利用数值模拟方法预测辫状河砂体几何形态

Braid river sandbody shape forecast by numerical simulation method

辫状河是自然界重要的河流类型之一。利用砂体沉积过程数值模拟方法可以预测辫状河砂体的几何形态。在建立了辫状河砂体沉积过程的数学方程后，根据现代辫状河沉积特征，设计了辫状河沉积过程的模拟条件，计算域长15km、宽10km，流量按50a一遇大洪水设计，模拟过程到1970a时，辫状河沉积过程基本达到平衡状态，此时砂体最大厚度约14m，出现在计算域2．5～3．5km处，以中砂沉积为主。计算过程中可识别6种沉积单元，包括辫状水道(砂体的平均长宽比2．45，平均宽厚比72．6)、纵向砂坝(平均长宽比2．02，平均宽厚比86．7)、斜列砂坝(平均长宽比2．27，平均宽厚比74．9)、废弃河道、堤岸、越岸沉积。主要沉积单元砂体几何参数之间的相关关系较好。

Braid river is important sediment type in nature. The braid river sandbody geometry shape could be forcasted by using numeri-cal simulation method. After mathematic equations of braid river sandbody deposition process are established, simulation conditions are designed for braid river sedimentation process based on deposition characteristics of modern braid river. The length and width of the calculation field is 15km and 10km, respectively. The flow rate is designed as the most serious flood in 50 years. When simulating process carry through year 1970, braid river sedimentation process reach stabilization state with the largest sand thickness of 14m appearing in 2.5-3.5km in calculating field. Medium sand is the main sediment. Six sediment units could be identified: braid channel with average length/width of 2.45 and average width/thickness of 72.6; lognitudinal bar with average length/width of 2.02 and average width/thickness of 86.7; diagonal bar with average length/width of 2.27 and width/ thickness of 74.9; abandon bar; bank and exceed bank sediment. The correlativity among sand body geometry parameters are preferable.