Investigation of bearing capacity factor of T-bar penetrometer at shallow depths in clayey soils

2013 ◽  
Vol 1 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Márcio S.S. Almeida ◽  
José Renato M.S. Oliveira ◽  
Khader I. Rammah ◽  
Pablo C. Trejo
Keyword(s):  
Shear Strength ◽  
Offshore Structures ◽  
Analytic Solutions ◽  
Undrained Shear Strength ◽  
Soil Parameters ◽  
Geotechnical Centrifuge ◽  
Fine Grain ◽  
Centrifuge Tests ◽  
Undrained Strength ◽  
Undrained Shear

The T-bar penetrometer is normally used in both in-situ and on the centrifuge to establish profiles of the undrained shear strength of fine-grain soils. However, adequate measurement of the undrained shear strength at shallow depths requires understanding the failure mechanism at these depths. For onshore and offshore structures such as pipelines, the assessment of soil parameters, in particular the undrained shear strength at shallow depth can be very critical to achieve both efficient and economic design. However, this requires the evaluation of the value of T-bar bearing factor (Nb) corresponding to both shallow and very shallow depths. This paper describes a series of geotechnical centrifuge tests undertaken using three different sizes of the T-bar penetrometer on two types of clayery soil. The results of the undrained strength obtained from each T-bar were compared with the results obtained from the bigger T-bars. The curves that describes the variation of the T-bar factor (Nb) versus the penetration depth were established from the comparison of all results obtained from the three different sizes of the T-bar. The results of (Nb) obtained in this study were compared with results obtained from both numerical and analytic solutions proposed in the literature. Generally, the experimental data obtained in this study presented Nb values higher than those predicted by others authors for all H/D ratios. However, the comparison indicates that the Nb values obtained in this study showed relatively reasonable agreement with those values obtained from the literature by adopting a non-homogenous strength profile.

scholarly journals A Random Forest Model for the Prediction of Spudcan Penetration Resistance in Stiff-Over-Soft Clays

2020 ◽  
Vol 27 (4) ◽  
pp. 130-138
Author(s):  
Pan Gao ◽  
Zhihui Liu ◽  
Ji Zeng ◽  
Yiting Zhan ◽  
Fei Wang
Keyword(s):  
Shear Strength ◽  
Random Forest ◽  
Penetration Resistance ◽  
Undrained Shear Strength ◽  
Soil Parameters ◽  
Good Prediction ◽  
Resistance Profile ◽  
Soft Clays ◽  
Centrifuge Tests ◽  
Undrained Shear

AbstractPunch-through is a major threat to the jack-up unit, especially at well sites with layered stiff-over-soft clays. A model is proposed to predict the spudcan penetration resistance in stiff-over-soft clays, based on the random forest (RF) method. The RF model was trained and tested with numerical simulation results obtained through the Finite Element model, implemented with the Coupled Eulerian Lagrangian (CEL) approach. With the proposed CEL model, the effects of the stiff layer thickness, undrained shear strength ratio, and the undrained shear strength of the soft layer on the bearing characteristics, as well as the soil failure mechanism, were numerically studied. A simplified resistance profile model of penetration in stiff-over-soft clays is proposed, divided into three sections by the peak point and the transition point. The importance of soil parameters to the penetration resistance was analysed. Then, the trained RF model was tested against the test set, showing a good prediction of the numerical cases. Finally, the trained RF was validated against centrifuge tests. The RF model successfully captured the punch-through potential, and was verified using data recorded in the field, showing advantages over the SNAME guideline. It is supposed that the trained RF model should give a good prediction of the spudcan penetration resistance profile, especially if trained with more field data.

Determination of the consistency limits of soils by the fall cone test

1986 ◽  
Vol 23 (2) ◽  
pp. 241-246 ◽  
Author(s):  
Y. Wasti ◽  
M. H. Bezirci
Keyword(s):  
Shear Strength ◽  
Key Words ◽  
Water Content ◽  
Strength Criterion ◽  
Undrained Shear Strength ◽  
Wide Range ◽  
Undrained Strength ◽  
Content Range ◽  
Undrained Shear

The liquid and plastic limits for a variety of natural and artificial soils covering a wide range of plasticity, as determined by the Casagrande method and the fall cone test and based on a strength criterion, were compared. To check the validity of the strength criterion, the undrained shear strength of these soils has been determined with a laboratory vane over the water content range between these limits. A limited comparison of the undrained strength values obtained from the vane test and fall cone test is also given. Key words: Atterberg limits, consistency, fall cone, laboratory vane, shear strength.

Reconsideration of case histories for estimating undrained shear strength in sandy soils

1999 ◽  
Vol 36 (5) ◽  
pp. 907-933 ◽  
Author(s):  
C E (Fear) Wride ◽  
E C McRoberts ◽  
P K Robertson
Keyword(s):  
Shear Strength ◽  
Sandy Soils ◽  
Standard Penetration Test ◽  
Undrained Shear Strength ◽  
Soil Liquefaction ◽  
Penetration Test ◽  
Case Histories ◽  
Original Case ◽  
Undrained Strength ◽  
Undrained Shear

When sandy soils respond in a strain-softening manner to undrained loading, an estimation of the resulting undrained shear strength (Su) is required to determine the potential for flow liquefaction at a given site. One of the most commonly used methods for estimating the undrained strength of liquefied sand is an empirical standard penetration test (SPT) based chart (originally proposed by H.B. Seed), which was developed using a number of case histories. The original interpretations of these case histories are viewed by many workers and regulatory agencies as the most authoritative measure of the liquefied strength of sand. Consequently, in comparison, other less conservative methods are generally held in an unfavourable light. This paper reexamines the original database of case histories in view of some more recent concepts regarding soil liquefaction. The objectives of this paper are to explore and reassess the issues involved in the original assessment and to offer alternative views of the case records. The conclusions presented here indicate that alternative explanations of the liquefied strength of sand are not inconsistent with the original case histories. Key words: sandy soils, soil liquefaction, undrained strength, standard penetration test (SPT).

Landslide history in a Tertiary sedimentary basin in the Quaternary in Japan

1991 ◽  
Vol 7 (1) ◽  
pp. 671-677
Author(s):  
S. Okusa ◽  
N. Takahama ◽  
Y. Fujita
Keyword(s):  
Shear Strength ◽  
Sedimentary Basin ◽  
Undrained Shear Strength ◽  
Climatic Conditions ◽  
History Of ◽  
Undrained Strength ◽  
Japanese Islands ◽  
Undrained Shear ◽  
Present Activity ◽  
Drained Shear Strength

AbstractThe landslide activities in the Quaternary of the Japanese Islands have been controlled by active neotectonic movements and humid climatic conditions. Most of the present active landslides in Cenozoic muddy sediment in the Japanese Islands occur in the ancient landslides site. In the Musigame landslides site in the Cenozoic Niigata sedimentary basin, the present active landslides are concentrated along the fissures and cracks in the ancient primary landslide blocks. The initial failure of the primary Musigame landslides might have occurred in the mudstone with the intact undrained shear strength and the retrogressive failures with a combination of the intact undrained shear strength and residual undrained strength. Secondary and presently active landslides have occurred in the previously disturbed mudstone in accordance with the residual drained shear strength. The analysis of the occurrence, movement and history of the primary and secondary landslides is essential to understand the present activity of landslide.

Modeling piezocone cone penetration (CPTU) parameters of clays as a multivariate normal distribution

2014 ◽  
Vol 51 (1) ◽  
pp. 77-91 ◽  
Author(s):  
Jianye Ching ◽  
Kok-Kwang Phoon ◽  
Chih-Hao Chen
Keyword(s):  
Shear Strength ◽  
Normal Distribution ◽  
Multivariate Normal Distribution ◽  
Undrained Shear Strength ◽  
Soil Parameters ◽  
Multivariate Normal ◽  
Cone Penetration ◽  
Overconsolidation Ratio ◽  
Data Points ◽  
Undrained Shear

This study examines the possibility of modeling piezocone cone penetration (CPTU) cone tip resistance, excessive pore pressure behind the cone, undrained shear strength, and overconsolidation ratio of lightly overconsolidated clays as a multivariate normal distribution. This is part of a continuing study to develop a multivariate distribution that could be used to simulate common soil parameters at a clay site. This study compiles a large database consisting of 535 data points in which the CPTU parameters, undrained shear strength, and overconsolidation ratio are simultaneously measured in close proximity. A multivariate normal distribution is then used to capture the correlations between soil parameters of interest and to derive useful equations for Bayesian inference. This constructed multivariate normal distribution and equations are further validated by another independent database consisting of 594 data points as well as by empirical equations proposed in literature. The most useful outcome of this study is to provide a systematic and analytical method for updating the distributions of the normalized undrained shear strength and the overconsolidation ratio in the presence of CPTU parameters.

scholarly journals Geotechnical Centrifuge Modelling of Retrogressive Sensitive Clay Landslides

2020 ◽  
Author(s):  
Ray Kennedy ◽  
W. Andy Take ◽  
Gregory A. Siemens
Keyword(s):  
Shear Strength ◽  
Slope Angle ◽  
Physical Modelling ◽  
Failure Surface ◽  
Undrained Shear Strength ◽  
Stability Number ◽  
Surface Stability ◽  
Geotechnical Centrifuge ◽  
Sensitive Clay ◽  
Undrained Shear

Sensitive clay landslides represent a significant geohazard due to their well-known potential for extensive retrogressive failures, on the scale of multiple hectares, which could encompass surrounding communities and infrastructure. Interpretation of retrogression mechanisms is often limited since only forensic investigations are possible. This work presents the results of a physical modelling study to examine retrogressive failures, analysis of each failure episode, and interpretation of the results using published relationships. Five novel centrifuge model tests were conducted under a defined range of undrained shear strength and slope angle conditions. The models are constructed of a sensitive cement-soil mixture that allows for a consistent contractile material with bespoke shear strength. Results indicate the observed retrogression distance correlates with Taylor’s stability number. The addition of a 5-degree slope angle to invoke a static shear stress on the model provoked notably larger retrogression distances. Post-test undrained shear strength measurements quantified softening of the material along the failure surface. Stability analyses on each failure episode captured the observed failure geometry and factor of safety. Results indicate that the geometric parameters of a slope, specifically the slope angle, may be able to explain a component of the scatter for relating the Taylor’s stability number with retrogression distances.

scholarly journals Modeling parameters of structured clays as a multivariate normal distribution

2012 ◽  
Vol 49 (5) ◽  
pp. 522-545 ◽  
Author(s):  
Jianye Ching ◽  
Kok-Kwang Phoon
Keyword(s):  
Shear Strength ◽  
Probability Distribution ◽  
Normal Distribution ◽  
Multivariate Normal Distribution ◽  
Undrained Shear Strength ◽  
Multivariate Distribution ◽  
Soil Parameters ◽  
Multivariate Normal ◽  
Multivariate Probability Distribution ◽  
Undrained Shear

This study explores the possibility of modeling liquidity index, undrained shear strength, remolded undrained shear strength, preconsolidation stress, and vertical effective stress of structured clays (sensitive or quick clays) as a multivariate normal distribution. The literature is replete with correlation equations between two soil parameters. Consistent synthesis of more than two soil parameters through construction of a multivariate probability distribution function is rare, despite obvious practical usefulness of such an approach. This study compiles a large database of structured clays to construct the multivariate probability distribution among the aforementioned five soil parameters. This multivariate distribution is then used to simulate the correlations between soil parameters of interest and to derive useful equations for Bayesian inference. This constructed multivariate distribution and equations are further validated by another independent database of structured clays as well as by empirical equations proposed in the literature.

Performance of clay samples reinforced with vertical granular columns

2007 ◽  
Vol 44 (1) ◽  
pp. 89-95 ◽  
Author(s):  
J Black ◽  
V Sivakumar ◽  
J D McKinley
Keyword(s):  
Shear Strength ◽  
Ground Improvement ◽  
Stress Path ◽  
Undrained Shear Strength ◽  
Replacement Ratio ◽  
Replacement Method ◽  
Single Column ◽  
Undrained Strength ◽  
Area Replacement Ratio ◽  
Undrained Shear

This paper reports an experimental study in which samples of soft kaolin clay (100 mm in diameter and 200 mm in height) were reinforced with vertical columns of sand and tested under triaxial conditions. Samples were reinforced with either a single column of sand of 32 mm diameter or three columns of sand, each of 20 mm diameter. The replacement method was used to form the columns. The columns were installed in the clay to depths of 120 and 200 mm. Tests were also carried out on samples that were not reinforced with sand columns. The samples were compressed under both drained and undrained conditions. It was found that the undrained shear strength of samples containing full-depth columns was greatly improved compared with that of the unreinforced samples. In the fully drained tests, the sample installed with a single column of 32 mm diameter exhibited better performance than the sample with three columns of 20 mm diameter, although the area replacement ratio in the case of the three 20 mm diameter columns was higher than that of the single 32 mm diameter column. However, the undrained strength of the composite material was not particularly affected by the number of columns.Key words: Ground improvement, undrained shear strength, consolidation, stress path, settlement.

Excavation d'argile sensible au site de l'aménagement hydroélectrique LG-2

1985 ◽  
Vol 22 (2) ◽  
pp. 186-194
Author(s):  
J. J. Paré ◽  
J. G. Lavallée
Keyword(s):  
Shear Strength ◽  
Undrained Shear Strength ◽  
Strength Analysis ◽  
Site Conditions ◽  
Embankment Dams ◽  
Clay Deposits ◽  
Undrained Strength ◽  
Sensitive Clay ◽  
Tailrace Tunnel ◽  
Undrained Shear

This paper is a review of the design adopted to establish the slopes for deep clay excavations (3 000 000 m3) made for founding rockfill embankment dams on bedrock and for clearing the tailrace tunnel portals at the LG-2 hydroelectric site. The design and excavation of soft sensitive clay deposits down to 22 m had been undertaken at a period of time when very few precedents were existing (1974). During the excavation works, only a few minor slides occurred, indicating that the design approach, using undrained shear strength analysis, was appropriate for the site conditions. Methods of excavation and hauling of material to disposal areas are also described. Key words: slope, sensitive clay, undrained strength analysis, safety factor, excavation method, behaviour.

scholarly journals Undrained shear strength of glacial till soils and its determining factors

Baltica ◽  
2021 ◽  
pp. 246-252
Author(s):  
Domas Gribulis ◽  
Kastytis Dundulis ◽  
Saulius Gadeikis ◽  
Sonata Gadeikienė
Keyword(s):  
Shear Strength ◽  
Triaxial Compression ◽  
Undrained Shear Strength ◽  
Test Results ◽  
Fine Silt ◽  
Determining Factors ◽  
Undrained Strength ◽  
Soil Components ◽  
Undrained Shear

This article presents results of the test conducted on the undrained shear strength of till clayey soils of Eastern Lithuania, which are characterized by rigid and very stiff consistency and low plasticity. According to the classification of soils presented in LST EN ISO 14688–2:2018 Geotechnical Investigation and Testing – Identification and Classification of Soil − Part 2: Principles for a Classification, the tested soils are classified as sandy low plasticity clays. The undrained shear strength was tested using the triaxial compression (unconsolidated undrained) method. The test results showed that peculiarities of the particle size distribution had a crucial impact on the undrained strength of these soils, i.e. on the correlation of clay and fine silt fractions with the rest of soil components.

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