增压式真空预压加固吹填超软土微观结构特征分析

Analysis of microstructure characteristics of air-booster vacuum preloading for ultra-soft dredger fills

先进行常规真空预压法(CVP)和增压式真空预压法(AVP)两组模型试验,分别对吹填超软土进行加固处理,对比分析其加固效果。再利用电镜扫描试验(SEM)和压汞试验(MIP)分别对两种方式加固后的吹填超软土进行微观结构测试,分析在两种加固方式下吹填超软土微观结构特征的变化,并通过Image-Pro Plus图像处理技术进行定量分析,模型试验结果分析表明增压式真空预压的加固效果优于常规真空预压,从土体骨架颗粒形态、骨架颗粒接触形式和骨架颗粒间孔隙3个角度说明了增压式与常规真空预压加固后土体的微观结构特征变化,微观结构定量分析表明,与常规真空预压相比,增压式真空预压加固后土体的孔隙数量、扁平度K、形状系数ff更大;土体的孔隙率、分形维数D更小;定向概率熵Hm没有明显的变化规律;孔径分布增量的峰值位置在左侧,说明增压式真空预压加固后土体的小孔隙数量更多。从微观角度证明了增压式真空预压法的加固效果优于常规真空预压法。

Two sets of model tests using the conventional vacuum preloading(CVP)method and the air-booster vacuum preloading(AVP)method,were implemented to strengthen the ultra-soft dredger fills and compare their reinforcement effect.The microstructure characteristics of ultra-soft dredger fills after two methods of reinforcement were investigated using scanning electron microscope(SEM)and mercury intrusion porosimetry(MIP),respectively.A comparative analysis was performed with respect to variables microstructure characteristics of ultra-soft dredger fills,and quantitative analysis was conducted by Image-Pro Plus graphics processing technology under the two reinforcement methods.The model test results show that the reinforcement effect of AVP method is better than that of CVP method.The microstructural characteristics of soil reinforced by two methods were analyzed from three aspects:the morphology of soil skeleton particles,the contact form of soil skeleton particles and the pore space between soil skeleton particles.Compared with CVP method,the microstructure quantitative analysis results indicate that the number of pores,flattening degree K and shape coefficient ff of soil are larger,whereas the porosity and fractal dimension D of soil are smaller after reinforcement in AVP method.However,the directional probabilistic entropy Hm has no obvious change rule,and the peak of the aperture distribution increment is on the left,indicating a greater number of small pores by using AVP method.Furthermore,it is proved that the reinforcement effect of the AVP method is superior to that of CVP method from the microscopic aspect.