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1
Costantini, A., HB So, and D. Doley. "Early Pinus caribaea var. hondurensis root development. 1. Influence of matric suction." Australian Journal of Experimental Agriculture 36, no. 7 (1996): 839. http://dx.doi.org/10.1071/ea9960839.
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This paper reports 2 experiments that examine the influence of matric suction on radicle elongation in Pinus caribaea var. hondurensis. Experiment 1 where mechanical impedance of root development was negligible and aeration was not limiting, and experiment 2 in low strength soils where both air-filled porosity and moisture were allowed to vary. In experiment 1, radicles were grown between sheets of Whatman No. 42 filter paper. The known wetting characteristic of this paper was used to prepare known pretrial suctions and define postharvest suctions. The midpoint of the pretrial-postharvest suction range was defined as nominal matric suction. Relationships between radicle elongation and nominal matric suction were developed for 6 P. caribaea var. hondurensis families. As matric suction increased from 0.0065 to 3.13 MPa, radicle elongation after 48 h of growth decreased monotonically to zero. Over the range of matric suctions, there was no critical level, below which radicle elongation was unaffected by increasing suction. It was concluded that radicles were able to sense, and respond to, increasing suction. Significant family x matric suction interactions were observed. In experiment 2, radicles were grown in 2 lowstrength repacked soils. An optimal level of matric suction for radicle elongation was observed in both soils. At suctions below and above the optima, inadequate air-filled porosity and moisture stress respectively adversely impacted upon elongation. The 2 experiments demonstrated that matric suction affects radicle elongation both directly and indirectly through interaction with other physical soil properties. Although increasing suction reduces radicle elongation, there may be a 'non-limiting' range of suctions in soil media over which radical elongation is relatively unaffected due to a concomitant improvement in aeration.
2
HAO, X., and E. DE JONG. "EFFECT OF MATRIC AND OSMOTIC SUCTION ON THE EMERGENCE OF WHEAT AND BARLEY." Canadian Journal of Plant Science 68, no. 1 (January 1, 1988): 207–9. http://dx.doi.org/10.4141/cjps88-021.
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Total emergence of wheat and barley was not affected my matric and osmotic suctions up to 0.5 and 0.9 MPa, respectively. Above 1.5 MPa matric suction, seeds germinated but did not emerge. Emergence rate decreased with increasing matric and osmotic suctions, except at high suctions where the reverse was observed.Key words: Emergence, osmotic suction, matric suction, wheat, barley
3
Manosuthkij, Thammanoon, Anand J. Puppala, Soheil Nazarian, Sireesh Saride, and Laureano Hoyos. "Comparisons between Field and Laboratory Suction Measurements of Expansive Clays." Transportation Research Record: Journal of the Transportation Research Board 2053, no. 1 (January 2008): 39–46. http://dx.doi.org/10.3141/2053-06.
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Field suction measurements are especially important for pavements constructed on unsaturated expansive soils. Because these subgrade soils can experience high suction during dry seasons, field sensors that can measure high soil suctions are necessary. In this research, thermal conductivity-based soil suction sensors were evaluated for matric suction measurements at several sites. Laboratory suction measurements with the filter paper method were compared with the field suction measurements with the sensors. Soil water characteristic curves derived from the laboratory and field measurements agreed closely. Volume change measurements using swell and shrinkage tests were conducted separately on the subgrade soils retrieved from the instrumented test sites. The laboratory and field suction data need an adjustment or shift of the time factor to obtain comparable values at high suctions. The influence of total suction on the volumetric swell and shrinkage characteristics of the field subsoils were also addressed.
4
Nguyen, Quan, Delwyn G. Fredlund, Lal Samarasekera, and Brent L. Marjerison. "Seasonal pattern of matric suctions in highway subgrades." Canadian Geotechnical Journal 47, no. 3 (March 2010): 267–80. http://dx.doi.org/10.1139/t09-099.
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The performance of “thin membrane surface” (TMS) highways is largely controlled by the strength of the subgrade soil, which in turn is a function of matric suction. Thermal conductivity matric suction sensors were used to indirectly measure in situ matric suctions. In September 2000, 32 thermal conductivity sensors were installed under TMS highways at two locations; namely, Bethune and Torquay, Saskatchewan, Canada, to monitor matric suction and temperature changes with time. This paper presents and interprets the variations in matric suctions measured between the years 2000 and 2005 at the Torquay site. The readings in the field showed a clearly seasonal pattern of matric suction changes that bore a relationship to rainfall near the test sites. Relatively constant equilibrium matric suctions that ranged from 20 to 60 kPa throughout the years were measured under the driving lanes. Conversely, matric suctions under the side slopes were found to vary widely with time and depth, ranging from 100 to 1500 kPa over the years. The greatest variation in matric suction from one location to another location occurred during the month of April. The matric suctions showed low variability during June, whereas larger variations were observed from July to October.
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Ng, Charles Wang Wai, Hamed Sadeghi, and Fardin Jafarzadeh. "Compression and shear strength characteristics of compacted loess at high suctions." Canadian Geotechnical Journal 54, no. 5 (May 2017): 690–99. http://dx.doi.org/10.1139/cgj-2016-0347.
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Compression and shear behavior of a loosely compacted loess is investigated via two series of saturated and unsaturated direct shear tests. The vapor transfer mechanism is used to modify a shear box device for control of suction at high range. In spite of significant volumetric strain upon wetting (up to 14%), suction-induced volumetric shrinkage is less than 2% for all suction levels considered because of the as-compacted moisture content at the dry side of the optimum value. During shearing, all unsaturated tests dried to high suctions indicate a strain-softening mode of failure associated with noticeable dilation. There is a continuous increase in peak strength with suction but at a reduced rate, which cannot be captured by the improved Bishop’s effective stress model, as it underestimates the contribution of high suctions by approaching zero degree of saturation. Unsaturated tests at high suctions also show an increased rate of dilation with suction for both values of net stress, which cannot be predicted well by the classical stress–dilatancy models. It is shown that for suction values beyond 8 MPa, dilation angle increases by 2° and 6° per 100 MPa increase of suction under net stress of 50 and 200 kPa, respectively.
6
Meilani, Inge, Harianto Rahardjo, Eng-Choon Leong, and Delwyn G. Fredlund. "Mini suction probe for matric suction measurements." Canadian Geotechnical Journal 39, no. 6 (December 1, 2002): 1427–32. http://dx.doi.org/10.1139/t02-101.
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A modified triaxial apparatus with mini suction probes was fabricated to study the matric suction along the specimen height during unsaturated triaxial testing. Three mini suction probes were placed at 3/4, 1/2, and 1/4 height of the specimen, each at 120° apart in the lateral direction. This paper presents the development of the mini probe for matric suction measurements. Evaluation of the performance shows that the fabricated mini probe provides a rapid response and accurate reading under negative and positive pore-water pressure changes. Matric suctions as high as 400 kPa were successfully measured on soil specimens over a time span of 15 h. On the other hand, the mini suction probes were also found to be able to measure a matric suction of 200 kPa for a longer period of 155 h.Key words: matric suction, mini suction probe, triaxial, unsaturated soils, mid-height pore-water pressure measurement.
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Fredlund, Delwyn G., Daichao Sheng, and Jidong Zhao. "Estimation of soil suction from the soil-water characteristic curve." Canadian Geotechnical Journal 48, no. 2 (February 2011): 186–98. http://dx.doi.org/10.1139/t10-060.
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Soil-water characteristic curves (SWCCs) are routinely used for the estimation of unsaturated soil property functions (e.g., permeability functions, water storage functions, shear strength functions, and thermal property functions). This paper examines the possibility of using the SWCC for the estimation of in situ soil suction. The paper focuses on the limitations of estimating soil suctions from the SWCC and also suggests a context under which soil suction estimations should be used. The potential range of estimated suction values is known to be large because of hysteresis between drying and wetting SWCCs. For this, and other reasons, the estimation of in situ suctions from the SWCC has been discouraged. However, a framework is suggested in this paper for estimating the median value for in situ soil suction along with a likely range of soil suction values (i.e., maximum and minimum values). The percentage error in the estimation of soil suction from the SWCC is shown to be lowest for sand soils and highest for clay soils.
8
Tripathy, Snehasis, Mohd Yuhyi M. Tadza, and Hywel Rhys Thomas. "Soil-water characteristic curves of clays." Canadian Geotechnical Journal 51, no. 8 (August 2014): 869–83. http://dx.doi.org/10.1139/cgj-2013-0089.
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The drying suction – water content soil-water characteristic curves (SWCCs) of three clays (MX80 bentonite, yellow bentonite, and Speswhite kaolin) were experimentally determined using axis-translation, vapour equilibrium, and osmotic techniques. The shrinkage paths of the clays were established from Clod tests. The suction – water content SWCCs in conjunction with the Clod test results enabled establishing the suction – degree of saturation SWCCs and further determination of the air-entry values (AEVs) of the clays. Chemical analyses of the polyethylene glycol (PEG) solutions in the osmotic tests revealed an imbalance of the osmotic suctions between the expelled and the retained salts on either side of semi-permeable membranes. A decrease in the water content due to an applied suction for clays with significant osmotic efficiencies was explained by two mechanisms. In mechanism 1, the water content decrease prior to the air entry is controlled by the interparticle repulsive pressure, and in mechanism 2, a decrease in the degree of saturation following the air entry is primarily due to the matric suction. The agreements between the AEVs of the clays determined based on the osmotic suctions corresponding to various applied suctions and that determined from the suction – degree of saturation SWCCs were found to be very good.
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Zhang, Hongxin, Shaowen Chen, Yun Gong, and Songtao Wang. "Flow control using unsteady pulsed holed suction with different excitation models in a highly loaded compressor cascade." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 232, no. 6 (November 13, 2017): 593–607. http://dx.doi.org/10.1177/0957650917740769.
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Unsteady pulsed holed suction as a new unsteady flow control technique is first proposed. Unsteady excitation models of four different waveforms (Waveforms 1, 2, 3, and 4) based on unsteady pulsed holed suction are investigated to analysis comparatively the control effects of flow separations in a certain highly loaded compressor. Some related unsteady aerodynamic parameters such as excitation frequency and excitation location are studies. The unsteady pulsed holed suctions of the four different modes (Waveforms 1, 2, 3, and 4) all effectively control flow separations. Their optimum frequencies are all an integer multiple of the natural frequency of vortex shedding. And their excitation locations gaining positive effect and optimal excitation locations are both same. The optimal excitation location is near the separation point of upper endwall in unexcited case. But, they show markedly different performances in reducing the total pressure losses. The unsteady pulsed holed suction of Waveform 3 shows greater advantage at different excitation frequencies and excitation locations. The optimum result is obtained by the unsteady pulsed holed suction of Waveform 3. The total pressure loss is reduced by 16.8%. Simultaneously, the unsteady pulsed holed suctions of the four different modes all can provide better effects than the steady constant holed suction in reducing the total pressure loss with the same suction-to-inlet time-averaged suction flow ratio ms. Especially at ms = 0.29%, for the steady constant holed suction, it is too small to effectively control flow separation, and consequently the total pressure loss are increased by 8.3%. However, for the unsteady pulsed holed suctions of Waveforms 2 and 3, the total pressure losses are reduced by 9.1% and 4.3%, respectively.
10
Wang, A., and H. Lai. "Control of separated flow at low Reynolds number around NACA0012 airfoil by boundary layer suction." Journal of Physics: Conference Series 2707, no. 1 (February 1, 2024): 012122. http://dx.doi.org/10.1088/1742-6596/2707/1/012122.
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Abstract The separated flow at low Reynolds number around the NACA0012 airfoil is numerically studied by large-eddy simulation. Strategies of boundary layer suction to control flow separation are investigated. A method of using two-zone suctions, near the leading edge and near the trailing edge, are calculated. Based on verification with direct numerical simulation (DNS) and experimental data, the results of the lift and the drag, the vortices, and the strength of near-field pressure fluctuations, are checked. The results show that the two-zone suctions can supress flow transition and separation, thereby increase the lift and reduce the drag. The shedding of vortices is weakened, and the near-field pressure fluctuations are attenuated. For comparison with the two-zone suctions, the strategies of suction near the leading edge only and suction near the trailing edge only are also studied. It is found that suction near the leading edge only may suppress transition and delay separation when the suction zone is large enough, but the flow property deteriorates due to shedding vortices in the wake. The suction near the trailing edge only may improve the flow performance by reducing the size of the vortices in the rear section of the airfoil and in the wake region, but it has little effect on the separation bubble and transition.
11
Fredlund, Delwyn G., Julian K.-M. Gan, Yun Guan, and Neil Richardson. "Suction Measurements on a Saskatchewan Soil Using a Direct-Measurement, High-Range Suction Sensor." Transportation Research Record: Journal of the Transportation Research Board 1596, no. 1 (January 1997): 84–92. http://dx.doi.org/10.3141/1596-13.
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A tensiometric-type suction sensor capable of direct measurement of matric suctions greater than 100 kPa has recently been developed. The sensor has been used to measure matric suctions up to 1250 kPa. The sensor makes use of the tensile strength of water for the measurement of matric suction. The cavitation of water in conventional tensiometers occurs at a negative pressure approaching 1 atmosphere because of the presence of cavitation nuclei. In the absence of cavitation nuclei, the tensile strength of water can be on the order of several atmospheres. The direct-measurement, high-range suction sensor has been used for the measurement of matric suction on borehole samples obtained during a soils investigation at a bridge site near the town of Outlook, Saskatchewan, Canada. The method has proven to be fast and simple to use. Matric suction measurements of the samples from the Outlook bridge site are presented, along with an interpretation of the laboratory data.
12
Harshbarger, SA, LA Hoffman, TG Zullo, and MR Pinsky. "Effects of a closed tracheal suction system on ventilatory and cardiovascular parameters." American Journal of Critical Care 1, no. 3 (November 1, 1992): 57–61. http://dx.doi.org/10.4037/ajcc1992.1.3.57.
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OBJECTIVE: To determine whether patients ventilated in the assist-control mode experienced a change in oxygenation, respiratory rate, inspiratory:expiratory ratio, heart rate, blood pressure or acid-base balance when suctioned with a closed tracheal suction system. DESIGN: A quasi-experimental, within-subject, repeated-measures design was used. SUBJECTS: 18 patients ventilated on a fraction of inspired oxygen of 0.47 +/- 0.17 and 2.3 +/- 5.0 cm H2O positive end-expiratory pressure. INTERVENTIONS: Two suction passes were performed, with measurements at baseline, immediately after the first suction pass, immediately before the second suction pass, immediately after the second suction pass, 2 minutes after the second suction pass and 5 minutes after the second suction pass. No hyperoxygenation was used. RESULTS: Significant differences were seen over time for arterial oxygen saturation, respiratory rate and inspiratory:expiratory ratio. Arterial oxygen saturation decreased to less than 90% in four subjects (range 88% to 89%), with a maximum fall of 9%. No significant differences were seen for heart rate, blood pressure, partial pressure of carbon dioxide, bicarbonate, time to nadir (lowest arterial oxygen saturation) or recovery time. CONCLUSIONS: Subjects ventilated in the assist-control mode and suctioned with a closed tracheal suction system did not experience significant changes in cardiovascular or acid-base parameters when suctioned without hyperoxygenation. Although most subjects did not become desaturated, four subjects experienced desaturation at one or more intervals. To prevent desaturation, hyperoxygenation should be used before and after suctioning with a closed tracheal suction system.
13
Yang, Shu-Rong, Wei-Hsing Huang, and Yu-Tsung Tai. "Variation of Resilient Modulus with Soil Suction for Compacted Subgrade Soils." Transportation Research Record: Journal of the Transportation Research Board 1913, no. 1 (January 2005): 99–106. http://dx.doi.org/10.1177/0361198105191300110.
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The variations of resilient modulus with the postconstruction moisture content and soil suction for cohesive subgrade soils were evaluated. In particular, the effects of relative compaction of the subgrade on the suction and resilient modulus were investigated. To simulate subgrade soils at in-service conditions, soil specimens were compacted at various relative compactions and optimum moisture content and then saturated to equilibrium moisture content to test for resilient modulus and soil suction. The filter paper method was used to measure the total and matric suctions of two cohesive soils. Test findings demonstrated that resilient modulus correlated better with the matric suction than with total suction. Matric suction was found to be a key parameter for predicting the resilient modulus of cohesive subgrade soils. A prediction model incorporating deviator stress and matric suction for subgrade soil resilient modulus was established.
14
Dreschel, Thomas W., and John C. Sager. "Control of Water and Nutrients Using a Porous Tube: A Method for Growing Plants in Space." HortScience 24, no. 6 (December 1989): 944–47. http://dx.doi.org/10.21273/hortsci.24.6.944.
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Abstract A plant nutrient delivery system that uses a microporous, hydrophilic tube was developed with potential application for crop production in the microgravity of space. The tube contains a nutrient solution and delivers it to the roots. Pumps attached to the tubing create a very small suction that holds the solution within the tube. This system was used to grow wheat (Triticum aestivum cv. Yecora Rojo) for 107 days in a controlled environment at suctions of 0.40, 1.48, or 2.58 kPa. The water absorbed through the pores of the tube by baby diaper sections decreased as suction increased. Correspondingly, final plant biomass, seed number, and spikelet number also tended to decrease as suction increased. The reduced yield at higher suction suggests that the plants experienced water stress, although all suctions were below those typical of soils at field capacity.
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Yang, Hongwei, and Adrian R. Russell. "Cone penetration tests in unsaturated silty sands." Canadian Geotechnical Journal 53, no. 3 (March 2016): 431–44. http://dx.doi.org/10.1139/cgj-2015-0142.
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Very little is known about how to interpret cone penetration tests (CPTs) when performed in unsaturated soils. The few published studies on CPTs in unsaturated soils have focused on either clean sands or silt. In this study, new results of laboratory-controlled CPTs in an unsaturated silty sand are presented. Silty sand exhibits hydraulic hysteresis and suction hardening. Suction is observed to have a pronounced effect on measured cone penetration resistance. For an isotropic net confining stress of 60 kPa, it is observed that higher suctions give rise to cone penetration resistances that are 50% larger than those for lower suctions. A semi-theoretical correlation is presented that links measured cone penetration resistances to initial relative density and mean effective stress. Suction has an influence on cone penetration resistances through suction hardening, as well as its contribution to effective stress. For this silty sand, it is shown that failing to account for suction may result in significant overestimations and unsafe predictions of soil properties from measured cone penetration resistances.
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Zhang, Junran, De’an Sun, Annan Zhou, and Tong Jiang. "Hydromechanical behaviour of expansive soils with different suctions and suction histories." Canadian Geotechnical Journal 53, no. 1 (January 2016): 1–13. http://dx.doi.org/10.1139/cgj-2014-0366.
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This paper presents a number of experimental results of suction-controlled triaxial tests on a compacted weakly expansive soil with different suctions and suction histories. In terms of suction control methods, the high suction level (from 3.29 to 38 MPa) was realized by the vapor equilibrium technique and the low suction level (from 0 to 800 kPa) was controlled by the axis translation technique. Results of the triaxial tests indicate that the specimen with higher suction shows higher strength and lower contractive and higher dilative volumetric strains, and the average skeleton stress ratio (q/p′) at failure decreases with increasing suction in the high suction range (3.29∼38 MPa). Given that suction during shearing is constant (e.g., 200 kPa), the specimen dried to a higher suction and the history shows higher strength and lower contractive volumetric strain. Experimental results also show that high pre-applied suction (i.e., the maximum suction in the history) can lead to peak strength, post-peak softening, and shear dilation. Three different methods (pressure plate, filter paper, and vapor equilibrium) were employed to study the soil-water retention behaviour of the unsaturated expansive soil. Test results indicate that by combining these three different methods, it is possible to determine the SWCC in the entire suction range (0∼367 MPa). Test results of the expansive soil also show that the void ratio keeps decreasing with increasing suction in the entire suction range.
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Wang, Hao, Yu-Jun Cui, Minh-Ngoc Vu, and Jean Talandier. "Investigation into the compression behaviour of unsaturated damaged Callovo-Oxfordian claystone." E3S Web of Conferences 382 (2023): 25008. http://dx.doi.org/10.1051/e3sconf/202338225008.
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In this study, the compression behaviour of unsaturated damaged COx claystone is investigated by performing high pressure oedometer tests with controlled suction. The damaged oedometer samples were prepared by shearing the claystone in triaxial conditions. Four high pressure oedometer tests were conducted using different controlled suctions. The effects of suction and damage on the swelling and compression were investigated in oedometer. Results show that the intact claystone exhibits a larger swelling strain than that of the damaged one at the same imposed suction. The damaged claystone at a lower suction displays a smaller yield stress and higher compressibility, and exhibits a larger compression index Cc than the intact one, evidencing the effect of damage. In addition, the step compression index Cc* increases with the increase of vertical stress, while deceases with the decrease of suction. This indicates the dependencies of compression behaviour on vertical stress and suction.
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Singhal, Sonal, Sandra L. Houston, and William N. Houston. "Swell pressure, matric suction, and matric suction equivalent for undisturbed expansive clays." Canadian Geotechnical Journal 52, no. 3 (March 2015): 356–66. http://dx.doi.org/10.1139/cgj-2014-0159.
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Methods of computation for soil heave based on an “equivalent” net normal stress path approach often have built-in assumptions regarding the relationship between in situ matric suction, overburden stress, and swell pressure. The term “matric suction equivalent” has been previously defined as the difference between in situ state of stress projected on the net normal stress plane (represented by swell pressure) and overburden stress. Correlations between matric suction, overburden stress, and swell pressure for matric suction values in excess of the air-entry value have not been well studied and are explored here for expansive soils. Filter paper (in-contact) and constant volume swell pressure tests were performed on undisturbed tube samples of expansive soils taken from Arizona, Colorado, and Texas. In general, the ratio of the matric suction equivalent to the matric suction decreases with increasing soil suction. An empirical relationship was established in which the matric suction equivalent was found to be proportional to the logarithm of the matric suction for in situ matric suctions greater than a certain value, termed as the “intercept matric suction”. A correlation between the intercept matric suction and the soil’s plasticity index (PI) was found for the clays of this study. The developed correlations represent a method for obtaining approximate estimates of in situ matric suction for expansive soils from PI and swell pressure data. Implications of the study findings for the use of an equivalent net normal stress approach for estimation of soil heave are explored.
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Zhang, Min, Shidong Fan, Hanhua Zhua, and Sen Han. "Numerical Simulation of Solid-Fluid 2-Phase-Flow of Cutting System for Cutter Suction Dredgers." Polish Maritime Research 25, s2 (August 1, 2018): 117–24. http://dx.doi.org/10.2478/pomr-2018-0082.
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Abstract The study of the flow characteristics of the solid-fluid two phase flow in the cutter suction dredger is very important for exploring the slurry formation mechanism and optimizing the operational parameters. In this study, standard k-ε model and Multiple Reference Frame are applied to numerically simulate flow field in and around the cutting system, then with the steady convergent result of the simulation as the initial condition, Discrete Phase Mode is used to solve the particle motion equation by fully coupling the continuous phase and the particles. The influence of suction flow velocity and cutter’s rotating speed on particles suction are analyzed, and effectively suctioned particles numbers are also quantitatively studied. The simulation result shows that the DPM model is able to simulate the movement of particles in and around the cutter suction dredger’s cutting system, in the fluid flow filed velocity vector and pressure distribution on different planes show different characteristics, and under higher suction velocity and lower cutter rotating speed more particles are suctioned into the suction inlet. The results can help better understand flow characteristics of solid-fluid 2-phase-flow of cutter suction dredger’s cutting system, and provide theoretical support for relative system design and operational parameters optimization.
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Hossain, Md Akhtar, and Jian-Hua Yin. "Shear strength and dilative characteristics of an unsaturated compacted completely decomposed granite soil." Canadian Geotechnical Journal 47, no. 10 (October 2010): 1112–26. http://dx.doi.org/10.1139/t10-015.
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Shear strength and dilative characteristics of a re-compacted completely decomposed granite (CDG) soil are studied by performing a series of single-stage consolidated drained direct shear tests under different matric suctions and net normal stresses. The axis-translation technique is applied to control the pore-water and pore-air pressures. A soil-water retention curve (SWRC) is obtained for the CDG soil from the equilibrium water content corresponding to each applied matric suction value for zero net normal stress using a modified direct shear apparatus. Shear strength increases with matric suction and net normal stress, and the failure envelope is observed to be linear. The apparent angle of internal friction and cohesion intercept increase with matric suction. A greater dilation angle is found at higher suctions with lower net normal stresses, while lower or zero dilation angles are observed under higher net normal stresses with lower suctions, also at a saturated condition. Experimental shear strength data are compared with the analytical shear strength results obtained from a previously modified model considering the SWRC, effective shear strength parameters, and analytical dilation angles. The experimental shear strength data are slightly higher than the analytical results under higher net normal stresses in a higher suction range.
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Ebrahimisadr, Hesam, and Bertrand Francois. "Water retention curves and tensile strength for studying desiccation cracking of compacted clay soils." E3S Web of Conferences 382 (2023): 09003. http://dx.doi.org/10.1051/e3sconf/202338209003.
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Desiccation cracking is a natural phenomenon caused by drying in near-surface earth soils subjected to constrained shrinkage. In this research, the water retention curve of two clayey soils, prepared by compaction under standard proctor conditions, are determined to study the desiccation cracking. Two techniques of suction control are applied to control the drying process and to reach the water retention curve of the soils. For the suction values higher than 4 MPa, the saline-solution method was used to impose variousrelative humidity and so, various suctions. In addition, the osmotic method was applied for the suction values between 0.5 MPa and 2 MPa. Additionally, the dynamic vapor sorption (DVS) technique is used to corroborate the water retention curves obtained with the two other techniques. The volume changes is also tracked showing significant shrinkage upon drying. To reach the tensile strength of the soil, the Braziliantest is performed on samples prepared by compaction and submitted to various suctions. According to the results, for the two tested soils, the soil with the higher plasticity index shows consistently the higher retention capacity and the larger shrinkage upon drying. Also, the obtained water retention curves exhibit a smooth transition when the suction control technique change (at suctions between 2 and 4 MPa).
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Thu, Trinh Minh, Harianto Rahardjo, and Eng-Choon Leong. "Soil-water characteristic curve and consolidation behavior for a compacted silt." Canadian Geotechnical Journal 44, no. 3 (March 1, 2007): 266–75. http://dx.doi.org/10.1139/t06-114.
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Measurement of the soil-water characteristic curve (SWCC) in the laboratory is commonly conducted under zero confining pressure. However, in the field, the soil is under a confining stress. Therefore, it is important to study the effects of the confining stress on SWCC. In addition, the consolidation curve is normally generated under saturated conditions. However, the soil above the water table is usually unsaturated. Hence, it is also necessary to investigate the effects of matric suction on the characteristics of the consolidation curves. This paper presents the SWCCs under different net confining stresses and the isotropic consolidation curves under different matric suctions that describe the volume change characteristics of unsaturated soils with respect to stress state variables, net normal stress, and matric suction. A series of SWCCs was determined for statically compacted silt specimens in a triaxial cell apparatus under different net confining stresses. Isotropic consolidation tests under different matric suctions were also carried out. The results of the SWCC tests show that the air-entry value increased with increasing net confining stress. The yield points (i.e., yield suction, s0) obtained from the SWCC tests also increased with increasing net confining stress. The results of isotropic consolidation tests indicate the strong influence of matric suction on compressibility and stiffness of the compacted silt specimens.Key words: soil-water characteristic curve, isotropic consolidation, pore-water pressure, volume change, NTU mini suction probe, matric suction.
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Azizi, Arash, Ashutosh Kumar, Mwajuma Ibrahim Lingwanda, and David Geoffrey Toll. "The influence of rates of drying and wetting on measurements of soil water retention curves." E3S Web of Conferences 195 (2020): 03005. http://dx.doi.org/10.1051/e3sconf/202019503005.
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The water retention curve is fundamental for a comprehensive description of the hydro-mechanical behaviour of unsaturated soils. The water retention testing system developed at Durham University allows direct and continuous measurement of suction using a high capacity tensiometer, water content determined from mass readings of a digital balance and measurements of volume change. The system was modified to accommodate an additional tensiometer to measure suction at the top besides the existing one at the bottom of the soil specimen. Soil specimens were subjected to drying and wetting following two procedures: discrete measurements carried out in stages to ensure equalisation and continuous measurement at different rates. All suctions measured during continuous and discrete measurements were very close at high saturation degrees. At lower saturation degrees, the suction values from the top and bottom of the specimen deviated from suctions observed in discrete measurements. This deviation in suction values was more evident in accelerated drying and wetting patterns. This can be explained by the fact that water permeability reduces with the decrease in saturation levels.
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Estabragh, A. R., and A. A. Javadi. "Critical state for overconsolidated unsaturated silty soil." Canadian Geotechnical Journal 45, no. 3 (March 2008): 408–20. http://dx.doi.org/10.1139/t07-105.
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The critical state concepts have been investigated for an overconsolidated unsaturated silty soil through a comprehensive set of controlled suction triaxial laboratory experiments. The experimental tests were conducted in a specially designed double-walled Bishop and Wesley triaxial cell on samples of unsaturated silty soil. Isotropic loading, unloading, and triaxial drained shear tests were performed on samples of unsaturated silty soil with different overconsolidation ratios at various suctions. The data from the triaxial tests were used in the development of a critical state framework for overconsolidated unsaturated silty soil. The framework is defined in terms of four state variables: mean net stress (p'), deviator stress (q), suction (s), and specific volume (v). The results show that the critical state lines in q:p' space for different soil suctions are not parallel and merge with each other. The slopes and intercepts of these lines are functions of suction. However, the critical state lines are nearly parallel in the v – ln p' plane except under saturation conditions, and the slope and intercept of these lines are also functions of suction.
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Arensdorf, Jared, Halle Petitt, and David Holt. "Improving hemolysis levels associated with cardiotomy suction." Perfusion 33, no. 8 (May 23, 2018): 612–17. http://dx.doi.org/10.1177/0267659118772456.
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Background: The major source of hemolysis during cardiopulmonary bypass (CPB) remains the cardiotomy suction.1 Previous research has shown that the combination of negative pressures and the massive air-blood interface exponentially increases hemolysis in suctioned blood. Objective: This research aims to decrease hemolysis by eliminating the air-to-blood interface by implementing the Venturi effect to create powerful suction. This research effort hypothesizes that the Venturi suction will result in less hemolysis, indicated by lower plasma free hemoglobin levels (PFH) compared to current vacuum suction. Method: The research hypothesizes that a paradigm approach to cardiotomy suction that utilizes the Venturi effect with shorter tubing lengths and weighted sucker tips will further reduce hemolysis. Results: The vacuum-suctioned blood showed PFH levels significantly increased from baseline levels (p=0.0039). Neither the Venturi nor paradigm groups showed PFH levels significantly increased from baseline levels (p=0.0625 and p=0.125, respectively). There was a significant difference in PFH levels among the three conditions (p<0.0001). The vacuum condition showed significantly higher levels of PFH compared to both the Venturi and the paradigm conditions (p<0.001 for both). There was no significant difference in the PFH levels between the Venturi and the paradigm groups (p=1.00). Conclusion: This study concludes that vacuum suction causes excessive hemolysis. A Venturi-powered suction system does not cause hemolysis and can be employed to reduce the damaging effects of vacuum suction on blood.
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Yang, Jin-Wen, Yu-Jun Cui, and Nadia Mokni. "Investigation of water-retention and uniaxial compression behaviour of MX80 bentonite pellet at various suctions." E3S Web of Conferences 382 (2023): 19004. http://dx.doi.org/10.1051/e3sconf/202338219004.
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MX80 bentonite pellet/powder mixture has been regarded as a candidate sealing material in deep geological high-level radioactive waste disposal. As single pellet plays an important role in the global hydromechanical behaviour of the mixture, a series of single pellet compression tests were conducted on cylindershape MX80 bentonite 32-mm pellet after reaching suction equilibrium. The changes in volume and water content during the suction equilibration with the vapour equilibrium technique allowed the water-retention properties to be investigated. X-ray μCT observations were also made on pellets after reaching the target suctions. Results showed that upon drying the water content, void ratio and volumetric strain decreased slightly, but increased significantly upon wetting. Moreover, upon drying the network of cracks presented insignificant change and the cracks were mainly located in the marginal areas of pellet, while on wetting, cracks substantially propagated from the marginal areas to the core of pellet. The uniaxial compression tests on single pellets showed that the axial strain εaxial contributed to the contractancy, while the lateral strain εlateral to the dilatancy. The uniaxial shear strength σa, max, the crack closure (CC) stress σcc, the crack initiation (CI) stress σci, the crack damage (CD) stress σcd and the Young’s modulus E were found to decrease with suction decreasing, evidencing the suction effect through softening and cracking. Because of the combined effect of suction and wetting-induced cracks, the Poisson’s ratios v increased until the suction decreased to 38-25 MPa, and then decreased with further suction decrease. Uniaxial loading closed the horizontal wetting-induced cracks at suctions ≤ 9 MPa, leading to a drop of εlateral before CC.
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Cuisinier, Olivier, and Farimah Masrouri. "Influence de sollicitations hydriques et mécaniques complexes sur le comportement d'un sol gonflant compacté." Canadian Geotechnical Journal 42, no. 3 (June 1, 2005): 731–41. http://dx.doi.org/10.1139/t05-007.
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The main objective of the paper is to present a study on compacted expansive soil strains generated by complex hydric or mechanical loadings and their consequences on tested soil compressibility. In the first part of the paper, the suction-controlled testing devices are described (osmotic and salt solution methods). All the presented tests were performed in the range of suctions between 0 and 40 MPa. The consequences of the strains induced by wetting as a function of the applied mechanical stress were analyzed. The results showed that, under these conditions, strain depends on the followed hydraulic path, whereas the slope of the plastic compression line λ(s) was only affected by the suction applied during the mechanical loading. The second test series demonstrated that the stress path influenced both deformation and slope λ(s) if suction higher than the initial sample suction was imposed during the test. As a conclusion, it could be stated that the slope λ(s) depends on the suction applied during a mechanical loading and on the maximum suction experienced by an expansive material during its past "history".Key words: compacted soil, suction, hydric cycle, hydromechanical behaviour, expansive soil.
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Friedrich, Martin G., Ioannes Bougioukas, Peter Wenig, Steffen Vormfelde, and Theodor Tirilomis. "New device for intraoperative blood suction avoiding turbulences." BMJ Innovations 4, no. 2 (February 1, 2018): 91–97. http://dx.doi.org/10.1136/bmjinnov-2017-000201.
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IntroductionBleeding during surgery is common. Increased bleeding may disturb procedure, induces haemodynamic instability and results in need for blood transfusion. Allogenic blood transfusions increase mortality and morbidity, especially risk of infections, pulmonary and renal complications, as well as thromboembolic events. Autotransfusion is in many cases a solution but forced suction may destroy or alter blood cells because of turbulences, shear forces and contact of the blood to extrinsic surfaces. The aim of the study was the analysis of turbulence profile and development of a new suction device reducing (or avoiding) turbulences.MethodsWe registered turbulences with a microphone placed in different positions within the blood suction during surgery and analysed the spectrum. Then, we modified the circuit adding signals from optical sensors and pressure transducer to avoid air mixing and tight suction. Finally, we created the algorithm for the suction circuit regulating individualised suction modes.ResultsWe developed a new suction system based on a roller pump. We used a piezo sensor and registered the acoustic signals. The optimal position for this element was into the suction handle. After filtering the signal and further processing, we used it for regulation of the roller pump. Additionally, an optical sensor minimises air mixing due to further regulation of motor speed. Finally, a negative pressure transducer gives in case of tight suction information to the circuit stopping motor speed and equalising pressure by opening a valve before suctions starts again. The algorithm allows various suction modes in an individualised manner for specific situations in operating field.ConclusionsWe developed a new blood suction device based on a roller pump. The system is turbulence-controlled and its algorithm allows several individualised suction modes. Additional features avoid tight suction and reduce air mixing.
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Rahardjo, H., T. T. Lim, M. F. Chang, and D. G. Fredlund. "Shear-strength characteristics of a residual soil." Canadian Geotechnical Journal 32, no. 1 (February 1, 1995): 60–77. http://dx.doi.org/10.1139/t95-005.
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Shallow landslides in natural residual soils slopes are common all over the world. The slip surfaces associated with these landslides are often situated above the groundwater table. Therefore, it is important to quantify the contribution of negative pore-water pressure to the shear strength of soil. The shear-strength characteristics of residual soil from the Jurong Formation in Singapore were assessed using multistage, consolidated drained triaxial tests. These tests involved shearing under either a constant net confining pressure and varying matric suctions or under a constant matric suction and varying net confining pressures. An extended form of the Mohr–Coulomb equation was used to interpret the test results. The test results show that for matric suctions up to 400 kPa, the angle of internal friction associated with the matric suction, [Formula: see text], is similar to the effective angle of internal friction, [Formula: see text], which averages 26° for the residual soil of the Jurong Formation. The residual soil can maintain a high degree of saturation for matric suctions as high as 400 kPa. Examples involving stability analyses of a residual soil slope with varying pore-water pressure profiles indicate that soil suction contributes significantly to the factor of safety, particularly for shallow slip surfaces. Key words : residual soil, unsaturated soil, matric suction, shear strength, multistage triaxial test, slope stability.
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Tang, Gary X., and James Graham. "A possible elasticplastic framework for unsaturated soils with high-plasticity." Canadian Geotechnical Journal 39, no. 4 (August 1, 2002): 894–907. http://dx.doi.org/10.1139/t02-024.
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The paper proposes a new elasticplastic framework for unsaturated, high-plasticity, clayey soils and sandclay mixtures. The framework considers possible coupling of stress- and suction-induced hardening, leading to a yield surface that is closed or "capped" as suctions increase. This produces a stress state boundary surface in three-dimensional pqs stress space (where p is the net mean stress, q is the deviator stress, and s is the matric suction) which differs from that of other conceptual models of its kind. Yielding, a hardening law, and failure criteria for saturated soils are incorporated into the stress state boundary surface. Two parameters, equivalent pressure pe and stress ratio ηs, are introduced to form the basis of the proposed elasticplastic framework for highly plastic soils with high suctions. This provides an alternative for the stress variables net mean stress and matric suction that are commonly used in modeling unsaturated soils with lower plasticity and lower suctions. This framework has allowed results of experiments on an unsaturated sandbentonite mixture to be successfully described using elastoplasticity. Yield and failure envelopes associated with the proposed state boundary surface in pqs space can be normalized using pe and ηs in such a way that they agree with a comparable envelope for saturated specimens. Key words: unsaturated, elasticplastic, triaxial, matric suction, state boundary surface, sand-bentonite.
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Chen, Rui, Ben Zhuo Zhang, Wei Dong Lei, and Wen Bin Luo. "Response of Soil Suction to Heavy Rainfalls in a Tailings Dam." Advanced Materials Research 250-253 (May 2011): 1681–85. http://dx.doi.org/10.4028/www.scientific.net/amr.250-253.1681.
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Rainfall is a significant factor leading to failure of tailings dams. The impact of rainfall on the instability of dams is mainly reflected in the variation of negative pore-water pressure (i.e. matric suction) during rainfall infiltration. However, there is a lack of study on the effects of rainfall on suction in tailings dams. In this study, the response of suction to artificial heavy rainfalls in a tailings dam was investigated. The effects of rainfall intensity and surface vegetation conditions on the response of suction were studied. It is found that suctions at a certain depth in the tailing dam were kept constant until the wetting front reached this depth. Once suctions were altered, the values dropped rapidly. The magnitude of suction change generally decreased with depth. Rainfall infiltration mainly occurred above the depth of 40 to 80 cm when subjected to rainstorm and heavy rainstorms. Larger rainfall intensity leads to shorter response time and to larger depth affected by rainfall, implying that the tailings dam is more susceptible to shallow landslide failure under larger rainfall intensity. The existing vegetation increases infiltrability significantly and then produces an adverse effect on the stability of the tailings dam. On the other hand, it is observed that the presence of vegetation greatly prevented surface erodibility and then decreases the possibility of debris flow.
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Zhan, Tony LT, and Charles WW Ng. "Shear strength characteristics of an unsaturated expansive clay." Canadian Geotechnical Journal 43, no. 7 (July 1, 2006): 751–63. http://dx.doi.org/10.1139/t06-036.
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The shear strength characteristics of an expansive clay from China were studied by performing suction-controlled direct shear tests on both natural and compacted specimens. The tested soil was a silty clay with intermediate plasticity and medium expansion potential. A modified direct shear apparatus with a newly developed water volume indicator was used for this laboratory study. The experimental results clearly show that the dilatancy of the expansive clay increases with an increase in the applied suction for both the natural and compacted specimens. Matric suction contributes to the shear strength of the expansive clay via two different mechanisms: the contribution of capillary force to interparticle normal stress, and the effect of suction on soil dilatancy. As a result of the second mechanism, the contribution of suction to peak shear strength for the clay is more significant than that to post-failure shear strength, particularly at a high suction range. The contribution of suction to post-failure shear strength for the natural specimen is basically consistent with that for the compacted specimen. The higher peak shear strength and dilatancy for the natural specimen are related to the cementation effect of the iron and manganese oxides. The contribution of suction to shear strength for the compacted expansive clay is more significant than that for a compacted kaolin at suctions less than 100 kPa.Key words: expansive clay, matric suction, shear strength, dilatancy, direct shear test, water content.
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Hou, Li Zhu, Jochen Wenninger, and Xu Jie Li. "Influence of Soil Texture on Soil-Water Characteristic Curves of Different Sandy Loam Layers." Advanced Materials Research 955-959 (June 2014): 3607–10. http://dx.doi.org/10.4028/www.scientific.net/amr.955-959.3607.
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Characteristic curves of soil moisture, between water content and matrix suction, are the basis for solving the problems of water flow and solute movement in soils. The soil–water characteristics of five layers of depths, 0–12 cm, 12–24 cm, 24–36 cm, 36–48 cm, and 48–60 cm, were measured for a sandy loam soil from Daxing District of Beijing in the northern part of the North China Plain by a pressure membrane apparatus. Curves were fitted using the Van Genuchten model. The fit between measured data and modeled results was excellent. The soil-water characteristic curves showed the typical Sshape of the Van Genuchten model. Matrix suction decreased with an increase in soil moisture; at low suctions, soil moisture content changed to a greater extent with suction, but at high suction, changes in soil moisture content with changes in suction were small. Clay content was proportional to soil water storage capacity and was inversely related to the speed of dehydration.
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Hamdany, Abdul Halim, Martin Wijaya, Alfrendo Satyanaga, Harianto Rahardjo, Zhai Qian, Aswin Lim, and Jong Kim. "Numerical Simulation on the Effect of Infiltration and Evapotranspiration on the Residual Slope." Sustainability 15, no. 11 (May 26, 2023): 8653. http://dx.doi.org/10.3390/su15118653.
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Soil suction plays an important role in governing the stability of slopes. Environmental sustainability could be jeopardized by hazards, such as slope failures (forest destruction, landscape alteration, etc.). However, the quantification of the suction effect on slope stability is a challenging task as the soil suction is usually affected by the precipitation and evapotranspiration. Numerical simulation plays an important role in the estimation of contour in soil suction due to rainfall and evapotranspiration as long-term and widespread monitoring is rarely conducted. The result of numerical simulation is highly dependent on the accuracy of the input parameters. Hence, suction monitoring plays an important role in verifying the result of numerical simulation. However, as a conventional tensiometer is limited to 100 kPa soil suction, it is hard to verify the performance of numerical simulation where suction is higher than 100 kPa. The osmotic tensiometer developed by Nanyang Technological University (NTU) can overcome this problem. It is now possible to monitor changes in soil suction higher than 100 kPa (up to 2500 kPa) for an extended period in the field. In this study, a procedure was proposed to estimate suction changes in residual soil based on rainfall and evapotranspiration data. Numerical simulation was carried out based on the soil properties and geometry of a residual soil slope from Jurong Formation Singapore. Changes in soil suction due to rainfall and evaporation were simulated and compared with the readings from the NTU osmotic tensiometers installed at 0.15 m and 0.50 m from the slope surface in the field. It was observed that numerical simulation was able to capture the variations of suctions accurately at greater depths. However, at shallow depths, erratic suction changes due to difficulties in capturing transpiration.
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Ng, C. W. W., D. B. Akinniyi, and C. Zhou. "Experimental study of hydromechanical behaviour of a compacted lateritic sandy lean clay." Canadian Geotechnical Journal 57, no. 11 (November 2020): 1695–703. http://dx.doi.org/10.1139/cgj-2019-0301.
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Lateritic clay is widely distributed in tropical areas and used extensively for foundation materials. Compared to other soils, it is rich in iron and aluminum oxides (sesquioxides), which enhance the formation of soil aggregates. The principal objective of this study is to investigate the hydromechanical behaviour of a lateritic sandy lean clay. All specimens were compacted at the same condition and then wetted to a predefined suction (0, 50, 150 kPa). Suction-controlled isotropic compression and shear tests were carried out. Moreover, soil microstructures at various suctions were determined using the mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) techniques. The compressibility of the lateritic clay decreased by about 50% as suction decreased from 150 to 0 kPa. This is mainly because as the suction decreased to 0 kPa, the sizes of interaggregate pores decreased, as revealed by MIP data. During shearing, the critical state friction angle appeared to be independent of suction. The contribution of suction to the apparent cohesion is unexpectedly low, likely because the interaggregate pores have a low degree of saturation and the contribution of the water meniscus on shear strength is very low.
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Rao, Sudhakar M., and P. Shivananda. "Role of osmotic suction in swelling of salt-amended clays." Canadian Geotechnical Journal 42, no. 1 (February 1, 2005): 307–15. http://dx.doi.org/10.1139/t04-086.
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The present study examines the influence of extraneous salt addition on pore-fluid osmotic suction of a clay soil. The dependence of swell potentials of the salt-amended clay specimens on initial pore-fluid osmotic suction is also examined. The osmotic suctions predicted by Van't Hoff's equation are in excess or smaller than the values calculated from the pore water electrical conductivity, depending on whether the Van't Hoff factor in the Van't Hoff equation is included or not. Experimental results suggest that the salt-amended specimens absorbed water and swelled in response to matric suction and chemical concentration gradients on inundation with water in oedometer cells. Salt also diffused from the soil pores of salt-amended specimens to the reservoir water in oedometer cells in response to chemical concentration gradients. Reduction in effective stress from osmotic flow into the soil specimen and increase in interparticle repulsion from reduction in pore-water salt concentration rendered the total swell potentials of salt-amended specimens independent of initial pore-fluid osmotic suction. The initial pre-fluid osmotic suction does, however, significantly affect the rate of swelling.Key words: clays, chemical properties, swell potential, suction.
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Ng, Charles Wang Wai, Hamed Sadeghi, Fardin Jafarzadeh, Mohammad Sadeghi, Chao Zhou, and Sina Baghbanrezvan. "Effect of microstructure on shear strength and dilatancy of unsaturated loess at high suctions." Canadian Geotechnical Journal 57, no. 2 (February 2020): 221–35. http://dx.doi.org/10.1139/cgj-2018-0592.
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To investigate the influences of microstructure changes on dilatancy of unsaturated loess at high suctions, a direct shear box device using the vapour equilibrium technique was used. Through conducting two series of direct shear tests on both intact and recompacted loess specimens and also investigating microstructural changes using the mercury intrusion porosimetry (MIP) technique, a linear increase in dilatancy with suctions ranging from 8 to 230 MPa can be identified at different net stresses. The enhanced dilatancy observed is mainly attributed to desiccation-induced high suctions as the reduction in void ratio due to enhancement of suction was negligible. A macrovoid ratio, eM, may be quantified and proposed to explain the differences in the increased dilatancy of recompacted and intact loess with suction.
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Rahimi, Arezoo, and Harianto Rahardjo. "New approach to improve soil-water characteristic curve to reduce variation in estimation of unsaturated permeability function." Canadian Geotechnical Journal 53, no. 4 (April 2016): 717–25. http://dx.doi.org/10.1139/cgj-2015-0199.
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The unsaturated permeability function is often estimated from the soil-water characteristic curve (SWCC) of a soil. A complete SWCC measurement can improve the estimation of the unsaturated permeability function. In most laboratories, the SWCC can be measured up to a suction of 100 kPa using a Tempe cell. However, complete measurement of the SWCC is an expensive and time-consuming task. Therefore, this paper presents a new approach to estimate SWCC data points beyond 100 kPa suction to complement the SWCC measured up to a suction of 100 kPa. The new SWCC is then used to estimate the unsaturated permeability function. The proposed approach uses knowledge of the grain-size distribution curve and measured SWCC data at 100 kPa suction to estimate the SWCC data points beyond 100 kPa suction. To verify the proposed procedure, SWCC tests were conducted over a wide range of suctions for coarse kaolin and a triaxial permeameter system was used to directly measure unsaturated permeability of the coarse kaolin. The proposed procedure is found to reduce the variation between unsaturated permeability functions estimated by various estimation models.
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Thu, Trinh Minh, Harianto Rahardjo, and Eng-Choon Leong. "Elastoplastic model for unsaturated soil with incorporation of the soil-water characteristic curve." Canadian Geotechnical Journal 44, no. 1 (January 1, 2007): 67–77. http://dx.doi.org/10.1139/t06-091.
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An elastoplastic model is proposed in this paper that incorporates the soil-water characteristic curve (SWCC) for obtaining soil parameters of unsaturated soil. The SWCC is shown to govern the rate of change in the soil parameters for the elastoplastic model with respect to matric suction. A series of isotropic consolidation tests under different matric suctions and tests for obtaining SWCC were carried out on statically compacted kaolin specimens. Nanyang Technological University (NTU) mini suction probes were installed along the height of the specimen to measure pore-water pressures during isotropic consolidation and SWCC tests. The results of isotropic consolidation tests demonstrate the strong influence of matric suction on compressibility and stiffness of the soil specimens. The experiments were also simulated using the proposed elastoplastic model and SWCC of the compacted kaolin. The simulated results agree closely with the experimental results. In addition, the proposed elastoplastic model was also verified against published data from the literature.Key words: matric suction, yield surface, soil-water characteristic curve, mini suction probe, elastoplastic model, unsaturated soil.
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Ng, C. W. W., Q. Y. Mu, and C. Zhou. "Effects of soil structure on the shear behaviour of an unsaturated loess at different suctions and temperatures." Canadian Geotechnical Journal 54, no. 2 (February 2017): 270–79. http://dx.doi.org/10.1139/cgj-2016-0272.
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Previous studies of shear behaviour at different suctions and temperatures focused mainly on recompacted soils. Limited attention has been paid to intact soil. In this paper, the shear behaviour of intact and recompacted loess was studied using a suction- and temperature-controlled direct shear apparatus. A scanning electron microscope and mercury intrusion porosimeter were used to evaluate the microstructure of both intact and recompacted loess. For a given suction and temperature, intact specimens exhibit a higher shear stiffness and larger dilatancy than recompacted specimens. This is mainly because clay particles in intact specimens accumulate near grain contacts and stick to the grain surfaces, as revealed in scanning electron microscopy and mercury intrusion porosimetry tests. This type of clay particle distribution in intact specimens results in a more resistant structure and higher yield stress. At suctions of 0 and 200 kPa, the shear stiffness and dilatancy of recompacted specimens increase with temperature. The shear stiffness and maximum dilatancy increase by as much as 47% and 63% at suctions of 0 and 200 kPa, respectively. These increases in shear stiffness and dilatancy are attributed mainly to the continuous plastic volumetric contraction during heating, which induced strain-hardening effects. On the contrary, thermal effects on the stress–strain behaviour of intact specimens are negligible at zero suction. At a suction of 200 kPa, as soil temperature rises from 20 to 60 °C, the shear stiffness and maximum dilatancy of intact specimens decrease by 35% and 68%, respectively. It is evident that intact specimens and recompacted specimens experience opposite thermal effects.
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Haeri, S. Mohsen, Behnam Sadollahzadeh, and Vahid Zahed. "An evaluation of the effect of matric suction on the dynamic strain-dependent parameters of an unsaturated silt." E3S Web of Conferences 382 (2023): 03007. http://dx.doi.org/10.1051/e3sconf/202338203007.
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This research investigates the influence of matric suction on the variation of shear modulus and damping ratio of a silty soil in very small to medium shear strain levels. A set of laboratory experiments including three bender elements tests in addition to three resonant column-torsional shear tests have been carried out on unsaturated Firuzkuh silt specimens. In this regard, an unsaturated triaxial cell equipped with a set of bender elements and a resonant column-torsional shear device that can apply and control matric suction have been used. All specimens had an initial void ratio of 0.7 and were tested in various matric suctions under a net mean stress of 50 kPa. For this purpose, the axis translation technique has been implemented for applying matric suction, and High Air Entry Value (HAEV) ceramic discs have been used for air-water control of unsaturated silt specimens. According to the results, a significant variation of shear modulus and damping ratio has been observed with changes in matric suction and shear strain level. The output data indicate that shear modulus increases with increasing matric suction while the damping ratio decreases with an increase in matric suction. In addition, shear modulus and damping ratio decrease and increase with increasing shear strain, respectively.
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Alcoverro, J., X. Pintado, S. Olivella, E. Toprak, and Mika Niskanen. "Analysis of the Extension of the Elastic Parameters for Modelling Highly Expansive Unsaturated Soils with the Barcelona Basic Model." Advances in Materials Science and Engineering 2023 (July 1, 2023): 1–14. http://dx.doi.org/10.1155/2023/1196011.
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Modelling of engineered barrier systems (EBS) in deep geological disposals of spent nuclear fuel requires sophisticated approaches that include highly nonlinear constitutive models. The Barcelona Basic Model for Expansive soils (BBMEx) is an extension for highly expansive unsaturated soils of the Barcelona Basic Model (BBM) for slightly-to-moderately expansive unsaturated soils. In this extension, the parameter κ (logarithmic compliance with respect to changes in net pressure) of the BBM is extended to a function of suction and a set of parameters, and the parameter κ s (logarithmic compliance with respect to changes in suction) of the BBM is extended to a function of net pressure, suction, and a set of parameters. On these functions, four conditions which are satisfied in the BBM are considered. For each condition, two results are obtained: (1) the ranges of the values of the parameters such that the condition is satisfied for all positive net pressures and all non-negative suctions and (2) for given values of the parameters, the maximum net pressure and the maximum suction such that the condition is satisfied for positive net pressures and non-negative suctions. The results should help prevent unrealistic predictions of the BBMEx. The extension was used for carrying out the simulation of an infiltration test in two different bentonites and the BBMEx model parameters analysed.
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Bardanis, Michael, and Dimitrios Loukidis. "Long-term suction measurements in Greece & Cyprus. A continuous update." E3S Web of Conferences 195 (2020): 01023. http://dx.doi.org/10.1051/e3sconf/202019501023.
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The occurrence of unsaturated soils in the field has been well documented worldwide by measurements of the degree of saturation on samples taken during geotechnical investigations. On the other hand, the suction of unsaturated soils in the field, especially as part of long-term measurements, is documented very rarely and references on the subject are very few and for very few places around the world. The scarceness of this kind of measurements denies researchers perception of the anticipated suction and its possible loss or retention as a result of climatic conditions, especially in countries with warm temperate climate. Suction measurements from temporary and permanent stations in Greece and Cyprus are presented in the paper. From these -admittedly few-measurements until today, the large magnitude of suction that may occur both during summer and winter is presented, along with the possibility of long periods of these suctions being maintained. Another consequence is the range of suction values that sensors should be able to measure in regions of similar climatic conditions in order to cover the range of expected values as obtained from the measurements available so far.
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Solano, Catalina, Marie Chicaud, Stessy Kutchukian, Luigi Candela, Mariela Corrales, Frédéric Panthier, Steeve Doizi, and Olivier Traxer. "Optimizing Outcomes in Flexible Ureteroscopy: A Narrative Review of Suction Techniques." Journal of Clinical Medicine 12, no. 8 (April 11, 2023): 2815. http://dx.doi.org/10.3390/jcm12082815.
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Objective: The aim of this review is to summarize the existing suction systems in flexible ureteroscopy (fURS) and to evaluate their effectiveness and safety. Methods: A narrative review was performed using the Pubmed and Web of Science Core Collection (WoSCC) databases. Additionally, we conducted a search on the Twitter platform. Studies including suctions systems in fURS were included. Editorials, letters and studies reporting intervention with semirigid ureteroscopy, PCNL and mPCNL were excluded. Results: A total of 12 studies were included in this review. These studies comprised one in vitro study, one ex vivo study, one experimental study and eight cohort studies. The Pubmed and WoSCC searches identified three suction techniques (Irrigation/Suctioning system with control of pressure, suction ureteral access sheath (sUAS) and direct in scope suction (DISS)), and the Twitter search identified four of them. The overall results showed that suction is an effective and safe technique that improves stone-free rates, reduces operative time and limits complication rates after fURS. Conclusions: The use of suctioning during common endourological procedures has been shown to improve safety and efficacy in several indications. However, randomized controlled trials are needed to confirm this.
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Praneeth, Kokkula, Ashish Aggarwal, Sunil Kumar Gupta, and Navneet Singla. "Necessity is the mother of invention: Technical note on the use of self-designed low-cost continuous sump suction for use in microvascular anastomosis." Surgical Neurology International 10 (November 8, 2019): 216. http://dx.doi.org/10.25259/sni_170_2019.
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Background: Technical advances in microneurosurgery facilitated the continuous evolution of surgery. In many developing countries surgeons face difficulties rendering high quality services due to resource constraints. The continuous dry surgical field is essential for performing microvascular anastomosis. Commercially available sump suctions are costly and beyond the reach of most surgeons in resource-constrained countries. Methods: We designed a suction system which functions on the principles of capillary action and sump effect. Results: The improvised sump suction was used successfully in our patients for micro vascular surgery, giving us a continuous dry field and removing the chance of error by an assistant. Conclusion: The suction system was made with the use of easily available low-cost components, and worked well to the satisfaction of the surgeon.
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Lu, Hua, Yang Wang, Xiao Yan Wang, Li Jun Hou, and Xin Zhao Jiang. "Experimental Study on Test Methods of the Intergranular Suction of Unsaturated Lateritic Soil." Applied Mechanics and Materials 353-356 (August 2013): 440–45. http://dx.doi.org/10.4028/www.scientific.net/amm.353-356.440.
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This paper aims at the test methods of the suction between grains of lateritic soil which is widely distributed in southern China, and proposes the test methods and principles according to the variation of the suctions various components. This paper works over the relationship between the suction and the degree of saturation through tests, and also analyzes pore fluid chemistry influence on the suction between grains. The test results show that the test principles and methods are feasible. They also show that the quantitative relationship between the unsaturated soil’s shear strength and saturation (water content), and a new understanding of the physical meaning in unsaturated condition of X, which is a empirical parameter in the principle of Bishop‘s effective stress.
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Voottipruex, Panich, Anuchit Uchaipichat, and Ekachai Man Koksung. "Effective Stress Parameter for Unsaturated Soils under Drying and Wetting Processes." Applied Mechanics and Materials 148-149 (December 2011): 1093–97. http://dx.doi.org/10.4028/www.scientific.net/amm.148-149.1093.
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This paper presents a variation of effective stress parameter with matric suction for unsaturated soils using a comprehensive data set of suctioned-controlled shear tests under drying and wetting processes. The effective stress parameter is determined by assuming that the slope of the critical state line in the plane of deviator stress against mean effective stress is independent of matric suction. This study shows a different in relationship between the effective stress parameter and matric suction for drying and wetting processes. The values of effective stress parameter obtained from the experiments were compared with those obtained from the expressions proposed in literature.
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Elmansoury, Ahmed, and Hedya Said. "Closed suction system versus open suction." Egyptian Journal of Chest Diseases and Tuberculosis 66, no. 3 (July 2017): 509–15. http://dx.doi.org/10.1016/j.ejcdt.2016.08.001.
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McCartney, John, and Fatemah Behbehani. "Hydromechanical behavior of unsaturated soils: Interpretation of compression curves in terms of effective stress." Soils and Rocks 44, no. 3 (July 2, 2021): 1–19. http://dx.doi.org/10.28927/sr.2021.065721.
Full textAbstract:
This state-of-the-art paper on the hydromechanical behavior of unsaturated soils focuses on the interpretation of the compression curves of unsaturated soils in terms of effective stress, with the goal of understanding the relative impacts of suction on the effective stress, net yield stress, effective yield stress and slope of the virgin compression line (VCL) during a monotonic increase in net stress. A database of compression curves was compiled for both high and low plasticity fine-grained soils under a wide range of suctions, isotropic or oedometric stress states, drainage conditions (constant suction or constant water content) and preparation techniques (impact compaction, static compaction, consolidation from slurry). Most of the compression curves plotted in terms of effective stress revealed a consistent hardening response with increasing suction and a slight suction dependency on the slope VCL. Interpretation of the compression curves in terms of effective stress led to load-collapse curves with a similar shape for a wide range of soils. Most soils evaluated had a greater rate of increase in effective yield stress with suction than the rate of increase in suction stress with suction, implying that these compacted soils may be susceptible to collapse upon wetting. Inconsistent trends were observed in some studies, which were attributed partially to natural variability but also experimental issues and limitations on the range of conditions investigated. Accordingly, recommendations are provided for future studies on the compression curves of unsaturated soils to ensure that results can be clearly interpreted in terms of effective stress.
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Silva, R. G., K. C. Cameron, H. J. Di, N. P. Smith, and G. D. Buchan. "Effect of macropore flow on the transport of surface-applied cow urine through a soil profile." Soil Research 38, no. 1 (2000): 13. http://dx.doi.org/10.1071/sr99016.
Full textAbstract:
A field lysimeter experiment was conducted to determine the effect of macropore flow on the transport of surface-applied cow urine N through soil. The lysimeters (500 mm diameter by 700 mm depth) used for this experiment were collected from Templeton fine sandy loam soil (Udic Ustochrept), which had been under ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) pasture for 9–10 years. The effect of macropore flow on urine-N leaching was determined by leaching experiments under 0.5 kPa and 0 kPa water tensions (suctions) imposed on top of the lysimeter using a disc tension infiltrometer. The 0.5 kPa suction prevented soil pores >600 µm diameter from conducting water and solutes, while the 0 kPa suction allowed conduction under ‘field saturated’ condition. Pores >600 µm diameter transmitted about 98% of the total nitrogen (N) leached below 700 mm depth. The main form of N transmitted under 0 kPa was ammonium (NH4 -N), accounting for 10.5% of the total N applied at 0 kPa suction. This was significantly higher than the amount of NH 4 -N leached at 0.5 kPa suction, which accounted for 0.17% of N applied. The urea-N in the leachate reached 16 mg/L at 0 kPa suction, and accounted for 1.6% of the total N applied. No urea was detected in the leachate at the 0.5 kPa suction. The concentrations and amounts of nitrate (NO3 -N) leached were very low and did not differ between the two suctions. The forms and amounts of N leached were affected by the interactions of macropore flow and N transformations in the soil, and the environmental conditions during the two leaching events. From this work, it is recommended that stock should be removed 1–2 days before irrigation water is applied as this will allow animal urine to diffuse into soil micropores and thus decrease N leaching by macropore flow.