Thin-layer effects on the CPT qc measurement

2005 ◽  
Vol 42 (5) ◽  
pp. 1302-1317 ◽  
Author(s):  
M M Ahmadi ◽  
P K Robertson
Keyword(s):  
Correction Factor ◽  
Soft Clay ◽  
Soil Layer ◽  
Cone Penetration ◽  
Dense Sand ◽  
Layer Interface ◽  
Cone Tip Resistance ◽  
Tip Resistance ◽  
Resistance Modeling ◽  
Good Agreement

A numerical analysis is presented to model the cone penetration test (CPT) tip resistance in layered soil. Analyses are performed for two-layer soils composed of either sands with different relative densities or different materials (sand and clay). Parametric numerical modeling is used to determine the distance that a cone senses a new upcoming soil layer interface or a layer interface behind. Analyses are also carried out for a thin sand layer embedded in soft clay. It is seen that the full tip resistance may not be reached in thin stiff layers. This is especially true for penetration in thin dense sand layers interbedded in softer clay. A correction factor is suggested to correct the cone tip resistance in thin sand layers. The higher the stiffness and the thinner the layer, the larger the correction factor. The numerical results obtained in this paper are in good agreement with experimental observations. Some limitations of a previously proposed correction factor are discussed.Key words: cone tip resistance, modeling, sand, clay, interface influence distance, layering.

Influence of placement method on the cone penetration resistance of hydraulically placed sand fills

2001 ◽  
Vol 38 (3) ◽  
pp. 592-607 ◽  
Author(s):  
K M Lee
Keyword(s):  
Cone Penetration ◽  
Density Profiles ◽  
Hydraulic Fill ◽  
Dense Sand ◽  
Cone Penetration Tests ◽  
Cone Tip Resistance ◽  
Tip Resistance ◽  
Wide Range ◽  
Penetration Tests

The reclamation for the new airport at Chek Lap Kok in Hong Kong included the placement of a substantial volume of sand fill by various hydraulic placement techniques, which resulted in a wide range of as-placed densities of the sand fill. This paper described the use of cone penetration tests (CPT) on the evaluation of the possible ranges of density achievable by various hydraulic placement methods adopted in the construction of the new airport. The results of the CPT indicated that the placement technique is one of the most important factors in controlling the as-placed density of hydraulically placed sand fill. There is a marked contrast in cone tip resistance (and the associated relative density) profiles for the sand fills formed by subaerial and subaqueous placement methods, in which the cone tip resistance of the sand fill formed by subaerial placement is substantially higher than that of the sand fill formed by subaequeous placement. The results confirm that dense sand fill cannot be formed by subaqueous placement methods. The weakest zone is generally located just beneath the water level where fill is placed by subaqueous discharge.Key words: sand, hydraulic fill, cone penetration test, calibration chamber test, in situ density.

Experimental Research on Determining the Geotechnical Parameters with CPTU Methods

2011 ◽  
Vol 250-253 ◽  
pp. 1798-1803
Author(s):  
Yan Yong An ◽  
Bao Tian Wang
Keyword(s):  
Soft Clay ◽  
Cohesive Soil ◽  
Sensor Technology ◽  
Soil Parameters ◽  
Cone Penetration ◽  
Test Technique ◽  
Geotechnical Parameters ◽  
Cone Tip Resistance ◽  
Laboratory Test Results ◽  
Tip Resistance

Cone penetration test is a fast and efficient in-situ test technique. With the development of sensor technology and the use of new probes, such test is employed in more fields and reveals more soil parameters. Based on the advanced CPTU equipment, porewater pressure dissipation processes were measured at different depths, dissipation characteristics of the sandy soil and cohesive soil were analyzed respectively; Then, consolidation and permeability coefficients of the cohesive soil were calculated, the results are close to the laboratory test results. Undrained shear strength of soft clay were determined use theoretical and empirical methods, calculation accuracy of these methods were analyzed and the results show that the total cone tip resistance method is in good consistence with the measured values. CPTU is able to provide plenty of geotechnical parameters; therefore, more experience of regional tests should be drawn so as to produce more economic and technical benefit in the future.

Computerized Cone Penetration Test for Soil Classification

2008 ◽  
Vol 2053 (1) ◽  
pp. 47-64 ◽  
Author(s):  
Murad Y. Abu-Farsakh ◽  
Zhongjie Zhang ◽  
Mehmet Tumay ◽  
Mark Morvant
Keyword(s):  
Classification System ◽  
Soil Classification ◽  
Cone Penetration Test ◽  
Classification Systems ◽  
Fuzzy Classification ◽  
Classification Methods ◽  
Penetration Test ◽  
Cone Penetration ◽  
Cone Tip Resistance ◽  
Tip Resistance

Computerized MS-Windows Visual Basic software of a cone penetration test (CPT) for soil classification was developed as part of an extensive effort to facilitate the implementation of CPT technology in many geotechnical engineering applications. Five CPT soil engineering classification systems were implemented as a handy, user-friendly, software tool for geotechnical engineers. In the probabilistic region estimation and fuzzy classification methods, a conformal transformation is first applied to determine the profile of soil classification index (U) with depth from cone tip resistance (qc) and friction ratio (Rf). A statistical correlation was established in the probabilistic region estimation method between the U index and the compositional soil type given by the Unified Soil Classification System. Conversely, the CPT fuzzy classification emphasizes the certainty of soil behavior. The Schmertmann and Douglas and Olsen methods provide soil classification charts based on cone tip resistance and friction ratio. However, Robertson et al. proposed a three-dimensional classification system that is presented in two charts: one chart uses corrected tip resistance (qt) and friction ratio (Rf); the other chart uses qt and pore pressure parameter (Bq) as input data. Five sites in Louisiana were selected for this study. For each site, CPT tests and the corresponding soil boring results were correlated. The soil classification results obtained using the five different CPT soil classification methods were compared.

Comparison of Measured and Back Estimated Cone Penetration Resistance of Sand

2008 ◽  
Author(s):  
Meen-Wah Gui ◽  
Dong-Sheng Jeng
Keyword(s):  
Penetration Resistance ◽  
Cavity Expansion ◽  
Cone Penetration ◽  
Cone Penetration Tests ◽  
Cone Tip Resistance ◽  
Tip Resistance ◽  
Cone Penetration Resistance ◽  
Expansion Theory ◽  
Cavity Expansion Theory ◽  
Penetration Tests

The application of cavity expansion theory in the back estimation of cone penetration tests conducted in calibration chambers has been carried out by many researchers. However, the theory is seldom employed by centrifuge modelers. Based on the work of spherical cavity expansion of previous researchers, this study proposed an analytical solution that incorporates the effects of cone geometry and surface roughness and the effect of compressibility to estimate the cone tip resistance. The calculated results are compared with the measured cone penetration resistance of four cone penetration tests performed in the centrifuge. The cone penetration tests were conducted in granular soil specimens having relative densities ranging between 54% and 89%. The comparison demonstrates the capacity of the cavity expansion theory in the prediction of the centrifuge cone penetration resistance.

Statistical relationships between piezocone measurements and stress history of clays

1996 ◽  
Vol 33 (3) ◽  
pp. 488-498 ◽  
Author(s):  
B SY Chen ◽  
P W Mayne
Keyword(s):  
Cone Penetration ◽  
Stress History ◽  
Statistical Correlations ◽  
Cone Tip Resistance ◽  
Clay Deposits ◽  
Preconsolidation Pressure ◽  
Tip Resistance ◽  
History Of ◽  
Statistical Relationships ◽  
Oedometer Tests

A database containing piezocone soundings from 205 clay sites around the world has been compiled for the calibration of an analytical cone penetration model and the development of statistical correlations. Yield stresses from laboratory oedometer tests were used as reference values for determining the stress history of natural clay deposits. Both simple and multiple regression analyses were performed on these data to evaluate correlative trends. Several simplified empirical relationships were identified for use in practice with the most reliable in relating preconsolidation stress to net cone tip resistance. Key words: cone tip resistance, overconsolidation ratio (OCR), preconsolidation pressure, piezocone, statistical relationships, stress history.

Cone Penetration Test Study of Ultra Soft Soil after Vacuum Preloading

2014 ◽  
Vol 580-583 ◽  
pp. 585-588
Author(s):  
Jiong Qi Yu ◽  
Hong Wen Li ◽  
Wen Shuang Wang
Keyword(s):  
Surface Layer ◽  
Soft Soil ◽  
Research Work ◽  
Cone Penetration Test ◽  
Penetration Test ◽  
Cone Penetration ◽  
Vacuum Preloading ◽  
Hydraulic Fill ◽  
Cone Tip Resistance ◽  
Tip Resistance

No sand cushion vacuum preloading method is one of the construction technology for treating the ultra soft soil formed with hydraulic fill at present. The practice is ahead of the scientific research work, as the effect detection technology of the surface-layer improvement is still in the stage of exploration. In this paper, the cone penetration test (CPT) is used to detect the effect of the surface-layer improvement of the ultra soft soil based on one case in Zhejiang province in China. The result shows that the cone tip resistance is at the range of 0.08 ~ 0.40MPa and the thickness varies about 1.5 to 2.2 m of the treated ultra soft soil. The cone tip resistance along the depth has two kinds of curve shape and four zones.

scholarly journals Spatial Correlation of Cone Tip Resistance for Soil in Nasiriyah

2018 ◽  
Vol 12 (1) ◽  
pp. 413-429
Author(s):  
Ressol R. Shakir
Keyword(s):  
Spatial Correlation ◽  
Soil Layer ◽  
Vertical Direction ◽  
Site Investigation ◽  
Linear Quadratic ◽  
Mean Values ◽  
Polynomial Degree ◽  
Reliability Based Design ◽  
Cone Tip Resistance ◽  
Tip Resistance

Background:Quantification of soil property spatial variations is an important step in any reliability-based design. Little stochastic parameter information about the soil in Nasiriyah, which is in southern Iraq, is available.Methods:In this paper, the Scale Of Fluctuation (SOF) for the site soil is examined, which is suggested for construction of the refinery fuel station project as no random parametric quantity has been studied in this region. A Cone Penetration Test (CPT) was performed as part of the site investigation to a depth of 20 m in the vertical direction, and 24 CPTs were analyzed within the site. The spatial correlation was computed using four methods, including Single Exponent (SNE), Square Exponent (SQE), Cosine Exponent (CSE) and Second-Order Markov (SOM). Identification of the soil type depended on the most recent classification chart, which is based on CPT results. The spatial correlation was evaluated for the vertical direction considering the cone tip resistance (qc) component. Three trend functions were applied to all CPT soundings, including linear, quadratic and cubic polynomials, which were utilized to transform the non-stationary data to stationary data. Three modes of soil were employed, including the eight-meter soil layer, a twelve-meter soil layer and the entire twenty meters of soil, which includes both layers.Results and Discussion:The mean values of SOF were 0.54 m, 0.53 m, and 1.73 m for soil layers 8 m, 12 m, and 20 m, respectively. The high value of the last mean is attributed to the 20 m of stratification in the ground. This study also indicates that the SOF decreases as the polynomial degree increases, which is due to enhanced fitting. The coefficient of variation (COV) for the SOF shows little variability for most of the studied soil cases.

Effect of Stress History and Shallow Embedment on Centrifuge Cone Penetration Tests in Sand

2019 ◽  
Author(s):  
Anamitra Roy ◽  
Shiaohuey Chow ◽  
Conleth O’Loughlin ◽  
Mark Randolph
Keyword(s):  
Silica Sand ◽  
Cone Penetration ◽  
Stress History ◽  
Buried Structures ◽  
Overconsolidation Ratio ◽  
Cone Penetration Tests ◽  
Cone Tip Resistance ◽  
Tip Resistance ◽  
Order Of Magnitude ◽  
Penetration Tests

Abstract The paper investigates the effect of stress history and shallow embedment on centrifuge cone penetration tests in sand. A series of centrifuge cone penetration tests were performed in loose and dense silica sand at g-levels ranging between 20 and 100 with corresponding overconsolidation ratio (OCR) between 1 and 5. Based on the measured cone tip resistance (qc) profiles, improved empirical correlations have been proposed with depth factors (fD) to impart additional flexibility in accurately back predicting sand relative density (RD) at shallow embedment in normally consolidated (NC) sands. The qc - RD correlations are then extended to capture overconsolidation effects in cone tip resistance, which is broadly consistent with the changes in compressibility and in-situ lateral stresses taking place in sands with increasing OCR levels. The proposed expressions allow accurate quantification of depth corrected CPT profiles in soils of varying overconsolidation ratio, for application in the interpretation of model tests on shallow foundations and anchors and in shallowly buried structures such as pipelines. The expressions also have application for interpretation of field CPT profiles where the thickness of interbedded layers is of similar order of magnitude to the cone diameter.

Reliability of self-boring pressuremeter in sand

1999 ◽  
Vol 36 (1) ◽  
pp. 102-110
Author(s):  
Debasis Roy ◽  
JMO Hughes ◽  
Richard G (Dick) Campanella
Keyword(s):  
The United States ◽  
The Self ◽  
Western Canada ◽  
Engineering Profession ◽  
Cone Penetration ◽  
Pressuremeter Test ◽  
Cone Tip Resistance ◽  
Tip Resistance ◽  
Testing Tool

The cone penetration test (CPT) is viewed by a majority in the geotechnical engineering profession as a preferred in situ testing tool, while the self-boring pressuremeter test (SBPMT) is sometimes viewed to be of questionable reliability. A comparative statistical study of SBPMT data and CPT cone tip resistance is undertaken in this research to examine whether the test data do actually support the perceived notion. Data from seven sand and silt sites in western Canada and one location in the United States have been examined. The sensitivity of the SBPMT to the variability in the state of packing is quantified and compared with the corresponding values for the cone tip resistance. The results indicate that the sensitivity of cone tip resistance and the SBPMT data to the variability in the in situ state of packing is comparable. Comparison of estimates of procedural uncertainties in the SBPMT and the CPT also leads to a similar conclusion. These observations do not support the notion of a general lack of reliability of the self-boring pressuremeter at sand-silt sites.Key words: reliability, sand, self-boring pressuremeter, piezocone, inherent variability, procedural uncertainty.

scholarly journals Parameterisation of the Koppejan settlement prediction model using cone penetration testing and gradient boosting

2020 ◽  
Vol 382 ◽  
pp. 443-447
Author(s):  
Kevin Duffy ◽  
Klaas Siderius ◽  
Mike Long
Keyword(s):  
Human Error ◽  
Gradient Boosting ◽  
Engineering Practice ◽  
Cone Penetration ◽  
Settlement Prediction ◽  
Fine Grained ◽  
Cone Penetration Testing ◽  
Cone Tip Resistance ◽  
Tip Resistance ◽  
Oedometer Tests

Abstract. This study examines how cone penetration test (CPT) parameters, such as cone tip resistance and friction sleeve resistance, can be used to assess the compressibility of fine-grained soils across the Netherlands based on a database of 286 paired CPTs and oedometer tests from across the country. This is done with the aim of refining and simplifying the parameterisation of the Koppejan consolidation coefficients, a procedure which can yield significant error and is prone to misinterpretation. It was found that there is significant potential in using gradient boosting methods to obtain a relationship between the CPT parameters and the Koppejan parameters, with further investigation required into the noise within the dataset and the acquisition of additional high-quality samples. The use of such methods will offer a means of reducing the influence of human error or misinterpretation on the prediction of settlement and provide further confidence in the use of machine learning methods in engineering practice.

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