土的自重应力新探

New research on gravity stresses in soils

土的自重应力分布是土力学的基本理论之一,对于地下水位以下饱和粘性土中的自重应力分布目前学术界尚无定论。本文分别从浮力原理和有效应力原理出发,探讨了渗流作用下土的自重应力分布问题,揭示了地下水竖向渗流对土的自重应力分布的影响作用,解决了地下水位以下饱和粘性土中的自重应力分布问题。本文研究成果显示,在多层含水层系统中,由于地下水水头分布的不同,地下水在地下水位以下饱和粘性土中可能产生负浮力、零浮力、欠浮力、静水浮力或超浮力,土的自重应力分布与传统方法计算结果有很大的差别。正是由于地下水竖直方向的渗流影响,造成了长期以来对土的自重应力的低估或高估,以及对土的应力历史的误判。因此对土力学以及岩土工程中的许多问题比如土压力问题、地下水的浮力等问题,需要重新审视。

Gravity stress distribution in soil is one of the basic theories in soil mechanics. No final conclusion has yet been reached on the gravity stress distribution in saturated clayey soil under the groundwater level. Based on the buoyancy principle and effective stress principle respectively, the vertical groundwater seepage effects on the gravity stress distribution in soil are revealed, and the problems are finally resolved. As the results, in the stratum system with multiple groundwaters, the negative buoyancy, zero buoyancy, less buoyancy, static water buoyancy or super buoyancy may occur in the saturated clayey soil under the groundwater level, caused by the different hydraulic head distribution in the soil. There is the great difference between the calculation results from this paper and that from the traditional methods. It is the groundwater seepage action in vertical direction that causes the underestimate or overestimate on the gravity stresses in soil and the wrong conclusion on soil stress history for a long time. So many issues in soil mechanics and geotechnieal engineering such as soil pressure and groundwater buoyancy action should be re-examined.