固态水膜对土中力链传递的影响机理

The effectmechanisms of solid water layer on the force chains in soils

土骨架所承担的荷载是经由力链传递的.当颗粒直接接触时,力链中的荷载直接由粒间作用力而传播.但对于具有吸附性的岩土材料,则应审慎考虑土水相互作用对土骨架承载机理的影响.通过总结土中吸附水的性质,将具有类固态性质的吸附水定义为固态水,明确了固态水膜所引起的水化力的定义及其作用机理,进而详细分析了土中力链的传递机理:当颗粒被固态水膜所包裹时,力链构型为“颗粒固态水颗粒”形式,此时颗粒并非直接接触,因而力链中的荷载是经由固态水膜所提供的水化力在粒间传递的;若荷载足够大且边界约束严格,则可将粒间固态水膜完全挤出以实现颗粒直接接触,此时力链构型为“颗粒颗粒”形式,力链中的荷载即由实际粒间接触压力来传递.若土的吸附能力较强且含水量较高,虽然整个加载过程中力链会不断变化与重构,且伴随部分粒间吸附水的挤出,但当颗粒接触点在力链重构中分开时,原本被挤出的粒间固态水膜会迅速恢复,进而继续影响力链的后续变形与重构.考虑到固态水膜的润滑作用,显然该作用机理是土体湿摩擦强度始终低于干摩擦强度的原因之一.

The load carried by the soil skeleton is transmitted in soils by force chains.If particles contact each other directly,the load in force chains is transmitted via inter-particle pressure among soil particles.However,for the adsorptive geomaterials,the solid-water interactions should be taken into account when analyzing the bearing mechanisms.In this work,after reviewing the properties of adsorbed water,the part of it which acts as semi-solid is defined as solid water,and then the definition of hydration force due to solid water and its effects on inter-particle force are illustrated.After that,the force chains in soils are analyzed considering the existence of solid water layer:if particles are wrapped by solid water layer,the force chains are in the form of“particle-solid water-particle”,so particles are indirectly contacted and load is transmitted via hydration force;If the load is large enough and the confinement is rigid enough,the inter-particle solid water could be extruded to realize the direct inter-particle contact,so the force chains are in the form of“particle-particle”and the load is transmitted via real inter-particle pressure.If a soil is strong adsorptive with higher saturation degree,although some inter-particle solid water could be extruded in the process of changing and reforming of force chains,it will recover immediately after the contact points are separated,which could affect the reforming of force chains during the whole loading process.Considering the lubrication due to solid water,it is obvious that the existence of solid water layer in force chains is a key reason to make the wet friction strength always lower that the dry friction strength.