接触角对非饱和土中基质吸力的影响

Effect of contact angle on matric suction of unsaturated soil

接触角是研究三相界面的一个基本物理量。非饱和土是典型的三相体,然而在非饱和土力学中对接触角的研究还比较少,目前还停留在假设阶段,通常假设接触角为某一固定值,甚至忽略接触角的影响。实际上接触角是随外界环境的改变而变化的。通过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。试验结果表明,接触角对非饱和土中的基质吸力有重要影响,含水率相同时,随着接触角的增大基质吸力是不断减小的,当含水率增大到一定值时,基质吸力不受土体(亲水状态下)接触角的影响。当接触角增大到一定值时,非饱和土体中的基质吸力消失,即非饱和土体中不再存在负的孔隙水压力。

Contact angle is a basic physical variable of the three-phase interface. Unsaturated soil is a typical three-phase matter. The research on contact angle in unsaturated soil is at the beginning stage. In general, contact angle is supposed as a constant or overlooked. Actually the contact angle will change with the external environment. The contact angle of sand will increase with surface modification. The surface property of sand is a＞ered from hydrophilic to hydrophobic. The apparent contact angle of sand increases by mixing the hydrophobic sand into normal sand. The mixture is used for preparation of samples. The suction measurement tests on samples with different contact angles are conducted. The resu＞s indicate that the contact angle has important effect on matric suction in unsaturated soil. When the water content at the same value, the matric suction decreases with the increasing of contact angle. When the water content reaches a certain value, matric suction would not be affected by the contact angle of sand（under hydrophilic condition）. When the contact angle reaches a threshold value, the matric suction disappears. The negative pore water pressure does not exist in unsaturated soil.