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Showing 7 results for Pressure Distribution

J. Jalili, M. K. Jafari, A. Shafiee, J. Koseki, T. Sato,
Volume 10, Issue 2 (6-2012)

A series of tests and also numerical analyses were conducted to explore the mechanical behavior of a mixture of coarse gravelsize
particles floating in a matrix of silt, sand or clay. The research is a step forward in an ongoing investigation on behavior of
composite clay, which is used as the core material of some large embankment dams all over the world. After providing the reader
with an overall image about behavior of such materials through the literature, the paper focuses on a predominant feature of the
composite soil behavior: increase of non-deformable solid inclusions in a mixture leads to formation of heterogeneity of stress
field, excess pore water pressure and strain distribution along the specimens. This paper mainly probes formation of such
heterogeneity by the aid of special experiments and also numerical analyses. In addition to loading details, it is clarified through
the paper that position of inclusions relative to loading direction also affects heterogeneity of stress/strain and excess pore water
pressure distribution through the mixture. Despite the former, the latter redistributes with a rate proportional to material
hydraulic conductivity.

H. Ghiassian, M. Jalili, I. Rahmani, Seyed M. M. Madani,
Volume 11, Issue 4 (12-2013)

The concept of Geosynthetic Cellular Systems (GCS) has recently emerged as a new method in construction of breakwaters and coastal protective structures. The method potentially has significant advantages compared to conventional systems from the standpoint of constructability, cost effectiveness, and environmental considerations. This paper presents the results of physical model testing on the hydraulic responses of GCS structures under wave action. A series of model tests were carried out in a wave flume on GCS models with different shapes and soil types, subjected to various wave characteristics. Horizontal wave forces acting on the models were measured at different elevations. The maximum horizontal force in each test was calculated and compared with conventional formula of predicting wave pressure on breakwaters. The results show that Goda’s equation overestimates the hydrodynamic water pressure on these structures. This can be attributed to the influence of seeping water through the GCS models because of relative permeability of the GCS.
C. Vieira,
Volume 12, Issue 1 (1-2014)

This paper presents a simplified approach to estimate the resultant force, which should be provided by a retention system, for the equilibrium of unstable slopes. The results were obtained with a developed algorithm, based on limit equilibrium analyses, that assumes a two-part wedge failure mechanism. Design charts to obtain equivalent earth pressure coefficients are presented. Based on the results achieved with the developed computer code, an approximate equation to estimate the equivalent earth pressure coefficients is proposed. Given the slope angle, the backslope, the design friction angle, the height of the slope and the unit weight of the backfill, one can determine the resultant force for slope equilibrium. This simplified approach intends to provide an extension of the Coulomb earth pressure theory to the stability analyses of steep slopes and to broaden the available design charts for steep reinforced slopes with non-horizontal backslopes
O. Farzaneh, F. Askari, J. Fatemi,
Volume 12, Issue 4 (12-2014)

AWT IMAGEPresented is a method of two-dimensional analysis of the active earth pressure due to simultaneous effect of both soil weight and surcharge of strip foundation. The study’s aim is to provide a rigorous solution to the problem in the framework of upper-bound theorem of limit analysis method in order to produce some design charts for calculating the lateral active earth pressure of backfill when loaded by a strip foundation. A kinematically admissible collapse mechanism consisting of several rigid blocks with translational movement is considered in which energy dissipation takes place along planar velocity discontinuities. Comparing the lateral earth forces given by the present analysis with those of other researchers, it is shown that the results of present analysis are higher (better) than other researchers’ results. It was found that with the increase in AWT IMAGE, the proportion of the strip load (q) which is transmitted to the wall decreases. Moreover, Increasing the friction between soil and wall ( AWT IMAGE) will result in the increase of effective distance ( AWT IMAGE). Finally, these results are presented in the form of dimensionless design charts relating the mechanical characteristics of the soil, strip load conditions and active earth pressure.

O. Nazari, E. Jabbari, H. Sarkardeh,
Volume 13, Issue 1 (3-2015)

To dissipate energy and invert excessive discharge flow away from high dams into plunge pool, flip buckets are commonly designed and optimized by hydraulic model studies. In the present study, performance of chute flip buckets in different hydraulic and geometry conditions was investigated using experimental data of five different physical models. The collected experimental data such as Froude number, radius of flip bucket and slope of chute covered a wide range of chute flip buckets in prototype. By analyzing the data, relations for dynamic values of maximum and minimum pressures and their location along the flip bucket were extracted. Moreover, pressure distribution along the central axis of flip bucket was defined. Finally, results of the present research were compared with that of the other researches. Results of this study could be used in the design of chute flip buckets in hydraulic engineering.
Shuai Li, Jian-Min Zhang, Wei-Lin Xu, Jian-Gang Chen, Yong Peng, Jun-Ning Li, Xiao-Long He,
Volume 14, Issue 1 (1-2016)

The cavitation erosion induced by high flow velocities is very prominent in high head and large unit discharge tunnel. Air entrainment is an effective technology to solve this problem. In this study, numerical simulation and physical model test are applied to the comparative study of air-water flows on bottom and lateral aerator in tunnel. The flow pattern, aeration cavity, air concentration and pressure distribution were obtained and there is a close agreement between the numerical and physical model values. The hydraulic characteristic and aeration effect of anti-arc section are analyzed. The results indicated that added lateral aeration facilities on 1# and 2# aerator can weaken backwater and increase the length of the bottom cavity, but it is limited to improve the air concentration and protect sidewall downstream of the ogee section. Air concentration improved on side walls downstream of anti-arc section when added lateral aeration facility on 3# aerator. The black water triangle zone disappeared and the floor and side walls well protected.

Yang Wang, Kai Su, Hegao Wu, Zhongdong Qian,
Volume 15, Issue 4 (6-2017)

The reinforced concrete bifurcation in hydropower station is consistently under high internal water pressure, and its diameter is usually larger than common duct junctions. In order to diminish or to decrease the heavy plastic zone and stress concentration, structure rounding is commonly used on bifurcation. This will bring some changes to the flow characteristic of bifurcation, and it is an interesting attempt to figure out the influence of structure rounding optimization. The Realizable k-ε model was employed in Computational Fluid Dynamics numerical simulation. The water pressure distribution was compared quantitatively at several certain sections. Furthermore, uneven pressure is analyzed by relative standard deviation. Hydraulic characteristics are discussed as well, including flow pattern, excavation volume and head loss in different working conditions. The results indicate that the pressure of pipe wall is uneven, and the maximum and minimum pressure value has a differential of 0.3% - 1.2% compared to relative static water pressure. The pressure unevenness will increase after structure rounding, and it has a positive correlation with structure rounding radius. At the same time, it is more reasonable for structure rounding in obtuse angle region than that in acute angle region, on account of well-distributed flow conditions and better economic benefit.

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