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Water distribution networks : design and control for intermittent supplyVairavamoorthy, Kalanithy January 1994 (has links)
No description available.
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Transmission of seismic waves in the soil media with variation of pore water pressure and effect on the dynamic behavior of structural foundations.Chan, Kai-I 22 August 2002 (has links)
ABSTRACT
The semi-finite cone model is adopted and modified to discuss the dynamic responses of the foundations, when the problem of liquefaction under the effect of cyclic loading is considered. The dynamic responses of the foundations caused by variation of the soil properties are also included. To achieve a better simulative of the physical phenomenon, this research employs the concept of wave reflections between soil layers.
The responses observed for the foundation are vertical displacements, horizontal displacements, rotational angles, and twist angles in different seismic waves. Time-domain analysis is applied, so the research is constructed in time-domain completely.
The soil conditions in this research are simulated as a single layer and layered system. Two types of the force simulation are employed; one is regular cycle force, and the other is irregular. To better understand the liquefaction, behavior of the variation of pore water pressure has been taken into accounts and analyzed focusly.
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EFFECTS OF ADDITION OF LARGE PERCENTAGES OF FLY ASH ON LIQUEFACTION BEHAVIOR OF SAND.Regmi, Gaurav 01 August 2014 (has links)
The liquefaction resistance of a saturated medium sand with varying amount of non-plastic type F fly ash was evaluated by conducting cyclic triaxial tests. The test results were used to evaluate the effect of addition of various percentages of fly ash on the liquefaction resistance of Ottawa sand. The effect of cyclic shear stress and confining pressure on liquefaction resistance of the sand-fly ash mixtures was the main scope of this research. In addition, the Young's Modulus and Damping Ratio for sand-fly ash mixtures were also determined. A comprehensive experimental program was conducted in which 50 stress controlled cyclic triaxial tests were performed on a clean sand, sand containing 25%, 30%, 50% and 70% fly ash at a constant relative density of 50%. The results show that sand containing 25% fly ash has the highest liquefaction resistance under cyclic loading in comparison to clean sand and sand containing 30%, 50% and 70% fly ash. The cyclic resistance goes on decreasing as the fly ash content further increases. The test result also shows that the liquefaction resistance of the clean sand and sand containing 70% fly ii ash is almost same. The test results were also examined in terms of the conceptual framework of Thevanayagam (2000). The effects on liquefaction resistance were also measured in terms of pore water pressure generation and deformation of the sample. As the confining pressure increases, shear stress required to cause initial liquefaction of the sample also increases. Modulus of Elasticity was seen to increase with increase in confining pressure and decrease with increase in axial strain for all cases of sand-fly ash mixtures used in these tests. The damping ratio of the sample increases with the increase in axial strain upto about 1% and then it either decreases or remains constant thereafter. There was no clear correlation of damping ratio with confining pressure.
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The Effects of Vibration on the Penetration Resistance and Pore Water Pressure in SandsBonita, John Anthony 07 November 2000 (has links)
The current approach for using cone penetration test data to estimate soil behavior during seismic loading involves the comparison of the seismic stresses imparted into a soil mass during an earthquake to the penetration resistance measured during an in-situ test. The approach involves an indirect empirical correlation of soil density and other soil related parameters to the behavior of the soil during the loading and does not involve a direct measurement of the dynamic behavior of the soil in-situ. The objective of this research was to develop an approach for evaluating the in-situ behavior of soil during dynamic loading directly through the use of a vibrating piezocone penetrometer.
Cone penetration tests were performed in a large calibration chamber in saturated sand samples prepared at different densities and stress levels. A total of 118 tests were performed as part of the study. The piezocone penetrometer used in the investigation was subjected to a vibratory load during the penetration test. The vibratory units used in the investigations were mounted on top of a 1m section of drill rod that was attached at the lower end to the cone penetrometer. Pneumatic impact, rotary turbine, and counter rotating mass vibrators were used in the investigation. The vibration properties generated by the vibratory unit and imparted into the soil were measured during the penetration test by a series of load cells and accelerometers mounted below the vibrator and above the cone penetrometer, respectively. The tip resistance, sleeve friction and pore water pressure were also measured during the test by load cells and transducers in the cone itself.
The vibration and cone data were compiled and compared to evaluate the effect of the vibration on the penetration resistance and pore water pressure in the soil mass. The results of the testing revealed that the influence of the vibration on the penetration resistance value decreased as the density and the mean effective stress in the soil increased, mainly because the pore water pressure was not significantly elevated throughout the entire zone of influence of the cone penetometer at the elevated stress and density conditions. An analysis of the soil response during the testing resulted in the generation of a family of curves that relates the soil response during the vibratory and static penetration to the vertical effective stress and density of the soil. The data used to generate the curves seem to agree with the proposed values estimated through the empirical relationship. An evaluation of the effects of the frequency of vibration was also performed as part of the study. The largest reduction in penetration resistance occurred when the input vibration approximated the natural frequency of the soil deposit, suggesting that resonance conditions existed between the input motion and the soil. An energy-based approach was developed to compare the energy imparted into the soil by the vibrator to the energy capacity of the soil. The input energy introduced into the soil mass prior to the reduction in penetration resistance agrees well with the energy capacity of the soil, especially in tests at the low effective stress level where a high excess pore water pressure was observed. / Ph. D.
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Lateral swelling pressure in variably saturated expansive clayGarrett, Steven Ray 12 May 2023 (has links) (PDF)
Lateral swelling pressure induced in expansive soils upon wetting can adversely impact the performance and integrity of earthen structures and foundations. The yearly cost associated with damage to structures from expansive clays in the United States is estimated to exceed the loss associated with natural disasters such as earthquakes, floods, and hurricanes. The main objective of this dissertation is to provide new insight into the evolution of lateral swelling pressure in variably saturated expensive soils under infiltration via physical testing. In the first part of this study, a new laboratory-scale testing apparatus was built to measure lateral and vertical swelling pressures under anisotropic conditions. The testing apparatus was used to investigate the effect of compaction level on lateral swelling pressure in an expansive clay collected from central Arkansas. Results show that the higher the compaction, the higher the lateral swelling pressure. In contrast, compaction was found to have an insignificant effect on the vertical swelling pressure at a compaction level of less than 90%. In the second part, the laboratory-scale testing apparatus was employed to test the effects of four additives (lime, lime kiln dust, cement, and cement kiln dust). The results showed that the addition of a high calcium additive could significantly reduce the swelling pressures of expansive clay. The third part of the dissertation involved full-scale testing of lateral pressures in an expansive clay upon infiltration. A heavily instrumented 3-m high masonry wall backfilled with an expansive clay was built and subjected to infiltration. The degree of saturation, pore-water pressure, temperature, suction, and lateral and vertical pressures were monitored at different locations during the test. Results showed that the development of lateral pressure is rapid during initial saturation and levels out as the clay approaches saturation levels. This finding highlights the importance of monitoring lateral pressure over time to accurately predict its behavior. The study also found that lateral pressure develops prior to vertical pressure, depending on the area and restraint.
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Effects of heterogeneity distribution on hillslope stability during rainfallsCai, Jing-sen, Yan, E-chuan, Yeh, Tian-chyi Jim, Zha, Yuan-yuan 04 1900 (has links)
The objective of this study was to investigate the spatial relationship between the most likely distribution of saturated hydraulic conductivity (K-s) and the observed pressure head (P) distribution within a hillslope. The cross-correlation analysis method was used to investigate the effects of the variance of lnK(s), spatial structure anisotropy of lnK(s), and vertical infiltration flux (q) on P at some selected locations within the hillslope. The cross-correlation analysis shows that, in the unsaturated region with a uniform flux boundary, the dominant correlation between P and Ks is negative and mainly occurs around the observation location of P. A relatively high P value is located in a relatively low Ks zone, while a relatively low P value is located in a relatively high Ks zone. Generally speaking, P is positively correlated with q/Ks at the same location in the unsaturated region. In the saturated region, the spatial distribution of K-s can significantly affect the position and shape of the phreatic surface. We therefore conclude that heterogeneity can cause some parts of the hillslope to be sensitive to external hydraulic stimuli (e.g., rainfall and reservoir level change), and other parts of the hillslope to be insensitive. This is crucial to explaining why slopes with similar geometries would show different responses to the same hydraulic stimuli, which is significant to hillslope stability analysis. (C) 2016 Hohai University. Production and hosting by Elsevier B.V.
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Mixtures of methane and water under extreme conditionsPruteanu, Ciprian Gabriel January 2018 (has links)
The hydrophobic effect has been a topic of research for decades, not only due to its importance as the primary building block of much of chemistry (it dictates which solvent can dissolve which solutes) and biology (guiding protein binding and gene expression) but also due to it being a fundamental physical process. The commonly held opinion is that 'like dissolve like', implying polar substances can readily mix with other polar substances, and similarly for apolar ones, but polar and apolar would separate and tend to stay isolated from one another (like oil in water). We have developed a quantitative imaging method that can be used in tandem with Raman spectroscopy in order to investigate the effect of high pressure on a model hydrophobic system - water and methane. Our study revealed an unexpectedly large increase in the amount of methane that can readily mix with water once a rather modest pressure has been applied to the system. Thus, the solubility of CH4 in H2O starts abruptly increasing at 1.3 GPa and reaches a maximum of 44(3) mole % at 2.1 GPa, showing no pressure dependence upon further compression. We have tried to reproduce the observed experimental behaviour using classical molecular dynamics simulations deploying a range of widely used water potentials (SPC/E, TIP4P, TIP3P), but unfortunately no quantitative or even qualitative agreement was reached with experiments. Finally, in order to understand the atomic level changes that enable this increased amount of methane to dissolve in water, we have performed neutron scattering measurements along with EPSR (empirical potential structure refinement) fits to the data in order to solve the structure of the fluid mixture. These revealed a tendency towards maintaining the H-bond network present in water and homogeneous mixing. Despite the network staying similar to the one found in pure fluid water at milder pressures and temperatures (close to ambient conditions), the H-bonds seem more disordered and show a greater variability in their lengths.
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A method for measuring smooth geomembrane/soil interface shear behaviour under unsaturated conditionsJogi, Manoj 12 December 2005
Geomembranes are one of the most widely used geosynthetics in various civil engineering applications. Their primary function is as a barrier to liquid or vapour flow. Smooth Geomembranes are frequently used in combination with different soils, and due to their low surface roughness, are challenging to design to ensure adequate shear strength along the smooth geomembrane-soil interface. It is important to use the appropriate values of interface shear strength parameters in the design of slopes incorporating one or more geomembranes in contact with soils. The parameters are determined by conducting direct shear test on the geomembrane-soil interface. Laboratory tests of interface shear strength for geomembranes and soil are typically carried out with no provision for measurement of pore pressures at the soil/geomembrane interface. <p>This thesis deals with study of smooth geomembrane-soil interfaces, particularly under unsaturated conditions. The various factors that affect the interface shear behaviour are also studied. The tests were conducted using a modified direct shear box with a miniature pore pressure transducer installed adjacent to the surface of the geomembrane. Geomembranesoil interface shear tests were carried out with continuous measurement of suction in close proximity to the interface during the shearing process thus making it possible to analyze test results in terms of effective stresses. The method was found to be suitable for unsaturated soils at low values of matric suction. <p>Results of interface shear tests conducted using this method show that it is quite effective in evaluating interface shear behaviour between a geomembrane and an unsaturated soil. The results suggest that soil suction contributes to shearing resistance at low normal stress values. At lower normal stress values, the interface shear behaviour appears to be governed only by the magnitude of total normal stress. <p> At high normal stresses, the failure mechanism changed from soil particles sliding at the surface of geomembrane to soil particles getting embedded into the geomembrane and plowing trenches along the direction of shear. A plowing failure mechanism resulted in the mobilization of significantly higher shear strength at the geomembrane soil interface. It was found that placement water contents near saturated conditions results in lower effective stresses, a shallower plowing mechanism and lower values of mobilized interface shear strength.
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A method for measuring smooth geomembrane/soil interface shear behaviour under unsaturated conditionsJogi, Manoj 12 December 2005 (has links)
Geomembranes are one of the most widely used geosynthetics in various civil engineering applications. Their primary function is as a barrier to liquid or vapour flow. Smooth Geomembranes are frequently used in combination with different soils, and due to their low surface roughness, are challenging to design to ensure adequate shear strength along the smooth geomembrane-soil interface. It is important to use the appropriate values of interface shear strength parameters in the design of slopes incorporating one or more geomembranes in contact with soils. The parameters are determined by conducting direct shear test on the geomembrane-soil interface. Laboratory tests of interface shear strength for geomembranes and soil are typically carried out with no provision for measurement of pore pressures at the soil/geomembrane interface. <p>This thesis deals with study of smooth geomembrane-soil interfaces, particularly under unsaturated conditions. The various factors that affect the interface shear behaviour are also studied. The tests were conducted using a modified direct shear box with a miniature pore pressure transducer installed adjacent to the surface of the geomembrane. Geomembranesoil interface shear tests were carried out with continuous measurement of suction in close proximity to the interface during the shearing process thus making it possible to analyze test results in terms of effective stresses. The method was found to be suitable for unsaturated soils at low values of matric suction. <p>Results of interface shear tests conducted using this method show that it is quite effective in evaluating interface shear behaviour between a geomembrane and an unsaturated soil. The results suggest that soil suction contributes to shearing resistance at low normal stress values. At lower normal stress values, the interface shear behaviour appears to be governed only by the magnitude of total normal stress. <p> At high normal stresses, the failure mechanism changed from soil particles sliding at the surface of geomembrane to soil particles getting embedded into the geomembrane and plowing trenches along the direction of shear. A plowing failure mechanism resulted in the mobilization of significantly higher shear strength at the geomembrane soil interface. It was found that placement water contents near saturated conditions results in lower effective stresses, a shallower plowing mechanism and lower values of mobilized interface shear strength.
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Relations Between Pore Water Pressure, Stability And Movements In Reactivated LandslidesGundogdu, Bora 01 February 2011 (has links) (PDF)
Slope movements cause considerable damage to life and property in Turkey as well as in the world. Although they do not typically cause loss of life, slow landslide movements can severely damage structures, interrupt the serviceability of lifelines / and, related stabilization efforts can be too costly. Most of these slow-moving landslides are reactivated landslides in stiff clays and shales, and they are mainly triggered by rainfall induced high pore water pressures. In this study, a number of reactivated, slow-moving landslide case histories with extensive pore pressure and movement data are selected for further analysis. For these landslides, the relation between pore water pressures, factor of safety and rate of movements of the slide are investigated by using limit equilibrium and finite element methods. It is found that there is a nonlinear relationship between these three variables. Sensitivity of slow moving landslides to changes in pore water pressure is developed by defining the percent change in factor of safety and percent change in pore pressure coefficient, for 10-fold change in velocity. Such relations could especially be useful in planning required level of remediation, for example, to decide on how many meters the ground water level should be lowered at a certain piezometric location, so that the stability increases to a desired level of F.S., and movement rates are reduced to an acceptable slow rate.
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