Gradation and shear characteristics of four cohesionless soils

1970 ◽  
Vol 7 (1) ◽  
pp. 62-68 ◽  
Author(s):  
N. A. Skermer ◽  
S. F. Hillis
Keyword(s):  
Ultimate Strength ◽  
Confining Pressure ◽  
Maximum Density ◽  
Triaxial Tests ◽  
Particle Crushing ◽  
Cohesionless Soils ◽  
Confining Pressures ◽  
Shear Characteristics ◽  
High Ultimate Strength ◽  
Coarse Gravel

Comparison of typical results from drained triaxial tests carried out at confining pressures of 50 and 350 p.s.i. (3.52 and 24.61 kg/cm2) on four cohesionless soils are presented.The effect of gradation at constant relative density is explored, and it is concluded that there is an optimum gradation in terms of both high ultimate strength and high mobilized strength. Uniform coarse gravel is shown to have poor mobilized strength, but at confining pressures high enough to cause particle crushing the improvement in gradation and packing leads to a high ultimate strength, although large axial strains are necessarily induced. The optimum gradation is shown to be close to Fuller's curve for maximum density. The effect of increasing the confining pressure from 50 to 350 p.s.i. (3.52 to 24.61 kg/cm2) leads to a decrease in [Formula: see text] peak of 6 to 10°, but modifications for dilatancy lead to [Formula: see text] parameters that are sensibly constant for any one material.

Comparative study of coral sand and silica sand in creep under general stress states

2017 ◽  
Vol 54 (11) ◽  
pp. 1601-1611 ◽  
Author(s):  
Yaru Lv ◽  
Feng Li ◽  
Yawen Liu ◽  
Pengxian Fan ◽  
Mingyang Wang
Keyword(s):  
Grain Size ◽  
Creep Behavior ◽  
Confining Pressure ◽  
Silica Sand ◽  
Triaxial Tests ◽  
Particle Crushing ◽  
Particle Rotation ◽  
General Stress ◽  
Coral Sand ◽  
Stress States

Coral sand has individual characteristics that differ from silica sand, such as creep behavior that is always attributed to particle crushing under high stress states. To understand the creep behavior of coral sand under general stress levels, three series of comparative triaxial tests relevant to the deviator stress, confining pressure, and relative density were performed on coral sand and silica sand creeping for more than 5 days. The volumetric, axial, and shear creeps of coral sand are considerably larger than those of silica sand, particularly under a relatively high confining pressure. The volumetric creep strain of coral sand was found to be contractive, but that of silica sand appeared dilative according to the creep time. This difference is not mainly governed by particle crushing in coral sand because the grain-size distribution prior to and after creep is similar. The grain skeletons were observed using a scanning electron microscope, finding that, independent of the grain size and shape, the coral grains include large amounts of cavities. The creep of coral sand under general stress conditions is mainly caused by particle interlocking, i.e., the angular regions of some particles interlock into the cavities of other particles due to particle rotation. This structuration is induced by breakage of asperities and voids during creep such as the local instability near cavities.

Experimental Study on Mechanical Property of Thermo-Mechanical and Hydro-Mechanical Coupling Condition for a Sandstone

2006 ◽  
Vol 326-328 ◽  
pp. 1797-1800 ◽  
Author(s):  
Qing Chun Zhou ◽  
Hai Bo Li ◽  
Chun He Yang ◽  
Chao Wen Luo
Keyword(s):  
Pore Pressure ◽  
Deformation Modulus ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Underground Engineering ◽  
Coupling Condition ◽  
West China ◽  
Mechanical Coupling ◽  
North Water ◽  
Confining Pressures

The mechanical properties of rock under high temperature, high geostress and high pore pressure are the basic and important information to assess the safety of underground engineering in west China. Based on the environmental conditions of the west route of south-to-north water transfer project in west China, a series of triaxial tests at confining pressures (0 to 60MPa) and temperatures (25°C to 70°C) as well as pore pressure (0 to 10MPa) have been conducted for a sandstone. It is reported that under the temperatures varying from 25°C to 70°C, the strength of the rock increases with the increment of confining pressure, while the deformation modulus of the rock doesn’t change distinctly with the increment of confining pressures. It is also indicated under the temperatures condition in the experiments, when the confining pressure is lower than 40MPa, the strength of the rock increases with the increment of temperature, whereas when the confining pressure is higher than 40MPa, the strength of rock tend to decrease with increment of temperature. It is further shown that the strength decreases with increasing pore pressure, and the decreasing rates tend to decrease with the increment of confining pressures.

scholarly journals Physical and Mechanical Properties of a Bulk Lightweight Concrete with Expanded Polystyrene (EPS) Beads and Soft Marine Clay

Materials ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1662 ◽  
Author(s):  
Jianguo Wang ◽  
Bowen Hu ◽  
Jia Hwei Soon
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Cement Content ◽  
Mass Density ◽  
Physical And Mechanical Properties ◽  
Confining Pressure ◽  
Expanded Polystyrene ◽  
Triaxial Tests ◽  
Filling Material ◽  
Confining Pressures

The variation of physical and mechanical properties of the lightweight bulk filling material with cement and expanded polystyrene (EPS) beads contents under different confining pressures is important to construction and geotechnical applications. In this study, a lightweight bulk filling material was firstly fabricated with Singapore marine clay, ordinary Portland cement and EPS. Then, the influences of EPS beads content, cement content, curing time and confining pressure on the mass density, stress–strain behavior and compressive strength of this lightweight bulk filling material were investigated by unconsolidated and undrained (UU) triaxial tests. In these tests, the mass ratios of EPS beads to dry clay (E/S) were 0%, 0.5%, 1%, 2%, and 4% and the mass ratios of cement to dry clay (C/S) were 10% and 15%. Thirdly, a series of UU triaxial tests were performed at a confining pressure of 0 kPa, 50 kPa, 100 kPa, and 150 kPa after three curing days, seven curing days, and 28 curing days. The results show that the mass density of this lightweight bulk filling material was mainly controlled by the E/S ratio. Its mass density decreased by 55.6% for the C/S ratio 10% and 54.9% for the C/S ratio 15% when the E/S ratio increased from 0% to 4% after three curing days. Shear failure more easily occurred in the specimens with higher cement content and lower confining pressure. The relationships between compressive strength and mass density or failure strain could be quantified by the power function. Increasing cement content and reducing EPS beads content will increase mass density and compressive strength of this lightweight bulk filling material. The compressive strength with curing time can be expressed by a logarithmic function with fitting correlation coefficient ranging from 0.83 to 0.97 for five confining pressures. These empirical formulae will be useful for the estimation of physical and mechanical properties of lightweight concretes in engineering application.

scholarly journals Experimental study on the thermal damage characteristics of cement stone

2020 ◽  
pp. 317-317
Author(s):  
Feng Xu ◽  
Bowen Qian ◽  
Ling Tan ◽  
Jianqiang Xu ◽  
Shengchuan Tang ◽  
...  
Keyword(s):  
Strain Curve ◽  
Horizontal Wells ◽  
Friction Angle ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Cement Stone ◽  
Different Temperatures ◽  
Confining Pressures ◽  
Southwest Region ◽  
Sealing Failure

Aiming at the problem of cement ring sealing failure during deep high-temperature shale gas exploitation, comprehensively considering the influence of the characteristics of multi-cluster fracturing of multiple horizontal wells and formation temperature, the cementing cement the southwest region is taken as the research object. After exposure to different temperatures (95?C and 135?C) and for different times (5, 10 and 20 times), axial and triaxial tests with different confining pressures (0, 5 MPa, 15 MPa and 30 MPa) were carried out. The research shows that: (1) the stress-strain curve of cement stone after heat treatment can be divided into four stages: compaction, elastic, yield and post-peak stage. As the confining pressure increases, the compaction phase disappears, the yield phase increases, and we see the transition from brittle to ideal plasticity after the peak; (2) as the temperature and number of thermal cycles increase, the cohesive force decreases significantly, and the internal friction angle shows a slight increase. The elastic modulus and the peak strength decreased.

scholarly journals Study on some fundamental factors affecting the static liquefaction of sand

2020 ◽  
Vol 61 (HTCS6) ◽  
pp. 40-47
Author(s):  
Kien Trung Nguyen ◽  
Thang Kim Nguyen ◽  
Ha Quang Ta ◽  
Huy Quang Dang ◽  
Keyword(s):  
Significant Influence ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Liquefaction Resistance ◽  
Factors Affecting ◽  
Static Liquefaction ◽  
The World ◽  
Long Time ◽  
Confining Pressures ◽  
Undrained Conditions

Static liquefaction of soil is a hazard that has caused a lot of damage to humans. Therefore, this phenomenon has been studied for a long time over the world, nevertheless, research on this issue in Vietnam is still limited. This paper presents the results of several triaxial tests under undrained conditions to evaluate the influence of some fundamental factors on the static liquefaction of Fontainebleau sand. The results show that the relative density and the confining pressure have a significant influence on the static liquefaction of the sand. When the density of the sand increases, the liquefaction resistance of the sand increases, until a certain limit, the sand changes from liquefaction behavior to dilatancybehavior with a decrease in pore pressure and an increase in mean effective stress. When the test is carried out at different confining pressures, the greater the confining pressure, the higher the liquefaction resistance.

scholarly journals Investigation on the relationship between CT numbers and marble failure under different confining pressures

2021 ◽  
Vol 60 (1) ◽  
pp. 846-852
Author(s):  
Yang Yan-Shuang ◽  
Li Kai-Yue ◽  
Zhou Hui ◽  
Tian Hao-Yuan ◽  
Cheng Wei ◽  
...  
Keyword(s):  
Damage Mechanics ◽  
Triaxial Compression ◽  
Ct Scanning ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Compression Tests ◽  
Ct Number ◽  
Confining Pressures ◽  
Loading Tests ◽  
Rock Specimens

Abstract Computed tomography (CT) scanning technology is helpful in investigating rock materials as it can demonstrate the micro structure of rock clearly. Conventional triaxial compression tests and the corresponding graded triaxial loading tests were carried out to investigate the complex failure mechanism of the marble at the Jinping Hydropower Station. After that CT-scanning tests were done on the loaded marble specimens. The test results show that (1) the CT numbers of the specimens have a certain statistical regularity, that is, the CT numbers of the specimens under different confining pressures satisfy the Weibull distribution, as the confining pressure increases, the mean values rise while variances decrease; (2) in the two groups of tests, the average CT numbers corresponding to the conventional triaxial tests are higher than those corresponding to the graded loading tests, but the CT number variances are lower than those of the graded loading tests; and (3) according to meso-damage mechanics, the damage variables of the rock specimens were established based on the definition of CT numbers. The calculation results show that the damage variables decrease with the increase in confining pressure, the damage variables of the rock specimens in the graded loading tests are higher than those in the conventional triaxial test, and the differences between the two loading tests have grown with the increase in confining pressure.

scholarly journals Effect of Geotextile Reinforcement on Shear Strength of Sandy Soil: Laboratory Study

2016 ◽  
Vol 38 (4) ◽  
pp. 3-13 ◽  
Author(s):  
Sidali Denine ◽  
Noureddine Della ◽  
Muhammed Rawaz Dlawar ◽  
Feia Sadok ◽  
Jean Canou ◽  
...  
Keyword(s):  
Shear Strength ◽  
Mechanical Behaviour ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Loose Sand ◽  
Test Results ◽  
Compression Tests ◽  
Confining Stress ◽  
Natural Sand ◽  
Confining Pressures

Abstract This paper presents results of a series of undrained monotonic compression tests on loose sand reinforced with geotextile mainly to study the effect of confining stress on the mechanical behaviour of geotextile reinforced sand. The triaxial tests were performed on reconstituted specimens of dry natural sand prepared at loose relative density (Dr = 30%) with and without geotextile layers and consolidated to three levels of confining pressures 50, 100 and 200 kPa, where different numbers and different arrangements of reinforcement layers were placed at different heights of the specimens (0, 1 and 2 layers). The behaviour of test specimens was presented and discussed. Test results showed that geotextile inclusion improves the mechanical behaviour of sand, a significant increase in the shear strength and cohesion value is obtained by adding up layers of reinforcement. Also, the results indicate that the strength ratio is more pronounced for samples which were subjected to low value of confining pressure. The obtained results reveal that high value of confining pressure can restrict the sand shear dilatancy and the more effect of reinforcement efficiently.

scholarly journals A parametric study on cyclic strength of coastal sand of Digha in West Bengal, India

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Pinak Ray ◽  
Ramendu Bikas Sahu
Keyword(s):  
West Bengal ◽  
Confining Pressure ◽  
Cyclic Stress ◽  
Cyclic Strength ◽  
Triaxial Tests ◽  
Cyclic Stress Ratio ◽  
Confining Pressures ◽  
Coastal Sand ◽  
Number Of Cycles

AbstractStress controlled cyclic triaxial tests have been carried out on coastal sand of Digha, West Bengal, India at different frequencies, confining pressures, relative densities and number of loading cycles for determination of influence of these parameters on cyclic strength (expressed in terms of cyclic stress ratio) and initial liquefaction of Digha sand. The test results provide evidence that increasing density of sand increases liquefaction potential, though it has been found that increase in effective confining pressure reduces cyclic strength of sand. Cyclic strength of sand decreases with increase of number of loading cycles at a specific density and a particular confining pressure. It has been observed that frequency of loading cycles does have any significant influence on the number of cycles for initial liquefaction of Digha sand. An empirical correlation has been developed on cyclic strength of sand based on these parameters and it has been found that this correlation fits quite well with the observed experimental results.

scholarly journals A Constitutive Model of Sandy Gravel Soil under Large-Sized Loading/Unloading Triaxial Tests

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Pengfei Zhang ◽  
Han Liu ◽  
Zhentu Feng ◽  
Chaofeng Jia ◽  
Rui Zhou
Keyword(s):  
Constitutive Model ◽  
Large Scale ◽  
Confining Pressure ◽  
Peak Strength ◽  
Triaxial Tests ◽  
Model Parameters ◽  
Sandy Gravel ◽  
Cumulative Volume ◽  
Gravel Soil ◽  
Confining Pressures

Based on large-scale triaxial tests of sandy gravel materials, the strength and deformation characteristics under loading/unloading conditions are analyzed. At the same time, the applicability of the hyperbolic constitutive model to sandy gravel is studied using experimental data. The results indicate that sandy gravel under low confining pressures (0.2 and 0.4 MPa) shows a weak softening trend; the higher the confining pressure, the more obvious the hardening tendency (0.6 and 0.8 MPa) and the greater the peak strength. During unloading tests, strain softening occurs, and the peak strength increases with increasing confining pressure. During loading tests, dilatancy appears when the confining pressure is low (0.2 MPa). With increasing confining pressure (0.4, 0.6, and 0.8 MPa), the dilatancy trend gradually weakens, and the cumulative volume tric strain increases, which reflects the relevance of the stress paths. Through research, it is found that the hyperbolic constitutive model has good applicability to sandy gravel soils, and the corresponding model parameters are obtained.

scholarly journals Triaxial tests on snow at low strain rate. Part II. Constitutive behaviour

2003 ◽  
Vol 49 (164) ◽  
pp. 91-101 ◽  
Author(s):  
Carlo Scapozza ◽  
Perry Bartelt
Keyword(s):  
Strain Rate ◽  
Yield Stress ◽  
Power Law ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Constitutive Behaviour ◽  
Fine Grained ◽  
Polycrystalline Ice ◽  
Confining Pressures

AbstractFine-grained, dry snow with a density range of 190–435 kg m−3 was tested in triaxial compression at −12°C with confining pressures varying between 0 and 40 kPa. The tests were strain-rate controlled, with strain rates ranging between 7.4 × 10−7 s−1 and 6.6 × 10−5 s−1. The analysis of the test results revealed that the relationship between yield stress and viscous strain rate is best given by a power law, similar to polycrystalline ice. However, the power-law exponent n is a function of density and varies between 1.8 (low-density snow, ρ < 200 kg m−3) and 3.6 (high-density snow, ρ > 320 kg m−3). The tests also showed that lower-density snow displays a significant non-linear stress–strain response before yielding. Two further aspects of the constitutive behaviour of snow were identified: (1) the strainrate independence of the post-yield work-hardening behaviour in compression and (2) the independence of the axial yield stress in relation to the confining pressure. The experimental observations are discussed with respect to the mechanical properties of polycrystalline ice, which is the constituent material of the load-bearing ice skeleton.

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