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Automatic interpretation and statistical evaluation of soil conditions for preliminary design of offshore foundations using the cone penetration test
Published in Guido Gottardi, Laura Tonni, Cone Penetration Testing 2022, 2022
L. Berenguer Todo Bom, M. Kanitz
Following the ground model definition, the derivation of the soil parameters relevant to the foundation design is undertaken. The CPT measurements are analyzed to derive the strength and stiffness parameter of the determined soil units. In the preliminary stage of the design process, typically, laboratory tests results of the soil are not yet available. Well-established correlations for the relevant soil parameters are hence employed to derive a first estimate of the soil properties from the in-situ CPT measurements. For all soil types, the submerged unit weight γ’ and the small strain shear modulus G0 are derived. The soil type determines which correlation (see Sec. 2.3) is used to derive G0. For clay and silty clay soils, the undrained shear strength cu is determined while for sand and silty sands, the internal friction angle φ′ and the relative density Dr are calculated. For φ′, the minimum value obtained between Equation (3) and Equation (4) is adopted. The relative density is determined based on the correlation of Jamiolkowski et al. (2003). Figure 3 presents the correlated strength parameters over depth for the investigated soil profile, all of which are obtained automatically following the ground model definition.
A state parameter-based cavity expansion analysis for interpretation of CPT data in sands
Published in Michael A. Hicks, Federico Pisanò, Joek Peuchen, Cone Penetration Testing 2018, 2018
The measured CPT data is normally interpreted to obtain soil properties, including friction angle, density and elastic parameters. Since the concept of critical state has enabled the significant development of soil constitutive models with consideration of volumetric changes, the critical state parameters are becoming important to geotechnical engineers. Friction angle is correlated to the critical state friction ratio M. The influence of friction angle on the normalised cone tip resistance is examined and presented in Figure 7. Note that this test series keeps the constant initial confining stress with P0 = 500kPa. Based on the aforementioned definition of G0, the stiffness index G0/p0 is directly related to initial specific volume, and thus to initial state parameter with constant p0. The trends in both Qt1 – G0 / p0 and Qt1 – ψ0 spaces show non-linear increases of Qt1 with friction angle.
Cone Penetration Tests
Published in James Fern, Alexander Rohe, Kenichi Soga, Eduardo Alonso, The Material Point Method for Geotechnical Engineering, 2019
James Fern, Alexander Rohe, Kenichi Soga, Eduardo Alonso
CPT is mainly used to determine the sub-surface stratigraphy and to estimate the geotechnical parameters of the soil for geotechnical site characterisation. The results are often directly applied for geotechnical design such as calculation of pile bearing capacity or settlement estimation. CPT measurements depend on the in situ mechanical response of the soil. Robertson [244] suggests the following soil behaviour type classification.Clay-like: typical of fine-grained plastic soils such as clay, in which the penetration occurs in undrained conditions and excess pore pressures are generated and do not have time to dissipate.Sand-like: typical of coarse grained soil such as sand, in which the penetration occurs in drained conditions and excess pore pressures may be generated but quickly dissipate.Transitional: typical of intermediate materials such as silt, sand-clay mixtures, tailings and are characterised by a complex penetration process and often the excess pore pressure partially dissipates during penetration (partially drained conditions).Most of the existing empirical or theoretical correlations between CPT or CPTu measurements and soil properties have been developed for undrained or drained conditions, and are thus inappropriate in intermediate soils. For this reason, it is important to gain a better understanding of the penetration process in these conditions. The problem has been mainly studied experimentally with centrifuge tests, calibration chamber tests, and in situ tests [154,186,218,240,259]. Only a few numerical studies investigated partial drainage in installation problems [123,269,338].
Characterising site investigation performance in multiple-layer soils and soil lenses
Published in Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards, 2021
M. P. Crisp, M. B. Jaksa, Y. L. Kuo
Two commonly-used geotechnical test types are considered: the standard penetration test (SPT) and cone penetration test (CPT) (Bowles 1997). The two tests differ in three ways; sampling cost per metre, sampling frequency with depth, and accuracy. The latter is simulated by applying unit-mean, lognormal random errors with varying COVs, as seen in Table 1, along with other attributes. The test errors are applied in a 3-step process in the following order: random bias per borehole (based on each borehole’s mean), random error per sample, and random global bias (based on the global mean). Testing errors are treated in further detail by Crisp, Jaksa, and Kuo (2019b). Details on the soil model generated from an investigation are given in the methodology overview. In order to examine the effect of these testing inaccuracies, versions of the SPT and CPT without random errors are also assessed. These are referred to as the discrete and continuous tests respectively, and share all attributes with their counterparts other than the added uncertainties.
Feasible packing of granular materials in discrete-element modelling of cone-penetration testing
Published in Geomechanics and Geoengineering, 2018
Nurhan Ecemis, Paulina Bakunowicz
The cone-penetration test (CPT) is an in situ test that has gained worldwide attention because it provides a continuous or near-continuous soil profile. Moreover, it is rapid, repeatable, reliable, and cost-effective when compared to other field tests (Lunne et al. 1997, Mayne 2007). A cone mounted at the end of series of rods is pushed into the ground at a constant penetration rate of 2 cm/s (ASTM D3441). Meanwhile, the independent parameters, including cone-penetration resistance (qc) and friction resistance (fs) are measured (Lunne et al. 1997). The interpretation of measured CPT parameters in highly permeable sands essentially relies on empirical or semi-empirical methods (Mayne 2007). These methods include (1) bearing capacity theories by limit plasticity, such as by Meyerhof (1961), Janbu and Senneset (1974), and Durgunoglu and Mitchell (1975a, 1975b); (2) cavity-expansion theories, such as by Baligh (1975, Vesic (1972), Salgado et al. (1997), and Yu and Mitchell 1998); and (3) steady-state cone-penetration and strain-path methods, such as by Baligh (1985), Houlsby et al. (1985), Teh and Houlsby (1991), and Whittle (1992). Laboratory studies using centrifuge tests (e.g. Bolton and Gui 1993) and calibration-chamber tests (e.g. Houlsby and Hitchmann, 1988, Ghionna and Jamiolkowski 1991) have also been performed to study cone-penetration. Laboratory tests are expensive, and conducting a CPT in the calibration chamber is laborious.
CPT-based method using hybrid artificial neural network and mathematical model to predict the load-settlement behaviour of shallow foundations
Published in Geomechanics and Geoengineering, 2022
Abdelfattah Aouadj, Ali Bouafia
Since a long time, CPT has been used extensively to estimate settlement of shallow foundations on granular soils. Most of the CPT-based methods, which are initiated theoretically or empirically, relate the load-settlement response of shallow foundation to the cone tip resistance by introducing some correction factors. Table 1 presents three traditional methods based on the CPT test where two of them are commonly used in the design of foundations, those of Mayerhof (1956) and Schmertmann (1978). The third is an empirical method was proposed by Mayne, et al. (2018) based on the results of 130 full-scale load test.