双层堤基管涌模型试验尺寸效应的数值模拟

NUMERICAL SIMULATION OF SIZE EFFECT IN PIPING EROSION MODEL TEST FOR DOUBLE-STRATUM DIKE FOUNDATIONS

借助双层堤基砂槽模型试验的成果,建立双层堤基管涌动态破坏过程的数学模型和模拟方法。采用数值仿真方法研究双层堤基管涌模型试验的模型尺寸效应的规律和机制,提出双层堤基管涌小尺寸的模型试验的修正方法。研究结果表明:(1)采用概化的数学模型可以很好地模拟堤基管涌模型试验结果的尺寸效应影响及管涌动态发展过程,计算结果和试验结果吻合较好,同时得到不同模型砂样内部的渗流场分布和一些难以观测到的数据。(2)模型尺寸对堤基管涌的临界水头、发展过程有较大影响,临界水头随模型宽度和深度的增加而减小,但减小的幅度逐渐减小。(3)通过理论和数值模拟分析,现有模型试验结果受模型尺寸影响较大,对现有模型进行改进,模型宽度增大为堤身长度(试验模型槽管涌口至上游临水面的距离为1.4 m)的1.7倍,模型深度增大为堤身长度的0.85倍。改进后管涌破坏区的影响半径约为堤身长度的0.85倍。

Mathematical model and simulation methodology for dynamic development process of piping erosion in double-stratum dike foundations are established. Moreover, laws and mechanism of size effect in piping erosion model tests for double-stratum dike foundations are studied by numerical simulation： and correction methodology for small scale piping erosion model tests in double-stratum dike foundations is also presented. Numerical results show that： （1） Using the generalized mathematical model, size effect in piping erosion model tests for double-stratum dike foundations and dynamic development process of piping erosion are well simulated and numerical results fit the model test ones very well. What is more, seepage field distribution inside sand specimen and data hard to observe in model tests are obtained. （2） Model test sizes have a great influence on the critical hydraulic head and dynamic development process. Critical hydraulic head decreases with gradually smaller amplitudes as the width and depth of the model increase. （3） By theoretical analysis and numerical simulation, the available model test results are influenced greatly by model size. The model is improved with width and depth increase to 1.7 times and 0.85 times of dike body length separately, while the distance from exit of piping to upstream surface is 1.4 m. The influence radius of piping failure zone after being modified is about 0.85 times of dike body length.