接触角及接触角滞后效应对非饱和土力学性质的影响研究

The contact angle of soil and pore water is changed by using surface-active agent.It confirms the variety and dosage of surface-active agent through testing.The contact angles of soil were measured with the Capillary Rise Method and the Sessile Drop Method.Strength test and penetration test were carried out with different soil samples and the samples have different contact angles,there were two ways in these tests,one is control the matric suction and another is not.Base on theses tests,the effects of contact angle on unsaturated soil strength and vadose characters were studied.The Soil-Water Characteristic Curve(SWCC) models were established, pore distribution and contact angles were reflected in the models.The models include drying boundary curve,wetting boundary curve and hysteresis scanning curve.The receding contact angle and advancing contact angle were measured with Wilhelmy plate method, numerical calculations have been made base on the experimental data. The effects of contact angle hysteresis pinning process on the deformation of unsaturated soil using PFC were studied. The theory basis of unsaturated soil is provided from micro level and surface science.

利用表面活性剂来改变土颗粒与孔隙水间的接触角，通过试验确定表面活性剂的种类和添加量，采用毛细管上升法和固滴着液法对接触角进行测量。对不同接触角的土样进行强度和渗透试验，试验分别包含：控制吸力试验和不控制吸力试验两种，以此来研究接触角对非饱和土强度和渗流特性的影响。建立能综合反映土样孔隙分布特性及微观接触角特性的土水特征曲线模型，模型包括反映增湿、退湿的边界曲线模型及反映土水特征曲线滞后性质的扫描线模型。用Wilhelmy平板法对土颗粒的前进接触角和后退接触角进行测量，以此作为建立模型的试验依据，在数值计算基础上，以PFC软件为基础研究接触角滞后效应Pinning过程对非饱和土变形的影响。从细观和表面科学角度，为进一步认识非饱和土的力学性质提供理论基础。

非饱和土中存在三相：固相、液相和气相。接触角是描述三相物质的一个基本物理量。本项目以非饱和土中的接触角为研究对象，通过改变土颗粒表面的接触角，开展不同接触角下非饱和土力学性质试验。用化学方法对砂土表面改性从而提高砂土的接触角，使砂土由亲水性变为斥水性。在亲水性砂土中加入斥水性砂土以提高砂土的表观接触角，以此为基础制备不同接触角的试样进行吸力测量试验，探讨了土体中的接触角与基质吸力的关系。把退湿分为外力式退湿和蒸发式退湿两种形式；增湿分为外力式增湿和凝结式增湿两种形式，以此为基础分析了退湿过程中，张力计和轴平移技术测量吸力时土样中的接触角特性；建立了理想化的土壤颗粒模型对砂土、粘土的斥水特性进行计算分析，对土体由“亲水”转变为“斥水”的机理有进一步的认识；对纯水、酒精溶液和肥皂水三种液体的表面张力进行测量，比较三种溶液表面张力的大小，在此基础上，把三种液体分别作为孔隙液体进行非饱和膨胀土的收缩开裂试验，为进一步认识土体开裂的本质提供了一个新思路；以理想模型为基础，分析了两球体颗粒相对移动时，接触角滞后效应对液桥力及液桥粘滞力的影响。项目从细观和表面科学角度，为进一步认识非饱和土的力学性质提供理论基础。