南阳膨胀土裂隙扩展及室内降雨人渗实验研究

Experimental Research on Crack Extension and Indoor Rainfall Infiltration of Nanyang Expansive Soil

膨胀土在含水量降低时发生干缩开裂,给工程带来了极大的危害,其中降雨条件下裂隙膨胀土渗流问题是一个典型的膨胀土工程问题。制备6个相同的南阳重塑膨胀土样,在相同的环境下分别脱湿96,79,63,48,39,30 h,通过数码拍照得到不同时刻试样表面裂隙图片,通过分析得到试样表面裂隙率;为了衡量裂隙在深部方向的发育情况,使用煤油进行渗透实验,得到煤油入渗系数与脱湿时间、平均含水率、表面裂隙率的关系曲线;在油渗实验结束后进行室内模拟降雨入渗实验,得到裂隙膨胀土入渗率的变化规律。通过对实验数据整理分析发现试样脱湿时间、试样平均含水率、试样表面裂隙率、煤油入渗系数、降雨入渗实验径流开始时间、试样入渗率之间有良好的相互关系,降雨入渗实验初期入渗率较大,入渗率随时间衰减很快,在15 min内降低了两个数量级,脱湿时间越长的样初期入渗率越高,衰减的也越快;入渗率在较短的时间内就开始趋于稳定,稳定后的入渗率随试样表面裂隙率线性增长,增长到一个峰值后迅速降低。

The crack of expansive soil occurs when the moisture content reduces,which brings great harm to the project. Fissured expansive soil seepage under rainfall is a typical engineering problem. In this paper,6 identical remolded Nanyang expansive soil samples were prepared,which were dried for 96,79,63,48,39 and 30 h in the same environment,respectively. Surface crack images at different times were obtained with digital camera,and surface fracture rate was obtained through images analysis. To measure crack development in the deep direction,the kerosene is used for infiltration experiments,and get the curves of oil seepage coefficient and desorption time,average moisture content,surface crack rate were secured through experiments;the law of fissured expansive soil permeability coefficient variation was got by the indoor simulated rainfall experiments. Through analysis of the experimental data,we find out that there exist good relationship among sample desorption time,surface cracks rate,average moisture content,oil seepage coefficient,the starting time of rainfall runoff and infiltration rate. In the initial infiltration,infiltration rate decay with time soon,reduces two orders of magnitude within 15 min;the initial infiltration rate of longer dewetting samples was higher and was with faster decay;infiltration rate stabilizes in a short time;the stabilized infiltration rate increases linearly with the surface crack rate to a peak and then decreases rapidly.