Effect of unloading duration on unconfined compressive strength

1999 ◽  
Vol 36 (1) ◽  
pp. 166-172 ◽  
Author(s):  
M A Fam ◽  
M B Dusseault
Keyword(s):  
Compressive Strength ◽  
Pore Pressure ◽  
Unconfined Compressive Strength ◽  
Excess Pore Pressure ◽  
Triaxial Tests ◽  
Compression Tests ◽  
Unconfined Compression ◽  
Coefficient Of Consolidation ◽  
Unconfined Compression Test ◽  
Excess Pore

This note examines the effect of unloading duration on unconfined compression test results. Artificial clayey specimens were prepared using the slurry consolidation technique. Extracted specimens were loaded vertically under K0 conditions, and the load was kept constant until the end of primary consolidation. Specimens were unloaded and unconfined compression tests were carried out at different times after unloading. It is observed that the longer the unloading duration, the lower the measured unconfined strength. This behavior is attributed to the presence of negative excess pore pressure that dissipates with time, reducing the strength. Using the measured coefficient of consolidation, the degree of excess pore pressure dissipation and therefore the average mean effective stress near the failure zone can be calculated at the time of failure. Mohr circles are drawn tangential to the total shear envelope, using the calculated mean effective stresses. Reasonable agreement between predicted and measured unconfined compressive strengths has been observed, suggesting that consolidation theory can be adopted to assess the effect of unloading duration on unconfined compressive strength. Finally, engineering applications using a similar concept are briefly discussed.Key words: clays, unloading, consolidation, unconfined compression tests, triaxial tests.

scholarly journals The Effect of Polymer-Cement Stabilization on the Unconfined Compressive Strength of Liquefiable Soils

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Ali Ateş
Keyword(s):  
Compressive Strength ◽  
Compression Strength ◽  
Unconfined Compressive Strength ◽  
Soil Stabilization ◽  
Sandy Soils ◽  
Pulse Velocity ◽  
Unit Weight ◽  
Unconfined Compression Strength ◽  
Compression Tests ◽  
Unconfined Compression

Soil stabilization has been widely used as an alternative to substitute the lack of suitable material on site. The use of nontraditional chemical stabilizers in soil improvement is growing daily. In this study a laboratory experiment was conducted to evaluate the effects of waterborne polymer on unconfined compression strength and to study the effect of cement grout on pre-venting of liquefiable sandy soils. The laboratory tests were performed including grain size of sandy soil, unit weight, ultrasonic pulse velocity, and unconfined compressive strength test. The sand and various amounts of polymer (1%, 2%, 3%, and 4%) and cement (10%, 20%, 30%, and 40%) were mixed with all of them into dough using mechanical kneader in laboratory conditions. Grouting experiment is performed with a cylindrical mould of  mm. The samples were subjected to unconfined compression tests to determine their strength after 7 and 14 days of curing. The results of the tests indicated that the waterborne polymer significantly improved the unconfined compression strength of sandy soils which have susceptibility of liquefaction.

Influence of Curing Pressure on Unconfined Compressive Strength of Cemented Clay

2018 ◽  
Vol 928 ◽  
pp. 263-268 ◽  
Author(s):  
Anuchit Uchaipichat
Keyword(s):  
Compressive Strength ◽  
Unconfined Compressive Strength ◽  
Cement Content ◽  
Soft Clay ◽  
Peak Stress ◽  
Confining Pressure ◽  
Compression Tests ◽  
Unconfined Compression ◽  
Soil Cement ◽  
Curing Pressure

The soil-cement columns are generally installed and cured in the soft clay layers under confining pressure. The strength of the soil-cement columns may be influenced by confining pressure during curing period. In this study, the main objective was to study the influence of curing pressure on unconfined compressive strength of cemented clay. A series of unconfined compression tests was performed on a cement admixed clay sample cured under pressure values of 0 kPa (atmospheric pressure), 25kPa, 50kPa and 100 kPa using a typical unconfined compression equipment. The test samples with values of cement content of 0.5, 1.0 and 2.0 percent were cured for 28 days.The stress-strain curves obtained from all tests show a peak value of stress. The unconfined compressive strength or peak stress obviously increased with increasing cement content for all curing pressure conditions. It can be observed that the strength of samples gradually increased with curing pressure for cement content of 0.5 percent. For cement contents of 1.0 and 2.0 percent, the strengths of samples cured under pressures of 25 kPa dramatically increased from the strength of samples cured without pressure (0 kPa), however, the strengths of samples for curing pressures of 25, 50 and 100 kPa were not clearly different.

Energy dissipation and dynamic behaviour of clay under cyclic loading

1992 ◽  
Vol 29 (1) ◽  
pp. 103-111 ◽  
Author(s):  
Y. L. Cao ◽  
K. T. Law
Keyword(s):  
Shear Modulus ◽  
Pore Pressure ◽  
Dynamic Behaviour ◽  
Dynamic Strength ◽  
Excess Pore Pressure ◽  
Triaxial Tests ◽  
Dynamic Shear Modulus ◽  
Dynamic Shear ◽  
Energy Concept ◽  
Excess Pore

A laboratory study has been conducted to investigate the dynamic behaviour of Champlain Sea clay from two locations in the Ottawa River valley region. The test program includes cyclic triaxial tests and resonant-column tests. The soil samples were consolidated at a range of pressures before the dynamic shear in order to cover the dynamic behaviour under both the overconsolidated and the normally consolidated states. An energy concept is introduced to interpret the test results. Mathematical relationships have been established for describing the various aspects of dynamic behaviour. These aspects include excess pore pressure, dynamic strength, dynamic shear modulus, and plastic strain. The study shows that the energy concept provides a promising way to analyze dynamic soil behaviour. Key words : energy, dynamic behaviour, clay, cyclic test, earthquake, excess pore pressure, shear modulus, strength.

Effect of the Time on the Undrained Shear Strength and Permeability of Clay-Wooden Sawdust Mixtures Used to Improve Landfills Liner

2020 ◽  
Vol 857 ◽  
pp. 311-318
Author(s):  
Omar Hamdi Jasim ◽  
Doğan Çetin
Keyword(s):  
Shear Strength ◽  
Undrained Shear Strength ◽  
Triaxial Tests ◽  
Compression Tests ◽  
Unconfined Compression ◽  
Unconfined Compression Test ◽  
Remarkable Effect ◽  
The Impact ◽  
Undrained Shear

This study aims to assess the impact of time on sawdust usage to enhance the behavior of the clay used in landfills. The soil used in this paper was brought from Büyükçekmece region / Istanbul. Four proportions (1, 2, 3 and 5) of the sawdust were added as a percentage of the dry weight of the soil. Soil-sawdust mixtures were compacted with the optimum water content corresponding to each percentage and samples were extracted. The extracted samples were divided into two groups, the immediate tests were performed on the first group while the second group was kept in special containers for long-term tests after 90 days. A series of undrained unconsolidated triaxial tests (UU) and unconfined compression tests (UCS) were performed on the specimens and compared with the row soil, in the immediate tests, the results from the UU triaxial test showed that the undrained shear strength was increased as the sawdust content increased and then decreased, it was conducted that the optimum sawdust content was 3%, it was increased the undrained shear strength by (39.5%) and (41.44%) for UU triaxial and Unconfined compression tests respectively. After 90 days of the curing period, it found that 2% is the optimum sawdust content, it was increased the undrained shear strength by (202.51%) and (176.64%) for UU triaxial and unconfined compression test respectively. In the immediate and long-term tests, the coefficient of permeability increased by (66.66) and (94.44%) as the sawdust increased from 0 to 5 % respectively. Sawdust increases the hydraulic conductivity of the clay. It can be concluded that the sawdust usage has a remarkable effect on the shear strength of the clay for both immediate and long-term tests.

One-dimensional consolidation with uncertain properties

1992 ◽  
Vol 29 (1) ◽  
pp. 161-165 ◽  
Author(s):  
Han Ping Hong
Keyword(s):  
Pore Pressure ◽  
Probability Distributions ◽  
Random Variable ◽  
Excess Pore Pressure ◽  
Coefficient Of Consolidation ◽  
One Dimensional ◽  
Degree Of Consolidation ◽  
Fifth Order ◽  
Matching Probability ◽  
Excess Pore

Different reasonable probability distributions can be assigned for the coefficient of consolidation, C. But if no more than the first few probability moments of the excess pore pressure and of the degree of consolidation which are functions of C are of concern, it is advantageous to use a simpler, distribution-free method for matching probability moments of C. In this note, the method of discretization of probability is used to analyze one-dimensional consolidation. The solutions, influenced by the probability moments of third, fourth, and fifth order of C, are presented. Key words : probability, discretization, coefficient of consolidation, excess pore pressure, degree of consolidation, moments, random variable.

scholarly journals Performance of THM behavior of sand-bentonite mixtures considering thermal effect

2021 ◽  
Vol 337 ◽  
pp. 01020
Author(s):  
Tomoyoshi Nishimura ◽  
Junichi Koseki
Keyword(s):  
Compressive Strength ◽  
Relative Humidity ◽  
Compression Test ◽  
Unconfined Compressive Strength ◽  
Triaxial Compression ◽  
Radioactive Waste Disposal ◽  
Unconfined Compression ◽  
Unconfined Compression Test ◽  
Sand Mixture ◽  
High Level

This study presented the overview on the behavior of bentonite-sand mixture used in high level radioactive waste disposal. Both unconfined compression test and triaxial compression test were conducted out that unsaturated-saturated bentonite-sand samples were applied temperature effect below 100 degrees Celsius. Unconfined compressive strength was determined with various temperatures and different relative humidity for unsaturated bentonite-sand specimens, so the growing of pore pressure due to heating was most significant for interpretation to THM behaviour of artificial barrier system compositing bentonite materials.

scholarly journals Capability of Pocket Penetrometer to Evaluate Unconfined Compressive Strength of Baghdad Clayey Soil

2018 ◽  
Vol 21 (1) ◽  
pp. 66 ◽  
Author(s):  
Azhar Sadiq Yasun
Keyword(s):  
Compressive Strength ◽  
Moisture Content ◽  
Unconfined Compressive Strength ◽  
Clayey Soil ◽  
Sample Type ◽  
Unconfined Compression ◽  
Unconfined Compression Test ◽  
Test Result

Unconfined compressive strength represents an important parameter for soil investigation report test results because the values of cohesion and allowable bearing capacity can directly obtained from the relevant test especially if the clayey soil layers are found at sufficient enough depth above water table level. This paper deals with simple comparison (based on (31) soil samples) between unconfined compressive strength (qu) obtained by using the pocket soil penetrometer tool and the unconfined compressive strength using the conventional test for the same sample penetrated by the pocket penetrometer with different soil moisture contents. Two triaxial specimens, sample type-1- with dimensions 38 X 79mm and type-2- with dimensions 33 X 79mm(diam. X height)) prepared in the libratory. It was found that the results refers that soil pocket penetrometer readings are closed enough to the results that obtained from the unconfined compression test result with certain conditions. The average percentage of difference between penetrometer readings and unconfined compression test result values was (1.103%) for sample type-1- and (1.53%) for sample type -2-. The maximum moisture content for all tests samples was (27.3%) and the minimum was (14.7%) while the average moisture content was(20.9%).

scholarly journals Comparison of the Use of Cement, Gypsum, and Limestone on the Improvement of Clay through Unconfined Compression Test

2019 ◽  
Vol 5 (2) ◽  
pp. 131
Author(s):  
Ika Puji Hastuty
Keyword(s):  
Compressive Strength ◽  
Shear Strength ◽  
Soil Properties ◽  
Compression Test ◽  
Unconfined Compressive Strength ◽  
Soil Stabilization ◽  
Unconfined Compression ◽  
Unconfined Compression Test ◽  
Limestone Soil ◽  
Materials Used

Soil stabilization is an effort to improve soil properties by adding additives in the soil to increase the soil strength and maintain the shear strength of the soil. There are many materials which can be used as stabilizers. The materials used in this study were cement, gypsum, and limestone, then the compressive strength values were compared by using the Unconfined Compression Test (UCT). The mixture combinations used in this study were 1% to 10% of cement, gypsum, and limestone on clay by curing for 14 days. The compressive strength value resulted from the unconfined compression test on the original soil sample was 1.4 kg/cm2. The original soil was classified as moderately sensitive soil because the sensitivity value of the original soil was 2. After being stabilized with various mixtures of cement, gypsum, and limestone, soil stabilization using cement obtained the maximum unconfined compressive strength value is 3.681 kg/cm2 in the mixture of 10%. Similarly, the soil stabilization using limestone and gypsum also obtained its maximum unconfined compressive strength value in the mixture of 10% is 3.307 kg/cm2 and 2.975 kg/cm2, respectively.

Undrained shear behaviour of sands subjected to large shear displacement and estimation of excess pore-pressure generation from drained ring shear tests

2005 ◽  
Vol 42 (3) ◽  
pp. 787-803 ◽  
Author(s):  
Yasuhiko Okada ◽  
Kyoji Sassa ◽  
Hiroshi Fukuoka
Keyword(s):  
Pore Pressure ◽  
Triaxial Compression ◽  
Excess Pore Pressure ◽  
Compression Tests ◽  
Shear Tests ◽  
Ring Shear ◽  
Ring Shear Tests ◽  
Triaxial Compression Tests ◽  
Undrained Shear ◽  
Excess Pore

Undrained shear behaviour of fine silica and weathered granitic sand subjected to large shear displacement is examined. Parallel experiments using ring shear and the triaxial compression tests on soil specimens through a wide range of initial void ratios were conducted to investigate undrained shear strength as the key factor in the flow-like motion of landslides. The steady-state undrained shear strengths achieved in ring shear tests were, in general, smaller than those in the triaxial compression tests, probably because of the excess pore-pressure generation by grain crushing within the shear zone that occurred in ring shear. Very low steady-state shear strengths were achieved, however, in triaxial compression tests on the dense silica sand in which well-defined shear surfaces developed in the cylindrical specimens. In these triaxial compression tests, shear deformation must have been concentrated on these surfaces to generate excess pore pressure similar to that found in ring shear tests. An attempt was made to estimate excess pore pressure generated in undrained ring shear tests using the results of drained ring shear tests. The equivalent normal stress calculated as the ratio of volumetric strain in the drained test to the coefficient of volume change was introduced as a parameter for the estimation of excess pore-pressure generation for the large shear displacement that is usually found in landslides. Equivalent normal stress from drained tests was almost the same as the generated excess pore pressure in undrained tests with up to 1 m of shear displacement, at which the steady state was reached.Key words: undrained shear strength, excess pore pressure, equivalent normal stress, ring shear test, triaxial compression test, liquefaction.

scholarly journals Compression and Strain Predictive Models in Non-Structural Recycled Concretes Made from Construction and Demolition Wastes

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3177
Author(s):  
Evelio Teijón-López-Zuazo ◽  
Jorge López-Rebollo ◽  
Luis Javier Sánchez-Aparicio ◽  
Roberto Garcia-Martín ◽  
Diego Gonzalez-Aguilera
Keyword(s):  
Compressive Strength ◽  
Predictive Models ◽  
Unconfined Compressive Strength ◽  
Image Correlation ◽  
Peak Strain ◽  
Compression Tests ◽  
Maximum Peak ◽  
3D Digital Image Correlation ◽  
Granulometric Analysis ◽  
Physical And Chemical

This work aims to investigate different predictive models for estimating the unconfined compressive strength and the maximum peak strain of non-structural recycled concretes made up by ceramic and concrete wastes. The extensive experimental campaign carried out during this research includes granulometric analysis, physical and chemical analysis, and compression tests along with the use of the 3D digital image correlation as a method to estimate the maximum peak strain. The results obtained show that it is possible to accurately estimate the unconfined compressive strength for both types of concretes, as well as the maximum peak strain of concretes made up by ceramic waste. The peak strain for mixtures with concrete waste shows lower correlation values.

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