Calibration Chamber Tests of a Cone Penetrometer in Sand PDF Download
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Author: G. T. Houlsby
Publisher:
ISBN:
Category : Laboratories
Languages : en
Pages :
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Author: G. T. Houlsby
Publisher:
ISBN:
Category : Laboratories
Languages : en
Pages :
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Author: An-Bin Huang
Publisher:
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 422
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Author: Sepideh Damavandinejad Monfared
Publisher:
ISBN:
Category :
Languages : en
Pages : 280
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Considering the difficulties associated with preparing loose sand samples in large calibration chambers and wide area of research on the behavior of loose sands, miniature calibration chamber experiments are used to perform cone penetration tests on soils in different states. A miniature cone calibration chamber has been designed and developed in this study. Nineteen tests have been performed on Ottawa sand and the results are compared to the available data in the literature. The accuracy of the results is validated by comparing the results with the suggested rate for the cone resistance in sands in literature. More specifically, results are compared with the results of the large calibration chamber tests performed on the same soil at University of Florida. Results are in a very good agreement with the literature and data available from large calibration chambers. Different soil identification systems are used to further validate and compare the results. Results of the performed tests are presented and discussed in terms of the repeatability of the developed apparatus, the effect of penetration rate, boundary condition effect, scale effect, particle crushing, overburden stress normalization and verification of the measurements. Some available procedures to perform a CPT-based liquefaction analysis including liquefaction susceptibility, triggering and post-liquefaction strength analysis are evaluated using the laboratory miniature CPT experiments performed in the current study. Some of the well-stablished equations to estimate soil properties required for liquefaction studies are also evaluated using the laboratory miniature CPT experiments performed in the current study. The existing methods for estimating state parameter from cone penetration test results are reviewed and an evaluation of the performance of the existing methods using the laboratory miniature CPT experiments performed in the current study is presented.
Author: Florian Thomas Stähler
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Geoffrey R. Martin
Publisher:
ISBN:
Category : Granular materials
Languages : en
Pages :
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"Verification of the densities for artificial sand fill islands in the Beaufort Sea is currently carried out using the cone penetration test (CPT). Cone penetration resistance is converted to relative density using one of the correlations published by Baldi et al (1982), Villet and Mitchell (1981) or Schmertmann (1975). These correlations have been derived on the basis of prototype chamber CPT tests on clean, generally dense, sands. Sand fills in the Beaufort Sea contain nominal silt fractions (1-5% fines) and the densities of interest are frequently less than those reported in the CPT chamber test programs. There is no sound justification that these published correlations in terms of relative density are valid for evaluation of sand fills in the Beaufort Sea. Ideally, a correlation between cone resistance and density would be developed for each sand type used in island construction. Such a program of CPT chamber tests would be extremely costly and time consuming. Early in 1984, Golder Associates proposed an alternative approach to CPT interpretation to Dome Petroleum, based on the state parameter approach to sand behaviour. It was hypothesized that the cone penetration resistance could be uniquely related to the state parameter, and that this correlation may be equally applicable to clean and silty sands. The initial phase of the evaluation of the state parameter approach to CPT interpretation involved a reinterpretation of existing calibration chamber test data in terms of state parameter. In order to do this, the Steady State line for each of the relevant CPT calibration sands must be known. The findings of the initial evaluation of the CPT/state interpretation are contained in this report.... One of the objectives of this study was to determine which correlation, if any, is most applicable to silty Beaufort Sea sand fills. On the basis of laboratory testing data, the CPT correlation sands essentially show the same engineering behaviour at large (failure) strains as Beaufort Sea sands, with or without silt. On this basis, any of the correlations with state parameter are applicable and the data on Figure 13 could readily be used to determine in situ state from CPT tests with reasonable accuracy. The significant point of the study is that a state parameter approach to CPT interpretation provides a rational interpretation of cone resistance in silty sands. Many of the problems associated with interpretation in terms of relation density along are avoided using the state parameter approach"--ASTIS database.
Author: Sepideh Damavandi-Monfared
Publisher:
ISBN:
Category : Field testing
Languages : en
Pages : 15
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Book Description
Cone penetration testing (CPT) has become the industry standard for in situ testing of cohesionless soils, and in particular, field liquefaction evaluation. The empirical methods for the interpretation of CPT data are either based on field data or the observation of CPT measurements in laboratory samples. In this study, a miniature cone penetrometer (with a diameter of 6 mm) is developed for understanding the response of loose to medium-dense sands. A modified triaxial cell is used for sample preparation and containment of the sample during cone penetration. The miniature cone can measure cone tip resistance, sleeve friction, and excess pore water pressure developed at the cone tip. While cone tip resistance is measured by a separate load cell, sleeve friction is obtained by subtracting cone tip resistance from a combined measurement of tip resistance and sleeve frictional force. Due to the free-draining nature of the sand tested in this study, no excess pore water pressure is developed during cone penetration. The measured data from the miniature cone are verified by comparison with CPT resistances measured in several other calibration chamber experiments on similar sands. Compared to a large calibration chamber with a standard size cone, the miniature cone allows quicker and less expensive CPT experiments in a more uniform sample.
Author: Joanna Butlanska
Publisher:
ISBN:
Category :
Languages : en
Pages : 565
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Cone penetration test (CPT) is a fast and reliable site investigation tool for exploring soils and soft ground. While the interpretation of the test results in clay has advanced considerably from a theoretical and numerical viewpoint that of tests in sands still relies largely on empirical correlations. A major source of such correlations comes from tests done in calibration chambers (CC), where soil state and properties might be tightly controlled. Calibration chambers are relatively large pieces of equipment, and calibration chamber testing is expensive and time consuming. Moreover, CC tests are performed on freshly reconstituted sands whose fabric may vary from that of natural sand deposits. Hence, correlations developed for one type of sand might not be suitable for another sand deposit. Numerical DEM-based calibration chambers might offer an interesting alternative to the more cumbersome physical tests. This study is the first attempt to perform a three-dimensional DEM-based simulation of cone penetration test. The three-dimensional commercial DEM code (PFC3D) is used to develop Virtual Calibration Chamber CPT (VCC CPT) model. To achieve that objective, several steps were necessary. First, calibration of an analogue discrete material to represent Ticino sand was performed using single-element tests. Afterwards, the mechanical response of the discrete material was further validated by performing additional triaxial tests with different initial conditions. The VCC CPT model was then constructed. Comprehensive dimensional analysis showed that the best option to balance computational efficiency and realism was to fill the chamber with a scaled-up calibrated discrete material. An original filtering technique was proposed to extract steady state cone resistances. A basic series of simulations was performed to explore the effect of initial stress and relative density in cone resistance. The results obtained from the simulations did fit closely the trends that had been previously established using physical chambers. That result was taken as a general validation of the proposed simulation approach. From the micromechanical point of view, the granular material is highly discontinuous and inhomogeneous. Obtaining a homogeneous initial state (especially in the zone of the penetrating cone) is crucial to obtain easily interpretable results. Specific procedures to assess initial state inhomogeneities were developed. DEM-based models can provide results at various level of resolution i.e. the microscale, the meso-scale and the macro-scale. A large series of VCC CPT has been performed. Simulations were performed for models with different horizontal servo-control walls, various sizes of chamber, cone and particles and two boundary conditions. The results were analyzed, focusing on aspects such as chamber size, particle size and boundary condition effects on steady state cone resistance values. A smaller number of tests have also been examined from the point of view of shaft resistance. Most trends and results obtained are shown to be in agreement with previous physical tests. When disagreements appear, the causes are identified: the most severe disagreements result from initial inhomogeneities in the discrete model. The work described in this thesis showed ease the burden of future CPT calibrations in granular materials.
Author:
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Category :
Languages : en
Pages :
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The static cone penetration tests are quite extensively used for carrying out in-situ geotechnical investigations both for onshore and offshore sites especially where the soil mass is expected to comprise of either soft to medium stiff clays or loose to medium dense sands. The wide use of the cone penetration tests (CPT) in geotechnical engineering has resulted in a great demand for developing necessary correlations between the cone penetration resistance and different engineering properties of soils. The successful interpretation of the cone penetration test data depends mainly on the various empirical correlations which are often derived with the help of a controlled testing in calibration chambers. The calibration chambers have been deployed in various sizes (diameter varying from 0.55 m to 2.10 m) by a number of researchers. It is quite an expensive and time consuming exercise to carry out controlled tests in a large size calibration chamber. The task becomes even much more difficult when a sample comprising of either silt or clay has to be prepared. As a result, most of the reported cone penetration tests in calibration chambers are mainly performed in a sandy material. Taking into account the various difficulties associated with performing tests in large calibration chambers, in the present study, it is attempted to make use of a miniature static cone penetrometer having a diameter of 19.5 mm. This cone was gradually penetrated at a uniform rate in a triaxial cell in which a soil sample of a given material was prepared; the diameter of the cone was intentionally chosen smaller so that the ratio of the diameter of the cell to that of the cone becomes a little larger. Two different diameters of the cells, namely, 91 mm and 140 mm, were used to explore the effect of the ratio of chamber (cell) size to that of the cone size. In addition, the rate of penetration rate was also varied from 0.6 mm/minute to 6.0 mm/minute (the maximum possible rate for the chosen triax.
Author: Rodrigo Salgado
Publisher:
ISBN:
Category : Soils
Languages : en
Pages : 764
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Author: Paul W. Mayne
Publisher: Transportation Research Board
ISBN: 0309097843
Category : Penetrometer
Languages : en
Pages : 126
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NCHRP synthesis 368 explores the current practices of departments of transportation associated with cone penetration testing (CPT). The report examines cone penetrometer equipment options; field testing procedures; CPT data presentation and geostratigraphic profiling; CPT evaluation of soil engineering parameters and properties; CPT for deep foundations, pilings, shallow foundations, and embankments; and CPT use in ground modifications and difficult ground conditions.
