Cone Penetration Test Results Research Articles

In-Situ Evaluation of Strength and Dilatancy of Sands Based on CPT Results

ABSTRACT In-situ tests have been increasingly used to estimate the shear strength of soils. In this paper, we propose methods to evaluate in-situ strength and dilatancy of sandy soils based on cone penetration test (CPT) results. It takes into account the silt content, relative density and stress state of the sand. A series of laboratory test results from fundamental property tests and triaxial tests are analyzed to develop methods for in-situ evaluation of strength and dilatancy for sands. Based on test results, modified and simplified dilatancy equations, in terms of the cone penetration resistance qc and intrinsic soil variables, are proposed. Results from proposed and original dilatancy indexes show close agreements for various soil conditions. Values of intrinsic variables for the proposed dilatancy relationships were proposed as a function of silt content. Based on TX test results, a direct CPT-based correlation, applicable to both clean and silty sands, is proposed as well. In order to verify the proposed methods, calibration chamber CPT results obtained in this study and collected from the literature are adopted. It is observed that the results from the proposed methods show good agreement with the measured results.

Utilization of self-organizing map and fuzzy clustering for site characterization using piezocone data

In this paper soft computing techniques, self-organizing maps and fuzzy clustering techniques have been proposed to isolate different layers in stratified soil based on available cone penetration test results. The results have been compared with that obtained from cone classification chart, hierarchical and K-mean clustering techniques. It was observed that variation in result with self-organizing map (SOM) and fuzzy clustering for isolating soil layers is marginal. These techniques are found to be efficient compared to hierarchical clustering technique. The results of K-mean clustering show that the identified soil strata are similar to that obtained from cone classification chart, SOM and fuzzy clustering.

Shear strength characterization of municipal solid waste at the Suzhou landfill, China

The current practice of slope stability analysis for a municipal solid waste (MSW) landfill usually overlooks the dependence of waste properties on the fill age or embedment depth. Changes in shear strength of MSW as a function of fill age were investigated by performing field and laboratory studies on the Suzhou landfill in China. The field study included sampling from five boreholes advanced to the bottom of the landfill, cone penetration tests and monitoring of pore fluid pressures. Twenty-six borehole samples representative of different fill ages (0 to 13 years) were used to perform drained triaxial compression tests. The field and laboratory study showed that the waste body in the landfill can be sub-divided into several strata corresponding to different ranges of fill age. Each of the waste strata has individual composition and shear strength characteristics. The triaxial test results showed that the MSW samples exhibited a strain-hardening and contractive behavior. As the fill age of the waste increased from 1.7 years to 11 years, the cohesion mobilized at a strain level of 10% was found to decrease from 23.3 kPa to 0 kPa, and the mobilized friction angle at the same strain level increasing from 9.9° to 26°. For a confinement stress level greater than 50 kPa, the shear strength of the recently-placed MSW seemed to be lower than that of the older MSW. This behavior was consistent with the cone penetration test results. The field measurement of pore pressures revealed a perched leachate mound above an intermediate cover of soils and a substantial leachate mound near the bottom of the landfill. The measurements of shear strength properties and pore pressures were utilized to assess the slope stability of the Suzhou landfill.

Use of in Situ Tests in Compaction Control of a Bottom Ash Embankment

Since 1994, the Indiana Department of Transportation has constructed numerous recycled materials projects that use bottom ash, fly ash, foundry sand, crushed glass, and tire shreds in transportation facilities. All these projects were constructed in accordance with procedural specifications based on conventional compaction control tests such as the nuclear gauge. However, the nuclear gauge does not give accurate density and moisture content results because of the presence of numerous elements in recycled materials. In addition, sand cone tests are cumbersome and time-consuming. There is a need to develop criteria for in situ test methods such as the dynamic cone penetration test and lightweight deflectometer (LWD) testing. Once an initial criterion is established, criteria for compaction control of similar recycled materials can be developed. In a study, a test pad using coal ash was constructed with a combination of roller passes. On the basis of the results of dynamic cone penetration and LWD tests conducted in the test pad, in conjunction with a combination of roller passes, the criteria for compaction control of bottom ash was provided for the construction of the remaining 11-m-high embankment. The subsequent construction monitoring and postconstruction evaluation of the bottom ash embankment revealed that the criteria are very effective.

A New Computer Program for Pile Capacity Prediction using CPT Data

An interactive computer program “GLAMCPT” is developed for application in soil profiling and prediction of pile load capacity using cone penetration test (CPT) and laboratory soil test results. GLAMCPT calculates pile capacity according to 10 selected methods from European design codes, refereed international publications and recommendations of professional institutions. To demonstrate the capabilities of the program, a database of comprehensive ground investigation and full-scale pile tests in sand, at a Belgian site, is analysed using GLAMCPT. The database comprises 11 static tests and 12 dynamic tests on piles of different construction techniques, including driven pre-cast concrete piles and screwed cast in-situ piles, installed using 5 different procedures. Prior to pile installation, CPTs were carried out at each proposed pile location. Comparison of GLAMCPT predictions with the observed pile capacities reveals that the most accurate of the existing methods yields an average, μ, of predicted to observed pile head capacity [P uh(p)/P uh(m)] equal to 0.94. The most consistent method produces a coeffcient of variation (COV) of [P uh(p)/P uh(m)] equal to 0.1 and ranking index (RI) of 0.08. Parametric studies have been carried out using GLAMCPT to formulate an improved predictive method, which yielded: μ = 0.99, COV = 0.07 and RI = 0.04.

Machine learning in soil classification

In a number of engineering problems, e.g. in geotechnics, petroleum engineering, etc. intervals of measured series data (signals) are to be attributed a class maintaining the constraint of contiguity and standard classification methods could be inadequate. Classification in this case needs involvement of an expert who observes the magnitude and trends of the signals in addition to any a priori information that might be available. In this paper, an approach for automating this classification procedure is presented. Firstly, a segmentation algorithm is developed and applied to segment the measured signals. Secondly, the salient features of these segments are extracted using boundary energy method. Based on the measured data and extracted features to assign classes to the segments classifiers are built; they employ Decision Trees, ANN and Support Vector Machines. The methodology was tested in classifying sub-surface soil using measured data from Cone Penetration Testing and satisfactory results were obtained.

Cone penetration tests under simulated field conditions

Cone penetration tests (CPT) performed in a conventional cavity-wall calibration chamber are inevitably affected by boundary conditions. The authors have developed an axisymmetric field simulator whereby CPT calibration tests can be conducted under substantially reduced boundary effects. The simulator consists of a cylindrical, physical sand specimen and a stack of expandable rings to simulate the soil from beyond the physical boundary. A series of CPT calibration tests has been performed in a clean, uniformly graded quartz sand using this simulator system. For a given relative density, the cone tip resistance (qc) was found to be most closely related to mean normal stress. The horizontal stress at the physical boundary increased during CPT under simulated field conditions. This increased horizontal stress had a much more significant and consistent effect on qc than the initial horizontal stress existing in the soil prior to CPT. The paper describes the results of CPT in the simulator, and discusses implications for the performance of CPT in a chamber and their interpretation.

Cone penetration tests under simulated field conditions

Cone penetration tests (CPT) performed in a conventional cavity-wall calibration chamber are inevitably affected by boundary conditions. The authors have developed an axisymmetric field simulator whereby CPT calibration tests can be conducted under substantially reduced boundary effects. The simulator consists of a cylindrical, physical sand specimen and a stack of expandable rings to simulate the soil from beyond the physical boundary. A series of CPT calibration tests has been performed in a clean, uniformly graded quartz sand using this simulator system. For a given relative density, the cone tip resistance (qc) was found to be most closely related to mean normal stress. The horizontal stress at the physical boundary increased during CPT under simulated field conditions. This increased horizontal stress had a much more significant and consistent effect on qc than the initial horizontal stress existing in the soil prior to CPT. The paper describes the results of CPT in the simulator, and discusses implications for the performance of CPT in a chamber and their interpretation.

Evaluation of the liquefaction potential of soil deposits based on SPT and CPT test results

In the literature, predictions for the occurrence of nonlinear soil liquefaction in soil deposits have been investigated through numerous empirical methods. These methods which are also known as ‘conventional techniques’ were derived from several in-situ tests, laboratory tests and case records. An alternative general regression neural network (GRNN) model that addresses the collective knowledge built in a simplified procedure is proposed. To meet this objective, a total of 3895 case records including twelve soil and seismic parameters driven mostly from the cone penetration test (CPT) results are introduced into the model. The data includes the results of field tests from the two major earthquakes that took place in Turkey and Taiwan in 1999 and some of the desired input parameters are obtained from correlations existing in the literature. The soil liquefaction decision in terms of seismic demand and capacity is determined by recognized simplified approach, namely a stress-based method and a strain-based method. Furthermore, the liquefaction probability of soils with significant fines is tested with the so-called Chinese Criteria. The proposed GRNN model is developed in four phases, mainly: the identification phase, collection phase, implementation phase, and verification phase. An iterative procedure was followed to maximize the accuracy of the proposed model. The case records were divided randomly into testing, training, and validation datasets. The proposed GRNN model effectively explored the complex relationship between the introduced soil and seismic input parameters and validated the liquefaction decision.

Comparisons of constitutive models for anisotropic soils

Constitutive modeling is a method by which anisotropy, one of the important affecting factors on the behavior of natural soils, could be properly simulated. In this research, three anisotropic constitutive models with comparative theories and model parame ters (anisotropic modified Cam-Clay model, Banerjee model, and bounding surface model) were formulated in a frame of finite strain, to predict the cone penetration test results. The prediction by each constitutive model was investigated and compared with the experimental result. The influence of the model parameters was theoretically and practically identified. The model predictions generally showed good agreement with the experimental results in cone resistance profile (8≈10% difference for OCR=1 specimen and 10≈17% difference for OCR=10 specimen), which is due to the model capacity and finite strain formulation as well as the homogeneity of the artificially prepared soil specimen and axisymmetric condition (no full anisotropy); however, the effort to reduce the number of parameter, with keeping the capacity of the model, is needed in the practical purpose.

Estimation of Load Capacity of Pipe Piles in Sand Based on Cone Penetration Test Results

Pipe piles can be classified as either closed- or open-ended piles. In the present paper, the load capacity of both closed- and open-ended piles is related to cone penetration resistance qc through an experimental program using calibration chamber model pile load tests and field pile load tests. A total of 36 calibration chamber pile load tests and two full-scale field pile load tests were analyzed. All the test piles were instrumented for separate measurement of each component of pile load capacity. Based on the test results, the normalized base resistance qb/qc was obtained as a function of the relative density DR for closed-ended piles, and of both the relative density DR and the incremental filling ratio (IFR) for open-ended piles. A relationship between the IFR and the relative density DR is proposed as a function of the pile diameter and driving depth. The relationship between IFR and DR allows the estimation of IFR and thus of the pile load capacity of open-ended piles at the design stage, before pile driving operations.

Empirical correlations of soil parameters based on Cone Penetration Tests (CPT) for Greek soils

This study presents the results of Cone Penetration Tests (CPT) and estimated correlations with the results of other in-situ tests (standard penetration test, cross-hole, seismocone) and laboratory tests (classification and undrained shear strength tests). These tests cover nearly all types of penetrable soils in Greece and, together with the formulation of empirical correlations, complement and improve on previous studies due to the significant number of CPT measurements.

Estimation of Load Capacity of Pipe Piles in Sand Based on Cone Penetration Test Results

Estimation of Load Capacity of Pipe Piles in Sand Based on Cone Penetration Test Results

Estimation of Footing Settlement in Sand

The settlement of foundations under working load conditions is an important design consideration. Well‐designed foundations induce stress‐strain states in the soil that are neither in the linear elastic range nor in the range usually associated with perfect plasticity. Thus, in order to accurately predict working settlements, analyses that are more realistic than simple elastic analyses are required. The settlements of footings in sand are often estimated based on the results of in situ tests, particularly the standard penetration test (SPT) and the cone penetration test (CPT). In this article, we analyze the load‐settlement response of vertically loaded footings placed in sands using both the finite element method with a nonlinear stress‐strain model and the conventional elastic approach. Calculations are made for both normally consolidated and heavily overconsolidated sands with various relative densities. For each case, the cone penetration resistance qc is calculated using CONPOINT, a widely tested program that allows computation of qc based on cavity expansion analysis. Based on these analyses, we propose a procedure for the estimation of footing settlement in sands based on CPT results.

The cavity expansion problem for the interpretation of cone penetration and pressuremeter tests

This paper presents a method of evaluation of the state of cohesionless soil from the results of cone penetration and pressuremeter tests. This method is based on the comparison of the solutions to the cylindrical and spherical cavity expansion problems obtained by the authors with experimental results available in the literature on cone penetration and pressuremeter tests in large calibration chambers. The solutions to the cavity expansion problems are obtained with the use of a constitutive equation of hypoplasticity calibrated for the same soils as in the experiments. The pressure-expansion curves from pressuremeter tests are compared with those calculated for the expansion of a cylindrical cavity. The relation between the cone resistance measured in cone penetration tests and the limit pressure calculated for a spherical or a cylindrical cavity is established through a shape factor. Soils with similar granulometric properties are found to exhibit a common shape factor as a function of the pressure-dependent relative density. Key words: cone penetration test, pressuremeter test, cavity expansion, hypoplasticity

Determination of Pile Base Resistance in Sands

Advances in the design of axially loaded piles are desirable because significant cost savings may result. Well-designed piles settle by amounts that are well tolerated by the superstructure and induce strains around the pile base that are far removed from failure. To investigate the development of base resistance for a given soil condition and increasing settlements, piles embedded in sand are modeled using the finite-element method with a nonlinear elastic-plastic model. Based on the load-settlement response obtained from the finite-element analysis and cone penetration resistance obtained from cavity expansion and stress rotation analyses, values of normalized base resistance, defined as base resistance divided by cone penetration resistance, are obtained. The relationship between base resistance and cone resistance is useful in the design of deep foundation using cone penetration test results. The effect of the initial coefficient of earth pressure at rest K0 on normalized base resistance values is als...

Layered elastic model for analysis of Cone Penetration Testing

A layered elastic model is adopted in the paper for the analysis of soil layering effects on the results of Cone Penetration Testing (CPT). Analytical solutions associated with the layered elastic CPT model and obtained via numerically integrating the fundamental singular solution for layered elastic solids due to the action of a body force concentrated on a circular ring. The soil layering effects on the CPT tip and friction resistance are examined in detail using the layered elastic CPT model. These examinations include parametric studies, influence of soil compressibility, comparisons with theoretical results given in the literature, verification with experimental data and simulation of field trial results. The examinations lead to the conclusions that the layered elastic CPT model can be used to analyse soil layering effects on CPT results and to estimate relative shear modulus strength of soil layers. Copyright © 1999 John Wiley & Sons, Ltd.

Technology of air-transported stabilized dredged fill. Part 2: quality assessment

A framework for the quality assessment of cement-treated ground, based on considerations of reliability, the regionalized variable theory and the observational method, is presented. From the results of laboratory and preconstruction field tests, the reliability-based quality index is defined on the basis of a function representing the actual strength of the stabilized ground normalized by the design strength. Quality control during construction is carried out by adopting a threshold quality index satisfying the designated probability of failure. Taking advantage of the regionalized variable theory, the technique employs the results of cone penetration tests for semivariogram analysis and applies the kriging technique for optimal interpolation and development of isostrength contours within the stabilized ground for quality assurance. The applicability of the proposed technique is examined by means of a field pilot study presented in the previous phase of this study.

Evaluation of Resilient Modulus of Subgrade Soil by Cone Penetration Test

Pavement design based on the resilient modulus of subgrade soil has been adopted by many transportation agencies following the recommendations of the AASHTO guide for design of pavement structures. Laboratory and field nondestructive tests are generally used to evaluate the resilient modulus of subgrade soil. These methods have shortcomings and limitations and are considered laborious, time-consuming, and expensive. The difficulties associated with the existing methods signify the need for a popular in situ technology for evaluating the resilient modulus of subgrade soil. Among other methods, the cone penetration test (CPT) is fast, simple, and economical and provides repeatable and reliable results. The results of a pilot investigation to assess the possibility of predicting the resilient modulus of subgrade soil from the CPT soundings are presented here. Field and laboratory testing programs were carried out on two types of cohesive soils at the Louisiana Transportation Research Center/Pavement Research Facility. Field tests consisted of CPT soundings using the 15-cm2 friction cone penetrometer and the 2-cm2 miniature friction cone penetrometer. Laboratory tests included the resilient modulus and physical properties of the investigated soils. The results of the miniature CPT were evaluated and compared with the soundings of the 15-cm2 cone at the same site. Both laboratory and field tests were analyzed. Based on statistical analyses, a model was proposed to estimate the resilient modulus from the CPT data and basic soil properties. Predicted values of the resilient modulus are consistent with laboratory measurements.

A comparison between observed and calculated large settlements of raft foundations

This paper shows the results of large settlements observed over several years in Belgrade for a hotel founded on four rectangular rafts with expansion joints of 1 m width, and for a silo group built on the right bank of the Danube River. The capacity of the silo group is 400 MN. The settlement calculation for these structures was made using deformation parameters deduced from cone penetration test results. The theoretical solution for stresses and displacements was obtained by the finite difference method. Observed and calculated settlements show satisfactory agreement.Key words: settlement, raft foundation, finite difference, cone penetration tests.