.4-0.5 should be achieved for a 10% misalignment. Therefore:

[0150] Table 6. Applications of the range of values ​​for κ in engineering.

[0151] .

[0152] As shown in the table above, in general engineering applications, it is recommended that κ be 5 to 7 to balance matching sensitivity and error tolerance.

[0153] S406: Comprehensive Discriminant Index and ROC Threshold Calibration Mechanism

[0154] Based on the combined results of multi-scale energy spectrum differences, fractal self-similarity differences, and local structure alignment, the final comprehensive discrimination index is determined by the following formula:

[0155] ;

[0156] Where w1+ w2+ w3=1, the recommended initial weight value is (w1, w2, w3)=(0.5,0.25,0.25), which can also be adjusted according to the focus of the project to enhance the influence of specific indicators;

[0157] When Ψ≤η, the randomly generated pile-rock contact surface is considered to be close to the measured contact surface in terms of multi-scale structural characteristics; if Ψ>η, it is judged to be significantly different.

[0158] The threshold η is determined using the Receiver Operating Characteristic (ROC) method, as follows:

[0159] Collect several sets of known randomly generated numerical samples of the contact surface (including samples that are close to the measured contact surface values ​​and samples that are not close to the measured contact surface values); calculate the discrimination index Ψ for each sample.

[0160] Using different thresholds η, the true positive rate and false positive rate were calculated separately.

[0161] True Positive Rate (TPR): The proportion of samples that are correctly identified as Ψ≤η in a sample that closely approximates the measured contact surface.

[0162] False Positive Rate (FPR): The proportion of samples that are not actually close to the measured contact surface and are identified as having Ψ≤η.

[0163] Plot the TPR-FPR curve (i.e., the ROC curve) and select η as the optimal threshold corresponding to the best balance point that makes TPR high and FPR low at the same time.

[0164] This calibration process can objectively determine the discrimination criteria, ensuring that the above methods remain stable and repeatable under different lithological conditions.

[0165] Compared with existing statistical matching methods for generating random roughness, the comprehensive discrimination method of the present invention has the following advantages:

[0166] (1) Introduction of multi-scale energy spectrum features: continuous wavelet transform is used to describe the distribution of roughness energy at different scales, revealing the hierarchical relationship between macroscopic fluctuations and microscopic textures;

[0167] (2) Hellinger distance is used for spectral shape comparison: it compares spectral shape differences in the form of probability distribution, avoids interference from energy amplitude differences, and is robust to noise and extreme values;

[0168] (3) Fractal spectral index fitting mechanism: Determining the spectral index based on power law regression Quantitative characterization of surface self-similarity features reveals the scale invariance of rough structures;

[0169] (4) Introduction of local construction alignment metric: Through extreme value matching and decay function control, a quantitative description of the spatial consistency of microstructure is achieved;

[0170] (5) Comprehensive index fusion mechanism: Construct a comprehensive discriminant function Ψ that includes spectral difference, fractal difference and alignment, and evaluate the "proximity" of the randomly generated and measured contact surfaces in a unified manner in the three dimensions of probability, geometry and space;

[0171] (6) ROC calibration improves practicality: Thresholds are calibrated by the receiver operating characteristic curve to achieve objectivity and reproducibility of the model judgment criteria.

[0172] In summary, the comprehensive discrimination method, through a multi-scale-fractal-alignment fusion discrimination mechanism, ensures that the randomly generated pile-rock contact surface is consistent with the measured contact surface in terms of morphology, structure, and statistical characteristics, thereby significantly improving the scientificity, reliability, and engineering feasibility of pile side friction calculation.

[0173] like Figure 9As shown, the black data points represent the pile side friction curves obtained using randomly generated contact surface parameters obtained through the comprehensive discrimination method described in this example, while the blue data points represent the pile side friction curves obtained without using the comprehensive discrimination method described in this example. It can be seen that the distribution of the black data points is relatively concentrated and has a good fit with the curve obtained by the empirical parameter method, indicating that the randomly generated contact surface parameters using the comprehensive discrimination method described in this example are consistent with the distribution of contact surface parameters measured by laser scanning. The distribution of the blue data points is very scattered and deviates significantly from the red curve, indicating that the randomly generated contact surface parameters without using the comprehensive discrimination method described in this example differ greatly from the actual contact surface, resulting in a large difference between the obtained pile side friction curve and the actual value, and a poor characterization effect.

[0174] Depending on the actual needs of the project, the dimensions of the horizontal boreholes corresponding to the rock-socketed piles vary, ranging from 0.6 to 1.5 meters in diameter and 10 to 25 meters in length, with some even larger-scale boreholes. Existing laser scanners are handheld or portable and can enter the borehole to scan the inner wall. However, given the large borehole size, manually using a handheld laser scanner to inspect the inner wall is impractical and prone to significant errors.

[0175] This embodiment also provides a support device for laser scanning borehole walls, such as... Figures 10-11 As shown, the device includes a fixed frame, a rotatable guide rail 5, a driving part 6, and several support parts 7. The fixed frame includes a circular bracket 8, four telescopic support rods 9, and a positioning part 10. The fixed frame is installed at the opening end of the borehole. The circular bracket 8 is perpendicular to the central axis of the borehole, and the positioning part 10 is located at the center of the circular bracket 8. The four support rods 9 are evenly distributed along the circumference of the circular bracket 8. The head of the support rod 9 is connected to the positioning part 10, and the tail of the support rod 9 is used to connect with the inner wall of the borehole to support the fixed frame.

[0176] The two ends of the guide rail rod 5 are rotatably connected to the positioning part 10 and the driving part 6, respectively. The support parts are evenly arranged along the length of the guide rail rod 5. Several laser scanners 11 are slidably connected on the guide rail rod 5. The driving part 6 can drive the tail end of the guide rail rod 5 to extend into the borehole. The support part 7 is used to support the guide rail rod 5. A laser scanner 11 is arranged between two adjacent support parts.

[0177] Optionally, the diameter of the circular bracket 8 is reasonably set according to the borehole diameter, and the outer diameter of the circular bracket 8 is preferably 3-10cm smaller than the inner diameter of the borehole; two adjacent support rods 9 form a 90° angle, and a fixing rod 12 is sleeved on the outside of each support rod 9. The fixing rod 12 is hollow inside, the head of the fixing rod 12 is fixedly connected to the outer side of the positioning part 10, and the tail of the fixing rod 12 passes through the circular bracket 8 to fix the position of the positioning part 10 and the support rod 9.

[0178] Further optionally, the support rod 9 passes through the corresponding fixed rod 12, and the tail of the support rod 9 is provided with a telescopic part, which includes a spring 13 and a connector 14. The two ends of the spring 13 are respectively connected to the tail of the support rod 9 and the connector 14. The spring 13 is a hard spring 13, so that the connector 14 can extend and retract appropriately to make close contact with the borehole wall.

[0179] Spring 13 is located inside the tail of fixed rod 12, providing a track for the extension and retraction of spring 13, so that connector 14 always extends and retracts along the direction of fixed rod 12 (i.e., the radial direction of circular bracket 8).

[0180] Optionally, the positioning part 10 is disc-shaped, with the side facing the inside of the drill hole as the front side and the side facing the outside of the drill hole as the back side. The center of the front side of the positioning part 10 is provided with a recessed locking position for rotating the head of the guide rail. The back side of the positioning part 10 is connected to a drive motor and an angle controller for driving the guide rail to rotate at the required specific angle.

[0181] When in use, first grind around the opening of the drill hole to make it relatively flat and form a relatively regular circle, which makes it easy to place the circular bracket 8. The circular bracket 8 and the drill hole should be placed as concentrically as possible. The four mating joints 14 abut against the ground drill hole opening to stabilize and fix the bracket. The center of the positioning part 10 is basically at the center of the drill hole.

[0182] Optionally, the driving part 6 is equipped with a positioning device. The driving part 6 is a self-driving device. Under the guidance of the positioning device, the driving part 6 can travel in a direction parallel to the center axis of the borehole to the inside or outside of the borehole.

[0183] The top of the driving part 6 is provided with a first lifting device 15, and the top of the first lifting device 15 is rotatably connected to the tail of the guide rail rod 5 for adjusting the height of the tail of the guide rail rod 5.

[0184] The positioning device is a commonly used positioning device in the field of oil and gas or coal gas drilling. It can guide the drill bit to drill underground in a preset direction. In this invention, the positioning device guides the driving part 6 to reach the deepest point of the borehole in a predetermined direction.

[0185] Optionally, the support is provided with wheels at the bottom and a second lifting device 16 at the top. The top of the second lifting device 16 is rotatably connected to a guide rail 5 for adjusting the height of the corresponding guide rail 5.

[0186] Optionally, the guide rail 5 is composed of several segments connected end to end, and the guide rail 5 is provided with a guide rail groove, and the laser scanner is slidably connected to the guide rail groove; a laser scanner is provided between the positioning part 10 and the first support part, and a laser scanner is provided between the last support part and the driving part 6.

[0187] Several sensors 17 are provided on the guide rail rod 5. The sensors 17 and the laser scanner 11 are located on opposite sides of the guide rail rod 5. The sensors are used to measure the vertical distance from the bottom of the guide rail rod 5 to the bottom of the borehole, so that the height of the guide rail rod 5 can be adjusted by the first lifting device 15 or the second lifting device, so that the entire guide rail rod 5 is on the same horizontal line.

[0188] In one specific implementation, a sensor is installed at the position of the guide rail rod 5 adjacent to the positioning part 10, a sensor is installed at the positions of the front and rear sides of the support part of the guide rail rod 5, and a sensor is installed at the position of the guide rail rod 5 adjacent to the driving part 6. A limiting part is provided at the tail of the guide rail rod 5 to prevent the tail of the guide rail rod 5 from detaching from the first lifting device 15. Limiting parts are also provided at the positions of the guide rail rod 5 corresponding to each support part. The sensors can be infrared height sensors. The positioning device, driving part 6, all sensors, drive motor, angle controller and laser scanner are all communicatively connected or wired to the control device outside the borehole, which can control the travel direction and speed of the driving part 6; control the lifting height of each lifting device through the data transmitted by the sensors; control the rotation angle of the guide rail rod 5 to adjust the angle position of the laser scanner scanning the inner wall of the borehole; control the movement of each laser scanner on the corresponding segment to perform a comprehensive scan of the inner wall of the borehole.

Claims

1. A quantitative characterization method for the pile-rock interface friction of a rock-socketed pile, characterized in that, include: S1: Along the circumference of the circular cross-section of the rock-socketed pile, take several marking points on the circumference of the cross-section; S2: Select side lines on the side of the rock-socketed pile, and mark the points one by one with the side lines; the side lines are uneven curves; construct the geometric outline of the pile-rock interface based on the side lines corresponding to the mark points. S3: Divide the side line into several micro-segments, with the length of each micro-segment being λ along the pile length direction. i Along the pile diameter direction, the height of the micro-segment is h. i ; S4: Perform laser scanning on the borehole in the rock wall to obtain the actual contour of the borehole wall and determine λ. i with h i The distribution pattern, randomly generated λ i with h i The data values ​​are used to determine the pile side friction resistance.

2. The quantitative characterization method according to claim 1, characterized in that, The rock-socketed pile is cylindrical, with its cross-section parallel to the pile diameter direction and the pile diameter direction perpendicular to the pile length direction. The top and bottom surfaces of the rock-socketed pile are parallel to the pile diameter direction. The intersection of the side line and the top surface of the rock-socketed pile is the vertex of the side line, and the intersection of the side line and the bottom surface of the rock-socketed pile is the bottom point of the side line. The line connecting the vertex and the bottom point of the side line is the side reference line, which is parallel to the pile length direction.

3. The quantitative characterization method according to claim 2, characterized in that, The borehole wall of the rock is uneven. Concrete is poured into the borehole and solidifies to form a rock-embedded pile. Therefore, the side of the rock-embedded pile is also uneven. The side line is a line on the pile-rock contact surface. The side line is an uneven curve and extends along both the pile length and pile diameter directions.

4. The quantitative characterization method according to claim 2, characterized in that, In step S1, the marked point is connected to the center of the corresponding cross-section to form the marked radius, and the angle between the marked radius and the radial vector of the cross-section is θ.

5. The quantitative characterization method according to claim 4, characterized in that, In step S3, the length λ of the micro-segment is along the length direction of the side baseline. i The length of the projection of the micro-segment onto the side baseline; the height h of the micro-segment along the length direction of the mark radius. i Let be the perpendicular distance between the point on the micro-segment furthest from the side baseline and the side baseline.

6. The quantitative characterization method according to claim 2, characterized in that, In step S4, based on the actual contour of the borehole wall, the values ​​of θ corresponding to the marker points at different positions on the circumference of the rock-socketed pile cross-section are determined.

7. The quantitative characterization method according to claim 5, characterized in that, In step S4, the pile-rock contact surface friction resistance of any micro-segment i of any side line is determined by the following formula: ； Where, τ i σ is the pile-rock contact surface skin friction, kPa; n0 ρ is the initial value of the normal stress at the pile-rock contact surface, kPa; K is the normal stiffness of the pile-rock contact surface, kPa / mm; s i λ represents the pile-rock relative displacement, in mm; i h is the length of the micro-segment, in mm. i The height of the micro-segment is in mm; b The basic friction angle of the pile-rock contact surface is given in degrees.

8. The quantitative characterization method according to claim 7, characterized in that, The normal stiffness K of the pile-rock contact surface is determined by the following formula: ； Among them, E r R is the elastic modulus of the rock, MPa; μ is the Poisson's ratio of the rock, dimensionless; r p denoted as the cross-sectional radius of the rock-socketed pile, in mm.

9. The quantitative characterization method according to claim 7, characterized in that, When the pile-rock interface fails, the pile-rock contact surface friction is represented by the residual pile-rock contact surface friction, τ. i 'Determined by the following formula:' ； Where, τ i 'Residual pile side friction, kPa; s r Residual pile-rock relative displacement, mm; r The residual friction angle at the pile-rock contact surface is expressed in degrees.

10. The quantitative characterization method according to claim 1, characterized in that, In step S4, the laser scanning is performed using the following support device, which includes a fixed frame, a rotatable guide rail, a driving part, and several support parts. The fixed frame includes a circular bracket, four telescopic support rods, and a positioning part. The fixed frame is installed at the opening end of the borehole. The circular bracket is perpendicular to the central axis of the borehole, and the positioning part is located at the center of the circular bracket. The four support rods are evenly distributed along the circumference of the circular bracket. The head of the support rod is connected to the positioning part, and the tail of the support rod is used to connect with the inner wall of the borehole to support the fixed frame. The guide rail rod has a positioning part and a driving part rotatably connected at both ends, and the support parts are evenly arranged along the length of the guide rail rod. Several laser scanners are slidably connected on the guide rail rod. The driving part can drive the tail end of the guide rail rod to extend into the borehole. The support parts are used to support the guide rail rod. A laser scanner is set between two adjacent support parts.

Images