路基煤矸石填料土-水特征曲线试验研究

Experimental study on soil-water characteristic curves of subgrade coal gangue filler

煤矸石作为煤层开采和洗选过程中产生的废弃料,常用于路基填筑。压实的路基煤矸石填料存在双孔隙群结构,其土-水特征曲线(SWCC)具有双台阶现象。而SWCC与土体非饱和渗透系数密切相关,对路基内部水分运移以及路基长期累积变形有重要影响。为了探究压实度、粉粒含量、最大颗粒粒径对双台阶SWCC的影响,对路基煤矸石填料进行了一系列压力板试验,并采用描述双台阶SWCC的Bi-V-G公式拟合实测SWCC,分析了模型参数变化规律。试验结果表明,粉粒含量为5%时,不同压实度试样SWCC均存在双台阶现象;粉粒含量为50%时,随着压实度增大,试样SWCC由双台阶形过渡为单台阶形,在0.90和0.95压实度之间存在一个界限值,双台阶现象消失;增大压实度、提高粉粒含量或减小最大颗粒粒径,均会使SWCC台阶高差减小。随着压实度增大或粉粒含量提高,模型参数a1、a2(与进气值有关的参数)和n1、n2(与排水程度有关的参数)值均逐渐减小,试样大、小孔隙部分均进气值增大,持水能力提高。

As a waste material generated during coal mining and washing,coal gangue is often used for filling roadbeds.The compacted coal gangue has a dual-porosity structure,which usually leads to bimodal soil-water characteristic curves(SWCC).SWCC is closely related to the permeability coefficient of unsaturated soils,which has an important influence on the water migration inside the roadbed and the long-term serviceability of the roadbed.In order to investigate the influence of compaction degree,silt content and maximum particle size on bimodal SWCCs,a series of pressure plate tests was conducted on compacted coal gangue samples.The experimental data was fitted by a bimodal SWCC function model,and the variation of fitted parameters was analyzed.The test results show that when the silt content is 5%,samples with different compaction degrees have bimodal SWCCs.When the silt content is 50%,the SWCCs of samples change from bimodal to unimodal with the increase of compaction degree,so it can be inferred that there exists a critical value of compactness between 0.90 and 0.95.Increasing compaction degree or silt content,or decreasing maximum particle size will reduce the difference of step height in SWCCs.With the increase of compaction degree or silt content,the values of model parameters a1,a2(parameters related to the air-entry value)and n1,n2(parameters related to drainage degree)decrease gradually,that is,the air-entry values and the water holding capacity of both macro-pore part and micro-pore part increase.