scholarly journals Degradation of submerged/wet concrete under cyclic compression and cyclic shear

2019 ◽  
Vol 258 ◽  
pp. 05012
Author(s):  
Chikako Fujiyama ◽  
Yasuhiro Koda ◽  
Noriaki Sento
Keyword(s):  
Water Supply ◽  
Water Pressure ◽  
Cement Matrix ◽  
Cyclic Shear ◽  
Fine Aggregates ◽  
Compressive Loads ◽  
External Water ◽  
Number Of Cycles ◽  
Cyclic Shear Test ◽  
Specific Degradation

The aim of this study is to identify a specific degradation of concrete that has been observed in bridge decks made of reinforced concrete (RC). To control the phenomenon, fundamental studies were conducted. Compressive loads and external water pressure were cyclically applied to submerged concrete cylinder specimens with different pre-loading and restraint conditions. The turbidity of the water in the tank was generally observed during the loading, and the pH of the turbid water steadily increased as the number of cycles increased. Thereafter, fine aggregates without a cement matrix were found on the inner surfaces of split specimens. These phenomena were quantitatively analyzed, and the analyses suggested that cyclic water pressure acted on the inside of pre-cracked specimens and washed out their cement matrix. The degradation of a rough cracked surface was also examined using the cyclic shear test, with/without a water supply to the crack. The shear slip and the orthogonal displacement were clearly amplified with an increase in the number of cycles when the water supply was present. The mechanical properties of cracked concrete with water in shear was discussed in accordance with that of liquefaction. These fundamental studies could help to determine the acceleration factors of the degradation and provide certain thresholds for practical use.

scholarly journals Pore water pressure responses of saturated sand and clay under undrained cyclic shearing

2021 ◽  
Author(s):  
An ◽  
Hiroshi ◽  
Nhan ◽  
Nhan ◽  
Tien ◽  
...  
Keyword(s):  
Shear Strain ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Silty Clay ◽  
Shear Tests ◽  
Sand Liquefaction ◽  
Cyclic Shear ◽  
Wide Range ◽  
Number Of Cycles

In this study, changes in the pore water pressure were observed for saturated specimens of a loose fined-grain sand (Nam O sand) and a soft silty clay (Hue clay) subjected to undrained cyclic shearing with different testing conditions. The cyclic shear tests were run for relatively wide range of shear strain amplitude (g = 0.05%-2%), different cycle numbers (n = 10, 50, 150 and 200) and various shear directions (uni-direction and two-direction with phase difference of q = 0o, 45o and 90o). It is indicated from the experimental results that under the same cyclic shearing condition, the pore water pressure accumulation in Hue clay is at a slower rate, suggesting a higher cyclic shear resistance of Hue clay than that of Nam O sand. Liquefaction is reached easily in nominally 50% relative density specimens of Nam O sand when g ³ 0.4%, meanwhile soft specimen of Hue clay is not liquefied regardless of the cyclic shearing conditions used in this study. The threshold number of cycles for the pore water pressure generation generally decreases with g meanwhile, the threshold cumulative shear strain for such a property mostly approaches 0.1%. In addition, by using this new strain path parameter, it becomes more advantageous when evaluating the pore water pressure accumulation in Nam O sand and Hue clay subjected to undrained uni-directional and two-directional cyclic shears.

scholarly journals Pore water pressure accumulation and settlement of clays with a wide range of Atterberg’s limits subjected to multi-directional cyclic shear

2020 ◽  
Vol 42 (1) ◽  
pp. 93-104
Author(s):  
Tran Thanh Nhan ◽  
Hiroshi Matsuda
Keyword(s):  
Shear Strain ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Pressure Ratio ◽  
Kaolinite Clay ◽  
Cyclic Shear ◽  
Wide Range ◽  
Number Of Cycles ◽  
Cyclic Settlement

In this study, normally consolidated specimens on four clays with a wide range of Atterberg’s limits were tested by applying several series of undrained multi-directional cyclic shear followed by drainage. The cyclic shear tests were carried out under the shear strain amplitudes (γ = 0.05%-2.00%), number of cycles n = 200 and the phase difference θ = 90o. Then the accumulation of cyclic shear-induced pore water pressure and the post-cyclic settlement in strain (εv, %) were observed and discussed. In conclusion, it is clarified that the pore water pressure ratio (Udyn/σ’vo) increases with g and the soils with higher Atterberg’s limits show lower Udyn/σ’vo, and under the multi-directional cyclic shear strain at γ > 0.4%, Hue clay and Kaolinite clay with relatively low plasticity suffer from cyclic failure. In addition, the post-cyclic settlement has a tendency of decreasing with the Atterberg’s limits in the range of plasticity index from Ip = 25.5 to 63.8, meanwhile when Ip < 25.5, different tendencies were observed e.g., Hue clay (with lower Ip) shows a smaller settlement compared with those on Kaolin (with higher Ip). Furthermore, the threshold number of cycles (ntp) and cumulative shear strain (G*tp) for pore water pressure buildup were then clarified.

Liquefaction Triggering Response Under Wave-Induced Cyclic Loading

2009 ◽  
Author(s):  
H. Tolga Bilge ◽  
Berna Unutmaz ◽  
A. Anil Yunatci ◽  
Ipek Yunatci ◽  
K. Onder Cetin
Keyword(s):  
Cyclic Loading ◽  
Earthquake Engineering ◽  
Water Pressure ◽  
Coarse Grained ◽  
Triaxial Tests ◽  
Offshore Structure ◽  
Cyclic Shear ◽  
Saturated Sands ◽  
Number Of Cycles ◽  
Wave Induced

Cyclic response of saturated sands has become one of the most popular topics in geotechnical earthquake engineering due to the consequent damages of earthquakes. Related to this topic, detailed performance of offshore structures founded on saturated sands under the effect of cyclic loads carries vital economic importance. It is well-known that besides seismic loading; storm, wind and/or submarine slope failures have direct effect on the strength and deformation behavior of soils through induced sea-level variations. This study summarizes the results of a series of cyclic triaxial tests performed to simulate the behavior of fully-saturated coarse grained sands under wave-induced cyclic loading. Evaluating the excess pore water pressure generation and shear strain accumulation response along with the number of cycles required for liquefaction triggering for sands, having different relative densities, and being subjected to various cyclic shear stress ratios (CSR), the following observations are made; i) number of cycles to liquefaction increases with increasing relative density and decreasing CSR, ii) for medium dense foundation and backfill soils, liquefaction is not triggered for CSR values less than 0.1 under reasonable number of cycles, and iii) number of cycles to liquefaction decreases significantly for soils subjected to CSR values exceeding of 0.25. These results were used to express the effects of the variation in water level and liquefaction triggering response in terms of in-situ test data, wave height and number of waves for the granular backfill of a sample offshore structure.

EXCESS PORE WATER PRESSURE ACCUMULATION AND RECOMPRESSION OF SATURATED SOFT CLAY SUBJECTED TO UNI-DIRECTIONAL AND MULTI-DIRECTIONAL CYCLIC SIMPLE SHEARS

2013 ◽  
Vol 07 (04) ◽  
pp. 1250027 ◽  
Author(s):  
HIROSHI MATSUDA ◽  
TRAN THANH NHAN ◽  
RYOHEI ISHIKURA
Keyword(s):  
Shear Strain ◽  
Pore Water ◽  
Strain Amplitude ◽  
Phase Difference ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Shear Direction ◽  
Cyclic Shear ◽  
Number Of Cycles ◽  
Shear Strain Amplitude

This paper is to investigate the effect of cyclic shear direction (or phase difference) on the accumulation of excess pore water pressure during cyclic shear and on the recompression after cyclic shear. Several series of uni-directional and multi-directional cyclic simple shear tests under undrained condition were carried out for normally consolidated Kaolin. From the test results it is shown that the accumulation of pore water pressure and the post-cyclic settlement increase with the shear strain amplitude and the phase difference. The values of the shear strain amplitude at which the effect of cyclic shear direction is most significant, decrease with the increase of the number of cycles. The change of the void ratio in the recompression stage increases approximately in proportion to the logarithm of the stress reduction ratio and is not affected by the shear strain amplitude. For multi-directional cyclic shear, this change of the void ratio depends on the phase difference and the number of cycles. The cyclic recompression indices in the recompression stage were obtained for uni-directional and multi-directional cyclic shears. The cyclic shear induced settlement can be calculated by using these indices.

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

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.

scholarly journals Analysis of Tunnel Water Inrush Considering the Influence of Surrounding Rock Permeability Coefficient by Excavation Disturbance and Ground Stress

2021 ◽  
Vol 11 (8) ◽  
pp. 3645
Author(s):  
Helin Fu ◽  
Pengtao An ◽  
Long Chen ◽  
Guowen Cheng ◽  
Jie Li ◽  
...  
Keyword(s):  
Permeability Coefficient ◽  
Water Pressure ◽  
Water Inrush ◽  
Surrounding Rock ◽  
Water Inflow ◽  
Calculation Error ◽  
External Water Pressure ◽  
Ground Stress ◽  
External Water ◽  
Inflow Prediction

Affected by the coupling of excavation disturbance and ground stress, the heterogeneity of surrounding rock is very common. Presently, treating the permeability coefficient as a fixed value will reduce the prediction accuracy of the water inflow and the external water pressure of the structure, leading to distortion of the prediction results. Aiming at this problem, this paper calculates and analyzes tunnel water inflow when considering the heterogeneity of permeability coefficient of surrounding rock using a theoretical analysis method, and compares with field data, and verifies the rationality of the formula. The research shows that, when the influence of excavation disturbance and ground stress on the permeability coefficient of surrounding rock is ignored, the calculated value of the external water force of the tunnel structure is too small, and the durability and stability of the tunnel are reduced, which is detrimental to the safety of the structure. Considering the heterogeneity of surrounding rock, the calculation error of water inflow can be reduced from 27.3% to 13.2%, which improves the accuracy of water inflow prediction to a certain extent.

Control of arterial pressure in aquatic sea snakes

1983 ◽  
Vol 244 (1) ◽  
pp. R66-R73 ◽  
Author(s):  
H. B. Lillywhite ◽  
F. H. Pough
Keyword(s):  
Arterial Pressure ◽  
Blood Volume ◽  
Water Pressure ◽  
Cardiovascular Responses ◽  
Physiological Regulation ◽  
Sea Snakes ◽  
Head Up Tilt ◽  
External Water Pressure ◽  
External Water ◽  
Head Level

Cardiovascular responses to head-up tilt, acutely graded hemorrhage, and pharmacologic stimulation by principal autonomic drugs were studied in four species of marine snakes, principally Aipysurus laevis (family Hydrophiidae). Arterial pressure varied inversely with tilt angle and blood volume deficit in conscious snakes outside of water, indicating that physiological regulation was poor or lacking. Calculated arterial pressures at head level typically diminished to zero in A. laevis tilted to angles greater than or equal to 30 degrees. Arterial pressure (corrected for external water pressure) did not change when these snakes were tilted in seawater. Changes of arterial pressure induced by tilt, blood loss, or autonomic drugs elicited reflex adjustments in heart activity, but the magnitude of these responses was less than that observed in terrestrial species of snake. It is concluded that baroreflexes are present but comparatively ineffective in sea snakes. Snakes tolerated large losses of blood volume, and extravascular fluids were absorbed into the circulation during hemorrhage; both hemorrhage and estimated hemodilution volumes exceeded 100% of the initial blood volume in Acalyptophis peronii. Thus, in marine snakes major fluid shifts between nonvascular and vascular compartments significantly compensate hypovolemia but, because of minor autonomic adjustments, do not result in a well-regulated arterial pressure.

scholarly journals A multicentered comparison of measurements obtained with microtip and external water pressure transducers

2005 ◽  
Vol 17 (4) ◽  
pp. 400-406 ◽  
Author(s):  
Andrew F. Hundley ◽  
Morton B. Brown ◽  
Linda Brubaker ◽  
Geoffrey W. Cundiff ◽  
Karl Kreder ◽  
...  
Keyword(s):  
Water Pressure ◽  
Pressure Transducers ◽  
External Water Pressure ◽  
External Water

Stress–strain pattern–based criterion to assess cyclic shear resistance of soil from laboratory element tests

2016 ◽  
Vol 53 (9) ◽  
pp. 1460-1473 ◽  
Author(s):  
Dharma Wijewickreme ◽  
Achala Soysa
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Shear Stiffness ◽  
Large Strains ◽  
Fundamental Parameter ◽  
Stress Strain ◽  
Cyclic Shear ◽  
Excess Pore Water Pressure ◽  
Excess Pore

The cyclic shear response of soils is commonly examined using undrained (or constant-volume) laboratory element tests conducted using triaxial and direct simple shear (DSS) devices. The cyclic resistance ratio (CRR) from these tests is expressed in terms of the number of cycles of loading to reach unacceptable performance that is defined in terms of the attainment of a certain excess pore-water pressure and (or) strain level. While strain accumulation is generally commensurate with excess pore-water pressure, the definition of unacceptable performance in laboratory tests based purely on cyclic strain criteria is not robust. The shear stiffness is a more fundamental parameter in describing engineering performance than the excess pore-water pressure alone or shear strain alone; so far, no criterion has considered shear stiffness to determine CRR. Data from cyclic DSS tests indicate consistent differences inherent in the patterns between the stress–strain loops at initial and later stages of cyclic loading; instead of relatively “smooth” stress–strain loops in the initial parts of loading, nonsmooth changes in incremental stiffness showing “kinks” are notable in the stress–strain loops at large strains. The point of pattern change in a stress–strain loop provides a meaningful basis to determine the CRR (based on unacceptable performance) in cyclic shear tests.

scholarly journals Instruments and Methods High Pressure Coupling for Pipe in Deep Water Filled Bore Holes

1963 ◽  
Vol 4 (36) ◽  
pp. 809-812
Author(s):  
R. L. Shreve
Keyword(s):  
High Pressure ◽  
Water Pressure ◽  
The Other ◽  
Internal Diameter ◽  
External Diameter ◽  
Synthetic Rubber ◽  
External Water Pressure ◽  
External Water ◽  
One Year ◽  
Aluminum Pipe

AbstractIn August 1961 an aluminum pipe (3.5 cm. internal diameter, 4.2 cm. external diameter) having 92 specially modified socket couplings (5.0 cm. external diameter) sealed with a quick-polymerizing synthetic rubber was sunk 226 m. in a vertical water-filled bore hole in Blue Glacier, Washington. U.S.A. The geometry of threads and mating surfaces of pipe and coupling was designed to cause increasing external water pressure to tighten the seal. One joint at a depth of 66 m. immediately developed an extremely slow leak (probably because of faulty cleaning), but the other 91 joints apparently were sound, as the pipe was free of water to a depth of at least 157 m. when resurveyed after one year.

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