Available online at www.sciencedirect.com ScienceDirect Procedia Engineering 154 (2016 ) 574 581 12th International Conference on Hydroinformatics, HIC 2016 Research on the Strength and Space-time Distribution of Sedimentation of Yi-Zheng Segment in Phase- Project of Deep Water Channel Construction of Yangtze River CHEN Li-ming a, LI Ti-lai a, DOU Xi-ping a, ZHANG Xin-zhou a, GAO Xiang-yu a, XU Hui a a State Key Laboratory of Hydrology and Water Resource and Hydraulic Engineering Science Nanjing Hydraulic Research Institute, Nanjing, 210029, China Abstract Phase- Project of Deep Water Channel Construction of Yangtze River(2014-2015), including the Yi-Zheng Segment, enables the water depth of Yangtze River Channel between Nanjing and Nantong arrive 12.5 meters. This thesis analyzes the sedimentation movement of Yi-Zheng Segment with mathematical model, makes prediction of the sediment s strength and space-time distribution. The simulation results indicate that the yearly dredging quantity of 1998 and 2010, two typical hydrological years, are 1.528 million m3 and 0.499 million m3 separately. The main maintenance months are October, November and December during the dry season, while the main maintenance parts are the channel from Dadaohe to Majiakou, the channel from Majiakou to Qibaidu, the channel from Qibaidu to Longmenkou in the right branch of Shiyezhou. These results could be helped to provide support of later dredging operation for keeping deep water Channel of Yi-Zheng Segment. 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license 2016 The Authors. Published by Elsevier Ltd. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review Peer-review under under responsibility responsibility of the of organizing the organizing committee committee of HIC of 2016 HIC 2016. Keywords: Yangtze River, Yi-Zheng Segment, sediment s strength, sediment s space-time distribution; Corresponding author. Tel.: +86-025-8582-8530; fax: +86-025-8582-8555. E-mail address: lmchen@nhri.cn 1877-7058 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of HIC 2016 doi:10.1016/j.proeng.2016.07.554
Chen Li-ming et al. / Procedia Engineering 154 ( 2016 ) 574 581 575 Introduction The 12.5-meter Deep Water Channel of Yangtze River downstream Nanjing is to preliminary open up at the end of the 12th Five-Year Plan. Together with the massive deep water channel construction, the ordinary dredging maintenance quantity will rise significantly. It s rather important to forecast the time-space distribution of sediment in the 12.5-meter deep water channel, which can help to reveal the regional dredging quantity in different months, thus provides reliable support to the dredging and maintenance work plan. Phase- Project of Deep Water Channel Construction of Yangtze River(2014-2015),including the Yi-Zheng Segment, enables the water depth of Yangtze River Channel between Nanjing and Nantong arrive 12.5 meters. This thesis analyzes the sedimentation movement of Yi-Zheng Segment with mathematical model, makes prediction of the sediment s strength and space-time distribution, and provides support of later dredging operation of deep water Channel of Yi-Zheng Segment [1-2]. Equations and Establishment of Numerical Model (1)Hydrodynamics Equations, as in Eq. [1-3]. CHu CHv Z 1 0 t C C 2 2 Hu 1 C C 2 1 C C gu u v gh Z C Huu C HvuHvu Hv 2 C H C H H H t C C C C C C 2 2 Hv 1 C C 2 gv u v gh Z 1 C C CHuv CHvvHuv Hu 2 CH CH H H t CC C C C C Where, u and v are velocity components of V in and directions; is the tidal level; H is the total water depth; t is time; g is the acceleration of gravity; C is Chezy coefficient; and,,, are turbulent shear stress [3-4]. (2)Suspended Load Sediment Transport Equation, as in Eq. [4]. ( HSi ) 1 1 C Si C S i (4) ( CHuS i) ( CHvS i) ( ) ( ) i i( Si Si) t CC CC s C s C Where, is the saturation recovery coefficient of sediment; i is the settling velocity of sediment for group I; S is the sediment concentration of different grain size; i S is the sediment carrying capacity, i 3 / m S K u gh s ; and are sediment diffusion coefficient in and directions, t ; s is constant, 1.0 [4-5]. (3)Bed Load Sediment Transport Equation, as in Eq. [5]. N i Where, is the bed load sediment concentration for group I; si is the settling velocity of bed load sediment for group I; N q / Hv; i bi qbi is the bed load sediment transport rate of different grain size, which is calculated by 2 2 2 the Dou Guoren formula, 2 qbi ( k / c )( rrs /( rs r)) mi ( u v ) /( gsi ) (4)Riverbed Deformation Equation, as in Eq. [6]. n Z 1 g b b 1 gb 0 i ( Si Si ) t C C i1 3 [4-5]. (1) (2) (3) (5) (6)
576 Chen Li-ming et al. / Procedia Engineering 154 ( 2016 ) 574 581 Where, gb, g are the bed load sediment transport rate in and directions, 0 is the dry density of b sediment [4-5]. Sanjiangkou Station is chosen as the upper boundary, Liuweihekou Station is chosen as the lower boundary, with a total length of about 40 km (Figure 1). Orthogonal curvilinear grids are used and the grid scale is 10150 m, the total number of grids is 50840(410 124). The measured terrain of Yi-Zheng Segment in March 2010 is used in the model [5]. Fig.1. Schematic diagram of the scope and grid of the model Fig.2. Location of measured data Verification of Numerical Model 3.1 Model parameters The model is verified by using the measured data including tidal levels, flow velocities, flow distribution ratio, and sediment concentration of spring and neap tides(location of measured data see Figure 2) in Mar, 2010. The calculation parameters upon calibration and Verification are that roughness is from 0.02 to 0.012 linearly interpolated from upstream to downstream, time step is 0.4s, moving boundary depth is 0.01 m, and turbulent viscosity coefficient is ku H t respectively ( k =1.0 and u is drag velocity). 3.2 Results of Flow The verified results of tidal levels, flow velocity and direction are shown in Figure34. It can be seen that the simulated tidal levels basically consist with the measured ones, except for a few points, and the error is within 0.15m/s. The main and secondary channels have obvious diversion and convergence and basically reflect the flow distribution of the research reach, and the error of flow distribution ratio is within 1.30%, which are shown in Table1. Table 1. Flow distribution ratio of Yi-Zheng segment Date Location Qm 3 /s flow distribution ratio (%) flow distribution ratio(%) Error(%) 2010.03 Left Branch of Shiyezhou 36.27 36.47 0.20 18830 Right Branch of Shiyezhou 63.73 63.53-0.20
Chen Li-ming et al. / Procedia Engineering 154 ( 2016 ) 574 581 577 WaterLevelm Levelm Water Water Levelm Level m Water WaterLevelm Level Water m Fig.3. The verified results of tidal levels in Mar 2010 m s Velocity m s Velocity Distancem Distancem m s Velocity m s Velocity Distancem Distancem m s Velocity m s Velocity Distancem Distancem Fig.4. The verified results of flow velocity in Mar 2010
578 Chen Li-ming et al. / Procedia Engineering 154 ( 2016 ) 574 581 3.3 Results of Sediment Figure 5 shows the comparison of sediment concentration between measured and simulated data. It can be seen that the simulated sediment concentrations basically consist with the measured ones, except for a few points. The measured terrain from 2010.3 to 2011.2 is used to verify scouring and silting quantity in Yi-Zheng Segment. Table 2 shows the comparison of scouring and silting quantity statistical results between measured and simulated data in the channel of right branch of Shiyezhou, and the error is within 12%. Table 3 shows the comparison of scouring and silting quantity statistical results between measured and simulated data in all Yi-Zheng Segment, and the error is within 27%. Figure 6 shows the measured and simulated space distribution of scouring and silting changes. It can be seen that the simulated scouring and silting quantity basically consist with the measured ones, and the space distribution of scouring and silting change also consist with the measured ones. Table 2. Comparison of statistical results in the channel of right branch of Shiyezhou (Unit:10E06m 3 ) 2010.3-2011.2 Dadaohe to Majiakou Majiakou to Qibaidu Qibaidu to Longmenkou 3.27 2.23 0.71 2.91 2.46 0.68 Error -11% 10% -4% Table 3. Comparison of statistical results in all Yi-Zheng Segment (Unit: 10E06m 3 ) 2010.3-2011.2 Siyuangou to Shierwei Left Branch of Shiyezhou Right Branch of Shiyezhou Shiyezhou to Guazhou 0.14-5.89 11.29-2.89 0.16-4.50 14.31-2.25 Error 14.3% -23.6% 26.7% -22.1% m3 Sediment kg m3 Sediment kg Distancem Distancem m3 Sediment kg m3 Sediment kg Distancem Distancem m3 Sediment kg kg m3 Sediment Distancem Distancem Fig.5. The verified results of sediment concentration in Mar 2010
Chen Li-ming et al. / Procedia Engineering 154 ( 2016 ) 574 581 579 4. Simulation of the Case Fig.6. The measured and simulated space distribution of scouring and silting change In Yi-Zheng segment the maintenance water depth is 7.5 meters, and the main maintenance channel is the right branch of Shiyezhou including the channel from Dadaohe to Majiakou, the channel from Majiakou to Qibaidu, the channel from Qibaidu to Longmenkou. The channel for statistical quantity of dredging are shown in Figure 7. Considering the uncertainty of hydrological years of Yangtze river, the water-sediment changes after the impoundment of the Three Gorges, and the water-sediment transport s influence to the channel scouring and silting improvement, this study selected 1998 and 2010 as the typical hydrological years for the simulation. Fig.7. The statistical quantity of dredging and distribution of scouring and silting 4.1Dredging Simulation in Typical Hydrological Year 1998 Table 4 have shown the monthly dredging quantity and maximum dredging thickness in typical hydrological year 1998. It s indicated that the total accumulated dredging quantity was 1.528 million m 3 in the main channel. The dredging measures frequently occurred in October, November and December during the dry season, due to the lower water level. The lower water level is, the bigger dredging quantity is, and also the more thick is. Figure 8 have shown the distribution of dredging quantity of the water channel in typical hydrological year 1998. It s indicated that the maximum dredging quantity is 0.911 million m 3, mainly distributed in the channel from Dadaohe to Majiakou, occurred in Nov 1998, which accounted for 90% of the yearly total quantity, and the maximum dredging thickness is 2.92m.
580 Chen Li-ming et al. / Procedia Engineering 154 ( 2016 ) 574 581 Table 4. The monthly dredging quantity and maximum thickness in 1998(Unit:10E06m 3 ) Month Dadaohe to Majiakou Majiakou to Qibaidu Qibaidu to Longmenkou 1 0 0 0 0 0 0 2 0 0 0 0 0 0 3 0 0 0 0 0 0 4 0 0 0 0 0 0 5 0 0 0 0 0 0 6 0 0 0 0 0 0 7 0 0 0 0 0 0 8 0 0 0 0 0 0 9 0 0 0 0 0 0 10 0.0016 0.24 0 0 0 0 11 0.9112 2.92 0.0428 1.52 0.006 1.46 12 0.4816 0.56 0.0824 0.56 0.0024 0.56 Part Statistics 1.3944 0.1252 0.0084 Total 1.528 4.2Dredging Simulation in Typical Hydrological Year 2010 Table 5 have shown the monthly dredging quantity and maximum dredging thickness in typical hydrological year 2010. It s indicated that the total accumulated dredging quantity was 0.499 million m 3 in the main channel. The dredging measures frequently occurred in October, November and December during the dry season, due to the lower water level. The lower water level is, the bigger dredging quantity is, and also the more thick is. Figure 9 have shown the distribution of dredging quantity of the water channel in typical hydrological year 2010. It s indicated that the maximum dredging quantity is 0.275 million m 3, mainly distributed in the channel from Dadaohe to Majiakou, occurred in Oct 2010, which accounted for 90% of the yearly total quantity, and the maximum dredging thickness is 1.60m. Table 5. The monthly dredging quantity and maximum thickness in 2010(Unit:10E06m 3 ) Month Dadaohe to Majiakou Majiakou to Qibaidu Qibaidu to Longmenkou 1 0 0 0 0 0 0 2 0 0 0 0 0 0 3 0 0 0 0 0 0 4 0 0 0 0 0 0 5 0 0 0 0 0 0 6 0 0 0 0 0 0 7 0 0 0 0 0 0 8 0 0 0 0 0 0 9 0 0 0 0 0 0 10 0.2752 1.60 0 0 0.0024 0.54
Chen Li-ming et al. / Procedia Engineering 154 ( 2016 ) 574 581 581 11 0.0616 0.14 0 0.02 0.0004 0.12 12 0.1568 0.30 0.0016 0.3 0.0012 0.30 Part Statistics 0.4936 0.0016 0.0040 Total 0.4992 Fig.8. Distribution of scouring and silting of the channel in Nov 1998 Fig.9. Distribution of scouring and silting of the channel in Oct 2010 5. Conclusions (1)Based on the observed hydrological, sediment and topographical data, this thesis has established a mathematical water sediment model of Yi-Zheng Segment, Yangtze River. Through calibration and validation of the tidal level, velocity, scouring and silting changes of riverbed, the thesis proves that the model can well simulate the water-sediment movement characteristics. (2)The simulation model can forecast the strength and time-space distribution of sedimentation in the deep-water channel of Yi-Zheng Segment under typical hydrological conditions. With monthly dredging in typical hydrological year, the accumulated dredging quantity was 0.499 million m 3, and 1.528 million m 3 in 1998 and 2010. The simulation result shows that the dredged quantity was closely related to the yearly water input and sediment input. the channel from Dadaohe to Majiakou is the main dredging region in typical hydrological years in the dry season from October to December. The simulation result provides support of later dredging operation of deep water Channel of Yi-Zheng Segment. Acknowledgements The study is supported by the National Key Technologies R&D Program of China during the 12th Five-year Plan Period. References [1] Wen Yun-cheng, Xia Yun-feng, Wu Dao-wen, Du De-jun, Xu Hua, Zhang Shi-zhao. Optimization on general layout scheme of 12.5 m deepwater channel phase I project from Nanjing down the Yangtze River. Port & Waterway Engineering, 2013, 477(3): 1-10. [2]Li Li, Li Xin. Channel arrangement of 12.5m deepwater channel construction phase I project of Yangtze River downstream Nanjing,Taicang- Nanjing section. Port & Waterway Engineering, 2012, 468(7): 21-25. [3]Zhou J G. Numerical solutions of the shallow water equations with discontinuous bed topography [J]. Int. JNumer Meth Fluids, 2002, 38,769-788. [4] Dou Xi-pingGao Xiang-yu, Zhang Xin-zhou. (2011).Prediction of Backsilting in river segment from Nanjing to Yangtze Estuary with two-dimensional water-sediment mathematical model. Nanjing: Nanjing Hydraulic Research Institute, 2011. [5] Dou Xi-pingZhang Xing-nong, Zhu Li-jun. etal. (2012).Research on the Strength and Space-time Distribution of 12.5m deepwater channel Construction of Yangtze River form Nanjing to Yangtze Estuary. Nanjing: Nanjing Hydraulic Research Institute, 2012.