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4
Eshev Sobir Samatovich, Karshi Engineering-Economic Institute, candidate of technical sciences, assistant professor; Uzbekistan, Karshi, E-mail: telnets(a)mail.ru
DEFORMATION OF COASTAL ESCARPMENT OF EARTH CHANNELS UNDER THE ACTION OF SURFACE WAVES
Abstract: As it was mentioned earlier that laboratory experience of the author and dependencies of S. H. Abaliyans to advantage of the riverbed of the limiting balance is designed method of the calculation morph metrical features of dynamically firm riverbeds of the greater earth channels, working under the condition of wind waves. The general regularities of deformation of coast escarpment is described under the action of surface waves.
Keywords: wave flow, sediment transport by waves and currents, the intermittence of water streams, saturated sediments, ripples.
The questions about choice of the optimum transverse profile of earth channels, occupies the leading place when designing the hydro irrigation system. Urgency of this problem is confirmed with unusual interest of the researchers, which belongs the big amount of publication in this area [1-3]. The Difficulty of the decision of given problems on modern stage is connected with that circumstance that in purpose of increasing to efficiency of the work of the channel in row of the events happens to design these vitally important for agriculture hydro technical buildings for mode, which velocity of the current of water exceed not washing importance to laying under the bed of the earth channels soil. Such statement of the problem brings to raise the row of the additional problems, in accordance with the account of transporting abilities of the flow in deformed channels and with the forecast of possible planned and high-altitude deformation of their riverbed. Besides, increasing of the requirements when designing greater channels conducts to need of taking into consideration of not stationary hydraulic factor (the waves which is made by the wind, ship and, long waves of the different origin and etc.), which can render the essential influence on erosion processes, running in riverbed, and conduct to change transporting abilities of riverbed flow. The last question has been described in domestic and foreign literature in insufficient degree and limited in most cases by analysis of the
contribution of the long gravitation waves (on type of the waves of the leash in riverbeds of the river) in running in channels of the riverbed forming processes. The study of deformation the riverbeds under the action of short (wind and ship) waves are dedicated only in separate publications, in which main attention is paid to shaping ashore forming of riverbed relief appearing as a result of destructions of the waves under their approach to ashore [4]. Therefore the question about the general regularity of deformation of coast escarpment of earth channels under the action of wind and ship waves remains open. In this work development of simplified schemes of the calculation of dynamically firm transverse profile of greater earth channels, working at the presence of existing wind and ship waves with the following of its checking for receptions of experimental material by author [7]. Herewith further we shall consider that the amount of transported alluviums in channel and missed consumption of water define the width, average of depth and longitude gradient of the riverbed, but the form of the cross-section of the channel conditions the distribution tangential appearing in channel under the action of different factor (the drain current, wind and ship waves and etc.). So the width, average depth and gradient of dynamical firm channels with the provision of the amount of entering alluviums are counted on the base of the physical approach [5], but the form of the
cross-section is counted with use of the method enticing power (the tangential tension). As source for calculation of the form of the firm transverse profile of the channel was chosen by S. H. Abaliyans that was accepted for condition statically firm riverbed:
h _ ί (dh/dy)2
К V Ъ2Ф*
(1)
Here h-local depth, - a maximum depth in channel, Y- transverse coordinate, - a corner of internal friction of given soil. Beside the following study [2] by author is given suggestions about possibility of the use (1) for description the parameters of the channel, transporting alluviums. For this S. H. Abaliyans suggested (1) to enter instead of corner of the natural escarpment (ф0) of its
reduced importance:
Ф, =
Фо
1,65'
(2)
Where ф„ - corner of internal friction of the soil that is under the dynamic stability.
Hereinafter it Was used the confirmed laboratorial data by gravitation authors [7] suggested that under the action of surface гравитационных waves occurs the partial destruction of coast escarpment of channel that finds its expression in shaping more full profile of the bottom in this zone. For quantitative account of the process of weeding of coast escarpment under the action of wind and ship waves in the expression is entered new value of the corner of the natural escarpment, which can be recorded with provision for dimensionality in the manner of:
Ы2Ф,-к
U:
Ы
(3)
Where V - factor molecular cinimatic viscosity; g-speed of the free fall; U,m - amplitude specific ten-
sions, appearing on riverbed of the flow under wind waves, which is defined in accordance with dependency by author.
In expression (3) empirical factor remains the unknown.
In purpose of the quantitative acknowledgement of the proposed mechanism of the erosion of coast escarpment under the action of wind waves and for determination of the value of the empirical factor “K”, entering in
(3) was organized series of the experimental studies by the author [7].
The Following stage of the studies is the determinations of importance of the empirical factor «К» in expression (3). As a result of integrating (l), after uncomplicated operation we have:
№Ф'~К
1 —
ul
ivs)2
2 h
-Y
2
(4)
Where hmb - maximum depth of canal when wave to
the direction of current.
Решая (4) относительно искомого коэффициента К получим:
К =
м2
U
Ъ2ФЯ -
Ah1
Г
1 V h
mb J
(5)
2
For the dynamical firm land canals when no waves we have:
— = 1-h
( 3 h γ]
В h
m У
Where
h =
ЩФ\
(6)
(7)
/'! „ and В average depth, and width of the channel
2
4
with the absence of waves, which are defined on stated in [5] the methods in accordance with given by consumption of water and amount of inflow of water into the channel by pump.
Substituting (7) in (4) we get a transverse profile of the bottom of dynamically firm channel in the condition of wind waves:
— = 1-h
rub
1 —
6h
Y
V В J
0,2717;
(vgf
2 h
-y
(8)
2
Using the dependencies К has allowed on given transverse profile of the bottom the results were gotten in the course of laboratory studies to define importance of the sought factor, at which changed within fc = 05. 0,1 (the
average importance fc = 0,27). For determination of the width of the channel in condition of the imposition of the waves on current (Bb) was used suggestion, which majority of the events is confirmed given called on laboratory studies: imposition wave drain current, bring about increase the width of the riverbed, does not обуславливает
observable change an area of its cross-section. This suggestion is founded on receptions in the course of experiment fact that erosion of the channel when cut off part is accompanied approximately equal accumulation of intensities of alluvium in interfacing zone of the coast escarpment from the central part of channel.
Figure I. The Collation accounting (1) and measured (2) of the transverse profiles of the experimental channel as of laboratory experience, A - drain mode, В - imposition of the surface waves on drain current
Using the dependencies К has allowed on given transverse profile of the bottom the results were gotten in the course of laboratory studies to define importance of the sought factor, at which changed within fc = 05. 0,1 (the average importance fc = 0,27). For determination of the width of the channel in condition of the imposition of the waves on current (Bb) was used suggestion, which majority of the events is confirmed given called on laboratory studies: imposition wave drain current, bring about increase the width of the riverbed, does not обуславливает observable change an area of its crosssection. This suggestion is founded on receptions in the course of experiment fact that erosion of the channel when cut off part is accompanied approximately equal accumulation of intensities of alluvium in interfacing zone of the coast escarpment from the central part of channel.
Use of this suggestion was recorded in the manner of:
B/2
J hdy = const, tgtpB1 = tgfaBl
0
It was allowed to get the expressions for calculation of the width (Bb) and maximum of the channel under the condition of wind waves in the manner of:
B, = B. =B
(9)
Collation computable on fig. 1 is brought on recommended methods and measured in laboratory condition, the profiles of the cross-section of dynamically firm channel with the presence of surface, gravitation waves, which shows enough good correspondence to results of calculation with actual data. Thereby, the work in this work has allowed to offer the algorithm calculation of the morph metric features of the large earth channels, working in the condition wind waves, of study increased hydraulic limits to applicability used in approach on the base of the account of the influence of surface gravitation waves on running in riverbed channel of erosion accumulating processes.
References:
1. Abaliyanc S. H. Firm and changing modes in the artificial riverbed. L., Gidrometeoizdat, -1981.-239 p.
2. Abaliyans S. H. The Form of the riverbed of the limiting balance. Sb. scientific. The Works Central Asia. Nil irrigation, - 1981.-P. 12-21,- 162 p.
3. Altunin S. T. The Regulation of riverbeds of the rivers. - M.: сельхозиздат, - 1962. - 271p.
4. The Mass E. I., Kantarzhi I. Recommendations on calculation of wind waves and transport alluvium in greater channel. - M., NNIIS, - 1986. - 64 p.
5. The Mass E. I., Mikhinov A. E. Recommendations on hydraulic calculation of earth channel with the provision of their transporting abilities. - Tashkent, - 1987. - 62 p.
6. Mikhinov A. E., Eshev S. S. The Calculation of the parameters of friction in the condition of not stationary turbulent border layer. - M.: - 1987. - 9 p. Manuscript деп. In VINITI 17.11.87, M8088-V87.
7. Mikhinov A. E., Eshev S. S. The Experimental study of the shaping the firm transverse profile of greater earth channel in not stationary hydraulic condition. - M. - 1987. - 39 p. Manuscript dept. In VINITI 01.11.87,7080-V87.
