Peak friction angle calculation method and system based on static sounding experiment

Abstract

The invention relates to the field of peak friction angle calculation, in particular to a peak friction angle calculation method and system based on a static sounding experiment. The method comprises the steps that a static sounding experiment is conducted on a seabed, and the conical tip resistance, the side friction resistance, the seabed penetration depth, the seawater unit weight and the seawater depth of a seabed soil body are obtained; the conical tip resistance is corrected through the seawater depth, the seabed penetration depth and the seawater unit weight, and corrected conical tip resistance is obtained; calculating the friction resistance ratio of the opposite sides of the seabed soil body by using the corrected conical tip resistance and the side friction resistance; determining the soil layer type of the seabed soil body by utilizing the friction resistance ratio of the opposite sides and the corrected conical tip resistance; and calculating a peak friction angle estimated value based on the soil layer type. According to the method, the problem that the calculation of the peak friction angle is not accurate and scientific enough due to complex and changeable environments for estimating the peak friction angle in the prior art is solved, and the accuracy and scientificity of estimating the peak friction angle are greatly improved.

Description

Technical Field

[0001] The present invention relates to the field of peak friction angle calculation, and specifically to a method and system for calculating the peak friction angle based on a static cone penetration test. Background Art

[0002] The strength index of soil, especially the effective peak friction angle, is an important parameter for evaluating the stability and bearing capacity of soil, and is widely used in fields such as ocean engineering, foundation design, and slope stability analysis. In engineering practice, it is often indirectly estimated through in-situ test data, among which the static cone penetration test (CPT for short) is one of the mainstream methods. This method has the advantages of high test efficiency, strong continuity, and non-disturbance of soil samples, and is especially suitable for the preliminary acquisition of strength parameters of soft clay or marine sedimentary layers.

[0003] However, the traditional method for estimating the peak friction angle has quite a lot of uncertainties. Among them, the inaccurate definition of soil layer types has the greatest impact on the estimation of the peak friction angle, because different soil layer types adopt different calculation methods, and the same calculation method results in changes in estimation accuracy due to complex environmental changes, so that the estimation of the peak friction angle remains a huge problem today.

[0004] Common technical means in the prior art, such as the inverse calculation method: some studies input the measured CPT data into a finite element or finite difference model, and optimize the soil strength index through inverse calculation. However, this method requires building a complex model, relying on a large number of input parameters (such as elastic modulus, stress path, drainage conditions, etc.), and requires iterative calculations, making it difficult to apply to the scenario of rapid engineering judgment. The combined algorithm of atlas discrimination and rule reasoning: In recent years, some methods have introduced machine learning or Bayesian models, using CPT parameters as inputs to output soil property indexes or strength ranges. Although the degree of automation has been improved, the model has strong "black box" characteristics and high dependence on training samples, making it difficult to ensure cross-regional universality and engineering interpretability. Therefore, there is an urgent need for a more intelligent and accurate method for calculating the peak friction angle in the prior art. Summary of the Invention

[0005] Aiming at the defects in the prior art, the present invention provides a method and system for calculating the peak friction angle based on a static cone penetration test, which solves the problem that the calculation of the peak friction angle in the prior art is not accurate and scientific enough.

[0006] To achieve the above object, an aspect of the present invention provides a method for calculating the peak friction angle based on a static cone penetration test, including: conducting a static cone penetration test on the seabed to obtain the cone tip resistance, side friction resistance, penetration depth into the seabed, unit weight of seawater, and seawater depth of the seabed soil; correcting the cone tip resistance by using the seawater depth, the penetration depth into the seabed, and the unit weight of seawater to obtain a corrected cone tip resistance; calculating the relative side friction ratio of the seabed soil by using the corrected cone tip resistance and the side friction resistance; determining the soil layer type of the seabed soil by using the relative side friction ratio and the corrected cone tip resistance; and calculating an estimated value of the peak friction angle based on the soil layer type.

[0007] The present invention first obtains basic data such as cone tip resistance and side friction resistance through static cone penetration, relies on seawater depth, penetration depth, and seawater specific weight to correct the cone tip resistance, eliminates the interference of the seawater environment on mechanical parameters, improves the accuracy of parameters, then calculates the relative side friction ratio by using the corrected cone tip resistance and side friction resistance, constructs a basis for soil type determination in combination with the corrected cone tip resistance, breaks through the bottleneck of difficult soil type definition under complex conditions such as the seabed transition layer and disturbed layer, and calculates the estimated value of the peak friction angle based on the determined soil layer type, improving the accuracy and scientificity of peak friction angle calculation.

[0008] Optionally, the soil layer type includes clay, silt, and sand, and the clay satisfies and , the silt satisfies and , the sand satisfies and , where is the corrected cone tip resistance, is the relative side friction ratio.

[0009] The present invention accurately defines three types of soil layers, namely clay, silt, and sand, by clarifying the threshold ranges of the corrected cone tip resistance and the relative side friction ratio. This quantitative standard provides a clear and operable determination basis for soil type identification in complex seabed strata, solves the problem of difficult soil type definition in the transition layer and disturbed layer, and further improves the scientificity and accuracy of soil layer type determination.

[0010] Optionally, the calculating the estimated value of the peak friction angle based on the soil layer type includes: setting a first weight set based on the soil layer type; calculating the peak friction angle of the seabed soil by using multiple methods to obtain multiple peak friction angle values; and performing weighted summation on the peak friction angle values by using the first weight set to obtain the estimated value of the peak friction angle.

[0011] The present invention calculates multiple peak friction angle values through multiple methods, covering different theoretical perspectives, and then performs weighted summation using a weight set. This not only avoids the limitations of a single calculation method but also, due to the adaptation to soil layer types, makes the weight distribution conform to the true mechanical mechanism of the soil mass, greatly improving the accuracy of the estimated peak friction angle value.

[0012] Optionally, the calculating multiple peak friction angle values of the seabed soil mass by using multiple methods includes: calculating a first estimated peak friction angle value by using the normalized corrected cone tip resistance; obtaining an estimated relative density value of the seabed soil mass based on the static cone penetration test, and calculating a second estimated peak friction angle value by using the estimated relative density value; obtaining the vertical effective stress of the seabed soil mass based on the static cone penetration test, and calculating a third estimated peak friction angle value by using the vertical effective stress and the corrected cone tip resistance.

[0013] The present invention calculates the first estimated peak friction angle value by using the normalized corrected cone tip resistance, explores the value of the mechanical signal at the cone tip, calculates the second estimated peak friction angle value by using the relative density, correlates with the structural characteristics, and calculates the third estimated peak friction angle value based on the vertical effective stress and the corrected cone tip resistance, incorporating the stress environment. The multiple methods cover different mechanical, structural, and stress factors, complementing and verifying each other, and improving the accuracy and scientific nature of the estimated peak friction angle value.

[0014] Optionally, the obtaining an estimated relative density value of the seabed soil mass based on the static cone penetration test includes: setting a second weight set based on the soil layer type; calculating multiple relative density values of the seabed soil mass by using multiple methods based on the static cone penetration test; and performing weighted summation on the relative density values by using the second weight set to obtain an estimated relative density value.

[0015] Multiple relative density values are calculated through multiple methods, covering different calculation logics, and then weighted summation is performed using a weight set. This not only overcomes the adaptation defects of a single method but also, due to the targeted weight distribution according to the soil layer type, makes the result conform to the true density state of the soil mass, improving the accuracy of the estimated relative density value.

[0016] Optionally, the calculating multiple relative density values of the seabed soil mass by using multiple methods based on the static cone penetration test includes: performing normalization processing on the corrected cone tip resistance to obtain a normalized corrected cone tip resistance; calculating a first relative density value by using the normalized corrected cone tip resistance; obtaining the overconsolidation ratio of the seabed soil mass according to the static cone penetration test, and calculating a second relative density value according to the overconsolidation ratio and the normalized corrected cone tip resistance; and calculating a third relative density value by using the cone tip resistance and the vertical effective stress.

[0017] In the present invention, the cone tip resistance is first normalized and corrected to calculate the first relative density value, focusing on the core mechanical parameters. The second relative density value is calculated by combining the overconsolidation ratio and the normalized cone tip resistance, incorporating the stress history dimension. Then, the third relative density value is calculated using the cone tip resistance and the vertical effective stress, strengthening the stress-density correlation. Multiple methods cover different influencing factors, verifying and complementing each other, breaking through the limitations of a single method, and improving the accuracy and scientific nature of the relative density value.

[0018] Optionally, the overconsolidation ratio of the seabed soil obtained according to the static cone penetration test includes: calculating the unit weight of the seabed soil using the side friction resistance; calculating the total stress at the measuring point of the seabed soil based on the unit weight of the soil and the penetration depth into the seabed; estimating the maximum past effective consolidation stress by combining the soil layer type, the total stress at the measuring point, and the corrected cone tip resistance; calculating the overconsolidation ratio of the seabed soil using the maximum past effective consolidation stress and the vertical effective stress.

[0019] In the present invention, the unit weight of the soil is calculated through the side friction resistance, the total stress at the measuring point is obtained by combining the penetration depth, and then the maximum historical effective consolidation stress is estimated by integrating the soil layer type, the total stress, and the corrected cone tip resistance. Finally, the overconsolidation ratio is obtained by combining with the vertical effective stress. Analyzing from multiple dimensions such as soil self-weight and stress history, correlating the side friction resistance with the physical properties of the soil, reflecting the double-layer load effect of the seabed with the total stress, and adapting to the stress response differences of different soil types by the soil layer type, the calculation of the overconsolidation ratio takes into account the in-situ test data and the historical stress state of the soil, improving the accuracy of the overconsolidation ratio calculation.

[0020] Optionally, the vertical effective stress of the seabed soil obtained based on the static cone penetration test includes: calculating the pore water pressure of the seabed soil using the seawater depth, the penetration depth into the seabed, and the unit weight of the seawater; calculating the vertical effective stress of the seabed soil using the pore water pressure and the total stress at the measuring point.

[0021] The pore water pressure is accurately calculated through the seawater depth, the penetration depth, and the unit weight of the seawater, and the vertical effective stress is obtained by combining the total stress at the measuring point. Following the principle of hydrostatic pressure, the interference of the seawater load is eliminated, the influence of the pore water pressure is stripped, and the effective stress borne by the soil skeleton is highlighted, ensuring that the mechanical analysis of the seabed soil is close to the true stress state and improving the accuracy of the total stress at the measuring point.

[0022] Optionally, the calculation of the total stress at the measuring point of the seabed soil based on the unit weight of the soil and the penetration depth into the seabed includes: calculating the soil stress at the measuring point of the seabed soil using the unit weight of the seawater and the seawater depth; calculating the water stress at the measuring point of the seabed soil using the unit weight of the soil and the penetration depth into the seabed; calculating the total stress at the measuring point of the seabed soil according to the soil stress at the measuring point and the water stress at the measuring point.

[0023] The present invention calculates the soil stress at the measurement point by the unit weight of seawater and the seawater depth, and calculates the water stress at the measurement point by the unit weight of soil and the penetration depth. Then, the sum is obtained as the total stress, quantifying the double-layer load effect of seawater ballast and soil self-weight, following the superposition principle of hydrostatic pressure and self-weight stress, stripping the interference of pore water pressure, accurately reflecting the actual stress state of the seabed soil, and improving the accuracy of the total stress at the measurement point.

[0024] In another aspect of the present invention, there is also provided a peak friction angle calculation system based on a static cone penetration test, including: a processor, an input device, an output device, and a memory. The processor, the input device, the output device, and the memory are interconnected. Among them, the memory is used to store a computer program, and the computer program includes program instructions. The processor is configured to call the program instructions to execute a peak friction angle calculation method according to any one of the previous aspects of the present invention.

[0025] The peak friction angle calculation system based on a static cone penetration test of the present invention has a compact structure, stable performance, high integration, and simple composition, and can stably execute a peak friction angle calculation method provided in the previous aspect of the present invention, further improving the overall applicability and practical application ability of the present invention. Description of the Drawings

[0026] Figure 1 It is a flowchart of a peak friction angle calculation method based on a static cone penetration test according to an embodiment of the present invention; Figure 2 It is a schematic structural diagram of a peak friction angle calculation system based on a static cone penetration test according to an embodiment of the present invention. Detailed Embodiments

[0027] Specific embodiments of the present invention will be described in detail below. It should be noted that the embodiments described here are only for illustrative purposes and do not limit the present invention. In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to those of ordinary skill in the art that: it is not necessary to employ these specific details to practice the present invention. In other instances, well-known circuits, software, or methods have not been specifically described to avoid obscuring the present invention.

[0028] Throughout the specification, references to "one embodiment", "an embodiment", "one example" or "an example" mean that a particular feature, structure, or characteristic described in connection with the embodiment or example is included in at least one embodiment of the present invention. Thus, the phrases "in one embodiment", "in an embodiment", "one example" or "an example" appearing throughout the specification do not necessarily all refer to the same embodiment or example. Additionally, the particular features, structures, or characteristics may be combined in any suitable combination and / or sub-combination in one or more embodiments or examples. Further, those of ordinary skill in the art should understand that the diagrams provided herein are for illustrative purposes only and are not necessarily drawn to scale.

[0029] Please refer to Figure 1 , in an alternative embodiment, to address the deficiencies in the prior art, such as Figure 1 A method for calculating the peak friction angle based on a static cone penetration test, as shown in Step S1: Conduct a static cone penetration test on the seabed to obtain the cone tip resistance, side friction resistance, penetration depth into the seabed, unit weight of seawater, and seawater depth of the seabed soil.

[0030] In this embodiment, the static cone penetration test (abbreviated as CPT) is an in-situ testing technique that uses a mechanical or hydraulic device to drive a cone penetrometer with sensors into the soil at a constant rate and simultaneously collect parameters such as the tip resistance, pore water pressure, and side friction resistance. This test can synchronously record the seawater depth and penetration depth into the seabed, and the data is usually presented as a curve that varies with the penetration depth. It has the advantages of high test efficiency, strong continuity, and non-disturbance of soil samples, and is particularly suitable for obtaining the mechanical parameters of soft clay or marine sedimentary layers.

[0031] When conducting a static cone penetration test on the seabed, a cone penetrometer equipped with a pressure sensor is driven into the seabed soil at a constant rate through an underwater detection device, and the cone tip resistance is collected in real-time using the resistance strain sensor at the front end of the penetrometer , and the side friction resistance is synchronously obtained through the sidewall friction cylinder sensor .

[0032] The penetration depth into the seabed is recorded by linking a depth encoder with a GPS positioning system and the seawater depth .

[0033] The unit weight of seawater is calculated by measuring the seawater temperature and salinity on-site and combining with the international seawater equation of state (or directly using the standard value of 1025 kg / m³). All data is transmitted to the deck data acquisition system through a waterproof cable and stored in real-time at a frequency of 10 Hz to form a depth-parameter curve.

[0034] Step S2: Correct the tip resistance using the seawater depth, the penetration depth into the seabed, and the unit weight of seawater to obtain the corrected tip resistance.

[0035] The corrected tip resistance satisfies the following formula: , where, is the corrected tip resistance, is the tip resistance obtained from the static cone penetration test, is the tip area ratio, is the unit weight of seawater, is the seawater depth, is the penetration depth into the seabed.

[0036] In the above formula, the tip area ratio , reflecting the actual influence of pore pressure on the tip area, usually takes an empirical value of 0.8.

[0037] In the seabed environment, the seawater and the seabed soil body form a pressure field. The permeable area of the tip (with a proportion of , because is the tip area ratio) will generate pressure due to the combined total water depth of the unit weight of seawater , the seawater depth and the penetration depth into the seabed , offsetting part of the measured tip resistance . The formula calculates the action amount of this pressure on the permeable area and adds it back to to eliminate the interference of seawater pressure and make more accurately reflect the resistance of the seabed soil body itself to the penetration of the tip.

[0038] Step S3: Calculate the relative side friction ratio of the seabed soil body using the corrected tip resistance and the side friction resistance.

[0039] The relative side friction ratio satisfies the following formula: , where, is the relative side friction ratio, is the side friction resistance, is the corrected tip resistance.

[0040] In this embodiment, the core of the above formula lies in quantifying the contribution ratio of the friction resistance of the soil body sidewall to the probe and the corrected resistance of the soil body end to the probe during the tip penetration process by comparing their relative strengths.

[0041] Step S4: Determine the soil layer type of the seabed soil body using the relative side friction ratio and the corrected tip resistance.

[0042] The soil layer types include clay, silt and sand, and the clay satisfies and , the silt satisfies and , and the sand satisfies and , where is the corrected cone tip resistance, and is the relative side friction ratio.

[0043] The corrected cone tip resistance reflects the resistance ability of the soil during the local penetration of the cone tip and is an important index characterizing the overall strength and density of the soil. Generally, due to the strong skeleton support force, sand has a higher peak compressive strength, so is usually much higher than that of silt and clay; while clay has a loose structure, poor drainage conditions and limited bearing capacity, has a relatively low value. [[ID=2,7]]

[0044] The relative side friction ratio reflects the ratio between the shear resistance ability and the main compressive strength of the soil during the shear process of the cone rod and is an important index indirectly reflecting the proportion of the friction characteristics and cohesion of the soil. Due to its significant cohesion and flow characteristics during shear, clay shows a relatively high friction ratio, has a relatively high value; while the friction contribution of sand during shear is relatively low, has a small value.

[0045] Therefore, when considering and jointly, the comprehensive mechanical behavior of different types of soil can be effectively distinguished. For example, "low + high " usually indicates clay; "medium + medium " indicates silt; while "high + low " typically represents sand. Based on this characteristic difference, the present invention constructs three types of interval division rules to achieve automatic identification of soil layer types and precise matching of weight paths.

[0046] Step S5, calculate the estimated value of the peak friction angle based on the soil layer type.

[0047] Among them, calculating the estimated value of the peak friction angle based on the soil layer type specifically includes the following sub-steps: Step S51, set the first weight set based on the soil layer type.

[0048] The first weight satisfies the following formula: , Among them, is the first weight set, is the soil layer type, is clay, is silt, is sand.

[0049] The strength-dominant mechanisms of different soil types (clay NT, silt FT, sand ST) are significantly different. The strength of clay is centered around cohesion, and the effects of the side friction ratio and consolidation history on the friction angle are more prominent. Silt is in a clay-sand transition state, and the coupling effect of density and cohesion is more crucial; the strength of sand completely depends on particle friction and interlock, and density is the core control factor. By comparing the prediction errors of different calculation models (such as the tip resistance model, side friction model, density model) for the peak friction angles of each soil type, the optimal weight distribution is obtained through regression: for clay, the side friction correlation model is emphasized (the third weight is 0.8); for silt, the density correlation model is strengthened (the third weight is 0.9); for sand, the tip resistance-density model is highlighted (the second weight is 0.8). This soil-type-driven weight design makes the multi-model fusion result more consistent with the true mechanical properties and compensates for the universality defect of a single model.

[0050] Step S52: Calculate the peak friction angles of the seabed soil by multiple methods to obtain multiple peak friction angle values.

[0051] Among them, calculating the peak friction angles of the seabed soil by multiple methods to obtain multiple peak friction angle values specifically includes the following sub-steps: Step S521: Normalize the modified tip resistance to obtain the normalized modified tip resistance.

[0052]

[0053] Among them, is the normalized modified tip resistance, is the modified tip resistance, is the atmospheric pressure, is the value of the vertical effective stress.

[0054] The above formula takes the atmospheric pressure as the reference dimension. The numerator converts the modified tip resistance into multiples of the atmospheric pressure to unify the stress magnitude. The denominator is the square root ratio of the vertical effective stress relative to the atmospheric pressure, representing the strength of the current stress environment. By dividing the pressure-normalized value of the modified tip resistance by the square root of the pressure normalization of the stress environment, the finally obtained normalized modified tip resistance , which essentially corrects the normalization result of the cone tip resistance to the effective stress - atmospheric pressure coupling field. It not only strips off the effective stress differences brought about by seabed depth and seawater weight but also retains the intrinsic strength information such as the soil's own density and particle interlocking, enabling the corrected cone tip resistances at different seabed positions and depths to be compared in a unified stress - strength dimension.

[0055] Simplifying and transforming the above formula gives:

[0056] Step S522: Calculate the estimated value of the first peak friction angle using the normalized corrected cone tip resistance.

[0057] In an alternative embodiment, the estimated value of the first peak friction angle satisfies the following formula: , where is the estimated value of the first peak friction angle, is the normalized corrected cone tip resistance.

[0058] The above formula has eliminated the interference of external stress fields such as atmospheric pressure and effective stress through the normalized corrected cone tip resistance and only focuses on the intrinsic properties of the soil itself, such as density and particle interlocking. The logarithmic function not only compresses the wide - range variation (with a span of over 10,000 times from 0.1 to 1000) but also conforms to the law of diminishing marginal contribution of density increase to the friction angle (e.g., for every 10 - fold increase, the friction angle increases by approximately 11°). The reference value of 17.6 defines the reference friction angle at, corresponding to extremely loose marine sedimentary soil. The coefficient 11 is obtained from the regression of seabed sounding data, ultimately achieving a rapid conversion from in - situ test parameters to the estimated value of the peak friction angle.

[0059] Step S523: Based on the static cone penetration test, obtain the estimated value of the relative density of the seabed soil, and calculate the estimated value of the second peak friction angle using the estimated value of the relative density.

[0060] The estimated value of the second peak friction angle satisfies the following formula: , where is the estimated value of the second peak friction angle, is the estimated value of the relative density.

[0061] The above formula uses 28° as the reference value (corresponding to the extremely loose state with a relative density of , such as the fluid - plastic marine silt), and quantifies the contribution intensity of density to the friction angle through the coefficient 12.5, that is For every 1% increase, the friction angle linearly increases by 0.125. The physical essence of this relationship is: the relative density directly reflects the degree of compaction of soil particles ( the higher it is, the stronger the particle biting and embedding effects, and the greater the frictional resistance during shear), and the formula converts the strength gain dominated by density into the friction angle increment in a linear superposition form. The coefficient and reference value are from the statistical regression of seabed deposits, realizing a rapid conversion from the density estimated value to the friction angle.

[0062] Among them, the specific steps for obtaining the estimated value of the relative density of seabed soil based on the static cone penetration test are as follows: Step S5231, set the second weight set based on the soil layer type.

[0063] The second weight set satisfies the following formula: , where is the second weight set, is the soil layer type, is clay, is silt, is sand.

[0064] Based on the differences in the strength-dominant mechanisms of clay NT, silt FT, and sand ST, the above formula is statistically optimized through in-situ seabed tests and laboratory tests. The strength of clay is centered on cohesion, and the side friction resistance contributes more prominently to the friction angle. Therefore, the side friction resistance correlation model is given the highest proportion. Silt belongs to the clay-sand transition state, and the coupling effect of density and cohesion is crucial. Weaken the pure cohesion model and strengthen the density-cohesion coupling model. The strength of sand depends on particle friction, and the density reflected by the normalized tip resistance is the core. Let the density-friction model dominate, and drive the model weight adaptation through soil type characteristics to make up for the universality defect of a single model.

[0065] Step S5232, calculate the relative density of the seabed soil using multiple methods based on the static cone penetration test to obtain multiple relative density values.

[0066] Among them, calculating the relative density of the seabed soil using multiple methods based on the static cone penetration test to obtain multiple relative density values includes: Step S52321, calculate the first relative density value using the normalized corrected tip resistance.

[0067] , where is the first relative density value, is the normalized corrected tip resistance.

[0068] The above formula is based on the statistical regression of a large number of in-situ static cone penetration test and measured density data, and uses the normalized corrected cone tip resistance , through logarithmic transformation to adapt to the non-linear relationship between the cone tip resistance and the density. The principle is that when the soil density increases, the particle interlocking effect increases exponentially, and the cone tip resistance increases exponentially synchronously. The logarithm can linearize it. The coefficient 68 quantifies the contribution intensity of the logarithmic change of the normalized corrected cone tip resistance to the density, and subtracting 1 is the intercept correction, corresponding to the extremely loose reference state where the first relative density value is 0 when the normalized corrected cone tip resistance is equal to 10. Finally, an efficient conversion from in-situ penetration parameters to relative density is achieved.

[0069] Step S52322, obtain the overconsolidation ratio of the seabed soil according to the static cone penetration test, and calculate the second relative density value according to the overconsolidation ratio and the normalized corrected cone tip resistance.

[0070] The second relative density value satisfies the following formula: , where, is the second relative density value, is the normalized corrected cone tip resistance, is the overconsolidation ratio.

[0071] The above formula corrects the structural interference of overconsolidation by integrating the intrinsic density of the soil and the stress history. The normalized corrected cone tip resistance characterizes the intrinsic density basis of soil particle interlocking, while the overconsolidation ratio (the overconsolidated soil forms a dense structure due to historical high stress) will make the normalized corrected cone tip resistance doped with false density signals of structural strengthening. The formula attenuates the structural contribution in the denominator (the larger the overconsolidation ratio, the stronger the stripping), linearizes the exponential relationship between the cone tip resistance and the density with the square root, and the empirical coefficient 305 is derived from seabed test statistics. Finally, the density signal free of structural interference is converted into the relative density percentage .

[0072] Among them, the steps to obtain the overconsolidation ratio of the seabed soil according to the static cone penetration test include the following: Step S523221, calculate the unit weight of the seabed soil using the side friction resistance.

[0073] The unit weight of the soil satisfies the following formula: , where, is the unit weight of the soil, is the side friction resistance.

[0074] The above formula estimates the unit weight of seabed soil through the side friction resistance. Using the positive correlation between the side friction resistance and the soil density, the wide range of changes in the side friction resistance is compressed through logarithmic transformation to adapt to the law of diminishing marginal contribution of density increase to the unit weight. Taking 26 as the upper limit of the density soil unit weight, the reduction range of the loose soil unit weight is adjusted by the coefficient 14 and the square term. Among them, The side friction resistance is converted into a density index, and the square operation of the denominator further smooths the change of the unit weight to ensure that the calculated value of the unit weight of extremely loose soil conforms to the characteristics of marine sedimentary soil. This empirical model is based on the statistical regression of seabed static cone penetration test data and soil weighing test to achieve an efficient conversion from in-situ parameters to physical indexes.

[0075] Step S523222, calculate the total stress at the measuring point of the seabed soil based on the unit weight of the soil and the penetration depth into the seabed.

[0076] Among them, calculating the total stress at the measuring point of the seabed soil based on the unit weight of the soil and the penetration depth into the seabed includes: Step S5232221, calculate the soil stress at the measuring point of the seabed soil using the unit weight of the seawater and the seawater depth.

[0077] The soil stress at the measuring point satisfies the following formula: , Among them, is the soil stress at the measuring point, is the unit weight of the seawater, is the seawater depth.

[0078] The above formula quantifies the ballast effect of the seawater weight on the seabed surface. The unit weight of the seawater is multiplied by the water depth to calculate the hydrostatic pressure generated by the weight of the seawater column at the measuring point on the seabed surface. This pressure is directly used as the initial normal stress of the soil, reflecting the stress contribution of the seawater load to the seabed soil, and is the basic boundary condition for subsequent analysis of the effective stress and strength characteristics of the soil. Essentially, it is the direct application of the hydrostatic pressure formula in the calculation of the seabed surface stress field.

[0079] Step S5232222, calculate the water stress at the measuring point of the seabed soil using the unit weight of the soil and the penetration depth into the seabed.

[0080] , Among them, is the water stress at the measuring point, is the unit weight of the soil, is the penetration depth into the seabed.

[0081] The above formula quantifies the stress contribution of the self-weight of the seabed soil mass at the penetration depth, with the unit weight of the soil mass as the unit weight index, and the penetration depth into the seabed being the thickness of the soil mass above the corresponding calculation point. The two are multiplied to directly calculate the vertical stress formed by the superposition of the self-weight of the soil mass at this depth, serving as the self-weight load basis for analyzing the effective stress and strength characteristics of the seabed soil mass.

[0082] Step S5232223: Calculate the total stress at the measurement point of the seabed soil mass based on the soil stress and the water stress at the measurement point.

[0083] , where is the total stress at the measurement point, is the unit weight of seawater, is the depth of seawater, is the unit weight of the soil mass, is the penetration depth into the seabed.

[0084] The above formula superimposes the self-weight load of the double-layer structure of the seabed, combines the hydrostatic pressure of the seawater column , with the self-weight stress of the seabed soil mass above the penetration depth and directly sums them to obtain the total vertical stress at the measurement point.

[0085] Step S523223: Estimate the maximum past effective consolidation stress in combination with the soil layer type, the total stress at the measurement point, and the corrected cone tip resistance.

[0086] In this embodiment, the maximum past effective consolidation stress refers to the maximum vertical effective stress that the soil sample has experienced during its soil formation or loading history.

[0087] , where is the maximum past effective consolidation stress, is the corrected cone tip resistance, is the total stress at the measurement point, is the atmospheric pressure, and m is a custom index related to the soil layer type.

[0088] When the soil layer type is clay , when the soil layer type is silt , when the soil layer type is sand .

[0089] The above formula combines the difference between the corrected cone tip resistance and the current total stress, and combines the soil layer type parameters (clay 0.72, silt 0.8, sand 0.85) and the atmospheric pressure reference , invert the historical maximum effective consolidation stress of the seabed soil mass, and use to quantify the difference in historical stress contributions of overconsolidated soils, and through adapting to the stress response characteristics of different soil types (sand particles are dominated by friction, so it is larger), and then through atmospheric pressure normalization to eliminate the interference of environmental magnitudes, and finally calibrated to the historical stress estimate value through the empirical coefficient 0.33.

[0090] Step S523224, calculate the overconsolidation ratio of the seabed soil mass using the maximum past effective consolidation stress and the vertical effective stress.

[0091] The overconsolidation ratio satisfies the following formula: , where is the overconsolidation ratio, is the corrected cone tip resistance, is the total stress at the measuring point, is the atmospheric pressure, and m is a custom index related to the soil layer type.

[0092] The overconsolidation ratio, as the ratio of the historical maximum effective consolidation stress of the soil mass to the current effective stress, is a core index reflecting the stress historical state (overconsolidated / normally consolidated / underconsolidated) of the seabed soil mass. Its significance lies in: by quantifying the strengthening effect of historical stress on the soil structure (such as overconsolidated soils forming a dense structure due to past high stresses), providing a benchmark for the mechanical analysis of the difference between the corrected cone tip resistance and the current stress, and then serving as a key input for calculating the relative density, and driving the multi-model weight distribution through the soil type identification mechanism (combining the corrected cone tip resistance and the side friction ratio) (such as different overconsolidation ratio related formula weights for sand and clay), and finally serving the accurate estimation of the peak friction angle, providing a quantitative basis in the stress historical dimension for the analysis of the foundation stability of ocean engineering, the evaluation of the bearing capacity of slopes, etc.

[0093] Step S52323, calculate the third relative density value using the cone tip resistance and the vertical effective stress.

[0094] , where is the third relative density value, is the cone tip resistance value, is the vertical effective stress value.

[0095] The above formula uses the cone tip resistance to reflect the dense characteristics of the soil mass, combines the vertical effective stress to consider the influence of the stress environment, adapts to the non-linear relationship between the cone tip resistance and the density through logarithmic operation, and the coefficients and It is determined by experimental statistical regression that the ratio of the cone tip resistance to the effective stress is converted into the third relative density , realizing the quantitative estimation of the soil compaction state based on the static cone penetration test parameters.

[0096] Step S5233, use the second weight set to perform weighted summation on the relative density values to obtain a relative density estimated value.

[0097] The relative density estimated value satisfies the following formula: , where, is the relative density estimated value, is the normalized corrected cone tip resistance, is the overconsolidation ratio, is the cone tip resistance value, is the vertical effective stress value, is the soil layer type, is clay, is silt, is sand.

[0098] In this embodiment, by fusing multiple relative density calculation models and assigning weights in combination with soil type characteristics, the accurate estimation of the seabed soil compaction degree is realized. In actual engineering, the strength mechanisms of clay, silt, and sand are significantly different (for example, clay depends on cohesion and sand depends on particle friction). After identifying the soil type based on the corrected cone tip resistance and the side friction ratio, different weights are assigned to different calculation methods, which not only avoids the adaptability defects of a single formula for complex strata, but also improves the robustness of the results through weighted fusion. The estimated relative density is closer to the true state of the soil, providing key parameter support for the subsequent calculation of the peak friction angle, and solving the engineering problem of large estimation deviation of traditional single models under complex seabed geological conditions.

[0099] Step S524, based on the static cone penetration test, obtain the vertical effective stress of the seabed soil, and use the vertical effective stress and the corrected cone tip resistance to calculate the third peak friction angle estimated value.

[0100] The third peak friction angle estimated value satisfies the formula: , where, is the third peak friction angle estimated value, is the corrected cone tip resistance, is the vertical effective stress value.

[0101] The above formula is based on the corrected cone tip resistance and the vertical effective stress The ratio is used to linearize the non - linear relationship between the two through logarithmic transformation. Then, in combination with the coefficients 0.1 and 0.38 (determined by statistical regression), the ratio information is converted into the input of the arctangent function, and finally the estimated value of the third peak friction angle is calculated. Quantitative estimation of the third peak friction angle of soil mass based on static cone penetration test parameters is realized.

[0102] Among them, the vertical effective stress of the seabed soil mass obtained based on the static cone penetration test includes: Step S5241: Calculate the pore water pressure of the seabed soil mass by using the seawater depth, the penetration depth into the seabed, and the unit weight of seawater.

[0103]

[0104] Among them, is the pore water pressure, is the unit weight of seawater, is the seawater depth, Penetration depth into the seabed.

[0105] The above formula adds the seawater depth and the penetration depth into the seabed to obtain the total liquid column height of seawater in the pores of the soil corresponding to the seawater and penetration depth. Then, it multiplies by the unit weight of seawater to calculate the pore water pressure formed by seawater at the measuring point of the seabed soil mass, reflecting the hydrostatic pressure principle that the pore water pressure varies linearly with the liquid column height.

[0106] Step S5242: Calculate the vertical effective stress of the seabed soil mass by using the pore water pressure and the total stress at the measuring point.

[0107] The vertical effective stress satisfies the following formula: , Among them, is the vertical effective stress, is the pore water pressure. Substituting the expressions of the above - mentioned vertical effective stress and pore water pressure into the vertical effective stress expression, we get: , Among them, is the unit weight of seawater, is the unit weight of soil mass, Penetration depth into the seabed Step S53: Use the first weight set to perform weighted summation on the peak friction angle values to obtain the estimated value of the peak friction angle.

[0108] The estimated value of the peak friction angle satisfies the following formula: , Among them, is the estimated value of the peak friction angle, is the normalized corrected cone tip resistance, is the estimated value of relative density, is the corrected cone tip resistance, is the value of vertical effective stress, is the soil layer type, is clay, is silt, is sand.

[0109] In this embodiment, by fusing multiple peak friction angle calculation models and assigning weights in combination with soil type characteristics, accurate estimation of the peak friction angle is achieved. The model of the present invention automatically identifies the soil layer types of clay, silt, and sand, assigns different weights to different calculation methods, not only avoids the adaptability defects of a single formula for complex strata, but also weights according to the emphasis on different calculation methods. This makes the estimated value of the peak friction angle more accurate and further solves the engineering problem of large estimation deviation of traditional single models under complex seabed geological conditions.

[0110] As can be seen from the above, the core process of the present invention is a calculation system for the peak friction angle of seabed soil based on the static cone penetration test (CPT), which integrates the full process logic from raw data acquisition to multi-model weighted fusion. Its core value lies in systematically solving engineering problems such as large parameter interference, fuzzy soil type definition, and large deviation of single models in traditional methods through the technical path of correction-identification-fusion.

[0111] First, the cone tip resistance is corrected by seawater depth, penetration depth, and unit weight of seawater to obtain the corrected cone tip resistance that eliminates the interference of seawater pressure, ensuring that the parameter reflects the true resistance of the soil body. Then, the relative side friction ratio is calculated in combination with the side friction resistance, and the soil layer type is accurately identified through the threshold interval of the corrected cone tip resistance and the relative side friction ratio ( and is clay, and is silt, and is sand), breaking through the bottleneck of identifying the seabed transition layer.

[0112] In the stage of calculating the peak friction angle, the system innovatively constructs a dynamic matching mechanism of soil type-weight: sets the first weight set for clay, silt, and sand respectively, and fuses three calculation models - the logarithmic model based on the normalized corrected cone tip resistance, the linear model based on relative density, and the arctangent model based on the ratio of effective stress. Among them, the calculation of relative density also adopts weighted fusion, and the overconsolidation ratio is introduced to eliminate the interference of stress history and make the estimated value of relative density more consistent with the true dense state of the soil body.

[0113] The engineering significance of this method lies in that through the collaborative correction of multiple parameters and the intelligent fusion of multiple models, the complex stress history, structural characteristics and mechanical responses of seabed soil are quantitatively correlated, greatly reducing the error of the estimated value of the peak friction angle compared with the traditional single model, and providing traceable and easily verifiable accurate parameters for the evaluation of the bearing capacity of marine pile foundations and the stability analysis of seawall slopes.

[0114] As Figure 2 shown, on the other hand, the present invention also provides a peak friction angle calculation system based on a static cone penetration test, including: a processor, an input device, an output device and a memory, the processor, the input device, the output device and the memory are interconnected, wherein the memory is used to store a computer program, the computer program includes program instructions, and the processor is configured to call the program instructions to execute the relevant steps of the relevant embodiments in a method for calculating the peak friction angle based on a static cone penetration test according to the present invention.

[0115] For a peak friction angle calculation system based on a static cone penetration test provided by the present invention, each functional component can be integrated in a processing component, or each component can exist physically alone, or two or more components can be integrated in one component. The above integrated components can be implemented in the form of hardware or in the form of software functions.

[0116] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered by the scope of the claims and the description of the present invention.

Claims

1. A method for calculating the peak friction angle based on static cone penetration test The characteristics are that the method includes: Conducting a static cone penetration test on the seabed to obtain the cone tip resistance, side friction resistance, penetration depth into the seabed, unit weight of seawater, and seawater depth of the seabed soil; Using the seawater depth, the penetration depth into the seabed, and the unit weight of seawater to correct the cone tip resistance to obtain the corrected cone tip resistance; Calculating the relative side friction ratio of the seabed soil using the corrected cone tip resistance and the side friction resistance; Determining the soil layer type of the seabed soil using the relative side friction ratio and the corrected cone tip resistance; Calculating the estimated value of the peak friction angle based on the soil layer type includes: Setting a first weight set based on the soil layer type; Calculating the peak friction angle of the seabed soil using multiple methods to obtain multiple peak friction angle values; Using the first weight set to perform weighted summation on the peak friction angle values to obtain the estimated value of the peak friction angle.

2. The peak friction angle calculation method based on the static cone penetration test according to claim 1, wherein the soil layer types include clay, silt and sand, and the clay satisfies and 5, the silt satisfies and , the sand satisfies and , where For correcting the cone tip resistance, is the relative side friction ratio.

3. The peak friction angle calculation method based on the static cone penetration test according to claim 1, characterized in that, The calculating the peak friction angle of the seabed soil using multiple methods to obtain multiple peak friction angle values includes: Normalizing the corrected cone tip resistance to obtain the normalized corrected cone tip resistance; Calculating the first estimated value of the peak friction angle using the normalized corrected cone tip resistance; Obtaining the estimated value of the relative density of the seabed soil based on the static cone penetration test, and calculating the second estimated value of the peak friction angle using the estimated value of the relative density; Obtaining the vertical effective stress of the seabed soil based on the static cone penetration test, and calculating the third estimated value of the peak friction angle using the vertical effective stress and the corrected cone tip resistance.

4. The method for calculating the peak friction angle based on the static cone penetration test according to claim 3, The characteristics are that the obtaining the estimated value of the relative density of the seabed soil based on the static cone penetration test includes: Setting a second weight set based on the soil layer type; Calculating the relative density of the seabed soil using multiple methods based on the static cone penetration test to obtain multiple relative density values; Using the second weight set to perform weighted summation on the relative density values to obtain the estimated value of the relative density.

5. The method for calculating the peak friction angle based on the static cone penetration test according to claim 4, The calculating the relative density of the seabed soil using multiple methods based on the static cone penetration test to obtain multiple relative density values includes: Calculating the first relative density value using the normalized corrected cone tip resistance; Obtaining the overconsolidation ratio of the seabed soil according to the static cone penetration test, and calculating the second relative density value according to the overconsolidation ratio and the normalized corrected cone tip resistance; Calculating the third relative density value using the cone tip resistance and the vertical effective stress.

6. The method for calculating the peak friction angle based on the static cone penetration test according to claim 5, The characteristics are that the obtaining the overconsolidation ratio of the seabed soil according to the static cone penetration test includes: Calculating the unit weight of the seabed soil using the side friction resistance; Calculating the total stress at the measuring point of the seabed soil based on the unit weight of the soil and the penetration depth into the seabed; Combining the soil layer type, the total stress at the measuring point, and the corrected cone tip resistance to estimate the maximum past effective consolidation stress; Calculating the overconsolidation ratio of the seabed soil using the maximum past effective consolidation stress and the vertical effective stress.

7. The method for calculating the peak friction angle based on the static cone penetration test according to claim 6, The characteristics are that the obtaining the vertical effective stress of the seabed soil based on the static cone penetration test includes: Calculating the pore water pressure of the seabed soil using the seawater depth, the penetration depth into the seabed, and the unit weight of seawater; Calculate the vertical effective stress of the seabed soil using the pore water pressure and the total stress at the measuring point.

8. A method for calculating the peak friction angle based on the static cone penetration test according to claim 6, It is characterized in that calculating the total stress at the measuring point of the seabed soil based on the unit weight of the soil and the penetration depth into the seabed includes: Calculate the soil stress at the measuring point of the seabed soil using the unit weight of the seawater and the seawater depth; Calculate the water stress at the measuring point of the seabed soil using the unit weight of the soil and the penetration depth into the seabed; Calculate the total stress at the measuring point of the seabed soil according to the soil stress at the measuring point and the water stress at the measuring point.

9. A peak friction angle calculation system based on static cone penetration test, characterized in that, It includes: A processor, an input device, an output device, and a memory. The processor, the input device, the output device, and the memory are interconnected. Among them, the memory is used to store a computer program, the computer program includes program instructions, and the processor is configured to call the program instructions to execute a method for calculating the peak friction angle based on a static cone penetration test according to any one of claims 1 to 8.

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