scholarly journals Undrained Cyclic Response and Resistance of Saturated Calcareous Sand considering Initial Static Shear Effect

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Baojian Li ◽  
Panpan Guo ◽  
Gaoyun Zhou ◽  
Zhe Wang ◽  
Gang Lei ◽  
...  
Keyword(s):  
Shear Stress ◽  
Relative Density ◽  
Shear Stresses ◽  
Loose Sand ◽  
Calcareous Sand ◽  
Cyclic Shear ◽  
Cyclic Response ◽  
Dense Sand ◽  
Cyclic Resistance ◽  
Static Shear

Sand elements in the natural or manmade field have often undergone initial static shear stresses before suffering cyclic loading. To explore the effect of static shear stress, a series of undrained cyclic triaxial tests were performed on dense and loose calcareous sand under different initial and cyclic shear stresses. The triaxial test results are used to describe the effect of static shear stress on the cyclic response of the calcareous sand with different relative density. Cyclic mobility, flow deformation, and residual deformation accumulation are the three main failure modes under varying static and cyclic shear stress levels. The cyclic resistance of dense sand is greater than that of loose sand, but the initial static stress has different effects on the cyclic resistance of the two kinds of sand. The dense sand owns a higher cyclic resistance with SSR increasing, while for the loose sand, 0.12 is the critical SSR corresponding to the lowest value of the cyclic resistance. The dense sand has more fast accumulation of dissipated energy, compared with loose sand. Additionally, an exponential relationship is established between static shear stress, relative density, and normalized energy density.

scholarly journals A Monotonic Smeared Truss Model to Predict the Envelope Shear Stress—Shear Strain Curve for Reinforced Concrete Panel Elements under Cyclic Shear

2021 ◽  
Vol 2 (1) ◽  
pp. 174-194
Author(s):  
Luís Bernardo ◽  
Saffana Sadieh
Keyword(s):  
Shear Stress ◽  
Reinforced Concrete ◽  
Shear Strain ◽  
Peak Load ◽  
Strain Curve ◽  
Fiber Reinforced Polymers ◽  
Shear Stresses ◽  
Cyclic Shear ◽  
Concrete Panels ◽  
Truss Model

In previous studies, a smeared truss model based on a refinement of the rotating-angle softened truss model (RA-STM) was proposed to predict the full response of structural concrete panel elements under in-plane monotonic loading. This model, called the “efficient RA-STM procedure”, was validated against the experimental results of reinforced and prestressed concrete panels, steel fiber concrete panels, and reinforced concrete panels externally strengthened with fiber-reinforced polymers. The model incorporates equilibrium and compatibility equations, as well as appropriate smeared constitutive laws of the materials. Besides, it incorporates an efficient algorithm for the calculation procedure to compute the solution points without using the classical trial-and-error technique, providing high numerical efficiency and stability. In this study, the efficient RA-STM procedure is adapted and checked against some experimental data related to reinforced concrete (RC) panels tested under in-plane cyclic shear until failure and found in the literature. Being a monotonic model, the predictions from the model are compared with the experimental envelopes of the hysteretic shear stress–shear strain loops. It is shown that the predictions for the shape (at least until the peak load is reached) and for key shear stresses (namely, cracking, yielding, and maximum shear stresses) of the envelope shear stress–shear strain curves are in reasonably good agreement with the experimental ones. From the obtained results, the efficient RA-STM procedure can be considered as a reliable model to predict some important features of the response of RC panels under cyclic shear, at least for a precheck analysis or predesign.

Confining stress and static shear effects in cyclic liquefaction

2001 ◽  
Vol 38 (3) ◽  
pp. 580-591 ◽  
Author(s):  
Y P Vaid ◽  
J D Stedman ◽  
S Sivathayalan
Keyword(s):  
Initial Density ◽  
Confining Pressure ◽  
Empirical Method ◽  
Shear Stresses ◽  
Confining Stress ◽  
Liquefaction Resistance ◽  
Sand Liquefaction ◽  
Cyclic Resistance ◽  
Cyclic Resistance Ratio ◽  
Static Shear

Liquefaction resistance of a sand under cyclic loading is assessed and the effects of the levels of confining pressure and static shear on resistance to liquefaction are investigated. Site-specific values of the resistance under specified levels of confining and static shear stresses are measured in the laboratory. The measured values are compared with those which would be predicted by the application of empirical multiplying factors Kσ and Kα to the reference resistance at 100 kPa effective confining stress with no static shear. It is shown that Kσ and Kα are not independent, as assumed in current practice. The combined factor Kσ × Kα resulting from the empirical method is shown to underestimate the cyclic resistance ratio regardless of the initial density and confining and static shear levels. The degree of conservatism is most dramatic at looser density states.Key words: sand, liquefaction, static, cyclic, static shear, confining stress.

scholarly journals UNDRAINED CYCLIC SHEAR BEHAVIOR OF SAND AND CLAY MIXTURE SUBJECTED TO INITIAL STATIC SHEAR STRESS

2006 ◽  
Vol 62 (1) ◽  
pp. 240-245 ◽  
Author(s):  
Masayuki HYODO ◽  
Jonggun KIM ◽  
Keisuke FUKUMOTO ◽  
Suguru YAMADA ◽  
Norimasa YOSHIMOTO
Keyword(s):  
Shear Stress ◽  
Shear Behavior ◽  
Cyclic Shear ◽  
Static Shear

scholarly journals Flow liquefaction potential of loose sand: stress path envelope and energy–based evaluation

2020 ◽  
Author(s):  
Kun Pan ◽  
Zhongxuan Yang ◽  
Yuanqiang Cai
Keyword(s):  
Axial Strain ◽  
Stress Path ◽  
Dissipated Energy ◽  
Loose Sand ◽  
Liquefaction Potential ◽  
Cyclic Shear ◽  
Cyclic Resistance ◽  
Potential Applicability ◽  
Potential Evaluation ◽  
Flow Liquefaction

Flow liquefaction, which is characterized by sudden collapse following the unstable behavior of saturated loose sand, may lead to the most catastrophic consequence of all liquefaction–related phenomena. This note presents a systematic experimental investigation into the flow liquefaction potential of sand under various initial and cyclic shear conditions. The cyclic flow liquefaction responses are compared to the monotonic shear results under an identical initial testing condition. It is found that the effective stress path of a monotonic test appears to envelop that of its corresponding cyclic test. The energy–based liquefaction potential evaluation indicates that the accumulative dissipated energy is uniquely correlated not only with the pore pressure and axial strain induced in sand, but also with the degraded stiffness during cyclic loading. Furthermore, the energy capacity for triggering the flow liquefaction appears to be intimately related to the cyclic resistance of sand; this signifies the potential applicability of energy–based liquefaction potential evaluation using strength data available in conventional analysis.

scholarly journals Empirical Studies of Ice Sliding

1979 ◽  
Vol 23 (89) ◽  
pp. 157-170 ◽  
Author(s):  
W. F. Budd ◽  
P. L. Keage ◽  
N. A. Blundy
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Sliding Friction ◽  
Normal Load ◽  
Water Pressure ◽  
Empirical Studies ◽  
Shear Stresses ◽  
Friction Characteristic ◽  
Wide Range ◽  
Static Shear

AbstractAn experimental programme has been carried out for studying temperate-ice sliding over rock surfaces with a wide range of roughnesses, for normal and shear stresses comparable to those expected under real ice masses. The limiting static shear stress for acceleration has been found to be directly proportional to the normal load giving a constant limiting coefficient of static friction characteristic of the surface. For a constant applied normal stress N and shear stress τb, well below the limiting static shear, a steady velocity Vb results which increases approximately proportionally to τb and decreases with increasing N and the roughness of the surface. For high normal stress the velocity becomes approximately proportional to the shear stress cubed and inversely proportional to the normal stress. As the shear stress increases acceleration sets in, which, for different roughness and normal loads, tends to occur for a constant value of the product τbVb. For some surfaces at high normal loads this acceleration was retarded by erosion. For constant-applied-velocity tests a steady shear stress resulted, which tended to become constant with high velocities, and which increased with increasing normal stress but with a reduced coefficient of sliding friction. The relevance of the results to the sliding of real ice masses is discussed with particular reference to the importance of the effect of the relative normal stress, above basal water pressure, to the sliding rate.

Effect of relative density and biocementation on cyclic response of calcareous sand

2019 ◽  
Vol 56 (12) ◽  
pp. 1849-1862 ◽  
Author(s):  
Peng Xiao ◽  
Hanlong Liu ◽  
Armin W. Stuedlein ◽  
T. Matthew Evans ◽  
Yang Xiao
Keyword(s):  
Calcium Carbonate ◽  
Relative Density ◽  
Pore Pressure ◽  
Soil Particle ◽  
Engineering Properties ◽  
Excess Pore Pressure ◽  
Calcareous Sand ◽  
Sem Images ◽  
Cyclic Response ◽  
Excess Pore

Microbial-induced calcium carbonate precipitation (MICP) represents a promising approach to improve the geotechnical engineering properties of soils through the precipitation of calcium carbonate (CaCO3) at soil particle contacts and soil particle surfaces. An extensive experimental study was undertaken to investigate the influence of initial relative density on the efficiency of the biocementation process, the reduction of liquefaction susceptibility, and the cyclic response in biocemented calcareous soils. For this purpose, stress-controlled undrained cyclic triaxial shear (CTS) tests were carried out on untreated and MICP-treated calcareous sand specimens for different initial relative densities and magnitudes of biocementation. Improvement in the cyclic response was quantified and compared in terms of excess pore pressure generation, evolution of axial strains, and the number of cycles to liquefaction. The cyclic experiments show that MICP treatment can change the liquefaction failure mechanism from flow failure to cyclic mobility and can significantly change the excess pore pressure generation response of initially loose specimens. Scanning electron microscope (SEM) images indicate the CaCO3 crystals alter the characteristics of the sand particles and confirm the physical change in soil fabric that impacts the dynamic behavior and liquefaction resistance of MICP-treated specimens. Furthermore, the effect of biocementation was contrasted against the effect of relative density alone, and MICP treatment was shown to exhibit greater efficiency in improving the cyclic resistance than densification.

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