Temperature Effects on Unconfined Compressive Strength of Clay Soils: Experimental and Constitutive Study

Abstract Unconfined compressive strength (Su) is one of the soil engineering parameters used in geotechnical designs. Due to the temperature changes caused by some human activities, it is important to study the changes in Su at different temperatures. For this purpose, kaolin, illite and montmorillonite clays with a liquid limit (LL) of 47, 80 and 119 respectively, were tested in a temperature-controlled cell in temperature range of 20 to 60 ℃. The results showed that the pore water pressure is a function of temperature and by heating, pore water pressure in the samples increased. In all three types of clay, the Su decreased linearly with increasing temperature. The reduction of Su in kaolin is more than illite and in illite is more than montmorillonite. The reason for this reduction, might be due the difference in the mineralogy of the clays. The results of unconfined compressive tests at different temperatures were simulated using hypoplastic model.

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Gas pressure in unsaturated offshore soils

Canadian Geotechnical Journal ◽

10.1139/t90-008 ◽

1990 ◽

Vol 27 (1) ◽

pp. 79-89 ◽

Cited By ~ 23

Author(s):

S. J. Wheeler ◽

W. K. Sham ◽

S. D. Thomas

Keyword(s):

Surface Tension ◽

Pore Water ◽

Pore Water Pressure ◽

Water Pressure ◽

Gas Pressure ◽

Cavity Expansion ◽

Total Stress ◽

Pressure Surface ◽

Reconstituted Soil ◽

The Difference

Direct measurement of gas pressure within unsaturated offshore soils is very difficult because the gas occurs in the form of large, discrete bubbles. However, consideration of the soil structure and analysis of a continuum model for the soil suggest two independent sets of limits for the gas bubble pressure. Surface tension effects limit the difference between gas pressure and pore-water pressure, while cavity expansion and contraction considerations limit the difference between gas pressure and mean total stress. If the gas pressure lies within these limits, it should remain almost unaffected by changes to the total stress or pore-water pressure. These suggestions are supported by results from an oedometer test on a reconstituted soil sample containing large bubbles of methane gas. Key words: bubbles, cavity expansion, gas, oedometer tests, offshore geotechnics, pore pressure, surface tension, unsaturated.

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Mechanical properties and acoustic emission characteristics of granite under thermo-hydro-mechanical coupling

Thermal Science ◽

10.2298/tsci2106585w ◽

2021 ◽

Vol 25 (6 Part B) ◽

pp. 4585-4596

Author(s):

Xin-Zhong Wang ◽

Dong Wang ◽

Zhe-Wei Wang ◽

Xiao-Juan Yin ◽

Xue-Jun Zhou ◽

...

Keyword(s):

Mechanical Properties ◽

Acoustic Emission ◽

Elastic Modulus ◽

Pore Water ◽

Pore Water Pressure ◽

Water Pressure ◽

Thermal Cracking ◽

Confining Pressure ◽

Mechanical Coupling ◽

Increasing Temperature

Exploring the mechanical properties and thermal cracking characteristics of rock under thermo-hydro-mechanical coupling in detail is of great importance for the safe excavation and stability of deep rock engineering. The mechanical properties and thermal cracking characteristics of granite under burial depths of 1000 m (confining pressure of 25 MPa) and 1600 m (confining pressure of 40 MPa) at a temperature of 110?C and a pore water pressure of 10 MPa were studied. The results show that the elastic modulus decreases with increasing temperature under a confining pressure of 25 MPa, whereas under a confining pressure of 40 MPa, the elastic modulus increases with increasing temperature. As the pore water pressure increases, the elastic modulus decreases slightly. Poisson?s ratio increas?es with increasing temperature below 40?C but decreases from 50-110?C. Pois?son?s ratio increases as pore water pressure increases. During the heating process, acoustic emission activity is first detected at 30-40?C and is relatively stable from 40-90?C. The acoustic emission activity increases sharply at 90-110?C, and the thermal cracking threshold of granite under thermo-hydro-mechanical coupling is approximately 95?C.

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Constitutive modelling of gassy clay

E3S Web of Conferences ◽

10.1051/e3sconf/20199215005 ◽

2019 ◽

Vol 92 ◽

pp. 15005

Author(s):

Zhiwei Gao ◽

Yi Hong

Keyword(s):

Pore Water ◽

Pore Water Pressure ◽

Water Pressure ◽

Gas Bubbles ◽

Constitutive Modelling ◽

Soil Response ◽

Saturated Clay ◽

Small Pore ◽

Clay Matrix ◽

The Difference

Fine grained sediments with undissolved gas bubbles are widely distributed in the seabed around the world. The gas bubbles are much larger than the clay particles and fit in the saturated clay matrix rather than the pore water. Generally, these bubbles tend to degrade the soil stiffness and strength. But when the difference between the gas and pore water pressure is sufficiently small, pore water in the saturated clay matrix can drain into the cavities, making the void ratio of the saturated matrix smaller, which makes the undrained shear strength of the gassy clay sample higher than that of a saturated one. Such soil response cannot be described based on the assumption that gassy clay is a soil with compressible pore fluid. A new constitutive model for describing the stress-strain relation for gassy clay is proposed. An important feature of the model is that the gassy clay is considered as a composite material with compressible cavities which could be flooded by pore water. Effect of gas cavities on plastic hardening on the saturated matrix is accounted for. The model has been used to predict the response of three gassy clays and good agreement between the test data and model simulations is observed. Potential improvement of the model is discussed.

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Liquefaction, landslide and slope stability analyses of soils: a case study of soils from part of Kwara, Kogi and Anambra states of Nigeria

10.5194/nhess-2016-297 ◽

2016 ◽

Cited By ~ 1

Author(s):

Olusegun O. Ige ◽

Tolulope A. Oyeleke ◽

Christopher Baiyegunhi ◽

Temitope L. Oloniniyi ◽

Luzuko Sigabi

Keyword(s):

Shear Strength ◽

Pore Water ◽

Slope Failure ◽

Pore Water Pressure ◽

Water Pressure ◽

Base Material ◽

Liquid Limit ◽

Soil Samples ◽

Landslide Risk ◽

Angle Of Internal Friction

Abstract. Landslide is one of the most ravaging natural disaster in the world and recent occurrences in Nigeria require urgent need for landslide risk assessment. A total of nine samples representing three major landslide prone areas in Nigeria were studied, with a view of determining their liquefaction and sliding potential. Geotechnical analysis was used to investigate the liquefaction potential, while the slope conditions were deduced using SLOPE/W. The results of geotechnical analysis revealed that the soils contain 6–34 % clay and 72–90 % sand. Based on the unified soil classification system, the soil samples were classified as well graded with group symbols of SW, SM and CL. The plot of plasticity index against liquid limit shows that the soil samples from Anambra and Kogi are potentially liquefiable. The liquefaction screening criteria also revealed that Anambra and Kogi are potentially susceptible to liquefaction, whereas samples from Kwara are not susceptible to liquefaction. Samples from Kogi and Anambra have lower values of MDD and OMC, ranging between 1.64–1.80 g/cm3 and 8.0–12.3 % respectively. These values showed that the samples are granular material with soil having anticipated embankments performance, subgrade and base material as poor-fair, fair-good and good-poor, respectively. The direct shear strength test on the soil samples indicated that the cohesion and angle of internal friction varies between 40 80 kPa and 24–35°. The Coefficient of permeability vary between 8.71 × 10−5 and 1.18 × 10−3. The factor of safety (FOS) values for soils from Anambra, Kogi and Kwara are 1.452, 1.946 and 2.488, respectively. These values indicate stability but care must be taken as the condition at the site shows that the slope is in its state of impending failure. The FOS for dry slope was higher when compared to the FOS values from wet slope. This was due to the effect of pore water pressure on the soil as it reduced the shear strength of the soil. A reduced value of FOS was observed in the model under loading conditions, which indicate that loading is also a contributing factor to the slope failure. It is recommended that proper and efficient drainage system should be employed in these areas to reduce the influence of pore water pressure in the soil.

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Influential Mechanism of Pore Water Pressure on the Compressive Strength of Concrete

DEStech Transactions on Engineering and Technology Research ◽

10.12783/dtetr/icaenm2017/7828 ◽

2017 ◽

Author(s):

Ying Cui ◽

Weifeng Bai ◽

Yongjie Zheng ◽

Haotian Han ◽

Linai Liu

Keyword(s):

Compressive Strength ◽

Pore Water ◽

Pore Water Pressure ◽

Water Pressure ◽

Compressive Strength Of Concrete

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TIME TO THE END OF PRIMARY CONSOLIDATION (EOP) OF SOFT CLAYEY SOILS: CONCERNING THE EFFECT OF ATTERBERG’S LIMIT AND CYCLIC LOADING HISTORY

HUE UNIVERSITY JOURNAL OF SCIENCE TECHNIQUES AND TECHNOLOGY ◽

10.26459/hueuni-jtt.v128i2b.5424 ◽

2019 ◽

Vol 128 (2B) ◽

pp. 29-41

Author(s):

Trần Thanh Nhàn

Keyword(s):

Cyclic Loading ◽

Pore Water ◽

Pore Water Pressure ◽

Water Pressure ◽

Clayey Soils ◽

Loading History ◽

Cyclic Shear ◽

Wide Range ◽

Primary Consolidation ◽

Time Required

In order to observe the end of primary consolidation (EOP) of cohesive soils with and without subjecting to cyclic loading, reconstituted specimens of clayey soils at various Atterberg’s limits were used for oedometer test at different loading increments and undrained cyclic shear test followed by drainage with various cyclic shear directions and a wide range of shear strain amplitudes. The pore water pressure and settlement of the soils were measured with time and the time to EOP was then determined by different methods. It is shown from observed results that the time to EOP determined by 3-t method agrees well with the time required for full dissipation of the pore water pressure and being considerably larger than those determined by Log Time method. These observations were then further evaluated in connection with effects of the Atterberg’s limit and the cyclic loading history.

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Conjectures, Hypotheses, and Theories of Drumlin Formation (In memory of Stanislaw Baranowski)

Journal of Glaciology ◽

10.3189/s0022143000011552 ◽

1981 ◽

Vol 27 (97) ◽

pp. 503-505 ◽

Cited By ~ 1

Author(s):

Ian J. Smalley

Keyword(s):

Shear Strength ◽

Pore Water ◽

Stress Level ◽

Critical Stress ◽

Pore Water Pressure ◽

Water Pressure ◽

Glacial Till ◽

Forming Process ◽

Stress Levels

AbstractRecent investigations have shown that various factors may affect the shear strength of glacial till and that these factors may be involved in the drumlin-forming process. The presence of frozen till in the deforming zone, variation in pore-water pressure in the till, and the occurrence of random patches of dense stony-till texture have been considered. The occurrence of dense stony till may relate to the dilatancy hypothesis and can be considered a likely drumlin-forming factor within the region of critical stress levels. The up-glacier stress level now appears to be the more important, and to provide a sharper division between drumlin-forming and non-drumlin-forming conditions.

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