| With the increasing demand for shipping in mountain rivers,higher requirements are put forward for the passing capacity of locks,and the work of lock renovation and expansion is carried out one after another.Mountain rivers are often meandering,wide and narrow,in the shape of coupling,and their river channel is often the ideal dam site for shipping hubs.However,after the widening of the water flow is slow,sediment fall silt,coupled with the mountain rivers"river nature like curved"characteristics of the river and shoreline curved,easy to form a large scale,complex evolution mechanism of the beach.For the complex beach section of the lock renovation and expansion project,the lock layout is limited by the existing buildings around,often only in the existing lock location for renovation and expansion,increasing the difficulty of the lock layout.In addition,under the squeeze of the complex beach,the flow direction and velocity change,resulting in the complex navigable water flow conditions in the gate area,which further increases the difficulty for the lock layout.For this reason,it is necessary to carry out experimental research,optimize the layout of locks,coordinate the relationship between locks and complex beaches,and propose corresponding measures to improve the navigable water flow conditions in the entrance area and ensure the safety of ships entering and leaving the locks.In this thesis,based on a typical mountainous river section with complex continental beach,Baishiyao first-line lock re-expansion project,physical model test is used to study the downstream gate area navigable water flow conditions and improvement measures after the re-expansion of Baishiyao first-line lock,and the lower approach channel arrangement and three panel island remediation measures to meet the navigational demand are proposed.The main research results of this thesis are as follows:(1)By collecting the topographic and satellite map data of the downstream section of Baishiyao,we analyzed that the downstream Sanbanzhou was mainly influenced by the operation mode of the hub,the alternation of abundant and dry water periods and the channel regulation,and the evolution mechanism was complicated,forming the present-day Sanbanzhou side-banks with a complete form and following the evolution rule of"withering,flooding and siltation".(2)Under the current conditions,the main channel mainstream flows obliquely into the lower approach channel mouth gate area due to the effect of picking and narrowing of the Sanbanzhou,resulting in the formation of oblique cross-flow on the right side of the mouth gate area and poor navigable water flow conditions.Therefore,physical model tests were conducted to investigate the effects of various options under the two improvement measures of dredging and installation of additional flow dividers on the navigable flow conditions in the lower approach channel mouth gate area.The results of the study showed that both measures had a certain improvement effect on the navigable flow conditions in the lower approach channel gate area,but the navigable flow conditions in the gate area gradually deteriorated as the flow increased.(3)The multi-measure combination scheme arrangement of simultaneous expansion and dredging and extension of the flow barrier can further improve the navigable water flow conditions in the lower approach channel mouth gate area.The results of the study show that the scheme widens the navigable water in the turning section of the route and forms a 180m braking section,which effectively improves the navigable water flow conditions in the lower approach channel mouth gate area with the downstream flow rate Q≤3860m~3/s.(4)Using the dynamic bed physical model test,the sediment flushing and siltation stability study was conducted for the multi-measure combination scheme.The research results show that the dredging slope of Sanbanzhou dredging trench is stable,and the overall form is intact and stable;the sediment siltation in the lower approach channel mouth gate area is not large,and the impact on the navigable water flow conditions in the lower approach channel mouth gate area is small. |
