泥石流宽级配砾石土中最优细粒质量分数试验研究

An experimental study on optimum content of fine grains of wide-graded gravel soil

宽级配砾石土的最优细颗粒质量分数可最大限度地降低其渗透性,抑制拦砂坝底扬压力,保障工程安全.通过击实试验和理论分析,研究了宽级配砾石土中细颗粒质量分数对土体干密度(孔隙度)的影响,确定了泥石流堆积物中最优细颗粒质量分数.研究表明,土体干密度与细颗粒质量分数的关系呈抛物线型,抛物线顶点即为最优细粒质量分数.理论分析表明,细粒质量分数在15.5%~20.6%时,粗颗粒孔隙被细粒填满;土体最优细粒质量分数理论值为20.6%,粗、细颗粒均处于最紧密堆积,干密度最大,孔隙度最小.理论计算未考虑粗颗粒的级配和颗粒本身的不规则性,计算结果较实际值偏大.击实试验表明,泥石流宽级配砾石土的最优细颗粒质量分数在15.68%~16.92%之间;土体干密度趋于最大,孔隙度达到最小.因此,为有效降低泥石流拦砂坝基底扬压力,建议坝基砾石土中细颗粒质量分数保持在16%~20%.

The optimum content of fine grains of wide-graded gravel soil can result in the lowest permeability,which will minimize the uplift pressure acting on the base of debris dam and increase engineering safety.The research of the influence of fine grain content on dry density of wide-graded gravel soil has been conducted based on the compaction tests and theoretical analysis.The optimal fine grain content of debris flow deposit has been determined. Research shows the relationship of fine grain content and dry density of soil is parabolic, and the parabolic vertex is the optimal fine grain content.Based on calculation and analysis, it has been found that the pores of coarse grains are filled by fine grains when the content of fine grains reach 15.5%-20.6%.And the theoretical value of the optimum content of fine grains is 20.6% ,which means the coarse and fine grains are in the most compact condition with maximum dry density and minimal porosity.The result of theoretical calculation, because of ignoring the gradation of coarse grains and irregularity of its shape, is larger than the actual value. Results of compaction tests show that the optimum contents of fine grains of wide grading gravelly soils are 15.68%--16.92% ; the dry density of the soil tends to be the biggest and the porosity be the smallest when the content of fine grains approaches to optimum content. Therefore, aim to reduce uplift pressure, the fine grain content of wide-graded gravel soil can be used for foundation of debris dam should be 16%--20%.