CAJ | 학술논문

黄土地区降雨诱发滑坡是不争的事实,但黄土地区地下水位很深,降雨入渗地面后如何运移,与地下水有无直接联系,目前还不是很清楚.为此设计了人工滴水试验模拟天然降雨条件,通过在一深度为10 m的探井井壁上埋设土壤水分计,观测人工滴水入渗过程中不同深度土体含水率随时间的变化情况,以确定其入渗影响深度.监测结果显示:降雨量为3.82 mm/d (小雨)时,0.5 m内土体含水率变化明显,0.5 m以下土层含水率几乎没有变化;降雨量为10.31 mm/d(中雨)时,1 m内土体含水率有所增加;降雨量达25.21 mm/d(大雨)时,1 m内土体含水率增长明显,1.0~1.6 m范围内有微弱增长;随着深度增加,土体含水率变化逐渐滞后,增幅逐渐减小.这说明在干旱的黄土地区,若无明显入水通道,短期内降雨的入渗深度有限,很难到达地下水位;但深部古土壤层的观测结果表明,即使在其上部黄土中含水率变化极其微弱的情况下,古土壤中的含水率上升明显,表明黄土中非饱和渗流或水汽迁移是存在的.通过试验还表明,陇东黄土高原地区土壤中水分循环主要发生在浅层0.7 m以内的蒸发带.降雨入渗到蒸发带以内,若无后续降雨补给,则向上蒸发排泄;若入渗至蒸发带以下,则不受蒸发影响,得以继续向下迁移;当遇到不透水面时,会在层面附近富集,有限元模拟也较好地反映了这一规律.
황토지구강우유발활파시불쟁적사실,단황토지구지하수위흔심,강우입삼지면후여하운이,여지하수유무직접련계,목전환불시흔청초.위차설계료인공적수시험모의천연강우조건,통과재일심도위10 m적탐정정벽상매설토양수분계,관측인공적수입삼과정중불동심도토체함수솔수시간적변화정황,이학정기입삼영향심도.감측결과현시:강우량위3.82 mm/d (소우)시,0.5 m내토체함수솔변화명현,0.5 m이하토층함수솔궤호몰유변화;강우량위10.31 mm/d(중우)시,1 m내토체함수솔유소증가;강우량체25.21 mm/d(대우)시,1 m내토체함수솔증장명현,1.0~1.6 m범위내유미약증장;수착심도증가,토체함수솔변화축점체후,증폭축점감소.저설명재간한적황토지구,약무명현입수통도,단기내강우적입삼심도유한,흔난도체지하수위;단심부고토양층적관측결과표명,즉사재기상부황토중함수솔변화겁기미약적정황하,고토양중적함수솔상승명현,표명황토중비포화삼류혹수기천이시존재적.통과시험환표명,롱동황토고원지구토양중수분순배주요발생재천층0.7 m이내적증발대.강우입삼도증발대이내,약무후속강우보급,칙향상증발배설;약입삼지증발대이하,칙불수증발영향,득이계속향하천이;당우도불투수면시,회재층면부근부집,유한원모의야교호지반영료저일규률.
@@@@It is an indisputable fact that rainfall can induce landslides in loess area;however, groundwater levels are always very deep in loess area. At present, it is not clear that how does rainfall move in loess and whether it affects groundwater directly when infiltrating ground below. In order to simulate the natural rainfall condition, manual drip experiment is carried out. By using soil moisture meters which are inserted into the wall at a 10 m-deep exploratory well, the changes of moisture content with time of soil layers at different depths in the process of artificial rainfall infiltration could be easily observed;the range affected by rainfall could be confirmed later. The result shows that moisture content of soil layers within 0.5 m changed obviously when the precipitation is 3.82 mm/d (light rain), while that of below have almost no changes;the moisture content within 1 m increases when the precipitation is 10.31 mm/d (moderate rain);the moisture content of the layers within 1 m increases significantly, and that of between 1 m to 1.6 m have a slight rise when the precipitation reached 25.21 mm/d (heavy rain), the changes of moisture content lag and the growth decreases gradually with depth. It is shown that if there are no obvious water paths in arid loess region, the infiltration depth of short-term rainfall is limited and it is difficult to reach the groundwater level, but according to the results of paleosol in deeper, the moisture content of paleosol has a considerable increase even though that of upper loess is relatively weak, which indicates that unsaturated seepage or vapor migration do exist in loess. It is also found that the circulation of soil moisture is primarily occurred in evaporation zone;that within shallow 0.7 m in Longdong Loess Plateau, if there is no recharge from follow-up rainfall, the rainfall infiltrated within evaporation zone will be excreted upward by evaporation;however, it will continue to move downward without the influence of evaporation when infiltrating beyond the evaporation zone; the water will gather on the surface as encountering the impervious layer, which is also reflected preferably by finite element simulation.