Simulation And Control Factors Of Underwater Distributary Channel In Lake Delta

The traditional theory holds that underwater distributary channel is an underwater extension part of the water distributary channel,but in recent years some experts and scholars have proposed that the underwater distributary channel was formed from the water level rising before the water distributary channel.In view of the above problems,it is of great theoretical and practical significance to simulate the underwater distributary channel of the delta front.In this paper,a systematic study of the genetic mechanism,influencing factors and distribution rules of underwater distributary channel is carried out by means of indoor physical simulation experiments,and a complete experiment simulation system of indoor experiment and field observation is formed by comparing with the Yanchang Delta in Ordos Basin.The experiment is divided into two kinds,which are the physical simulation under constant parameters and the change of parameters.The number of main parameters is three,which are the gradient,the water level and the velocity.The results show that the development period of delta can be divided into super high construction period,high construction period and low construction period according to the different development scale of different time periods.In the low construction period,it can be divided into uniform development period and lateral development period according to the different development form of sand body.The oblique development period.The size of the delta is closely related to the size of the parameters.Through the experiment,it is recognized that the selection of the parameters has an important influence on the development of the delta.In general,the smaller the slope is,the lower the water level is,the greater the flow velocity is,the larger the scale of the delta development is,the smaller the slope is,the lower the water level is,the greater the flow velocity is,the larger the underwater distributary channel is.The experimental process shows that the accumulation of coarse sediment on the surface of the sand body is a necessary condition for the formation of water distributary channel.The water distributary channel enters the lake to form the underwater distributary channel,and the sediment transport through the water distributary channel and the underwater distributary channel and deposit the channel end sand body at the front edge position.In the case of development,the underwater distributary channel usually appears in the low construction period.Compared with the underwater distributary channel located on both sides,the number of underwater distributary channels in front of the underwater distributary channel is relatively small,but the scale is larger.The data analysis shows that the three types of water distributary channel,underwater distributary channel and channel end sand body are positively correlated,and have better fitting with the existing empirical formulas.Comparing with the delta of Yanchang Formation in Ordos Basin,we can know the advantages and disadvantages of indoor simulation,and then we can better guide the experiment.After comparison,it is found that there are both similarities and differences.Compared with the branch channel,the main channel and the branch channel are both large and large,and the channel will experience three types of development: concentric filling,lateral shear and lateral splice.It is different that the end of the branch channel of the Yanchang delta is usually pointed out because of its limited space.However,for the Delta Delta,the growth rate is faster and the time is shorter,and there is no evidence to be left after the development of the delta.