改良花岗岩残积土进失水能力及接触角试验研究

花岗岩残积土的进失水能力与其软化崩解的特殊力学特性息息相关，现有的改良土研究都着重于土体宏观力学与微观结构的变化，忽视了固化剂对土颗粒表面性质的影响。为了探索固化剂改良后的花岗岩残积土进失水能力及三相接触角的变化规律，开展了水滴入渗试验、接触角测量试验、进水试验和失水试验，并结合扫描电镜和红外光谱方法，定性及定量分析了花岗岩残积土在不同固化剂作用下微观结构和化学成分的变化规律对花岗岩残积土进失水能力的影响机制。结果表明：（1）不同含量的改良剂能不同程度地影响花岗岩残积土表层斥水性能；随着固化剂掺量的提高，土体的表面斥水性增强，三相接触角变大，进失水能力减弱；固化剂改良土体的效果依次为石灰、水泥、高岭土，且改良土体的进失水能力变化与土体表面斥水性和三相接触角的变化有明显的相关性。（2）改良花岗岩残积土进失水能力的变化由土体内部结构的改变以及表面性质的改变共同导致。（3）水泥和石灰主要依靠离子的交换团聚作用、土壤固化剂对土颗粒的包裹作用、硬凝反应以及碳酸化作用减弱土颗粒外部的双电层及其表面自由能，使土体斥水性和初始接触角变大；而高岭土主要依靠自身对水分子的吸附作用，对土体的斥水性和接触角影响不大。结果可为固化剂改变土体表面性质导致的接触角变化规律提供一定科学依据，也为不同渗透需求的实际工程选取改良剂提供一定参考。

Water entrance-and-release capacity and contact angle of improved granite residual soil

Water entrance-and-release capacity of granite residual soil is closely related to the special mechanical properties of softening and disintegration. Existing research on the improved soil focuses on the macro-mechanical properites and variation of micro-structure of soil, and ignores the influence of curing agent on the soil surface properties. To explore the water entrance-and-release capacity of granite residual soil improved by curing agent and the variation of three-phase antenna, the water drop infiltration test, contact angle measurement test, water inlet test and water entrance-and-release test were carried out. Combined with scanning electron microscopy and infrared spectroscopy, the influence mechanism of microstructure and chemical composition of granite residual soil under different curing agents on entrance-and-release of granite residual soil was analyzed qualitatively and quantitatively. The results show that (1) different contents of curing agent can affect the surface water repellency of granite residual soil to different degrees. With the increasing curing agent content, the surface water repellency of soil increases, the three-phase antenna becomes larger, and the water release capacity weakens. (2) The improvement effect of lime is stronger than that of cement and kaolin, and the change of water entrance-and-release capacity of modified soil is obviously correlated to the change of water repulsion and three-phase antenna. The change of water entrance-and-release capacity of improved granite residual soil is caused by the changes of soil internal structure and surface property. (3) Cement and lime mainly rely on ion exchange agglomeration, soil curing agent's wrapping effect on soil particles, hard coagulation reaction and carbonation to weaken the double electric layer and surface free energy on the surface of soil particles, so that the soil water repulsion and initial contact angle become larger. Kaolin mainly depends on its adsorption of water molecules, but it has little effect on the water repellency and contact angle of soil. The results can provide a scientific basis for the variation of contact angle caused by the change of soil surface properties by curing agent, and also provide a reference for the selection of improvement in practical engineering with different permeability requirements.