形状效应下砂土管涌试验及水力条件分析

Sand piping tests and hydraulic condition analysis with particle shape effect

管涌是导致水利工程失稳破坏的主要原因之一。目前对土体管涌的研究大多忽视颗粒的形状效应,且部分实际工程的渗透变形结果与理论判别准则不符。为此,采用自主设计的土体渗透试验装置,对3种不同形状的砂土开展了多种颗粒级配的土体管涌试验,基于分形理论和毛管模型多尺度分析了土体发生管涌的临界水力条件,借助声发射系统对试验过程进行了监测。研究结果表明:形状趋于球形砂样的渗透性较强,易发生管涌破坏;随着阻塞颗粒含量的增加,土体在渗流作用下趋于稳定;土体发生管涌的临界水力梯度与质量分形维数呈反比关系;考虑颗粒形状和有效孔隙体积建立的毛管模型,可以较为准确地预测管涌发生的临界流速;声发射累积能量的演化规律可以反映土体管涌的发展特征。

Soil piping is one of the main causes of instability and failure in hydraulic engineering.To date,most of the existing studies on soil piping ignored the shape effect of sand particles;The seepage deformation results of some real projects are inconsistent with the theoretical criterion.In this work,a self-designed soil permeability test device is used to conduct piping tests on a variety of soils that have different gradings and three different particle shapes.Based on the fractal theory and a capillary model,critical hydraulic conditions for soil piping are analyzed at multiple scales,and the testing process is monitored using an acoustic emission system.The results show that sand samples with spherical particle shape have relatively high permeability,prone to piping failure;with the increase of blocking particles,the soil tends to be stable under the action of seepage.The critical hydraulic gradient of soil piping is inversely proportional to the mass fractal dimension;the capillary model based on particle shape and effective pore volume predicts the critical flow rate of piping with a satisfactory accuracy.The evolution patterns of acoustic emission cumulative energy can reflect the characteristics of soil piping development.