A method and system for calculating peak friction angle based on static penetration test

Abstract

The present invention relates to the field of peak friction angle calculation, specifically a method and system for calculating peak friction angle based on static penetration tests. The method comprises: conducting a static 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 a corrected cone tip resistance; using the corrected cone tip resistance and the side friction resistance to calculate the relative side friction ratio of the seabed soil; using the relative side friction ratio and the corrected cone tip resistance to determine the soil layer type of the seabed soil; and calculating the peak friction angle estimation value based on the soil layer type. The present invention solves the problem in the prior art that the calculation of the peak friction angle is not accurate and scientific due to the complex and changeable environment of the peak friction angle estimation. The present invention greatly improves the accuracy and scientificity of the peak friction angle estimation.

Description

Technical Field

[0001] The invention relates to the field of peak friction angle calculation, in particular to a peak friction angle calculation method and system based on static penetration test. Background Art

[0002] Soil strength indicators, especially the effective peak friction angle, are important parameters for evaluating soil stability and bearing capacity. They are widely used in marine engineering, foundation design, slope stability analysis, and other fields. In engineering practice, these indicators are often estimated indirectly through in-situ test data, with the cone penetration test (CPT) being a mainstream method. This method offers advantages such as high testing efficiency, strong continuity, and no soil sample disturbance. It is particularly suitable for obtaining preliminary strength parameters for soft clay or marine sedimentary layers.

[0003] However, the traditional method of estimating the peak friction angle has considerable uncertainty. Among them, the inaccurate definition of soil layer type has the greatest impact on the estimation of the peak friction angle, because different soil layer types use different calculation methods, and the same calculation method causes changes in estimation accuracy due to complex environmental changes. As a result, the estimation of the peak friction angle is still a huge problem today.

[0004] Commonly used techniques in existing technologies include inversion calculations: Some studies have inputted CPT measured data into finite element or finite difference models to optimize soil strength indicators through inversion calculations. However, this method requires the construction of complex models, relies on a large number of input parameters (such as elastic modulus, stress path, drainage conditions, etc.), and requires repeated iterative calculations, making it difficult to apply to rapid engineering judgment scenarios. In recent years, some methods have introduced algorithms combining graph discrimination with rule-based reasoning: These methods use machine learning or Bayesian models as input and output soil property indicators or strength ranges. While this improves the level of automation, the models are highly "black box" and rely heavily on training samples, making it difficult to ensure cross-regional universality and engineering interpretability. Therefore, existing technologies urgently need a more intelligent and accurate method for calculating peak friction angle. Summary of the Invention

[0005] In view of the defects in the prior art, the present invention provides a method and system for calculating the peak friction angle based on static 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] In order to achieve the above-mentioned purpose, one aspect of the present invention provides a method for calculating the peak friction angle based on a static penetration test, comprising: conducting a static 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 a corrected cone tip resistance; using the corrected cone tip resistance and the side friction resistance to calculate the relative side friction resistance ratio of the seabed soil; using the relative side friction resistance ratio and the corrected cone tip resistance to determine the soil layer type of the seabed soil; 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 penetration, and corrects the cone tip resistance based on seawater depth, penetration depth and seawater gravity, eliminating the interference of the seawater environment on the mechanical parameters and improving the accuracy of the parameters. The relative side friction resistance ratio is then calculated based on the corrected cone tip resistance and side friction resistance, and the basis for soil type determination is constructed in combination with the corrected cone tip resistance, breaking through the bottleneck of difficult soil type definition under complex conditions such as seabed transition layer and disturbance layer, and calculating the peak friction angle estimate based on the determined soil layer type, thereby improving the accuracy and scientificity of the peak friction angle calculation.

[0008] Optionally, the soil layer types include clay, silt and sand, and the clay meets and , the silt satisfies and , the sand meets and ,in, To correct the cone tip resistance, is the friction ratio of the opposite sides.

[0009] This invention precisely defines three soil types: clay, silt, and sand, by defining the threshold range for modifying the ratio of cone tip resistance to relative friction. This quantitative standard provides a clear and actionable basis for identifying soil types in complex seabed formations, resolving the difficulty in defining transition and disturbed layers, and further improving the scientific and accurate nature of soil type determination.

[0010] Optionally, the calculation of the peak friction angle estimate based on the soil layer type includes: setting a first weight set based on the soil layer type; using multiple methods to calculate the peak friction angle of the seabed soil to obtain multiple peak friction angle values; and using the first weight set to perform weighted summation on the peak friction angle values ​​to obtain a peak friction angle estimate.

[0011] The present invention calculates multiple peak friction angle values ​​using a variety of methods, encompassing different theoretical perspectives, and then uses a weighted summation method. This method avoids the limitations of a single calculation method and, by adapting the soil layer type, allows the weight distribution to align with the actual mechanical mechanisms of the soil, significantly improving the accuracy of the peak friction angle estimate.

[0012] Optionally, the use of multiple methods to calculate the peak friction angle of the seabed soil to obtain multiple peak friction angle values ​​includes: using the normalized corrected cone tip resistance to calculate a first peak friction angle estimate; obtaining a relative density estimate of the seabed soil based on the static penetration test, and using the relative density estimate to calculate a second peak friction angle estimate; obtaining the vertical effective stress of the seabed soil based on the static penetration test, and using the vertical effective stress and the corrected cone tip resistance to calculate a third peak friction angle estimate.

[0013] The present invention uses normalized modified cone tip resistance to calculate the first peak friction angle estimate, explores the value of the cone tip mechanical signal, uses relative density to calculate the second peak friction angle estimate, associates structural characteristics, and calculates the third peak friction angle estimate based on vertical effective stress and modified cone tip resistance. It integrates into the stress environment, and multiple methods cover different mechanical, structural, and stress factors, complementing and verifying each other, thereby improving the accuracy and scientificity of the peak friction angle estimate.

[0014] Optionally, the relative density estimation value of the seabed soil obtained based on the static 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 penetration test to obtain multiple relative density values; and using the second weight set to perform weighted summation on the relative density values ​​to obtain a relative density estimation value.

[0015] Multiple relative density values ​​are calculated using a variety of methods, encompassing different calculation logics, and then weighted and summed using a set of weights. This overcomes the adaptability limitations of a single method and, by assigning weights tailored to soil layer types, ensures that the results align with the soil's true density, improving the accuracy of the relative density estimates.

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

[0017] The present invention first normalizes and corrects the cone tip resistance to calculate the first relative density value, focuses on the core mechanical parameters, combines the overconsolidation ratio and the normalized cone tip resistance to calculate the second relative density value, incorporates the stress history dimension, and then uses the cone tip resistance and vertical effective stress to calculate the third relative density value, strengthening the stress-density correlation. Multiple methods cover different influencing factors, verify and supplement each other, break through the limitations of a single method, and improve the accuracy and scientificity of the relative density value.

[0018] Optionally, the over-consolidation ratio of the seabed soil obtained according to the static 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 based on the soil layer type, the total stress at the measuring point and the corrected cone tip resistance; and calculating the over-consolidation ratio of the seabed soil using the maximum past effective consolidation stress and the vertical effective stress.

[0019] The present invention calculates the unit weight of soil through lateral friction resistance, and obtains the total stress of the measuring point in combination with the penetration depth. The soil layer type, total stress and modified cone tip resistance are then integrated to estimate the historical maximum effective consolidation stress, and finally combined with the vertical effective stress to obtain the over-consolidation ratio. From the perspective of multi-dimensional analysis such as soil deadweight and stress history, the lateral friction resistance is associated with the physical properties of the soil, and the total stress is used to reflect the double-layer load effect of the seabed. The soil layer type is used to adapt to the stress response differences of different soil types, so that the over-consolidation ratio calculation takes into account both in-situ test data and the historical stress state of the soil, thereby improving the accuracy of the over-consolidation ratio calculation.

[0020] Optionally, obtaining the vertical effective stress of the seabed soil based on the static 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; and 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 by taking into account the seawater depth, penetration depth and unit weight of seawater. The vertical effective stress is then derived by combining the total stress at the measuring point. This follows the principle of hydrostatic pressure, eliminates interference from seawater loads, removes the influence of pore water pressure, and highlights the effective stress borne by the soil skeleton. This ensures that the mechanical analysis of the seabed soil is close to the actual stress state and improves the accuracy of the total stress at the measuring point.

[0022] Optionally, the calculation of the total stress of the seabed soil at the measuring point based on the unit weight of the soil and the penetration depth into the seabed includes: calculating the soil stress of the seabed soil at the measuring point using the unit weight of seawater and the seawater depth; calculating the water stress of the seabed soil at the measuring point using the unit weight of the soil and the penetration depth into the seabed; and calculating the total stress of the seabed soil at the measuring point based on 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 measuring point by the unit weight of seawater and the seawater depth, and calculates the water stress at the measuring point by the unit weight of the soil and the penetration depth, and then sums them up to obtain the total stress. This quantifies the double-layer load effect of seawater ballast and soil deadweight, follows the principle of superposition of hydrostatic pressure and deadweight stress, removes the interference of pore water pressure, accurately reflects the actual stress state of the seabed soil, and improves the accuracy of the total stress at the measuring point.

[0024] Another aspect of the present invention provides a peak friction angle calculation system based on static penetration test, comprising: a processor, an input device, an output device and a memory, wherein 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 a peak friction angle calculation method based on static penetration test as described in any one of the previous aspects of the present invention.

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

[0026] Figure 1 This is a flow chart of a method for calculating a peak friction angle based on a static penetration test according to an embodiment of the present invention;

[0027] Figure 2 The figure is a schematic structural diagram of a peak friction angle calculation system based on a static penetration test according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] Specific embodiments of the present invention will be described in detail below. It should be noted that the embodiments described herein are for illustrative purposes only and are not intended to limit the present invention. In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that these specific details are not necessarily required to practice the present invention. In other instances, well-known circuits, software, or methods are not specifically described to avoid obscuring the present invention.

[0029] Throughout this specification, references to "one embodiment," "an embodiment," "an 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. Therefore, appearances of the phrases "in one embodiment," "in an embodiment," "an example," or "an example" in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in any suitable combinations and / or subcombinations in one or more embodiments or examples. Furthermore, those of ordinary skill in the art will appreciate that the figures provided herein are for illustrative purposes only and are not necessarily drawn to scale.

[0030] See Figure 1 ,In an optional embodiment, in order to address the ,deficiencies in the prior technology, such as Figure 1 A method for calculating the peak friction angle based on a static penetration test is shown, comprising the following steps:

[0031] Step S1, performing a static 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.

[0032] In this example, the cone penetration test (CPT) is an in-situ testing technique that uses a mechanical or hydraulic device to penetrate a conical probe equipped with sensors into the soil at a constant rate, collecting real-time data on parameters such as pile tip resistance, pore water pressure, and side friction. This test simultaneously records both the seawater depth and the penetration depth into the seabed. The data is typically presented as a graph that changes with penetration depth. It offers advantages such as high testing efficiency, strong continuity, and no disturbance to the soil sample. It is particularly suitable for obtaining mechanical parameters in soft clay or marine sediments.

[0033] When conducting a static penetration test on the seabed, a cone probe equipped with a pressure sensor is penetrated into the seabed soil at a constant rate through underwater detection equipment, and the resistance strain sensor at the front end of the probe is used to collect the cone tip resistance in real time. , synchronously obtain the side friction resistance through the side wall friction tube sensor .

[0034] Use depth encoder and GPS positioning system to record penetration depth into the seabed and sea depth .

[0035] Unit weight of seawater By measuring seawater temperature and salinity on-site and calculating them in combination with the international seawater state equation (or directly using the standard value of 1025kg / m³), all data are transmitted to the deck data acquisition system via waterproof cables and stored in real time at a frequency of 10Hz to form a depth-parameter curve.

[0036] Step S2: correcting the cone tip resistance using the seawater depth, the seabed penetration depth, and the unit weight of seawater to obtain a corrected cone tip resistance.

[0037] The modified cone tip resistance satisfies the following formula:

[0038] ,

[0039] in, To correct the cone tip resistance, is the cone tip resistance obtained from the static penetration test, is the cone tip area ratio, Unit weight of seawater, is the seawater depth, The depth of penetration into the seabed.

[0040] The cone tip area ratio in the above formula is , which reflects the actual effect of pore pressure on the cone head area, and the empirical value is usually 0.8.

[0041] In the seabed environment, the seawater and the seabed soil form a pressure field, and the permeable area at the tip of the cone (accounting for ,because is the cone tip area ratio) will be affected by the unit weight of seawater , seawater depth and penetration depth into the seabed The superimposed total water depth generates pressure, which offsets part of the measured cone tip resistance The formula calculates the amount of pressure acting on the permeable area. , add it back to On the other hand, it can eliminate the interference of seawater pressure and make More accurately reflects the seabed soil's own resistance to cone penetration.

[0042] Step S3: Calculate the relative side friction ratio of the seabed soil using the modified cone tip resistance and the side friction resistance.

[0043] The friction ratio of the opposite side satisfies the following formula:

[0044] ,

[0045] in, is the friction ratio of the opposite side, is the lateral friction resistance, To correct the cone tip resistance.

[0046] In this embodiment, the core of the above formula is to quantify the contribution ratio of the friction resistance of the soil side wall to the probe and the correction resistance of the soil end to the probe during the cone tip penetration process by comparing the relative strengths of the two.

[0047] Step S4: determining the soil layer type of the seabed soil using the opposite side friction ratio and the modified cone tip resistance.

[0048] Soil types include clay, silt and sand, and the clay meets and , the silt satisfies and , the sand meets and ,in, To correct the cone tip resistance, is the friction ratio of the opposite sides.

[0049] Corrected cone tip resistance It reflects the resistance of the soil during the local compression of the cone head and is an important indicator of the overall strength and density of the soil. In general, sand has a high peak compressive strength due to its strong skeleton support. It is usually much higher than silt and clay; however, clay has a loose structure, poor drainage conditions, and limited bearing capacity. The value is relatively low.

[0050] Opposite side friction ratio It reflects the ratio between the shear resistance and principal compressive strength of the soil during cone shearing. It is an important indicator that indirectly reflects the ratio of the friction resistance and cohesion of the soil. Clay exhibits a higher friction resistance ratio due to its significant cohesion and flow characteristics during shearing. The value is relatively high; while the friction contribution of sand during shear is relatively low. The value is smaller.

[0051] Therefore, when considering the and When two parameters are used, the comprehensive mechanical behaviors of different types of soil can be distinguished more effectively. +High " usually indicates clay; " medium +Medium " indicates silt; while "high +Low " typically represents sandy soil. Based on this characteristic difference, the present invention constructs three types of interval division rules to achieve automatic identification of soil layer types and accurate matching of weight paths.

[0052] Step S5: Calculate an estimated value of the peak friction angle based on the soil layer type.

[0053] Calculating the estimated value of the peak friction angle based on the soil layer type specifically includes the following sub-steps:

[0054] Step S51: setting a first weight set based on the soil layer type.

[0055] The first weight satisfies the following formula:

[0056] ,

[0057] in, is the first weight set, For soil layer type, For clay, For silt, It is sandy soil.

[0058] The dominant strength mechanisms of different soil types (clay NT, silt FT, and sand ST) differ significantly. Clay's strength is centered on cohesion, with lateral friction ratio and consolidation history having a more pronounced influence on the friction angle. Silt is in a clay-sand transitional state, where the coupling of density and cohesion is more critical. Sand's strength depends entirely on particle friction and embedment, with density being the core controlling factor. By comparing the prediction errors of different computational models (such as the cone tip resistance model, lateral friction model, and density model) for the peak friction angle of each soil type, the optimal weighting was determined through regression: clay prioritizes the lateral friction correlation model (third weight 0.8), silt enhances the density correlation model (third weight 0.9), and sand emphasizes the cone tip resistance-density model (second weight 0.8). This soil-type-driven weighting design allows the multi-model fusion results to more closely align with actual mechanical properties, addressing the generalizability limitations of single models.

[0059] Step S52: Calculate the peak friction angle of the seabed soil using multiple methods to obtain multiple peak friction angle values.

[0060] Calculating the peak friction angle of the seabed soil using multiple methods to obtain multiple peak friction angle values ​​specifically includes the following sub-steps:

[0061] Step S521 , normalizing the corrected cone tip resistance to obtain a normalized corrected cone tip resistance.

[0062]

[0063] in, is the normalized modified cone tip resistance, To correct the cone tip resistance, is the atmospheric pressure, is the vertical effective stress value.

[0064] The above formula is based on atmospheric pressure As the base dimension, the numerator The cone tip resistance will be corrected Convert to multiples of atmospheric pressure, unify stress magnitude, denominator The vertical effective stress The square root ratio of the relative atmospheric pressure represents the strength of the current stress environment. The normalized value of the pressure-corrected cone tip resistance is divided by the square root of the pressure-normalized stress environment to obtain the normalized corrected cone tip resistance. In essence, it is the normalized result of the modified cone tip resistance on the effective stress-atmospheric pressure coupling field. It not only strips away the effective stress differences caused by the seabed depth and seawater weight, but also retains the intrinsic strength information such as the density and particle bite of the soil itself, so that the modified cone tip resistance at different seabed positions and depths can be compared under a unified stress-strength dimension.

[0065] Simplifying and transforming the above formula, we can get:

[0066]

[0067] Step S522: Calculate a first peak friction angle estimation value using the normalized corrected cone tip resistance.

[0068] In an optional embodiment, the first peak friction angle estimate satisfies the following formula:

[0069] ,

[0070] in, is the estimated value of the first peak friction angle, Corrected cone tip resistance for normalization.

[0071] The above formula is corrected by normalizing the cone tip resistance The external stress field interference such as atmospheric pressure and effective stress has been eliminated, and only the intrinsic characteristics such as soil density and particle bite are focused. The logarithmic function is compressed. The wide range of changes (0.1-1000 spans more than ten thousand times) is consistent with the marginal decreasing law of the contribution of density improvement to friction angle (such as For every 10-fold increase, the friction angle increases by about 11°). The base value is 17.6. The baseline friction angle at 90° corresponds to extremely loose marine sedimentary soil, and the coefficient 11 is obtained by regression of seabed penetration data, which ultimately achieves a rapid conversion from in-situ test parameters to peak friction angle estimates.

[0072] Step S523: obtaining an estimated value of the relative density of the seabed soil based on the static penetration test, and calculating an estimated value of the second peak friction angle using the estimated value of the relative density.

[0073] The estimated value of the second peak friction angle satisfies the following formula:

[0074] ,

[0075] in, is the estimated value of the second peak friction angle, is an estimated value of relative density.

[0076] The above formula takes 28° as the reference value (corresponding to relative density The contribution of density to the friction angle is quantified by the coefficient 12.5, that is, For every 1% increase, the friction angle increases linearly by 0.125. The physical core of this relationship is: relative density Directly reflects the arrangement density of soil particles ( The higher the density, the stronger the particle bite and embedment, and the greater the frictional resistance during shear). The formula converts the density-dominated strength gain into a friction angle increment in the form of linear superposition. The coefficient and the benchmark value are derived from the statistical regression of seabed sediments, enabling a rapid conversion from density estimates to friction angles.

[0077] The step of obtaining an estimated value of the relative density of the seabed soil based on the static penetration test specifically includes the following sub-steps:

[0078] Step S5231: setting a second weight set based on the soil layer type.

[0079] The second weight set satisfies the following formula:

[0080] ,

[0081] in, is the second weight set, For soil layer type, For clay, For silt, It is sandy soil.

[0082] The above formula is based on the differences in the strength dominant mechanisms of clay NT, silt FT, and sand ST. After statistical optimization through seabed in-situ tests and indoor tests, the strength of clay is centered on cohesion, and the lateral friction resistance contributes more significantly to the friction angle. Therefore, The highest proportion is given to the lateral friction resistance correlation model. Silt belongs to the clay-sand transition state, and the density and cohesion coupling effect are key. The pure cohesion model is weakened and the density-cohesion coupling model is strengthened. The strength of sand depends on particle friction, and the density reflected by the normalized cone tip resistance is the core. Let the density-friction model dominate, drive the model weight adaptation through soil characteristics, and make up for the universality defects of a single model.

[0083] Step S5232: Based on the static penetration test, a plurality of methods are used to calculate the relative density of the seabed soil to obtain a plurality of relative density values.

[0084] The relative density of the seabed soil is calculated based on the static penetration test using a variety of methods to obtain multiple relative density values, including:

[0085] Step S52321: Calculate a first relative density value using the normalized corrected cone tip resistance.

[0086] ,

[0087] in, is the first relative density value, Corrected cone tip resistance for normalization.

[0088] The above formula is based on the statistical regression of a large number of seabed static penetration and density measurement data, and uses normalized correction of cone tip resistance The nonlinear relationship between cone tip resistance and density is adapted through logarithmic transformation. The principle is that when the soil density increases, the particle bite effect is exponentially enhanced, 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. Minus 1 is the intercept correction, which corresponds 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, the efficient conversion of in-situ sounding parameters to relative density is achieved.

[0089] Step S52322: obtaining the overconsolidation ratio of the seabed soil according to the static penetration test, and calculating a second relative density value according to the overconsolidation ratio and the normalized corrected cone tip resistance.

[0090] The second relative density value satisfies the following formula:

[0091] ,

[0092] in, is the second relative density value, is the normalized modified cone tip resistance, is the overconsolidation ratio.

[0093] The above formula corrects the structural interference of overconsolidation by integrating the intrinsic density of soil and stress history. Normalized Corrected Cone Tip Resistance The intrinsic density basis that describes the interlocking of soil particles, and the overconsolidation ratio (Overconsolidated soil forms a compact structure due to historical high stress) This will cause the normalized modified cone tip resistance to be mixed with a false compaction signal of structural reinforcement. The formula is The structural contribution is attenuated in the denominator (the larger the overconsolidation ratio, the stronger the peeling), and the exponential correlation between the cone tip resistance and density is linearized with the square root. The empirical coefficient 305 is derived from the seabed test statistics. Finally, the density signal without structural interference is converted into a relative density percentage. .

[0094] The method of obtaining the overconsolidation ratio of the seabed soil according to the static penetration test comprises the following steps:

[0095] Step S523221: Calculate the unit weight of the seabed soil using the side friction resistance.

[0096] The unit weight of soil satisfies the following formula:

[0097] ,

[0098] in, is the unit weight of soil, is the lateral friction resistance.

[0099] The above formula is based on the lateral friction resistance Estimate the unit weight of seabed soil. Utilizing the positive correlation between lateral friction and soil density, the wide variation of lateral friction is compressed through logarithmic transformation, adapting to the marginal decreasing law of the contribution of density improvement to unit weight. Taking the benchmark value of 26 as the upper limit of the dense soil weight, the weight reduction of loose soil is adjusted by the coefficient 14 and the square term, where: The lateral friction resistance is converted into a density index, and the square operation of the denominator further smoothes the density changes to ensure that the calculated density of extremely loose soil conforms to the characteristics of marine sedimentary soil. This empirical model is based on the statistical regression of seabed static sounding data and soil weighing tests to achieve efficient conversion of in-situ parameters to physical indicators.

[0100] Step S523222: Calculate the total stress of the seabed soil at the measuring point based on the unit weight of the soil and the penetration depth into the seabed.

[0101] 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:

[0102] Step S5232221, calculating the soil stress at the measuring point of the seabed soil using the unit weight of the seawater and the seawater depth.

[0103] The soil stress at the measuring point satisfies the following formula:

[0104] ,

[0105] in, is the soil stress at the measuring point, is the unit weight of seawater, The depth of sea water.

[0106] The above formula quantifies the ballast effect of seawater weight on the seabed surface. The unit weight of seawater is and water depth Multiply them 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 seawater load to the seabed soil. It is the basic boundary condition for subsequent analysis of the effective stress and strength characteristics of the soil. In essence, it is the direct application of the hydrostatic pressure formula in the calculation of the seabed surface stress field.

[0107] 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.

[0108] ,

[0109] in, is the water stress at the measuring point, is the unit weight of soil, The depth of penetration into the seabed.

[0110] The above formula is to quantify the contribution of the seabed soil's own weight to the stress at the penetration depth, expressed as the unit weight of the soil. It is a heavy indicator and the depth of penetration into the seabed The vertical stress formed by the superposition of the soil's own weight at that depth is directly calculated by multiplying the soil thickness above the corresponding calculation point, which serves as the deadweight load basis for analyzing the effective stress and strength characteristics of the seabed soil.

[0111] Step S5232223: Calculate the total stress of the seabed soil at the measuring point based on the soil stress at the measuring point and the water stress at the measuring point.

[0112] ,

[0113] in, is the total stress at the measuring point, is the unit weight of seawater, is the seawater depth, is the unit weight of soil, The depth of penetration into the seabed.

[0114] The above formula is the superposition of the deadweight load of the double-layer structure of the seabed, and the hydrostatic pressure of the seawater column , and penetration depth The self-weight stress of the seabed soil above Directly sum to obtain the total vertical stress at the measuring point.

[0115] Step S523223, estimating the maximum past effective consolidation stress based on the soil layer type, the total stress at the measuring point, and the modified cone tip resistance.

[0116] In this embodiment, the maximum past effective consolidation stress refers to the maximum vertical effective stress that the soil sample has ever experienced during its soil formation or loading history.

[0117] ,

[0118] in, is the maximum past effective consolidation stress, To correct the 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 type.

[0119] When the soil type is clay , when the soil type is silt , when the soil type is sandy soil .

[0120] The above formula is obtained by integrating the difference between the modified cone tip resistance and the current total stress, combined with the soil layer type parameters (Clay 0.72, silt 0.8, sand 0.85) and atmospheric pressure reference , inverse the historical maximum effective consolidation stress of the seabed soil, using Quantify the difference in historical stress contribution of overconsolidated soil by Adapt to the stress response characteristics of different soil types (sand particle friction dominates the failure The stress value is then normalized to atmospheric pressure to eliminate environmental interference, and finally calibrated to the historical stress estimate using an empirical coefficient of 0.33.

[0121] Step S523224: Calculate the overconsolidation ratio of the seabed soil using the maximum past effective consolidation stress and the vertical effective stress.

[0122] The overconsolidation ratio satisfies the following formula:

[0123] ,

[0124] in, is the overconsolidation ratio, To correct the 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 type.

[0125] The overconsolidation ratio, the ratio of the soil's historical maximum effective consolidation stress to its current effective stress, is a core indicator reflecting the historical stress state of seabed soil (overconsolidation / normal consolidation / underconsolidation). Its significance lies in: quantifying the strengthening effect of historical stress on soil structure (e.g., overconsolidated soil forms a compact structure due to past high stress), providing a benchmark for the mechanical analysis of the difference between the modified cone tip resistance and the current stress, and then serving as a key input for calculating relative density. Furthermore, through a soil type identification mechanism (combining the modified cone tip resistance with the lateral friction resistance ratio), it drives the allocation of multi-model weights (e.g., the weights of formulas related to sand and clay corresponding to different overconsolidation ratios), ultimately serving as a precise estimate of the peak friction angle and providing a quantitative basis for the stress history dimension for marine engineering foundation stability analysis and slope bearing capacity assessment.

[0126] Step S52323: Calculate a third relative density value using the cone tip resistance and the vertical effective stress.

[0127] ,

[0128] in, is the third relative density value, is the cone tip resistance value, is the vertical effective stress value.

[0129] The above formula is based on the cone tip resistance Reflects the compaction characteristics of the soil, combined with vertical effective stress Considering the influence of stress environment, the nonlinear relationship between cone tip resistance and density is adapted by logarithmic operation, and the coefficient and The ratio of cone tip resistance to effective stress is converted into the third relative density through experimental statistical regression. , to achieve quantitative estimation of soil compaction state based on static penetration parameters.

[0130] Step S5233: Use the second weight set to perform weighted summation on the relative density values ​​to obtain a relative density estimation value.

[0131] The relative density estimation value satisfies the following formula:

[0132] ,

[0133] in, is the estimated value of relative density, is the normalized modified cone tip resistance, is the overconsolidation ratio, is the cone tip resistance value, is the vertical effective stress value, For soil layer type, For clay, For silt, It is sandy soil.

[0134] In this embodiment, accurate estimation of seabed soil density is achieved by integrating multiple relative density calculation models and assigning weights based on soil characteristics. In actual engineering, the strength mechanisms of clay, silt, and sand differ significantly (for example, clay relies on cohesion, and sand relies on particle friction). After identifying the soil type based on the modified cone tip resistance and lateral friction resistance ratio, the formula assigns differentiated weights to different calculation methods. This not only avoids the adaptability of a single formula to complex strata, but also improves the robustness of the results through weighted fusion. This makes the estimated relative density more consistent with the actual state of the soil, provides key parameter support for the subsequent peak friction angle calculation, and solves the engineering problem of large estimation deviations of traditional single models under complex seabed geological conditions.

[0135] Step S524: obtaining the vertical effective stress of the seabed soil based on the static penetration test, and calculating an estimated value of the third peak friction angle using the vertical effective stress and the modified cone tip resistance.

[0136] The estimated value of the third peak friction angle satisfies the formula:

[0137] ,

[0138] in, is the estimated value of the third peak friction angle, To correct the cone tip resistance, is the vertical effective stress value.

[0139] The above formula is corrected by the cone tip resistance and vertical effective stress The nonlinear relationship between the two is linearized using logarithmic transformation, and then combined with the coefficients 0.1 and 0.38 (determined by statistical regression), the ratio information is converted into the input of the inverse tangent function, and the estimated value of the third peak friction angle is finally calculated. , to achieve quantitative estimation of the third peak friction angle of soil based on static penetration parameters.

[0140] The vertical effective stress of the seabed soil obtained based on the static penetration test includes:

[0141] Step S5241: Calculate 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.

[0142]

[0143] in, is the pore water pressure, is the unit weight of seawater, is the seawater depth, Depth of penetration into the seabed.

[0144] The above formula adds the depth of seawater to the depth of penetration into the seabed to obtain the total liquid column height of seawater and the seawater in the soil pores corresponding to the penetration depth. The total liquid column height is then multiplied by the unit weight of seawater to calculate the pore water pressure formed by seawater at the measuring point in the seabed soil. This reflects the hydrostatic pressure principle that the pore water pressure varies linearly with the height of the liquid column.

[0145] Step S5242: Calculate the vertical effective stress of the seabed soil using the pore water pressure and the total stress at the measuring point.

[0146] The vertical effective stress satisfies the following formula:

[0147] ,

[0148] in, For vertical effective effect, is the pore water pressure. Substituting the above expression of vertical effective stress and pore water pressure into the vertical effective stress expression, we can get:

[0149] ,

[0150] in, is the unit weight of seawater, is the unit weight of soil, Depth of penetration into the seabed

[0151] Step S53: performing weighted summation on the peak friction angle values ​​using the first weight set to obtain an estimated peak friction angle value.

[0152] The estimated value of the peak friction angle satisfies the following formula:

[0153] ,

[0154] in, is the estimated value of the peak friction angle, is the normalized modified cone tip resistance, is the estimated value of relative density, To correct the cone tip resistance, is the vertical effective stress value, For soil layer type, For clay, For silt, It is sandy soil.

[0155] In this embodiment, a precise estimation of the peak friction angle is achieved by integrating multiple peak friction angle calculation models and assigning weights based on soil characteristics. The model automatically identifies soil layer types such as clay, silt, and sand, assigning differentiated weights to different calculation methods. This not only avoids the adaptability of a single formula to complex strata, but also weights the calculation methods that are not suitable for it. This makes the estimated peak friction angle more accurate, further resolving the engineering problem of large estimation errors in traditional single models under complex seabed geological conditions.

[0156] As can be seen from the above, the core process of this invention is a system for calculating the peak friction angle of seabed soil based on the cone penetration test (CPT). It integrates the entire process logic, from raw data acquisition to multi-model weighted fusion. Its core value lies in its ability to systematically address engineering challenges inherent in traditional methods, such as significant parameter interference, ambiguous soil type definitions, and significant bias in single models, through a correction-identification-fusion technical approach.

[0157] First, the cone tip resistance is corrected by the seawater depth, penetration depth and unit weight of seawater to obtain the corrected cone tip resistance without the interference of seawater pressure, ensuring that the parameter reflects the true resistance of the soil. Then, the relative side friction resistance ratio is calculated in combination with the side friction resistance. The soil layer type is accurately identified by the threshold range between the corrected cone tip resistance and the relative side friction resistance ratio ( and For clay, and For silt, and is sand), breaking through the bottleneck of seabed transition layer identification.

[0158] During the peak friction angle calculation stage, the system innovatively constructs a soil type-weight dynamic matching mechanism: the first weight set is set for clay, silt, and sand respectively, and three calculation models are integrated - a logarithmic model based on normalized corrected cone tip resistance, a linear model based on relative density, and an inverse tangent model based on effective stress and ratio. Among them, the calculation of relative density also adopts weighted fusion, and the overconsolidation ratio is introduced to eliminate stress history interference so that the relative density estimate is more in line with the actual density state of the soil.

[0159] The engineering significance of this method lies in that, through multi-parameter collaborative correction and multi-model intelligent fusion, the complex stress history, structural characteristics and mechanical response of the seabed soil are quantitatively associated, so that the error of the peak friction angle estimation value is greatly reduced compared with the traditional single model, providing traceable and easily verifiable accurate parameters for marine pile foundation bearing capacity assessment, seawall slope stability analysis, etc.

[0160] like Figure 2As shown, on the other hand, the present invention also provides a peak friction angle calculation system based on static penetration test, including: a processor, an input device, an output device and a memory, wherein 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 relevant steps of a relevant embodiment of a peak friction angle calculation method based on static penetration test of the present invention.

[0161] The present invention provides a peak friction angle calculation system based on a static penetration test. Each functional component can be integrated into a single processing unit, each component can exist physically separately, or two or more components can be integrated into a single unit. The integrated components can be implemented in either hardware or software.

[0162] 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 it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. A method for calculating the peak friction angle based on static penetration test, Its characteristic is that the method comprises: Conduct static penetration tests on the seabed to obtain the cone tip resistance, side friction resistance, penetration depth, unit weight of seawater, and seawater depth of the seabed soil; Correcting the cone tip resistance using the seawater depth, the seabed penetration depth, and the unit weight of seawater to obtain a corrected cone tip resistance; Calculating the relative side friction resistance ratio of the seabed soil using the modified cone tip resistance and the side friction resistance; Determining the soil layer type of the seabed soil using the opposite side friction ratio and the modified cone tip resistance; Calculating an estimate of the peak friction angle based on the soil type involves: setting a first weight set based on the soil layer type; By calculating the peak friction angle of the seabed soil, multiple peak friction angle values ​​are obtained, including: Normalizing the corrected cone tip resistance to obtain a normalized corrected cone tip resistance; Calculating a first peak friction angle estimation value using the normalized corrected cone tip resistance; Obtaining an estimated value of the relative density of the seabed soil based on the static penetration test, and calculating an estimated value of the second peak friction angle using the estimated value of the relative density; The relative density estimation value of the seabed soil obtained based on the static penetration test includes: setting a second weight set based on the soil layer type; Calculating the relative density of the seabed soil based on the static penetration test to obtain a plurality of relative density values; Performing a weighted summation on the relative density values ​​using the second weight set to obtain a relative density estimation value; Obtaining a vertical effective stress of the seabed soil based on the static penetration test, and calculating an estimated value of the third peak friction angle using the vertical effective stress and the modified cone tip resistance; The peak friction angle values ​​are weighted and summed using the first weight set to obtain a peak friction angle estimate.

2. The method for calculating the peak friction angle based on a static penetration test according to claim 1, wherein the soil layer types include clay, silt and sand, and the clay satisfies and , the silt satisfies and , the sand meets and ,in, To correct the cone tip resistance, is the friction ratio of the opposite sides.

3. The method for calculating the peak friction angle based on the static penetration test according to claim 1, Its characteristic is that the relative density of the seabed soil is calculated based on the static penetration test to obtain multiple relative density values ​​including: Calculating a first relative density value using the normalized corrected cone tip resistance; Obtaining an overconsolidation ratio of the seabed soil according to the static penetration test, and calculating a second relative density value according to the overconsolidation ratio and the normalized corrected cone tip resistance; A third relative density value is calculated using the cone tip resistance and the vertical effective stress.

4. The method for calculating the peak friction angle based on the static penetration test according to claim 3, The method is characterized in that the overconsolidation ratio of the seabed soil obtained according to the static penetration test includes: Calculating the unit weight of the seabed soil using the side friction resistance; Calculating the total stress of the seabed soil at the measuring point based on the unit weight of the soil and the penetration depth into the seabed; estimating the maximum past effective consolidation stress based on the soil layer type, the total stress at the measuring point, and the modified cone tip resistance; The overconsolidation ratio of the seabed soil is calculated using the maximum past effective consolidation stress and the vertical effective stress.

5. The method for calculating the peak friction angle based on the static penetration test according to claim 4, Its characteristic is that the vertical effective stress of the seabed soil obtained based on the static 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; The vertical effective stress of the seabed soil is calculated using the pore water pressure and the total stress at the measuring point.

6. The method for calculating the peak friction angle based on the static penetration test according to claim 4, The method is characterized in that the total stress at the measuring point of the seabed soil body is calculated based on the unit weight of the soil body and the penetration depth into the seabed, including: Calculating the stress of the seabed soil at the measuring point using the unit weight of the seawater and the depth of the seawater; 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; The total stress of the seabed soil at the measuring point is calculated based on the soil stress at the measuring point and the water stress at the measuring point.

7. A peak friction angle calculation system based on static penetration test, characterized in that: include: A processor, an input device, an output device and a memory, wherein 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 a peak friction angle calculation method based on a static penetration test as described in any one of claims 1 to 6.

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