Comparison of the Dynamic Properties and Undrained Shear Strengths of Offshore Calcareous Sand and Artificially Cemented Sand

2003 ◽  
Author(s):  
Celestino Valle ◽  
Beatriz I. Camacho ◽  
Kenneth H. Stokoe ◽  
Alan F. Rauch
Keyword(s):  
Sodium Silicate ◽  
Dynamic Properties ◽  
Triaxial Compression ◽  
Calcareous Soils ◽  
Sodium Silicate Solution ◽  
Small Strain ◽  
Compression Tests ◽  
Calcareous Sand ◽  
Cemented Sand ◽  
Undrained Shear

Calcareous sand specimens were obtained from Campeche Bay in the southern Gulf of Mexico. The dynamic properties of these specimens were measured in resonant column and torsional shear (RCTS) tests, while the undrained shear strength was measured in unconsolidated-undrained (UU) triaxial compression tests. For weakly cemented, natural materials like this, it is difficult to obtain reliable properties from laboratory tests because sampling and handling of the soil specimens damages the particle cementation to an unknown degree. Artificially cemented specimens can be studied to better understand this problem. In this work, the strength and dynamic properties of artificially cemented sand were also measured using RCTS and UU tests. The artificially cemented specimens were formed by mixing uniform sand with a sodium silicate solution. The degree of cementation was varied by using different sodium silicate concentrations. This approach could be used to reproduce cemented test specimens in the laboratory with similar mechanical properties as cemented offshore soils. The results from this limited study show that the small-strain dynamic properties measured in the laboratory, and their variation with confining pressure, clearly identifies disturbance in the calcareous soils.

Static and dynamic properties of a lightly cemented silicate-grouted sand

2012 ◽  
Vol 49 (10) ◽  
pp. 1117-1133 ◽  
Author(s):  
Daniela Porcino ◽  
Vincenzo Marcianò ◽  
Raffaella Granata
Keyword(s):  
Dynamic Properties ◽  
Triaxial Compression ◽  
High Stress ◽  
Small Strain ◽  
Compression Tests ◽  
Bender Elements ◽  
Liquefaction Resistance ◽  
Cyclic Shear ◽  
Loose Medium ◽  
Triaxial Compression Tests

This paper describes the results of an experimental investigation on the behaviour of a lightly grouted loose medium sand under both monotonic and cyclic loading. The experimental programme in the present study was carried out on both untreated and treated sand specimens stabilized with a silica-based grout, and comprises isotropic triaxial compression tests equipped with bender elements, drained triaxial monotonic shearing tests, and undrained cyclic tests in a simple shear (SS) apparatus. The results highlight that the weak cementation level induced by chemical treatment was sufficient to moderately increase small-strain stiffness and stress–dilatancy of the grouted sand during drained monotonic shear. A small cohesion intercept was observed in the analyzed failure envelope, while cyclic liquefaction resistance exhibited a much more significant increase, with a different pattern of behaviour between low and high stress levels. Finally, undrained cyclic SS test results evidenced that silicate grout employed in this research improves undrained cyclic shear strength in a manner similar to densification of the same material up to a density index of approximately 75%.

scholarly journals Effect of Fiber and Cement Additives on the Small-Strain Stiffness Behavior of Toyoura Sand

2020 ◽  
Vol 12 (24) ◽  
pp. 10468
Author(s):  
Muhammad Safdar ◽  
Tim Newson ◽  
Colin Schmidt ◽  
Kenichi Sato ◽  
Takuro Fujikawa ◽  
...  
Keyword(s):  
Model Comparison ◽  
Local Strain ◽  
Small Strain ◽  
Experimental Results ◽  
Compression Tests ◽  
Cemented Sand ◽  
Strain Measurements ◽  
Good Comparison ◽  
Toyoura Sand ◽  
Comparison Of The Results

The disposal of 2011 Japan earthquake waste has become an important issue in Japan and it is not realistic or economical to send all of these wastes to landfill sites, due to limited space, high costs, and related environmental issues. In sustainable geotechnical applications, mixing of the separated soils from disaster wastes with additives (e.g., cement and fiber) is required to improve their strength and stiffness characteristics. In this study, monotonic triaxial drained compression tests are performed on medium dense specimens of Toyoura sand-cement-fiber mixtures with different percentages of fiber and cement (e.g., 0–3%) additives. The experimental results indicate that behavior of the mixtures is significantly affected by the concentration of fiber and cement additives. Based on a comprehensive set of test results, modifications to the series of equations were developed that can be used to evaluate the shear modulus and mobilized stress curves at small-strain levels. The experimental results and model comparison show that the elastic threshold strain (γe), reference strain (γr), increases with fiber and cement additives. In addition, the range of curvature parameter, from 0.88 to 1.0, provides a good comparison with the results of small-strain measurements. Overall, the comparison of the results and model shows that the small-strain measurements obtained using local strain transducers fall within the range of model upper and lower bound curves. The results of the unreinforced, fiber, and cemented sand shows a close agreement with the model mean curve, but fiber-reinforced cemented sand shows a good comparison with model upper bound.

scholarly journals Interpretation of undrained shear strength observed in confined triaxial compression tests on compacted clay

2021 ◽  
Author(s):  
Chee K. Wong ◽  
Martin Lun ◽  
Ron C.K. Wong
Keyword(s):  
Shear Strength ◽  
Unsaturated Soil ◽  
Water Pressure ◽  
Triaxial Compression ◽  
Undrained Shear Strength ◽  
Compacted Clay ◽  
Compression Tests ◽  
Basic Model ◽  
Triaxial Compression Tests ◽  
Undrained Shear

This paper presents an interpretation technique to quantify the effects of compaction state and matric suction on the undrained shear strength of compacted clay under confined undrained triaxial compression. This novel technique is based on the mathematical frameworks of SHANSEP (Stress History and Normalized Soil Engineering Property) method for saturated soil and BBM (Barcelona Basic model) for unsaturated soil. Test data of compacted Calgary till were analyzed and interpreted using the proposed technique. The interpretation technique is very useful in delineating the relative impacts of the factors on the behavioral trends in measured undrained shear strength. It was found that in addition to the initial compacted void ratio and suction, soil structure and failure mode exert significant influence on the undrained shear strength of compacted clay. This technique is attractive to engineering practitioners because the confined undrained compression tests (with no pore air and water pressure measurement) are much simpler and less time consuming compared to rigorous laboratory tests on unsaturated soil.

scholarly journals Shear Characteristics of Cement-Stabilized Sand Reinforced with Waste Polyester Fiber Fabric Blocks

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Xiangfeng Lv ◽  
Hongyuan Zhou
Keyword(s):  
Low Cost ◽  
Triaxial Compression ◽  
Friction Angle ◽  
Polyester Fiber ◽  
Peak Strain ◽  
Compression Tests ◽  
Initial Stiffness ◽  
Cemented Sand ◽  
Aspect Ratios ◽  
Fiber Fabric

The present paper is devoted to investigate the effects of waste polyester fiber fabric blocks on the strength and mechanical behavior of cemented sand. In the investigation, samples were prepared at four different percentages of waste polyester fiber fabric block content (0.0%, 0.5%, 1.0%, and 1.5% by weight of soil) and two different aspect ratios (2 : 1 and 3 : 1), and conventional triaxial compression tests were carried out after the curing period. The test results indicated that the addition of fibers increased peak and residual shear strengths of cemented sand and changed its brittle behavior to a more ductile one. As the fabric block content increased, the brittleness index and initial stiffness decreased, and the peak strain and internal friction angle increased. The optimal combination of the content and aspect ratio was determined to be 0.5% and 3 : 1. The integration of the fabric blocks with the cemented sand matrix was analyzed by using the scanning electron microscopy (SEM). It is found that the reinforcement effect is related to the bond strength and friction at the interface. The micromechanical properties of the fiber/matrix interface were influenced by the undulations between the fabric block components. In summary, this study presented a low-cost and environment-friendly method for reinforcing cement-stabilized sand.

Undrained triaxial strength and stress–strain characteristics of a glacial till soil

1988 ◽  
Vol 25 (3) ◽  
pp. 428-439 ◽  
Author(s):  
J. H. Atkinson ◽  
J. A. Little
Keyword(s):  
Critical State ◽  
Soil Mechanics ◽  
Triaxial Compression ◽  
Practical Importance ◽  
Small Strain ◽  
Compression Tests ◽  
Triaxial Strength ◽  
Current State ◽  
Boulder Clay ◽  
Triaxial Compression Tests

Undrained triaxial compression tests were carried out on reconstituted and nominally undisturbed tubed samples of a lodgement till from the Vale of St. Albans in Hertfordshire, England. The soil is a matrix-dominant, chalky boulder clay of Anglian age with little discernable engineering fabric. Electron microscope observations showed the presence of crystalline calcite in tube samples.The test results were examined within the general framework of critical state soil mechanics using normalizing procedures to take account of the different states and stress histories of the samples. These analyses demonstrate the practical importance of accounting for the current state and stress history in the interpretation of soil test data.The present results form a self-consistent pattern of behaviour. Differences between reconstituted and tubed samples were found only at small strain and may be attributed to cementing in tubed samples, which is broken down during reconstitution and during relatively large straining in recompression and shearing. Key words: boulder clay, cemented soil, critical state, shear strength, soil mechanics, stiffness, till, triaxial test.

Test Study on Dynamic Deformation Behavior of Soft Rock-Concrete Sample under Cyclic Loading

2014 ◽  
Vol 501-504 ◽  
pp. 295-299 ◽  
Author(s):  
Zu De Ding ◽  
Yong Gang Du ◽  
Juan Huang ◽  
Cheng Hua Shi
Keyword(s):  
Dynamic Deformation ◽  
Dynamic Properties ◽  
Triaxial Compression ◽  
Soft Rock ◽  
Dynamic Strain ◽  
Compression Tests ◽  
Deformation Behaviors ◽  
Weak Interlayer ◽  
Good Contact ◽  
Dynamic Deformation Behavior

Considering three contact states of good contact, containing weak interlayer and water, containing weak interlayer but no water, a series of cyclic triaxial compression tests of soft rock-concrete samples for investigation the dynamic deformation behaviors are carried out. The influence of contact states on dynamic properties of combination samples is analyzed based on the dynamic stress-strain curves and accumulative strain curves. The results show that changing the contact states has notable effects on the dynamic strain of the samples. Comparing with the good contact sample, the accumulative strain of the sample containing weak interlayer is about 2 times. The amplitude of the sample vibration increases, while the accumulative strain reduces with the increase of the vibration frequency. It can be noted that the measures such as assuring construction quality, removing weak interlayer and water, keeping good contact state between bedrock and tunnel structure can reduce the settlements and improve the tunnel service life.

scholarly journals Consolidated Undrained Triaxial Compression Tests and Strength Criterion of Solidified Dredged Materials

2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
Jianwen Ding ◽  
Xusong Feng ◽  
Yupeng Cao ◽  
Sen Qian ◽  
Feng Ji
Keyword(s):  
Shear Strength ◽  
Water Pressure ◽  
Triaxial Compression ◽  
Strength Criterion ◽  
Undrained Shear Strength ◽  
Compression Tests ◽  
Dredged Materials ◽  
Strength Evolution ◽  
Triaxial Compression Tests ◽  
Undrained Shear

Consolidated undrained triaxial compression tests were performed to investigate the shear strength behavior of the solidified dredged materials (SDM). The variation law of deviator stress and excess pore water pressure with the increase of the applied confining pressure was investigated. It is found that the shear strength envelope is consisted of two lines, and there exists a transitional stress on the intersection point. The undrained shear strength develops slightly with the increase of applied normal stress in the preyield state. However, the undrained shear strength increases significantly in the postyield state, and the strength envelope is nearly a straight line with the extension through the origin. Based on the triaxial test data and the binary medium model, a strength criterion considering strength evolution mechanism is proposed and the relevant parameters of the strength criterion were discussed. Comparisons of the predicted results and experimental data demonstrate that the proposed strength criterion can properly describe the strength evolution rules of the SDM.

scholarly journals Small-strain deformation behaviour of a clay at frozen and unfrozen states: A comparative study

2019 ◽  
Vol 92 ◽  
pp. 04001
Author(s):  
Satoshi Nishimura ◽  
Shota Okajima ◽  
Jinyuan Wang ◽  
Bhakta Raj Joshi
Keyword(s):  
Strain Rate ◽  
Axial Strain ◽  
Deformation Behaviour ◽  
Triaxial Compression ◽  
Small Strain ◽  
Small Scale ◽  
High Plasticity ◽  
Compression Tests ◽  
Small Strains ◽  
Displacement Sensors

The small-strain deformation behaviour of frozen high-plasticity clay, and the factors influencing it were investigated through parallel tests at frozen and unfrozen states. The first and second series involved temperature-controlled triaxial compression tests on unfrozen and frozen samples, respectively, with accurate strain measurement with local displacement sensors, fully calibrated for cold environment. The small-strain loading was conducted at different axial strain rates and temperatures. At pre-yield small strains in order of 0.001%, Young's modulus was independent of the strain rate, in a same manner as in unfrozen soils. The strain rate only affected the onset of small-scale yielding and the degradation of stiffness after that. The elastic strain range was greater at lower temperature, but the degree of stress-strain non-linearity seen at small strains remained on the whole similar between frozen and unfrozen states. An interesting feature of the frozen clay's stiffness, also confirmed by third test series adopting bender elements, is that it decreases when the soil is frozen from higher effective stress. A simple model was proposed to explain this feature.

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 Stress-dependent behavior of saturated clay

2012 ◽  
Vol 49 (8) ◽  
pp. 907-916 ◽  
Author(s):  
Naeem O. Abdulhadi ◽  
John T. Germaine ◽  
Andrew J. Whittle
Keyword(s):  
Stress Level ◽  
High Pressures ◽  
Large Strain ◽  
Triaxial Compression ◽  
Friction Angle ◽  
Peak Strain ◽  
Compression Tests ◽  
Stress Strain ◽  
Stress Dependent ◽  
Undrained Shear

A program of K0-consolidated undrained triaxial compression tests has been performed to investigate the effects of consolidation stress level on the compression and shear behavior of resedimented Boston blue clay (RBBC). Specimens were consolidated to maximum vertical effective stresses in the range 0.15–10 MPa and tested at three overconsolidation ratios (OCR): 1, 2, and 4. The results show that the virgin compression curves are essentially linear in e–log[Formula: see text] space over the consolidation stress range. However, the normally consolidated K0 stress ratio increases with the level of consolidation stress. The stress–strain–strength properties measured in undrained shear are significantly affected by the consolidation stress level at each OCR and show indications of non-normalizable behavior. At high pressures, the undrained shear stress–strain behavior becomes more ductile, requiring larger strains to mobilize peak resistance and exhibiting less post-peak strain-softening. The undrained strength ratio (su/[Formula: see text]) is not uniquely controlled by OCR as suggested by the SHANSEP equation, but consistently decreases with increasing consolidation effective stress. There is notable reduction in the stiffness ratio (Eu/[Formula: see text]) with stress level, and significant decrease in the large-strain friction angle.

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