不同压实度和初始含水率裂隙膨胀土室内降雨入渗试验研究

Experiment Study on Indoor Rainfall Infiltration of the Fractured Expansive Soil with Different Compaction Degrees or Initial Water Contents

在大气降雨和蒸发的作用下,膨胀土体收缩产生大量无序破裂裂隙,水分易向土体深部渗透,裂隙性膨胀土比同类非开裂土体具有更大的渗透性,容易使膨胀土地区的边坡滑坡。常规试验中采用完整的土样进行渗透试验,量测出的渗透系数与实际裂隙存在的膨胀土渗透性有数量级上的差异,为反映裂隙膨胀土的真实渗透性,对不同初始含水率相同压实度、相同初始含水率不同压实度的两组裂隙膨胀土样进行室内模拟降雨实验,研究其在降雨入渗条件下的渗透规律,得出以下结论:(1)不同压实度膨胀土样脱湿后都形成以宽、细裂隙构成的裂隙网络,表面裂隙形态各不相同,总体上随压实度降低土样主裂隙有由开放向连通闭合的趋势,高、低压实度土样表面裂隙率比中等压实度(75%)土样低;(2)不同初始含水率土样裂隙脱湿后表面裂隙形态差异大,初始含水率从高到低土样宽裂隙趋向于均匀,且细裂隙明显增多,主裂隙曲线形状随初始含水率降低由圆弧状向直线转变,高初始含水率土样表面裂隙率大,初始含水率降到一定程度时土样表面裂隙率基本相当;(3)不同压实度下裂隙膨胀土初始入渗率随压实度增大而增大,近于线性关系,其后短时间内急骤衰减,压实度大的土样衰减速率较慢,稳定后入渗率都处于10-4数量级;(4)不同初始含水率土样初始入渗率数量级相同,不同土样入渗率变化区别极大,入渗率衰减阶段的衰减速率与持续时间明显不同,初始含水率高的土样衰减速率较低、持续时间长,土样稳定后平均入渗率除极高初始含水率土样外其他基本相同,约为4×10-4cm/s。

In the role of atmospheric precipitation and evaporation,expansive soil shranked and produced a lot of random crack,water easy penetrated to deep soil,fissured expansive soil similar has larger permeability than non cracked soil,easy to make the landslide happen in the expansive soil area.In the conventional tests,the permeability coefficient of the soil samples was determined by using the full soil samples,and the permeability of the expansive soil was found to be different from the actual.In order to reflect the true permeability of cracked expansive soil,the indoor rainfall infiltration experiments were carried out to two groups of cracked expansive soil samples with different initial water content and different compaction degree,the infiltration laws of rainfall infiltration were studied,and the conclusions as follows:①The soil samples with different compaction degrees are formed with wide and fine cracks after dehydration,the surface fracture morphology are different,there have the trend of main crack from opening up to connected closed with the compaction degree decreases,the surface crack ratio of high and low compaction degree expansive soil were less than medium degree expansive soil(75%);②Different initial water content expansive soils have different surface fracture morphology,the main fracture curves became even and fine cracks were obviously increased with the initial water content from high to low,the shape of the main fracture curves were turned from the arc shape to a straight line,high initial water content samples have more fracture rate,the fracture rate became similar when the initial water cut to a certain extent;③The initial infiltration rate increased when compaction degree of expansive soil increased,there was a nearly linear relationship,the infiltration rate was sharply decreased followed by a short period,and the magnitudes of stable infiltration rate were 10-4;④The initial infiltration rate of different initial water content expansive soils had the same magnitudes,the change of different samples infiltration rates were great different and the decay-rate and duration were significantly different,the high initial water content expansive soils had low decay-rate and during a long time,the stable infiltration rate were basically the same(about 4×10-4 cm/s)except high initial water content expansive soils.