砂雨法饱和模型制样相对密度控制要素与评价方法

为满足动力离心液化试验相对密度（D_r）低的制样需求，实现砂雨法饱和模型制样相对密度的准确控制，建立了设备制模稳定性评价方法，通过自主研制一套适于饱和模型制样的鸭嘴式砂雨法装置，开展了三组干砂/饱和砂模型对比试验；通过分析出砂口尺寸、落距、移动速度等控制要素的影响，对新型装置制样性能进行了验证；采用微型动力触探仪测试饱和模型不同位置及深度的D_r空间分布，给出了模型均匀稳定性评价方法；建立描述砂雨法制样过程流速变化的数学模型和推导表达式，提出了控制稳态D_r的归一化标准. 研究结果表明:3 mm为低密实度制样的最佳出砂口尺寸；饱和模型D_r随水中落距的变化率为空中落距变化率的3.5倍，水中落距是饱和制样密实度的主导控制要素；出砂口移动速度最高达到颗粒落速的31%，对低密实度制样影响不可忽略；设备移速与落距对颗粒流速及试样D_r大小具有决定作用. 

Control Factors and Assessment Technique of Relative Density Using Pluviation Method for Saturated Model

Accurate control of relative density (D_r) in saturated pluviation method is the fundamental requirement for low relative density sample preparation of dynamic centrifuge liquefaction tests. To achieve an evaluation method on pluviation stability, a set of duckbill pluviator which fits saturated modeling was developed. Three groups of dry and saturated sand model contrast tests were carried out to identify the impacts of nozzle size, drop distance and movement velocity, aiming to assess the capability of the developed sampling device. A mini dynamic penetrometer facility was applied to measure the spatial distribution of the saturated model’s D_r, giving a homogeneity evaluation of the models. A particle-flow-velocity model for pluviation was derived to give a normalize criteria for density stable control. The results show that the optimal size of nozzle is 3mm which satisfies the requirements of low compactness modeling. The change rate of D_r with thickness of water is 3.5 times of that with air drop height, indicating that thickness of water layer is the dominant factor on D_r of saturated model. The nozzle movement velocity is up to 31% of particle velocity which is non-trivial on the low density sample preparation. The travelling speed and drop height play a decisive role in particle flow velocity and D_r.