Cone Penetration Test Research Articles

Determination of Constrained Modulus of Granular Soil from In Situ Tests—Part 2 Application

The paper demonstrates how the concepts presented in the companion paper: “Determination of Constrained Modulus of Granular Soil from In Situ Tests—Part 1 Analyses” can be applied in practice. A settlement design based on the tangent modulus method is described. Extensive in situ tests were performed on a well-documented test site consisting of sand with silt and clay layers. The field tests comprised different types of penetration tests, such as the cone penetration test, the flat dilatometer, and the seismic down-hole test. The modulus number and the constrained tangent modulus were derived from the cone penetration test with pore water pressure measurement and the flat dilatometer test. In addition, the shear wave speed was determined from two seismic down-hole tests, from which the small-strain shear modulus could be evaluated. The constrained modulus obtained from the cone penetration test with pore water pressure measurement (CPTU) and the flat dilatometer (DMT) was compared with that from the seismic down-hole tests. The importance of the stress history on the constrained modulus was demonstrated. The range of modulus numbers, derived from different in situ tests, compares favorably with empirical values reported in the literature.

A Critical Review of Cone Penetration Test-Based Correlations for Estimating Small-Strain Shear Modulus in North Sea Soils

The geotechnical characterisation of offshore wind farm sites requires measurement or estimation of the small-strain shear stiffness Gmax of the subsoil. This parameter can be derived from shear wave velocity Vs measurements if the bulk density of the soil is known. Since direct measurements of Vs are generally not available at all foundation locations in a wind farm, correlations with cone penetration test (CPT) results are often used to determine location-specific stiffness parameters for foundation design. Existing correlations have mostly been calibrated to onshore datasets which may not contain the same soil types and stress conditions found in the North Sea. The distinct geological history of the North Sea necessitates a critical review of these existing CPT-based correlations. They are evaluated against an extensive database of in situ Vs measurements in the southern North Sea. The importance of modelling the stress-dependent nature of Vs is highlighted, and a novel stress-dependent model for Vs from CPT data, which leads to an improved fit, is presented. As the small-strain stiffness is used as an input to foundation response calculations, the model uncertainty of the correlation can introduce significant uncertainty into the resulting foundation response. This transformation uncertainty is quantified for each of the correlations evaluated in this study and shows important variations.

Analysis of pile end bearing capacity in Holocene interlayered silty deposits based on CPT soil behavior type index

The existing correlations between pile and cone penetration test (CPT) results often lack versatility for silty geomaterials, as they were primarily developed for clays or sands. To establish meaningful correlations, it is essential to understand the geology of the environment under examination. The CPT and its derived parameters, including the Soil Behavior Type (SBT) index, have proven to provide reliable soil information, particularly in the field of pile foundation engineering. This paper presents the findings and interpretations from several pile load tests conducted alongside field cone penetration tests on a Holocene saline interlayered silty formation, a distinct condition encountered in practice. Various CPT-based pile design methods were employed to evaluate pile capacity based on CPT results. As observed, predictions for pile shaft resistance in this geological formation remained consistent across all methods, while notable variations emerged in estimating pile end bearing. This was inferred to be a result of limited research on pile end bearing capacity in the literature, leading to proposals of broad ranges for pile influence zone and toe coefficient values, as well as various CPT tip resistance averaging techniques across different methods. Consequently, to improve accuracy, modifications based on site-specific test data may be necessary. Drawing from the assessments, effective modifications involved considering the SBT index near the pile tip. Subsequently, the current study introduces a new region-specific adjustment to the widely recognized Enhanced Unicone method based on the SBT index, resulting in a more accurate estimate of pile end bearing in such interlayered silty contexts, with less scatter compared to other available approaches.

Evaluating the Characteristics of Spatial Variability of Soil in Vertical Direction Highly Heterogeneous Region Based on Cone Penetration Test

Abstract Key parameters describing the spatial variability of soil properties based on the random field theory are the scale of fluctuation (SOF) and coefficient of variation (COV). To characterize the spatial variability of soil properties, reducing the impact of these errors and uncertainties is necessary. To accomplish this, for the five main layers of soil, we collected 18 cone penetration test (CPT) data from a highly heterogeneous region in Lianyungang New Airport, Jiangsu Province, China, and used the control variable method to analyze the influence of the estimation method of tendency, its function type and outliers. The results show that, compared with the ordinary least square method (OLSM), the least absolute deviation method (LADM) can more truly reflect the trend component of CPT parameters in the vertical direction, and the influence of other factors on SOF and COV is also studied, such as outliers and estimation functions of trend components. On this basis, a reasonable calculation process of SOF and COV is summarized, which provides a reference for the calculation of SOF and COV in vertical direction in the future. By comparing the SOF calculated by different models, the results show that the squared exponential (SQX) model has the highest SOF in 68.3% of the evaluation, and the single exponential (SNX) model has the lowest SOF in 64.4% of the evaluation. Moreover, we compared the SOF and COV of cone tip resistance (qc) and sleeve friction (fs), which showed that SOF of qc and COV of qc is lower than that of fs in 54.4 and 73.3% of all evaluations, respectively.

Liquefaction hazard of Wellington reclamations based on conventional analysis

Severe liquefaction-induced damage occurred in reclamation fills at the port of Wellington (CentrePort) in the 2016 Kaikōura earthquake, but little or no damage was reported in areas of older and shallower reclamations in central Wellington. Recent studies have therefore primarily focused on understanding the liquefaction hazard of the port, while little is still understood with regards to the fill characteristics and liquefaction potential of the Wellington reclamations outside CentrePort. This study utilizes data from comprehensive field investigations, including 58 new cone penetration tests (CPTs) performed both within and outside the port in the Wellington waterfront area, supplemented with over 100 CPTs from our previous studies at CentrePort, to characterize the liquefaction resistance of the reclaimed fills in Wellington. The geotechnical data is first used to define simplified schematic soil profiles and to determine characteristic CPT parameter values (25th–50th–75th percentiles) for fills encountered in different reclamation areas. These analyses highlight differences in the soil profiles, and the relative similarity in the estimate of liquefaction resistance based on conventional CPT-based assessment, of fills encountered in different reclamation areas despite differences in the age, techniques, and materials employed in the construction of these reclamations. Conventional liquefaction assessments of reclamation fills based on CPT data are then performed over the wider waterfront area for a range of earthquake scenarios and ground motion intensities relevant for Wellington. For recent, past earthquakes, correspondence between predicted and observed severity of the manifestations of liquefaction vary depending on the earthquake event and area of observations. Likelihood of liquefaction occurrence and severity of the effects of liquefaction are then discussed for characteristic return periods, in the context of the seismic hazard of Wellington.

Cone penetration tests and dynamic soil properties

Cone penetration tests and dynamic soil properties

A method for estimating coefficient of lateral earth pressure based on cone penetration tests

The coefficient of lateral earth pressure at rest (K0) is a key state soil variable for the design of foundations and underground structures, characterizes in-situ stress state and soil condition. In this study, a method for the in-situ estimation of K0 using the cone penetration test (CPT) is proposed considering vertical and inclined cone resistances (qc). For this purpose, a series of laboratory CPTs in a soil chamber were conducted to obtain and characterize vertical and inclined qc values at various inclination angles (θ) and relative densities (DR). It was observed that the values of qc increased as θ increased, which was more pronounced at higher DR. Coupled Eulerian-Lagrangian (CEL) finite element analyses were performed to quantify the values of inclined qc at various cone penetration and soil conditions. Based on results from laboratory CPTs and CEL analyses, a CPT-based K0 correlation model was established, which was given as a function of vertical and inclined qc values. The model parameter for the proposed method was evaluated and quantified. The validity of the proposed method was confirmed from the comparison with case examples.

Explainable AI models for predicting liquefaction-induced lateral spreading

Introduction: Earthquake-induced liquefaction can cause substantial lateral spreading, posing threats to infrastructure. Machine learning (ML) can improve lateral spreading prediction models by capturing complex soil characteristics and site conditions. However, the “black box” nature of ML models can hinder their adoption in critical decision-making.Method: This study addresses this limitation by using SHapley Additive exPlanations (SHAP) to interpret an eXtreme Gradient Boosting (XGB) model for lateral spreading prediction, trained on data from the 2011 Christchurch Earthquake.Result: SHAP analysis reveals the factors driving the model's predictions, enhancing transparency and allowing for comparison with established engineering knowledge. Notably, the SHAP values expose an unexpected behavior in the PGA feature. Moreover, the results demonstrate that the XGB model successfully identifies the importance of soil characteristics derived from Cone Penetration Test (CPT) data in predicting lateral spreading, validating its alignment with domain understanding.Discussion: This work highlights the value of explainable machine learning for reliable and informed decision-making in geotechnical engineering and hazard assessment.

Investigation and analysis of the macro- and micro-responses of bentonite-sand mixtures to temperature

Bentonite-sand mixture has been proposed as a buffer material of high-level radioactive waste (HLW) repositories in many countries. The elevated temperature in HLW repositories significantly influences the properties and behaviour of the surrounding buffers. However, to date the mechanism of temperature effects on the behaviour of the bentonite buffer is not well understood. This study is aimed at clarifying the macro- and micro-responses of bentonite-sand mixtures by conducting cone penetration test, rheometer test, flask volumetric test, scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) at different temperatures. The results from macro-experiments show that the liquid limit and yield stress increased while bound water content decreased with increasing temperature. The normalized relationships disclose the sand content dramatically affects the degree of temperature influence on the macro-behaviour. SEM and MIP results present that the contact manner between particles converted from edge-to-face to the edge-to-edge association and some intra-aggregate pores merged to form inter-aggregate pores as temperature increases. The mechanisms of the increasing temperature influence on the responses of bentonite-sand mixtures can be inferred that: 1) the diffuse double layer is supposed to decrease since more ions were electrolyzed from montmorillonite particles, thereby, increasing the ion concentration and changing the ion valence; 2) the slight shrinkage of diffuse double layer produced nano-fissures, causing water-hold capacity to increase; 3) the temperature-induced transition from bound water into free water results in an increase of liquid volume; 4) increasing temperature led to increased inter-particle repulsive force. Furthermore, an empirical model was proposed to predict the yield stress of bentonite dispersion incorporating the combined effects of sand content and temperature.

РІЗНІ ПРАКТИКИ ОЦІНЮВАННЯ МІЦНОСТІ ШАРІВ ҐРУНТОВОЇ ОСНОВИ І ДИСПЕРСНИХ МАТЕРІАЛІВ ЗА РЕЗУЛЬТАТАМИ ДИНАМІЧНОГО ВИПРОБУВАННЯ КОНУСНИМ ПЕНЕТРОМЕТРОМ

Introduction. The introduction to the paper highlights the methods of standard geotechnical tests for in situ measurements of subgrade strength or strength estimation. Problem statement. The issue of the paper concerns the interpretation and the application of the results of testing of the subgrades or granular layers of a road pavement by the dynamic cone penetrometer. Purpose. The goal of the paper consists of the analysis of practices of the subgrade strength evaluation by the conversion of the dynamic cone penetration test (DCPT) results to the nominal values of the California bearing ratio (CBR) or by plotting the subgrade profile and also of practices for the layer thickness evaluation and compaction control. Results. The main principles of DCPT were reviewed with performing the analysis of factors affecting the test results. The equations of the dependence of the nominal CBR values on the penetration index as the main result of DCPT was analyzed. The assumption was made that the difference in such equations may be determined by the differed confinement conditions under testing in accordance with which the calculated values provided by the results of testing under the triaxial confinement are higher. Also the stair-stepping effect appeared when performing DCPT on cohesive soils was reviewed.

Utilizing Machine Learning for Cone Penetration Test-Based Soil Classification

The cone penetration test (CPT) is widely used in geotechnical engineering to assess soil properties. Traditional methods of interpreting CPT data and classifying soils have limitations and are time-consuming. Machine learning (ML) algorithms offer a data-driven approach to automate and improve soil classification based on CPT data. In this study, the applicability of ML techniques was investigated to measure the reliability of soil classification prediction using raw CPT data. A dataset comprising raw CPT data and corresponding soil classifications derived from the adjacent boreholes was prepared for training and testing the selected ML techniques. Five ML algorithms, namely logistic regression, the support vector machine, the random forest (RF), K-nearest neighbors (KNN), and extreme gradient boosting (XGBoost), were applied. The results showed that the RF algorithm outperformed other ML methods, achieving an F1-score of 0.896. Comparing the performance of different algorithms, the RF consistently showed the best results, followed by XGBoost and KNN. These findings highlight the potential of ML algorithms, particularly the RF, in accurately predicting soil classification based on CPT data, thus improving the efficiency and reliability of geotechnical engineering applications.

Analisa Prediksi Potensi Likuifaksi di Kota Rengat Kabupaten Indragiri Hulu

The number of incidents occurring on the island of Sumatra, especially West Sumatera and Jambi provinces that affect the vibration of the earthquake in Rengat City on a large scale can lead to the movement of land such as landslides and stagnant ground water sources can lead to liquefaction. The purpose of this research is to know how the arrangement of soil type at research location Rengat City and to know the location reviewed in Rengat City, and its surrounding experience potential liquefaction based on some existing penetration test data. This research was conducted to predict liquefaction potential that occurred in Rengat City of Indragiri Hulu Regency with secondary data of penetration test of konus with Seed and Idriss method (1971). The calculation of potential liquefaction prediction is done by determining the number of soil layers, estimating the weight of the soil volume, determining the soil overburden, determining the effective soil stress, determining the corrected confront resistance, calculating Cyclic Strees Ratio (CSR), calculating Cyclic Resistance Ratio (CRR). After calculating the value of Magnitude Scalling Factor (MSF) and calculating the value of safe factor by comparing the value of Cyclic Strees Ratio (CSR) with Cyclic Resistance Ratio (CRR) if the calculation <1 factor is safe then potentially liquefaction occurs. Based on the results of the analysis of the 7 locations with a total of 2 cone penetration test conus analyzed in this study in Rengat City, obtained the type of soil structure is not uniform and based on the results of analysis, from the 7 research sites with tottal 21 point penetration test konus reviewed at magnitude 5 to 10 in Rengat City Indragiri Hulu Regency. In the type of sand soil in the dominant study area can not be achieved liquefaction, this is reinforced from the calculation (SF)> 1 safe factor (SF: 1.0).

Distributed acoustic sensing for seismic surface wave data acquisition in an intertidal environment

The application of distributed acoustic sensing (DAS) for shallow marine seismic investigations is assessed, in particular with respect to the collection of seismic surface wave data in an intertidal setting. Appropriate selection and directional sensitivity of fiber-optic cables is considered and the measured data is validated with respect to conventional seismic data acquisition approaches, using geophones and hydrophones, along with independent borehole and seismic cone penetration test (SCPT) data. In terms of cable selection, a reduction in amplitude and frequency response of an armored cable is observed, when compared with an unarmored cable. For seismic surface wave surveys in an offshore environment where the cable would need to withstand significant stresses, the use of the armored variant with limited loss in frequency response may be acceptable from a practical perspective. The DAS approach also has indicated good consistency with conventional means of surface wave data acquisition, and the inverted [Formula: see text] also is very consistent with downhole SCPT data. Observed differences in phase velocity between high tide (Scholte wave propagation) and low tide (Rayleigh wave propagation) are not thought to be related to the particular type of interface wave due to shallow water depth. These differences are more likely to be related to the development of capillary forces in the partially saturated granular medium at low tide. Overall, this study demonstrates that our novel approach of DAS using seabed fiber-optic cables in the intertidal environment is capable of rapidly providing near-surface S-wave velocity data across considerable spatial scales (multikilometer) at high resolution, which is beneficial for the design of subsea cables routes and landfall locations. The associated reduction in deployment and survey duration, when compared with conventional approaches, is particularly important when working in the marine environment due to potentially short weather windows and expensive downtime.

CPT calibration chamber testing on tailings

The cone penetration test (CPT) is a widely used technique for on-site investigations. In the field, interpretation correlations of CPT can be established using laboratory calibration chamber tests. Empirical and theoretical correlations were developed for clay and sand under undrained and drained conditions, respectively. However, interpreting these results can be more challenging for intermediate soils that exhibit partial drainage during penetration and lie between fully undrained and drained conditions. Tailings, which are the by-products of mining and are often rich in fine particles, are a typical example of such intermediate soils. To gain a deeper understanding of the behavior of the tailings during CPT, a calibration chamber test was performed at a standard rate of 2 cm/s and subsequently at a slow rate of 0.02 cm/s, and the obtained results were analyzed.

Soil classification based on unsupervised learning using cone penetration test data

Borehole data obtained during geological surveys are the most essential source for understanding soil stratification. It is a prerequisite to know the soil classes up to some depths prior to any construction. However, the direct method to identify the soil classes by drilling boreholes and testing soil samples is costly. A cost-effective alternative is the Cone Penetration Testing (CPT), which is one of the most popular soil investigation methods. This paper explores the intelligent classification of soil layers based on CPT data using three unsupervised machine learning methods: K-means, Gaussian Mixture Process, and BIRCH. The research investigates the classification performance of different models in scenarios with 2 combinations, 3 combinations, 4 combinations, and 5 combinations. The results indicate that the Gaussian Mixture Process method exhibits the best classification performance, followed by the BIRCH method, while K-means performs relatively poorly. Using unsupervised learning for intelligent soil layer classification offers a fast and clear process, but the accuracy still requires further improvement. This study provides a valuable reference for future soil classification studies.

Application of PISA method for monopile design in layered soil

The foundation design for offshore wind turbines (OWTs) is critical to ensuring their structural integrity and long-term stability. Large-diameter monopiles are widely used for OWTs owing to their proven effectiveness. The conventional design approach, derived from the oil and gas industry’s p-y model, has limitations when applied to monopiles for OWTs. Consequently, a novel design method based on the PISA joint industry research project was developed, which extends beyond the traditional lateral soil resistance (p-y curves) and incorporates additional soil reaction components from shaft friction, pile base shear, and base moment. Unlike the simplistic rule-based conventional approaches, the proposed method necessitates site-specific 3D finite element (FE) simulations for precise calibration of soil reaction curves. Although successfully applied in European offshore wind farms, the PISA method’s performance in regions with distinct seabed compositions, such as China, remains to be verified. Therefore, this paper presents a comprehensive case study conducted at the Xiangshan wind farm, a representative site characterized by layered soil. The study employed in-situ investigations (cone penetration test, borehole) and laboratory tests (direct simple shear, bender element) to delineate the seabed soil profile and derive essential soil parameters for accurate foundation design. To facilitate the design, an Abaqus-based design tool was developed, which automated the extraction of soil reaction curves from the 3D FE simulations, calibration of PISA springs, and execution of one-dimensional beam-spring analyses employing Timoshenko beam theory. Comparative analyses were performed on the computed responses of piles, encompassing load-deflection curves, pile deflections, and bending moment profiles. The outcomes from the 3D FE simulations, uncalibrated rule-based PISA model, and calibrated PISA model were compared to validate the PISA method for monopile design in layered soil conditions.

Similarity Solutions for Spherical Cavity Expansion in Strain-Softening Soils and its Application in Cone Penetration Test

The cavity expansion theory is commonly employed to predict the grouting pressure and cone penetration resistance. However, existing theoretical solutions for cohesive-frictional soils with dilation fail to simultaneously consider both the elastic deformation in the plastic zone and strain-softening behaviour of soils. To address this limitation, a similarity solution was derived for the expansion of spherical cavities from a zero initial radius with an initial confining pressure in strain-softening Mohr–Coulomb materials. The results demonstrate good agreement with previous theories, predicting an ultimate pressure higher than that obtained by neglecting elastic deformation in the plastic zone but lower than that calculated by neglecting softening characteristics. Moreover, several influential factors affecting the radius of the plastic zone and ultimate pressure were meticulously examined. On-site cone penetration test data and the theoretical results showed notable agreement. This indicates that the proposed solution exhibits a better conformance with the field data than do the previous solutions.

Small-strain characterization of Shanghai clays by triaxial compression tests

The mechanical properties of the upper Shanghai Layers 2-6 clays at small strain levels have been extensively investigated. Nonetheless, limited data exist on their small-strain characteristics through K 0-consolidated undrained triaxial compression tests, with even less information available for the deeper layers 8 and 10. This study employed a series of K 0-consolidated undrained TC tests on intact samples from both the upper layers 2-6 and the deeper layers 8 and 10 of Shanghai clay. We evaluated the undrained maximum secant stiffness (Eu max) and reference shear strain (γ0.7 ). An increase in over-consolidation ratio (OCR) results in a higher E u max/p’ and a more rapid decay of the G/G max with the increasing shear strain (γ). As the value of γ 0.7 increases with I p and decreases with OCR, a correlation between γ 0.7 and Ip can be established. This study observed significant correlations between the E u max, effective stress (p’), and the maximum deviatoric stress, as well as between E u max and the cone resistance obtained from field cone penetration tests. These correlations offer methods to estimate E u max and γ0.7 values based on parameters that are more readily measurable, which provide critical references for the calculations and design parameters in foundation engineering within the Shanghai region.

Coupled pore pressure analysis of cone penetration test in two-layered clay

PurposeThe paper aims to clarify the distribution of excess pore pressure during cone penetration in two-layered clay and its influence on penetrometer resistance.Design/methodology/approachAn arbitrary Lagrangian–Eulerian scheme is adopted to preserve the quality of mesh throughout the numerical simulation. Simplified methods of layered penetration and coupled pore pressure analysis of cone penetration have been proposed and verified by previous studies. The investigation is then extended by the present work to study the cone penetration test in a two-layered clay profile assumed to be homogeneous with the modified Cam clay model.FindingsThe reduction of the range of pore pressure with decreasing PF will cause a decrease of the sensing distance. The PF of the underlying soil is one of the factors that determine the development distance. The interface can be obtained by taking the position of the maximum curvature of the penetrometer resistance curve in the case of stiff clay overlying soft clay. In the case of soft clay overlying stiff clay, the interface locates at the maximum curvature of the penetrometer resistance curve above about 1.6D.Research limitations/implicationsThe cone penetration analyses in this paper are conducted assuming smooth soil-cone contact.Originality/valueA simplified method based on ALE in Abaqus/Explicit is proposed for layered penetration, which solves the problem of mesh distortion at the interface between two materials. The stiffness equivalent method is also proposed to couple pore pressure during cone penetration, which achieves efficient coupling of pore water pressure in large deformations.

Softening-based interface model and nonlinear load-settlement response analysis of piles in saturated and unsaturated multi-layered soils

This work presents a simplified method for the nonlinear analysis of the load–displacement response of piles in multi-layered soils. As a starting step, a new interface model based on the disturbed state concept (DSC) is put forth to simulate the interface shear stress-displacement relationship by considering the nonlinear hardening–softening behaviour. In the new model, input parameters can be conveniently calibrated using conventional interface shear tests or on-site tests. The good agreement between predictions and experimental data from interface direct shear tests validated the performance of the proposed DSC model. The DSC model performed better in terms of predictions when compared to the hyperbolic one. Next, the soil-structure interface model and bearing capacity theory are coupled to provide a theoretical framework for the analysis of pile load-transfer in saturated and unsaturated multi-layered soils, where the DSC model is employed to represent base resistance as well as skin friction. This work also discusses the profile of steady-state in-situ matric suction, soil–water characteristic curve, and pore-water pressure of unsaturated soils. The proposed method has the advantage of being used in practice as it is simple to obtain input parameters from laboratory tests, as well as Standard Penetration or Cone Penetration Tests. The proposed framework is finally applied to the analysis of five well-documentedcase studies. The proposed approach and the static load test results from the field measurements are found to be in satisfactory agreement, indicating that the proposed method performs well. The proposed method is suggested to be utilised for preliminary analysis, planning a suitable programme of loading tests, as well as optimizing the pile design by back analysis ofthe load test results.