Frictional Ratio Research Articles

The role of dynamic friction in the appearance of periodic oscillations in mechanical systems

This article investigates the appearance of periodic mechanical oscillations associated with the transition between static and dynamic friction regimes. The study employs a mechanical system with one degree of freedom and a friction model recently proposed by Brown and McPhee, whose continuity and differentiability properties make it particularly appropriate for an analytical treatment of the equations. A bifurcation study of the system, including stability analysis, transformation to normal form and numerical continuation techniques, reveals that stable periodic orbits can be created either by a supercritical Hopf bifurcation or by a saddle-node bifurcation of limit cycles. The influence of all system parameters on the appearance of periodic oscillations is investigated in detail. In particular, the effect of the friction model parameters (static-to-dynamic friction ratio and transition speed between the static and dynamic regimes) on the bifurcation behavior of the system is addressed.

Gaussian process regression to predict dryout incipience quality of saturated flow boiling in mini/micro-channels

In the present study, a Gaussian process regression (GPR) model is developed to predict the dryout incipience quality for flow boiling in mini / micro – channels based on a consolidated database obtained from Purdue University Boiling and Two – Phase Flow Laboratory (PU – BTPFL) consisting of 997 points from 26 sources. The database includes 13 different working fluids over a wide range of operating conditions: hydraulic diameter (0.51 – 6.0 mm), mass velocities (29 – 2303 kg/ m2 s), liquid – only Reynolds number (125 – 53,770), boiling number (0.31 – 44.3 × 10-4), and reduced pressure (0.005 – 0.78). The inputs to the model were liquid – only Weber number (Wefo), reduced pressure (PR), boiling number (Bo), heated to frictional perimeter ratio(PH/PF), capillary number (Ca) and density ratio (ρg/ρf), and the output was dryout incipience quality. The database was randomly divided into training data to learn GPR kernel (covariance) parameters using maximum likelihood estimation, and test data to evaluate the prediction accuracy of the outputs based on mean absolute error (MAE). Six – different types of covariance functions were tested, and GPR model with automatic relevance detection (ARD) rational quadratic covariance function showed the best overall performance. A performance comparison of approved GPR model was made with an existing highly reliable universal correlation to predict dryout incipience quality for mini / micro – channels. Results show that the developed GPR model exhibits superior generalization ability with an overall MAE of 6.03 %, and a significant reduction of 51.76 % in MAE compared with the universal correlation. Overall, the GPR model was found to be a data efficient machine learning technique for predicting dryout incipience quality for flow boiling in mini / micro – channels based on a consolidated database.

A practical optimisation method for friction tuned mass dampers in multi-storey buildings subjected to earthquake excitations

To reduce lateral drifts, the parameters of friction tuned mass dampers (FTMDs) need to be “tuned up” during the design process, which can be a challenging task for multi-storey buildings subjected to real ground motions. To address this issue, this article proposes a practical particle swarm optimisation (PSO) algorithm to optimise simultaneously the parameters (frequency ratio and friction ratio) of FTMDs fitted on multi-degree of freedom (MDOF) systems and frames subjected to real seismic records. First, elastic MDOF systems with FTMDs were modelled in OpenSees software considering different number of storeys (5, 10 or 20), periods and stiffness distributions. Optimised frequency ratios and friction coefficients of FTMDs and the main structure response were then derived using an objective function that minimised the structures’ maximum average roof displacement. FTMDs with optimised parameters proved very effective at reducing average roof displacements of the examined MDOF structures by up to 39 %, but the magnitude of the reduction depended on the period of the structure. Subsequently, the effectiveness of FTMDs at controlling the response of inelastic steel moment-resisting frames (MRFs) was examined. For the examined structures and seismic records, the use of optimised TMDs led to marginally smaller (2 %) roof displacements when compared to FTMDs. Therefore, FTMDs can be as effective as TMDs devices but with added advantages of less susceptibility to aging and temperature variations. It is also shown that higher mode effects experienced by real MRFs can be captured accurately by equivalent MDOF systems (difference in responses <4 %), which can therefore simplify the design.

Exploring the viability of Bentonite-amended blends incorporating marble dust, sand, and fly ash for the creation of an environmentally sustainable landfill liner system

The development of effective and cost-efficient landfill liners is crucial to prevent groundwater contamination from leachate, safeguarding soil quality and the environment. Composite liners, particularly those combining bentonite with supplementary materials such as fly ash or marble dust, present a promising solution. This study delves into a comprehensive investigation of the physical properties of landfill liners composed of bentonite-fly ash and bentonite-marble dust mixtures through an extensive series of laboratory tests. The research systematically analyzes various proportions of bentonite with fly ash and marble dust, evaluating their impact on liner performance in comparison to Bentonite-sand mixtures. Physicochemical analyses are employed to understand the interactions and behaviors of these distinct substances within the amended bentonite. A wide array of physical properties, including Atterberg’s limits, compaction characteristics, free swell index, modified free swell index, California bearing ratio, cohesion, and angle of internal friction, are meticulously examined. Collectively, these properties offer a comprehensive overview of the suitability and performance potential of bentonite-fly ash and bentonite-marble dust mixtures as landfill liners, presenting a viable alternative to traditional bentonite-sand mixtures. The study reveals synergistic effects between bentonite and both fly ash and marble dust, highlighting their significant contributions to enhancing the physical traits of landfill liners. This advancement in landfill liner design holds the promise of effectively mitigating detrimental environmental impacts associated with waste disposal. While this study provides a robust foundation, it is essential for future investigations to prioritize long-term performance assessments and real-world implementation. Validation and fine-tuning of these findings are crucial to ensuring practical applicability and efficacy within authentic landfill construction scenarios. This holistic approach will contribute to the continued evolution and optimization of landfill liner design, addressing the pressing challenges of sustainable waste management and environmental protection.

A Numerical Model for Analyzing Mechanical Slippage Effect on Crosswell Distributed Fiber-Optic Strain Measurements During Fracturing

Summary Distributed fiber-optic (FO) strain measurements have become a widely used method for monitoring and diagnosing far-field strain induced during hydraulic fracturing (HF). However, field observations have revealed that the mechanical decoupling between the fiber and the rock often happens. Despite this phenomenon, much of the current research assumes that the fiber cable remains mechanically coupled to the rock formation. To improve the accuracy and reliability of field data interpretation, it is essential to better understand the effect of fiber decoupling on strain responses. The objective of this study is to simulate strain responses while taking into account the impact of fiber slippage. In this study, we developed a numerical model that allows for accurate prediction and analysis of strain responses of crosswell distributed FO experiencing mechanical decoupling. Our model first uses the 3D displacement discontinuity method to calculate displacement fields induced by hydraulic fractures. The model then accounts for the occurrence of slippage and calculates the fiber displacement distribution with slippage effect. Additionally, the model can predict fiber strain distribution in cases where the stick-slip behavior is present. To better understand the impact of friction on strain and strain-rate signals, we conduct a sensitivity analysis. This allows us to explore the effects of different friction levels on the signals, which can be critical in achieving more accurate and reliable results. Our model results reveal several key observations. First, when fiber slippage is detected, we typically observe a broadening of the extension zone near the fracture on the strain/strain rate waterfall plots, which cannot provide a well-defined fracture domain corridor. The simulated strain rate pattern matches the field observation. Additionally, the size of the decoupling zone increases as the friction between the fiber and formation decreases. Also, the decoupling generates negative cumulative strain change after a certain period of closure. Furthermore, when the dynamic friction is smaller than the static friction, sudden strain releases appearing as sticking portions were visible in the strain/strain-rate waterfall plots, indicating the occurrence of stick-slip behavior in the fiber. We also observed that the sudden strain releases in the strain rate waterfall plot occur more frequently when the maximum fiber strain gradient is smaller. Moreover, the longer sticking portion was observed when the dynamic/static friction ratio was smaller. The key innovation of this study is the development of a forward numerical model that simulates strain responses while taking into account the coupling effect between fiber and formation. To the best of our knowledge, this is the first time that such a model has been presented. Overall, our study provides an important contribution to the field of HF monitoring by enabling a more accurate and reliable interpretation of strain signals, which can ultimately improve the safety and effectiveness of HF operations.

The influence of laser texturing on the tribological behavior of titanium alloy Ti6Al4V in medical applications

This paper analyzes the tribological behavior of the Ti6Al4V ELI alloy subjected to laser texturization for medical purposes. Laser texturing enables one to observe specific patterns of the material surface at established depths. Microtexturing of the samples was performed using a 355 nm picosecond laser. The influence of the microtexturing process (depending on the process parameters) on the geometric parameters of the proposed laser texturing pattern was evaluated. Selected samples were subjected to tribological testing using the ball-on-plate technique in dry and lubricant-sliding methods (in Ringer solution). The wear properties were evaluated by comparing the coefficient friction, wear volumes, and wear ratio. A scanning electron microscope characterized the morphologies of the wear scar and the wear mechanism. The experimental results show that the surface texturing and the changes in microgrooves can reduce wear. The results indicate, that samples after laser texturing were characterized by 15% higher microhardness, compared to those in the initial state. It was found, a 26% reduction in friction coefficient and 29% in the wear volume compared to the smooth, untextured surface samples under lubricated conditions. The decrease in value of the coefficient friction and wear volume for the samples after the laser texturing process is an effect of synergistic of entrapped wear debris in micro-grooves and increased hardness for samples after laser textured.

Penyelidikan Tanah Menggunakan Metode Uji Sondir Di Universitas 17 Agustus 1945 Surabaya

Cone Penetration Test (CPT) is a method designed to determine and test the strength of soil layers quickly and is one of the most widely used testing methods. The aim of this research is to determine the resulting bearing capacity and determine the hard soil layers on the Padhang-Padhang campus of West Sulawesi University using the Cone Penetration Test (CPT) or Sondir field testing tool. The method used in this research is the literature study method and direct testing in the field. From the results of this test, the Cone Penetration Test (CPT) data from 1 test point was processed and analyzed using Microsoft Excel 2019 software. The results of data processing and analysis were the maximum cone pressure (qc) value and the maximum number of sticking resistances (JHP), namely 650 kg/cm at a depth of 12.60 meters and 2496.00 kg/cm² at a depth of 15.00 meters. The maximum friction ratio (Rf) of 0.11% is at a depth of 14.00 meters, while the maximum Sticking Resistance Pressure (fs) value of 110 kg/cm² is at a depth of 14.00 meters.

Link Between Geometrical and Physical Property Changes Along Nankai Trough With Slow Earthquake Activity Revealed by Dense Reflection Survey

AbstractWe examined the possible factors affecting the spatial distribution of very low frequency earthquakes and tremors in the shallow megathrust of Nankai Trough (&lt;30 km) using a dense network of prestack depth migrated profiles at the frontal wedge. Geometrical parameters examined were decollement roughness, taper angle, and underthrust thickness. Physical properties such as effective basal friction (μb) and pore pressure ratio (λ*) were calculated from the taper angle and p‐wave velocity. Regions of low λ* (0.39 ± 0.08) and smooth decollement showed no slow earthquake activity. In contrast, high activity of slow earthquakes was observed in areas with a rough decollement due to the presence of subducted seamounts or bathymetric highs. The low taper angle (3.8°) off Muroto where slow earthquakes also occur translates to a wide zone of low μb (0.21 ± 0.06) and high λ* (0.66 ± 0.06). However, our results also show that slow earthquakes don't always occur in areas with high λ*.

Earthworm-Inspired Soft Skin Crawling Robot.

Earthworms are fascinating animals capable of crawling and burrowing through various terrains using peristaltic motion and the directional friction response of their epidermis. Anisotropic anchoring governed by tiny appendages on their skin called setae is known to enhance the earthworm's locomotion. A multi-material fabrication technique is employed to produce soft skins with bristles inspired by the earthworm epidermis and their setae. The effect of bristles arranged in triangular and square grids at two spatial densities on the locomotion capability of a simple soft crawling robot comprised of an extending soft actuator covered by the soft skin is investigated experimentally. The results suggest that the presence of bristles results in a rostral to caudal friction ratio of µR/µC > 1 with some variations across bristle arrangements and applied elongations. Doubling the number of bristles increases the robot's speed by a factor of 1.78 for the triangular grid while it is less pronounced for the rectangular grid with a small factor of 1.06. Additionally, it is observed that increasing the actuation stroke for the skin with the high-density triangular grid, from 15% to 30%, elevates the speed from 0.5 to 0.9mms-1, but further increases in stroke to 45% may compromise the durability of the actuators with less gains in speed (1mms-1). Finally, it is demonstrated that a crawling robot equipped with soft skin can traverse both a linear and a curved channel.

Study on the hysteretic characteristics of FRP-reinforced concrete shear wall with innovative friction dampers

FRP-reinforced concrete shear walls (FRCWs) are able to achieve satisfactory residual deformation and corrosion resistance compared with steel reinforced concrete walls (SRCWs). However, in the FRCWs, the failure of the plastic hinge region brings great challenges to the post-earthquake repair of the structure. Therefore, this paper designed one SRCW and two FRCWs with innovative friction dampers (FDs) at the feet, and steel truss and steel plate were embedded at the plastic hinge region of the two FRCWs respectively to supplement the weakened shear strength. Then pseudo-static tests were carried out twice before and after repairing the two FRCWs with FDs. Experimental results showed that compared with the SRCW at the same lateral drift, the damage of the FRCW was reduced by installing FDs at the feet, and the energy dissipation capacity was enhanced; the repaired FRCWs with FDs could still have acceptable seismic performance. Subsequently, the Park-Ang damage indices of wall webs of the FRCWs with FDs were calculated, which proved that the FRCWs with FDs could meet the four-level seismic fortification objective. In the end, two orthogonal tests were designed based on the established OpenSees models to evaluate the impact of the damper friction and FRP reinforcement ratio on the seismic behaviours of the FRCWs with FDs. It was recommended to adopt larger longitudinally distributed FRP reinforcement ratio to obtain satisfactory self-centering ability and hysteresis performance of the FRCW with FDs.

Segregation–rheology feedback in bidisperse granular flows: a coupled Stokes’ problem

The feedback between particle-size segregation and rheology in bidisperse granular flows is studied using the Stokes’ problem configuration. A method of lines scheme is implemented to solve the coupled momentum and segregation equations for a normally graded particle size distributed bulk at constant solids volume fraction. The velocity profiles develop quickly into a transient state, decoupled from segregation yet determined by the particle size. From this transient state, the velocity profile changes due to the particles’ relative movement, which redistributes the frictional response, hence its rheology. Additionally, the particles’ relative friction is modified via a frictional coefficient ratio, by analogy with the particles’ size ratio. While positive values of this coefficient exacerbate the nonlinearity of the velocity profiles induced by size differences, negative values dampen this behaviour. The numerical solutions reproduce well the analytical solutions for the velocity profile, which can be obtained from the steady-state conditions of the momentum and segregation equations for the transient and steady states, respectively. Segregation–momentum balances and four characteristic time scales can be established to propose two non-dimensional quantities, including specific Schmidt and Péclet numbers that describe broadly the segregation–rheology feedback. The proposed scheme, theoretical solutions and non-dimensional numbers offer a combined approach to understand segregation and flow dynamics within a granular bulk, extensible across many flow configurations.

Investigation of the performance of a parabolic trough collector outfitted with annular absorber tubes

The current work recommends a novel absorber tube for parabolic trough solar collectors. Annular absorber tubes with and without spiral tape have been investigated as an alternative to conventional absorber tubes. This work employs numerical analysis through the usage of CFD code. The pitch ratio (P/D), width ratio (W/D), and height ratio (H/D) of the spiral tape are each different. Within the annular absorber tube, these ratios have an impact on the performance of heat transfers, pressure drop, and entropy generation. The results reveal that an annular absorber tube without spiral tape has a higher Nu ratio than a conventional absorber tube. In an annular absorber tube with P/D = 1.4, the Nusselt number increases. In an annular absorber tube, the spiral tape thickness ratio has no effect. The average Nu ratio is 24.5% greater at a height ratio of 0.3 than it would be in an annular absorber tube without spiral tape. The annular absorber tube's spiral tape's pitch ratio, thickness ratio, and height ratio all generate less total entropy than a conventional absorber tube does. The wall temperature of the absorber tube with the lowest spiral tape pitch ratio decreases, which results in a reduction in the thermal stress on the absorber wall. On the other hand, spiral tape and an annular absorber tube have a higher friction ratio. It exceeds the friction ratio of the annular absorber tube without spiral tape by 41.7 times.

Statistical Evaluation of Sleeve Friction to Cone Resistance Ratio in Coarse-Grained Soils

The investigation of soil is a particularly important stage of structural design. Cone penetration tests (CPTs) are the most common soil investigation techniques. The results of these tests provide information about the values of cone resistance (qc) and sleeve friction (fs), which correspond to depth. Previous studies have shown that the ratio of sleeve friction to cone resistance depends on the particle size distribution in soil and its use for soil classification. Unfortunately, as an analysis of the literature shows, there is no such classification for coarse-grained soils. This paper presents statistically significant differences in the ratio of fs to qc in coarse-grained soils. Based on the research performed, the proposed coefficients depend on the classification of coarse-grained soils with respect to the size of the soil particles. The data investigated were obtained from study reports on 35 sites (5934 tests) at which the main type of soil was coarse-grained and contained different sizes of particles. Following a statistical analysis, five groups of tested coarse-grained soils, silty fine sand, clayey fine sand, fine sand, medium sand and gravelly coarse sand together with gravel, are derived. The analysed data show statistically significant differences in the ratio of fs to qc considering this particular type of soil. A ratio of fs to qc with a probability of 95% is proposed for sandy soils. The values for silty fine sand, clayey fine sand, fine sand, medium sand and gravelly coarse sand mixed with gravel are 0.009459, 0.010982, 0.009268, 0.008001 and 0.006741, respectively. A linear relationship between the fs and qc indexes is also suggested.

Mechanism Design and Motion Planning of a Hexapod Curling Robot Exhibited During the Beijing 2022 Winter Olympics Games

When a curling rock slides on an ice sheet with an initial rotation, a lateral movement occurs, which is known as the curling phenomenon. The force of friction between the curling rock and the ice sheet changes continually with changes in the environment; thus, the sport of curling requires great skill and experience. The throwing of the curling rock is a great challenge in robot design and control, and existing curling robots usually adopt a combination scheme of a wheel chassis and gripper that differs significantly from human throwing movements. A hexapod curling robot that imitates human kicking, sliding, pushing, and curling rock rotating was designed and manufactured by our group, and completed a perfect show during the Beijing 2022 Winter Olympics Games. Smooth switching between the walking and throwing tasks is realized by the robot’s morphology transformation based on leg configuration switching. The robot’s controlling parameters, which include the kicking velocity vk, pushing velocity vp, orientation angle θc, and rotation velocity ω, are determined by aiming and sliding models according to the estimated equivalent friction coefficient μequ and ratio e of the front and back frictions. The stable errors between the target and actual stopping points converge to 0.2 and 1.105 m in the simulations and experiments, respectively, and the error shown in the experiments is close to that of a well-trained wheelchair curling athlete. This robot holds promise for helping ice-makers rectify ice sheet friction or assisting in athlete training.

Determining The Depth of Hard Soil Layers Using Geoelectric Resistivity and Cone Penetration Test Methods (Case Study: Kelurahan Bontoramba Kecamatan Somba Opu Kabupaten Gowa)

Hard soil layers can impact the loading, stability, and behavior of structures in the geotechnical field. Comprehensive understanding of the depth and properties of hard soil layers can aid in designing suitable structures. Therefore, this study employed the resistivity geoelectric and Cone Penetration Test (CPT) methods to map the features of hard soil layers. Resistivity data were acquired through measurements utilizing the geoelectric method, while data on cone resistance, shear resistance, and friction ratio were gathered through field measurements using the CPT tool. The collected data was analyzed comprehensively to obtain a complete understanding of soil conditions. Based on resistivity values, the results indicated the research site comprises alluvium, very dry clay, and dry sandy soil. Based on the CPT test, it is determined that the layers contain mixtures of fine-grained soils, clay, silt, and sand. Therefore, it can be inferred that the dense sand lithology constitutes the hard soil layer geologically. The employment of both approaches delivers supplementary details on soil features and depth.

Numerical analysis of the dependence of damage on friction during deep drawing of asymmetric geometries

The manufacturing of three-dimensional sheet metal components, such as car body parts, heavily relies on deep drawing. With the increasing demand for lightweight measures in the automotive industry due to CO2 limitation requirements, various methods are currently employed to reduce the weight of deep drawn components. However, these methods often overlook the potential for influencing the stress-strain dependent damage state within the component, even though it can greatly affect its performance in subsequent applications, and thus offers lightweight potentials. Friction between the deep drawing tools and the sheet metal is a key factor influencing the stress-strain state, and hence, represents a lever that can be utilized to manipulate the damage state in the component. This paper focuses on the numerical analysis of the dependence of damage on friction during deep drawing. Therefore, a rectangular geometry with an asymmetrical material flow is numerically investigated. A friction ratio is introduced with different constant friction coefficients for the corner of the tools and the straight sides. The established load paths at a chosen reference point are then considered in the form of selected stress and strain characteristics and the numerically predicted damage state is compared. The results are used to derive a recommended friction ratio that leads to less damage in the corner of the geometry. Afterwards strip drawing tool surfaces are modified to manipulate their friction properties using machine hammer peening. Subsequently, the influence of the structures of the strip drawing tool surfaces is quantified using strip drawing tests. The identified contact normal stress dependent friction coefficients are then implemented in the numerical simulation and the established numerical predicted damage state is examined to gain a more comprehensive understanding of how the friction ratio and the structure of the tool surfaces influence the damage state.

Natural state parameter for sand

Based on the frictional state concept, the natural state parameter for sands is defined as an extension of the state parameter defined by Been and Jefferies. The proposed definition of the natural state parameter is the sum of the distance between the normalised difference of the current stress ratio and the critical frictional stress ratio and the difference between the current and critical frictional state void ratio for the same mean principal stress. Therefore, it combines the difference between the current and critical frictional state in the q ‒ p’ and e ‒ p’ planes and can be treated as an extension of Been and Jefferies’ definition of the state parameter in the e ‒ p’ plane. The results of drained triaxial compression tests for Toyoura sand and Dog’s Bay sand, presented in the literature, are analysed. The values of the natural state parameter at failure for these sands are equal to zero. Therefore, the critical state in the q ‒ p’ and e ‒ p’ planes can be determined by analysing the conditions at failure. At failure, the deformations of the samples are almost homogeneous, and the stresses and deformations (void ratios) can be correctly determined. Additionally, the critical frictional state and critical state are very similar for these sands. The relationship between the dilatancy and the state parameter at failure, similar to that given by Been and Jefferies, was obtained directly by using the frictional state concept and the proposed definition of the natural state parameter. The natural state parameter, like the state parameter, can be used for modelling of sands in the future.

Prediction of energy dissipation by analytical solution to combined viscous and Coulomb damping

Damping in mechanical vibration systems primarily falls under (i) linear viscous and (ii) non-linear Coulomb damping. Practically, most systems possess characteristics of both linear viscous and non-linear Coulomb damping. In this work, the method of phase space coordinate averaging is used to obtain an approximate analytical solution for the system’s response when it is subjected to both viscous and Coulomb damping. The accuracy of the proposed solution is examined by comparing it with the numerical simulations and experimental results. The energy dissipated by both damping mechanisms is quantified using semi-analytical integrals. The analysis of energy dissipation quantifies the conditions for natural frequency, damping ratio, and coefficient of friction, at which the energy dissipated by viscous damping is equal to the energy dissipated by Coulomb damping. This has led to the introduction of a non-dimensional quantity called the dissipation number (D). With certainty, it can be stated that if D>1, friction is dominant, and if D<1, viscosity is dominant.

Enhancing journal bearing performance through surface texturing: A comprehensive review of latest developments and future prospects

Incorporating surface textures on the contact points substantially improve bearing performances, which is evident from burgeoning interest in this field. This study thoroughly reviews existing literature on the topic from its inception to date. We have carried out an assiduous examination of various surface microcavities to assess how well they perform in terms of load-bearing capacity, friction coefficient, and friction force. The study briefly dwells upon numerical modeling techniques and their advantages and limitations. Further, this study develops a quantitative understanding of the impact of four textures including Pocket, Line, Cross, and Dot-like texture on the bearing parameters such as coefficient of friction, film thickness, and convergence ratio at the inlet and exit. The study elucidates how various surface textured designs would affect the way a hydrodynamic journal bearing functions . The present study also examines the texture roughness pattern transverse and longitudinal sinusoidal, full, and half-wave and its influence on the hydrodynamic journal bearing performance. The study gets concluded with the finding that in the case of pocket texture, the coefficient of friction is reduced by up to 20%. Transverse and longitudinal positive full wave texture pattern increase load-bearing capacity by up to 34% and reduces friction coefficient by up to 18%.

Estimating geotechnical parameters using semisupervised learning: An example from the Dutch offshore wind farm zone

Wind energy is considered to be of great importance for promoting energy transition and achieving net-zero carbon emission. Reliable modeling and monitoring of the near-subsurface geology are crucial for successful wind farm selection, construction, operation, and maintenance. For optimal characterization of shallow seafloor sediments, 2D ultrahigh-resolution (UHR) seismic survey and 1D cone-penetration testing (CPT) often are acquired, processed, interpreted, and integrated for building 3D ground models of essential geotechnical parameters such as friction. Such a task faces multiple challenges, such as limited CPT availability, strong noise contamination in UHR seismic data, and heavy manual efforts for completing the traditional workflows, particularly acoustic impedance inversion. This study accelerates the integration by a semisupervised learning workflow with three highlights. First, it enables geotechnical parameter estimation directly from UHR seismic data without impedance inversion. The second comes from the use of a pretrained feature engine to reduce the risk of overfitting while mapping massive UHR seismic data with sparse CPT measurements through deep learning. More importantly, it allows incorporating other geologic/geophysical information, such as a predefined structural model, to further constrain the machine learning and boost its generalization capability. Its values are validated through applications to the Dutch wind farm zone for estimating four geotechnical parameters, including cone-tip resistance, sleeve friction, pore-water pressure, and the derived friction ratio, in two example scenarios: (1) UHR seismic data only and (2) UHR seismic data and an 11-layer structural model. The results verify the feasibility of data-driven geotechnical parameter estimation. In addition to the two demonstrated scenarios, our workflow can be further customized for embedding more constraints, e.g., prestack seismic and elastic/static property models, given their availability in a wind farm of interest.