Effect of confining pressure and degree of saturation on damping ratios of sand

2014 ◽  
pp. 277-282 ◽  
Author(s):  
Z Cheng ◽  
E Leong
Keyword(s):  
Confining Pressure ◽  
Degree Of Saturation

scholarly journals Influence of the Saturation Ratio on Concrete Behavior under Triaxial Compressive Loading

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Xuan-Dung Vu ◽  
Matthieu Briffaut ◽  
Yann Malecot ◽  
Laurent Daudeville ◽  
Bertrand Ciree
Keyword(s):  
Nuclear Power ◽  
Water Saturation ◽  
Confining Pressure ◽  
Degree Of Saturation ◽  
Triaxial Tests ◽  
Saturation Ratio ◽  
Concrete Wall ◽  
Saturation State ◽  
Massive Concrete ◽  
The Impact

When a concrete structure is subjected to an impact, the material is subjected to high triaxial compressive stresses. Furthermore, the water saturation ratio in massive concrete structures may reach nearly 100% at the core, whereas the material dries quickly on the skin. The impact response of a massive concrete wall may thus depend on the state of water saturation in the material. This paper presents some triaxial tests performed at a maximum confining pressure of 600 MPa on concrete representative of a nuclear power plant containment building. Experimental results show the concrete constitutive behavior and its dependence on the water saturation ratio. It is observed that as the degree of saturation increases, a decrease in the volumetric strains as well as in the shear strength is observed. The coupled PRM constitutive model does not accurately reproduce the response of concrete specimens observed during the test. The differences between experimental and numerical results can be explained by both the influence of the saturation state of concrete and the effect of deviatoric stresses, which are not accurately taken into account. The PRM model was modified in order to improve the numerical prediction of concrete behavior under high stresses at various saturation states.

scholarly journals Dilatancy Characteristics and Constitutive Modelling of the Unsaturated Soil Based on Changes in the Mass Water Content

2021 ◽  
Vol 11 (11) ◽  
pp. 4859
Author(s):  
Xiao Xu ◽  
Guoqing Cai ◽  
Zhaoyang Song ◽  
Jian Li ◽  
Chongbang Xu ◽  
...  
Keyword(s):  
Water Content ◽  
Unsaturated Soil ◽  
Soil Mechanics ◽  
Constitutive Models ◽  
Confining Pressure ◽  
Prediction Equation ◽  
Constitutive Modelling ◽  
Degree Of Saturation ◽  
Model Parameters ◽  
High Plasticity

Most soil mechanics theories are limited to strain hardening and shrinkage under high compressive stresses, and there are some shortcomings in the selection of suction or degree of saturation as the water content state varies in the constitutive models of unsaturated soil. Based on the triaxial shear tests of unsaturated compacted soil (a silt of high plasticity) with different water content and confining pressure (low-confining), a shear dilatancy model of unsaturated soil based on the mass water content is proposed in this paper. The influence of the water content on the shear deformation characteristics of the unsaturated soil is analysed. The stress–dilatancy relationship and the prediction equation of the minimum dilatancy rate of the unsaturated soil under different water content and different confining pressure are provided. Selecting the mass water content as the state variable, a constitutive model suitable for the dilatancy of unsaturated soil is established. The method of determining model parameters based on the mass water content is analysed. The applicability of the model is verified by comparisons between the predicted and experimental results.

Seismic measurements in sand specimens with varying degrees of saturation using piezoelectric transducers

2012 ◽  
Vol 49 (6) ◽  
pp. 671-685 ◽  
Author(s):  
Celestino Valle-Molina ◽  
Kenneth H. Stokoe
Keyword(s):  
Excitation Frequency ◽  
Critical Factor ◽  
Confining Pressure ◽  
Small Strain ◽  
Piezoelectric Transducers ◽  
Degree Of Saturation ◽  
Bender Elements ◽  
Optimum Frequency ◽  
S Waves ◽  
Seismic Measurements

Small-strain seismic measurements in sand specimens were undertaken in the laboratory using piezoelectric transducers. The measurements involved determining both constrained compression wave and shear wave velocities, Vp and Vs, respectively. The piezoelectric transducers were discs (PDs) for Vp measurements and bender elements (BEs) for Vs measurements. An instrumented triaxial chamber (ITC) was developed and associated support instrumentation was assembled to perform the seismic measurements. The same PDs and BEs were installed in a combined resonant column and torsional shear (RCTS) device. The soil tested in both devices was washed mortar sand. The sand was tested in dry, unsaturated, and saturated conditions in the ITC, while only dry sand was tested in the RCTS. Development, calibration, and operation of the PDs and BEs are discussed. Example waveforms are presented, which are associated with different stress levels, saturation conditions, and frequencies of excitation for P and S waves. A critical factor in performing successful measurements is the driving of each type of piezoelectric transducer at the optimum frequency, which depends on the effective confining pressure ([Formula: see text]), degree of saturation, and soil type. The excitation frequency used for PDs was found to be important when the sand specimens were at nearly or fully saturated conditions.

Undrained Behavior of Unsaturated Bentonite-Sand Mixture

2012 ◽  
Vol 446-449 ◽  
pp. 1454-1457
Author(s):  
Wen Jing Sun ◽  
De An Sun ◽  
Jin Yi Zhang
Keyword(s):  
Confining Pressure ◽  
Degree Of Saturation ◽  
Dry Density ◽  
Compression Tests ◽  
Shear Tests ◽  
Isotropic Compression ◽  
Sand Mixture ◽  
Mechanical Behaviours ◽  
Undrained Behavior ◽  
Gaomiaozi Bentonite

The strength, deformation and hydro-mechanical behaviours of a compacted unsaturated Gaomiaozi bentonite-sand mixture under undrained condition are studied by conducting a series of isotropic compression tests and triaxial shear tests under constant water content. During undrained isotropic compression testing, void ratio and suction decrease while degree of saturation increases. The stress-strain relations are obtained from undrained triaxial shear tests. The volume contraction and lateral expansion can be observed. The suction decreases with increasing shearing. The net confining pressure and initial dry density affect the initial rigidity, undrained shear strength, volumetric deformation and hydro-mechanical behaviour.

Gas permeability of a compacted bentonite–sand mixture: coupled effects of water content, dry density, and confining pressure

2015 ◽  
Vol 52 (8) ◽  
pp. 1159-1167 ◽  
Author(s):  
Jiang-Feng Liu ◽  
Frédéric Skoczylas ◽  
Jean Talandier
Keyword(s):  
Water Content ◽  
Gas Permeability ◽  
Confining Pressure ◽  
Degree Of Saturation ◽  
Dry Density ◽  
Sand Mixture ◽  
Compacted Bentonite ◽  
High Confining Pressure ◽  
Confining Pressures ◽  
Gas Tightness

The gas-tightness of compacted bentonite–sand mixtures is important to the total sealing efficiency of geological repositories. The initial aim of this work was to determine whether the combination of a high confining pressure (Pc) and incomplete saturation could cause a bentonite–sand mixture to become gas-tight. The results show that the physical characteristics of the materials (degree of saturation, Sr; porosity, [Formula: see text]; and dry density, ρd) are very sensitive to changes in the applied confining pressures and their own swelling deformation (or shrinkage). The combination of these changes affects the sample’s effective gas permeability (Keff). For materials prepared at a relative humidity (RH) of 98%, Keff decreased from 10−16 to 10−20 m2 when Pc increased from 1 to 7 MPa. This means that gas-tightness can be obtained for a compacted bentonite–sand mixture when the materials experience a series of changes (e.g., w, Sr, [Formula: see text], and ρd). In addition, larger irreversible deformation (or hysteresis) was observed during the loading–unloading cycle for the sample with higher water content. This phenomenon may be attributed to larger interactions between the macrostructural and microstructural deformations and the decrease of preconsolidation pressure during hydration.

Permeability of mine tailings measured in triaxial cell

2019 ◽  
Vol 56 (4) ◽  
pp. 587-599
Author(s):  
Hernán Patiño ◽  
Eliana Martínez ◽  
Jesús González ◽  
Antonio Soriano
Keyword(s):  
Mine Tailings ◽  
Confining Pressure ◽  
Degree Of Saturation ◽  
Consolidation Pressure ◽  
Coefficient Of Permeability ◽  
Triaxial Cell ◽  
Empirical Function ◽  
Hydraulic Gradients ◽  
The Mean ◽  
Constant Head

The execution of permeability tests using a triaxial cell makes it possible to eliminate the uncertainties that characterize tests performed using conventional equipment. This paper contains the results of 48 tests carried out on three materials recovered from tailings of Riotinto mines (Spain). The equipment involved a modified triaxial system to facilitate the execution of permeability tests under constant head. The tests were performed on samples consolidated to 50, 100, 200, and 300 kPa for four different hydraulic gradients established by applying a backpressure difference (ΔBp). The magnitude of the backpressure difference was applied as a percentage of the initial effective consolidation pressure, expressed as ΔBp/[Formula: see text]; namely, values of 10%, 15%, 20%, and 25%, which resulted in hydraulic gradients between 5 and 80. The backpressure (Bp) was constant (400 kPa) in all cases, allowing a degree of saturation close to 100% to be achieved. This was verified by calculating Skempton’s B parameter, which was very close to unity in all cases. The results indicate that it is feasible to define an empirical function including the coefficient of permeability (k) and the effective consolidation pressure ([Formula: see text]), the mean effective confining pressure ([Formula: see text]), and the backpressure differential (ΔBp).

Sand–bentonite liners: predicting permeability from laboratory tests

1990 ◽  
Vol 27 (1) ◽  
pp. 47-57 ◽  
Author(s):  
Robert P. Chapuis
Keyword(s):  
Laboratory Tests ◽  
Confining Pressure ◽  
Degree Of Saturation ◽  
Preliminary Evaluation ◽  
Empirical Equations ◽  
Test Results ◽  
Testing Methods ◽  
Natural Sand ◽  
Laboratory Test Results

Soil–bentonite mixes are frequently used as impervious blankets in waste disposal projects. Numerous results of laboratory permeability tests are presented for sands containing up to 33% bentonite. These results seem difficult to analyze because different testing methods have been used in which it is not easy to control certain parameters, such as hydration period, degree of saturation, and swelling under low confining pressure. Hydraulic conductivity, however, can be obtained by using empirical equations that take into account the bentonite content, porosity, and degree of saturation of the sand alone when tested at its optimum modified Proctor value in a permeameter. This preliminary evaluation helps to select the soil to be tested. Then, the laboratory test results can be used to predict the in situ hydraulic performance after due consideration of the variabilities in natural sand and bentonite content. Key words: liner, soil, bentonite, permeability, laboratory, field.

INFLUENCE OF CULTIVATION DEGREE OF SOD-PODZOLIC SOIL ON RESPONSIVENESS OF SOWING PEAS TO NITROGEN NUTRITION LEVEL

2020 ◽  
Keyword(s):  
Podzolic Soil ◽  
Nitrogen Nutrition ◽  
Maximum Yield ◽  
Mineral Nitrogen ◽  
Degree Of Saturation ◽  
Cultivated Soil ◽  
Combined Use ◽  
Dry Soil ◽  
Microbial Preparation ◽  
Harvest Maturity

The article presents the results of a vegetation experiment on studying an effect of increasing doses of nitrogen (factor С - N0; No.o5; No.io; N015; No.2o; N0,25 g/kg of absolutely dry soil) and pre-sowing inoculation of seeds with biological preparation "Risotorphine" (factor В - no inoculation; by inoculation) on the formation of vegetative mass and grain yield ofpeas at cultivating in the conditions of a poorly cultivated (factor A0) and of a medium cultivated (factor A f sod-podzolic soil. Cultivation degree of soil was expressed by such criteria as power of an arable horizon, value of metabolic acidity and content of mobile phosphorus, a degree of saturation of soil with bases. For experience tab there were used Mitscher-lich cups with a capacity of 5 kg of absolutely dry soil (a.d.s.), in 16 repetitions of options. The experiments were conducted in the conditions of vegetation site on the territory of University Scientific Centre "Lipogorie" of FSBEI Perm GATA, guided by a science-based methodology. When harvesting peas for a green mass more intensive development and productivity of plants (23.3 and 58.9, 40.0, 78.8 g/cup, respectively) in the phase of stem branching and budding a beginning offlowering that is recorded for its use on the background of inoculation, usage of mineral nitrogen in a dose of 0.10 g/kg on a poorly cultivated soil and 0.15 g/kg a.d.s. on a medium cultivated soil. Applying of higher doses of nitrogen has a depressing effect on development of assimilating surface of pea plants on a poorly and a medium cultivated soil. When raising pea plants before harvest maturity of grain: in the conditions of a poorly cultivated soil for yield at the level of 7.92 g/cup, the process of carrying on only an inoculation of seed with microbial preparation "Rizotorfin" can be considered; in the medium cultivated soil varieties, plant peas impose higher requirements for the level of mineral nutrition the maximum yield in the experiment (which 9.22 g/cup), noted at a combined use of inoculation and mineral nitrogen in a dose of 0.20 g/kg a.d.s.

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