降雨入渗是诱发滑坡的关键因素,研究斜坡降雨入渗规律对于滑坡的预测与防范具有重要意义。传统的Green-Ampt模型及改进的Green-Ampt模型均假定入渗过程为均匀饱和入渗,忽略了入渗过程中湿润锋锋面上方非饱和区的存在。针对这一不足,首先,基于达西定律分析斜坡内基质吸力的分布规律;然后,结合非饱和土VG模型得到了斜坡内湿润区含水量沿深度变化的函数关系;最后,基于改进的Green-Ampt模型推导了考虑土体非饱和特性的斜坡降雨入渗模型,并将其引入到无限斜坡稳定性分析当中。研究结果表明:与数值解和现有模型相比,考虑土体非饱和特性的降雨入渗模型能更加准确地反映降雨入渗的过程,基于改进模型计算的稳定性系数较好地揭示了恒定降雨强度下斜坡稳定性的变化规律,证明了该方法的正确性和适用性。

Rainfall infiltration is a key factor which induces landslides. Researching the law of rainfall infiltration in slope is of crucial significance for the prediction and prevention of landslides. The traditional Green-Ampt model and the improved Green-Ampt model both assume that the infiltration process is uniform and saturated, ignoring the existence of unsaturated zone above the wetting front. In view of this, we analyzed the distribution law of matric suction in slope first of all based on Darcy’s law; and in subsequence, we obtained the functional relation of water content in the wet zone of slope varying with depth in association with the VG model of unsaturated soil; finally, we derived a rainfall infiltration model considering the unsaturated characteristics of soil using the improved Green-Ampt model, and applied the model into infinite slope stability analysis. Results demonstrated that, compared with numerical solution and existing models, the proposed infiltration model in consideration of the unsaturated characteristics of soil reflects more accurately the process of rainfall infiltration. In addition, the stability coefficient calculated based on the proposed model better reveals the change rule of slope stability under constant rainfall intensity, which proves the correctness and applicability of the model.

膨胀土非饱和渗流的过程伴随着膨胀应变的产生。探明多场耦合作用下膨胀应变对膨胀土边坡非饱和降雨入渗的变化规律至关重要。基于有限差分渗流理论、降雨入渗模块的二次开发和膨胀应变的施加,采用C++和FISH语言编制程序,将膨胀应变引入非饱和土的流-固耦合模型,提出了一种综合考虑膨胀应变和应力应变的非饱和膨胀土多场耦合分析法,通过算例实现了降雨入渗条件下膨胀土边坡非饱和渗流的数值模拟,并探讨了膨胀应变对饱和度和暂态面积比的影响规律。研究表明,膨胀应变对膨胀土边坡非饱和降雨入渗的过程影响显著,其降雨入渗深度、湿润锋扩展速度和暂态饱和区时空分布受膨胀应变的控制,考虑膨胀应变时暂态面积比变化的雨后时间滞后性强于不考虑膨胀应变时。

The process of unsaturated seepage in expansive soils is accompanied by the generation of expansion strains. The expansion strains under the coupling of multiple fields are crucial for investigating the variation of unsaturated rainfall infiltration in expansive soil slopes. By applying C++ and FISH language to programming, we introduced expansion strain into the fluid-structure interaction model of unsaturated soils, and proposed a multi-field coupling analysis method for unsaturated expansive soil considering expansion strain and stress strain. By using this model, we simulated numerically the unsaturated seepage flow of expansive soil slope in the presence of rainfall infiltration, and furthermore explored the influences of expansion strain on saturation degree and transient area ratio. Research results suggest that expansion strain has an evident impact on the process of unsaturated rainfall infiltration in expansive soil slopes. The depth of rainfall infiltration, the expansion speed of wetting front, and the temporal and spatial distribution of transient saturation region are controlled by the expansion strain. After rainfall, the time lag of transient area ratio is extended when expansion strain is considered.

结合拉普拉斯变换和有限差分法给出求解试井分析中-维渗流问题的拉普拉斯变换差分法:首先对渗流方程采用拉普拉斯变换消去时间变量得到拉普拉斯空间数学模型,采用有限差分法求解拉普拉斯空间数学模型,最后通过拉普拉斯反演算法得到井底压力或产量.通过与有限差分法结果和解析解对比,拉普拉斯变换差分法比有限差分法计算误差小.虽然单步计算耗时长,但计算任意时刻结果时对空间网格的适应性和不依赖其它时刻计算结果的特性使得拉普拉斯变换差分法在试井分析中有非常好的应用前景.

With finite difference method and Laplace transform,a Laplace transform difference method for well-test problem with one-dimensional seepage flow is proposed.Firstly,time variable is eliminated by Laplace transform.Then the mathematics model is solved with finite difference method.Finally the wellbore pressure or production is obtained with numerical inversion algorithm.A comparison with finite difference method solution and analytic solution shows that the calculating error of Laplace transform difference method is smaller than that of finite difference method,though it consumes more time in each step.Laplace transform difference method has advantages in well-test application since any moment simulation does not rely on other moment result and space grid.

受限于河渠水位变化过程复杂且无具体函数形式，无法求解建立的该类边界条件控制下半无限域潜水非稳定运动模型，采用不考虑边界条件形式的Laplace变换求解，利用Laplace变换中的微分定理和卷积定理，给出模型的理论解；同时对河渠水位变化过程进行Lagrange插值，给出模型解在实际问题中的运用，并与数值解进行对比。结果表明，该方法简单可行，且给出的模型解析式也均为常规函数，同时结合插值函数，利用相应的求参方法，借助实例进行验算，结果基本吻合，可为河渠附近潜水非稳定流模型解的研究问题提供相关参考。