三峡水库135～139m运行期土脑子河段冲淤条件分析

土脑子河段位于三峡水库变动回水区五羊背至鹭鸶盘,长约3km,蓄水前具有汛期淤积,汛末及汛后冲刷,年内冲淤基本平衡的规律。三峡水库135~139m运行期,受坝前水位、来水来沙条件以及河道形态等因素综合影响,年内有冲有淤,累积为淤,其中汛期为主要淤积期,汛末及消落期是主要冲刷期。分析表明,当坝前水位139m、流量大于10000m3/s时,河床开始冲刷;随着坝前水位消落,入库流量增大,冲刷强度逐渐增强,在流量15000m3/s左右时冲刷强度最大;当坝前水位135m、流量大于23000m3/s时,河床开始淤积,随着入库流量增大,淤积强度逐渐增强。

Analysis on scouring and silting process in Tunaozi reach during the Three Gorges Reservoir operation period of water level from 135 to 139 m

Tunaozi reach locates in the variable backwater region of Three Gorges Reservoir(TGR) from Wuyangbei to Lusipan,about 3 km long.Before the TGR operation,it had the rule of silting in flood periods and scouring at the end of and after flood periods,and the annual quantity of scouring and silting keeps good balance.When the TGR is operated at water level from 135 to 139 m,the net sedimentation in the Tunaozi reach was abserved and the sedimentation process exhibited deposition in flood periods and erosion at late flood periods and low water level periods.The analysis showed that when the water level at dam site is 139 m and the discharge is more than 10000m~3/s,the river bed begins to scour.As the water level declines and the coming discharge increases,the scouring intensity gradually enhances,and it reaches the maximum around the discharge of 15000m~3/s.When the water level at dam site is 135 m and the discharge is more than 23000m~3/s,river bed begins to silt,and as the in coming discharge increases,the silting intensity is also greater.