改良花岗岩残积土崩解特性试验研究

Experimental Study on Disintegration Characteristics of Improved Granite Residual Soil

在华南地区循环湿热多雨气候的影响下,花岗岩残积土遇水极易崩解,诱发崩岗等地质灾害,对道路、桥梁等工程造成极大影响,因此常利用水泥、石灰和高岭土等固化剂对花岗岩残积土进行改良。为了进一步研究干湿循环条件下改良花岗岩残积土的崩解特性,采用自行设计的干湿循环崩解测试仪,开展华南地区干湿循环环境下改良花岗岩残积土的崩解试验,结合X射线衍射试验以及扫描电镜试验,研究固化剂对花岗岩残积土抗崩解性的改良效果,分析改良花岗岩残积土崩解机理。结果表明:干湿循环条件下,改良花岗岩残积土土样崩解过程可以分为4个阶段,即表层吸水剥落阶段、饱水软化阶段、饱和稳定阶段和完全解体阶段;干湿循环作用显著增大改良土崩解速率,部分试样崩解速率可达到原来的2~3倍,添加固化剂能有效增强花岗岩残积土的抗崩解性,完全崩解时长增加到素土的2~6倍;基于绿化角度,掺入高岭土对花岗岩残积土进行改良较为合适;素土以及改良土崩解过程中,土样黏土矿物(例如高岭石)含量减少,显著降低土样胶结作用,促进土样崩解的发生;花岗岩残积土内部孔隙大小分布不均匀的结构特征,使土样在崩解过程中产生吸力不平衡现象,较小的孔隙先被水填入,压缩土样孔隙内的空气,产生应力集中现象,这是土样崩解发生的内在驱动力。研究结果揭示了花岗岩残积土崩解机制,可为实际工程中对花岗岩残积土进行改良提供一定的参考。

Under the influence of the cyclic humid, hot, and rainy climate in South China, granite residual soil is easily disintegrated when it comes in contact with water. This induces geological disasters such as collapse and has a significant impact on roads, bridges, and other projects. Therefore, cement, lime, and kaolin are often used to improve the anti-disintegration property of residual soil. A self-designed dry-wet cycle disintegration tester was used to study the disintegration characteristics of improved granite residual soil in South China under dry-wet cycle conditions. The results show that the disintegration process of improved granite residual soil samples can be divided into four stages under dry-wet cycles: surface water absorption and spalling, saturating and softening, saturated stabilization, and complete disintegration. The dry-wet cycle significantly increases the disintegration rate of the improved soil, which can reach 2-3 times in some cases. The addition of curing agent can effectively enhance the anti-disintegration property of granite residual soil, and their total disintegration time increases to 2-6 times that of plain soil. From the perspective of greening, kaolinite is suitable for improving granite residual soil. The content of clay minerals(such as kaolinite) decreased during the disintegration of all the granite residual soil samples, which significantly reduced the cementation and enhanced the disintegration of the samples. The uneven distribution of pore size in the granite residual soil causes the unbalanced suction of the sample during disintegration. The smaller pores are first filled with water to compress the air in the pores of the sample, resulting in a stress concentration phenomenon, which is the internal driving force of disintegration. The results reveal the disintegration mechanism of granite residual soil and provide a reference for the improvement of granite residual soil in practical engineering.