PSEUDOSTATIC DESIGN FACTORS FOR STABILITY OF WATERFRONT-RETAINING WALL DURING EARTHQUAKE

2010 ◽  
Vol 04 (04) ◽  
pp. 387-400 ◽  
Author(s):  
DEEPANKAR CHOUDHURY ◽  
SYED MOHD AHMAD
Keyword(s):  
Retaining Wall ◽  
Pressure Ratio ◽  
Free Water ◽  
Hydrodynamic Pressure ◽  
Wall Friction ◽  
Sliding Stability ◽  
The Stability ◽  
Seismic Forces ◽  
Design Factors ◽  
Similar Kind

The paper presents a methodology for seismic design of rigid watferfront-retaining wall and proposes simple design factors for the sliding stability under seismic condition. Conventional pseudostatic approach has been used for the calculation of the seismic forces, while for the calculation of the hydrodynamic pressure, Westergaard's approach has been used. In addition, the hydrodynamic force has been considered from both the upstream and downstream sides of the waterfront-retaining wall under free water condition of the backfill. Simplified expression for the calculation of the equivalent weight of the wall which would be needed to maintain sliding stability is presented. It has been observed that the presence of water both on the upstream and downstream sides of the wall has serious destabilizing effect on the stability of the wall. It is noticed that as the height of the water inside the backfill increased from 0.00 to a height equal to the height of the wall itself, i.e., the backfill is fully submerged, the weight of the wall needed for the later case is around 3 times more than what would be needed for the former case. Similar observations were also made by varying other parameters like the horizontal and vertical seismic acceleration coefficients, height of the water on the upstream side of the wall, and soil and wall friction angles. The pore pressure ratio and the inclination of the ground, however, did not have significant effect on the results. Due to nonavailability of the results of similar kind in literature, an exact comparison for the present results could not be made. Only partial comparison of the present results is made with an already existing methodology for the dry backfill case only, in which no presence of water has been considered on the other side of the wall. This comparison shows a good agreement with the present results. The proposed pseudostatic design factors for the case of wet backfill with the presence of water on both sides of the wall are claimed to be unique.

scholarly journals Sliding failure analysis of a gabion retaining wall at km 31+800 of Lubuk Selasih – Padang city border highway, Indonesia

2020 ◽  
Vol 156 ◽  
pp. 02005
Author(s):  
Hanafi ◽  
Hendri Gusti Putra ◽  
Andriani
Keyword(s):  
Stability Analysis ◽  
Contact Area ◽  
Retaining Wall ◽  
Field Investigation ◽  
Wire Mesh ◽  
Soil Parameters ◽  
Road Section ◽  
Sliding Stability ◽  
The Stability ◽  
National Road

In August 2010, there was a landslide on the down-slope of national road section at Km 31+800 Lubuk Selasih – Padang City Border. In order to prevent further damage, it was necessary to make an immediate repair by constructing a gabion retaining wall. Since this repair was so urgent, physical and mechanical soil parameters for the stability analysis were determined from literature data. The stability analysis considered dangers of overturning, sliding, and soil bearing capacity. For the sliding stability analysis, the value for friction considered only the interaction between the soil and the base of the retaining wall, with the assumption that the contact area was equal to the total area of the entire base of the retaining wall. After the construction was completed, sliding failure occured due to pressure from the backfill embankment. This research performs a reanalysis of the retaining wall stability using soil and gabion parameters determined from field investigation and laboratory testing. In this reanalysis the friction contact area was assumed to be between the soil and the wire mesh of retaining wall. With these parameters and assumption, the main cause of sliding failure became clear, indicating that this approach increased the accuracy of stability analysis for gabion retaining walls.

Sliding Stability of Retaining Wall Supporting c-Φ Backfill under Pseudo-Statically Seismic Active Load

2013 ◽  
Vol 4 (1) ◽  
pp. 1-16
Author(s):  
Sima Ghosh
Keyword(s):  
Factor Of Safety ◽  
Retaining Wall ◽  
Earth Pressure ◽  
Wall Friction ◽  
Dynamic Factor ◽  
Active Earth Pressure ◽  
Seismic Active Earth Pressure ◽  
Wedge Surface ◽  
Wide Range ◽  
Sliding Stability

The sliding stability of retaining wall is one of the four important stability criteria for the safe design of retaining wall. Here an attempt is made to determine the sliding stability of retaining wall under seismic loading condition supporting c- F backfill considering both soil and wall inertia using pseudo-static method. The analysis for seismic active earth pressure for that particular study is done in such a way to develop a single critical wedge surface which is more realistic. The effect of wide range of variation of parameters like angle of internal friction of soil, angle of wall friction, cohesion, adhesion, seismic acceleration are studied on normalized seismic active earth pressure variation, wall inertia factor, thrust factor, combined dynamic factor and dynamic factor of safety against sliding. Results are presented in terms of formula for critical wedge surface and seismic active earth pressure and non-dimensional charts for the variation of different factors. Finally, a failure zone against sliding is recommended in the Factor of safety against sliding charts.

Roles of vanes in diffuser on stability of centrifugal compressor

2019 ◽  
Vol 233 (14) ◽  
pp. 5380-5392
Author(s):  
Wangzhi Zou ◽  
Xiao He ◽  
Wenchao Zhang ◽  
Zitian Niu ◽  
Xinqian Zheng
Keyword(s):  
High Pressure ◽  
Centrifugal Compressor ◽  
Dynamic Pressure ◽  
Pressure Ratio ◽  
Pressure Rise ◽  
Rotating Stall ◽  
Centrifugal Compressors ◽  
Compression System ◽  
The Stability ◽  
Rotating Instability

The stability considerations of centrifugal compressors become increasingly severe with the high pressure ratios, especially in aero-engines. Diffuser is the major subcomponent of centrifugal compressor, and its performance greatly influences the stability of compressor. This paper experimentally investigates the roles of vanes in diffuser on component instability and compression system instability. High pressure ratio centrifugal compressors with and without vanes in diffuser are tested and analyzed. Rig tests are carried out to obtain the compressor performance map. Dynamic pressure measurements and relevant Fourier analysis are performed to identify complex instability phenomena in the time domain and frequency domain, including rotating instability, stall, and surge. For component instability, vanes in diffuser are capable of suppressing the emergence of rotating stall in the diffuser at full speeds, but barely affect the characteristics of rotating instability in the impeller at low and middle speeds. For compression system instability, it is shown that the use of vanes in diffuser can effectively postpone the occurrence of compression system surge at full speeds. According to the experimental results and the one-dimensional flow theory, vanes in diffuser turn the diffuser pressure rise slope more negative and thus improve the stability of compressor stage, which means lower surge mass flow rate.

A Study of Influences of Inlet Total Pressure Distortions On Clearance Flow in an Axial Compressor

2021 ◽  
Author(s):  
Guoming Zhu ◽  
Xiaolan Liu ◽  
Bo Yang ◽  
Moru Song
Keyword(s):  
Total Pressure ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Leading Edge ◽  
Stall Margin ◽  
Flow Cells ◽  
Static Pressure Distribution ◽  
Speed Flow ◽  
Clearance Flow ◽  
The Stability

Abstract The rotating distortion generated by upstream wakes or low speed flow cells is a kind of phenomenon in the inlet of middle and rear stages of an axial compressor. Highly complex inflow can obviously affect the performance and the stability of these stages, and is needed to be considered during compressor design. In this paper, a series of unsteady computational fluid dynamics (CFD) simulations is conducted based on a model of an 1-1/2 stage axial compressor to investigate the effects of the distorted inflows near the casing on the compressor performance and the clearance flow. Detailed analysis of the flow field has been performed and interesting results are concluded. The distortions, such as total pressure distortion in circumferential and radial directions, can block the tip region so that the separation loss and the mixing loss in this area are increased, and the efficiency and the total pressure ratio are dropped correspondingly. Besides, the distortions can change the static pressure distribution near the leading edge of the rotor, and make the clearance flow spill out of the rotor edge more easily under near stall condition, especially in the cases with co-rotating distortions. This phenomenon can be used to explain why the stall margin is deteriorated with nonuniform inflows.

Map Width Enhancement Technique for a Turbocharger Compressor

2013 ◽  
Vol 136 (6) ◽  
Author(s):  
Subenuka Sivagnanasundaram ◽  
Stephen Spence ◽  
Juliana Early
Keyword(s):  
Performance Improvement ◽  
Peak Pressure ◽  
Pressure Ratio ◽  
Comparison Study ◽  
Heavy Duty ◽  
Recirculating Flow ◽  
Heavy Duty Diesel ◽  
And Performance ◽  
The Stability ◽  
The Impact

This paper presents an investigation of map width enhancement and the performance improvement of a turbocharger compressor using a series of static vanes in the annular cavity of a classical bleed slot system. The investigation has been carried out using both experimental and numerical analysis. The compressor stage used for this study is from a turbocharger unit used in heavy duty diesel engines of approximately 300 kW. Two types of vanes were designed and added to the annular cavity of the baseline classical bleed slot system. The purpose of the annular cavity vane technique is to remove some of the swirl that can be carried through the bleed slot system, which would influence the pressure ratio. In addition to this, the series of cavity vanes provides a better guidance to the slot recirculating flow before it mixes with the impeller main inlet flow. Better guidance of the flow improves the mixing at the inducer inlet in the circumferential direction. As a consequence, the stability of the compressor is improved at lower flow rates and a wider map can be achieved. The impact of two cavity vane designs on the map width and performance of the compressor was highlighted through a detailed analysis of the impeller flow field. The numerical and experimental study revealed that an effective vane design can improve the map width and pressure ratio characteristic without an efficiency penalty compared to the classical bleed slot system without vanes. The comparison study between the cavity vane and noncavity vane configurations presented in this paper showed that the map width was improved by 14.3% due to a significant reduction in surge flow and the peak pressure ratio was improved by 2.25% with the addition of a series of cavity vanes in the annular cavity of the bleed slot system.

Oscillations of a moderately underexpanded choked jet impinging upon a flat plate

1996 ◽  
Vol 315 ◽  
pp. 267-291 ◽  
Author(s):  
Chih-Yu Kuo ◽  
Ann P. Dowling
Keyword(s):  
Experimental Data ◽  
Flat Plate ◽  
Pressure Ratio ◽  
Feedback Mechanism ◽  
Pressure Waves ◽  
Stagnation Flow ◽  
Stability Threshold ◽  
Shock Position ◽  
The Stability ◽  
Plate Distance

The oscillation of a moderately underexpanded choked jet impinging upon a flat plate is investigated both analytically and numerically. The feedback mechanism between oscillations of the standoff-shock and the plate is clarified. Pressure waves produced by the motion of the shock are reflected by the plate. In addition, oscillations in the shock position lead to downstream entropy fluctuations, which generate pressure waves as they are convected through the stagnation flow near the plate. A linear stability analysis is used to investigate the stability threshold and frequencies of oscillation, as a function of jet pressure ratio and nozzle-to-plate distance. The analytical predictions are compared to results from a numerical simulation and to the experimental data of Powell (1988) and Mørch (1963, 1964).

Stall inception mechanisms in a contra-rotating fan operating at different speed combinations

2019 ◽  
Vol 234 (8) ◽  
pp. 1041-1052 ◽  
Author(s):  
MP Manas ◽  
AM Pradeep
Keyword(s):  
Pressure Ratio ◽  
Pressure Sensors ◽  
Stability Limit ◽  
Leading Edge ◽  
Axial Direction ◽  
Tip Leakage Flow ◽  
Stall Inception ◽  
Unsteady Pressure ◽  
Stall Cells ◽  
The Stability

Contra-rotating fan is a concept that can possibly replace the present-day conventional fans due to its several aerodynamic advantages. It has the potential to improve the stability limit and can achieve a higher pressure ratio per stage. One of the advantages of a contra-rotating fan is its capability to operate both the rotors at different speeds. In the present study, experiments are carried out at different speed combinations of the rotors and the stall inception phenomenon is captured using high-response unsteady pressure sensors placed on the casing upstream of the leading edge of rotor-1. The unsteady pressure data are investigated using wavelet and Fourier analysis techniques. It is observed that the mechanism of stall inception is different for different speed combinations. The pre-stall disturbances fall in different frequency ranges for different speed combinations. For the range of speed combinations investigated, the frequency of appearance of stall cells of rotor-1 does not depend on the speed of rotor-2. A higher speed of rotation of rotor-1 leads to a higher frequency of appearance of stall cells and a lower speed of rotation of rotor-1 leads to a lower frequency of appearance of stall cells. For all the speed combinations, there is a range of frequency where no disturbance is observed and this range is termed as the ‘no-disturbance zone’. Disturbances are observed at lower frequencies and at frequencies close to the blade passing frequency. In order to understand the flow physics in detail, computational analysis is carried out for different speed combinations of the rotors. For a higher speed of rotor-2, it is observed that the suction effect of rotor-2 is significant enough to pull the tip-leakage flow towards the axial direction. Thus, the suction effect of rotor-2 plays a significant role in determining the stall of the stage.

scholarly journals Experimental Investigation of Seismic-Induced Hydrodynamic Pressures on a Vertical Wall under Conditions of Wave Resonance

2017 ◽  
Vol 2017 ◽  
pp. 1-11
Author(s):  
YiLiang Zhou ◽  
LingKan Yao ◽  
MingYuan Gao ◽  
Hongzhou Ai
Keyword(s):  
Vertical Wall ◽  
Hydrodynamic Pressure ◽  
Sine Wave ◽  
Shaking Table ◽  
Initial Water ◽  
Wave Resonance ◽  
The Stability ◽  
Experimental Pressure ◽  
Good Agreement ◽  
Dominant Frequencies

The distribution of hydrodynamic pressure acting on the structural face of a dam significantly influences the stability of the dam. The present study investigates the development of the hydrodynamic pressure acting on the surface of a dam at different heights with respect to time during earthquakes with different dominant frequencies using a shaking table. The results demonstrate that the variation in the hydrodynamic pressure significantly follows the seismically accelerated wave motion in the absence of resonance. However, under conditions of resonance, the fluctuations in the hydrodynamic pressure exhibit similarities with a sine wave, and the positive peak values present some hysteresis. The experimental pressure values in the absence of resonance present parabolic distributions with respect to the water height that are in good agreement with the corresponding hydrodynamic pressures determined by Westergaard’s equation, while conditions of wave resonance produce a uniform distribution of hydrodynamic pressures with greater values and much longer periods of increased hydrodynamic pressure than the case of nonresonance. In addition, the seismic frequency, fundamental frequency of the reservoir, maximum peak seismic acceleration, and initial water depth are treated as variables. An empirical equation is derived to predict the maximum hydrodynamic pressure in conjunction with wave resonance conditions.

Evaluation of Seismic Displacement of Quay Walls for the Passive Case Under Earthquake and Tsunami

2010 ◽  
Author(s):  
Yongliang Lin ◽  
Mengxi Zhang ◽  
Xinxing Li
Keyword(s):  
Retaining Wall ◽  
Earth Pressure ◽  
Seismic Loading ◽  
Passive Earth Pressure ◽  
Block Method ◽  
Rotational Displacement ◽  
Passive Condition ◽  
Seismic Displacement ◽  
Quay Wall ◽  
Seismic Forces

Prediction of the seismic rotational displacements of retaining wall under passive condition is an important aspect of design in earthquake prone region. In this paper, a rotating block method is developed to calculate the rotational displacements of quay walls based on rigid foundations under seismic loading and tsunami for the passive earth pressure condition. The proposed method considers the combined effect of the seismic forces, hydrostatic and hydrodynamic forces and tsunami force acting on the quay wall. Variations of different parameters involved in the analysis suggest sensitiveness of the rotational displacement and provides a better guideline for design.

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