Effect of Duration and Pattern of Hydrographs on Scour Around Pier in Sharp Bend Under Incipient Motion and Live Bed Conditions

As 180-degree meanders are observed in abundance in nature, a meandering channel with two consecutive 180-degree bends was designed and constructed to investigate bed topography variations. These two 180-degree mild bends are located between two upstream and downstream straight paths. In this study, different mean velocity-to-critical velocity ratios have been tested at the upstream straight path to determine the meander’s incipient motion. To this end, bed topography variations along the meander and the downstream straight path were addressed for different mean velocity-to-critical velocity ratios. In addition, the upstream bend’s effect on the downstream bend was investigated. Results indicated that the maximum scour depth at the downstream bend increased as a result of changing the mean velocity-to-critical velocity ratio from 0.8 to 0.84, 0.86, 0.89, 0.92, 0.95, and 0.98 by, respectively, 1.5, 2.5, 5, 10, 12, and 26 times. Moreover, increasing the ratio increased the maximum sedimentary height by 3, 10, 23, 48, 49, and 56 times. The upstream bend’s incipient motion was observed for the mean velocity-to-critical velocity ratio of 0.89, while the downstream bend’s incipient motion occurred for the ratio of 0.78.

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VELOCITY APPROACH FOR INCIPIENT MOTION

ISH Journal of Hydraulic Engineering ◽

10.1080/09715010.2010.10515001 ◽

2010 ◽

Vol 16 (2) ◽

pp. 47-58

Author(s):

Hradaya Prakash

Keyword(s):

Incipient Motion

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Incipient motion conditions for single rock fragments in simulated rill flow

Earth Surface Processes and Landforms ◽

10.1002/esp.3290130304 ◽

1988 ◽

Vol 13 (3) ◽

pp. 225-237 ◽

Cited By ~ 14

Author(s):

D. Torri ◽

J. Poesen

Keyword(s):

Incipient Motion ◽

Rock Fragments ◽

Rill Flow

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Vessel navigation risk and stern-swing index in sharp bend channels

Ocean Engineering ◽

10.1016/j.oceaneng.2021.109640 ◽

2021 ◽

Vol 238 ◽

pp. 109640

Author(s):

Tao Yan ◽

Dongyue Qian ◽

Yaqing Shu ◽

Yunping Yang ◽

Rui Xu

Keyword(s):

Sharp Bend

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Microearthquake seismicity and tectonics of Coastal Northern California

Bulletin of the Seismological Society of America ◽

10.1785/bssa0600051669 ◽

1970 ◽

Vol 60 (5) ◽

pp. 1669-1699 ◽

Cited By ~ 7

Author(s):

Leonardo Seeber ◽

Muawia Barazangi ◽

Ali Nowroozi

Keyword(s):

High Frequency ◽

Fault Plane ◽

San Andreas Fault ◽

High Gain ◽

Strike Slip ◽

Fault System ◽

Northern California ◽

Fault Plane Solutions ◽

Sharp Bend ◽

San Andreas

Abstract This paper demonstrates that high-gain, high-frequency portable seismographs operated for short intervals can provide unique data on the details of the current tectonic activity in a very small area. Five high-frequency, high-gain seismographs were operated at 25 sites along the coast of northern California during the summer of 1968. Eighty per cent of 160 microearthquakes located in the Cape Mendocino area occurred at depths between 15 and 35 km in a well-defined, horizontal seismic layer. These depths are significantly greater than those reported for other areas along the San Andreas fault system in California. Many of the earthquakes of the Cape Mendocino area occurred in sequences that have approximately the same magnitude versus length of faulting characteristics as other California earthquakes. Consistent first-motion directions are recorded from microearthquakes located within suitably chosen subdivisions of the active area. Composite fault plane solutions indicate that right-lateral movement prevails on strike-slip faults that radiate from Cape Mendocino northwest toward the Gorda basin. This is evidence that the Gorda basin is undergoing internal deformation. Inland, east of Cape Mendocino, a significant component of thrust faulting prevails for all the composite fault plane solutions. Thrusting is predominant in the fault plane solution of the June 26 1968 earthquake located along the Gorda escarpement. In general, the pattern of slip is consistent with a north-south crustal shortening. The Gorda escarpment, the Mattole River Valley, and the 1906 fault break northwest of Shelter Cove define a sharp bend that forms a possible connection between the Mendocino escarpment and the San Andreas fault. The distribution of hypocenters, relative travel times of P waves, and focal mechanisms strongly indicate that the above three features are surface expressions of an important structural boundary. The sharp bend in this boundary, which is concave toward the southwest, would tend to lock the dextral slip along the San Andreas fault and thus cause the regional north-south compression observed at Cape Mendocino. The above conclusions support the hypothesis that dextral strike-slip motion along the San Andreas fault is currently being taken up by slip along the Mendocino escarpment as well as by slip along northwest trending faults in the Gorda basin.

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