Piezocone Penetration Test Research Articles

Bearing capacity of constrained grouting expansion bored pile based on CPTU and expansion tests

Bored Pile of Constrained Grouting Expansion (BPCGE) is a new type of pile that combines grouting, compression, and expansion technologies. However, there is still insufficient understanding of its bearing characteristics and strength degradation, especially when the surrounding mass is located in soft cohesive soil layers. To address the issues mentioned above, analysis of bearing capacity and strength assessment of BPCGE based on piezocone penetration test (CPTU) and expansion tests are taken into account. Firstly, based on the similarity between the pile prototypes and models, constrained grouting expansion tests are conducted to study the borehole expansion and soil consolidation effects, and analyze the influence on effective stress of soil around the pile and stress relaxation characteristics of cohesive soil. Secondly, CPTU tests and numerical simulations were carried out to investigate the size effect of BPCGE, and a conversion relationship between lateral friction resistance of pile and CPTU friction resistance was established. Finally, the ultimate bearing capacity of BPCGE is proposed. In an application of a high-rise residential project, the calculation method based on CPTU data can effectively predict the ultimate bearing capacity of BPCGE, saving 262 ordinary piles.

A numerical study of deep excavations adjacent to existing tunnels: Integrating CPTU and SDMT to calibrate soil constitutive model

Accurate determination of parameters for an advanced soil constitutive model highly relies on laboratory testing, even though it is notoriously difficult to obtain undisturbed samples for soft soils. This study explores the potential use of in-situ tests, such as piezocone penetration tests (CPTU) and seismic dilatometer tests (SDMT), to estimate the constitutive model parameters. Based on a case history of a deep excavation adjacent to existing tunnels in silt/sand-dominated sediments, a calibration approach of a set of the HSSmall (Hardening Soil Model with Small Strain Stiffness) model parameters is presented, and the derived parameters are used to numerically compute the interactive responses of tunnels and deep excavations. Several comparisons against field monitoring data indicate that the numerical model with the CPTU/SDMT-interpreted HSSmall model parameters adequately reproduces observed deformation responses of deep excavations adjacent to tunnels. However, the use of laboratory tests with disturbed samples to estimate the stiffness parameters of the HSSmall model may lead to an overconservative solution. This finding supports the use of CPTU/SDMT to provide representative parameters for a range of soil layers, leading to the conclusion that tunnel linings may be beneficial to mitigate ground movements and wall deflections due to a barrier effect.

Characterisation of the spatial variability of underconsolidated Singapore Marine Clay using random field theory

ABSTRACT This paper characterised the spatial variability of Singapore Kallang Formation Marine Clays using piezocone penetration test (CPT) data from the Marina South area. Both vertical and horizontal scales of fluctuation in undrained shear strength for two distinct clay units, Upper Marine Clay (UMC) and Lower Marine Clay (LMC), are calibrated for autocorrelation and semi-variogram functions. The Marina South area was reclaimed from the sea using fills placed in three phases from 1970s to 1990s and remains underconsolidated up to date. This study identified variations in the degree of consolidation across the area, which has led to variations in the undrained shear strength in this area. However, the variations in the degree of consolidation were found to have no noticeable influence on the vertical and horizontal scales of fluctuation of either UMC or LMC unit. The vertical scales of fluctuation of UMC and LMC units are 0.57 ± 0.3 m and 0.48 ± 0.17 m , respectively, while the horizontal scales of fluctuations are 148 ± 26 m and 138 ± 28 m , respectively. The present study contributes to the database of the statistical and spatial variability of marine clays and can provide useful guidance for assessing reliability of excavations and foundations in Marina South as well as other areas with similar geological settings.

Improving the interpretation of undrained shear strength from piezocone penetration tests by integrating soil physical properties using a hybrid meta-heuristic algorithm

Conventional empirical equations for estimating undrained shear strength (su) from piezocone penetration test (CPTu) data, without incorporating soil physical properties, often lack the accuracy and robustness required for geotechnical site investigations. This study introduces a hybrid virus colony search (VCS) algorithm that integrates the standard VCS algorithm with a mutation-based search mechanism to develop high-performance XGBoost learning models to address this limitation. A dataset of 372 seismic CPTu and corresponding soil physical properties data from 26 geotechnical projects in Jiangsu Province, China, was collected for model development. Comparative evaluations demonstrate that the proposed hybrid VCS-XGBoost model exhibits superior performance compared to standard meta-heuristic algorithm-based XGBoost models. The results highlight that the consideration of soil physical properties significantly improves the predictive accuracy of su, emphasizing the importance of considering additional soil information beyond CPTu data for accurate su estimation.

Physical property of MICP-treated calcareous sand under seawater conditions by CPTU

MICP (Microbially induced calcite precipitation), an environmentally friendly soil improvement technique, has great potential in ocean engineering due to its ability to promote the precipitation of calcium carbonate through microbial activity to enhance the engineering properties of geomaterials. In this study, piezocone penetration test (CPTU) is used to evaluate the effectiveness of MICP treatment in calcareous sand. The change of physical properties (relative density Dr and total unit weight γt) of MICP treated calcareous sand is investigated by conducting CPTU on the geomaterials prepared in a series of mini calibration chambers (25 cm × 50 cm). Results indicate that CPTU (tip stress, sleeve friction, and porewater pressure) measurements can be used to interpret the physical characteristics of calcareous sand treated with MICP under seawater conditions. Additionally, a relationship between CPTU measurements, physical parameters (relative density Dr and total unit weight γt) of MICP treated calcareous sand is proposed and calibrated. The findings of the research extend the implementation of in-situ testing techniques such as CPTU towards physical property evaluation of bio-treated geomaterials in ocean environment, and demonstrate the potential of scaling up MICP techniques for broader engineering application.

Study on settlement deformation law of new and old subgrade of expressway reconstruction and expansion based on CPTU

In the reconstruction and expansion of expressways in soft soil areas, controlling the differential settlement between the new and existing subgrades is of vital importance. To investigate the settlement and deformation characteristics of both the new and existing subgrades, piezocone penetration test (CPTU) and dissipation tests were conducted on these subgrades. The CPTU dissipation data was utilized to determine the soil’s degree of consolidation, and settlement calculations for the new and existing road subgrades were based on the CPTU test results. Subsequently, a finite element model was developed using the CPTU test findings to analyze the horizontal displacements, vertical settlements, and differential settlements of the new and existing subgrades before and after the reconstruction and expansion. Based on the measured settlement results, the new and old subgrade settlement calculation results are verified. The outcomes revealed that the degree of consolidation for the existing road subgrade of the Lianhuai Expressway ranged between 42 % and 96 %. The maximum horizontal displacement of the subgrade pre- and post-expansion occurred at the slope toe. Before expansion, the maximum vertical settlement was observed along the road’s centerline, while after expansion, it was located in the centerline of the widened section. The maximum additional settlement amounted to 274.77 mm. During the new road construction phase, the differential settlement between the new and existing road subgrades increased rapidly over time, peaking at its maximum value. However, during the operational phase of the new road, this differential settlement tapered off as time progressed.

The role of liquefaction in the evolution of shallow submarine canyon heads from a geotechnical perspective: A case study of the Garrucha Canyon (SE Mediterranean)

This work aims to establish the role of liquefaction in a shallow submarine environment defined by a canyon head reaching the coast. The study area is the Garrucha submarine canyon head, which is located in the western Mediterranean Sea.The potential of liquefaction is approached empirically by two methods in parallel, undrained cyclic direct simple shear (UCDSS) test and piezocone penetration test (CPTu) analyses. For both approaches, considering the regional earthquake records, a cyclic load linked to Mw ≤ 6.5 earthquake events or a maximum ground surface acceleration amax of 0.25 g is considered.The sediment samples analysed are nonplastic sands with low silt/clay contents and can be defined as liquefiable. Geotechnical analysis reveals a high probability of triggering liquefaction in this kind of sediment at depths greater than 3 m below the seafloor. CPTu records are used to assess and improve the liquefaction model for the study area by defining 3 different stratigraphic configurations or liquefiable conditions: uniformly liquefiable, interbedded liquifiable and nonliquefiable.This work highlights the importance of liquefaction—a process normally underestimated in submarine environments—in the downslope transport of sediment from the upper part of a canyon and, more generally, in canyon head evolution with different potential morphosedimentary consequences.

Influence of drainage conditions on piezocone penetration mechanism in offshore clays

ABSTRACT CPTu (piezocone penetration test) is widely used in engineering practice to determine various parameters of clays under partially drained conditions. However, most existing research is based on undrained or fully drained conditions for clays, leading to underestimation or overestimation of soil strength. By applying the Eulerian-Lagrangian large deformation finite element method to analyse the water-soil interaction, the CPTu driving mechanism in offshore saturated soft clays under different drainage conditions is revealed. An advanced hypoplastic constitutive model for clays is used to simulate the nonlinear behaviour of kaolin under different drainage conditions. The generation, accumulation, and dissipation of excess pore water pressure under different drainage conditions are analysed, as well as the influence of excess pore water pressure on cone tip resistance and the effective stress of the soil during the CPTu penetration process.

A Novel Method for Estimating the Undrained Shear Strength of Marine Soil Based on CPTU Tests

The undrained shear strength is an essential parameter in the foundation design of marine structures. Due to the complex marine environment and technical limitations, it is difficult and costly to obtain offshore samples. Piezocone penetration tests (CPTU) are relatively low-cost compared to drilling and sampling methods. Therefore, based on the soil behavior type index (Ic) derived from CPTU results, a model for estimating cone factors (Nkt, Nke) is proposed to improve the accuracy of estimation of undrained shear strength. The result shows that the soil behavior type index (Ic) and cone factors take on a negatively correlated exponential relation. Incorporating a cone factor that varies with the soil behavior type index (Ic) significantly enhances the accuracy of undrained shear strength predictions compared to the conventional method of using a constant cone factor. This approach reduces the root mean square error (RMSE) for Nkt (Nke) from 0.124 (0.126) MPa to 0.056 (0.06) MPa, and the mean absolute error (MAE) from 0.0154 (0.016) MPa to 0.0032 (0.0036) MPa. The method was validated at an additional location and the predictions were in high agreement with the results of the consolidated quick direct shear test. The developed method can serve as an effective tool used in the design of foundations of marine structures.

A Comprehensive Review of the Evaluation and Application of Engineering Properties of Expansive Soil Based on Piezocone Penetration Test (CPTU)

Expansive soil presents several challenges in civil and geotechnical engineering because of its distinctive physical and mechanical properties, including considerable volumetric fluctuations, non-linear stress–strain behaviour, and high permeability. Owing to soil disturbances and sample size limitations during sampling, important parameters such as the expansive soil expansion force, compressive strength, and shear strength obtained through indoor experiments often cannot accurately reflect the values in situ. In this regard, in situ piezocone penetration testing has the advantages of small disturbances and high efficiency and has been widely used in subways, bridges, highways, and other engineering projects. This paper comprehensively summarizes the research progress of in situ testing technology in the evaluation and application of engineering properties of expansive soils in China and internationally. First, a detailed analysis of the basic theories and physical mechanisms of various in situ testing methods is provided, focusing on their applicability and accuracy in expansive soils. Second, examples of the application of in situ testing technology in expansive soil engineering are summarized. Finally, predictive models and methods based on in situ testing data, especially those that introduce cutting-edge models such as machine learning and advanced data analysis techniques, are discussed.

CPTU-based permeability evaluation of clays

The piezocone penetration test (CPTU) is an efficient in-situ testing method for delineating subsurface stratigraphy and interpreting geoparameters continuously with depth. However, owing to the regional sensitivity and geological diversity, the applicability of CPTU-based geotechnical parameter evaluation methods is limited when applied to specific sites. This requires further scrutiny considering the different geological histories and local soil conditions. In this study, a database that included a collection of CPTU test sites in Jiangsu Province, China, was compiled containing high-quality sampling and laboratory testing performed to characterize the permeability of clay soils. Several published CPTU correlations for determining soil permeability were summarized and compared with laboratory-measured soil permeability as a benchmark reference. The evaluation results indicated that the I c-based correlations can provide a reasonably good determination of the permeability for the investigated soils with root mean squared error of 0.89 and mean absolute error of 0.77. Finally, a modified approach was presented to evaluate the permeability coefficient of Jiangsu clay soils, which was calibrated using two additional case studies.

Determination of the overconsolidation ratio and undrained shear strength of cohesive soils by CPTu measurement

Estimations of the undrained shear strength (Su) and overconsolition ratio (OCR) of cohesive soil are essential for the evaluation of geology investigation. In comparison to time-consuming laboratory tests, the field piezocone penetration test (CPTu) can rapidly evaluate these parameters. However, existing studies have mainly relied on empirical correlations to estimate the undrained shear strength Su and OCR from CPTu measurements. These correlations are mainly empirical, involving fixed coefficients multiplied by CPTu measurement. Based on the coupled Eulerian-Lagrangian method, this study employed large deformation finite element modeling to summarize and extend the relationships between CPTu measurement and the estimation of undrained shear strength Su and OCR in cohesive soils. These relationships allow for predictions based on CPTu measurements without the requirement for laboratory calibration or referencing to field benchmarks. The accuracy and applicability of the proposed prediction formulas are validated through field case studies for comparative analysis.

Cavity expansion-based interpretation of piezocone penetration test (CPTu) data in clays

A cavity expansion-based method is proposed in this paper to correlate the relevant findings with the piezocone penetration test (CPTu) data in clays. The rigorous and explicit solution for both spherical and cylindrical undrained cavity expansion is adopted based on a unified critical state constitutive model for clays and sands. The analogous model developed is comprehensively validated against two series of advanced numerical simulations and calibration chamber tests of the CPTu in fine-grained soils, along with bias analyses. The effects of the overconsolidation ratio and initial state parameter are extensively investigated for various clay types. Both theoretical and empirical correlations are then proposed for back-calculations of cone factor, undrained shear strength, overconsolidation ratio and initial state parameter of clays. Two case studies of CPTu tests are conducted in addition to examine correlations and contours of the in situ state parameter, demonstrating the applicability of the proposed theoretical approach for interpretation of the CPTu data.

Comparison of the Piezocone Penetrometer (CPTU) and Flat Dilatometer (DMT) Methods for Landslide Characterisation

The increasing occurrence of landslides worldwide causes many human casualties and huge socio-economic losses. Therefore, the fastest and most accurate characterisation of landslides is important. The objective of this study is to compare how well the flat dilatometer (DMT) test and the piezocone penetration (CPTU) test can find the depth of a sliding zone. Inclinometers were used to measure horizontal changes in the soil to ensure the depth of the sliding zone was correct. The coincidence of the results of in situ static probes, and the displacements of the inclinometers is a sure confirmation of the depth of the sliding zone. In the example of Bedekovčina and Kravarsko landslides, in situ static probes were used to obtain values of input parameters on the sliding zone for parametric sensitivity analysis of parameters. Sensitivity analysis was performed by plotting the relationship between the above parameters and the vertical effective stress σ′vo on the sliding zone. The sensitivity analysis of the parameters of 11 tested samples shows that for the parameters of the obtained DMT probe, a higher sensitivity of the parameters is obtained, closer to the values concerning the expected range, and a minor standard deviation. The parameter Kd obtained by dilatometer probing is the best indicator of the depth of the sliding zone. The literature value Kd = 1.8–2.0 on the sliding zone in this paper is extended to the range Kd = 1.8–2.5, and its detection sensitivity is influenced by over-consolidation in shallow soil layers. In general, the research results show that the dilatometer probe has an advantage over the piezocone penetrometer test for the needs of landslide characterisation.

A comparison between static and dynamic load tests of Tapered steel jacking piles in Baskarp sand

In this study, four full scale static compression tests were performed on a tapered steel jacking pile with diameters 76 mm and 89 mm in both dry and saturated soil conditions. Each test consists of multiple sub-tests with respect to determination of in-situ Baskarp Sand No.15 conditions and bearing capacities of the piles. Further, a finite element methodology has been developed to predict the load-displacement response of tapered piles installed in sand, incorporating the effects of jacking installation. The methodology is based on the identification of the failure mechanism and shear strain formation at failure around the pile as well as adoption of soil-soil interface elements. The nonlinear soil model parameters for a fully wished-in-place (fully-WIP) condition were obtained through piezocone penetration tests where various methods were applied to obtain the relative density, among which those providing best fit according to Jamiolokowski et al., (2003) were selected for further assessment. Finally, the hammer tests were performed from which the dynamic bearing capacities and the relation between static and dynamic bearing capacities were obtained.

Study on strength properties and soil behaviour type classification of Huanghe River Delta silts based on variable rate piezocone penetration test

Study on strength properties and soil behaviour type classification of Huanghe River Delta silts based on variable rate piezocone penetration test

The Use of CPTU and DMT Methods to Determine Soil Deformation Moduli—Perspectives and Limitations

Abstract The article presents the concept of determining constrained modulus—M0 , initial shear modulus—G0 , Young modulus—E, and rigidity index—IR on the basis of parameters from static penetration tests CPTU (Piezocone Penetration Testing), SCPTU (Seismic Piezocone Penetration Testing) and dilatometer tests DMT (Flat Dilatometer Test), SDMT (Seismic Flat Dilatometer Test). The basis for constructing the empirical relationships between the mentioned modules and parameters from the CPTU and DMT studies was to determine the factors that affect these relationships. The article discusses the impact of the following factors; geological and geotechnical conditions, conditions of recording measurements in CPTU and DMT tests, factors relating to the CPTU and DMT testing methods, factors affecting reference parameters from laboratory tests, factors related to subsoil properties. The basis for obtaining the empirical relationships for determining the analyzed modules and rigidity index were extensive research of the soils of various origins, in Poland. Measurement uncertainties and factors influencing the recorded parameters in the CPTU study were documented by the studies of the Norwegian Geotechnical Institute and the former Department of Geotechnics of the Agricultural University in Poznań. In these studies, penetrometers from several reputable manufacturers were used. The article summarizes the established empirical relationships for individual modules, taking into account the effect of overconsolidation. It also comments on the interrelationship between constrained modulus M0 from CPTU and DMT test for soils in Poland.

A new empirical model for the undrained shear strength of undisturbed marine fine-grained soil based on piezocone penetration tests

Simple, precise, and economical evaluation of the undrained shear strength Su of undisturbed marine soil can facilitate the construction of offshore projects. In this study, piezocone penetration tests (CPTu) were conducted at the site of a wind power project, and consolidated undrained triaxial tests were performed on specimens of undisturbed marine fine-grained soil taken from the site. Analysis shows that the Eslami–Fellenius and Chinese soil classification methods based on CPTu data are more applicable for marine soils. The test results indicate that the stress–strain curve exhibits strain softening if the clay content is less than 30 %, otherwise it exhibits either strain hardening or strain stability. Furthermore, the specimens exhibit two deformation failure modes: softening contraction and hardening dilatancy. From the correlation between the consolidated undrained triaxial test data and the CPTu data, Su can be determined simply via an explicit expression involving the measured pore pressure behind the cone (u2), the corrected cone tip resistance (qt), and the soil depth H, and this expression is significantly more precise than the existing empirical formulas. The proposed method offers a sound basis for designing the foundations of marine engineering and infrastructure projects in different sea region.

Estimating plasticity index directly from piezocone penetration tests in saturated natural soils

Plasticity index, Ip, is a relatable parameter for most geotechnical engineers, because Ip can be used to estimate other soil properties, such as internal friction angle, compression index, and low-strain shear modulus. Consequently, a method for estimating Ip directly from a piezocone penetration test (CPTU), which measures cone resistance, sleeve friction, and pore pressure would be useful for many practising geotechnical engineers. This technical note presents a method for estimating Ip profiles entirely from CPTU data. The new method has been calibrated using a case database of 258 complementary measurements taken, in natural soils, at 25 globally distributed marine sites.

Deterministic and Probabilistic Analyses of the Bearing Capacity of Screw Cast in Situ Displacement Piles in Silty Soils as Measured by CPT and SDT

The bearing capacity of screw cast in situ displacement piles is mostly unexplored. There is also insufficient research on piles in silty soils. Therefore, five cone penetration tests (CPT) and one piezocone penetration test (CPTu) using direct methods were utilised to determine the load-bearing capacity of four displacement piles in Estonia. In addition to the CPT sounding data, static-dynamic test (SDT) results were used to analyse the load-beating capacity of the piles. Both deterministic and probabilistic methods were used in the analysis. Characteristic values as a 95% reliable mean and 5% fractile values for sounding parameters, according to the Eurocode 7, were included. Additionally, Monte Carlo simulation was included in the reliability-based design (RBD). The bearing capacities of screw cast in situ displacement piles in silty soils, here based on the CPT and SDT sounding data, were similar. The adaptation of SDT results for the CPT direct methods for pile load-bearing capacity analysis certainly deserves attention and further investigation. For both sounding types, the Eurocode 7 method provided the best results for all piles. The results of pile-bearing capacities in the absolute difference varied within ±11% between the average, RBD and characteristic values.