SOME OBSERVATIONS ON THE UNDRAINED SHEARING STRENGTH USED TO ANALYZE A FAILURE

1969 ◽  
Vol 6 (2) ◽  
pp. 97-110 ◽  
Author(s):  
F. A. De Lory ◽  
R. J. Salvas
Keyword(s):  
Clay Soils ◽  
Triaxial Tests ◽  
Silty Clay ◽  
Compression Tests ◽  
Foundation Soil ◽  
Shearing Strength

The undrained shearing strength of the foundation soil at the site of a failure of a low embankment was investigated by several methods. It was found that both field vane and laboratory compression tests tended to underestimate the strength required for stability. Further consideration of the test specimens from sample tubes showed the undrained shearing strength varied considerably with the position of the sample in the tube. Specimens from tubes from another site yield the same type of results. The two silty clay soils involved were studied in more detail using CIU and CAU triaxial tests and comparing cu/p′ ratios. It was found that in general they yielded the values usually obtained for lacustrine clays.

scholarly journals Research of the Behavior of Clay Materials with Double Porosity

2021 ◽  
Vol 13 (6) ◽  
pp. 3219
Author(s):  
Hynek Lahuta ◽  
Luis Andrade Pais
Keyword(s):  
Double Porosity ◽  
Strength Properties ◽  
Triaxial Tests ◽  
Building Structures ◽  
Foundation Soil ◽  
Problematic Use ◽  
The North ◽  
Static Liquefaction ◽  
Confinement Stress ◽  
Clay Materials

This contribution presents results from a series of compression and undrained triaxial tests to study the mechanical behavior of dump clay from the north of Bohemia. The use of these materials as a foundation for construction can’t be achieved without the adoption of some precautions. This comes from embankment, formed by digging the ground (altered claystone), up to the level of coal mining which is in a sub horizontal stratigraphic layer. A potential static liquefaction behavior was observed in undrained tests for high confinement stress. A structural collapse was noticed with the results obtained in the triaxial test. This collapse is characterized by an unexpected large decrease in deviator and mean effective stress. The soils formed have strength properties that are potentially dangerous. These concepts can improve the use of these kinds of soils in geotechnical engineering work. It continues and expands the results obtained in previous research, especially the future problematic use of these materials as the foundation soil for line or building structures.

Strength envelope of granular soil stabilized by multi-axial geogrid in large triaxial tests

2020 ◽  
Vol 57 (3) ◽  
pp. 448-452 ◽  
Author(s):  
A.S. Lees ◽  
J. Clausen
Keyword(s):  
Triaxial Compression ◽  
Triaxial Tests ◽  
Compression Tests ◽  
Failure Envelope ◽  
Element Analysis ◽  
Linear Elastic ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic ◽  
Triaxial Compression Tests ◽  
Properties Of Soil

Conventional methods of characterizing the mechanical properties of soil and geogrid separately are not suited to multi-axial stabilizing geogrid that depends critically on the interaction between soil particles and geogrid. This has been overcome by testing the soil and geogrid product together as one composite material in large specimen triaxial compression tests and fitting a nonlinear failure envelope to the peak failure states. As such, the performance of stabilizing, multi-axial geogrid can be characterized in a measurable way. The failure envelope was adopted in a linear elastic – perfectly plastic constitutive model and implemented into finite element analysis, incorporating a linear variation of enhanced strength with distance from the geogrid plane. This was shown to produce reasonably accurate simulations of triaxial compression tests of both stabilized and nonstabilized specimens at all the confining stresses tested with one set of input parameters for the failure envelope and its variation with distance from the geogrid plane.

Evaluation on Features of Soft Foundation Engineering and Bearing Layer of Pile in Jiaxing City

2011 ◽  
Vol 90-93 ◽  
pp. 217-221
Author(s):  
Jin Long Zhou ◽  
Qiao Li ◽  
Wei Zhong Cai
Keyword(s):  
Soil Mass ◽  
Shallow Foundation ◽  
Silty Clay ◽  
Foundation Engineering ◽  
Foundation Soil ◽  
Cone Tip Resistance ◽  
Soft Foundation ◽  
Tip Resistance ◽  
Bearing Layer

Through the investigation into composition of major shallow foundation soil mass and the correlation of mechanical indicators in this study, the regression equation of mechanical indicators of the features of local foundation soil mass and the data of in situ testing was obtained. Based on massive quantities of exploration materials, this study analyzed engineering features, distribution status, and the feasibility of silty clay to be used as the bearing layer of the pile in Layer ④2 . The analytical results showed that the silty clay with the uniform depth of over 3.5m and the cone tip resistance in static sounding of over 400MPa could be used as bearing layer of the pile. This study could provide the reference for the accurate understanding of the engineering features of soil mass, and the design and evaluation of foundation in Jiaxing City.

scholarly journals Experimental Study of Stress-Seepage Coupling Properties of Sandstone under Different Loading Paths

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-21
Author(s):  
Xi Chen ◽  
Wei Wang ◽  
Yajun Cao ◽  
Qizhi Zhu ◽  
Weiya Xu ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Pore Pressure ◽  
Complex Loading ◽  
Friction Angle ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Compression Tests ◽  
Biot Coefficient ◽  
Cyclic Loading And Unloading ◽  
Loading And Unloading

The study on hydromechanical coupling properties of rocks is of great importance for rock engineering. It is closely related to the stability analysis of structures in rocks under seepage condition. In this study, a series of conventional triaxial tests under drained condition and hydrostatic compression tests under drained or undrained condition on sandstones were conducted. Moreover, complex cyclic loading and unloading tests were also carried out. Based on the experimental results, the following conclusions were obtained. For conventional triaxial tests, the elastic modulus, peak strength, crack initiation stress, and expansion stress increase with increased confining pressure. Pore pressure weakened the effect of the confining pressure under drained condition, which led to a decline in rock mechanical properties. It appeared that cohesion was more sensitive to pore pressure than to the internal friction angle. For complex loading and unloading cyclic tests, in deviatoric stress loading and unloading cycles, elastic modulus increased obviously in first loading stage and increased slowly in next stages. In confining pressure loading and unloading cycles, the Biot coefficient decreased first and then increased, which indicates that damage has a great impact on the Biot coefficient.

scholarly journals Resilient modulus and cumulative plastic strain of frozen silty clay under dynamic aircraft loading

2021 ◽  
Vol 3 (10) ◽  
Author(s):  
Xiaolan Liu ◽  
Xianmin Zhang ◽  
Xiaojiang Wang
Keyword(s):  
Plastic Strain ◽  
Resilient Modulus ◽  
Confining Pressure ◽  
Frozen Soil ◽  
Triaxial Tests ◽  
Silty Clay ◽  
Research Findings ◽  
Cumulative Plastic Strain ◽  
Construction Operation ◽  
Compaction Degree

AbstractThis paper describes an investigation into the factors influencing the resilient modulus and cumulative plastic strain of frozen silty clay. A series of dynamic triaxial tests are conducted to analyze the influence of the temperature, confining pressure, frequency, and compaction degree on the resilient modulus and cumulative plastic strain of frozen silty clay samples. The results show that when the temperature is below − 5 °C, the resilient modulus decreases linearly, whereas when the temperature is above − 5 °C, the resilient modulus decreases according to a power function. The resilient modulus increases logarithmically when the frequency is less than 2 Hz and increases linearly once the frequency exceeds 2 Hz. The resilient modulus increases as the confining pressure and compaction degree increase. The cumulative plastic strain decreases as the temperature decreases and as the confining pressure, frequency, and compaction degree increase. The research findings provide valuable information for the design, construction, operation, maintenance, safety, and management of airport engineering in frozen soil regions.

Thermodynamic-based cross-scale model for structural soil with emphasis on bond dissolution

2021 ◽  
Author(s):  
Wei Zhang ◽  
Jia-qiang Zou ◽  
Kang Bian ◽  
Yang Wu
Keyword(s):  
Constitutive Model ◽  
Bond Strength ◽  
Scale Model ◽  
Triaxial Tests ◽  
Natural Soil ◽  
Engineering Practice ◽  
Compression Tests ◽  
Strength Deterioration ◽  
Decomposed Granite ◽  
Completely Decomposed Granite

The immersion weakening effect of natural soil has always been a difficult problem encountered in geotechnical engineering practice. The bond dissolution is a common cause of soil strength deterioration, which remains not well understood yet. In this study, a thermodynamic-based constitutive model of structural soils based on the α model is first established, considering the bond strength by modifying the yield surface size and gradually reducing the bond strength with the development of plastic strain. Furthermore, by taking the meso-mechanisms of bond dissolution into account, the evolution rule of the free energy during the bond dissolution process is derived based on a homogenization approach, and a thermodynamic-based constitutive model of structural soil with bond dissolution is thereafter developed. By comparing with the results of one-dimensional compression tests and conventional triaxial tests, the model is verified to be capable of reflecting the gradual destructuration process of soil while loading. The comparison with triaxial test results of completely decomposed granite after different immersion durations and parametric studies show that based on the cross-scale energy equivalence, the model can well reflect the strength deterioration characteristics of completely decomposed granite with bond dissolution mechanisms at the mesoscale fully considered.

Deep sampling and testing in soft stratified clay

2003 ◽  
Vol 40 (3) ◽  
pp. 575-586 ◽  
Author(s):  
Simon James Cummings ◽  
Vinayagamoorthy Sivakumar ◽  
Isaac Gregg Doran ◽  
Jim Graham
Keyword(s):  
Triaxial Compression ◽  
Relevant Literature ◽  
Thick Layer ◽  
Site Investigation ◽  
Anisotropic Elasticity ◽  
Triaxial Tests ◽  
Compression Tests ◽  
Lower Zone ◽  
A Site ◽  
Triaxial Compression Tests

A 37-m thick layer of stratified clay encountered during a site investigation at Swann's Bridge, near the sea-coast at Limavady, Northern Ireland, is one of the deepest and thickest layers of this type of material recorded in Ireland. A study of the relevant literature and stratigraphic evidence obtained from the site investigation showed that despite being close to the current shoreline, the clay was deposited in a fresh-water glacial lake formed approximately 13 000 BP. The 37-m layer of clay can be divided into two separate zones. The lower zone was deposited as a series of laminated layers of sand, silt, and clay, whereas the upper zone was deposited as a largely homogeneous mixture. A comprehensive series of tests was carried out on carefully selected samples from the full thickness of the deposit. The results obtained from these tests were complex and confusing, particularly the results of tests done on samples from the lower zone. The results of one-dimensional compression tests, unconsolidated undrained triaxial tests, and consolidated undrained triaxial compression tests showed that despite careful sampling, all of the specimens from the lower zone exhibited behaviour similar to that of reconstituted clays. It was immediately clear that the results needed explanation. This paper studies possible causes of the results from tests carried out on the lower Limavady clay. It suggests a possible mechanism based on anisotropic elasticity, yielding, and destructuring that provides an understanding of the observed behaviour.Key words: clay, laminations, disturbance, yielding, destructuring, reconstituted.

scholarly journals Applicability of wetting front advancing method in the sand to silty clay soils

2020 ◽  
Vol 60 (5) ◽  
pp. 1215-1225
Author(s):  
Qiang Liu ◽  
Ping Xi ◽  
Jiali Miao ◽  
Xiaochen Li ◽  
Ke Wang
Keyword(s):  
Clay Soils ◽  
Silty Clay ◽  
Wetting Front

Photogrammetry-Based Method to Determine the Absolute Volume of Soil Specimen during Triaxial Testing

2020 ◽  
Vol 2674 (8) ◽  
pp. 206-218
Author(s):  
Sara Fayek ◽  
Xiaolong Xia ◽  
Lin Li ◽  
Xiong Zhang
Keyword(s):  
Unsaturated Soils ◽  
Optimization Techniques ◽  
Triaxial Tests ◽  
Triaxial Testing ◽  
Soil Specimen ◽  
Compression Tests ◽  
Unconfined Compression ◽  
Absolute Volume ◽  
Triaxial Cell ◽  
The Absolute

Triaxial tests are used extensively to evaluate stress-strain behavior for both saturated and unsaturated soils. A literature review indicates that all conventional triaxial test methods measure the relative volume of soil; however, between the initial measurements and the start of the triaxial tests, there are unavoidably disturbances during installation that cause deviation of soil volume from that at the initial condition. Recently image-based methods have been developed to measure the absolute volume of soil specimens. However, these methods still have a major limitation in their inability to determine top and bottom boundaries between the soil specimen, and the top and bottom caps. This paper proposes a photogrammetry-based method to overcome this limitation by developing a mathematically rigorous technique to determine the upper and lower boundaries of soil specimens during triaxial testing. The photogrammetry technique was used to determine the orientations of the camera, and the shape and location of the acrylic cell. Multiple ray-tracings and least-square optimization techniques were also applied to obtain the coordinates of any point inside the triaxial cell, and thus back-calculate the upper and lower boundaries. With these boundaries and the side surface, a triangular surface mesh was constructed and the specimen volume was then calculated in both unconfined compression tests and triaxial tests. The calculation procedures are presented in detail with validation tests performed on a cylindrical specimen to evaluate the accuracy of the method. Results indicate that the accuracy of the proposed method is up to 0.023% in unconfined compression tests and 0.061% in triaxial tests.

scholarly journals Microbial biodiversity as related to crop succession and potato intercropping for management of brown rot disease

2019 ◽  
Vol 29 (1) ◽  
Author(s):  
N. A. S. Messiha ◽  
K. M. A. Elhalag ◽  
N. M. Balabel ◽  
S. M. A. Farag ◽  
H. A. Matar ◽  
...  
Keyword(s):  
Sandy Soils ◽  
Brown Rot ◽  
High Ratio ◽  
Fluorescent Pseudomonads ◽  
Clay Soils ◽  
Silty Clay ◽  
Potato Brown Rot ◽  
Rot Disease ◽  
Bacterial Plant Pathogen ◽  
Crop Succession

AbstractPotato brown rot, caused by Ralstonia solanacearum, ranked globally as the second most important bacterial plant pathogen. In the present study, the influence of different cropping programs in potato brown rot management was investigated in four infected fields in Egypt. Two districts were selected as sandy soils in Giza (Wardan) and Behera (Ganuob El-Tahrir) governorates. The other two were selected as silty clay in Minufyia (Talia) and Beni-Suef (Sids) governorates. The followed crop succession included corn, potato intercropped with cabbage, onion, cowpea, wheat, corn again, and ended by potato. The pathogen was undetectable after corn, onion, and wheat. It decreased in cowpea and cabbage rhizospheres in the clay soils. The pathogen was undetectable at all districts, except at Sids, where the pathogen was significantly decreased but was not eradicated. This was possibly attributed to the high ratio of NO3− and Na+ at this district. Decreased R. solanacearum density after corn coincided with the high ratio of fluorescent pseudomonads, endospores, and actinomycetes, being most clear in the poor soils (Wardan) and less clear under iron excess at Ganoub El-Tahrir as well as the clay soils. Corn rhizosphere supported an array of antagonistic actinomycetes such as strains similar to Streptomyces intermedius, Streptomyces albidoflavus group, Streptomyces argenteolus group, and Streptomyces erythrogriseus. Intercropping potato with cabbage decreased the density of the pathogen in rhizosphere, which is associated with greater antagonistic fluorescent pseudomonads, Bacillus spp. and Serratia spp. Onion soil and rhizosphere associated with abundance of antagonists and fluorescent pseudomonads, followed by S. maltophilia and Bacillus spp. Wheat soil and rhizosphere supported fluorescent pseudomonads and antagonistic Streptomyces spp., especially in sandy soils. The pathogen was undetectable after planting the ending potato in the three districts, Wardan, Ganoub El-Tahrir, and Talia. This was accompanied by a general oligotrophism and increased ratio of fluorescent pseudomonads, endospores bacteria, and actinomycetes along with a diversity of R. solanacearum antagonists such as S. maltophilia, Citrobacter freundii, Acinetobacter sp., Delftia sp., and Serratia marcescens.

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