Cone Penetration Measurements Research Articles

Coupled hydromechanical modelling of cone penetration in layered liquefiable soils

Soil layering modifies cone penetration measurements when the cone is close to layer boundaries. Transition zone and thin-layer effects appear, complicating interpretation. To help identify the mechanisms underlying transition and thin-layer effects, several series of realistic simulations of cone penetration in layered soils are presented. Cone penetration tests are simulated using fully coupled hydromechanical models solved with the particle finite-element method. A constitutive model capable of representing flow liquefaction is employed to explore the effect of embedded layers with different initial state parameter and/or hydraulic conductivity than the host soil. Sensing and development distances for tip resistance and excess pore pressure are examined, as well as the effect of layering on dissipation tests. It is shown how distortion of layer interfaces by the cone is captured, explaining several characteristics of pore pressure and dissipation records. It is also shown that looser soil states may be hidden in the tip resistance trace by simultaneous changes in soil hydraulic conductivity.

Evaluation of Flow Liquefaction Susceptibility in Non-Plastic Silty Soils Using the Seismic Cone

The state parameter allows the evaluation of the in situ state of soils, which can be particularly useful in tailings impoundments where flow liquefaction is the most common failure model. Positive state parameter values characterize a contractive response during shearing and, for non-plastic soils, can indicate flow liquefaction susceptibility. This paper presents a methodology to classify and estimate the state parameter (Ψ) for non-plastic silty soils based on seismic cone penetration measurements. The method expands on a previous methodology developed for sands that use the ratio of the small strain shear modulus and the cone tip resistance G0/qt for classification and Ψ assessment. For non-plastic silty soils, drainage conditions during cone penetration must be accounted for and are used to allow soil classification and correct the cone tip resistance. An empirical formulation is proposed to correct qt for partial drainage measurements and predict Ψ for non-plastic silty soils. Mining tailings results of in situ and laboratory tests were used to validate the proposed methodology producing promising responses. The Ψ value estimated through the proposed methodology are in the range of those obtained from laboratory tests, indicating an adequate prediction of behavior for non-plastic silty soils.

Cone penetration measurements in oil-contaminated sand stabilized by lateritic soil and potential usage in concrete mix

Oil-contaminated soils are generally considered inadequate for structural concrete and highway construction. However, soils continue to be contaminated by oil and various methods of stabilization have been attempted. This paper documents a series of experiments carried out using the electronic cone penetration test (CPTu) to investigate the strength behaviour of a poorly graded sand (SP) when contaminated by oil and subsequently stabilized by a lateritic soil (LS). When contaminated with oil, the sand lost some of its strengths as indicated by the decreased cone resistance (qc) and sleeve friction (fs) values, which reduced further when the oil content (OC) was increased. When subsequently stabilized with the LS, the lost strengths recovered and continued to enhance with additional LS used. Based on the evaluation of results associated with qc, for a contaminated sand with up to 8% OC, the stabilization that would return the original uncontaminated sand’s strength was one with 20% LS content. Moreover, the stabilization was more efficient for sand with lesser OC than with more OC. Similar results as those associated with qc were found when the bases for evaluation were the internal friction angle (ϕ), standard penetration number (SPTN), and Young’s modulus (Es), since these parameters were all derived from qc. Based on the evaluation of results associated with fs, unlike in the case of qc, a blanket LS content of 15% was capable of returning the original uncontaminated sands’ value even for a sample with 10% OC. The morphologies of contaminated and stabilized sands have shown revealing results of breakdown and rejuvenation through scanning electron microscopy (SEM). Moreover, based on compressive and flexure concrete tests it was observed that the oil-contaminated sand, after stabilizing it with lateritic soil, should be useable as a fine aggregate in rural infrastructures and low strength concrete applications such as Sandcrete block and sidewalks, rather than being neglected.

Classification and State-Parameter Assessment of Granular Soils Using the Seismic Cone

AbstractThis paper presents a methodology developed for soil classification and state parameter (ψ) evaluation for granular soils based on seismic cone penetration measurements. The method uses a t...

Effect of bio-cementation on geophysical and cone penetration measurements in sands

Microbially induced calcite precipitation (MICP) is a potentially environmentally conscious ground improvement method that can improve the engineering properties of granular soils through the precipitation of calcite. In this study, an experiment involving two 1.7 m diameter tank specimens was completed to investigate the effect of bio-cementation on cone penetrometer and geophysical measurements in sands. Following nonuniform bio-cementation treatments, specimens achieved calcite contents ranging from 0.5% to 5.3% by mass, shear wave velocity (Vs) values between 131 and 967 m/s, and mid-depth cone penetration resistances (qc) ranging between 3.6 and 32.1 MPa. At calcite contents exceeding 5.0%, qcand Vsimprovements were as high as 527% and 686%, respectively. Although cone penetration resistance, sleeve friction, and friction ratio measurements exhibited limited sensitivity to bio-cementation at calcite contents of less than 3.0%, Vsmeasurements successfully detected bio-cementation at calcite contents near 1.0%. When qcand Vsmeasurements were compared at similar locations, increases in an empirical parameter (KG) enabled improved detection of bio-cementation at calcite contents near 0.5%. Large increases in normalized tip resistances (Qtn) and small decreases in normalized friction ratios (Fr) with increasing bio-cementation resulted in cemented materials plotting near and within the gravelly sand and sand-like dilative soil behavioral type regions using two soil behavior type (SBT) charts.

Underpinning works under existing shallow foundations in Blaj ‐ Romania using Springsol® technology

AbstractRomanian branch of Soletanche Bachy (SB) together with SB Group expertise, carried out underpinning works at an existing factory located in Blaj. After being built in 2007 on poor soil conditions, the structure has continuously developed serious settlements. Various solutions for remediation were studied, but the most suitable was ‐ Springsol® technology. This method is SB's soil mixing technique: it allows construction of soil‐cement columns with small diameter drilling rigs which can fit inside existing buildings. 27 Springsol® columns with d=400 mm were executed under existing foundations. The main works followed a trial carried out on a plot close to the factory. The objective was to validate the construction parameters and measure their characteristics. Dynamic cone penetration measurements were performed around the columns before and after their construction, along with a large number of later excavated trial columns injected with various parameters enabled finding the right response to meet the client’ s expectations and demonstrate the effectiveness of the proposed solution.

Continuum cavity expansion and discrete micromechanical models for inferring macroscopic snow mechanical properties from cone penetration data

AbstractDigital cone penetration measurements can be used to infer snow mechanical properties, for instance, to study snow avalanche formation. The standard interpretation of these measurements is based on statistically inferred micromechanical interactions between snow microstructural elements and a well‐calibrated penetrating cone. We propose an alternative continuum model to derive the modulus of elasticity and yield strength of snow based on the widely used cavity expansion model in soils. We compare results from these approaches based on laboratory cone penetration measurements in snow samples of different densities and structural sizes. Results suggest that the micromechanical model underestimates the snow elastic modulus for dense samples by 2 orders of magnitude. By comparison with the cavity expansion‐based model, some of the discrepancy is attributed to low sensitivity of the micromechanical model to the snow elastic modulus. Reasons and implications of this discrepancy are discussed, and possibilities to enhance both methodologies are proposed.

Reconstructing Early Neolithic Paleogeography: EMI‐Based Subsurface Modeling and Chronological Modeling of Holocene Peat below the Lower Scheldt Floodplain in NW Belgium

Well‐preserved prehistoric landscapes and sites have been found, buried deeply below the Holocene peat or floodplain deposits of “Waasland Scheldt polders.” During the mid‐to‐late Holocene, Late Weichselian (river) dunes within the floodplain and river flanks were favored locations for Final Early Neolithic occupation. Available living space was determined by the dune topography and elevation of the peat at that time. Therefore, an elevation model of the peat base was created using multireceiver electromagnetic induction (EMI) survey data. Electrical conductivity data of a dune were collected and 1D inverted within a three‐layered soil model with variable electrical conductivity of the top layer and variable depth to the base of the middle layer (i.e., the peat). The modeled peat base depth was calibrated and validated, and eventually replaced by depth data from coring and cone penetration measurements wherever depth modeling from inverting the EMI measurements proved inaccurate. Using the resulting peat base elevation model, a paleogeographic map at the time of the modeled end date of Mesolithic–Neolithic transitional Swifterbant Culture sites nearby was created by chronologically modeling the peat elevation at that time. The developed paleogeographic mapping methodology can be used for subsequent archaeological prospection by core sampling or to contextualize excavated sites.

Experimental Evaluation of Earthworm and Plant Root Soil Penetration–Cavity Expansion Models Using Cone Penetrometer Analogs

Core Ideas Analytic model for penetration–expansion forces closely agrees with measurements. Measurements used cones with size geometry similar to earthworms and roots. Soil parameters and constraints for root and earthworm bioturbation are estimated. To form new burrows, earthworms need to consume 0.3 kg C m−2 yr−1. Recent mechanical models of soil penetration by earthworms and plant roots based on penetration‐cavity expansion were tested using cone penetration measurements at scales compatible with the sizes of earthworms and plant roots. Measurements using different cone radii (1.0–2.5 mm) and cone semi‐apex angles (15–30°) were obtained for a range of soils and water contents at highly resolved penetration forces and constant insertion rates. The cone penetration measurements were interpreted using independently determined soil mechanical parameters and yielded good agreement with predictions from an analytical mechanical model. Experimental confirmation of penetration force predictions supports estimates of energy costs associated with soil bioturbation that vary with soil hydration status and mechanical characteristics. Effects of soil friction and axial compaction were assessed by comparing the results from conventional and recessed cones (to eliminate soil–shaft friction). The study provides new insights into quantitative soil bioturbation processes and expands predictive capabilities of the mechanics and energetics of earthworm activity and root zone dynamics related to soil structure development.

Cone penetration data classification with Bayesian Mixture Analysis

ABSTRACTThis paper presents an application of the Bayesian Mixture Analysis (BMA) to deal with the classification of spatially variable soil data from the cone penetration test. The cone penetration data classification postulates a problem where a set of cone penetration measurements is used to identify “hidden or unobserved” soil classes. The problem is formulated as an incomplete-data Gaussian mixture where the observed data are defined by the natural logarithm-transformed values of the normalized friction and the normalized cone resistance, while the soil classes to be identified are considered as hidden data. The solution for the incomplete-data problem which consists of class-dependent mixture probabilities and Gaussian distribution parameters is defined in a Bayesian framework. The implementation of conjugate priors for the Gaussian mixtures enables an efficient sampling of the posterior parameters by the Gibbs algorithm of the Markov Chain Monte Carlo method. When compared to the well-established Robertson classification charts, the BMA formulation has an advantage due to the Bayesian framework which enables the definition of soil classes through mixture priors, class-dependent posterior parameter estimates, and a probabilistic soil classification. The presented approach is applied to the cone penetration data from the Sheringham Shoal Offshore Wind Farm site.

Design and characterization of GRC-1: A soil for lunar terramechanics testing in Earth-ambient conditions

Earth experiments must be carried out on terrain that deforms similarly to the lunar terrain to assess the tractive performances of lunar vehicles. Most notably, terrain compaction and shear response underneath the lunar vehicle wheels must represent that of the Moon. This paper discusses the development of a new lunar soil simulant, Glenn Research Center lunar soil simulant #1 (GRC-1), which meets this need. A semi-empirical design approach was followed in which the soil was created by mixing readily available manufactured sands to a particle size distribution similar to the coarse fraction of lunar soil. By varying terrain density, a broad range of in situ cone penetration measurements collected by the Apollo mission astronauts can be replicated. An extensive set of characterization data is provided in this article to facilitate the use of this material. For reference, the index and geotechnical properties of GRC-1 are compared to the lunar soil and existing lunar soil simulants.

Cone-based electrical resistivity tomography

Determining the 3D spatial distribution of subsurface properties is a challenging, but critical, part of managing the cleanup of contaminated sites. We have developed a minimally invasive technology that can provide information about the 3D distribution of electrical conductivity. The technique, cone-based electrical resistivity tomography (C-bert), integrates resistivity tomography with cone-penetration testing. Permanent current electrodes are emplaced in the subsurface and used to inject current into the subsurface region of interest. The resultant potential fields are measured using a surface reference electrode and an electrode mounted on a cone penetrometer. The standard suite of cone penetration measurements, including high-resolution resistivity logs, are also obtained and are an integral part of the C-bert method. C-bert data are inverted using an inexact Gauss-Newton algorithm to produce a 3D electrical conductivity map. A majorchallenge with the inversion is the large local perturbation around the measurement location, due to the highly conductive cone. As the cone is small with respect to the total model space, explicit modeling of the cone is cost prohibitive. We have developed a rapid method for solving the forward model which uses iteratively determined boundary conditions (IDBC). This allows us to generate a computationally feasible, preinversion correction for the cone perturbation. We assessed C-bert by performing a field test to image the conductivity structure of the Kidd 2 site near Vancouver, British Columbia. A total of nine permanent current electrodes were emplaced and five C-bert data sets were obtained, resulting in 6516 data points. These data were inverted to obtain a 3D conductivity image of the subsurface. Furthermore, we demonstrated, using a synthetic experiment, that C-bert can yield high quality electrical conductivity images in challenging field situations. We conclude that C-bert is a promising new imaging technique.

Soil strength and soil pore characteristics for direct drilled and ploughed soils

Direct drilling has often been reported to increase density and strength and to affect pore continuity and tortuosity of the upper soil layers. In this study these aspects were studied for three texturally differing soils 4–6 years after initiation of continuous trials with direct drilling and mouldboard ploughing. The soils studied were a coarse sandy soil (Korntved, 5% clay), a sandy loam (Ballum, 8% clay) and a silty loam (Højer, 19% clay). The crop rotation at Korntved was spring barley and winter rye while at Ballum and Højer it was spring barley and winter wheat. Both crops were grown every year. All fields had been mouldboard ploughed for decades prior to the trial period. The ploughed treatment (PL) was imposed in the autumn and the seedbed preparation and drilling were performed with an S-tined seedbed harrow and a traditional drill. The direct drilled (DD) treatment received no tillage other than the drilling which was performed by a triple-disc drill. Straw and stubble were burned. In the 4th, 5th and 6th years of the trial period, minimally disturbed soil cores were taken from the 4 to 8, 14 to 18 and 24 to 28 cm depths, i.e. two horizons above the ploughing depth of 20 cm, and one horizon below this depth. Longer cores were sampled in the 18–27 cm depth in order to include this transition layer. Furthermore, in the 4th year of the trial period shear strength was measured in the field at 2-week intervals in the spring with a vane shear tester in the two upper layers mentioned. All samplings and measurements took place in the field grown with spring barley. In the laboratory air diffusivity and air permeability were measured at field-sampled water content and again when the soil cores were drained to a matric potential of −100 hPa. Cone penetration resistance was measured with a 2 mm diameter penetrometer. Separate core samples from the 14 to 18 cm depth of the Korntved and Højer soils were used for estimating soil cohesion and soil internal friction by a shear annulus method at field-sampled water content. For all soils, DD increased soil bulk density in the two upper soil layers. The shear vane tester also generally estimated higher shear strength for the DD compared to the PL treatment. The shear annulus measurements in the laboratory revealed no differences between tillage treatments for the Korntved soil, while a tendency of higher cohesion and internal soil friction was found for the DD treatment on the Højer soil. The cone penetration measurements indicated a stronger top-soil and fewer high-strength soil elements in the 24–28 cm horizon for the DD than for the PL treatment. Generally the DD treatment had lower volume of macropores (i.e. pores>30 μm ) in the 4–8 and 14–18 cm depths than the PL treatment. This was reflected in reduced air diffusivities and air permeabilities for these horizons. An exception was the 14–18 cm depth of the Ballum soil, where increased air diffusivity and air permeability was measured at field-sampled water content. Continuity indices calculated from air diffusivity and air permeability measurements showed that the DD soil from the 4 to 8 and 14 to 18 cm depths had less continuous and more tortuous macropores than the ploughed soil.

Consumer acceptance of fatty spreads

The effect of consumer trends on the purchase of reduced fat products in general and fatty spreads in particular are discussed. A variety of fatty spreads with fat levels ranging from 20 to 80% were assessed by cone penetration measurements and sensory assessments. The results indicated that butter had poor spreadability characteristics at 5° and 10°, while mechanically worked butter (spreadeasy butter) gave a significantly different texture profile, as measured by the Instron Model 1000. This butter type was assessed as being spreadable at 10° by the sensory panelists and by cone penetrometry. Comparable values of hardness were obtained using data obtained by cone penetrometry and texture profile analysis from the Instron. Low fat spreads (fat levels 25–39%) produced desirable spreadability characteristics using both objective and subjective methods of assessment. Sunflower oil‐based spreads and very low fat spreads, i.e. ≦ 25% fat, were assessed as being soft and oily. The results overall indicated that the use of a cone penetrometer and the subsequent calculation of a yield value gave, using Haighton's seven‐point scale, a good indication of spreadability characteristics.

Strength of C 3A paste containing gypsum and CaCl 2

A study has been made of the strength of 3CaO.Aℓ 2O 3 and 3CaO.Aℓ 2O 3 + gypsum pastes as well as of the influence of the admixture CaCℓ 2 on these pastes. The methods employed were microhardness indentation and cone penetration. With 16 per cent CaCℓ 2 added to the 3CaO.Aℓ 2O 3 paste a significant gain in strength was obtained after 3 months, while an 8 per cent CaCℓ 2 addition to the 3CaO.Aℓ 2O 3 + gypsum system gave the highest strength at the same age. Morphological changes in the pastes were found to be related to changes in hardness. From a comparison of the two methods it was concluded that cone penetration measurements are useful up to a certain hardness level.