含非饱和导排层的毛细阻滞型覆盖层性能 模型试验研究

通过自制试验装置研究了强降雨条件下含非饱和导排层的毛细阻滞型覆盖层性能，试验装置包括 2 m×1 m×1.2 m 的模型槽、降雨模拟器与测量系统等。毛细阻滞型覆盖层模型中细粒土、非饱和导排层和粗粒土分别采用粉土、砂和碎石，模型坡度为 1<>V ∶ 3<>H ，共进行 3 组试验。所模拟的强降雨强度为 65 ～ 76 mm/h ，利用摄像和张力计监测了降雨入渗及侧向导排过程，并分别监测了坡面径流量、各土层的侧向导排量及底部渗漏量随时间变化。在强降雨条件下，试验 Ⅰ 中坡面径流量占降雨量的 69.4% ，入渗的水量中大部分存储在上层粉土中，砂层的侧向导排量为降雨量的 3.5% ，碎石层底部的渗漏量只有降雨量的 2.9% 。试验 Ⅱ 和试验 Ⅲ 中通过添加膨润土降低粉土层渗透性有效减少了降雨入渗量，与试验 Ⅰ 相比，试验 Ⅱ 和试验 Ⅲ 中非饱和砂层侧向排水出现时间延后，试验 Ⅱ 中通过下卧碎石层渗漏量进一步减少至 0.8% ，试验 Ⅲ 中无渗漏。试验结果表明：通过控制上层土 降雨 入渗量及发挥毛细阻滞及侧向导排综合作用，可有效控制该覆盖层在强降雨条件下渗漏量，使毛细阻滞型覆盖层在湿润气候区应用成为可能。

Model tests on capillary-barrier cover with unsaturated drainage layer

Model tests are carried out to study the response of capillary-barrier cover with unsaturated drainage layer under heavy rainfall situation.The test equipment includes a model box with a dimension of 2 m×1 m×1.2 m,a rainfall simulator and measuring facilities.The materials of fine layer,unsaturated drainage layer and coarse layer of the capillary-barrier cover model are silt,sand and gravel respectively,and the gradient of model is 1V: 3H.The intensity of simulated rainfall is 65~76 mm/h.During the tests the rainfall infiltration process and lateral drainage phenomenon are observed,and the surface runoff,lateral drainage and percolation through capillary-barrier cover are measured.In Test Ⅰ,runoff accounts for 69.4% of the total rainfall,and most of the infiltration is stored in the silt layer.The lateral drainage of the sand layer is significant,being 3.5% of the total rainfall;and the percolation through the cover is 2.9% of the total rainfall.In Tests Ⅱ and Ⅲ,the infiltration flux is reduced by an addition of bentonite into the silt layer.A delayed response in the lateral drainage is observed in the sand layer,and the percolation is reduced to only 0.8% of the total rainfall in Test Ⅱand no percolation is observed in Test Ⅲ.The model test results indicate that the percolation through the capillary-barrier cover can be controlled under heavy rainfall condition by reducing rainfall infiltration and enhancing capillary barrier effect and lateral drainage capacity.The research makes the application of capillary-barrier cover in humid regions feasible.