灌溉后的黄土剪切特征变化

Variation of Shearing Characteristics of Loess Soil after Irrigation

摘要:

在中国甘肃省的黑方台阶地上从上世纪60年代开始出现人类定居和开垦活动,并自1968年发展为灌溉农业.随着灌溉的进行地面已出现沉陷和滑坡.地表沉陷是由灌溉水的充填引起黄土结构崩塌造成的.然而崩塌和湿润化对剪切特征的影响目前还不清楚.为了研究湿化后的黄土剪切特征的变化,进行了对马兰黄土未经扰动和重塑土样的直接剪切盒测试.结果显示未扰动土样的粘合力和内摩擦角在湿润化后都下降了,而所观察到的重塑土的弹度参数只有少许变化.未扰动土的不饱合粘合力,据认为其受胶结物质的影响,在饱合后消失了.经灌溉的土的不饱合强度参数与未灌溉土相比表现出差异,它们可能受土壤水分的强烈影响.

Abstract:

At Heifangtai terrace in China, farmland reclamation and settlement started in 1960＇s and irrigation farming began in 1968. Following to the irrigation, ground subsidence and landslides have occurred. The ground subsidence was due to collapse of loess soil caused by applying irrigation water. However, the effect of the collapse and the wetting on shear characteristics are still not clear. In order to investigate changes in the shear characteristics of loess soil when wetted, direct shear box test using the undisturbed and remolded samples of Malan loess soil was conducted. The results of the undisturbed soil showed decrease in both cohesion and internal friction angle occurred by wetting, while little change in the strength parameters was observed for the remolded soil. For the undisturbed soil, the cementating material is considered effective to the unsaturated cohesion, which disappears in the saturated state. The irrigated soil showed the different unsaturated strength parameters from the non-irrigated soil. Nevertheless, the may be strongly affected by the soil water content.