Enhanced in Situ Geotechnical Testing for Bridge Foundation Analysis

1997 ◽  
Vol 1569 (1) ◽  
pp. 26-35 ◽  
Author(s):  
Paul W. Mayne ◽  
Chris Dumas
Keyword(s):  
Continuum Theory ◽  
Strain Range ◽  
Small Strain ◽  
Standard Penetration Test ◽  
Engineering Properties ◽  
Engineering Practice ◽  
Time Behavior ◽  
Highly Nonlinear ◽  
Hybrid Devices

Geotechnical analyses of bridge foundations are complex because of the difficulties in addressing the highly nonlinear and anisotropic stress-strain-strength-time behavior of soils, from the nondestructive small-strain range region through to failure conditions. Often engineering practice overrelies on a single test value from soil borings [the standard penetration test (SPT) N-value] for the evaluation of all necessary geotechnical parameters, which is unrealistic. There exists, in fact, a variety of in situ measurement devices for the better definition of soil engineering properties, particularly hybrid devices such as the seismic piezocone and seismic flat dilatometer, as related to foundation applications. The importance of small-strain field stiffness measurements (i.e., shear wave velocity) is discussed and illustrated with two case studies involving the axial response of drilled shaft and driven pile foundations. The examples are reviewed within the context of elastic continuum theory but may be applied similarly for use in site-specific determinations of nonlinear spring constants and well-known t-z, p-y, or q-z curves, or all three.

scholarly journals Enhancing Constitutive Models for Soils: Adding the Capability to Model Nonlinear Small Strain in Shear

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
S. Seyedan ◽  
W. T. Sołowski
Keyword(s):  
Yield Surface ◽  
Constitutive Models ◽  
Strain Range ◽  
Small Strain ◽  
Deviatoric Stress ◽  
Triaxial Tests ◽  
Engineering Practice ◽  
Model Parameters ◽  
Highly Nonlinear ◽  
Strain Relationship

The deviatoric stress-deviatoric strain relationship in soils is highly nonlinear, especially in the small strain range. However, the constitutive models which aim to replicate the small strain nonlinearity are often complex and rarely used in geotechnical engineering practice. The goal of this study is to offer a simple way for updating the existing constitutive models, widely used in geotechnical practice, to take into account the small strain shear modulus changes. The study uses an existing small strain relationship to derive a yield surface. When the yield surface is introduced to an existing soil model, it enhances the model with the nonlinear deviatoric stress-deviatoric strain relationship in the small strain range. The paper also gives an example of such a model enhancement by combining the new yield surface with the Modified Cam Clay constitutive model. The validation simulations of the undrained triaxial tests on London Clay and Ham River sand with the upgraded constitutive models replicate the experiments clearly better than the base models, without any changes to existing model parameters and the core source code associated with the base model.

scholarly journals The comparative analysis of the seismic test results performed using the cross-hole and down-hole methods in terms of test reliability and efficiency

2018 ◽  
Vol 66 ◽  
pp. 01021
Author(s):  
Wojciech Tschuschke ◽  
Sławomir Gogolik ◽  
Maciej Kroll ◽  
Krzysztof Janicki
Keyword(s):  
Comparative Analysis ◽  
Small Strain ◽  
Test Reliability ◽  
Engineering Practice ◽  
Test Results ◽  
In Situ Tests ◽  
The Cross ◽  
Seismic Tests

Seismic tests are becoming more and more meaningful in modern geoengineering since they allow precise assessment of changes in the analyzed profile of soil deformation parameters at very small strain. The engineering practice generally uses two methods for such kinds of tests: reference cross-hole test and commercial down-hole method. The costs of implementation of this kind of research and the reliability of the results obtained along with any additional benefits from the type of the selected testing technique are not without significance. Seismic measurements for which comparative analysis was performed were carried out in a strongly anisotropic materials base of a tailings. The results of tests conducted with a standard cross-hole method were compared with those conducted using the down-hole method, in which the seismic piezocone (SCPTU) and seismic dilatometer (SDMT) were used. Test results have shown that in terms of assessment of their credibility, there were no fundamental differences in the quality of the recorded signals. It has been pointed out, however, that there are many advantages to penetration in situ tests, which complement identification of subsoil structure with many crucial elements that cannot be achieved using the cross-hole method.

Assessment of the range of variation of Nγ from 60 estimation methods for footings on sand

2013 ◽  
Vol 50 (7) ◽  
pp. 793-800 ◽  
Author(s):  
Edgar Giovanny Diaz-Segura
Keyword(s):  
Friction Angle ◽  
Standard Penetration Test ◽  
Estimation Methods ◽  
Penetration Test ◽  
In Situ Tests ◽  
Vertical Loading ◽  
Simplified Method ◽  
Bearing Capacity Factor ◽  
Range Of Variation

The range of variation of the bearing capacity factor, Nγ, was assessed using 60 estimation methods for rough footings on sand subjected to static vertical loading. The influence on the Nγ values of the use of correlations for the estimation of the friction angle, [Formula: see text], derived from in situ tests was also assessed. The analysis shows a marked dependency on the methods used to determine Nγ, showing differences for the same [Formula: see text] values of up to 267% between estimated values. Uncertainty in the estimation of [Formula: see text], due to the use of correlations with in situ tests, leads to a range of variation for Nγ higher than that seen using the 60 estimation methods. Finally, given the regular use of the in situ standard penetration test (SPT) on sands, and based on a series of analyses using finite elements, a simplified method in terms of the SPT N-values is proposed for estimation of Nγ in footings on sands.

scholarly journals NUMERICAL MODELLING OF THE SOIL BEHAVIOUR BY USING NEWLY DEVELOPED ADVANCED MATERIAL MODEL

2017 ◽  
Vol 57 (1) ◽  
pp. 58-70 ◽  
Author(s):  
Jan Veselý
Keyword(s):  
Numerical Modelling ◽  
Plastic Material ◽  
Material Model ◽  
Small Strain ◽  
Theoretical Background ◽  
Linear Elastic ◽  
In Situ Data ◽  
Modified Cam Clay ◽  
Soil Behaviour

This paper describes a theoretical background, implementation and validation of the newly developed Jardine plastic hardening-softening model (JPHS model), which can be used for numerical modelling of the soils behaviour. Although the JPHS model is based on the elasto-plastic theory, like the Mohr-Coulomb model that is widely used in geotechnics, it contains some improvements, which removes the main disadvantages of the MC model. The presented model is coupled with an isotopically hardening and softening law, non-linear elastic stress-strain law, non-associated elasto-plastic material description and a cap yield surface. The validation of the model is done by comparing the numerical results with real measured data from the laboratory tests and by testing of the model on the real project of the tunnel excavation. The 3D numerical analysis is performed and the comparison between the JPHS, Mohr-Coulomb, Modified Cam-Clay, Hardening small strain model and monitoring in-situ data is done.

Judgement Method for Surrounding Rock Stability of Guanjiao Tunnel Based on Catastrophe Theory

2011 ◽  
Vol 90-93 ◽  
pp. 2307-2312 ◽  
Author(s):  
Wen Jiang Li ◽  
Su Min Zhang ◽  
Xian Min Han
Keyword(s):  
Plastic Strain ◽  
Catastrophe Theory ◽  
Soft Rock ◽  
Surrounding Rock ◽  
In Situ Monitoring ◽  
Engineering Practice ◽  
Stability Of Surrounding Rock ◽  
The Stability ◽  
Rock Tunnel

The stability judgement of surrounding rock is one of the key jobs in tunnel engineering. Taking the Erlongdong fault bundle section of Guanjiao Tunnel as the background, the stability of surrounding rock during construction of soft rock tunnel was discussed preliminarily. Based on plastic strain catastrophe theory, and combining numerical results and in-situ data, the limit displacements for stability of surrounding rock were analyzed and obtained corresponding to the in-situ monitoring technology. It shows that the limit displacements obtained corresponds to engineering practice primarily. The plastic strain catastrophe theory under unloading condition provides new thought for ground stability of deep soft rock tunnel and can be good guidance and valuable reference to construction decision making and deformation managing of similar tunnels.

scholarly journals CHARACTERIZING A TROPICAL SOIL VIA SEISMIC IN SITU TESTS

2019 ◽  
Vol 37 (3) ◽  
pp. 263
Author(s):  
Breno Padovezi Rocha ◽  
Heraldo Luiz Giacheti
Keyword(s):  
Shear Modulus ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Soil Profile ◽  
Site Investigation ◽  
Tropical Soil ◽  
Engineering Properties ◽  
Foundation Engineering

ABSTRACT. The shear wave velocity (Vs) is an important geotechnical parameter to be used in dynamic problems (e.g. earthquakes and vibration problems) as well as in static deformation analysis such as excavations and foundation engineering design. There are several in situ seismic tests to determine Vs such as the crosshole and the downhole techniques, as well as hybrid tests (e.g. seismic dilatometer – SDMT). This paper presents crosshole, downhole and SDMT tests carried out in a typical tropical soil profile from Brazil. Advantages and limitations regarding the test procedures and interpretation are briefly presented and differences observed among Vs determined by these techniques are discussed. Shear wave velocities (Vs) estimated from the crosshole, downhole and SDMT tests ranging from 194 to 370 m/s. The shear wave velocity suggests that the experimental site could be divided into two strata, which are in agreement with soil profile description. The maximum shear modulus (G0) calculated from the Vs by theory of elasticity can be used to show the investigated tropical soil is a typical unusual geomaterial. This article also emphasizes that the SDMT is a useful test for site investigation since it allows a great means for profiling geostratigraphy and soil engineering properties during routine site investigation as well as for dynamics problems. Keywords: shear wave velocity, maximum shear modulus, crosshole, downhole, SDMT.RESUMO. A velocidade de onda cisalhante (Vs) é um parâmetro geotécnico empregado em análises dinâmicas (terremotos e problemas de vibração), bem como em análises estáticas (escavações e projeto de fundações). Existem vários ensaios sísmicos de campo para a determinação de Vs, entre eles as técnicas crosshole e downhole, e os ensaios híbridos (por exemplo, dilatômetro sísmico – SDMT). Este artigo apresenta os ensaios crosshole, downhole e SDMT realizados em um perfil típico de solo tropical do Brasil, as vantagens e limitações dos procedimentos de ensaio e de interpretação são brevemente apresentadas, e as diferenças observadas entre os valores de Vs determinados pelas diferentes técnicas são discutidas. Os perfis de Vs determinados pelas diferentes técnicas variaram de 194 a 370 m/s. A velocidade da onda cisalhante sugere que o campo experimental investigado pode ser dividido em dois horizontes, os quais estão de acordo com a descrição do perfil do solo estudado. O módulo de cisalhamento máximo (G0), calculado a partir de Vs pela teoria da elasticidade, pode ser utilizado para demonstrar o comportamento não convencional do solo investigado. Este artigo também enfatiza que o SDMT é um ensaio geotécnico útil para a investigação geotécnica do subsolo, uma vez que permite a definição do perfil estratigráfico e a estimativa de parâmetros estáticos e dinâmicos de um projeto.Palavras-chave: velocidade de onda cisalhante, módulo de cisalhamento máximo, crosshole, downhole, SDMT.

scholarly journals Performance of electrokinetic treatment of fine-grained problematic soils

2021 ◽  
Vol 9 (4B) ◽  
Author(s):  
Abiola Ayopo Abiodun ◽  
◽  
Zalihe Nalbantoglu ◽  
Keyword(s):  
Low Voltage ◽  
Soil Depth ◽  
Experimental Tests ◽  
Interactive Effects ◽  
Engineering Properties ◽  
Laboratory Model ◽  
Fine Grained ◽  
Electrode Length ◽  
Problematic Soils

Electrokinetic (EK) treatment is an innovative, cost-effective in situ ground modification technology. The EK treatment uses a combination of low-voltage direct-current, electrodes, and ionic solutions across problematic soil to improve the ground conditions. This study aims to model the effect of changing electrode length (le) on the performance of the EK treatment on the engineering properties of fine-grained problematic soils. The consideration of the changing electrode lengths (le), varying soil depths (ds), and lengthwise anode to cathode distances (dA↔E), in the soil block samples, is in the form of the laboratory model test tank. The significant performance of the experimental tests was with changing electrode lengths of 0.25le (7.5 cm), 0.50le (15.0 cm), 0.75le (22.5 cm), and 1.0le (30.0 cm). The study analyzed the test data obtained from the Atterberg limit and one-dimensional swelling tests at different extraction points of the EK treated soils in the test tanks. Furthermore, the study carefully analyzed the effect of changing electrode length (le) on the performance of the EK treatment. The results of the Design of Experiment (DOE) model analysis revealed that the effect of changing electrode length (le) on the plasticity index (PI), and swelling potential (SP) of the EK treated soils, was significant. For a specific soil depth (ds), the electrode lengths (le) of 0.50le and 0.75le were significantly effective in reducing the PI, and the SP of the EK treated soils. Unlike other studies in the literature, the use of DOE analysis in the present study enabled the detection of the significant input factors and their interactive effects on the PI and the SP, thus, enabling the practicing engineers to navigate accurate design models for large in situ applications.

Investigation of Small- to Large-Strain Moduli Correlations of Rockfill Materials – Application to Romaine-2 Dam

2021 ◽  
Author(s):  
Ibrahim Lashin ◽  
Michael Ghali ◽  
Marc Smith ◽  
Daniel Verret ◽  
Mourad Karray
Keyword(s):  
Large Strain ◽  
Deformation Behaviour ◽  
Numerical Data ◽  
Small Strain ◽  
Hyperbolic Model ◽  
Large Strains ◽  
Initial Modulus ◽  
Rockfill Materials ◽  
Materials Used

Establishment of a relationship between the shear wave velocity (Vs) and other geotechnical parameters of rockfill soils at large strains (oedometer modulus, Moedo, tangent modulus, Et) is considered a significant step towards more precise modelling of earth-structure deformation behaviour. In this study, four samples of different gradations, reconstituted from the rockfill materials used in the construction of the Romaine-2 dam, were experimented to correlate the small strain to large strain moduli. Development of Moedo and Vs with consolidation was measured in the laboratory using the piezoelectric ring-actuator technique (P-RAT) incorporated in a large oedometer. Therefore, a correlation between Moedo and small strain shear modulus Go was proposed. Moreover, numerical simulations were performed based on the Duncan-Chang hyperbolic model to correlate the Vs to Duncan-Chang initial modulus(Ei). Based on the experimental and numerical data, a relation between Ei and Vs of the tested rockfill has been established. Verification studies were also carried out on in-situ measurements during Romaine-2 dam construction, proofing the ability of the proposed relationships to predict Ei related to the minor principal stress (σ3) from in-situ Vs measurement. The proposed correlations could help the geotechnical designers to estimate accurately the deformation of rockfill materials from in-situ Vs measurement.

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