scholarly journals Numerical Analysis of Rapid Drawdown of an Embankment Dam

2020 ◽  
Vol 10 (2) ◽  
pp. 5496-5500
Author(s):  
A. H. Bhutto ◽  
G. S. Bhurgri ◽  
S. Zardari ◽  
M. A. Zardari ◽  
R. Bhanbhro ◽  
...  
Keyword(s):  
Shear Strength ◽  
Numerical Analysis ◽  
Undrained Shear Strength ◽  
Embankment Dam ◽  
Staged Construction ◽  
Different Depths ◽  
Undrained Strength ◽  
Clay Core ◽  
The Stability ◽  
Undrained Shear

Numerical analysis for the safe rate determination of lowering of an embankment dam was performed in this study with the use of the finite element method. Coupled deformation and consolidation analysis were carried out for staged construction and drawdown of a 59m embankment dam for varying undrained shear strength of the clay core. The lowering of the reservoir was performed at different depths between two extreme scenarios, i.e. rapid lowering rate (1m/day) and slow lowering rate (0.1m/day). The reservoir of the dam was lowered to a depth from 10m to 55m in gradual increments. The results indicated that the safety of the dam was satisfactory when the reservoir was lowered at the quick rate for a depth of 10m, 20m, 30m respectively when the undrained shear strength of the clay core was taken as 20, 25 and 30kN/m2. Regarding the case of slow drawdown rate of the reservoir, it was found that the reservoir could be lowered up to a depth of 55m at a rate of 0.1m/day when the undrained strength of clay core was 25kN/m2. The stability of the dam was also found satisfactory even though the reservoir was lowered at a rate of 0.25m/day for a depth of 55m when the undrained shear strength of clay core was 30kN/m2.

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.

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.

Stability threshold for cyclic loading of saturated clay

1989 ◽  
Vol 26 (1) ◽  
pp. 122-131 ◽  
Author(s):  
Guy Lefebvre ◽  
Denis LeBoeuf ◽  
Benoît Demers
Keyword(s):  
Shear Strength ◽  
Cyclic Loading ◽  
Strain Rate ◽  
Undrained Shear Strength ◽  
Triaxial Tests ◽  
Repeated Loading ◽  
Loading Test ◽  
Stability Threshold ◽  
The Stability ◽  
Undrained Shear

This paper presents the results of an experimental investigation performed to study the stability threshold under cyclic (repeated) loading, and the postcyclic static strength of a sensitive clay from the Hudson Bay region. The strain rate and structure effects were also studied by carrying out monotonic and cyclic triaxial tests at both slow and rapid strain rates or frequencies, and at confining pressures above and below the apparent preconsolidation pressure. The stability threshold for both structured and normally consolidated Grande Baleine clay is about 60–65% of the original undrained shear strength measured at the same strain rate as that used in the repeated loading test. The undrained shear strength and the failure envelope remain essentially unchanged if the repeated preloading is kept below the threshold. The clay structure remains unaltered by this preloading. Key words: clay, stability threshold, cyclic loading, earthquake, postcyclic strength.

On the evaluation of undrained shear strength and preconsolidation pressure from common field tests in clay

2005 ◽  
Vol 42 (4) ◽  
pp. 1221-1231 ◽  
Author(s):  
Rolf Larsson ◽  
Helen Åhnberg
Keyword(s):  
Shear Strength ◽  
Soft Clay ◽  
Field Tests ◽  
Undrained Shear Strength ◽  
Test Field ◽  
Cone Penetration ◽  
In Situ Tests ◽  
Cone Penetration Tests ◽  
The Stability ◽  
Undrained Shear

The undrained shear strength is a key parameter in the estimation of the stability of natural slopes and man-made constructions in soft clay. It is therefore important to develop relevant methods to evaluate the operative strength. Results from an investigation regarding the effect of excavations at slope crests to increase the stability of clay slopes are presented. This study has provided an opportunity to study the effect of overconsolidation on the evaluated parameters from common in situ tests in homogeneous and truly overconsolidated clays. Certain inconsistencies in the commonly used methods of interpretation of field vane tests, cone penetration tests, and dilatometer tests are highlighted, and modified interpretation methods taking the effects of overconsolidation into account are proposed.Key words: clay, overconsolidation, undrained shear strength, cone penetration test, field vane test, dilatometer test.

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.

Probabilistic analysis of tunnel face stability considering spatially variable undrained shear strength with linearly increasing mean trend

2020 ◽  
pp. 1748006X2092715
Author(s):  
Hongzhan Cheng
Keyword(s):  
Shear Strength ◽  
Finite Difference ◽  
Finite Difference Method ◽  
Difference Method ◽  
Undrained Shear Strength ◽  
Tunnel Face ◽  
Face Stability ◽  
Tunnel Face Stability ◽  
The Stability ◽  
Undrained Shear

The inherent spatial variability of soil properties has been considered as one of the main sources of uncertainties in geotechnical problems. The need for probabilistic analysis of the tunnel face stability that takes into account the variability of soil properties has been acknowledged. This article employed a probabilistic-based method, called random finite difference method, for evaluating the stability of tunnel face under the influence of the variability of undrained shear strength in clays. The two-dimensional spatial variation in soil undrained shear strength is modeled by random fields, which are discretized by the Covariance Matrix Decomposition method. The procedure for random finite difference method is presented. An illustrative example is employed to investigate the effect of soil variability. Particular attention has been paid to the situation that undrained shear strength increases with depth. The results demonstrate that ignoring the variability of undrained shear strength will result in overestimates of the tunnel face stability if the support pressure of the tunnel face exceeds the deterministic value, especially for higher coefficient of variation of soil undrained shear strength. Minor differences in the failure mechanism are observed in comparison to the deterministic case, considering only the global failure of the tunnel face is observed. In addition, ignoring the increase of undrained shear strength with depth will lead to conservative designs. The random finite difference method can provide a practical tool for evaluating the stability of a tunnel face in variable soils.

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.

scholarly journals Influence of Grain Sizes on Undrained Strength of Sand Mixtures

2019 ◽  
Vol 8 (9) ◽  
pp. 3154-3159
Keyword(s):  
Grain Size ◽  
Shear Strength ◽  
Land Reclamation ◽  
Fine Sand ◽  
Undrained Shear Strength ◽  
Coarse Sand ◽  
Sand Particle ◽  
Undrained Strength ◽  
Undrained Shear ◽  
Sand Grain Size

Sand is known as the main material in land reclamation works to develop and widen an area. It is important for the Geotechnical Engineer to ensure the sand used can accommodate the burden imposed from the structures to be built on it. Previous researchers have conducted studies on the strength of sand, whether focusing on the sand itself or with the presence of fines. However, the study of sand grain size effects in sand mixtures in affecting sand behavior is extremely limited. The sizes and angularity of the sand particle are believed to contribute to the behavior of sand mixtures soil. Hence, the study to investigate the effect of sand grain size on sand mixtures in term of undrained strength is being carried out. The sand was sieved to coarse sand, medium sand and fine sand then each size was mixed with kaolin at 0 %, 20 % and 40 %. The undrained strength was obtained from triaxial test on undrained condition. As a result, it is found that the maximum deviator stress, qmax increases with the decrease of fines (kaolin) content. On the other hand, at the same fines content, increased of sand size leads to the increased of qmax, which means the increased of undrained shear strength. In addition, the angular shape of sand particle was thought to contribute to the high value of undrained shear strength for the sand mixtures.

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